Magnetic rotational position sensor having dual magnetic flux sensor capabilities

[0002] This is a continuation-in-part and benefit is claimed under 35 U.S.C. § 120 based on U.S. patent application Ser. No. 09/074,946, filed May 8, 1998, now U.S. Pat. No. 6,137,288, the contents of which are hereby incorporated by reference.

[0003] The present invention generally relates to the field of rotational position sensors, and more specifically to a magnetic rotational position sensor for sensing each rotational position of a control shaft about an axis over a definable range of rotation.

[0004] Electronic fuel injected engines used in motor vehicles typically embody a microprocessor based control system. Fuel is metered or injector activation time is varied in accordance with various engine parameters including the regulation of air flow into the engine via a rotational position of a throttle diaphragm relative to a closed position of the throttle diaphragm. Typically, a shaft is adjoined to the throttle diaphragm to synchronously rotate the throttle diaphragm as the shaft is rotated between the closed position and a maximal open position of the throttle diaphragm. Rotational position sensors are adjoined to the shaft to sense each rotational position of the shaft, i.e. each degree of rotation of the shaft relative to the closed position, whereby the rotational position of the throttle diaphragm relative to the closed position is sensed.

[0005] One of the problems associated with the prior magnetic rotational position sensors is magnetic hysteresis. Magnetic hysteresis causes an offset error signal to be provided whenever a magnetic element of the sensor, e.g. a magnetic pole piece or a magnetic rotor, is advanced from and returned to a reference position of the magnetic element. Annealing the magnetic element can minimize, but never eliminate, magnetic hysteresis. What is therefore needed is a novel and unique magnetic rotational position sensor that does not experience magnetic hysteresis.

[0006] The present invention is a magnetic rotational position sensor that overcomes the aforementioned drawback associated with prior magnetic rotational position sensors. Various aspects of the present invention are novel, non-obvious, and provide various advantages. While the actual nature of the present invention described in detail herein can only be determined with reference to the claims appended hereto, certain features which are characteristic of the present invention disclosed herein can be described briefly.

[0007] One form of the present invention is a magnetic rotational position sensor comprising a ring pole piece defining an air gap area and a magnet disposed within the air gap area to thereby generate a magnetic field therein. The magnetic rotational position sensor further includes a first magnetic flux sensor and a second magnetic flux sensor disposed within the magnetic field. The magnetic flux sensors have coplanar surfaces.

[0008] Further forms, objects, features, aspects, benefits, advantages, and embodiments of the present invention shall become apparent from the detailed description and drawings provided herewith.

[0009] FIG. 1A is a first exploded view of a first embodiment of a magnetic rotational position sensor in accordance with the present invention.

[0010] FIG. 1B is a first perspective view of the magnetic rotational position sensor of FIG. 1A as assembled and adjoined to a control shaft.

[0011] FIG. 1C is a second exploded view of the magnetic rotational position sensor of FIG. 1A.

[0012] FIG. 1D is a second perspective view of the magnetic rotational position sensor of FIG. 1A as assembled and adjoined to a control shaft.

[0013] FIG. 2A is a first diagrammatic illustration of a first embodiment of a magnetic circuit of FIGS. 1A-1D.

[0014] FIG. 2B is a second diagrammatic illustration of the magnetic circuit of FIGS. 1A-1D.

[0015] FIG. 2C is a third diagrammatic illustration of the magnetic circuit of FIGS. 1A-1D.

[0016] FIG. 3A is a schematic of a preferred embodiment of a drive circuit in accordance with the present invention.

[0017] FIG. 3B is a graph depicting a waveform of a first provided voltage sensing signal and a waveform of a second provided voltage sensing signal of a preferred embodiment of the magnetic flux sensor of FIGS. 1A-1D.

[0018] FIG. 4 is a schematic of a preferred embodiment of an output signal amplifier in accordance with the present invention.

[0019] FIG. 5A is a diagrammatic illustration of a reference positioning of a magnetic flux sensor of a preferred embodiment of a magnetic rotational position sensor in accordance with the present invention as adjoined to a control shaft.

[0020] FIG. 5B is a diagrammatic illustration of a clockwise synchronous rotation of a magnetic circuit of the magnetic rotational position sensor of FIG. 5A.

[0021] FIG. 5C is a diagrammatic illustration of a counterclockwise synchronous rotation of the magnetic circuit of the magnetic rotational position sensor of FIG. 5A.

[0022] FIG. 6A is a first exploded view of a third embodiment of a magnetic rotational position sensor in accordance with the present invention.

[0023] FIG. 6B is a first perspective view of the magnetic rotational position sensor of FIG. 6A as assembled and adjoined to a control shaft.

[0024] FIG. 6C is a first longitudinal cross-sectional view of the magnetic rotational position sensor of FIG. 6A as assembled and adjoined to a control shaft.

[0025] FIG. 6D is a second longitudinal cross-sectional view of the magnetic rotational position sensor of FIG. 6A as assembled and adjoined to a control shaft.

[0026] For the purposes of promoting an understanding of the principles of the present invention, reference will now be made to the preferred embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the present invention is thereby intended, such alterations and further modifications in the illustrated embodiments and such further applications of the principles of the present invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the present invention relates. For purposes of the present invention, the term adjoined is broadly defined as an unitary fabrication, a permanent affixation, a detachable coupling, a continuous engagement, or a contiguous disposal as would occur to one skilled in the art.

[0027] The present invention is a novel and unique magnetic rotational position sensor that senses each degree of rotation of a control shaft about an axis over a definable range of rotation without experiencing magnetic hysteresis. For purposes of the present invention, a control shaft is broadly defined as any article of manufacture or any combination of manufactured articles that is adjoined to an object, e.g. a throttle diaphragm, a foot pedal, a piston, etc., to control the linear, angular, and/or rotational movement of the object as the control shaft is rotated about an axis, e.g. a longitudinal axis of the control shaft.

[0028] Referring to FIGS. 1A-1D, a first embodiment of a magnetic rotational position sensor 10 in accordance with the present invention is shown. Magnetic rotational position sensor 10 senses each degree of rotation of a control shaft 20 about an axis over a 180 degree range of rotation without experiencing magnetic hysteresis as further described in FIGS. 2A-2C and accompanying text.

[0029] Magnetic rotational position sensor 10 comprises a ring pole piece. For purposes of the present invention, a ring pole piece is broadly defined as any magnetizable article of manufacture or any combination of manufactured magnetizable articles that has an open configuration defining an air gap area. For the various embodiments of the present invention, the ring pole piece can vary in geometric size and shape, and can be made from any magnetizable material. Preferably, the ring pole piece is a soft magnetic steel ring pole piece 11 including a pole segment 11ahaving an arcuate configuration, a pole segment 11bhaving a rectangular configuration, and a pole segment 11chaving a rectangular configuration as shown in FIGS. 1A-1D. Pole segment 11ais adjoined to pole segment 11band pole segment 11c, and pole segment 11band pole segment 11care spaced to thereby define an air gap area 11d. Preferably, pole segment 11ais unitarily fabricated with pole segment 11band pole segment 11c.

[0030] Magnetic rotational position sensor 10 further comprises a magnet disposed within air gap area 11dto constitute a magnetic circuit that provides a magnetic field within air gap area 11dand encloses the magnetic field within ring pole piece 11 to prevent magnetic hysteresis. For the various embodiments of the present invention, one of the poles surfaces of the magnet is facing and spaced from pole segment 11awhile the other pole surface of the magnet if facing and spaced from pole segment 11band pole segment 11c, or preferably, one of the poles surfaces of the magnet is facing and spaced from pole segment 11awhile the other pole surface of the magnet is facing and adjoined to pole segment 11band/or pole segment 11c. Additionally, the magnet can vary in geometric size and shape, and can be any type of magnet. Preferably, the magnet is an injection molded rare earth magnet 12 having a substantially semi-circular configuration that is void of any magnetic flux density “hot spots” along both pole surfaces. Magnet 12 is disposed within air gap area 11dto constitute a magnetic circuit 13 as shown in FIGS. 1B and 1D. Magnet 12 has a north pole surface 12afacing and spaced from pole segment 13, and a south pole surface 12bfacing and adjoined to pole segment 11band pole segment 11cto thereby provide an equally balanced magnetic field 15 throughout air gap area 11dand to enclose magnetic field 15 within ring pole piece 11 as further described in FIGS. 2A-2C and accompanying text.

[0031] Ring pole piece 11 is adjoined to control shaft 20 to synchronously rotate magnetic field 15 about a second axis for each degree of rotation of control shaft 20 about a first axis, e.g. longitudinal axis 21 of control shaft 20, as further described in FIGS. 2A-2C and accompanying text. For the illustrated embodiment of the present invention, ring pole piece 11, magnet 12 and control shaft 20 are encapsulated in plastic to permanently affix south pole surface 12bto pole segment 11band pole segment 11c, and to permanently affix ring pole piece 11 and control shaft 20 via a plastic base 23 as shown in FIGS. 1B and 1D.

[0032] Magnetic rotational position sensor 10 further comprises a pair of magnetic flux sensors. For purposes of the present invention, a magnetic flux sensor is broadly defined as any device operable to sense a magnitude of a magnetic flux density passing through the device and operable to provide at least one voltage sensing signal representative of a magnitude of magnetic flux density passing through the device. For the illustrated embodiment of the present invention, the magnetic flux sensors are a Hall effect device 14 and Hall effect device 114, e.g. a HZ-302C(SIP type) Hall effect device manufactured by Ashai Kasei Electronics Co., Ltd., as shown in FIGS. 1A-1D. Hall effect device 14 has a first plane 14aand a secibd okabe 14b, and is operable to sense a magnitude of magnetic flux density passing through plane 14aand plane 14b. Hall effect device includes an input lead 14c, a reference lead 14d, a first output lead 14eand a second output lead 14f. In response to a current drive signal I_DSand a voltage drive signal V_DS, Hall effect device 14 is aldo operable to provide a first voltage sensing signal V_SS1and a second voltage sensing signal V_SS2. Both voltage sensing signals V_SS1and V_SS2are representative of a magnitude of magnetic flux density passing through planes 14aand 14b, repectively, as further described in FIG. 3B, and accompanying text.

[0033] Hall effect device 114 has a first plane 114ahas a first plane 114aand a second plane 114b, and is operable to sense a magnitude of magnetic flux density passing through plane 114aand plane 114b. Hall effect device includes an input lead 114c, a reference lead 114d, a first output lead 114eand a second output lead 114f. In response to a current drive signal I_DSand a voltage drive signal V_DS, Hall effect device 114 is also operable to provide first voltage sensing signal V_SS1and second voltage signal V_SS2. Plane 14aand plane 114aare coplanar whereby Hall effect device 14 and Hall effect device 114 are operable to simultaneously provide a pair of voltage sensing signals V_SS1as further described in FIG. 3B, and accompanying text. Plane 14bplane 114bare coplanar whereby Hall effect device 14 and Hall effect device 114 are operable to simultaneously provide a pair of voltage sensing signals V_SS2as further described in FIG. 3B, and accompanying text.

[0034] Referring to FIGS. 2A-2C, to sense each degree of rotation of control shaft 20 about an axis over a definable range of rotation, e.g. a 180 degree range of rotation about a longitudinal axis 21 of control shaft 20, a different magnitude of magnetic flux density must pass through planes 14aand 14bof magnetic flux sensor 14 for each degree of synchronized rotation of magnetic field 15 about a second axis, e.g. an axis 16, over the definable range of rotation. Consequently, an angular orientation angle θ of planes 14aand 14brelative to magnetic field 15 must change for each degree of synchronized rotation of magnetic field 15 about axis 16 over the definable range of rotation. Preferably, when magnetic flux sensor 14 is disposed along a center line 15aof magnetic field 15, planes 14aand 14bare parallel to magnetic field 15, i.e. an angular orientation angle θ of zero degrees, as shown in FIG. 2A. It is to be appreciated and understood that angular orientation angle θ relative to magnetic field 15 will change with each degree of synchronized rotation of magnetic field 15 about axis 16 over a ±ninety (90) degree range of synchronized rotation of magnetic field 15 relative to magnetic flux sensor 14 as evidenced by the synchronized rotational movement of a center point 17 of magnetic flux sensor 14 and a reference point 22 of control shaft 20 as shown in FIGS. 2B and 2C. Thus, it is to be appreciated and understood that each degree of rotation of control shaft 20 about longitudinal axis 21 over a 180 degree range of rotation can be sensed because each degree of rotation of control shaft 20 about longitudinal axis 21 exclusively corresponds to a distinct degree of synchronized rotation of magnetic field 15 about axis 16 and a different magnitude of magnetic flux density will pass through magnetic flux sensor 14 for each degree of synchronized rotation of magnetic field 15 about axis 16 over the 180 degree range of rotation.

[0035] To linearly sense each degree of rotation of control shaft 20 about longitudinal axis 21 over the 180 degree range of rotation, angular orientation angle θ must uniformly change for each degree of synchronized rotation of magnetic field 15 about axis 16. One aspect of the present invention is that for a each axis of magnetic field 15 that intersects center line 15a, angular orientation angle θ uniformly changes along one radial arc originating from the selected axis for each degree of synchronized rotation of magnetic field 15 about the selected axis over approximately an ±eighty (80) degree range of synchronized rotation of magnetic field 15. For example, angular orientation angle θ uniformly changes along a radial arc 18 originating from axis 16 for each degree of synchronized rotation of magnetic field 15 about axis 16 over approximately an ±eighty (80) degree range of synchronized rotation of magnetic field 15 relative to magnetic flux sensor 14. Thus, it is preferred that magnetic flux sensor 14 is initially disposed within magnetic field 15 along center line 15aof magnetic field 15 with planes 14aand 14bparallel to magnetic field 15 and center point 17 of magnetic flux sensor 14 being an intersection point of center line 15aof magnetic field 15 and radial arc 18.

[0036] Referring still to FIGS. 2A-2C, several important points must be appreciated and understood. First, for the various embodiments of the present invention, the axis of control shaft 20 may or may not coincide with a selected axis of a provided and enclosed magnetic field. Preferably, the axis of control shaft 20 does coincide with the selected axis of the magnetic field, e.g. longitudinal axis 21 of shaft 20 coinciding with axis 16 of magnetic field 15. Second, for the various embodiments of the present invention, the axis of the magnetic field may or may not coincide with a central longitudinal axis of the ring pole piece. Preferably, the axis of the magnetic field does not coincide with the central longitudinal axis of the ring pole piece, e.g. axis 16 of magnetic field 15 not coinciding with longitudinal axis 11eof ring pole piece 11 as shown.

[0037] Third, the relative dimensions of a ring pole piece in accordance with the present invention and of a magnet in accordance with the present invention defines the maximum synchronous range of rotation of a provided and enclosed magnetic field relative to a magnetic flux sensor. For example, the relative dimensions of ring pole piece 11 and magnet 12 as illustrated enable magnetic field 15 to be rotated at least 180 degrees relative to magnetic flux sensor 14. Finally, the symmetrical configurations of a ring pole piece in accordance with the present invention and of a magnet in accordance with the present invention that is void of magnetic flux density “hot spots” along both pole surfaces relative to a center line of a provided and enclosed magnetic field equally balances the magnetic field throughout the air gap area. For example, the symmetrical configurations of ring pole piece 11 and magnet 12 relative to center line 15aof magnetic field 15 equally balances magnetic field 15 throughout air gap area 11d.

[0038] As previously described in FIGS. 1A-1D and accompanying text, a current drive signal I_DSand a voltage drive signal V_DSneed to be supplied to Hall effect device 14 and Hall effect device 114 to thereby simultaneously provide the pair of voltage sensing signals V_SS1and the pair of voltage sensing signals V_SS2. For the various embodiments of the present invention, any power source supplying current drive signal I_DSand voltage drive signal V_DSto Hall effect device 14 and/or Hall effect device 114 may be exposed to adverse temperatures as low as −40° Celsius to as high as 150° Celsius when Hall effect device 14 and/or Hall effect device 114 are located in a engine compartment of a motor vehicle. As such, it is to be appreciated and understood that current drive signal I_DSand voltage drive signal V_DScan significantly fluctuate under such adverse temperature conditions. Accordingly, a preferred embodiment of a drive circuit 30 to invariably provide a constant current drive signal I_CDSand a constant voltage drive signal V_CDSover such adverse temperatures is shown in FIG. 3A.

[0039] Referring to FIG. 3A, drive circuit 30 comprises a voltage divider 31 operable to provide a reference voltage signal V_REF1in response to a power signal V_CC. Voltage divider 31 including a first resistor R1, a second resistor R2 and a third resistor R3 electrically coupled in series between a power supply terminal 50aand a ground reference terminal 50bof a power source (not shown) to thereby provide reference voltage signal V_REF1. Preferably, the power source transmits a power signal V_CCof 5.0 volts between power supply terminal 50aand ground reference terminal 50bwhereby reference voltage signal V_REF1is approximately 2.5 volts. For the illustrated embodiment, it is preferred that resistors R1 and R2 are of equal value and that resistor R3 is of a significantly less value, e.g. resistors R1 and R2 can be 10kohm resistors, and resistor R3 can be a trimable 1 k ohm resistor.

[0040] Drive circuit 30 further comprises a current amplifier 32 operable to provide and control constant current drive signal I_CDSand constant voltage drive signal V_CDSin response to power signal V_CCand a reference voltage signal V_REF1. Current amplifier 32 includes a first operational amplifier OP1, a first bipolar pnp transistor Q1, a fourth resistor R4, a fifth resistor R5, and a first capacitor C1. Operational amplifier OP1 has a non-inverting input electrically coupled to voltage divider 31 to receive a reference voltage signal V_REF1, and an inverting input electrically coupled to input lead 14cof Hall effect device 14. Transistor Q1 has an emitter lead electrically coupled to reference lead 14dof Hall effect device 14 and a collector lead electrically coupled to ground reference terminal 50b. Resistor R4 electrically couples power supply terminal 50ato input lead 14cof Hall effect device 14. Resistor R5 electrically couples a power output of operational amplifier OP1 to a base lead of transistor Q1. Capacitor C1 electrically couples the power output of operational amplifier OP1 to the inverting input of operational amplifier OP1.

[0041] Preferably, constant current drive signal I_CDSis 7.0 milliamperes ±10 microamperes and constant voltage drive signal V_CDSis approximately 4.2 volts. Accordingly, it is preferred that resistor R4 is a 150 ohm resistor, resistor R5 is a 470 ohm resistor, and capacitor C1 is a 0.01 microfarads capacitor. Drive circuit 30 can further comprise an optional second capacitor C2 electrically coupling power supply terminal 50aand ground reference terminal 50bto eliminate any noise from power signal V_CC. Preferably, capacitor C2 is a 0.1 microfarads capacitor.

[0042] Upon receipt of a constant current drive signal I_CDSand a constant voltage drive signal V_CDSvia input lead 14c, Hall effect device 14 provides voltage sensing signals V_SS1and V_SS2. Waveforms of provided voltage sensing signals V_SS1and V_SS2as related to angular orientation angle θ of Hall effect device 14 relative to magnetic field 15 are shown in FIG. 3B. Referring to FIGS. 2A-2C and 3B, it is to be appreciated and understood that each value of voltage sensing signals V_SS1and V_SS2along the waveforms exclusively corresponds to a distinct degree of rotation of control shaft 20 about an axis, e.g. longitudinal axis 21 of control shaft 20, over a 180 degree range of rotation. It is to be further appreciated and understood that voltage sensing signals V_SS1and V_SS2are linearly provided over approximately a middle 160 degrees of the 180 degree range of rotation. Unfortunately, voltage sensing signals V_SS1and V_SS2are high impedance loads that are typically not feasible as voltage output signals. Accordingly, a preferred embodiment of an output signal amplifier 40 is shown in FIG. 4.

[0043] Referring to FIG. 4, output signal amplifier 40 comprises a buffer amplifier 41 operable to buffer voltage sensing signals V_SS1and V_SS2and to counteract any temperature drift of voltage sensing signals V_SS1and/or V_SS2due to the ambient temperature of Hall effect device 14. Buffer amplifier 41 includes a second operational amplifier OP2, a third operational amplifier OP3, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, and a thermistor TR. Operational amplifier OP2 has a non-inverting input electrically coupled to output lead 14fof Hall effect device 14 to receive a provided voltage sensing signal V_SS1, and operational amplifier OP3 has a non-inverting input electrically coupled to output lead 14eof Hall effect device 14 to receive a provided voltage sensing signal V_SS2. Resistor R6 electrically couples a power output of operational amplifier OP2 to an inverting input of operational amplifier OP2. Resistor R7 electrically couples a power output of operational amplifier OP3 to an inverting input of operational amplifier OP3. Resistor R8 and resistor R9 in series electrically couple the inverting input of operational amplifier OP2 and the inverting input of operational amplifier OP3. Thermistor TR is electrically coupled in parallel to resistor R8. Preferably, resistors R6 and R7 are 10 k ohm resistors, and resistors R8 and R9 are 1 k ohm resistors.

[0044] Output signal amplifier 40 further comprises a voltage divider 42 operable to provide a reference voltage signal V_REF2in response to a power signal V_CC. Reference voltage signal V_REF2is provided to correct for any manufacturing anomalies of Hall effect device 14 as further described in FIG. 6A and accompanying text. Voltage divider 42 includes a tenth resistor R10, an eleventh resistor R11, a twelfth resistor R12, and a thirteenth resistor R13 electrically coupled in series to power supply terminal 50aand ground reference terminal 50b. Preferably, the power source transmits a power signal V_CCof 5.0 volts between power supply terminal 50aand ground reference terminal 50bwhereby reference voltage signal V_REF2is approximately 2.5 volts. For the illustrated embodiment, it is preferred that resistors R10 and R13 are of equal value and that resistors R11 and R12 are of a significantly less value, e.g. resistors R10 and R13 can be 10 k ohm resistors, and resistors R11 and R12 can be trimable 1 k ohm resistors. Voltage divider 42 further includes an operational amplifier OP5 having an non-inverting input electrically coupled to resistor R11 and resistor R12 to thereby receive reference voltage signal V_REF2, and an inverting input electrically coupled to a power output.

[0045] Output signal amplifier 40 further comprises a differential amplifier 43 operable to provide a voltage output signal V_OUTand a first current output signal I_OUT1in response to buffered voltage sensing signals V_SS1and V_SS2, and a reference voltage signal V_REF2. Differential amplifier 43 includes an operational amplifier OP4, a fourteenth resistor R14, a fifteenth resistor R15, a sixteenth resistor R16, and a third capacitor C3. Resistor R14 electrically couples the power output of operational amplifier OP2 to an inverting input of operational amplifier OP4. Resistor R15 electrically couples the power output of operational amplifier OP3 to a non-inverting input of operational amplifier OP4. Resistor R16 electrically couples the power output of operational amplifier OP5 to the noninverting input of operational amplifier OP4. Capacitor C3 electrically couples a power output of operational amplifier OP4 to the inverting input of operational amplifier OP4. It is to be appreciated that voltage output signal V_OUTis representative of each degree of rotation of a control shaft 20 about the first axis. Preferably, voltage output signal V_OUTranges between 0 volts and 5.0 volts over the 180 degree range of rotation of control shaft 20, and linearly ranges between 0.5 volts and 4.5 volts over a middle 160 degrees of the 180 degree range of rotation. Accordingly, it is preferred that resistor R14, resistor R15 and resistor R16 are 10 k ohm resistors, and capacitor C3 is a 0.1 microfarads capacitor.

[0046] For various embodiments of the present invention, output signal amplifier 40 can further comprises a boost circuit 44 to transmit voltage output signal V_OUTand to boost output current signal I_OUT1. Boost circuit 44 includes a first bipolar npn transistor Q2, a second bipolar pnp transistor Q3, a seventeenth resistor R17, an eighteenth resistor R18, a nineteenth resistor R19, a twentieth resistor R20, a twenty-first resistor R21, and a fourth capacitor C4. An emitter lead of transistor Q3 is electrically coupled to power supply terminal 50a. A base lead of transistor Q3 is electrically coupled to a collector lead of transistor Q2. Resistor R17 electrically couples the power output of operational amplifier OP4 to a base lead of transistor Q2. Resistor R18 electrically couples the inverting input of operational amplifier OP4 to a collector lead of transistor Q3. Resistor R19 electrically couples an emitter lead of transistor Q2 to ground reference terminal 50b. Resistor R20 electrically couples the emitter lead of transistor Q2 to the collector lead of transistor Q3. Resistor 21 and capacitor C4 electrically couple the collector lead of transistor Q3 to ground reference terminal 50b. Preferably, a boosted output current signal I_OUT2is approximately five (5) milliamperes. Accordingly, it is preferred that resistor R17 and R19 are 5.6 K ohm resistors, resistor R18 is a 10 k ohm resistor, R20 is a 8.2 k ohm resistor, R21 is a trimable 1 k ohm resistor and capacitor C4 is a 0.1 microfarads capacitor.

[0047] While drive circuit 30 and output signal amplifier 40 were described herein as related to Hall effect device 14, it is to be appreciated that the description of drive circuit 30 and output signal amplifier 40 equally related to Hall effect device 114.

[0048] Referring to FIGS. 5A-5C, preferred embodiment of a magnetic rotational position sensor 10′ in accordance with the present invention is shown. Magnetic rotational position sensor 10′ comprises magnetic circuit 13, Hall effect device 14, Hall effect device 114, a circuit 130 including a pair of drive circuits 30 (FIG. 3A), and a circuit 140 including a pair of output signal amplifiers 40 (FIG. 4). Magnetic rotational position sensor 10′ further comprises a power source 50, e.g. a battery as shown, electrically coupled to circuit 130 and circuit 140 to supply a power signal of 5.0 volts to the drive circuits 30 of circuit 130 and the output signal amplifiers 40 of circuit 140. For the illustrated embodiment of the present invention, the pair of voltage sensing signals V_SS1and the pair of voltage sensing signals V_SS2should be 2.5 volts and a pair of output voltage signals V_OUTshould be 2.5 volts as indicated on a voltmeter 60 and a voltmeter 61 for an angular orientation angle θ of zero degrees as shown in FIG. 5A. It is to be appreciated and understood that Hall effect device 14 and/or Hall effect device 114 can have manufacturing anomalies that offsets any of the voltage sensing signals V_SS1, the voltage sensing signals V_SS2, and/or the output voltage signals V_OUTfrom 2.5 volts. Thus, resistor R3 (FIG. 3A) of one or both drive circuits 30, and resistor R11 and resistor R12 (FIG. 4) of one or both output signal amplifiers 40 are trimmed as necessary to transform the values the output voltage signals V_OUTto 2.5 volts. It is to be further appreciated and understood that thermistor TR (FIG. 4) of the output signal amplifiers 40 will maintain the value of output voltage signal V_OUTto 2.5 volts over a temperature range of approximately −40° Celsius and 150° Celsius. As a result, at an angular orientation angle θ of +eighty (80) degrees, the voltage sensing signals V_SS1are 4.5 volts, the voltage sensing signals V_S2are 0.5 volts, and the output voltage signals V_OUTare 4.5 volts as indicated on voltmeter 60 and voltmeter 61 as shown in FIG. 5B. Conversely, at an angular orientation angle θ of −eighty (80) degrees, the voltage sensing signals V_SS1are 0.5 volts, the voltage sensing signals V_SS2are 4.5 volts, and the output voltage signals V_OUTare 0.5 volts as indicated on voltmeter 60 and voltmeter 61 as shown in FIG. 5C. It is to be appreciated and understood that output voltage signals V_OUTvary linearly between 0.5 volts and 4.5 volts, and increase and decrease at a rate of 0.025 volts per full degree of rotation of control shaft 20. As a result, the output voltage signals V_OUTcan be easily processed by a microprocessor based system to monitor and control all rotational movements of control shaft 20 about the first axis.

[0049] Referring to FIGS. 6A-6D, a magnetic rotational position sensor 110 in accordance with the present invention is shown. Magnetic rotational position sensor 110 senses each degree of rotation of a control shaft 20 (FIGS. 1A-1D) about a longitudinal axis 21 (FIGS. 2A-2C) of control shaft 20 over a 180 degree range of rotation without experiencing magnetic hysteresis. Magnetic rotational position sensor 110 comprises ring pole piece 11, magnet 12 magnetic flux sensor 14, and magnetic flux sensor 114 as previously described herein. Magnetic rotational position sensor 110 further comprises a rotor 111 supporting ring pole piece 11 and magnet 12 as illustrated in FIGS. 2A-2C. A carrier 112 is snap fitted within rotor 111 with a bearing cap 113 therebetween. Carrier 112 is also adjoined to control shaft 20 by any method whereby ring pole piece 11, magnet 12, rotor 111, and carrier 112 synchronously rotate with control shaft 20 about axis 21 of control shaft 20 whereby the pair of voltage sensing signal V_SS1and the pair of voltage sensing signal V_SS2are representative of each rotational position of control shaft 20 about longitudinal axis 21.

[0050] Magnetic flux sensor 14 and magnetic flux sensor 114 are electrically coupled to and mounted on a PC board 115 with plane 14aand plane 114abeing coplanar, and plane 14b. (FIG. 1C) and plane 114b(FIG. 1C) being coplanar. PC board 115 is extended into carrier 112 with magnetic flux sensor 14 and magnetic flux sensor 114 being similarly disposed in air gap area 11dof ring pole piece 11 whereby a pair of voltage sensing signal V_SS1and a pair of voltage sensing signal V_SS2(FIG. 3B) from magnetic flux sensor 14 and magnetic flux sensor 114 can be provided to a pair of output amplifiers 40 (FIG. 4). It is to be appreciated and understood that the plane 14aand plane 114aare coplanar to facilitate the pair of voltage sensing signal V_SS1being identical over the 180 degree range of rotation, and the plane 14band plane 114bare coplanar to facilitate the pair of voltage sensing signal V_SS2as being identical over the 180 degree range of rotation.

[0051] All publications, patents, and patent applications cited in this specification are herein incorporated by reference as if each individual publication, patent, or patent application were specifically and individually indicated to be incorporated by reference and set forth in its entirety herein. While the present invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that the preferred embodiments has been shown and described and that all changes, equivalents, and modifications that come within the spirit of the invention are desired to be protected.