Abstract:
A rotor disk or color wheel received on a shaft to be sensed has an annular band of dual color (red/green) filter material having opposite circumferential gradient. A printed circuit board on one axial side of the rotor disk has the dual color LED, emitting light to a reflector on the opposite axial side of the rotor disk. Some reflected light from the LED passes through the filter which transmits, according to the amount of single color filter material present at the particular rotor station to a photodetector on the circuit board. Other rays of the emitted light are reflected directly to a second detector for ambient compensation. The amount of light transmitted by the filter causes the detector current to vary the charge rate of a capacitor charged to a reference level, and when reached the LED is switched to the other of the dual color emission. The time required to charge the capacitor to the reference level determines the fraction of the duty cycle of the output signal which may be correlated with known data on the color gradient to determine the rotor angular position. A second color wheel is indexed or geared up or down as an integrator for counting the number of full revolutions of the shaft color wheel.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     MICROFICHE APPENDIX 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     The present invention relates to sensors of the type employed for remotely determining the rotation or angular position of a rotor or shaft by providing an electrical signal indication of the rotational position of the shaft or rotor from a reference datum. The invention relates particularly to providing such a signal on a continuing basis as a transducer. 
     Rotary angle or position transducers are desired for various control systems; and, in one application is it desired to provide the accumulated angular rotation of a vehicle steering shaft for providing a signal indicative of the steering shaft rotation to a system employed for providing variable effort power assist to the vehicle steering system. Another use for a steering shaft position sensor is to provide a signal from which the turn signal lights may be activated and de-activated. 
     Angle or rotary position sensors or transducers employing optical sensing of the rotation of a rotor are known and an example of such a device is that shown and described in U.S. Pat. No. 4,947,036 issued to J. D. Pokorski, et al which describes a device utilizing a dual color light source to illuminate a rotating member which includes material providing a gradient of the two colors of the light source disposed thereon for reflection or filtered transmission, the results of which are detected by photodetectors to determine a ratio of the detected output light intensities which is compared with the known arrangement of gradient on the rotating member for determining the position of the rotating member. The aforesaid known techniques employ light beams of different wave length or color chromaticity for detecting the angular or rotary position of a moveable member. Such known devices have used photodetectors to determine the relative intensity of light of a discrete wave length or color chromaticity either transmitted through a filter or reflected from a surface having material of a discrete wave length or color chromaticity. Such known techniques of measuring reflected or transmitted light of a given color chromaticity for determining the rotary position of a member by detecting the relative intensity of the reflected or transmitted light are subject to error and suffer from a relatively low signal-to-noise ratio in the presence of spurious or stray light and to variations in the color chromaticity of the material through which the light is transmitted or reflected. 
     In such known arrangements, the detector voltage is proportional to the intensity of the detected light, either transmitted or reflected. It is also known to alternately direct the beams of light of a first and second color chromaticity through a filter or on a reflective material of discrete color chromaticity to the photodetector utilizing synchronized time multiplexing to produce a voltage proportional to the intensity of the received light. Typically, a microprocessor is responsive to the photodetector voltage to compute the ratio of the detector voltage arising from the alternate detection of light of the first and second color chromaticity. 
     In the aforesaid known techniques, proportion of the amount of light detected of one wave length or chromaticity is then correlated with a predetermined relationship between the position of the rotor and the proportion of the colored material of one chromaticity present at a particular station on the rotor. This correlation enables the detection of the rotary position of the rotor. 
     The known techniques for sensing the position of a rotor using light of two different wave lengths have been proven generally effective; however, where a high degree of accuracy on the order of 1° or less resolution is required, the aforesaid known techniques have been proven inadequate to provide the desired resolution. Known rotary position transducers utilizing color gradient detection have been arranged with the light source and the detectors positioned oppositely with respect to the rotor, and have thus been subject to tolerance accumulation with respect to their placement and this has resulted in variation of the sensed or detected color intensity resulting in error of the measured angle of rotation. Furthermore such known rotary position detectors have been difficult to assemble and calibrate in high volume production and thus costly for automotive steering shift position sensing applications. 
     In applications for sensing the rotary position of a shaft where a high degree of resolution typically less than 1° angular movement is required, for example in a device for detecting the rotary position of a vehicle steering shaft for purposes of providing a signal useable to control the variable assist in a power steering system it has been desired to provide an accurate, easy to assemble and calibrate and reliable angle sensor which is low in manufacturing cost. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention utilizes a rotor having filter material of opposite angular gradients of two different wave lengths or chromaticities on the rotor to receive and transmit light from a source of illumination alternately of light of one and then the other of the selected wave lengths or chromaticities. The results of which transmission are reflected to a photodetector providing an electrical signal indicative of the amount of light transmitted of the selected wave lengths or chromaticity. The light source preferably comprises light emitting diodes, and the photodetectors are disposed on a circuit board on a common side of the rotor; and, the reflective surface indisposed on an axially opposite side of the rotor enabling complete assembly of all electrical/electronic components on the board prior to final assembly in the housing. 
     The current in the photodetector is employed to modify the rate of charge of a capacitor; and, the time required for the capacitor to reach a predetermined charge or voltage level is employed to generate a pulse signal having the duration thereof corresponding to the time required to charge the capacitor, thus giving a width modulated signal indicative of the proportion of the resultant light representative of a particular station on the rotor. The proportion of light of the given wave length is then correlated with the predetermined value of the color gradient at the particular location or station on the rotor and the rotor position may thus be electrically determined. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top view of the assembled sensor/transducer in the preferred form of the present invention; 
     FIG. 2 is a perspective view of the assembly of FIG. 1; 
     FIG. 3 is a section view taken along section indicating lines  3 — 3  of FIG. 1; 
     FIG. 4 is a section view taken along section indicating lines  4 — 4  of FIG. 1; 
     FIG. 5 is a perspective view of the sectioned portion of FIG. 4; 
     FIG. 6 is a perspective view of the sectioned portion of FIG. 3; 
     FIG. 7 is an exploded view viewed from above of the assembly of FIG. 1; 
     FIG. 8 is a view similar to FIG. 7 as viewed from below of the assembly of FIG. 1; 
     FIG. 9 is an enlarged portion of a broken-away view of the assembly of FIG. 1; 
     FIG. 10 is a top view similar to FIG. 1 of an alternate embodiment of the invention; 
     FIG. 11 is a perspective view of the assembly of FIG. 10; 
     FIG. 12 is an exploded view taken from above of the embodiment of FIG. 10; 
     FIG. 13 is an exploded view taken from below of the embodiment of FIG. 10; 
     FIG. 14 is a section view taken along section indicating lines  14 — 14  in FIG. 10; 
     FIG. 15 is a section view taken along section indicating lines  15 — 15  of FIG. 10; 
     FIG. 16 is a perspective view of the sectioned portion of FIG. 14; and, 
     FIG. 17 is a perspective view of the sectioned portion of FIG.  15 . 
     FIG. 18 is a schematic of the circuit for processing the signal from the photodetectors of the embodiment of FIGS.  1  and  10 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIGS. 1 through 9, the preferred form of the invention is shown in which the sensor/transducer assembly is indicated generally at  10  and includes a housing base or shell  12  and a cover or closure member  14  which together comprise the base structure of the assembly. The cover  14  includes a tower or receptacle portion  16  which is adapted to receive an external electrical connector or plug (not shown) through aperture  18 , for making electrical connection to the internal components in any convenient manner such as by pin and socket connection (not shown). 
     An annular rotor hub  20  has the inner periphery thereof adapted to receive a shaft, such as a steering shaft (not shown) therethrough and has means provided on the inner periphery for frictional engagement with the unshown shaft. In the present practice of the invention, it has been found satisfactory to provide resilient annular rings  22 ,  24  respectively received in annular grooves  26 ,  28  formed in the inner periphery of the hub  20 , which annular rings are radially compressed upon assembly of the rotor hub  20  over the shaft to be monitored. It will be understood however, that other means of frictionally engaging the inner periphery of the rotor hub  20  with a shaft may be employed such as, for example, frictionally engaging a splined or knurled surface on the shaft or providing a key-way and key-in driving connection. Alternatively, deformable frictionally engaging surfaces (not shown) may be formed on the inner periphery of the hub to resiliently engage the shaft as the hub is received over the shaft. 
     The upper end  30  of the hub  20  is journalled in an aperture  32  formed in cover  14 ; whereas, the lower end  34  of rotor hub  20  is journalled in an aperture  36  formed in the base  12 . 
     Rotor hub  20  has attached thereto in driving engagement an annular disk  38  which is formed of generally transparent material and which has provided about the outer periphery thereof a band of color filter material  40  which has a gradient thereon of two discrete chromaticities with the gradient, for each chromaticity varying oppositely in the circumferential direction. The band of color material  40  is thus retained between an annular member  42  and the rotor disk  38  in a sandwiched fashion. In the present practice of the invention, the rotor disk has a diameter of about 60 millimeters. 
     In the present practice of the invention it has been found satisfactory to form the rotor disk  38  of transparent polycarbonate plastic material with the color gradient ring  40  formed of photographic film material with the color gradient material developed on the surface thereof by techniques well known in the art. The ring  42  is received over the color gradient filter material  40  and is secured thereon by any suitable expedient as, for example, weldment or heat staking of the inner periphery of the ring  42  to the rotor disk  38 . It will be understood however that other materials may be employed for the rotor disk and ring  42  and other techniques employed for securing ring  42  thereto. The color gradient material  40  may also be formed by silk screening color material on a transparent substrate; however, where a high degree of resolution, such as resolution less than 1° of angular rotation of the rotor disk  38  and particularly less than 0.1° of angular rotation is required, the use of photographic color film for the color ring  40  has been found to provide a higher degree of resolution. 
     In the presently preferred practice of the invention, the film ring  42  of color filtering material having a two color annular gradient is comprised of film material having a thickness of about 0.008 inches (0.20 millimeters); however, other thicknesses of film material may be employed if desired. 
     In the present practice of the invention, the number of pixels or dots changed in 0.1° of angular rotor movement is about 880 for a color “window” area of 6.7 mm 2 . It will be understood however that the arrangements of and densities of color may be employed depending upon the angular resolution desired. 
     Referring to FIGS. 3 through 8, hub  20  has a pin  44  extending downwardly from the undersurface thereof which, once each full revolution of the hub  44 , engages one of a plurality of circumferentially spaced notches or slots  46  provided in an index wheel  48 . Wheel  48  has a central aperture  50  formed therein which is journalled over a stanchion  52  extending upwardly from the interior surface or bottom of base  12 . 
     A second color wheel  54  has a central aperture  56  formed therein which is journalled for rotation over a stanchion  58  spaced from stanchion  52  and also extending upwardly from the bottom of base  12 . 
     Color wheel  54  has a plurality of pins spaced circumferentially thereabout and extending downwardly from the undersurface thereof as denoted by reference numeral  60  which pins  60  sequentially engage one of the slots  46  upon rotation of index wheel  48 . Thus, each full revolution of the hub  20  causes pin  44  to engage one of the slots  46  in index wheel  48  indexing the wheel  48  so as to cause a corresponding index movement of color wheel  44 . Thus, wheel  54  is an integrator or accumulator of the number of successive full revolutions either clockwise or counter-clockwise of the hub  20 . 
     Wheel  54  has provided on its upper surface a plurality of arcuate color segments  62  disposed and secured in a manner similar to the color film band  40  of rotor disk  38 . The arcuate segments  52  being formed of film similar to band  40 , but each having a uniform but discrete chromaticity as opposed to a color gradient employed on the color film band  40 . 
     Referring to FIGS. 3 through 9, a circuit board subassembly indicated generally at  66  has a plurality of pairs of photodetectors  68 ,  70 ,  72 ,  74 ,  76 ,  78  disposed thereon. Each pair of photodetectors having a dual color light emitting source preferably a light emitting diode as denoted by reference numeral  80 ,  82 ,  84  disposed between the pairs as shown in FIGS. 8 and 9 on the undersurface of the circuit board  64 . The pairs of photodetectors and their accompanying diode are arranged so that the pairs  68 ,  70  and  72 ,  74  are disposed about the periphery of the color band  40  with the detectors  70 ,  72  disposed axially adjacent the color band  40  of rotor disk  38 ; and, the remaining ones of the pairs,  25  specifically detectors  68 ,  74  are disposed beyond the periphery of the color band  40 . The diodes  80 ,  82  are disposed likewise radially outwardly of the outer periphery of the color band  40 . 
     Photodetector pair  76 ,  78  is disposed with the detector  78  adjacent the color segment  62  on color wheel  54 ; and, detector  76  is disposed radially outwardly of the periphery of the color wheel  54  as is diode  84 . 
     The printed circuit board assembly  66  is preferably attached to the undersurface of cover  14 . Electrical connection to the circuit board assembly is made through aperture  18  by plug-in or pigtail connection which is omitted for simplicity of illustration. 
     Each pair of the photodetectors has disposed at the same station thereas, but on the opposite axial side of the rotor disk  38 , a pad having the surface thereof formed as a light reflecting surface. The pads are denoted in the drawings by reference numerals  86 ,  88 ,  90  and are attached preferably to the inner surface of the base  12  with the reflective surface thereof facing upward toward the photodetectors and light emitting diodes. 
     Referring to FIG. 9, the path of the light from the LEDs is shown by black arrow wherein some of the light from the light emitters is reflected from the reflective surface of pad  88  and is transmitted through the color band  40  on rotor disk  38  and filtered therethrough according to the gradient of the film at the particular station on the rotor; and, the light transmitted through the filter is detected by the photodetector  72 . Other rays of the light from emitter  82  are reflected in the opposite direction on reflective surface of pad  88  and do not pass through a filter but directly strike the reference detector  74 . This arrangement thus provides a reference level of intensity to permit compensation for ambient conditions such as temperature, dust and moisture. 
     Thus, as the rotor disk  38  is rotated by the hub  20  which in turn is rotated by the shaft (not shown) the amount of red or green filtering material in the color film  40  determines the amount of red or green light transmitted to detector  72  depending on which of the two chromaticities is being emitted at a given instant of time. The electrical output of the detector  72  is then processed in a manner which will hereinafter be described to provide a correlation with the known color gradient at various stations on the rotor to thus enable a determination of the actual angular position of the rotor with respect to the stationary detector  72 . 
     It will be understood that the wheel  54  and detectors  76 ,  78  operate in the same fashion, except that the color band on color wheel  54  comprises discrete angular segments, each having a uniform but discretely different chromaticity instead of the gradient employed in the color band  40  of rotor  38 . The detector  76  provides an electrical output which is similar to that for detector  72  from which an angular or rotary position of color wheel  54  may be determined as will be hereinafter described and thus the number of full revolutions of the rotor  20  determined. 
     Referring to FIGS. 10 through 17, another embodiment of the invention is indicated generally at  100  with a base  102  and cover or closure  104  having an electrical receptacle tower  106  extending upwardly therefrom with an aperture  107  therein for receiving a plug or connector (not shown). 
     A color gradient wheel indicated generally at  108  has a hub  110  adapted to be received over a shaft (not shown) in driving engagement therewith similar to rotor hub  20  of the embodiment of FIG.  1 . 
     The outer periphery of wheel  108  has an annular band of film developed with two discrete chromaticities thereon with angular opposite gradients similar to the band  40  on the embodiment of FIG.  1  and is indicated by dashed outline and reference numeral  112 . 
     The hub of wheel  108  denoted by reference numeral  114  has annular grooves provided therein into which are received resilient rings  116 ,  118  similar to the rings  22 ,  24  of the FIG. 1 embodiment for providing frictional engagement with the shaft to be received through the hub. The upper end of hub  114  is journalled in an aperture  118  formed in the cover  104 ; and, the lower end of hub  114  is journalled in an aperture  120  provided in the base  102 . The undersurface of wheel  108  includes a gear wheel having peripheral gear teeth  122  disposed therearound which are meshed with corresponding gear teeth  124  provided on ring gear  126  which is received over and journalled on a stanchion  128  extending upwardly from the interior of base  102 . 
     A second color wheel indicated generally at  130  has a central aperture  132  which is received over and journalled on a second stanchion  134  extending upwardly from the interior of base  102  and which stanchion  134  is spaced from stanchion  128 . Wheel  130  has a outer annular band of color filter material having arcuate segments of uniform but discretely differently color thereon disposed about the periphery of the wheel and denoted by reference numeral  136 . Segments  136  may be formed on a single annular film band and attached in a manner similar to film band  112  on wheel  108 . 
     The undersurface of color wheel  130  has provided thereon a gear wheel  138  having a plurality of teeth  140  disposed circumferentially thereabout and which also mesh with teeth  124  on gear wheel  126 . The pitch diameters of teeth  122 ,  124  and  140  are chosen such that one full revolution of color wheel  108  causes color wheel  130  to rotate more or less than one full revolution. 
     A printed circuit board subassembly indicated generally at  142  comprises a circuit board  144  having mounted on the undersurface thereof two pairs of spaced photodetectors  146 ,  148  and  150 ,  151  with each pair having disposed therebetween a light emitting source such as an LED  152 ,  154  respectively. 
     Photodetector  146  is disposed axially adjacent the color band  112  of wheel  108 ; and, LED  152  and photodetector  148  are disposed radially beyond the periphery of wheel  108 . Detector  148  is disposed axially adjacent the color band segments  136  of wheel  130 ; and, LED  154  and photodetector  150  are disposed beyond the periphery of wheel  130 . 
     A pair of pads  156 ,  158  having reflective upper surfaces  160 ,  162  respectively which are disposed on the opposite axial side of the wheel  108  from the detectors so as to receive light respectively from LED  152  through filter segments  136  and directly from LED  154 . It will be understood that the arrangement of the photodetectors and LEDs for the embodiment of FIG. 10 is similar to the arrangement of the embodiment of FIG. 1 as shown in detail in FIG.  9 . In operation, rotation of the wheel  108  a full revolution causes a rotation of wheel  130  by more or less than a full revolution to permit the detectors to identify the angular position of wheel  130  and thus count the number of full revolutions of wheel  108 . 
     The pads  156 ,  158  are preferably attached to the inner surface of the base  102 . In the FIG. 10 embodiment the printed circuit board assembly  142  is preferably attached to the undersurface of the cover  104 . Electrical connection is made through aperture  107  in the tower  106  of the embodiment of FIG. 10 for direct plug in connection with the printed circuit board assembly  142  or alternatively by a pigtail connector, which connection has been omitted for simplicity of illustration. 
     It will be understood that in both the embodiment of FIG.  1  and FIG. 10 the color filter band  40  on the rotor disk  38  and the corresponding band  112  on color wheel  108  may employ oppositely directed adjacent spirals of red and green filter material; or, alternatively may employ circumferentially varying amounts of red and green pixels at each station of the rotor such that the sum of the amount of red and green filter material at any station is substantially constant. 
     In operation, when the LED  82 ,  152  emits red light, the amount of light transmitted through the color bands  40 ,  112  respectively to detectors  72 ,  146  is dependent upon the amount of red filter material present at the particular rotor station. Similarly, when the LEDs  82 ,  152  emit green light, the amount of light transmitted through the filter bands  40 ,  112  to respectively detectors  72 ,  146  is dependent upon the amount of green filter material present at the particular rotor station. 
     In the present practice of the invention the electronic circuitry is operable to cause the LEDs to emit alternately red and green light for a period of time dependent upon the amount of red or green filter material present at a particular rotor station. The output of the detectors is then processed as a duty cycle signal. A correlation may then be made between the amount of red or green filter material present at that station and the known arrangement of the color gradient on the bands  40 ,  112 ; and, the angular rotor position of the rotor may be determined electrically in an unshown microcomputer. 
     Referring to FIG. 18, the circuit for providing an electrical signal indicative of the rotor position is indicated generally at  164 ; and, it will be understood that the circuitry components are included as part of a circuit board assembly  66 ,  142 . 
     Referring to FIG. 18, the light emitters  82 ,  152  comprise a bi-color LED  1 A,  1 B alternating red or green. The photodetectors  72 ,  146  are denoted by photo diode D 1 ; whereas the detectors  74 ,  148  are denoted by photo diode D 2 . 
     Photo diode D 1  receives the red or green light alternately from LED  1 B and LED  1 A as transmitted through the color film band  40 ,  112  on the rotor. The amount of light, either red or green, detected by D 1  is dependent upon the amount of red and green filter material present at the particular rotor station being sensed. 
     U 1  is a quad analog transmission gate: when U 1 D and U 1 C are “ON” red light from LED  18  causes the current in D 1  to flow from cathode to anode. Integrating amplifier U 2 C converts this current to a positive ramp output voltage at pin  8  thereof for charging capacitor C 1  which voltage is also applied to the inverting pin  6  of comparator U 2 B. When the ramp voltage exceeds the reference voltage at pin  5  of U 2 B, the output of U 2 B at pin  7  goes low and pin  1  of U 2 A goes high thereby energizing LED  1 A to emit green light. 
     The analog switches of U 1  are controlled by comparator outputs U 2  pin  1  and U 2  pin  7 . When LED  1 A is energized to emit green light, switches U 1 A and U 1 B are turned to “ON”. The current in detector D 1  then causes integrating amplifier U 2 C output pin  8  to ramp negative until pin  5  of U 2 B falls below the reference voltage at pin  5  U 2 B which is provided by voltage divider network R 3 , R 4 . 
     Output pin  7  of U 2 B goes high staring the cycle again. Resistor R 2  provides for threshold hysteresis between one-third V CC  and two-thirds V CC  and preferably between 0.45 V CC  and 0.55 V CC . Diodes D 3  and D 4  provide for reverse polarity blocking when the supply voltage V CC  is greater than 5 volts DC because the maximum reverse blocking voltage for the LEDs is 5 volts DC. 
     When a color filter such as filter band  40 ,  112  is interposed between LED  1  and photodetector diode D 1 , the ramping voltage on capacitor C 1  will be slower in either the red or the green direction because one LED spectrum will be filtered more than the other. Employing a changing gradient color filter between the LEDs and D 1 , an output at U 2 A pin  1  is obtained which describes the position of the filter in terms of the fraction or percentage of the duty cycle. The frequency can be monitored as a diagnostic, for example, when the frequency is too low a dirty optical interface is indicated. 
     Amplifier U 2 D functions as an optical feedback reference amplifier. The output of U 2 D is controlled by the current through photodetector D 2  which is also illuminated directly by LED  1 . Reference voltage V REF  supplies a current through trimmer resistor RP 1  and resistor R 8  to the cathode of photo diode D 2  and the inverting input pin  13  of U 2 D. The output of U 2 D then adjusts LED current to force zero voltage between U 2 D input pins  13  and  12 . The circuit then functions to force a constant LED intensity dependent only on the stable reference voltage from V REF  and the sensitivity of diode D 2  which tracks photo diode D 1  over the temperature range. The photo diode reference circuit thus compensates for variations in the red and green efficiencies of LED  1 A,  1 B. The values of the various circuit components are indicated in Table I. 
     
       
         
               
               
               
               
               
             
           
               
                 TABLE I 
               
               
                   
               
               
                 Item 
                 Quantity 
                 Reference 
                 Part 
                 Source(s) 
               
               
                   
               
             
             
               
                 1 
                 1 
                 C1 
                 100 pf 
                 0805CG101J9BBO 
               
               
                 2 
                 3 
                 C2, Cx, Cy 
                 0.1 uf 
                 08052R104K8BBO 
               
               
                 3 
                 5 
                 R1, R2, R3, R4, R5 
                 100 K 
                 P100K-CCT 
               
               
                 4 
                 1 
                 R7 
                 430 
                 P432-CCT 
               
               
                 5 
                 1 
                 R8 
                 5.1 Meg 
                 RK73H2AT5114F 
               
               
                 6 
                 1 
                 R9 
                 10 K 
                 P10.0K-CCT 
               
               
                 7 
                 1 
                 RP1 
                 0-20 K 
                 3224W-203E 
               
               
                 8 
                 2 
                 D1, D2 
                 Photo Diode 
                 S6838 Hamamatsu 
               
               
                 9 
                 2 
                 D3, D4 
                 Diode 
                 LL4148 Diode Incorp. 
               
               
                 10  
                 1 
                 LED1A, LED1B 
                 LED diode 
                 KAA-3528ESGC 
               
               
                 11  
                 1 
                 V REF   
                 Zener diode 
                 LM385M-2.5 
               
               
                 12  
                 1 
                 U1A, U1B, U1C, U1D 
                 CD-4016-BCM 
                 Fairchild 
               
               
                 13  
                 1 
                 U2A, U2B, U2C, U2D 
                 LMC6484-AIM 
                 National Semicond 
               
               
                   
               
             
          
         
       
     
     The present invention thus provides shaft rotary angle position sensor/transducer which has high resolution, is compact, easy to manufacture in mass production, relatively low in manufacturing cost and is particularly suitable for sensing the rotary position of a motor vehicle steering shaft. 
     Although the invention has hereinabove been described with respect to the illustrated embodiments, it will be understood that the invention is capable of modification and variation and is limited only by the following claims.