US 4,125,894 AGrant

Engine Test and Display Apparatus

Issue Date:1978-11-14

•128 Claims

•74 Drawing Sheets

Abstract

The disclosure describes an improved automated engine diagnosing device employing a digital data processor computer and a cathode ray tube display monitor which displays engine parameter (i.e., condition) values in alphabetic, numeric, and graphical form. Some data is accumulated from the engine by means of direct digital measurements, whereas other data is obtained from the engine by an analog-to-digital converter. The data is then processed by the computer and displayed on the cathode ray tube display monitor.

Metadata

Assignee

Sun Electric Corporation

Inventors

Aloysius T. Cashel
Frank Perna
Gerald C. Trussell
Alfred C. D'Souza
Richard A. Karlin
James R. Caruth
Gary L. Van Ermen
Robert W. Arnston
Gary F. Comiskey
Frederick R. Borgens
Keith A. Kreft
Arthur Damm
Dennis C. Sienaski
Robert C. Shepardson
Yam C. Leung
Thomas M. Jankowski

Application Information

Application Number:US 7981813

Filing Date:1977-05-18

Priority Date:1975-12-16

Art Unit:236

Classifications

IPC:

G06F 1550F02P 504

Field of Search:

36473123340324424;425;442;551112;116;117.2;117.3;11832 EA146.215;16 R;16 S

Patent Drawings (74 sheets)

Description

BACKGROUND AND SUMMARY OF THE INVENTION

The servicing of vehicle engines is becoming increasingly important because of road safety considerations and the public awareness of automotive emissions on the environment. In addition, the engines of current vehicles are becoming more difficult and complicated to diagnose and analyze. As a result, one object of the present invention is to provide an automated and rapid diagnostic device which will reduce the cost of labor involved in diagnosing vehicle engines.

Other objects of the invention are:

(1) TO PROVIDE PRECISE AND OBJECTIVE EVALUATION OF MALFUNCTION TO AVOID CUSTOMER RETURNS;

(2) TO DISPLAY DATA ACCUMULATED FROM A VEHICLE ENGINE IN AN EASY-TO-UNDERSTAND FORM;

(3) TO PROVIDE AN IMPROVED DEVICE FOR DISPLAYING ENGINE RPM, DWELL AND CYLINDER TIMING BY DIRECT DIGITAL MEASUREMENT;

(4) TO PROVIDE A DEVICE FOR DISPLAYING THE VALUES OF ENGINE PARAMETERS ON A CATHODE RAY TUBE DISPLAY MORITOR IN ALPHABETIC, DIGITAL AND GRAPHICAL FORM;

(5) TO PROVIDE A CATHODE RAY TUBE DISPLAY MONITOR OF THE FOREGOING TYPE IN WHICH THE HISTORY OF AN ENGINE PARAMETER IS DISPLAYED AS A FUNCTION OF TIME;

(6) TO PROVIDE AN IMPROVED DEVICE IN WHICH RELATED VEHICLE ENGINE TESTS ARE GROUPED TOGETHER AND DISPLAYED SIMULTANEOUSLY ON A CATHODE RAY TUBE DISPLAY MONITOR, AND IN WHICH THE TESTS ARE SEQUENCED ONE AFTER ANOTHER IN AN AUTOMATIC MANNER;

(7) TO PROVIDE A SEQUENCING MODE OF OPERATION OF THE FOREGOING TYPE IN WHICH DATA IS REMEMBERED BY THE APPARATUS FROM ONE TEST GROUPING TO ANOTHER;

(8) TO PROVIDE AN IMPROVED DEVICE FOR DISPLAYING ENGINE PARAMETER VALUES FOR EACH CYLINDER OF A MULTICYLINDER ENGINE;

(9) TO PROVIDE A MEANS OF DISPLAYING THE SPEED OF A VEHICLE ENGINE ON A CATHODE RAY TUBE DISPLAY MONITOR BY MEANS OF A BAR GRAPH;

(10) TO PROVIDE AN AUTOMATIC VEHICLE ENGINE DIAGNOSING DEVICE CAPABLE OF REMEMBERING CALIBRATION CONSTANTS AND AUTOMATICALLY PROCESSING THE DATA RECEIVED FROM THE ENGINE BY LINEARIZING THE VALUE OF THE DATA;

(11) TO PROVIDE AN IMPROVED VEHICLE ENGINE DIAGNOSING DEVICE CAPABLE OF DECIDING WHETHER COMPONENTS OF THE ENGINE ARE IN GOOD WORKING ORDER OR SHOULD BE REPLACED;

(12) TO PROVIDE AN IMPROVED DEVICE WHICH IS AUTOMATICALLY CAPABLE OF MEASURING THE POWER BALANCE OF A VEHICLE ENGINE;

(13) TO PROVIDE AN AUTOMATIC POWER BALANCE DEVICE OF THE FOREGOING TYPE IN WHICH THE SPEED OF THE ENGINE OVER SEVERAL ENGINE REVOLUTIONS IS AVERAGED DURING THE POWER BALANCING PROCEDURE;

(14) TO PROVIDE AN IMPROVED APPARATUS FOR MEASURING THE PARAMETERS OF AN ENGINE BY AN ANALOG CIRCUIT WHICH IS AUTOMATICALLY SET TO THE PROPER RANGE DEPENDING ON THE VALUE OF THE PARAMETER BEING MEASURED; AND

(15) TO PROVIDE AN IMPROVED VEHICLE ENGINE TESTING DEVICE WHICH IS CAPABLE OF STORING MAXIMUM AND MINIMUM VALUES OF THE ENGINE PARAMETERS AND OF DISPLAYING THE VALUES STORED.

(16) TO PROVIDE AN IMPROVED VEHICLE TESTING DEVICE CAPABLE OF DISPLAYING A VALUE IF AN ENGINE PARAMETER LIES WITHIN AN ACCEPTABLE RANGE AND CAPABLE OF DISPLAYING A SYMBOL IF THE ENGINE PARAMETER LIES OUTSIDE THE ACCEPTABLE RANGE.

DESCRIPTION OF THE DRAWINGS

These and other objects, advantages and features of the present invention will hereafter appear in connection with the accompanying drawings wherein like numbers refer to like parts throughout and wherein:

FIG. 1 is a perspective view of an internal combusion engine that is connected to a preferred form of the present invention;

FIGS. 2a and 2b are schematic diagrams of an ignition system of the engine shown in FIG. 1 connected to a system block diagram of a preferred form of the present invention;

FIGS. 2c and 2d are timing diagrams showing the manner in which data is transmitted and received by the data processor of the present invention;

FIG. 3 is a schematic diagram of a preferred form of trigger generator made in accordance with the present invention;

FIG. 4 is a schematic diagram of a preferred form of secondary signal sampler made in accordance with the present invention;

FIG. 4a illustrates exemplary voltage waveforms generated by the signal sampler shown in FIG. 4;

FIG. 5 is a schematic diagram of a preferred form of primary-secondary interface circuit made in accordance with the present invention;

FIG. 5a illustrates exemplary voltage waveforms generated by the signal sampler shown in FIG. 5;

FIG. 6 is a schematic diagram of a preferred form of shorting control circuit made in accordance with the invention;

FIG. 7 is a schematic diagram of a preferred form of primary attenuator circuit made in accordance with the present invention;

FIG. 8 is a schematic diagram of an ammeter circuit made in accordance with the present invention;

FIG. 9 is a schematic diagram of a voltmeter circuit made in accordance with the invention;

FIG. 10 is a schematic diagram of an ohmeter circuit made in accordance with the present invention;

FIG. 10a illustrates exemplary voltage waveforms generated by the circuitry shown in FIG. 10;

FIG. 11 is a schematic block diagram of a preferred form of a current source circuit made in accordance with the present invention;

FIG. 11a is a schematic diagram of a condenser leakage tester circuit made in accordance with the present invention;

FIG. 12 illustrates the manner in which FIGS. 12a-12f should be arranged;

FIGS. 12a-12f are schematic diagrams of a preferred form of analog system made in accordance with the present invention;

FIG. 13 illustrates the manner in which FIGS. 13a-13c should be arranged;

FIGS. 13a-13c are schematic diagrams of a preferred form of cylinder selection circuit made in accordance with the present invention;

FIG. 14 illustrates the manner in which FIGS. 14a-14f should be arranged;

FIGS. 14a-14f are schematic diagrams of a preferred form of a counting and cylinder control system made in accordance with the invention;

FIG. 14g illustrates exemplary clock pulses generated by the circuit shown in FIG. 14c;

FIG. 14h illustrates exemplary voltage waveforms produced by the circuits shown in FIGS. 13a-13c and FIGS. 14a-14f;

FIG. 14i illustrates exemplary voltage waveforms used to control the generation of P and N numbers in the counters of circuits 1766-1769;

FIG. 14j illustrates exemplary voltage waveforms used to control the generation of D and E numbers in the counters of circuits 1770-1773 during the accumulative mode of operation;

FIG. 14k illustrates exemplary voltage waveforms used to generate the D and E numbers in the counters of circuits 1770-1773 during the "per cylinder" mode of operation;

FIG. 15 illustrates the manner in which FIGS. 15a-15e should be arranged;

FIGS. 15a-15e are schematic diagrams of a preferred form of a character controller made in accordance with the present invention;

FIG. 16 illustrates the manner in which FIGS. 16a-16c should be arranged;

FIGS. 16a-16c are schematic block diagrams of a preferred form of graphic controller made in accordance with the present invention;

FIG. 16d is a schematic illustration of the manner in which the CRT display shown in FIG. 1 is divided by scanning into rows and columns;

FIG. 16e is an enlarged plan view of a preferred form of a graphical rpm bar as displayed on the CRT;

FIG. 16f is an enlarged view of the right hand end of the rpm bar shown in FIG. 16e;

FIG. 17a is a plan view of a preferred form of front control panel for use in the present invention;

FIG. 17b is a schematic diagram of a preferred form of the keyboard shown in FIG. 17a;

FIGS. 17c-17e are schematic diagrams of a preferred form of front panel interface circuit made in accordance with the invention;

FIG. 18 is a logic schematic diagram of a preferred form of remote control circuitry made in accordance with the invention;

FIG. 19 is a flowchart illustrating the basic executive control sequence executed by the data processor:

FIG. 20 is a flowchart illustrating the analog-to-digital converter data acquisition and display program segment executed by the data processor;

FIG. 21 is a flowchart illustrating the emissions data acquisition and display subroutine executed by the data processor;

FIG. 22 is a flowchart illustrating the manner in which the data processor acquires the P, N and accumulated D numbers and displays the rpm, average dwell and engine timing parameters calculated from the numbers;

FIG. 23 is a flowchart illustrating the manner in which the data processor acquires the E number and the D number in the per cylinder mode and the manner in which the dwell per cylinder, cylinder timing per cylinder and average cylinder timing parameters are displayed based on the acquired numbers;

FIG. 24 is a flowchart illustrating the manner in which the data processor calculates engine timing;

FIG. 25 is a flowchart illustrating the overall operation of the system;

FIG. 26 illustrates the format displayed on the CRT screen during step S140 of the flowchart shown in FIG. 25;

FIG. 27 illustrates the format displayed on the CRT screen during step S141 of the flowchart shown in FIG. 25;

FIG. 28 illustrates the format displayed on the CRT screen during step S142 of the flowchart shown in FIG. 25;

FIG. 29 illustrates the format displayed on the CRT screen during step S143 of the flowchart shown in FIG. 25;

FIG. 30 illustrates the format displayed on the CRT screen during area test 1;

FIG. 31 is a flowchart describing the program segment executed by data processor during area test 1;

FIG. 32 illustrates the format displayed on the CRT screen during area test 2;

FIG. 33 is a flowchart illustrating the program segment executed by the data processor during area test 2;

FIG. 34 illustrates the format displayed on the CRT screen during area test 3;

FIG. 35 is a flowchart illustrating the program segment executed by the data processor during area test 3;

FIG. 36 illustrates the format displayed on the CRT screen during area test 4;

FIG. 37 is a flowchart illustrating the program segment executed by the data processor during area test 4;

FIG. 38 illustrates the format displayed on the CRT screen during area test 5;

FIG. 39 is a flowchart illustrating the program segment executed by the data processor during area test 5;

FIG. 40 illustrates the format displayed on the CRT screen during area test 7;

FIG. 41 is a flowchart illustrating the program segment executed by the data processor during area test 7;

FIG. 42 illustrates the format displayed on the CRT screen after the completion of the area tests;

FIG. 43 illustrates the format displayed on the CRT screen during the pin point ignition test in the per cylinder mode;

FIG. 44 illustrates the format displayed on the CRT screen during the pin point condenser test in the history mode; and

FIG. 45 is a flowchart illustrating the program segment executed by the data processor during the pin point condenser test in the history mode.

DESCRIPTION OF THE PREFERRED EMBODIMENT

INTRODUCTION

Referring to FIGS. 1, 2a and 2b, an exemplary V-8 internal combustion engine 100 can be diagnosed by the present invention. A schematic diagram of the ignition system of engine 100 is shown in FIG. 2a.

Engine 100 comprises cylinders or ignition chambers 101-108 which are fitted with spark plugs or ignitors 101a-108a. The invention also can be used with a Wankel-type engine which uses firing chambers rather than cylinders. Spark plugs 101a-108a are connected to a distributor 110 by spark plug leads 10lL-108L, respectively. Distributor 110 includes a rotor 112 which distributes high voltage ignition signals to each of the spark plugs in a defined sequence. The rotor receives high voltage ignition signals from a coil assembly 114 comprising a primary coil 115 that is magnetically coupled to a secondary coil 116. Voltage signals are generated in the primary coil by a 8-sided cam 117 which is mechanically rotated in synchronism with engine 100 in order to periodically open and close contact points 118, 118a. A conventional distributor capacitor 119 is connected across contact points 118, 118a. The primary coil voltage induces in the secondary coil high voltage ignition or firing signals or pulses which fire the spark plugs sequentially.

Electrical power is supplied to the ignition system by a conventional 12 volt battery 120 having a positive terminal 122 and a negative terminal 123. An ignition switch 124 is connected in series between the battery and primary coil 115, and an alternator 125 charges battery 120.

Although engine 100 is shown with a conventional mechanical contact point ignition system, it should be understood that the present invention can be used to diagnose more sophisticated ignition systems in which electronic or semi-conductor switches are used in place of contacts 118, 118a.

Engine timing marks 130 are fixed to the block of the engine and cooperate with a damper mark 133 on the rotating engine vibration damper 132 in order to properly time the firing of the spark plugs. The engine damper also can include a slot 136, the position of which can be detected by a conventional magnetic pick-up 137 that produces a change in voltage when slot 136 moves past the location of the pick-up. Such devices are well-known in the art and need not be described in detail. Basically, they comprise an electronic circuit typically fabricated on a single or monolithic chip of silicon, and are therefore, commonly referred to as "monolithic" pick-ups.

A preferred form of the present invention which can be used to diagnose an engine of the abovedescribed type basically comprises a cable assembly 150, a case assembly 180, a display monitor 190, including a cathode ray tube (CRT) face 192, a timing light 200, a timing light circuit 202, a monolithic input circuit 210, a trigger generator 215, a secondary signal sampler 264, a primary interface circuit 360, a shorting control circuit 560, a primary attenuator 590, an ammeter circuit 610, a voltmeter circuit 700, an ohmeter-capacitance circuit 750, a current source circuit 830, a condenser leakage test circuit 950, an infra-red emissions analyzer 1000, a data processor 1090, a read-only memory 1094, a processing bus 1096, an analog control system 1100, a counting and cylinder control system 1400, a character controller 1800, a graphic controller 2130, a front panel interface circuit 2240, and a remote controller 2550.

The system can be approximately divided into the functions of (1) data acquisition, (2) acquisition control, (3) display and (4) system processing and management. The function performed by each of the basic system circuits is shown in Table A:

In general, the preferred system made in accordance with the present invention is capable of instructing an operator how to connect and set up the system, capable of conducting area tests in order to locate a general area of malfunction, and capable of conducting pin point tests which isolate a specific difficulty within the general area of malfunction:

The instruction of the operator begins as soon as the system is turned on at the front panel. At that time, the set of written instructions appearing on CRT face 192 informs the operator to connect the cables to the engine, to properly set up the system, to calibrate various measuring devices, and to enter data relating to the engine being tested.

In the area tests, a specified sequence of testing automatically is conducted by the system in order to locate the general area of malfunction. As the operator pushes a proceed button on keyboard 184, the system automatically evaluates the engine under cranking, idle, low cruise, snap acceleration and high cruise conditions. As each area test is conducted, the critical parameters of the engine are measured and displayed on CRT face 192.

After the area tests are completed, the operator may move to any one of several pin point tests designed to locate a specific defective component within the general area of malfunction determined in the area tests. In the process of conducting the tests, the system is capable of generating data on a per cylinder or accumulated basis, as well as measuring the data on a historical basis at time intervals determined by the operator. This mode of operation is particularly useful for studying such characteristics as spark advance curves. During all of the tests, the information is conveniently displayed in alphabetic and numeric, as well as graphical form on CRT face 192.

In order to completely describe the system, the data acquisition circuits will first be discussed in detail. Then the data processor 1090 and processing bus 1096 will be described so that the mode of operation of the analog control system 1100 and the counting and cylinder control system 1400 can be understood. The display circuits will then be described in detail, followed by a discussion of the front panel interface and remote controller which enable the operator to interface with the overall system. Finally, the programmed instructions stored in read-only memory 1094, which control the overall operation of the system, will be described.

CABLE ASSEMBLY 150

Referring to FIGS. 1 and 2a, cable assembly 150 comprises a secondary pattern pick-up 152 which is a capacitive attenuator capable of reducing the high voltage signal at the secondary coil to appropriate levels that can be handled by the amplifiers of the secondary signal sampler. After the secondary signal has been attenuated by the pick-up by factor of about 213:1, the attenuated signal is transmitted to the secondary signal sampler over lead 153.

The primary signal is sampled by a primary clip 154 and a lead 155, as well as a clip 156 and a lead 157 which are connected to chassis ground.

A clamp-on trigger pick-up 158 is normally clipped around the spark plug lead for the number 1 cylinder (e.g., lead 101L) and generates signals each time the number 1 spark plug (i.e., plug 101a) is fired. The signals are transmitted through conductors 159, 159a to the trigger generator.

During area tests, test clips 160, 161, which conduct signals through leads 162 and 163, respectively, are normally connected to the battery with the polarity shown. However, the leads can be used to measure voltage drops across any two points in the automotive system, and the leads also are used for conducting ohmeter and coil/condenser tests.

An ammeter probe 164 is normally connected around one lead of battery 120. The probe is a Hall-effect transducer that can be used to sense the fluctuations in the dc currect flowing into or out of the battery. The probe has a polarity indicator which is necessary to determine the direction of current flow. Such devices are well-known in the art and need not be described in detail. The signal generated by the ammeter probe is conducted to the ammeter circuit by lead 165.

A lead 166 is connected from the monolithic timing pick-up 137 to the monolithic input circuit 210.

CASE ASSEMBLY 180

Referring to FIG. 1, case assembly 180 comprises a front panel 182 that includes a keyboard 184 for reading the digits 0-9 into the system. The panel also includes a control switch assembly 186 which performs various input control functions.

The case assembly is fitted around a conventional display monitor 190, such as Model XM-702-72 manufactured by Motorola Corp., Chicago, Ill. The monitor has a cathode ray tube with a display face 192, for displaying data in alphabetic, numeric or graphical form.

TIMING LIGHT 200 AND TIMING LIGHT CIRCUIT 202

Referring to FIG. 2a, timing light 200 is a conventional device for producing a brilliant flash of light in order to illuminate the timing marks on engine 100. Such devices are well-known in the art and need not be described in detail.

Timing light circuit 202 contains an adjustable delay circuit which flashes the light and generates a FLASH* pulse after an ENG. SYNC* pulse is received at input 204. The operator adjusts the amount of delay in the delay circuit until the flash occurs as timing mark 133 coincides with the 0 advance or top-dead-center line of marks 130. Such circuitry is well-known in the art and need not be described in detail. One circuit is described in U.S. Pat. No. 3,368,143.

MONOLITHIC INPUT CIRCUIT 210

Monolithic input circuit 210 comprises a resistor 211, a capacitor 212, an inverting amplifier 213, and an output conductor 214, connected as shown. (FIG. 2a).

TRIGGER GENERATOR 215

Trigger Generator 215 is used to generate an ENG. SYNC* pulse at the time the no. 1 cylinder of the engine is fired. (Throughout this speciifcation, an asterisk (*) is used to identify the inverse or complement of a pulse or signal identified without an asterisk.)

Referring to FIG. 3, the trigger generator comprises resistors 217-228, capacitors 234-239, transistors 240-243 and a diode 246, connected as shown. A 9 millisecond one-shot multivibrator 247 and a 1.3 millisecond one-shot multivibrator 249 are used to suppress noise which may be picked up on the input in the trigger generator. Output conductor 251 provides an ENG. SYNC pulse when spark plug 101a is fired, and output conductors 252-253 each provide an ENG. SYNC* pulse which is the complement of the ENG. SYNC pulse. An output lead 254 is connected to the primary interface circuit. Transformer coils 256, 257 provide an input signal from trigger pick-up 158, and over voltage protection is provided by a varactor 259.

SECONDARY SIGNAL SAMPLER 264

Secondary signal sampler 264 produces an output voltage proportional to the peak secondary voltage which can be sampled by analog system 1100.

Referring to FIG. 4, the secondary signal sampler comprises input circuitry 265 which includes resistors 266-272, capacitors 274-275, diodes 277-278 and inverting amplifier 280. A threshold detector 282 comprises resistors 284-287 and an amplifier 289, and a driver amplifier 290 is controlled by a feedback resistor 292 and a capacitor 293. A diode 295 allows a storage capacitor 296 to charge to a positive voltage, but prevents the capacitor from discharging in the opposite direction.

Sampler 264 also comprises an output buffer amplifier 298 that is controlled by a feedback resistor 299 and a feedback capacitor 300. The output signal from amplifier 298 is coupled through resistors 301 and 302 to an output conductor 303.

A cross over detector 306 comprising a transistor 307, a diode 308 and resistors 309, 310 provides an output signal which operates through an inverting amplifier 312 in order to switch the output state of a paralysis one-shot multivibrator 314 that is controlled by resistors 316, 317, as well as a capacitor 318. The period of one-shot 314 is approximately 700 microseconds. The Q output of one-shot 314 switches a time delay one-shot 320 which is controlled by a capacitor 321 and a resistor 322 to produce a pulse having a duration of about 70 microseconds. The Q output of one-shot 320 switches the state of a sample pulse one-shot multivibrator 324 which is controlled by a resistor 325 and a capacitor 326 to produce a pulse having a duration of about 70 microseconds.

Sampler 264 also includes inverters 328, 329 which have their outputs connected to leads 330, 331, respectively.

A store one-shot multivibrator 333 is controlled by a resistor 334 and a capacitor 335 to produce an output pulse having a duration of about 300 microseconds.

A NAND gate 336 controls a store-dump circuit 338 comprising resistors 340-345, transistors 347-348 and a diode 349, all of which enable the charging or discharging of capacitor 296.

Referring to FIGS. 4 and 4a, secondary signal sampler 264 operates in the following manner:

Waveforms W1-W10 in FIG. 4a represent the voltage waveforms occurring at the like-lettered points of the circuit shown in FIG. 4. The vertical axis represents volts and the horizontal axis represents time.

W1 represents a fragmentary and somewhat idealized voltage waveform generated by secondary coil 116. The line of waveform W1 form P1 to P2 represents the firing line voltage transmitted to a spark plug in order to fire the plug when points 118, 118a open. Point P2 represents the peak voltage across the plug and the point in time at which current begins to flow across the plug gap. A small oscillation, P3, may occur as current begins to flow across the plug gap. P4 represents the "steady-state" spark line during which current continues to flow across the plug gap.

Amplifier 280 responds to waveform W1 in the manner shown by waveform W2. While the firing voltage is building up across the spark plug, voltage on the output of amplifier 280 increases from approximately 0 volts to the voltage shown at P2'. As the voltage increases, it crosses a threshold level VTH which causes the Q output of one-shot 333 to switch to its 0 state (waveform W4). As the voltage of waveform W2 is increasing from 0 volts to voltage P2', diode 295 is forward biased so that capacitor 296 is charged to a positive voltage. This voltage is fed back from the output of amplifier 298 through resistors 301 and 292 to the inverting input of amplifier 290. Due to the feed back arrangement, the output voltage of amplifier 298 has the waveform shown at W3 in FIG. 4a. Waveform W3 is referred to as the PKV signal in other parts of this specification.

As soon as waveform W2 passes peak voltage P2', diode 295 is reversed biased, and the output voltage of amplifier 290 rapidly decreases to a voltage P6 below 0 volts. This causes the output of crossover detector 306 to switch to its 0 state as shown at point P7 of waveform W6. Waveform W6 remains in its 0 state for approximately 700 microseconds. When waveform W6 is switched to its 0 state at point P7, the Q output of paralysis one-shot 314 is switched to its one state (waveform W7 at point P8), and the Q output of paralysis one-shot 314 is switched to its one state (waveform W7* at point P9). At this same time, the Q output of delay one-shot 320 is switched to its 0 state (waveform W8 at point P10) for about 70 microseconds.

When waveform W8 returns to its one state at point P11, the Q output of sample pulse one-shot 324 is switched to its one state at point P12 (waveform W9) and stays in its one state for about 70 microseconds. As long as either waveform W4 or waveform W7* is in its 0 state, the output of NAND gate 336 is switched to its 1 state (waveform W10). During this time period between points P13 and P14, transistor 348 is switched to its conductive state and transistor 347 is switched to its none-conductive state, so that capacitor 296 can store a positive voltage. As soon as the output of NAND gate 336 returns to its 0 state at time P14, transistor 347 is switched to its conductive state so that capacitor 296 is rapidly discharged.

The discharge of capacitor 296 returns waveform W3 to its initial state, thereby preparing the circuitry for another cycle of operation. As will be explained in more detail later, the time period between points P12 and P15 (waveform W9) defines a sampling period during which the maximum amplitude of the secondary waveform W1 can be sampled on conductor 303. Waveform W9 is referred to as the PKV RET signal in other parts of this specification.

PRIMARY INTERFACE 360

Primary interface circuit 360 generates a DELAYED DWELL* pulse having a duration proportional to the time contact points 118, 118a when closed.

Referring to FIG. 5, circuit 360 includes an input circuit 362 capable of conditioning signals from a positive or negative grounded battery system. Circuitry 362 comprises operational amplifiers 364, 365, each connected as a comparator circuit, as well as resistors 368-379, a capacitor 381 and diodes 383, 384, connected as shown. A conditioning circuit 390 processes signals from conventional as well as high energy ignition circuits by means of operational amplifiers 392, 393, respectively, each of which is connected as a comparator circuit. The conditioning circuit also includes NAND gates 395-397, resistors 400-418, capacitors 421-424, an inverter 426, input conductors 428, 429, and a one-shot multivibrator 430 connected to a diode 431.

A stretching and delay circuit 434 includes transistors 436-438, an operational amplifier 440 connected as a comparator circuit, an inverter 444, resistors 448, 449, 451, 453-458, and capacitors 461-462, all connected as shown.

Driver transistors 530-531 amplify the signals conducted to output conductors 550-551. The transistors are biased by resistors 537-540.

Primary interface circuit 360 is basically used to condition the signals received from engine 100 in order to provide a DELAYED DWELL* pulse.

Referring to FIGS. 5 and 5a, the primary interface circuit 360 operates as follows:

Waveform W12 illustrates an exemplary primary voltage waveform of the type received on conductor 155 from primary coil 115. Waveform W12 includes a firing line P20 generated at the time contact points 118, 118a open in order to fire a spark plug. The line between points P20 and P21 on waveform W12 indicates the time period during which current is gapping across the spark plug. At point P22, contact points 118, 118a close in order to initiate the dwell portion of the ignition cycle. The dwell portion ends at point P21 when the contact points again open in order to fire another spark plug.

Operational amplifiers 364 and 365 are arranged to accommodate either a negative battery or positive battery ignition system, respectively. The amplifiers from input primary signal W12 remove many of the oscillations by means of a comparator technique. For example, the inverting input of operational amplifier 365 may be biased approximately at voltage VT1 (waveform W12). In response to this operation, the output of operational amplifier 365 produces voltage waveform W13.

Operational amplifiers 392 and 393 apply the same comparator technique as amplifiers 364 and 365 in order to convert waveform W13 into a signal more nearly resembling a pulse, such as voltage waveform W14. In order to achieve this result, the inverting input of operational amplifier 392 can be set at approximately VT2 volts (waveform W13). In this mode of operation, operational amplifier 392 produces an output voltage waveform W14 which closely resembles a pulse of the type useful for the data processing apparatus described later.

Operational amplifier 393 is used in connection with so-called high energy ignition (HEI) systems that produce higher voltages than conventional ignition systems. As a result, operational amplifier 393 is less sensitive than operational amplifier 392.

The output of amplifier 393 is connected to the input of one-shot 430 in order to produce an output voltage waveform W17. This voltage is used as a noise blanking signal in order to produce a more nearly uniform pulse at the input of stretching and delay circuit 434.

Monostable multivibrator 430 produces a pulse having a duration of approximately 1 millisecond. It has been found that a multivibrator of this type is needed in connection with certain models of vehicle ignition systems which have a particularly long dwell time period.

NAND gates 395-397 select either the output of amplifier 392 or the output of amplifier 393 for conduction to circuit 434 depending on the state of conductor 429 which is operated from a switch on front panel 182. The switch is set by the operator depending on whether a conventional system or a special high energy ignition system is used in the vehicle being tested. (See FIG. 17a).

The output of transistor 436 is amplified by a transistor 437 and is delayed by a filter and delay circuit comprising resistors 457, 458 and capacitors 461, 462. The delay circuit delays the leading and trailing edges of voltage waveform W14 by approximately 600 microseconds in order to produce a voltage waveform W18. This voltage is amplified by operational amplifier 440 and transistor 438. After being conditioned by inverter 444 and additional driver transistors 530, 531, the waveform and its inverse are transmitted over output conductors 550 and 551 as DELAYED DWELL and DELAYED DWELL* pulses, respectively.

SHORTING CONTROL CIRCUIT 560

Referring to FIG. 6, shorting control circuit 560 comprises a triac 562 having a gate 563 and current conducting terminals 564, 565. The triac is connected in series with a resistor 567. Gate 563 is driven by a transistor 568, as well as a diode 569, resistors 570-574 and a capacitor 576. Inverters 578, 579 provide the various signals with proper polarity. Triac 562 is switched to its conductive state whenever the signal on conductor 580 is switched to its logical 1 state (i.e., whenever a positive AUTO SHORT* is received). Whenever triac 562 is switched to its conductive state, contacts 118, 118a are shorted to ground (except for the low resistance of resistor 567 and triac 562), and the primary and secondary coils are prevented from firing any spark plugs.

PRIMARY ATTENUATOR 590

Referring to FIG. 7, primary attenuator 590 comprises diodes 592, 593, resistors 595-598 and capacitors 600-604, connected as shown. The circuitry filters and clips the primary signal generated by primary coil 115, and provides an input to analog system 1100.

AMMETER CIRCUIT 610

Ammeter Circuit 610 provides output signals proportional to the average amperes and instantaneous amperes flowing through any test wire associated with engine 100, such as the battery cable. The circuit can be automatically ranged and zeroed by the analog system 1100 and data processor.

Referring to FIG. 8, ammeter circuit 610 basically comprises a bias circuit 612, a differential amplifier circuit 630 and a range circuit 662.

Bias circuit 612 comprises an operational amplifier 613, a transistor 614, resistors 616-620, and capacitors 622-624, all connected as shown. The components are arranged to provide a constant voltage for ammeter probe 164 through conductor 627. A feedback signal is returned from ammeter probe 164 over conductor 628.

Ammeter probe 164 incorporates a Hall-effect generator which produces a fluctuating dc voltage between conductors 655 and 657 which is proportional to the instantaneous flux density of the field surrounding the wire around which the probe is placed. The flux density, in turn, is proportional to the current flowing through the wire. One such probe is manufactured by Sun Electric Corp., Chicago, Ill., under part number 6005-0133. The voltage difference is measured by differential amplifier circuit 630 by the use of operational amplifiers 632-635, resistors 638-647 and capacitors 648-653. Conductor 656, resistor 639 and potentiometer 638 serve as zero adjustment elemnents to compensate for the offset of the Hall-effect generator.

On output conductor 659, the differential amplifier circuit provides a voltage having an amplitude proportional to the average current flowing through the test wire; on output conductor 660, the differential amplifier circuit provides a voltage having an amplitude proportional to the instantaneous or actual value of the current flowing through the test wire. The circuitry relating to operational amplifiers 632-634 has a relatively rapid time constant so that rapid dc fluctuations in the current flowing through the test wire result in corresponding fluctuations of the voltage on output conductor 660. The circuitry associated with operational amplifier 635 includes additional filtering and a longer time constant so that the voltage appearing on output conductor 669 is proportional to the average current fluctuation in the test wire.

The sensitivity of differential amplifier circuit 630 is controlled by range circuit 662 which includes NAND gates 664-667, switching gates 669-671, resistors 673-681, potentiometers 683-685 and a capacitor 687. The value of the resistance in the feedback circuit of operational amplifier 632 is controlled by the conductive state of gate switches 669-671. These gate switches, in turn, are controlled by the logical state of the range adjustment signals appearing on range 1 control conductor 688 and range 0 control conductor 689.

VOLTMETER CIRCUIT 700

Referring to FIG. 9, voltmeter circuit 700 produces on an output conductor 746 a voltage signal having an amplitude proportional to the voltage across test leads 162, 163. The circuit can be automatically ranged by analog system 1100 and the data processor.

Circuit 700 includes operational amplifiers 702, 703 and a field effect transistor 704, as well as a protection diode 705. The circuit also includes potentiometers 712-715, resistors 717-735, and capacitors 740-744, all connected as shown.

The gain of amplifier 703 is adjusted by changing the logic state of the signal on input conductor 747. If small voltages are being measured, the range adjustment signal on conductor 747 is switched to its logical 0 state which turns on field effect transistor 704 so that the gain of amplifier 703 is increased. If larger voltages are being measured, the range signal on conductor 747 is switched to its logical 1 state so that the field effect transistor 704 is switched to its non-conductive state, thereby decreasing the gain of amplifier 703. An output conductor 748 transmits a signal to ohmeter-capacitance circuit 750.

OHMETER-CAPACITANCE CIRCUIT 750

Ohmeter-capacitance circuit 750 is used to provide a voltage signal on output conductors 822 and 825 which is proportional to the resistance or capacitance, respectively across which test leads 162 and 163 are placed. Referring to FIG. 10, circuit 750 includes operational amplifiers 752-757 and a one-shot multivibrator 759. NAND gates 760, 761 perform logical switching and additional switching functions are performed by transistors 763-765. The circuit also includes diodes 767-773, resistors 775-805, potentiometers 807-810 and capacitors 811-819. An input conductor 820 provides a switching signal whenever the circuit is intended to measure the value of a capacitor.

CURRENT SOURCE CIRCUIT 830

Current is supplied to test leads 162, 163 for use by the ohmeter-capacitance circuit by means of a current source circuit 830 (FIG. 11). Circuit 830 includes light-emitting diodes 823-837 which are capable of switching photosensitive transistors 842-847, respectively. The circuit also includes operational amplifiers 850-854, transistors 856-862, switching diodes 864-879, a Zener diode 881, resistors 883-913, an adjustable potentiometer 916, capacitors 918-919, and a connecting conductor 926. The amount of current conducted by circuit 832 to test leads 162, 163 is determined by the logical state of an Ohm range 0 conductor 920, an Ohm range 1 conductor 921, an Ohm range 2 conductor 922, an Ohm range 3 conductor 923, an Ohm range 4 conductor 924 and a capacitor select conductor 820.

The circuitry described in FIGS. 10 and 11 operates as follows:

In order to measure the resistance placed across test leads 162, 163, one of input conductors 920-924 is switched to its logical 0 state, depending on the value of the resistor being measured. An appropriate current is then supplied to test leads 162, 163 so that a sufficient voltage is developed across the test leads. This voltage is amplified by operational amplifiers 702 (FIG. 9), 752 and 753 (FIG. 10). As a result, a voltage is produced on output conductor 822 which has a magnitude proportional to the resistance between test leads 162, 163.

When the value of the capacitor placed across leads 162, 163 is to be determined, capacitance select conductor 820 is switched to its logical 0 state at time T0 (FIG. 10a). At that time, the collector of transistor 763 is already at its 0 state (waveform W29 -- FIG. 10a), and the base of transistor 859 (FIG. 11) is already at its 0 state (waveform W30 -- FIG. 10a) so that transistor 859 is in its non-conductive state, thereby allowing the test capacitor connected across test leads 162, 163 to draw current and to store charge. The increase in voltage across the capacitor due to charge storage is amplified by amplifiers 702 and 752 in order to produce voltage waveform W25 (FIG. 10a). When voltage waveform W25 is increased to voltage level VT7 (i.e., at time T1), the output of comparator 754 is switched to its 0 state (waveform W26) so that the output of one-shot multivibrator 759 (waveform W27) is switched to its one state.

Between times T0 and T1, amplifier 755 is operated as an integrator in order to produce voltage waveform W28. At time T1, transistor 765 is switched to its conductive state by the output of multivibrator 759 so that voltage waveform W28 is returned to a low value. Also at time T1, the voltage waveform W29 on output conductor 824 is switched to its one state, thereby causing transistor 859 (FIG. 11) to switch to its conductive state. At time T1, the test capacitor connected between leads 162, 163 discharges through diode 878, transistor 859, resistor 893, diode 879 and resistor 892 so that voltage waveform W25 decays to a low value.

At time T2, the output of multivibrator 759 automatically returns to its 0 state so that transistor 859 is switched to its non-conductive state, thereby allowing the test capacitor to charge. As a result, the circuitry produces the waveforms as shown in FIG. 10a between time periods T2 and T3 which are analogous to the same voltages produced during time period T0 to T1.

The peak value of voltage waveform W28 is proportional to the capacitance of the test capacitor. Operational amplifier 756 and diode 773 cooperate in order to store the peak value of waveform W28 at the inverting input of amplifier 756. The peak value signal is filtered by a network comprising resistors 796-799 and capacitors 817-818. The signal is then impedance matched to output conductor 825 by a buffer amplifier 757. The peak value of the signal produced by the buffer amplifier, (voltage waveform W31) is proportional to the capacitance of the test capacitor.

CONDENSER LEAKAGE TEST CIRCUIT 950

Referring to FIG. 11a, condenser leakage test circuit 950 comprises a step-up transformer 952 which increases the voltage of a 117 volt AC source 952 to approximately 420 volts AC. The circuit also includes diodes 954-956, resistors 958-960, a capacitor 962 and a leakage current resistor 964. Normally open relay contacts K10a, K10b and normally closed relay contacts K10c, K10d are operated by a relay coil K10 (FIG. 12a); normally open relay contacts K11a, K11b and k11c are operated by a relay coil K11 (FIG. 12a) and normally closed relay contacts K12a are operated by a relay coil K12 (FIG. 12a).

During a capacitor leakage test, leads 162, 163 are placed across a condenser which is being tested. In response to the depression of a HIGH-VOLTAGE switch on front panel 182, circuit 950 applies a high voltage to output test leads 162, 163. Any leakage current through the test condenser generates a voltage across resistor 964 which is conducted to the circuitry of FIG. 11 over conductors 163, 162a.

The relay contacts in FIG. 11a are shown in their normal states which exist while a leakage test is not being conducted. When a leakage test is being conducted (i.e., when leakage conductor 1143 (FIG. 12a) is switched to its 0 state by decoder 1142), the relay contacts are switched to their reverse conditions by the current flowing through relay coils K10-K12.

INFRARED EMISSION ANALYZER 1000

Analyzer 1000 is fitted with an exhaust probe 1006 which is placed in the tail pipe assembly of the vehicle being tested. Analyzer 1000 may be implemented by a variety of available devices which are capable of producing an HC output voltage on conductor 1002 having an amplitude proportional to the amount of hydrocarbon emitted from engine 100 and which are capable of producing a CO voltage on conductor 1004 having an amplitude proportional to the amount of carbon monoxide emitted by engine 100. One such analyzer is Model U-912-1 manufactured by Sun Electric Corp., Chicago, Ill.

DATA PROCESSOR 1090

Overall system processing and management is controlled by data processor 1090. The processor performs a number of tasks which may be summarized as follows:

(1) Data is received from analog control 1100 and counting cylinder control 1400 which measure the parameters or conditions of the engine being tested;

(2) Data received from analog control and counting and cylinder control is manipulated to provide output commands to character controller 1800 and graphic controller 2130 which enable the display of alphabetic, numeric and graphical information on display monitor 190; and

(3) The status of keyboard 184 and control switch assembly 186 are periodically monitored to determine the type of engine being tested and the kind of test desired by the operator.

As shown in FIG. 2b, data processor 1090 treats analog control 1100, counting and cylinder control 1400, character controller 1800, graphic controller 2130 and front panel interface as peripheral devices which are interconnected by means of a processing bus 1096. The bus includes output data bus conductors BD0-BD15, input data bus conductors SW0-SW15, address conductors AD2-AD7 and timing signal conductors T1-T4. The signal mnemonics for the pulses transmitted on conductors T1-T4 are shown in Table B.

The manner in which the data processor outputs commands to peripheral devices, such as analog controller 1100 or counting and cylinder control 1400, is shown in FIG. 2c. The data processor operates through a number of microcycles, the 6th and 7th of which are illustrated in FIG. 2c. The bits of data transmitted in the output commands are communicated to the peripheral device over output data bus conductors BD0-BD15. In order to have the data on the BD conductors received by the proper peripheral devices, the proper address of the peripheral device must be placed on the address (AD) conductors during phase T3 of the 6th microcycle (FIG. 2c). During the remaining portion of the 6th microcycle and throughout the 7th microcycle, the address identifying bits on the AD conductors are stabilized. Throughout the 6th microcycle and part of the 7th microcycle, information used internally by the data processor continues to be placed on the output BD conductors. This mode of operation is signified by the x's shown in FIG. 2c during phases T3, T5 and T7 of the 6th microcycle and phase T1 of the 7th microcycle. Just prior to phase T3 of the 7th microcycle, the data processor places on the BD output conductors the bits of information intended to be received by the peripheral device addressed by the AD conductors. As soon as the data has stabilized on the BD conductors, between phases T3 and T4 of the 7th microcycle, the data processor generates a WRITE STROBE pulse. During the duration of the WRITE STROBE, the output data on the BD conductors is stored by the peripheral device for later use. After the WRITE STROBE is returned to its 0 state, a different peripheral device can be addressed and different data can be transmitted to the BD output conductors.

The manner in which the data processor inputs data from a peripheral device is shown in connection with FIG. 2d. As in the case of the output commands, and address of the peripheral device from which information is needed is placed on address conductors AD during phase T3 of the 6th microcycle. Throughout the remaining portion of the 6th microcycle and the 7th microcycle, this address remains stabilized on the AD conductors. During phase T3 of the 7th microcycle, the data processor transmits a READ STROBE on conductor T2 which enables the peripheral device addressed on conductors AD to transmit bits of data over the input data bus conductors SW. During phase T4 of the 7th microcycle, the input data is stabilized and remains stable until the phase T8 of the 7th microcycle. At the end of the 7th microcycle, the data processor returns the READ STROBE to its 0 state, and then can address a different peripheral device to receive additional information.

One suitable data processor is the IMP-16C manufactured by National Semiconductor Corporation, Santa Clara, Calif. The IMP-16C is a 16 bit parallel processor having an arithmetic unit and a control unit. The processor includes a read/write memory for temporarily storing values. For example, the values of various modified engine conditions or parameters are temporarily stored before they are transmitted to character controller 1800.

As shown in FIG. 2b, data processor 1090 is used in connection with a read only memory 1094 having a storage capacity of about 4k. The IMP-16C processor can be used with a variety of read only memories as long as they have an access time equal to or less than 850 nanoseconds. Instructions for wiring read only memory 1094 and connecting it to the processing bus and data processor may be found in the IMP-16C Application Manual published by National Semiconductor Corporation in January, 1974. (Publication No. 420021C).

ANALOG SYSTEM 1100

Analog system 1100 sets up and controls the data acquisition circuits previously described so that the various analog parameters or conditions of the engine are systematically channeled to a single analog-to-digital converter which makes the value of the parameter available to the data processor in the form of a digital measurement signal.

Referring to FIGS. 12a-12f, analog system 1100 basically comprises a range control circuit 1102, a set-up and selection circuit 1160, a sampling control circuit 1246, a real-time clock 1320, a multiplexer 1350, and an analog-to-digital converter 1352.

Referring to FIG. 12a, range control circuit 1102 receives input data from data output bus conductors BD4-BD11 and uses this information to determine the range of the engine parameter circuitry to be selected for a particular measurement. Information received on the data bus conductors is stored in quad latches 1104-1111 during the WRITE STROBE signal as described in FIG. 2c. The proper analog circuitry range is also selected by NAND gates 1114-1126, AND gates 1128-1135, inverters 1138-1140, and a binary decoder 1142. Decoder 1142 is connected to the range control conductors of the data acquisition circuits previously described. Range adjustment signals are transmitted over these conductors. Output conductors 1145-1152 interconnect the components in the manner shown.

Referring to FIG. 12b, set-up and selection circuit 1160 comprises quad latches 1162-1169, data output bus conductors BD0-BD2, AND gates 1172-1176, NAND gates 1178-1179, an inverter 1180, and output conductors 1182-1195, all connected as shown. Referring to FIG. 12c, circuit 1160 also includes address bus conductors AD2-AD7, timing conductors T1-T4, data output bus conductors BD0-BD3, AND gates 1200-1217, NAND gates 1220-1222, inverters 1224-1228, a one shot multivibrator 1230, output conductors 1232-1237, resistors 1240-1241, and a capacitor 1242, all connected as shown.

Referring to FIG. 12d, sampling control circuit 1246 comprises NAND gates 1250-1258 and output conductors 1260-1270. Referring to FIG. 12e, circuit 1246 also includes NAND gates 1274-1281, an AND gate 1283, a one shot multivibrator 1285, a resistor 1286, a capacitor 1287, output conductors 1290-1291, a run switch 1292 shown in the run position and a calibrate switch 1293 shown in the run position. Referring to FIG. 12f, sampling control circuit 1246 also includes one shot multivibrators 1296, 1297, inverters 1299-1302, resistors 1304-1312, capacitors 1314-1315, and output conductors 1316, 1317. As shown in FIGS. 12d -12f, the sampling control circuit receives inputs from conductors 330, 1517 and 502 which determine the point of time at which converter circuit 1352 begins to convert the data received by multiplexer 1350.

Referring to FIG. 12f, real-time clock 1320 comprises counters 1322, 1323, D-type flipflops 1326, 1327. NAND gates 1329, 1330, an AND gate 1331, inverters 1333, 1334, tristate buffers 1336-1343, a resistor 1345 and input data bus conductors SW0-SW7. The real-time clock indicates to the data processor how long an operation has been running. This is particularly useful when the analog measuring circuits are being set-up and selected.

Referring to FIG. 12e, analog-to-digital converter 1352 comprises a digital-to-analog converter 1354, a successive approximation register (SAR) 1356, a comparator 1357, an amplifier 1358, one-shot multivibrator 1360, D-type flipflops 1362-1365, tristate buffer gates 1367, 1368, diodes 1370-1374, potentiometers 1376-1378, resistors 1380-1386, a tristate buffer 1390 and an input conductor 1392 for receiving a clock pulse. A switch 1393 is shown in the closed or run position used during normal operation of the system. During calibration, switch 1393 is moved to its open position.

OPERATION OF ANALOG SYSTEM 1100

Ammeter circuit 610, voltmeter circuit 700 and ohmeter-capacitance circuit 750 each are capable of operating in a plurality of ranges depending on the magnitude of the parameter being measured. Each of these circuits requires the selection of the proper range. Once a range is selected, a time delay is required for the circuitry to settle or establish stable conditions before the analog-to-digital conversion is performed. In order to achieve this mode of operation, the data processor goes through a similar procedure for each of the circuits. The numerical values read in the various ranges is shown in Table C:

If the programming of the data processor calls for any analog value to be read from engine 100, it issues an ADC FLAG RESET OUTPUT COMMAND of the type shown in Table 1.

As shown in Table 1, the OUTPUT COMMAND is performed by placing binary bits 1010 on timing conductors T1-T4, respectively, and by placing binary bits 010001 on address conductors AD2-AD7, respectively. Of course, as explained in connection with FIG. 2c, each OUTPUT COMMAND, including the one shown in Table 1, requires a WRITE STROBE on conductor T3. In response to the coding shown in Table 1, the output of AND gate 1215 (FIG. 12c) is switched to its 1 state so that the output of D-type flipflop 1362 (FIG. 12e) is switched to its 0 state, thereby lowering the ADC READY flag.

After the ADC READY flag has been reset to 0, the data processor can issue an ADC SETUP OUTPUT COMMAND by placing the data bits shown in Table 2 on the address conductors AD2-AD7 and the data output conductors BD3-BD11.

As shown in Table 2, the analog channel (i.e., the parameter to be measured) is coded on conductors BD7-BD11 and is stored in latches 1107-1116, respectively (FIG. 12a). This information is used by multiplexer 1350 to select the proper parameter. The proper range of the parameter selecter for measurement is coded on conductors BD4-BD6 and is stored in latches 1104-1106, respectively during the WRITE STROBE.

After issuing the SETUP OUTPUT COMMAND, the data processor determines the proper period of time delay by inputing the count of real time clock 1320 through a REAL TIME CLOCK INPUT COMMAND shown in Table. 3.

The input command addresses the real time clock by putting the bit code shown in Table 3 on address conductors AD2-AD7. As soon as a READ STROBE is produced, the count of the real time clock is available over input conductors SW0-SW7. As explained previously, the real time clock registers the count of the increments of a free running clock having a period of about 1.008 milliseconds. The clock is capable of registering the count from 0 to 255 and then resetting to 0 and beginning the count again. A REAL TIME CLOCK INPUT COMMAND resets the clock to 0. By subsequently issuing another REAL TIME CLOCK INPUT COMMAND, the data processor can determine the amount of elapsed time, and thereby knows whether the analog circuit has had sufficient time to set up.

After an appropriate amount of time has elapsed, based on data from the real time clock, the data processor initiates the analog-to-digital conversion by issuing an ADC CONVERSION OUTPUT COMMAND as shown in Table 4.

As soon as a WRITE STROBE is received by analog system 1100, the multiplex channel for the required conversion is designated by the bits on conductors BD7-BD11 and the sampling time is designated by the bits on conductors BD0-BD2. Bits BD0-BD2 enable the conversion to take place in synchronism with the DELAYED DWELL* signal on conductor 502, the CYL signal on conductor 1517, or the PKVDET signal on conductor 330. (FIG. 12f). As soon as the conversion is completed, the analog circuitry automatically raises the ADC READY flag by switching the output of D flipflop 1362 to its 1 state.

The data processor determines whether the ADC conversion is completed by inputting the ADC READY flag through an INPUT STATUS REGISTER INPUT COMMAND of the type shown in Table 5.

The status register consists of a number of storage latches, such as 1390 (FIG. 12e) which are scattered throughout the circuitry. By placing the address of the status register on conductors AD2-AD7, (shown in Table 5), the ADC READY flag can be read from the state of conductor SW0, and the status of many other functions in the circuitry can be read from various SW conductors which will be described hereafter. If the data processor finds that the ADC READY flag is in its 1 state, it knows that the analog-to-digital conversion is complete. At this point in time, data processor can receive the digital measurement signal stored in buffer gates 1367, 1368, corresponding to the desired analog parameter, by issuing a READ ADC INPUT COMMAND shown in Table 6.

As shown in Table 6, as soon as a READ STROBE is generated by the data processor, the ADC digital measurement signal is available for storage by the data processor over conductors SW0-SW9.

COUNTING AND CYLINDER CONTROL SYSTEM 1400

Referring to FIGS. 13a-13c, counting and cylinder control system 1400 comprises a cylinder selection circuit 1402, a counter circuit 1412, and a decoder circuit 1417, together with additional components.

Referring to FIG. 13a, cylinder selection circuit 1402 comprises input inverters 1404-1409. The inverters receive inputs from conductors 1438-1442 that are connected to resistors 1438a-1442a and capacitors 1438b-1432b, respectively. Input conductors 1438-1442 receive MOD3*, MOD4*, MOD6*, MOD8* and MOD12* signals from the front panel depending on whether the engine being tested has 3, 4, 6, 8 or 12 cylinders, respectively.

Counter circuit 1412 includes flipflop-type counters 1414-1416 which continuously count through states 0-7 without being reset, except when the circuit is initially connected to an operating engine. After the first pulse transmitted over conductor 1444 is received, the counter circuit is not reset, but continually counts through states 0-7 at a rate determined by the pulses received on conductor 1445.

Decoder circuit 1417 comprises AND gates 1418-1426, NOR gates 1428-1431, NAND gates 1433-1436 and an inverter 1437. The cylinder selection circuit, counter circuit and decoder circuit are interconnected by conductors 1448-1461 through cables 1463, 1464. Output conductors 1470-1473 represent digital bit positions 0-3, respectively for purposes of determining the spark plug of the engine which is about to be fired.

Referring to FIG. 13b, control system 1400 comprises a latch 1478 which receives binary information from data bus conductors BD0-BD3. The circuitry also includes D-type flipflops 1480-1483, a one-shot multivibrator 1485, NOR gates 1487-1490, Exclusive OR gates 1492-1495, AND gates 1497-1500, inverters 1502-1503, resistors 1506-1510, a capacitor 1512, and output conductors 1514, 1516, 1517, 1520 and 1521.

Exclusive OR gates 1492-1495 operate as comparators. When the binary number stored in latch 1478 is identical to the binary number represented on output conductors 1470-1473, the Exclusive OR gates cause AND gate 1498 to produce an output pulse. During the next clock pulse received over conductor 1521, the Q output of flipflop 1482 is switched to its one state and remains in its one state until the binary number represented by conductors 1470-1473 is changed.

Referring to FIG. 13c, counter and cylinder control system 1400 also comprises AND gates 1524-1527 and a NOR gate 1529 which are used to operate the remaining circuitry when an appropriate address in the form of binary data is received on address conductors AD2-AD7.

The system also includes logic gates 1530-1535, switches 1540-1545, and resistors 1550-1555. The circuitry can be used in order to manually introduce data into the data processor by means of manipulating the switches. Output conductors 1557-1558 connect the circuitry in the manner shown.

In order to designate a particular cylinder of engine 100 for shorting or sampling of engine parameters, the data processor issues a CYLINDER SELECT OUTPUT COMMAND shown in Table 7:

If conductor BD15 is switched to its 1 state, the Q output of flipflop 1480 (FIG. 13b) is switched to its 1 state so that inverter 1503 is enabled to produce an AUTO SHORT* pulse. If conductor BD15 is switched to its 0 state, AND gate 1500 is disabled so that no AUTO SHORT* pulse can be produced. During the WRITE STROBE, the number of the selected cylinder is stored in latch 1478 from conductors BD0-BD3.

Referring to FIGS. 14a-14f, counting and cylinder control system 1400 also comprises an operating command decoding circuit 1562, a trigger generating circuit 1564, a phasing and synchronization circuit 1632, a clock and phase generator 1740, a status read-out circuit 1750 and a counter circuit 1764.

These circuits acquire data for measurement of rpm, average and per cyclinder dwell, and average and per cylinder cam lobe or cylinder timing.

Referring to FIG. 14a, circuits 1562 and 1564 comprise a binary coded decimal-to-decimal decoder 1570, one shot multivibrators 1572, 1573, NAND gates 1575-1582, AND gates 1586-1590, a NOR gate 1593, inverters 1595-1602, resistors 1605-1615, capacitors 1618, 1619, and output conductors 1620-1629 which comprise a cable 1630.

Operating command decoding circuit 1562 receives data on input conductors AD5-AD7, T2, T3, and decodes the information in order to determine the type of operation required. Trigger generating circuit 1564 receives timing signals over conductors 214, 206, 1620, and 252 in order to initiate certain modes of operation at the required time.

Referring to FIG. 14b, phasing and synchronization circuit 1632 comprises J-K flipflops 1634-1641, a one-shot multivibrator 1643, NAND gates 1645-1653, AND gates 1656-1658, and amplifier 1660, resistors 1662-1666, a capacitor 1668 and output conductors 1670-1680, all connected as shown. Referring to FIGS. 14c and 14d, circuit 1632 also comprises D-type flipflops 1684-1687, J-K flipflops 1690-1693, NAND gates 1695-1702, AND gates 1706-1709, inverters 1712-1713, amplifiers 1715-1717, resistors 1719-1723 and conductors 1726-1735. Among other functions, circuit 1632 serves as gate circuitry for transmitting clock pulses to counter circuit 1764 or inhibiting clock pulses from being transmitted to counter circuit 1764.

Referring to FIG. 14c, clock and phase generator 1740 comprises divide-by-sixteen counters 1742, 1743, AND gates 1745, 1746, an inverter 1747 and an amplifier 1748. Circuit 1740 generates various clock pulses displaced in phase in order to operate phasing and synchronization circuits 1632.

Referring to FIG. 14d, status read-out circuit 1750 comprises J-K flipflops 1752, 1753, an AND gate 1754, amplifiers 1755, 1756, a resistor 1757, an output conductor 1759 and an output cable 1760. Circuit 1750 provides signals on output conductors SW4 and SW5 which indicate whether certain portions of counter circuit 1764 have overflowed during the counting process.

Referring to FIGS. 14e and 14f, counter circuit 1764 comprises counter-latches 1766-1773, such as National SemiConductor Model No. DM8554. Counterlatches 1766-1769 alternately generate a "P" count and an "N" count, whereas counter-latches 1770-1773 alternately generate an "E" count and a "D" count. When the latches of circuits 1766-1769 hold the N number, they are referred to as the N register, and when they hold the P number, they are referred to as the P register. Likewise, when the latches of circuits 1770-1773 hold the D number, they are referred to as the D register, and when the latches hold the E number, they are referred to as the E register.

Circuit 1764 also includes inverters 1776, 1777, logic gates 1779-1781 and resistors 1783-1790. The logic gates are used to drive input data bus conductors SW1-SW3 in order to indicate flags which furnish information to the data processor.

OPERATION OF COUNTING AND CYLINDER CONTROL SYSTEM 1400

The circuitry shown in FIGS. 13a-13c and 14a-14f operates as follows:

Referring to FIGS. 14c and 14g, clock and phase generator 1740 produces clock pulses CC05678A, CC06 and CC08. These clock pulses are used in order to provide the correct sequencing and synchronization of ignition information in the circuitry. The clock pulses are generated at about 89.286KHz.

FIG. 14h illustrates exemplary primary ignition waveforms PR101, PR102 and PR108 which correspond with the primary ignition signals produced in order to fire spark plugs 101a, 102a and 108a, respectively. Additional ignition waveforms, of course, are produced by primary coil 115 in order to fire spark plug 103a-107a. Also shown in FIG. 14h are the ENG SYNC pulses produced by the circuitry shown in FIG. 3, and the DELAYED DWELL* signal produced by the circuitry in FIG. 5. The DELAYED DWELL* signal is inverted by inverter 1712 (FIG. 14c) and is synchronized by clock signals CC06 in flipflop 1684 in order to produce the PRIM SYZD signals shown in FIG. 14h. The PRIM SYZD signals are transmitted to conductor 1445 in order to advance counters 1414-1416 (FIG. 13a).

When the system is turned on, the first ENG SYNC pulse resets counters 1414-1416, and thereafter, the counters continue to operate in response to the PRIM SYZD pulses without being reset. Due to the delays inherent in the filtering circuits in FIGS. 3 and 5, as well as the synchronizing operation of the circuitry shown in FIGS. 14a-14f, the ENG SYNC, DELAYED DWELL* and PRIM SYZD signals actually may be delayed a few hundred microseconds from their time relationship with the primary ignition signals shown in FIG. 14h.

In order to obtain information about the ignition signals for a particular cylinder of engine 100, the circuitry shown in FIGS. 13a-13c is capable of producing a CYL signal of the type shown in FIG. 14h. In the example shown in FIG. 14h, the CYL signal is used to obtain information for cylinder 102 or spark plug 102a. In order to produce the CYL signal shown in FIG. 14h, the data processor issues a CYLINDER SELECT OUTPUT COMMAND in the manner previously described.

The circuits shown in FIGS. 13a-13c and FIGS. 14a-14c are also used in order to derive digital numbers having values proportional to the time periods designated as N, P. D2 and E2 on FIG. 14h. More specifically, the N number has a value corresponding to the period of time from the opening of points 118, 118a to fire spark plug 101a (time P01, FIG. 14h) until the time the FLASH* signal is received from the timing light circuit over conductor 206 or the time the MONTIM* signal is received from the monolithic timing pick up over conductor 214. The P number has a value proportional to the period from time P01 to time P01' (FIG. 14h). That is, it has a value proportional to the time from one opening of contact points 118, 118a to fire spark plug 101a until the next opening of contact points 118, 118a to fire spark plug 101a. The D number has a value proportional to the period from the closing of contact points 118, 118a to the next opening of the contact points for a selected cylinder (i.e., the dwell time period). In the example shown in FIG. 14h, the D number has a value proportional to the duration from time PC1 to time P02, that is, from the time the points have closed after firing spark plug 101a, until the time the points open in order to fire spark plug 102a. The circuitry can obtain a D number for any selected cylinder, and also can provide an accumulated D number having a value corresponding to the D periods for all cylinders from time P01 to time P01', that is, for the entire ignition cycle. The E number has a value proportional to the time from the closing of points 118, 118a in order to fire a particular spark plug until the next successive closing of the points. This time period is known as the cylinder timing period. In the example shown in FIG. 14h, the E number has a value proportional to the time duration from time PC1 to time PC2, that is, from the time the contact points close in order to prepare for firing spark plug 102a until the time the points close again in order to prepare for firing spark plug 103a. In addition, the circuitry can also provide an accumulated E number having a value porportional to the sum of all the separate E numbers for each of the ignition wave forms occuring from time P01 to time P01', that is, an entire ignition cycle of the engine.

As shown in FIG. 14h, the D number has a value proportional to the time period during which the DELAYED DWELL* signal is in its 1 state and the E number has a value proportional to the time period from one transition of the DELAYED DWELL* signal from the 0 to the 1 state until the next transition of the DELAYED DWELL* signal from the 0 to the 1 state.

A firing time period F is defined as the time period from the opening of contacts 118, 118a to fire a spark plug until the closure of the contacts to start the dwell time period.

Referring to FIG. 14i, the N and P numbers are obtained as follows:

The operator of the system throws an appropriate switch on the front panel (described hereafter) which energizes conductor 1620 (FIG. 14a) so that the circuitry responds to either the MONTIM* pulse received over conductor 214 or the FLASH* pulse received over conductor 206. In this example, it will be assumed that the circuitry is set to be responsive to the MONTIM* pulse.

When the data processor determines that it wants to obtain an N or a P number, it issues a P, N FLAG RESET OUTPUT COMMAND shown in Table 8.

In response to this COMMAND and a WRITE STROBE which switches conductor 1622 to its 1 state, NAND gate 1645 produces a PN CLEAR* pulse and NAND gate 1653 produces an N RESET* pulse (FIGS. 14b and 14i). In response to these pulses, the P FLAG and N FLAG signals are switched from their 1 to 0 states, the counters of circuits 1766-1769 are cleared to their 0 count states, and the PNTRNFR signal is switched from its 1 to its 0 state in order to close the port between the counters and latches in circuits 1766-1769. As shown in FIG. 14i, all of these operations occur at time T0.

As soon as contact points 118, 118a open to produce the next PR1 ignition signal, the ENG SYNC pulse is produced by the circuitry shown in FIG. 3 and is transmitted to conductor 252 (FIG. 14a). In response to this pulse, the PTRIG signal is produced by flipflop 1572. In response to the PTRIG pulse, the PNCNTENABL signal is switched from its 0 to 1 state in order to make the counter portion of circuits 1766-1769 responsive to clock pulses CC05678A. As shown in FIG. 14i, each of these events occurs at time T1.

At time T2, (FIG. 14i), the MONTIM* signal is received over conductor 214 (FIG. 14a). In response to the MONTIM* signal, one shot multivibrator 1573 generates an NTRIG signal which causes the N FLAG signal to switch from its 0 to 1 state. At the same time, the PNTRNFR signal is briefly switched to its 1 state so that the number represented in the counter portion of circuits 1766-1769 is transferred to the latch portion of the circuits. The transition of the PNTRNFR signal to its 1 state occurs between the CC05678A clock pulses so that the counter portion of circuits 1766-1769 continues to count without missing any clock pulses.

After time T2 (FIG. 14i), the N number is held in the latch portion of circuits 1766-1769 and may be read at any time by the data processor. In order to determine whether the N or P numbers are ready, the data processor issues a PN STATUS INPUT COMMAND shown in Table 9:

When a READ STROBE is generated, the status of the PFLAG, NFLAG and POVRFLOW signals can be sensed over conductors SW1-SW3. When the data processor decides to read the N number, it issues a READ N INPUT COMMAND shown in Table 10.

In response to this command and a READ STROBE, the PNREAD* pulse and N READ STROBE* pulse are generated which causes the latches of circuits 1766-1769 to transmit the N number over conductors SW0-SW15 to the data processor. As shown in FIG. 14i, these events occur at the time T3.

At time T4, in response to the N READ STROBE* signal, flipflops 1639, 1640 and NAND gates 1650-1652 cause the PNTRNFR signal to switch from its 0 to 1 state so that the ports between the counters and latches of circuits 1766-1769 are opened. Thereafter, the latches store each number generated by the counters.

The counters of circuit 1766-1769 continue to count clock pulses until the occurrence of the next ENG SYNC* pulse at time T5. At this time, a PTRIG pulse is generated, the PNCNTENABL signal is switched from its 1 to 0 state to prevent the counters of circuits 1766-1769 from responding to any additional clock pulses, and the PFLAG signal is switched from its 0 to 1 state. At this point in time, the P number is held in the latches of circuits 1766-1769 and may be read by the data processor at any time.

When the data processor wants to know the status of the P number, it transmits a PN STATUS OUTPUT COMMAND (Table 9). Since the P FLAG signal is in its 1 state, the data processor knows that the P number is available for reading.

When the data processor desires to read the P number, it issues a P REA INPUT COMMAND shown in Table 11:

In response to this command and a READ STROBE, the PN READ* pulse and N READ STROBE* pulse are generated on conductor 1627. In response to this signal, the latches of circuits 1766-1769 transmit the P number over conductors SW0-SW15 to the data processor.

Referring to FIG. 14j, in order to obtain a D number or an E number, the data processor first determines whether it wants an E or D number for a selected cylinder (the PER CYLINDER mode) or whether it wants to accumulate E or D numbers corresponding to all cylinders of the engine (the ACCUMULATED mode). In order to determine the mode, the data processor issues a MODE CONTROL OUTPUT COMMAND shown in Table 12:

In response to this command and a WRITE STROBE, AND gate 1588 generates a D WRIT signal (FIG. 14a) which enables flipflop 1692 to store the MODE (FIG. 14d). In the example of FIG. 14j, it is assumed that the Q output of flipflop 1692 is switched to its 1 state, indicating the accumulative mode of operation. As shown in FIG. 14j, this switching takes place at time T0. In response to this operation of flipflop 1692, NAND gate 1699 forces the EDTRNFR signal on conductor 1735 to its 1 state.

At time T1, the data processor resets the E FLAG and resets the counters of circuits 1770-1773 to 0 by issuing an E FLAG RESET OUTPUT COMMAND shown in TABLE 13.

In response to this command, NAND gate 1648 (FIG. 14b) generates the EDCLEAR* pulse shown in FIG. 14j. In response to this pulse, the counters of circuits 1770-1773 are cleared to 0.

At time T2, when contact points 118, 118a open in order to create primary ignition signal PR1, the ENG SYNC pulse is generated. In response to the ENG SYNC pulse, the PNCNTENABLE signal is switched from its 0 to 1 state.

Every DELAYED DWELL* signal received on conductor 551 (FIG. 14c) results in a corresponding and slightly delayed DWELL DELAY signal produced at the Q output of flipflop 1685. Subsequent to time T2 (FIG. 14j), each time the DWELL DELAY signal is switched to its 1 state, AND gate 1708 and NAND gates 1701 and 1702 (FIG. 14d) cause the EDCNTENABL signal on conductor 1734 to switch to its 1 state, thereby enabling the counters of circuits 1770-1773 to be responsive to clock pulses CC05678A. Since the time during which the DELAY DWELL signals are in their one state corresponds to the time during which the D number is to be produced, as shown in FIG. 14j, the counters of circuits 1770-1773 accept and count clock pulses each time the EDCNTENABL signal is switched to its 1 state.

This mode of operation continues until time T3 when the next ENG SYNC pulse is generated. At time T3, the PNCNTENABL signal is switched from its 1 to its 0 state, thereby forcing the EDCNTENABL signal to remain in its 0 state. As a result, the counters of circuits 1770-1773 no longer accept clock pulses.

Since the EDTRNFR signal has been in its 1 state during the entire time of operation, the latches of circuits 1770-1773 contain the accumulated D number counted by the counters up until time T3. This D number is available for reading by the data processor. At time T3, the P FLAG was switched from its 0 to 1 state in the same manner described in connection with FIG. 14i. Therefore, in order to determine whether the accumulated D number is available, the data processor determines the status of the P FLAG in the same manner described in connection with FIG. 14i.

If the data processor determines that the P FLAG is in its 1 state, it can read the accumulated D number by issuing a D READ INPUT COMMAND shown in Table 14:

In response to this command and a READ STROBE, an EDREAD* pulse is produced on conductor 1629 by NAND gate 1579 (FIG. 14a). This pulse causes the D number stored in the latches of circuits 1770-1773 to be conducted to the data processor over conductors SW0-SW15.

In order to generate the E and D numbers on a per cylinder basis, the data processor selects the cylinder for which the E and D numbers are to be measured in the manner previously described in connection with FIGS. 13a-13c. In the example shown in FIG. 14k, the cylinder 102 is selected.

In order to establish the per cylinder mode of operation, the data processor issues the MODE CONTROL OUTPUT COMMAND shown in Table 12 so that the Q output of flipflop 1692 (the PERCYLMODE signal) shown in FIG. 14k is switched to its 1 state at time T0.

When the data processor is ready to start generating the E and D numbers, the F FLAG RESET OUTPUT COMMAND (Table 13) is issued so that the ED CLEAR* signal on conductor 1677 is briefly switched to its 0 state at time T1. In response to the ED CLEAR* pulse, NAND gate 1699 (FIG. 14d) switches the EDTRNFR signal from its 1 to 0 state. Also at time T1, the E FLAG signal on the Q output of flipflop 1752 (FIG. 14d) is switched from its 1 to 0 state.

The E and D numbers will not be counted until both the CYL signal transmitted to conductor 1516 from FIG. 13b and the CYLPREP signal generated by the Q output of flipflop 1686 are both in their 1 state (FIG. 14c). If the ED CLEAR* pulse is received during the time the CYL pulse is in its 1 state, the E and D numbers will not be generated until the next occurrence of the CYL pulse. From the trailing edge of the CYL pulse (time T2), the CYLPREP signal is switched from its 0 to 1 state, and the signal remains in the 1 state until the trailing edge of the next successive CYL pulse.

Referring to FIG. 14k, at time T3, when the DWELL DELAY, CYL and CYLPREP signals are all switched to their 1 states, the Q output of flipflop 1687 switches the PERCYLCNT signal from its 0 to 1 state (FIG. 14d). In response to this signal, NAND gate 1701 causes the EDCNTENABL signal on conductor 1734 to switch from a 0 to l state, so that the counters of circuits 1770-1773 begin to count the CC05678A clock pulses on conductor 1726. At time T4 (FIG. 14k) when the DWELL DELAY signal is switched from its 1 to 0 state in response to the opening of contact points 118, 118a, AND gate 1709 (FIG. 14d) generates a DTRNFRENABL pulse which briefly causes the EDTRNFR signal to switch to its 1 state, so that the D number is transferred from the counters of circuits 1770-1773 to the latches of circuits 1770-1773. The D transfer enable pulse is generated between the CC05678A clock pulses, so that the counters of circuits 1770-1773 continue to count the clock pulses in order to form the E number.

At time T5 (FIG. 14k), when the DWELL DELAY signal is switched from its 0 to 1 state in response to the closing of contact points 118, 118a, the CYL, CYLPREP, PRCYLCNT and EDCNTENABL signals are all switched from their 1 to 0 states, so that the counters of circuits 1770-1773 stop counting clock pulses. The E FLAG signal is then returned to its 1 state to indicate to the data processor that the E number is ready to be read.

If the data processor wants to know the status of the E number, it issues an E STATUS INPUT COMMAND shown in Table 15:

In response to this command and a READ STROBE, status read conductor 1625 is switched to its 1 state by AND gate 1587 (FIG. 14a). In response to the STATUS READ pulse, the E FLAG is conducted to the data processor over conductor SW4 (FIG. 14d). Since the E FLAG is in its 1 state at this point in time, the D number is available for reading in the latch portion of circuits 1770-1773, and the E number is ready for reading in the counter portion of circuits 1770-1773.

In order to read the D number, the data processor issues the D READ INPUT COMMAND (Table 14), and the D number is read in the manner previously described at time T6 (FIG. 14k).

After a slight delay created by flipflops 1690, 1691, the EDTRNFR signal on conductor 1735 is switched from its 0 to 1 state so that the E number is transferred to the latches of circuits 1770-1773. Thereafter, at any arbitrary time T7, the data processor can read the E number by issuing an E READ INPUT COMMAND shown in Table 16:

In response to this command and a READ STROBE, an EDREAD* pulse is generated by NAND gate 1579,and the E number held in the latches of circuits 1770-1773 is transmitted to the data processor over conductors SW0-SW15.

CHARACTER CONTROLLER 1800

Character controller 1800 is a charcter generator used to generate the video signals required to display alphabetic, numeric and symbolic characters on the face of the CRT tube located in display monitor 190. The character controller has a refresh capability which continues refreshing the data on the CRT screen once a set of characters has been inputted to the device by the data processor. This same set of characters will be refreshed until a new command is received from the data processor.

Referring to FIGS. 15a-15e, information relating to the display data is stored in a character generator read-only memory 1810. The appropriate data is also generated by a main shift register 1812 and dot display shift registers 1814, 1815. Data identifying the type of information to be displayed, as well as the location of the information on the CRT face, is received and stored in data display address registers 1818, 1819 and character identification latches 1820, 1821.

Controller 1800 also includes refresh buffer memories 1824-1826, a line counter 1829, a character row/line counter 1830, a row-line counter 1831, additional counters 1832, 1833, J-K flipflops 1836-1842, one-shot multivibrators 1845, 1846, NAND gates 1849-1864, AND gates 1865-1906, NOR gates 1908-1920, an OR gate 1924, inverters 1928-1946, Exclusive OR gates 1950-1958, a logic gate 1959, diodes 1961-1964, resistors 1967-2013, and capacitors 2020-2027. The components are connected by conductors 2031-2079 which are schematically shown as merging together into cables 2084-2087. Of course, in practice, the conductors remain isolated from each other. The entrance and exit points from the cables are clearly shown both by the numbers of the conductors at both ends and also by mnemonic identification codes drawn beside the conductors. Additional conductors 2090-2100 are also used in order to interconnect the components.

GRAPHIC CONTROLLER 2130

Graphic controller 2130 cooperates with character controller 1300 and data processor 1090 in order to produce a horizontal bar graph having a length proportional to engine rpm. The graphic controller has the same refresh capability as the character controller.

Referring to FIGS. 16a-16c, controller 2130 includes a latch 2132 which stores a row number corresponding to the row in which the bar graph is displayed and latches 2134, 2135 which store an rpm number controlling the length of the bar graph.

Controller 2130 also includes a row counter 2137 operated by inverters 2138, 2139. As soon as the number counted by the row counter is identical to the row number stored in latch 2132, a comparator 2140 indicates to the bar graph generating circuitry that the proper row has been reached. Comparator 2140 comprises Exclusive OR gates 2142-2145, inverters 2147-2150 and AND gates 2152, 2153. Down counters 2155, 2156 control the length of the bar graph.

Clearing and clocking circuitry within controller 2130 includes D-type flipflops 2158, 2159, inverters 2160, 2161, and NAND gates 2162, 2163.

Additional circuitry for placing the bar graph in the correct lines of the selected row and limiting the graph to the correct length includes a line counter 2164, D-type flipflops 2165-2168, NAND gates 2170-2174, 2177-2179, AND gates 2183-2186, NOR gates 2187-2191, inverters 2193-2196 and resistors 2199-2205. Conductors 2210-2221 are used to interconnect the circuitry in the manner shown, and commands from the data processor are decoded by AND gates 2224-2228, a NOR gate 2230 and inverters 2232, 2233.

OPERATION OF THE CHARACTER CONTROLLER 1800 AND THE GRAPHIC CONTROLLER 2130

The control of information placed on CRT 192 is maintained completely by character controller 1800 and graphic controller 2130. Both of the controllers have refresh capabilities to continue refreshing data on the CRT screen. Once the set of characters and/or bar graph position has been inputted to the controllers by the data processor, this same set of characters and/or bar graph position will be refreshed until a new command is received.

For purposes of character display, CRT screen 192 is divided into 16 horizontal rows (row 0 at the top to row 15 at the bottom) and 32 vertical columns (column 0 at the left to column 31 at the right) (See FIG. 16d). CRT 192 includes an electron beamproducing electron gun which scans the face of the CRT with a predetermined number of parallel beam scan lines at a predetermined rate. Each line is scanned at the same predetermined rate during a time period having a predetermined duration. Character controller 1800 includes a clock, a line counter and a row counter which enable the scan of the electron gun to be divided into rows and lines within a row. A total of 512 characters may be placed on the screen at any one time. The character set normally stored in read-only memory 1810 is described in the following Table S:

Only one character is entered into the controller registers 1818-1821 at a time, and each time a row and column must be specified in a CHARACTER CONTROLLER WRITE CHARACTER OUTPUT COMMAND shown in Table 17:

As shown in Table 17, the address of the character controller is transmitted to conductors AD2-AD7, the BD0 conductor is set to its 0 state, the binary code of the character to be entered into the controller is transmitted to conductors BD1-BD6, the column in which the character is to be displayed is transmitted to conductors BD7-BD11, and the row in which the characters are to be displayed is transmitted to conductors BD12-BD15. The signals by which the column and row are identified constitute display address signals which determine the location on CRT screen 192 at which the character is displayed. These address signals as well as the corresponding character signals transmitted to conductors BD1-BD6, are normally stored in read-only memory 1094.

After the character is stored in the character controller, it is outputted to the CRT screen and the SW0 conductor is set to its 1 state, indicating that a new character can be accepted. The data processor can read the status of the ready/busy flag on conductor SW0 by issuing a CHARACTER CONTROLLER STATUS INPUT, COMMAND shown in Table 18.

The approximate time required to store and display one character is about 1.1 millisecond.

By issuing a CHARACTER CONTROLLER FLUSH OUTPUT COMMAND shown in Table 19, the data processor can erase the CRT screen and all previous character data.

The erase operation takes about 7.0 milliseconds. No reset is required, simply a CHARACTER CONTROLLER STATUS INPUT COMMAND to sense the ready/busy flag.

For any test in which engine rpm needs to be displayed, the character controller and data processor place rpm scale marks in row 0 and arabic numerals corresponding to rpm is thousands in row 1 of the CRT screen, all as shown in FIG. 16e.

Referring to FIG. 16f, the block format for generation of a single character is divided horizontally into 9 clock periods and vertically into 15 lines per row. The rpm scale marks are generated approximately in the first 9 lines of row 0, and the horizontal bar portion of the rpm bar graph is generated in approximately lines 11, 12 and 13 of row 0.

In order to properly position the characters on the CRT screen, the character controller produces a HORBLANK signal at the end of each line. At the end of each 15 HORBLANK pulses, the controller knows that a row has been completed, and therefore, generates a ROWEND pulse. In addition, when the entire face of the CRT screen has been scanned, the controller produces a FRAMESTART pulse indicating that a new frame has started. These pulses are used by both the character controller and graphic controller in order to insure that video information is transmitted to the monitor over conductor 2090 (FIG. 15e) at the proper instant to place the character or graph in the correct position on the CRT face. The characters can be displayed on the CRT screen in a character group consisting of one or more characters.

Referring to FIGS. 16a-16c, the graphic controller can eliminate the bar graph shown in FIG. 16e from the CRT face by issuing a GRAPHIC CONTROLLER OUTPUT COMMAND shown in Table 20.

In response to this command, the Q output of flipflop 2166 (FIG. 16b) is switched to a state which prevents pulses from being transmitted on the graphic output conductor 2066 (FIG. 16c).

The data processor can display the bar graph by issuing a GRAPHIC CONTROLLER DISPLAY OUTPUT COMMAND shown in Table 21.

That is, conductor BD15 is switched to its 1 state, the states of conductors BD0-BD8 determine the length of the bar graph, and the states of conductors BD9-BD12 determine the row in which it is displayed. In the present example, the bar graph is displayed in row 0 of the CRT face. (FIGURE 16e). The row number is normally stored in read-only memory 1094.

Referring to FIG. 16a, four binary 0's corresponding to row 0 are stored in latch 2132. As soon as row counter 2137 is reset to its 0 state by the receipt of a FRAMESTART* pulse on conductor 2095, comparator 2140 switches the output of AND gate 2153 to its 1 state. The FRAMESTART* pulse also resets counter 2164 to its 0 state. Thereafter, counter 2164 begins to count HORBLANK* pulses received from the character controller over conductor 2093. Thus, line counter 2164 advances one count at the end of each line of the display.

As shown in FIG. 16e, the rpm bar graph consists of a vertical pointer P which is 6 lines tall and a horizontal bar B which is 2 lines wide. Pointer P is generated in lines 4, 5, 6, 7, 8 and 9 of row 0 of the CRT display. In order to display the pointer, the output of AND gate 2186 is switched to its 1 state after line counter 2164 has counted 4 lines (i.e., 4 HORBLANK* pulses).

At the end of every display line, upon receipt of each HORBLANK* pulse, down counters 2155, 2156 are loaded with the length number stored in latches 2134, 2135. The number stored in the latches corresponds to the number of CLK* pulses received on conductor T4 which will give the appropriate designation of rpm on the rpm scale (FIG. 16e). Each clock period is 175 nanoseconds and corresponds to about 27.8 rpm on the rpm scale. In line 8 of row 0, as soon as counters 2155, 2156 have been counted down to 1 by the receipt of CLK* pulse, the output of NOR gate 2187 (FIG. 16b) is switched to its 1 state so that a pulse is clocked through D-flipflop 2165. This pulse, in turn, is gated through NAND gate 2179 and AND gate 2184 (FIG. 16c). The pulse is delayed by one clock period in D-type flipflop 2168 and is then transmitted over conductor 2066 to the character controller for display on the CRT screen. The same procedure is used in lines 5, 6, 7, 8 and 9 in order to generate the pointer P of the bar graph.

At the beginning of lines 10 and 11, row 0, the output of AND gate 2185 is switched to its 1 state. As a result, NAND gate 2178, AND gate 2184 and D-type flipflop 2168 enable the transmission of pulses to the character controller in response to the receipt of each CLK* pulse. As soon as counters 2155, 2156 have been counted down to 0 on each line, the output of NOR gate 2191 is switched to its 0 state to prevent additional graphic bar pulses from being transmitted to the character controller over conductor 2066. As a result, the bar and pointer are terminated at the appropriate point on the rpm scale (FIG. 16e).

The same procedure is followed for line 11 of row 0, so that the bar graph is displayed for the appropriate length in each of these lines. At the beginning of line 12, the outputs of both AND gates 2185 and 2186 are in their 0 state, thereby preventing the display of the bar graph in any additional lines of row 0.

FRONT PANEL INTERFACE CIRCUIT 2240

Referring to FIGS. 17a and 17e, front panel 182 includes the front panel interface circuitry 2240. As indicated in FIG. 17a, the circuitry includes the following set-up switches which must be properly adjusted by the operator before the system is ready for operation: cylinder number switch 2250, timing switch 2290, ignition type switch 2296, and ignition selector switch 2300.

Cylinder number switch 2250 is settable to the 2, 3, 4, 6, 8 and 12 cylinder positions which correspond to conductors C2, C3, C4, C6, C8 and C12, respectively. The information derived from the conductors is coded by AND gates 2252-2259 which are biased by resistors 2262-2268. The coded information is recorded in a panel register 2270 comprising latches 2272-2287, and the coded number of cylinders in engine 100 is held in latches 2272-2275.

Timing switch 2290 is set to the "magnetic" position corresponding to contact 2292 if timing information is to be received by magnetic pick-up 137 and is set to the "manual" position corresponding to contact 2293 if timing information is to be introduced by manual means, such as a timing light. The type of timing selected by switch 2290 is stored in latch 2282 of the panel register.

Ignition type switch 2296 is moved to the "2 cycle" position, corresponding to contact 2298, if a two-cycle engine is tested, and is moved to the four-cycle position, corresponding to contact 2299, if a four-cycle engine is tested. This information is stored in latch 2283.

Still referring to FIGS. 17a and 17e, the front panel includes a pin point mode switch 2304 which has contacts 2306-2308 corresponding to the "history", "latest" and "per cylinder" modes, respectively. Information from these contacts is coded by AND gates 2310, 2311, biased by resistors 2313-2315. The information is then stored in latches 2284, 2285 of the panel register.

The front panel also includes a pin point switch 2318 and an area switch 2320 which determine whether pin point or area tests are performed by the system. This information is coded by means of resistors 2322, 2323, NAND gates 2325, 2326 which prevent the pin point and area switches from being activated at the same time. If the pin point switch is activated, an amplifier 2328 illuminates a light bulb 2829 in order to indicate the mode of operation to the operator. If the area switch is activated, an amplifier 2330 illuminates a light bulb 2331 in order to indicate this mode of operation to the operator.

The type of pin point test desired by the operator is indicated by switches 2333-2339 which correspond to amperes, ohms, volts, ignition, condenser, infra-red emission analyser, and high voltage (leakage) tests, respectively. The information for switches 2333-2338 is stored in latches 2276-2281, respectively and the information from switch 2339 is stored in latch 2287. Resistors 2342-2344 bias the panel register and an output conductor 2345 is used to read the panel register in the manner described hereafter. Switches 2333-2338 are each shown in their off position connected to the 1 (e.g., A1) inputs of latches 2276-2281. In order to indicate that a pin point test is requested, the operator depresses the switches on the front panel which cause them to be moved to the "on" or 2 (e.g., A2) positions on the inputs of latches 2276-2281.

Referring to FIGS. 17a-17c, keyboard 184 has 20 switches which are conductively connected through a cable 2346 to a conventional encoder 2348. The encoder communicates with the circuitry shown in FIG. 17c through conductors 2350-2358. Each time the ENTER, RESTART 1, RESTART 2 and 0 switches are pushed, the respective conductors 2350, 2355, 2356 and 2357 are switched to their 0 states. The remaining conductors 2351-2354 are used to code the remaining switches of keyboard 184 into a binary code.

Referring to FIG. 17c, information transmitted from the keyboard is stored in a keyboard register 2359 comprising latches 2360-2364, as well as a latch 2365 used to indicate a request for an amperes calibrate procedure.

Circuitry used for transmitting keyboard data to latches 2360-2364 and for setting the KB FLAG in latch 2452 of the status register includes NAND gates 2370-2377, AND gate 2379, NOR gates 2380, 2381, one shot multivibrators 2382, 2383, inverters 2386-2390, resistors 2393-2408, a diode 2412 and capacitors 2415-2424.

If any of the switches on the keyboard is depressed, the normally 0 output of NAND gate 2375 is switched to its 1 state. As a result, the output of NOR gate 2380 is switched to its 1 state for about 1 millisecond so that NAND gates 2370-2374 can transmit data from the keyboard into latches 2360-2364, respectively. Thereafter, the 0 state of the output of NOR gate 2380 prevents additional information from being entered into latches 2360-2364. At the same time the output of NOR gate 2380 is switched to its 1 state, the output of the flipflop formed by NAND gates 2376, 2377 is switched to its 1 state in order to set the KB FLAG in latch 2452 to its 1 state. If a pulse is received over conductor 2526, the output of the flipflopp formed by NAND gates 2376, 2377, is reset to its 0 state, thereby resetting the KB FLAG to its 0 state and also resetting the keyboard register 2359 to its 0 state.

If the operator wants the system to perform an amps calibrate routine, he closes switch 2430 (FIG. 17d) which is located physically on the ammeter probe. Closure of switch 2430 stores a logical 1 signal in latch 2365 by means of one-shot multivibrator 2432, an inverter 2434, a diode 2435, resistors 2437-2442, capacitors 2444-2447 and a conductor 2449. Latch 2365 is reset at the same time the keyboard register 2359 is reset.

Referring to FIG. 17c, the DELTA FLAG is stored in latch 2453 of the status register in order to control the data displayed by the character and graphic controllers, as well as the sampling time interval of various engine parameters. The operator can control the data display and sampling time intervals by means of a refresh rate switch 2455 (FIG. 17a) which includes a potentiometer slide 2456 and a command switch 2457.

During the automatic phase of operation, switch 2435 is moved to the automatic portion of its span shown in FIG. 17a which causes switch 2457 to close. The time required in order to store a DELTA FLAG in latch 2453 is then controlled by the time period of oscillator 2460. The oscillator, in turn, is controlled by capacitor 2463 and resistors 2465-2467. The rate at which the oscillator produces pulses can be controlled by means of potentiometer slider 2456 from about 0.1 to 10 seconds. When the oscillator produces a pulse in the automatic mode, it is transmitted and stored in latch 2453 by means of NAND gates 2469-2472, an AND gate 2474, an inverter 2475 and resistors 2477-2480.

If switch 2455 is moved to the command position shown in FIG. 17a, oscillator 2460 no longer controls the rate at which a DELTA FLAG is stored. Instead, in order to store a DELTA FLAG in latch 2453, the ENTER switch on the keyboard must be depressed, or a button on the remote controller must be depressed. In either case, the enter conductor 2350 is switched to its 0 state, which results in the storing of a DELTA FLAG in latch 2453 by means of a one-shot multivibrator 2482, a diode 2483, resistors 2485, 2486 and capacitors 2488, 2489.

Referring to FIG. 17d, the circuitry for reading and resetting the KB, panel and status registers includes AND gates 2492-2502, NOR gates 2506-2508, NAND gates 2510-2514, inverters 2517-2519 and conductors 2523-2527.

In order to read the information stored in the panel register, the data processor issues a PANEL REGISTER READ INPUT COMMAND shown in Table 21.

As previously explained, as soon as a keyboard switch is depressed, the KB FLAG is stored in latch 2452. The data processor recognizes that keyboard data is prepared to be read by issuing a STATUS REGISTER READ INPUT COMMAND shown in Table 22.

By issuing the command, the data processor can read the status of the KB FLAG from conductor SW14.

If the KB FLAG is positive, the data processor reads the information on the keyboard by issuing a KEYBOARD REGISTER AND AMP.CAL. READ INPUT COMMAND shown in Table 23.

By issuing this command, the data processor can read the keyboard data from conductors SW0-SW4 and can determine whether an amps calibrate request is made from the state of conductor SW6.

After the data from the keyboard register is read, the KB FLAG is reset by issuing a KEYBOARD RESET OUTPUT COMMAND shown in Table 24.

In this command, conductor BD14 is switched to its 1 state, FIG. 17d, so that AND gate 2500 produces a pulse which resets the keyboard register 2359 and the KB FLAG and latch 2452.

In order to reset latch 2365, which determines whether an amps calibrate routine is requested, the data processor issues an AMP CAL RESET OUTPUT COMMAND shown in Table 25.

During this command, conductor BD13 is switched to its 1 state (FIG. 17d), so that AND gate 2503 transmits a pulse which resets latch 2365.

In order to determine whether additional data should be displayed or generated, the data processor from time-to-time issues a status register read input command to determine the state of the DELTA FLAG on conductor SW15. This command is shown in Table 22. If the DELTA FLAG has been switched to its 1 state, it indicates that a new time interval has elapsed. The data processor then resets the DELTA FLAG, thereby acknowledging that the time interval has elapsed, by issuing a DELTA FLAG RESET OUTPUT COMMAND shown in Table 26.

During this command, conductor BD15 is switched to its 1 state so that AND gate 2501 (FIG. 17d) produces a pulse which resets latch 2450.

Referring to FIG. 18, remote control transmitter 2550 cooperates with a companion radio receiver 2552. A typical transmitter and receiver pair useful for this purpse is manufactured by Intercontinental Dynamics Corporation, Model RT101. In response to the depression of a button 2551 (FIG. 2b) on the transmitter, the receiver generates a voltage pulse for approximately 0.5 seconds on conductor 2553.

Depression of the button either results in a PROCEED command which advances the analyzing system to the next test, or in an ENTER command which allows data to be entered into the system. The response of the system to the depression of button 2551 depends on whether the system is in the command mode, or the automatic refresh mode determined by switch 2455 (FIG. 17a). If the system is in the command mode, switch 2455 opens switch 2457 (FIG. 17c) so that a positive voltage is conducted over conductor 2562 (FIG. 18). In response to this positive voltage, a pulse is transmitted through NAND gate 2556 to conductor 2350. This pulse generates the DELTA FLAG and stores it in latch 2353 (FIG. 17c) in the manner previously described.

If the system is in the automatic refresh mode, switch 2457 (FIG. 17c) is closed so that conductor 2562 is held to ground potential. In this mode of operation, NAND gate 2556 is disabled and NAND gates 2557-2559 are enabled, so that output conductors 2352-2354 are each switched to their 0 state in the same manner as if the PROCEED button of the keyboard had been depressed. As a result, a PROCEED command is stored in latches 2350-2364 of keyboard register 2359 (FIG. 17c).

INPUT STATUS REGISTER

As previously described, a peripheral device called the input status register has storage latches located throughout the circuitry. Most of these latches have been described in connection with FIGS. 12-17. In general, upon the happening of a particular event, one of the devices described in FIGS. 12-17 sets a flag bit to a 1 state. By issuing an INPUT STATUS REGISTER INPUT COMMAND (Table 5), the data processor may read all the bits of the status register to determine the status of the flag in question. The data processor also may selectively reset the flag to a 0 state or may leave the flag bit in its 1 state by means of output commands previously described. The location and function of the various input status register flag bits is summarized in Table 27:

SYSTEM PROCESSING AND MANAGEMENT

The preferred embodiment of the present invention is structured around data processor 1090 which is a 16 bit, parallel bus microprocessor having multiple accumulators, a LIFO stack, and a microinstruction set implemented in a control read-only memory for interpretation and execution of macro-level assembly language instructions.

Data processor 1090 manages the acquisition of analog and digital data from engine 100, processes the data and displays the results in alphanumeric and graphical form on CRT face 192 of display monitor 190. The system is managed under the control of front panel 182 and keyboard 184. By the use of switches 2318 and 2320 (FIG. 17a), the operator may select either pin point tests or area tests for display on the CRT screen:

The area tests are conducted in a program sequenced manner in order to locate a general area of engine malfunction. As the operator pushes the remote control button 2551 or the PROCEED button on keyboard 184, the next area test in the sequence is initiated. Until the operator pushes the PROCEED button, the data processor updates the data on the CRT screen at a refresh rate determined by the position of Refresh Rate switch 2455. The operator is allowed to push the BACK SPACE button on keyboard 184 if he wishes to return at any time to the previous step in the test sequence. Pushing the RESTART button on the keyboard at any time aborts the sequence, flushes or blanks the CRT screen, and returns the operator to the setup phase of operation.

In order to obtain the analog and digital data required for display on the CRT screen in both the area and pin point tests, the data processor steps through a basic executive control sequence schematically shown in the flowchart of FIG. 19. This sequence is common to all test modes and is used throughout all data acquisition subroutines, area tests and pin point tests. The executive sequence embodies a basic set of subroutines used to scan the front panel control switches and registers, read entries from keyboard 184, display characters and messages on the CRT screen, monitor the real time clock, and scan the input status register. The executive subroutines, combined with the calls to them embedded within the measurement and computational program segments, form the executive control sequence.

System status words are stored and updated in a read/write memory contained within data processor 1090. The status words enable the executive control sequence to transfer control to the required program segments or measurement subroutines. The system status words include such items as:

(1) Input status register

(2) Front panel register

(3) Last keyboard entry

(4) Program segment linkages

(5) Mode flags (area or pin point)

(6) Display row and column coordinates

The encircled A in FIG. 19 indicates the initial entry point into the test mode. This same symbol is used to indicate the initial entry point on all area test or pin point test flow charts. The encircled B in FIG. 19 indicates a secondary entry point after test mode initialization and no change in test mode has been requested by the operator through the front panel or the keyboard. The same encircled B symbol is used on all area and pin point test flow charts to indicate a secondary entry point.

As shown in FIG. 19, analog data is acquired and displayed in steps S2, S3, and the digital-type ignition data obtained from the P, N E and D registers is acquired, computed and displayed in steps S4 and S5.

The manner in which the analog data is acquired and displayed is more fully described in the analog-digital converter data acquisition and display flow chart of FIG. 20. As shown in step S24, the data processor sets the range code of analog control system 1100 as required. As previously explained, the range is set by issuing the ADC FLAG RESET and ADC SETUP output commands described in Tables 1 and 2. Basically, the data processor first reads the highest numbered range of ammeter circuit 610, voltmeter circuit 700 and first reads the lowest numbered range of ohmeter-capacitance circuit 750. If the value of amperes or volts obtained from ammeter circuit 610 or voltmeter circuit 700 is lower than the stored range number (Table C), the next lower numbered range is read. If the value obtained from ohmeter-capacitance circuit 750 is too low, the next higher numbered range is read. As a result of this operation, amperes, volts and ohms are always measured in the range of the analog circuits which maximizes accuracy. This is an important feature which enhances the accuracy of the system without intervention by the operator. The range is altered by changing the range adjustment signal line which is activated by decoder 1142 (FIG. 12a).

In step S33 of FIG. 20, the data processor delays the conversion of analog data by reading real time clock 1320 through a REAL TIME CLOCK INPUT COMMAND (Table 3). As previously explained, the delay period is needed in order to allow certain of the analog data acquisition circuits to settle and attain stable conditions. The amount of time required varies from one circuit to the next and extends from a low of 50 milliseconds settling time required to read the actual amperes from circuit 610 to a high of 6000 milliseconds settling time required for the condenser leakage test conducted by circuits 750, 830 and 950.

In step S28, the data processor issues an ADC CONVERSION OUTPUT COMMAND (Table 4) which causes the conversion of the analog signal to digital form. In step S31, the status of the conversion is determined by issuing an INPUT STATUS REGISTER OUTPUT COMMAND (Table 5). If the conversion is complete, the result is read from buffers 1367, 1368 in step S36 by issuing a READ ADC INPUT COMMAND (Table 6). If the resulting digital number is outside the proper range, the program returns to step S24 where the range is adjusted by switching a different output of decoder 1142 to its 1 state.

If an overflow condition exists in which no range can read the parameter, the overflow symbol (Table S) is displayed in step S39. This is a unique feature which enables the operator to tell at a glance that the parameter can not be measured.

In step S42, K is 2500. If no conversion has been completed within 2.5 seconds, the invalid data signal is displayed (step S43).

Once an analog parameter reading has fallen within the limits defined by the ranging criteria, it can be converted to a decimal number for display in engineering units on CRT face 192 using the following formula:

Units = (ADC reading obtained from buffers 1367, 1368) (conversion factor).

The data processor automatically uses the foregoing formula in order to accurately convert the digital measurement numbers obtained from buffers 1367, 1368 to digital display signals having an engineering unit suitable for display on CRT face 192 and understandable to the operator of the system. The digital display signals are stored in the read/write memory of processor 1090 before they are outputted to character controller 1800. This is a unique feature which enables a parameter to be displayed in different engineering units merely by changing the processor program.

One example of the ability of the system to perform non-linear scaling and complex linearization on measured engine parameters is shown in connection with the emissions data acquisition and display flow chart of FIG. 21. In step S51 of FIG. 21, NHC corresponds to the value read from buffers 1367, 1368 of analog system 1100 when multiplexer 1350 is programmed to read the value of the hydrocarbon (HC) parameter. NCO corresponds to the value read from buffers 1367, 1368 of analog system 100 when multiplexer 1350 is programmed to read the carbon monoxide (CO) parameter. In step S58, the data processor calculates the equation shown in order to linearize the values of HC and CO which are displayed on CRT screen 192 in step S59. Constants A1-D1 and A2-D1 are normally stored in memory 1094. The values of constants A-D, are 313.6, 30.57, -3.330 and 0.7342 respectively, and the values of constants A.sub.2 -D.sub.2 are 0.2053, 0.2471, 0.02507 and -0.0005394, respectively. In addition, L1 used with XHC = 50 parts per million, L1 used with XCO = 0.1%, K = 14 millivolts per bit and M = 5.

Aside from the analog parameters, the data processor calculates a number of digital type engine parameters obtained from the P, N, E and D registers. The manner in which this data is obtained by the data processor is shown in the flow charts of FIGS. 22 and 23. FIG. 22 describes the acquisition and display of the P, N and accumulated D numbers, and FIG. 23 describes the acquisition and display of the E number and the D number of a per cylinder basis.

In steps S65, S66 (FIG. 22), the status of the N and P registers is determined by issuing a PN STATUS INPUT COMMAND (Table 10). In step S78, the N register is read by issuing a READ N INPUT COMMAND (Table 10); in step S80, the P register is read by issuing a P READ INPUT COMMAND (Table 11). In step S82, the program determines whether the PC mode has been set by use of the MODE CONTROL OUTPUT COMMAND (Table 12). In step S90, the P and N registers are reset by issuing a P, N FLAG RESET OUTPUT COMMAND (Table 8) and the E and D registers are reset by issuing an E FLAG RESET OUTPUT COMMAND (Table 13). In step S97, the value of K is 10,000.

In step S105 (FIG. 23), the status of the D register and number is determined by issuing an E STATUS INPUT COMMAND (Table 15). If the D number is available, it is read in step S108 by issuing a D READ INPUT COMMAND (Table 14). The value of X in step S106 is 400.

After waiting 50 microseconds (step 109), the E number is read in step S110 by issuing an E READ INPUT COMMAND (Table 16). The E and D registers (circuits 1770-1773) are then reset in step S112 by issuing an E FLAG RESET OUTPUT COMMAND (Table 13). Of course, the flowchart of FIG. 23 assumes that the per cylinder (PC) mode has been set by the use of a MODE CONTROL OUTPUT COMMAND (Table 12).

The engine timing calculation required in step S94 of the flowchart of FIG. 22 is shown in FIG. 24. The "MFG. OFFSET" referred to in step S129 of FIG. 24 is the number of degrees (specified by the manufacturer) by which the monolithic timing mark 136 precedes the top dead center position of the engine. This offset in degrees is entered into the system on keyboard 184 by the operator during the set-up procedure. As previously explained, the engine timing is the number of degrees before or after the top dead center position of the engine at which the number one spark plug is fired. If the number one spark plug is fired before the top dead center position, the engine timing is displayed as an advance value. If the number one spark plug is fired after the top dead center position, the engine timing is displayed as a retard value. This display technique is illustrated in steps S135 and S137 of FIG. 24.

The calculations of RPM (speed), average dwell, dwell per cylinder, cylinder timing per cylinder, and average cylinder timing referred to in step S94 of FIG. 22 and steps S118, S120 and S124 of FIG. 23 are defined in Table 28:

TABLE 28

Rpm for 2 cycle engines = 2678578/P,

Rpm for 4 cycle engines = 2(2678578)/P

Dwell per cylinder = d/p (360.degree.)

average dwell = (.epsilon.d)/qp (360.degree.)

cylinder timing per cylinder = (e)/p (360.degree.) -360.degree./q

(cam lobe)

average cylinder timing = (.epsilon.e)/qp (360.degree.) - (360.degree.)/q

(cam lobe)

p = p number obtained from circuits 1766-1769 (FIGS.14e and 14i)

D = d number obtained from circuits 1770-1773 in the per cylinder mode (See FIGS. 14f and 14k)

.epsilon.D = D number obtained from circuits 1770-1773 in the accumulative mode (i.e., sum of D numbers for all cylinders; See FIGS. 14f and 14j)

Q = number of cylinders in engine 100

E = e number obtained from circuits 1770-1773 in per cylinder mode (See FIGS. 14f and 14k)

.epsilon.E = E number obtained from circuits 1770-1773 by repetitively operating in the per cylinder mode for each different cylinder according to the routine described in FIG. 23 (i.e., sum of E numbers for all cylinders; See FIGS. 14f and 14j)

As seen in Table 28, when the P number is used to calculate RPM, it constitutes a digital RPM signal which is inverted by the data processor.

The data processor includes numerical averaging techniques for engine parameters having continuous variations, such as engine speed and the peak kilovolt (PKV) output of the secondary coil. The averages are taken over a predetermined number of engine revolutions or a fixed number of readings depending upon the display requirements. Examples of these averaging techniques will be described more fully in connection with area tests 1 and 5.

The data processor uses the foregoing data acquisition, calculation and display capabilities in order to properly calibrate and set up the system, conduct area tests designed to uncover general areas of malfunction, and conduct pin point tests designed to isolate a defective component within the general area of malfunction.

The basic organization of these set up procedures and tests is described in the man/machine flow diagram of FIG. 25. When the system is first turned on, step S140 of FIG. 25 results in the display on CRT face 192 shown in FIG. 26. This display communicates instructions to the operator which enables cable assembly 150 to be connected to engine 100 in the manner shown in FIG. 1.

When the PROCEED button (or remote control button 2551) is pushed, step S141 is entered which results in the display shown in FIG. 27. The operator is informed to select the number of cylinders in the engine, ignition type, ignition selector position and type of timing by operating switches 2250, 2296, 2300 and 2290. The display of FIG. 27 also invites the operator to enter the TDC offset angle of the magnetic or monolithic timing input. The offset angle of the monolithic mark supplied by the manufacturer is entered by the operator on keyboard 184 (See S129 of FIG. 24). If the value is accepted by the data processor, it is displayed in the lower right hand corner of the CRT face in the position indicated by the x's in FIG. 27. If the operator makes an error in entering the offset angle, the data processor displays the word ERROR in the place where the word ACCEPTED is shown in FIG. 27. The operator can then attempt to correct the offset angle by entering a new value in the keyboard. If the new value is accepted, the display shown in FIG. 27 is outputted to the CRT face.

When the PROCEED button on the keyboard is pushed, step S142 (FIG. 25) is entered and the display shown in FIG. 28 is generated. The operator is invited to close amps calibrate switch 2430 (FIG. 17d) so that the data processor automatically goes through an amps calibration routine wherein the ambient field picked up by ammeter probe 164 is read and is automatically stored in the memory for use later in the program. The stored ampere value provides a 0 offset value which is substracted from the later-acquired ampere readings.

When the PROCEED button is again depressed, step S143 (FIG. 25) is entered and the display shown in FIG. 29 is generated. At this point in time, the operator pushes either an AREA or PIN POINT button (FIG. 17a). If the AREA button is depressed and the PROCEED button is then depressed, step S144 is entered and the display shown in box S144 of FIG. 25 is generated. When the PROCEED button is again pressed, the area tests are entered.

AREA TESTS

In area tests, a specified programmed sequence of tests is conducted by the data processor to locate a general area of engine malfunction. As the operator pushes the PROCEED button on the keyboard, the next step in the sequence is initiated, and, under control of the data processor, the operator is instructed by the CRT display. The results of each area test are displayed in alphanumeric and graphic form. Unitl the operator pushes the PROCEED button, the data processor updates (i.e., converts, calculates and displays) the data on CRT screen 192 at a refresh rate determined by refresh rate switch 2455.

In order to increase the flexibility of the system, the operator may push the BACK SPACE button on the keyboard anytime he desires to return to the previous step in the sequence. Pushing the RESTART button on the keyboard at any time aborts the sequence, blanks or flushes the CRT screen, and returns the operator to the preliminary or set-up phase (steps S140-S144, FIG. 25).

There are seven steps in the area test sequence, and each step corresponds to one "page" of information which is simultaneously displayed on the CRT screen. The seven area tests, together with the test conditions and parameters measured in each test, are described in the following Table 29:

In order to illustrate the flexibility of the system, area tests 1-5 and 7 will now be described in detail:

AREA TEST 1 -- CRANKING

As soon as area test 1 is entered, the data processor causes a display of the type shown in FIG. 30 to be presented on CRT face 192. However, in place of the x's shown in FIG. 30, the data processor presents arabic numbers which quantitatively define the parameters shown in FIG. 30. These numbers are derived from the data processor program segment shown in the flow chart of FIG. 31.

As shown in FIG. 31, step S171 results in the display of the test title and alphabetic format shown in FIG. 30. As previously explained in connection with character controller 1800, in order to display the format shown in FIG. 30, each separate character or symbol, together with its location on the CRT screen, is transmitted one-at-a-time to registers 1818-1821 and is stored in refresh memories 1824-1826 (FIG. 15c). When all the data required to display the format of FIG. 30 has been stored in the refresh memories, the display is commenced. The refresh capability of the character controller is then utilized in order to keep displaying the format until new instructions are received from the data processor. This is an important feature of the system which enables each area test format to be displayed as a single "page" on the CRT face. The page format of presenting data simplifies the task of the operator because he can view all of the critical parameters for each area test at a single glance. The same technique is used to display all other area test formats on CRT screen 192.

As shown in FIG. 30, in order to conduct the cranking test, the operator disables the ignition of engine 100 and cranks the engine by energizing the starter.

In step S172 of FIG. 31, the data processor enables an analog-to-digital conversion of the average amperes flowing through the battery cable (conductor 659) while the engine is being cranked. As shown in step S173, the data processor does not allow the number of amperes, or the number associated with any of the other parameters, to be displayed on CRT face 192 (FIG. 30) until the amperes flowing through the battery cable exceeds a predetermined number K. Normally, the value of K is 50 amperes. This is an important feature whereby the cranking of the engine is automatically detected. The operator is relieved of the responsibility of informing the system that the engine is being cranked. As a result, the proper information is displayed on the face of CRT 192 only during the actual cranking condition of the engine, not while the engine is stopped.

Before the starter draw current is displayed on row 6 of the CRT display (FIG. 30), the ambient current value stored during the amps calibration routine is substracted from the starter draw current value obtained from analog system 1100. This is an important feature which increases the accuracy of the amperes values displayed on the CRT face. A similar subtraction is made before any ampere value is displayed.

As soon as the current flowing through the battery cable exceeds 50 amperes and 1 second has elapsed (X = 1000 in step S175), the system automatically reads, stores and displays the parameters shown in FIG. 30.

Referring to step S180 (FIG. 31), the data processor takes readings of the points closed portion of the primary signal transmitted over conductor 606 to multiplexer 1350 (FIG. 12d). The N signal samplings of the points closed portion of the primary signal are then averaged and displayed opposite the legend "DYN. DIST. RES." on the CRT face 192 (FIG. 30). Normally, N = 8.

As shown in step S181, the average dwell calculation is made over M engine revolutions and is averaged and displayed opposite the "DWELL" legend on CRT face 192 (FIG. 30). Normally, M = 2. The averaging techniques described in steps S180 and S181 are important features which enable stable digital values to be displayed on the CRT face. If averaging were not used, the fractional portion of the number displayed on the screen would tend to continually change, thereby complicating the reading of the value by the operator.

As shown in step S182, data processor 1090 obtains N readings of the peak kilovolt (PKV) signal transmitted to the input of multiplexer 1350 over conductor 303 (FIG. 12d). Only the maximum one of the N readings is displayed on the CRT face opposite the legend "COIL OUTPUT" (FIG. 30). This is an important feature which automatically enables the maximum coil output to be viewed by the operator without the necessity of considering the individual coil outputs associated with each spark plug. In connection with steps S180 and S182, the value of N normally equals 8.

AREA TEST 2 -- ALTERNATOR OUTPUT

When the operator has finished area test 1, he may advance to area test 2 by pushing the PROCEED button on the keyboard. At that time, the data processor causes character controller 1800 to display on CRT screen 192 the format shown in FIG. 32. As shown in FIG. 32, the operator is instructed to enable the ignition system, start the engine, accelerate the engine to a predetermined test speed (e.g., 2500 rpm), and return the engine to idle speed. As the engine is being accelerated to the test speed, the data processor enables the maximum amperes produced by the alternator to be displayed on screen 192, together with the engine speed at which the maximum amperes were generated. These numbers appear in the positions occupied by the x's in FIG. 32.

In order to determine the peak alternator output and the speed at which it is produced, the data processor executes the program segment shown in the flow chart of FIG. 33. In step S186, the data required to display the format shown in FIG. 32 is transmitted to character controller 1800 and is stored in the refresh memories 1824-1826 (FIG. 15c). This results in continual refreshing of the display shown in FIG. 32.

At step S187, the current engine speed is determined and used to generate the rpm bar graph. If the current engine speed is greater than the value S (which is normally set at the engine idle speed, 700 rpm), the average amperes are read from analog system 1100. In step S190, if the current average amperes are greater than the previous average ampere reading, the current reading is stored and displayed. By continuing this process as the engine is accelerated to its test speed, the maximum ampere reading and the corresponding engine speed at which the maximum reading occurs are numerically displayed on CRT screen 192. This is an important feature which enables the operator to accurately read the maximum alternator output, as well as the corresponding engine rpm, without having to evaluate a transient display. The maximum ampere reading, and corresponding rpm, are automatically computed and stored so that the operator can read them at his leisure.

In step S191, the current engine rpm is calculated and displayed on the bar graph scale. This display is executed by means of the commands previously described in Tables 17-21.

AREA TEST 3 -- Idle

When the operator has completed his viewing of area test 2, he presses the PROCEED button on the keyboard and is automatically taken into area test 3. During area test 3, the data processor enables the display of the alphabetic format and rpm bar graph scale shown in FIG. 34 by excuting step S194 of the idle test program segment shown in the flowchart of FIG. 35. The position indicated by x's in FIG. 34 are filled with numbers calculated by the remaining steps of the subroutine shown in FIG. 35.

In step S195, the current engine speed is calculated and displayed both in bar graph form and in numeric form. Average dwell is then calculated in the manner previously described in Table 27 for each of N engine revolutions. As explained in FIG. 35, N = 2 for four cycle engines and N = 1 for two cycle engines. The average dwell values then are averaged over the N engine revolutions and are displayed in step S196. In step S197, the average dwell value calculated in step S196 is stored as an idle dwell value (DL) for use in area test 7. In steps S198 and S199, the current HC and CO readings are measured by use of the commands shown in Tables 1-6, and the subroutine shown in the flowchart of FIG. 20, computed by the use of the subroutine shown in the flowchart of FIG. 21, and displayed by use of the commands shown in Tables 17, 18. In step S200, the engine timing is calculated in the manner described in connection with FIG. 24 and is displayed opposite the legend "INITIAL TIMING" on CRT screen 192 (FIG. 34). The engine timing at idle is then stored in step S201 for later use by the program in area test 7. This is an important feature which enables the timing at high speed (area test 7) to be compared with the idle timing obtained during area test 3. The entire process is conducted automatically by the data processor.

AREA TEST 4 -- LOW CRUISE

When the operator has completed area test 3, he pushes the PROCEED button on the keyboard so that the data processor displays on screen 192 the alphabetic, symbolic and graphical format shown in FIG. 36 by executing step S205 of the program segment shown in the flowchart of FIG. 37. The space occupied by the x's in FIG. 36 is filled with numbers calculated by the remaining steps of the program segment shown in FIG. 37.

In step S206, temporary locations in the read/write (r/w) memory in data processor 1090 are addressed in order to store the maximum and minimum PKV signals (conductor 303) obtained during subsequent steps of the program segment. As shown in steps S207, S208, the PKV signal for a selected cylinder I is read by analog system 1100. If the current PKV value is greater than the previous PKV value, the current value is stored in the temporary memory location as the current maximum PKV value (step S210). If the current PKV value is less than the previous minimum PKV value, the current value is stored as the current PKV minimum value in the temporary memory locations (step S213).

In the loop created by steps S214 and S215, the same procedure is followed for all of the cylinders so that the maximum PKV and minimum PKV reading for all cylinders of the engine are stored in temporary memory locations. The minimum value and the maximum value are displayed opposite the legends "KV (MIN) and KV (MAX)", respectively, on CRT screen 192 (FIG. 36).

According to steps S126-S218, the current engine speed and HC, CO values are also displayed. The HC and CO values, of course, are calculated according to the subroutines and commands discussed in connection with area test 3. The engine speed is displayed both numerically and in bar graph form.

AREA TEST 5 - AUTOMATIC POWER BALANCE

After the operator has completed area test 4, he pushes the PROCEED button to enter area test 5. Then the format shown in FIG. 38 is displayed on CRT screen 192 by execution of step S224 of the program segment shown in the flowchart of FIG. 39. The numbers indicated by the x's in FIG. 38 are filled with numbers calculated by the remaining steps of the program segment described in the flow chart of FIG. 39.

The automatic power balance program segment shown in FIG. 39 sequentially shorts out contact points 118, 118a during the normal firing time of each spark plug of the engine and reports the resulting drop in engine rpm for each cylinder on CRT screen 192. In order to commence the test, the operator is instructed to set the base speed of the vehicle. The base speed can be set by at least two means:

(1) The operator can sit in the vehicle and hold the accelerator pedal in a constant position which causes the engine to rotate at the desired base speed. Normally, the base speed is between 1000 and 3000 rpm.

(2) The operator may use any one of a variety of devices for setting the throttle linkage at a fixed position which creates the desired base speed without the need to sit inside the vehicle.

When the base speed is established, the operator either pushes the PROCEED button on the keyboard or button 2551 on radio remote control unit 2550 so that the proceed code is stored in keyboard register 2359 (FIG. 17c). The data processor periodically scans the front panel switches and keyboard register to determine whether the PROCEED code has been received (step S225). When the proceed code is received, the data processor reads and computes the average engine speed for N engine revolutions, stores the computed value as the base speed (SB), and displays the converted value on CRT screen 192 opposite the legend "BASE SPEED". N is normally equal to 64. Computing the average engine speed for N engine revolutions (step S227) is an important feature which enables the change in rpm calculated when the ignition points are shorted to more accurately represent the condition of the cylinders. If the engine speed were not averaged, then the base speed could fluctuate sufficiently to cause the engine rpm change computed in step S234 to be misleading. Once the base speed has been established, it is up to the operator to maintain the throttle position at the same setting during the entire power balance test.

In step S230, after the base speed has been set, the ignition for a selected cylinder (e.g., cylinder 101) is shorted by generating an AUTO SHORT* pulse. This pulse (i.e., disable signal) is generated by issuing a CYLINDER SELECT OUTPUT COMMAND (Table 7) which operates the cylinder selection circuit 1402 (FIGS. 13a-13c) and shorting control circuit 560 (FIG. 6) in the manner previously described. The selected cylinder then is disabled by shorting contacts 118, 118a at the proper time in each engine cycle.

In step S232, the data processor waits X engine revolutions for the engine to stabilize before the engine speed is read. X normally equals 84. Engine revolutions are determined by counting ENG SYNC pulses.

In step S233, the average engine speed for K engine revolutions is determined (value SSI). K is normally set equal to 64. The value of the engine speed while the selected cylinder is shorted (SSI) is subtracted from the base speed (SB) in order to determine the change in speed for the selected cylinder (SB-SSI). The AUTO SHORT* pulse is then terminated in step S235 so that the engine speed increases to the base speed. Thereafter, the ignition for each of the cylinders is shorted in turn in the loop created by steps S236, S237 so that the change in rpm while each cylinder is disabled is displayed opposite the cylinder number on the CRT face 192 (FIG. 38).

During the entire power balance test, the current engine speed is read and displayed on the rpm bar graph scale located at the top of CRT screen 192.

After all of the cylinders have been disabled, control is transferred to the basic executive routines in step S238. It should be noted that the entire power balance test is conducted automatically by the data processor without the need for intervention by the operator. At the end of the test, the change in rpm for each cylinder is automatically recorded on the CRT face where it can be copied at the leisure of the operator.

AREA TEST 6 -- SNAP ACCELERATION

After the automatic power balance test (area test 5), is completed, the operator pushes the PROCEED button in order to advance into area test 6. In area test 6, the engine is rapidly accelerated and the maximum PKV signal, maximum rpm and maximum CO reading are recorded on the CRT face 192.

AREA TEST 7 - HIGH CRUISE

After area test 6 is completed, the operator pushes the PROCEED button so that the data processor displays on CRT face 192 the bar graph scale and alphanumeric format shown in FIG. 40 by executing step S240 of the program segment shown in the flowchart of FIG. 41. As area test 7 proceeds, numbers are displayed in the positions filled with x's in FIG. 40 by the execution of the remaining steps of the program segment illustrated in FIG. 41.

At the beginning of area test 7, the operator is reminded to bring the engine up to the test speed (e.g., 1000 to 3000 rpm). The manner in which the engine is brought up to and maintained at the test speed has been previously described in connection with area test 5. In step S242, the current engine speed is calculated and displayed numerically opposite the legend "ENGINE SPEED" and graphically on the rpm bar graph scale located in row 0 of the CRT screen. In step S243, the average dwell is calculated in the manner previously described in Table 27. The average dwell reading for N engine revolutions is stored and then averaged. The average of the N average dwell readings is used as the high cruise dwell (DH) reading and is displayed opposite the legend "DWELL" on CRT face 192 (FIG. 40).

In step S244, the idle speed dwell (DL) is recalled from the read/write memory. As explained in connection with the flowchart of FIG. 35, the idle speed dwell was also averaged over N engine revolutions and stored in the read/write memory for later use. In step S245, the subtraction DH-DL is performed by the data processor, and the remainder is displayed opposite the legend "DWELL VARIATION" on CRT face 192 (FIG. 40).

In step S246, the current engine timing is calculated according to the subroutine shown in FIG. 24 and is stored in read/write memory as the high cruise timing (TH). In step S246, the idle speed timing (TL) is recalled from read/write memory. The calculation of the idle speed timing (TL) is described in step S201 of the flowchart of FIG. 35. In step S248, the data processor performs the subtraction TH-TL, and the resulting remainder is displayed as the engine timing advance opposite the legend "TIMING ADVANCE" on the CRT face 192 (FIG. 40). The current or high cruise timing TH is then displayed as degrees advance or degrees retard opposite the legend "INITIAL + ADVANCE" on CRT face 192 (FIG. 40).

As shown in steps S250 and S251, the data processor then measures, computes and displays the current CO and HC values. In step S252, the data processor measures, computes and displays the battery voltage measured over conductors 162, 163 opposite the legend "CHARGING VOLTS".

The ability of the system to store the dwell and timing advance measurements during the idle area test and to recall these measurements during the high cruise test is an important feature. This ability of the system to remember values from one area test to the next enables the operator to determine the changes in variable engine parameters, such as dwell and timing advance, in a convenient manner. These changes are recorded on CRT screen 192 until the operator can thoroughly analyze the results.

After area test 7 is completed, the operator may enter the pin point mode of operation by pushing button 2318 on the front panel (FIG. 17a). At this point in time, the data processor causes the instructions shown in FIG. 42 to be displayed on CRT face 192. This display is made in accordance with step S154 shown in the flowchart of FIG. 25.

PIN POINT TESTS

The pin point tests are selected by depressing buttons 2333-2339 on front panel 182 (FIG. 17a). There are three display modes for the presentation of engine condition or parameter values in the pin point tests which can be selected by switch 2304. These modes correspond to displaying the latest or current value, displaying the values in a historical sequence and displaying the values for a particular cylinder. The rate at which the parameter values are refreshed and displayed in the "latest" mode, and the rate at which the parameters are sampled in the "historical" mode, varies from about 0.2 to 8 seconds depending on the position of switch 2455 (FIG. 17a). Per cylinder information is only meaningful for measuring peak KV, dwell, cylinder timing and amperes. If per cylinder information is requested for other functions or parameters, the data columns are blanked on CRT screen 192.

The position of the data on CRT screen 192 during a pin point test is relative to the particular test selected. When historical data is presented on the screen, 10 sets of values are displayed, with the latest or current value always on the first or top row. The top row is separated from the rest of the values by a blank row. After the 10 sets of values have been displayed, the operator must push the PROCEED button to continue with 10 new sets of data entries.

Since only a limited amount of information can be simultaneously displayed on CRT screen 192, the order of priorities for the parameters is as follows: engine speed, Co, HC, condenser, condenser leakage, peak KV, dwell, engine timing, cylinder timing, volts, ohms, amperes. In the pin point tests, the data processor will ignore requests for display of more than 5 engine parameters. In order to select the engine parameters to be displayed during the pin point tests, appropriate buttons within the group 2333-2339 are pushed. If a newly selected parameter has a priority and column format allowing it to be displayed, or if a selected parameter has a priority greater than the priority of any parameter currently being displayed, the CRT screen will be erased, and the messages "SELECT PIN-POINT TEST MODE, PUSH DESIRED TEST BUTTONS, PUSH PROCEED BUTTON" will appear. The operator then must press the PROCEED button to enter the new parameters. This mode of operation occurs regardless of any pin point mode selection made with switch 2304.

PINPOINT IGNITION TEST IN THE PER CYLINDER MODE

FIG. 43 discloses the rpm bar graph scale and parameter format displayed on CRT screen 192 during the pin point test if switch 2304 is moved to the per cylinder position and ignition button 2336 is pushed. As noted in FIG. 43, the number of each cylinder of the engine is displayed in the left hand column of the FIG. 43 format. Opposite each cylinder, the firing KV, (PKV) dwell degrees, cylinder timing and amps parameters are displayed:

The PKV signal is displayed under the heading "FIRNG KV" (FIG. 43). The manner in which the PKV signal is sampled on a per cylinder basis has been described in connection with the secondary signal sampler 264 (FIG. 4) analog system 1100 (FIGS. 12a-12f), cylinder selection circuit 1402 (FIGS. 13a-13c) and the flow chart of FIG. 20.

Dwell per cylinder is displayed under the heading "DWELL DEG" (FIG. 43). The manner in which dwell per cylinder is calculated and displayed has been previously described in connection with Table 27 and the flowchart of FIG. 23.

Cylinder timing per cylinder is displayed under the heading "CYL TIM". The manner in which the cylinder timing per cylinder is calculated and displayed has been previously described in connection with Table 27 and the flowchart of FIG. 23.

The numbers displayed under the "AMPS" column for each cylinder in FIG. 43 can be understood with reference to ammeter circuit 610 (FIG. 3), analog system 1100 (FIGS. 12a-12f), cylinder selection circuit 1402 (FIGS. 13a-13c), and the flow chart of FIG. 20. Basically, after an ADC CONVERSION OUTPUT COMMAND (Table 4) has been issued, each time the CYL* signal is generated by cylinder selection circuit 1402, analog-to-digital converter 1352 initiates a conversion of the "actual amperes" signal transmitted to multiplexer 1350 over conductor 660. The value of the actual amperes is calculated and displayed opposite the cylinder shown in FIG. 43 for which the CYL* signal is generated.

The "TIM DEG" heading is displayed during the pin point ignition test in the per cylinder mode, but no numbers are entered under the heading. The rpm bar graph also is displayed (FIG. 43).

The ability of the system to measure the parameters shown in FIG. 43 on a per cylinder basis is an important feature which increases the diagnostic value of the information displayed to the operator. The accuracy of the information is enhanced by the method of making direct digital measurements of engine rpm, dwell, and cylinder timing described previously. By making these measurements in the manner described, rpm, dwell and cylinder timing can be accurately measured during a single engine cycle. This is an important consideration when the engine is operated at idle speed and also when the engine is put through the snap acceleration test (area test 6). By measuring dwell and cylinder timing on a per cylinder basis, the operator is able to determine the condition of the ignition system with a degree of accuracy heretofore unattainable.

During the calculation of amperes on a per cylinder basis, the data processor subtracts the initial calibration value obtained during calibration of the ammeter circuit before the amperes value is displayed. This feature enhances the accuracy of the system and enables the operator to determine the amperes flowing through the battery cable with great precision. The ability of the system to automatically and rapidly range and read ammeter circuit 610 provides maximum accuracy and enables measurements of the battery cable current on a real time, per cylinder basis.

CONDENSER PIN POINT TEST IN THE HISTORY MODE

The format displayed on CRT face 192 for the condenser pin point test in the history mode is shown in FIG. 44. In order to initiate this test, the operator places a test condenser (i.e., capacitor) across leads 162, 163 (FIG. 2a). He then pushes the pin point button 2318 and CONDENSER button 2337 on the front panel (FIG. 17a). If a leakage test is desired, the operator also must push the HIGH VOLTAGE button 2339. This is a safety feature which warns the operator that a high voltage is placed on leads 162, 163 during the leakage test. The operator also moves switch 2304 to the history position. The data processor then displays the format shown in FIG. 44 on CRT face 192.

Under the heading "CAP MFD", the capacitance value of the test condenser is displayed in microfarads in the positions occupied by the x's. The current value is displayed in row 5 and periodic readings of the value are displayed on a historical basis from time-to-time in rows 7-15 opposite the letters A-I. Under the heading "LEAK", the data processor indicates the condition of the test condenser by displaying the words "GOOD" or "BAD" in the positions occupied by the y's (FIG. 44). The condition word displayed depends on the amount of leakage current flowing through the test condenser. The current condition is displayed in row 5, and the historical condition, based on measurements taken periodically, is displayed in rows 7-15 opposite the letters A-I.

The capacitance of the condenser in microfarads and the conditions of the condenser are determined by the data processor based on the program segment illustrated in the flowchart of FIG. 45. Step S260 results in the format shown in FIG. 44. In step S261, the coordinate of the row and column of the first number displayed under the "CAP MFD" heading is stored for convenient access. In step S262, the letter I, which represents the row number, is set equal to 1. (1 corresponds to the first row of the history display, i.e., row 7 shown in FIG. 44.) Step S263 determines whether a data display is requested by examining the state of the DELTA FLAG is determined by issuing an INPUT STATUS REGISTER INPUT COMMAND. The data display ca be requested in one of two ways:

(1) If switch 2455 is set to its automatic position (FIG. 17a), the DELTA FLAG is set to 1 at a time interval adjustable from about 0.2 to 8 seconds.

(2) If switch 2455 is in the command position, a data display request which takes a reading, makes a calculation and displays a value or condition opposite one of the letters A-I is only made when the ENTER button is depressed or the remote control button 2551 is depressed.

As soon as a data display request is received, the value of the condenser capacitance is calculated by the data processor using ohmeter-capacitance circuit 750, current source circuit 830, and analog control system 1100. The manner in which capacitance is read is described in connection with Tables 1-6 and FIG. 20. After the capacitance value is measured and calculated, it is displayed on current value row 5. If it is decided in step S266 that more history rows can be displayed on CRT screen 192, the capacitance value measured in step S265 is also displayed on history row I. In the present example in which I = 1, the value is displayed in row 7 opposite the letter A.

If it is determined that a leakage test is required in step S268, the row and column display coordinates are incremented to the leakage position below the lable "LEAK". The data processor then delays for six seconds while the test condenser is charging up. (In step S270, X = 6). The condenser leakage current is then measured and computed. In order to perform the leak test, the data processor switches leakage line 1143 (FIG. 12a) to its 1 state so that relays K10-K12 switch their corresponding contacts to a condition opposite the one shown in FIG. 11a. As a result, high voltage is conducted to the condenser over conductors 162, 163. Any leakage current flowing through the condenser results in a voltage across resistor 964 (FIG. 11a) which is conducted over conductors 162a, 163 to the circuitry shown in FIG. 9. The voltage is amplified in circuit 702 and is further operated on by circuits 752, 753 (FIG. 10) to produce a voltage on leakage conductor 823 which is proportional to the value of the leakage current flowing through resistor 964 (FIG. 11a). This voltage is converted to a digital number by analog control system 1100 in the manner described in the flow chart of FIG. 20.

If the resultant digital number indicates a leakage current above a predetermined number of microamperes, the word "BAD" is displayed in row 5 (step S274, FIG. 45). If the value of the digital number obtained from analog control system 1100 indicates a leakage current equal to or below the predetermined number of microamps (i.e., K microamps), the term "GOOD" is displayed in row 5. If it is determined in step S275 that more history rows can be displayed, the GOOD or BAD condition is displayed in history row I. In this case, since I is set equal to 1, the appropriate word is displayed in row 7 opposite the letter A.

The data processor then switches leakage conductor 1143 (FIG. 12a) to its 0 state so that the relay contacts described in FIG. 11a are switched to the states shown in FIG. 11a. As soon as the relay contacts are switched, the high voltage is removed from leads 162, 163, and the data processor delays for 1.0 second so that the test condenser can discharge. (In step S277, Y = 1.0). If more history rows can be displayed as determined in step S278, the I value is incremented by 1, and the row and column display coordinates are again set to display the values under the "CAP MFD" heading. control is then transferred to the executive routines in step S281.

If the executive routines indicate that the capacitance test is still desired, the subroutine is entered at step B (FIG. 45), and the capacitance and leakage tests are repeated for the next display row 8 opposite the letter B when the period of time set by refresh rate switch 2455 has elasped (or when an ENTER command is received).

Each time a new value is entered in one of the history rows 7-15, the same value is also entered in the current value row 5. Moreover, after all of the history rows 7-15 have been filled, the current value row 5 continues to be refreshed with new data at the rate determined by the setting of refresh rate switch 2455. The subroutine is repeated if the PROCEED button is pushed.

The history mode of operation of the pin point test is an important feature which enables the operator to determine the manner in which parameter values change as a function of time. As a result, the condition of engine parameters which change as a function of time may be determined with a degree of accuracy heretofore unattainable.

EXECUTABLE BINARY CODE LISTING

Although the foregoing description of the preferred embodiment will enable a person of ordinary skill in the art to make and use the same, the following detailed binary code listing for data processor 1090 is included to provide detailed information concerning the programming and operation of the overall system. Additional detailed features of the system will become apparent to those skilled in the art from reviewing the program listing. The listing is given in hexadecimal code. The left-hand column is the memory location in memory 1094 in hexadecimal code, and the right-hand column is either instructions or data in hexadecimal code. This code can be used on a National SemiConductor Microprocessor Model IMP-16c. ##SPC1## ##SPC2## ##SPC3## ##SPC4## ##SPC5##

Those skilled in the art will recognize that only a single preferred embodiment has been disclosed, and that the preferred embodiment can be modified without departing from the spirit and scope of the invention. For example, the invention can be used in connection with a diesel type engine in which each firing chamber is fitted with an ignitor which comprises a fuel injector. In such a system, the firing pulse which actuates or fires the ignitor comprises a pressure wave inside a fuel line connected to an injector. A mechanical or electrical switch creates pressure in the fuel line or opens the injectors sequentially in order to inject fuel into the proper firing chamber at the proper time. The pressure wave or firing pulse created as the fuel is injected can be used as a source of timing pulses in the same manner as the ignition signals of a conventional gasoline-powered internal combustion engine which uses spark plugs.

Claims

What is claimed is:

1. Improved apparatus for measuring the dwell of an ignition system of an internal combustion engine having a predetermined number of cylinders and fuel ignitors, said ignition system comprising a switch periodically opened and closed in synchronism with the rotation of the engine in order to create time-spaced ignition pulses for firing the ignitors, the switch being closed for a dwell time period and being open for a firing time period in order to create such ignition pulse, said apparatus comprising: clock means for producing clock pulses at a predetermined rate; first counter means for counting the clock pulses; second counter means for counting the clock pulses; first gate means for transmitting clock pulses to the first counter means in response to a first one of the ignition pulses and for preventing the transmission of clock pulses to the first counter means in response to a second one of the ignition pulses; second gate means for transmitting clock pulses to the second counter means only during the duration of one or more dwell time periods which occur between the first ignition pulse and the second ignition pulse; processor means for producing a digital dwell signal having a value proportional to the count of the second counter means divided by the count of the first counter means; and display means for displaying a swell number having a value proportional to the value of the dwell signal.

2. Apparatus, as claimed in claim 1, and further comprising means for electrically coupling the first gate means to a single one of the ignitors, whereby the first one and second one of the ignition pulses are successive ignition pulses transmitted to said single one of the ignitors.

3. Apparatus, as claimed in claim 2, wherein the second gate means comprises means for transmitting clock pulses to the second counter means during only a single dwell time period which occurs between the first and second ignition pulses and wherein the apparatus further comprises means for selecting the dwell time period during which the clock pulses are transmitted to the second counter means, whereby the dwell number associated with a preselected ignitor is displayed on the display means.

4. Apparatus, as claimed in claim 2, wherein the second gate means comprises means for transmitting clock pulses to the second counter means during each dwell time period occurring between the first ignition pulse and the second ignition pulse, whereby the dwell number displayed on the display means represents the averge dwell time of the ignition system.

5. Apparatus, as claimed in claim 4, wherein the processor means further comprises means for dividing the count of the second counter means by the predetermined number of chambers.

6. Apparatus, as claimed in claim 1, wherein the processor means comprises a digital computer.

7. Apparatus, as claimed in claim 1, wherein the display means comprises: a character generator; and a cathode ray tube monitor.

8. Improved apparatus for measuring the timing of a chamber of an internal combustion engine having a predetermined number of chambers and including an ignition system having fuel ignitors, said ignition system comprising a switch periodically opened and closed in synchronism with the rotation of the engine in order to create time-spaced ignition pulses for firing the ignitors, the time duration between successive closures of the switch defining a chamber timing period, said apparatus comprising: clock means for producing clock pulses at a predetermined rate; first counter means for counting the clock pulses; second counter means for counting the clock pulses; first gate means for transmitting clock pulses to the first counter means in response to a first one of the ignition pulses and for preventing the transmission of clock pulses to the first counter means in response to a second one of the ignition pulses; second gate means for transmitting clock pulses to the second counter means only during one or more selected chamber timing periods which occur between the first ignition pulse and the second ignition pulse; means for modifying the one or more selected chamber timing periods during which clock pulses are transmitted to the second counter means; processor means for producing a digital chamber timing signal having a value proportional to the count of the second counter means divided by the count of the first counter means; and display means for displaying a chamber timing number having a value proportional to the value of the chamber timing signal, whereby the chamber timing number displayed on the display means is associated with one or more preselected chambers and ignitors.

9. Apparatus, as claimed in claim 8, and further comprising means for electrically coupling the first gate means to a single one of the ignitors, whereby the first one and second one of the ignition pulses are successive ignition pulses transmitted to said single one of the ignitors.

10. Apparatus, as claimed in claim 9, wherein the processor means comprises means for individually selecting each of the chamber timing periods within an engine cycle and for summing the individual resulting counts of the second counter means, whereby the chamber timing number displayed on the display means represents the average chamber timing of the ignition system.

11. Apparatus, as claimed in claim 10, wherein the processor means comprises means for dividing the summed individual counts of the second counter means by the predetermined number of chambers.

12. Apparatus, as claimed in claim 8, wherein the processor means comprises a digital computer.

13. Apparatus, as claimed in claim 8, wherein the display means comprises: a character generator; and a cathode ray tube monitor.

14. Apparatus for analyzing an internal combustion engine comprising: means coupled to the engine for generating a digital measurement signal corresponding to a predetermined engine condition; display means having a face for displaying at a first location on the face a first character group of alphabetic letters indicative of the unit in which the predetermined engine condition is measured and for displaying at a second location on the face a first number indicative of the value of the engine condition being measured; memory means for storing a first character code signal corresponding to the first character group, a first display address signal corresponding to the first location, and a second display address signal corresponding to the second location; display controller means for enabling the display means to display the first character group at the first location in response to the first character code signal and the first display address signal and for enabling the display means to display the first number at the second location in response to the second display address signal and a first digital display signal corresponding to the value of said engine condition in the units indicated by the first character group; and processor means for altering the value of the digital measurement signal to produce the first digital display signal, transmitting the first digital display signal and second display address signal to the display controller means and for transmitting the first character code signal and first display address signal to the display controller means, at least said first digital display signal being produced and transmitted to the display controller means in less than 8 seconds from the time the engine condition occurs, whereby the units and value of the engine condition are displayed in digital form on the face of the display means in real time, so that an operator of the apparatus can determine the value of the engine condition as the engine is operating.

15. Apparatus, as claimed in claim 14, wherein the means coupled to the engine for generating comprises: analog measuring means for generating an analog measuring signal corresponding to the engine condition being measured; and converter means for converting the analog measuring signal to the digital measurement signal.

16. Apparatus, as claimed in claim 14, wherein the memory means comprises a digital read-only memory for storing an application control program.

17. Apparatus, as claimed in claim 14, wherein the processor means comprises: an arithmetic unit; a control unit; means for transmitting data from the memory means to the display controller means; and means for enabling the temporary storage of the first digital display signal before transmitting the first digital display signal to the display controller means.

18. Apparatus, as claimed in claim 14, wherein the display controller means comprises a buffer memory for storing the first character code signal while the first character group is displayed on the face of the display means.

19. Apparatus, as claimed in claim 14, wherein the display means comprises a cathode ray tube.

20. Apparatus, as claimed in claim 19, wherein the cathode ray tube comprises an electron gun for scanning the face with a predetermined number of scan lines at a predetermined rate, and wherein the display controller means comprises: clock means for generating clock pulses at a predetermined rate; row counter means for counting clock pulses so that each scan is divided into a predetermined number of rows; and line counter means for counting the scans so that the face of the cathode ray tube means is divided into a predetermined number of lines for displaying characters.

21. Apparatus, as claimed in claim 14, and further comprising panel switch means for selecting the type of engine condition to be displayed, wherein the processor means comprises means for periodically interrogating the panel switch means independent of the selection state of the panel switch means, whereby a change in the type of engine condition selected on the panel switch means results in a substantially instantaneous change of the unit and value displayed on the display means.

22. Apparatus, as claimed in claim 21, wherein the processor means comprises executive means for interrogating the panel switch means before the first digital display signal and second display address signal are transmitted to the display controller means.

23. Apparatus, as claimed in claim 14, wherein the processor means comprises means for transmitting the first character code signal and the first display address signal in parallel form to the display controller means, whereby the display of engine parameters in real time is facilitated.

24. Apparatus, as claimed in claim 23, wherein the first character code signal and the first display address signal are transmitted to the display controller means in a single word.

25. Apparatus, as claimed in claim 14, wherein the memory means comprises means for storing an instruction signal corresponding to an alphabetic instruction to be displayed on the display means, wherein the processor means comprises means for transmitting the instruction signal to the display controller means, and wherein the display controller means comprises means for displaying the alphabetic instruction simultaneously with the first character group and the first number on the display means.

26. Apparatus for analyzing an internal combustion engine comprising: means coupled to the engine for generating a digital measurement signal corresponding to a predetermined engine condition; display means having a face for displaying at a first location on the face a first character group of alphabetic letters indicative of the unit in which the predetermined engine condition is measured, for displaying at a second location on the face a first number indicative of the value of the engine condition being measured at a first point in time, and for displaying at a third location on the face a second number indicative of the value of the engine condition being measured at a second point in time; memory means for storing a first character code signal corresponding to the first character group, a first display address signal corresponding to the first location, a second display address signal corresponding to the second location, and a third display address signal corresponding to the third location; display controller means for enabling the display means to display the first character group at the first location in response to the first character code signal and the first display address signal, for enabling the display means to display the first number at the second location in response to the second display address signal and a first digital display signal corresponding to the value of said engine condition in the units indicated by the first character group at the first point in time, and for enabling the display means to display the second number at the third location in response to the third display address signal and a second digital display signal corresponding to the value of said engine condition in the units indicated by the first character group at the second point in time; processor means for transmitting the first character code signal and first display address signal to the display controller means, operative in a first mode at the first point in time for altering the value of the digital measurement signal to produce the first digital display signal and for transmitting the first digital display signal and second display address signal to the display controller means, and operative in a second mode at the second point in time for altering the value of the digital measurement signal to produce the second digital display signal and for transmitting the second digital display signal and third display address signal to the display controller means; and selection means for operating the processor means in the first mode whereby the first number is displayed on the face of the display means so that the value of the engine condition at the first point in time can be observed, and for operating the processor means in the second mode whereby the second number is displayed on the face of the display means so that the value of the engine condition at the second point in time can be observed.

27. Apparatus, as claimed in claim 26, wherein the selection means comprises a transmitter located remotely from the processor means for selectively determining the operating mode of the processor means.

28. Apparatus, as claimed in claim 26, wherein the means coupled to the engine for generating comprises: analog measuring means for generating an analog measuring signal corresponding to the engine condition being measured; and converter means for converting the analog measuring signal to the digital measurement signal.

29. Apparatus, as claimed in claim 26, wherein the memory means comprises a digital memory.

30. Apparatus, as claimed in claim 26, wherein the processor means comprises: an arithmetic unit; a control unit; means for transmitting data from the memory means to the display controller means; and means for enabling the temporary storage of the first digital display signal before transmitting the first digital display signal to the display controller means.

31. Apparatus, as claimed in claim 26, wherein the display controller means comprises a buffer memory for storing the first character code signal while the first character group is displayed on the face of the display means.

32. Apparatus, as claimed in claim 26, wherein the display means comprises a cathode ray tube.

33. Apparatus, as claimed in claim 31, wherein the cathode ray tube comprises an electron gun for scanning the face with a predetermined number of scan lines at a predetermined rate, and wherein the display controller means comprises: clock means for generating clock pulses at a predetermined rate; row counter means for counting clock pulses so that each scan is divided into a predetermined number of rows; and line counter means for counting the scans so that the face of the cathode ray tube is divided into a predetermined number of lines for displaying characters.

34. Apparatus, as claimed in claim 26, wherein the memory means comprises means for storing an instruction signal corresponding to an alphabetic instruction to be displayed on the display means, wherein the processor means comprises means for transmitting the instruction signal to the display controller means, and wherein the display controller means comprises means for displaying the alphabetic instruction simultaneously with the first character group, the first number and the second number on the display means.

35. Apparatus for automatically analyzing an internal combustion engine during a first operating state and a second operating state comprising: means coupled to the engine for generating first and second digital measurement signals corresponding to first and second engine conditions, respectively, which are useful for analyzing the first operating state and for generating third and fourth digital measurement signals corresponding to third and fourth engine conditions, respectively, which are useful for analyzing the second operating state; display means having a face for displaying simultaneously during a first time period first and second numbers corresponding to the first and second digital measurement signals, respectively, a first character group of alphabetical letters indicative of the units of the first number and a second character group of alphabetical letters indicative of the units of the second number, and for displaying simultaneously during a second time period, third and fourth numbers corresponding to the third and fourth digital measurement signals, respectively, a third character group of alphabetical letters indicative of the units of the third number and a fourth character group of alphabetical letters indicative of the units of the fourth number; memory means for storing first character code signals corresponding to the first character group, second character code signals corresponding to the second character group, third character code signals corresponding to the third character group and fourth character code signals corresponding to the fourth character code group; display controller means for enabling the display means to display the first character code group in response to the first character code signals, to display the second character code group in response to the second character code signals, to display the third character code group in response to the third character code signals, to display the fourth chacter code group in response to the fourth character code signals, to display the first number in response to a first digital display signal corresponding to the value of the first engine condition in the units indicated by the first character code group, to display the second number in response to a second digital display signal corresponding to the value of the second engine condition in the units indicated by the second character group, to display the third number in response to a third digital display signal corresponding to the value of the third engine condition in the units indicated by the third character group, and to display the fourth number in response to a fourth digital display signal corresponding to the value of the fourth engine condition in the units indicated by the fourth character group; processor means for operating in a first mode during the first time period to alter the digital measurement signals to produce the first and second digital display signals, respectively, and to transmit the first and second digital display signals and the first and second character code signals to the display controller means so that the first and second numbers and the first and second character groups are displayed, and for operating in a second mode during the second time period to alter the value of the third and fourth digital measurement signals to produce the third and fourth digital display signals, respectively, and to transmit the third and fourth digital display signals and the third and fourth character control signals to the display controller means so that the third and fourth numbers and the third and fourth character groups are displayed; and selection means for enabling the processor means to operate in the first mode so that the first operating state of the engine can be analyzed by observing the first and second numbers on the face of the display means and for enabling the processor means to operate in the second mode so that the second operating state of the engine can be analyzed by observing the third and fourth numbers on the face of the display means.

36. Apparatus, as claimed in claim 35, wherein the means coupled to the engine for generating comprises: analog measuring means for generating an analog measuring signal corresponding to the engine condition being measured; and converter means for converting the analog measuring signal to the digital measurement signal.

37. Apparatus, as claimed in claim 35, wherein the memory means comprises a digital memory.

38. Apparatus, as claimed in claim 35, wherein the processor means comprises: an arithmetic unit; a control unit; means for transmitting data from the memory means to the display controller means; and means for enabling the temporary storage of the first digital display signal before transmitting the first digital display signal to the display controller means.

39. Apparatus, as claimed in claim 35, wherein the display controller means comprises a buffer memory for storing the first character code signal while the first character group is displayed on the face of the display means.

40. Apparatus, as claimed in claim 35, wherein the display means comprises a cathode ray tube.

41. Apparatus, as claimed in claim 40, wherein the cathode ray tube comprises an electron gun for scanning the face with a predetermined number of scan lines at a predetermined rate, and wherein the display controller means comprises: clock means for generating clock pulses at a predetermined rate; row counter means for counting clock pulses so that each scan is divided into a predetermined number of rows; and line counter means for counting the scans so that the face of the cathode ray tube means is divided into a predetermined number of lines for displaying characters.

42. Apparatus, as claimed in claim 35, wherein the memory means comprises means for storing character signals corresponding to a first alphabetic instruction and a second alphabetic instruction to be displayed on the display means, wherein the processor means comprise means for transmitting the character signals to the display controller means, and wherein the display controller means comprises means for displaying the first alphabetic instruction during the first time period and for displaying the second alphabetic instruction during the second time period.

43. Apparatus, as claimed in claim 35, wherein the processor means enables the storage of the first digital measurement signal in the memory means during the first time period, and uses the first and third digital measurement signals during the second time period in order to calculate a fifth digital display signal for display on the display means.

44. Apparatus, as claimed in claim 35, wherein the selection means comprises a transmitter located remotely from the processor means.

45. Apparatus for displaying a first engine condition associated with a first chamber of an internal combustion engine and for separately displaying a second engine condition associated with a second chamber of the internal combustion engine, said apparatus comprising: means coupled to the engine for generating a first digital measurement signal corresponding to the first engine condition and for generating a second digital measurement signal corresponding to the second engine condition; display means having a face for displaying at a first location on the face a first character group indicative of the unit in which the first and second engine conditions are measured, for displaying at a second location on the face a first number indicative of the value of the first engine condition and for displaying at a third location on the face a second number indicative of the value of the second engine condition; memory means for storing first character code signals corresponding to the first character group, a first display address signal corresponding to the first location, a second display address signal corresponding to the second location and a third display address signal corresponding to the third location; display controller means for enabling the display means to display the first character group at the first location in response to the first character code signals and the first display address signal, for enabling the display means to display the first number at the second location in response to the second display address signal and a first digital display signal corresponding to the value of said first engine condition in the units indicated by the first character group, for enabling the first display means to display the second number at the third location in response to the third display address signal and a second digital display signal corresponding to the value of said second engine condition in the units indicated by the first character group; and processor means for transmitting the first character code signals and first display address signal to the display controller means so that the first character group is displayed, for altering the value of the first and second digital measurement signals to produce the first and second digital display signals and transmitting the first and second digital display signals together with the second and third display address signals to the display controller means, whereby the first number and second number are simultaneously displayed on the face of the display means so that the value of the first and second engine conditions can be observed.

46. Apparatus, as claimed in claim 45, wherein the means coupled to the engine for generating comprises: analog measuring means for generating an analog measuring signal corresponding to the engine condition being measured; and converter means for converting the analog measuring signal to the digital measurement signal.

47. Apparatus, as claimed in claim 45, wherein the memory means comprises a digital read-only memory for storing an application control program.

48. Apparatus, as claimed in claim 45, wherein the processor means comprises: an arithmetic unit; a control unit; means for transmitting data from the memory means to the display controller means; and means for enabling the temporary storage of the first digital display signal before transmitting the first digital display signal to the display controller means.

49. Apparatus, as claimed in claim 45, wherein the display controller means comprises a buffer memory for storing the first character code signals while the first character group is displayed on the face of the display means.

50. Apparatus, as claimed in claim 45, wherein the display means comprises a cathode ray tube.

51. Apparatus, as claimed in claim 50, wherein the cathode ray tube comprises an electron gun for scanning the face with a predetermined number of scan lines at a predetermined rate, and wherein the display controller means comprises: clock means for generating clock pulses at a predetermined rate; row counter means for counting clock pulses so that each scan is divided into a predetermined number of rows; and line counter means for counting the scans so that the face of the cathode ray tube means is divided into a predetermined number of lines for displaying characters.

52. Apparatus, as claimed in claim 45, wherein the internal combustion engine comprises a first ignitor located adjacent the first chamber, a second ignitor located adjacent the second chamber, a switch periodically opened and closed in synchronism with the engine to create a first firing signal for activating the first ignitor and for creating a second firing signal for activating the second ignitor and wherein the means coupled to the engine further comprises: chamber selection means for producing a first chamber selection pulse during the creation of the first firing signal and for producing a second chamber selection pulse during the creation of the second firing signal; and means for producing the first digital measurement signal in response to the first chamber selection pulse and for producing the second digital measurement signal in response to the second chamber selection pulse.

53. Apparatus, as claimed in claim 52, wherein the chamber selection means comprises: register means for receiving from the processor means a first selection code corresponding to the first chamber or a second selection code corresponding to the second chamber; first counter means for counting the signals produced by the opening and closing of the switch and for producing a first counting state during the creation of the first firing signal and for producing a second counting state during the creation of the second firing signal; and comparator means for generating the first chamber selection pulse when the first selection code corresponds to a first counting state and for generating the second chamber selection pulse when the second chamber selection code corresponds to the second counting state.

54. Apparatus, as claimed in claim 45, and further comprising panel switch means for selecting the type of engine condition to be displayed, wherein the processor means comprises means for periodically interrogating the panel switch means independent of the selection state of the panel switch means, whereby a change in the type of engine condition selected on the panel switch means results in a substantially instantaneous change of the unit and values displayed on the display means.

55. Apparatus, as claimed in claim 54, wherein the processor means comprises executive means for interrogating the panel switch means before the first and second digital display signals and the first, second and third display address signals are transmitted to the display controller means.

56. Apparatus, as claimed in claim 45, wherein the processor means comprises means for transmitting the first character code signal and the first display address signal in parallel form to the display controller means, whereby the display of engine parameters in real time is facilitated.

57. Apparatus, as claimed in claim 56, wherein the first character code signal and the first display address signal are transmitted to the display controller means in a single word.

58. Apparatus, as claimed in claim 45, wherein the first character group comprises alphabetic letters.

59. Apparatus for determining and displaying the value of a predetermined parameter of an internal combustion engine having a plurality of chambers fitted with ignitors operated by a series of time-spaced firing signals, said apparatus comprising: means coupled to the engine for generating a digital measurement signal proportional to the value of the predetermined parameter; display means having a face for displaying at a first location a scale of numbers indicative of the predetermined parameter and for displaying a variable graphic image adjacent the scale; memory means for storing first character code signals corresponding to the scale of numbers and first number display address signals corresponding to the first location; display controller means for enabling the display means to display the scale of numbers at the first location in response to the first character code signals and the first number display address signals, and for producing a graphic image at a position adjacent the scale of numbers determined by the value of a digital display signal, so that the predetermined parameter is visually represented; and processor means for transmitting the first character code signals and first number display address signals to the display controller means so that the scale of numbers is displayed and for converting the digital measurement signal into a digital display signal and transmitting the digital signal to the display controller means so that the graphic image is displayed on the display means.

60. Apparatus, as claimed in claim 59, wherein the means coupled to the engine comprises: clock means for producing clock pulses at a predetermined rate; counter means for counting the clock pulses; and gate means for transmitting the clock pulses to the counter means in response to a first one of the firing signals and for preventing clock pulses from being transmitted to the counter means in response to a second one of the firing pulses in order to form the digital measurement signal in the counter means.

61. Apparatus, as claimed in claim 60, wherein the processor means comprises means for computing the digital display signal from the digital measurement signal by inverting the digital measurement signal.

62. Apparatus, as claimed in claim 60, wherein the gate means is responsive only to the firing pulse transmitted to a single one of the ignitors.

63. Apparatus, as claimed in claim 62, wherein the first firing signal occurs at the beginning of one engine cycle and the second firing signal occurs at the beginning of the next subsequent engine cycle.

64. Apparatus, as claimed in claim 59, wherein the processor means comprises means for dividing a constant by the number of pulses counted by the counter means.

65. Apparatus, as claimed in claim 59, wherein the means coupled to the engine comprises means for generating a digital measurement signal proportional to the speed of the engine, whereby the speed of the engine is visually represented.

66. Apparatus, as claimed in claim 59, wherein the display means comprises a cathode ray tube.

67. Apparatus, as claimed in claim 66, wherein the cathode ray tube comprises: an electron gun for striking the face of the tube with an electron beam in response to the graphic signal; and scanning means for scanning the beam across the face in a series of parallel lines, each line being scanned during a predetermined time period.

68. Apparatus, as claimed in claim 67, wherein the display controller means comprises: first latch means for storing a row number signal corresponding to the row on the face at which the graphic image is to be produced; first counter means for counting the number of rows scanned by the scanning means, and for producing a first start signal in the row indicated by the row number signal; second counter means for counting the number of lines scanned by the scanning means within the row indicated by the row number and for producing a second start signal in a predetermined line; means for receiving clock pulses at a predetermined rate; second latch means for storing the digital display signal; third counter means for generating a stop signal after the receipt of a predetermined number of clock pulses proportional to the value of the digital display signal; means for resetting the third counter means at the beginning of each scan line; and means responsive to the first and second counter means for generating the graphic signal in response to the first and second start signals and terminating the graphic signal in response to the stop signal, whereby the cathode ray tube generates a visible line having a length proportional to the value of the predetermined parameter.

69. Apparatus, as claimed in claim 68, wherein the memory means comprises means for storing the row number signal.

70. Apparatus for measuring and displaying a parameter useful for diagnosing an internal combustion engine comprising: transducer means for generating a digital calibration signal corresponding to the ambient value of the parameter adjacent the engine during a first time period and for generating a digital measurement signal corresponding to the value of the parameter produced by the engine as well as the ambient value of the parameter during a second time period; display means including a face for displaying a digital measurement number indicative of the value of the parameter produced only by the engine; memory means for storing the digital calibration signal; processor means for combining the digital calibration signal and the digital measurement signal to produce a digital calculated signal having a value which eliminates the effect of the ambient value of the parameter on the digital measurement signal; and display controller means for enabling the display means to display the digital measurement number in response to the digital calculated signal.

71. Apparatus, as claimed in claim 70, wherein the transducer means comprises: analog measuring means for generating an analog measuring signal corresponding to the parameter being measured; and converter means for converting the analog measuring signal to a digital signal.

72. Apparatus, as claimed in claim 70, wherein the parameter is amperes.

73. Apparatus, as claimed in claim 70, wherein the memory means comprises a digital read-only memory for storing an application control program.

74. Apparatus, as claimed in claim 70, wherein the processor means comprises: an arithmetic unit; a control unit; and means for transmitting data among the processor means, memory means, transducer means and display controller means.

75. Apparatus, as claimed in claim 74, wherein the arithmetic unit comprises means for subtracting the digital calibration signal from the digital measurement signal.

76. Apparatus, as claimed in claim 70, wherein the display means comprises a cathode ray tube.

77. Apparatus, as claimed in claim 76, wherein the display controller means comprises a character generator.

78. Apparatus, as claimed in claim 70, and further comprising panel switch means for selecting the engine parameter to be displayed, wherein the processor means comprises means for periodically interrogating the panel switch means independent of the selection state of the panel switch means, whereby a change in the engine parameter selected on the panel switch means results in a substantially instantaneous change of the measurement number displayed on the display means.

79. Apparatus, as claimed in claim 78, wherein the processor means comprises executive means for interrogating the panel switch means before the digital calculated signal is transmitted to the display controller means.

80. Apparatus for measuring and displaying a parameter useful for diagnosing an internal combustion engine comprising: transducer means coupled to the engine for generating a digital measurement signal corresponding to the value of the parameter produced by the engine; display means including a face for displaying a digital measurement number indicative of the value of the parameter produced by the engine if the digital measurement number is within a predetermined range of values and for displaying a symbol if the digital measurement signal is outside the predetermined range of values; memory means for storing range signals indicative of the range of values of the digital measurement number acceptable for display on the display means; processor means for comparing the digital measurement signal with the range signals, for producing the error signal if the value of the digital measurement signal is outside the predetermined range of values indicated by the range signals, and for producing a digital display signal corresponding to the value of the digital measurement signal is within the predetermined range of values indicated by the range signals; and display controller means for enabling the display means to display the digital measurement number in response to the digital display signal and for enabling the display means to display the symbol in response to the error signal.

81. Apparatus, as claimed in claim 80, wherein the transducer means comprises: analog measuring means for generating an analog measuring signal corresponding to the parameter being measured; and converter means for converting the analog measuring signal to the digital measurement signal.

82. Apparatus, as claimed in claim 81, wherein the parameter is current.

83. Apparatus, as claimed in claim 81, wherein the parameter is resistance.

84. Apparatus, as claimed in claim 80, wherein the memory means comprises a digital read-only memory for storing an application control program.

85. Apparatus, as claimed in claim 80, wherein the processor means comprises: an arithmetic unit; a control unit; and means for transmitting data among the processor means, memory means, transducer means and display controller means.

86. Apparatus, as claimed in claim 80, wherein the display means comprises a cathode ray tube.

87. Apparatus, as claimed in claim 86, wherein the display controller means comprises a character generator.

88. Apparatus, as claimed in claim 80, and further comprising panel switch means for selecting the engine parameter to be displayed, wherein the processor means comprises means for periodically interrogating the panel switch means independent of the selection state of the panel switch means, whereby a change in the engine parameter selected on the panel switch means results in a substantially instantaneous change of the digital measurement number displayed on the display means.

89. Apparatus, as claimed in claim 88, wherein the processor means comprises executive means for interrogating the panel switch means before the digital display signal is transmitted to the display controller means.

90. Apparatus for automatically determining the relative power produced by at least the first and second chambers of an internal combustion engine, the first and second chambers being fitted with first and second ignitors fired by time-spaced firing signals generated by the engine, said apparatus comprising: disabling means for preventing a firing signal from being transmitted to the first ignitor in response to a first disable signal and for preventing a firing signal from being transmitted to the second ignitor in response to a second disable signal; speed detection means for generating a digital base speed signal having a value proportional to the base speed of the engine when the first or second ignitors are enabled to receive firing signals, for generating a first digital disabled speed signal proportional to the first disabled speed of the engine when the first ignitor is prevented from receiving firing signals and for generating a second digital disabled speed signal having a value proportional to the second disabled speed of the engine when the second ignitor is prevented from receiving firing signals; memory means for storing the digital base speed signal in response to a store signal; display means for displaying a first speed change number indicating the difference between the speed of the engine when both first and second ignitors are enabled and when the first ignitor is prevented from receiving firing signals and for displaying a second speed change number indicating the difference between the speed of the engine when both first and second ignitors are enabled and when the second ignitor is prevented from receiving firing signals; display controller means for enabling the display means to display the first speed change number in response to a first speed change signal and for enabling the display means to display the second speed change number in response to a second speed change signal; and processor means for enabling the production of the first disabled speed signal at a first point in time and for calculating the first speed change number in response to the digital base speed signal and the first disabled speed signal, whereby the first speed change number is displayed, and for enabling the production of the second disabled speed signal at a second point in time and for calculating the second speed change number in response to the digital base speed signal and the second disabled speed signal, whereby the second speed change number is displayed.

91. Apparatus, as claimed in claim 90, wherein the processor means comprises means for sampling the digital base speed signal over a first predetermined number of engine revolutions and for averaging the values of the sampled digital base speed signals, whereby the average base speed of the engine over the first predetermined number of engine revolutions is used to calculate the first and second speed change numbers.

92. Apparatus, as claimed in claim 91, wherein the processor means further comprises: means for sampling the first digital disabled speed signal over a second predetermined number of engine revolutions and for averaging the values of the sampled first digital disabled speed signals, whereby the average first disabled speed of the engine over the second predetermined number of engine revolutions is used to calculate the first speed change number; and means for sampling the second digital disabled speed signal over a third predetermined number of engine revolutions and for averaging the values of the sampled second digital disabled speed signals, whereby the average second disabled speed of the engine over the third predetermined number of engine revolutions is used to calculate the second speed change number.

93. Apparatus, as claimed in claim 92, wherein the speed detection means comprises: clock means for producing clock pulses at a predetermined rate; a counter means for counting clock pulses; and gate means for transmitting clock pulses to the counter means in response to a first one of the firing pulses and for inhibiting clock pulses from being transmitted to the counter means in response to a second one of the firing pulses.

94. Apparatus, as claimed in claim 92, wherein the processor means comprises an arithmetic unit and a control unit.

95. Apparatus, as claimed in claim 90, wherein the memory means comprises a digital, read-write memory.

96. Apparatus, as claimed in claim 90, wherein the display means comprises a cathode ray tube.

97. Apparatus, as claimed in claim 90, wherein the digital base speed signal has a value proportional to the average base speed of the engine when the first and second ignitors are enabled to receive firing signals.

98. Apparatus for measuring and displaying a parameter of an internal combustion engine which is capable of varying over a first and second range of values, said apparatus comprising: analog measuring means operable with a first degree of sensitivity for generating a first analog measuring signal having a first value proportional to the parameter and operable with a second degree of sensitivity for generating a second analog measuring signal having a value proportional to the parameter times a scale factor; converter means for converting the first analog measuring signal to a first digital measurement signal and for converting the second analog measuring signal to a second digital measurement signal; display means having a face for displaying at a first location on the face a first character group indicative of the units in which the parameter is measured and for displaying at a second location on the face a first number indicative of the value of the parameter in the first range and a second number indicative of the value of the parameter in the second range; display controller means for enabling the display means to display the first number at the second location in response to a first digital display signal and to display the second number at the second location in response to a second digital display signal; memory means for storing a scale factor signal corresponding to the scale factor; and processor means for operating the analog measuring means with the first degree of sensitivity when the parameter is within the first range of values so that the first digital measurement signal is produced and for converting the first digital measurement signal into the first conversion signal to form the first digital display signal whereby the first number is displayed, and for operating the analog measuring means with the second degree of sensitivity when the parameter is within the second range of values so that the second digital measurement signal is produced and for combining the second digital measurement signal with the scale factor signal to form the second digital display signal whereby the second number is displayed.

99. Apparatus, as claimed in claim 98, wherein the memory means comprises means for storing a range digital signal having a value between the first range of values and the second range of values, and wherein the processor means comprises means for comparing the range digital signal with the first digital measurement signal to determine whether the parameter lies within the first or second range of values.

100. Apparatus, as claimed in claim 99, wherein: the analog measuring means and converter means comprise an amplifier including means for adjusting the gain of the amplifier to a first level in response to a first adjustment signal and capable of adjusting the gain of the amplifier to a second level in response to a second adjustment signal; and the processor means comprises means for generating the first adjustment signal when the parameter is within the first range of values and for generating the second adjustment signal when the parameter is within the second range of values.

101. Apparatus, as claimed in claim 100, wherein the memory means further comprises a digital memory.

102. Apparatus, as claimed in claim 101, wherein the display means comprises a cathode ray tube.

103. Apparatus, as claimed in claim 102, wherein the processor means comprises an arithmetic unit for multiplying the value of second digital measurement signal times the value of the scale factor signal to form the second digital display signal.

104. Apparatus for measuring and displaying the maximum value of a parameter of an internal combustion engine which varies in value comprising in combination: means for generating during a predetermined time period a series of time-spaced digital measurement signals having values corresponding to the values of the parameter as it varies; memory means for storing at any one instant in time the measurement signal having the largest value of all the measurement signals generated during the predetermined time period; processor means for repetitively comparing the value of the stored measurement signal with the value of a subsequently-generated measurement signal and for storing the subsequently-generated measurement signal in place of the stored measurement signal in the memory means if the value of the subsequently-generated measurement signal is greater than the value of the stored measurement signal; and display means for displaying a number corresponding to the value of the measurement signal remaining in the memory means at the end of the predetermined time period, whereby the maximum value of the parameter occurring during the predetermined time period is displayed.

105. Apparatus, as claimed in claim 104, wherein the parameter is current.

106. Apparatus, as claimed in claim 104, wherein the processor means comprises a digital computer.

107. Apparatus, as claimed in claim 104, wherein the display means comprises: a character generator; and a cathode ray tube monitor.

108. Apparatus, as claimed in claim 104, wherein the engine comprises an ignition system including a high voltage secondary coil for generating secondary ignition signals and wherein the parameter comprises the secondary ignition signal voltage.

109. Apparatus, as claimed in claim 108, wherein the means for generating comprises: means for generating a threshold signal in response to the rising of the secondary ignition signal voltage above a predetermined threshold level; means for generating a cross-over signal in response to a decrease in said secondary ignition signal voltage after said voltage has attained the maximum value; a storage capacitor; and gate means responsive to the threshold and cross-over signals for enabling the storage capacitor to charge to a storage voltage proportional to the secondary ignition signal voltage, for generating a sample signal indicating that the storage voltage is available for sampling and for thereafter discharging the storage capacitor.

110. Apparatus, as claimed in claim 104, wherein the predetermined time period is no greater than the time required for one revolution of said engine.

111. Apparatus for measuring and displaying the minimum value of a parameter of an internal combustion engine which varies in value comprising in combination: means for generating during a predetermined time period a series of time-spaced digital measurement signals having values corresponding to the values of the parameter as it varies; memory means for storing at any one instant in time the measurement signal having the smallest value of all the measurement signals generated during the predetermined time period; processor means for repetitively comparing the value of the stored measurement signal with the value of one or more subsequently-generated measurement signals and for storing the subsequently-generated measurement signal in place of the stored measurement signal in the memory means if the value of the subsequently-generated measurement signal is less than the value of the stored measurement signal; and display means for displaying a number corresponding to the value of the measurement signal remaining in the memory means at the end of the predetermined time period, whereby the minimum value of the parameter occurring during the predetermined time period is displayed.

112. Apparatus, as claimed in claim 111, wherein the processor means comprises a digital computer.

113. Apparatus, as claimed in claim 111, wherein the engine comprises an ignition system including a high voltage secondary coil for generating secondary ignition signals and wherein the parameter comprises the secondary ignition signal voltage.

114. Apparatus, as claimed in claim 111, wherein the means for generating comprises: means for generating a threshold signal in response to the rising of the secondary ignition signal voltage above a predetermined threshold level; means for generating a cross-over signal in response to a decrease in said secondary ignition signal voltage after said voltage has attained the maximum value; a storage capacitor; and gate means responsive to the threshold and cross-over signals for enabling the storage capacitor to charge to a storage voltage proportional to the secondary ignition signal voltage, for generating a sample signal indicating that the storage voltage is available for sampling and for thereafter discharging the storage capacitor.

115. Apparatus, as claimed in claim 111, wherein the predetermined time period is no greater than the time required for one revolution of said engine.

116. Apparatus for determining the timing of an internal combustion engine having a plurality of chambers fitted with ignitors which are operated by a series of time-spaced firing pulses and having a timing mark which passes a timing location when the engine is located at a predetermined number of degrees prior to a top dead center position, said apparatus comprising: a register for storing the predetermined number of degrees; manually operable means for entering the predetermined number of degrees into the register; generator means for generating a timing pulse when the timing mark passes the timing location; clock means for producing clock pulses at a predetermined rate; a counter means for counting clock pulses; gate means for transmitting clock pulses to the counter means between the occurrence of a first and second one of the firing pulses to obtain a first count proportional to the time period between the first and second ignition pulses, and for transmitting clock pulses to the counter means between the occurrence of one of the firing pulses and the timing pulse to obtain a second count proportional to the time period between the last said firing pulse and the timing pulse; processor means for generating a timing number proportional to the second count divided by the first count plus the predetermined number of degrees; and display means for displaying a timing display number proportional to the timing number in digital form.

117. Apparatus, as claimed in claim 116, wherein the gate means is responsive only to the firing pulses transmitted to a single one of the ignitors.

118. Apparatus, as claimed in claim 116, wherein the first firing pulse occurs at the beginning of one engine cycle and the second firing pulse occurs at the beginning of the next subsequent engine cycle.

119. Apparatus, as claimed in claim 116, wherein the processor means comprises means for multiplying a constant times the quotient of the second count divided by the first count.

120. Apparatus, as claimed in claim 116, wherein the display means comprises: a character generator; and a cathode ray tube monitor.

121. Apparatus, as claimed in claim 116, wherein the manually-operable means comprises a keyboard capable of generating digital data.

122. Apparatus, as claimed in claim 116, wherein the processor means comprises means for determining whether the timing number exceeds a predetermined number of degrees, whereby the timing display number is displayed as degrees advance or as degrees retard.

123. Apparatus for measuring and displaying a parameter useful for diagnosing an internal combustion engine comprising: transducer means for generating a digital measurement signal corresponding to the value of the parameter produced by the engine; display means including a face for displaying a digital measurement number indicative of the value of the parameter; memory means for storing first and second linearization constants; processor means for multiplying the value of the digital measurement signal times the value of the first linearization constant to produce a first partial result signal, for multiplying a power of the value of the digital measurement signal times the value of the second linearization constant to produce a second partial result signal, and for summing the values of the first and second partial result signals in order to produce a digital calculated signal, whereby the value of the digital measurement signal is linearized; and display controller means for enabling the display means to display the digital measurement number in response to the digital calculated signal.

124. Apparatus, as claimed in claim 122, wherein the processor means comprises: an arithmetic unit; a control unit; and means for transmitting data among the processor means, memory means, transducer means and display controller means.

125. Apparatus, as claimed in claim 124, wherein the display means comprises a cathode ray tube.

126. Apparatus, as claimed in claim 124, wherein the transducer means comprises: analog measuring means for generating an analog measuring signal corresponding to the parameter being measured; and converter means for converting the analog measuring signal to the digital measurement signal.

127. Apparatus, as claimed in claim 124, wherein the parameter is the concentration of an exhaust emission from the engine.

128. Apparatus, as claimed in claim 124, wherein the memory means comprises a digital read-only memory for storing the first and second linearization constants.

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Abstract

Patent Drawings (74 sheets)