WO2021144614A1

WO2021144614A1 - Low consumption contactless sensor

Info

Publication number: WO2021144614A1
Application number: PCT/IB2020/050356
Authority: WO
Inventors: Pierre Karciauskas; Marie-Emilie ROUFFET; Willy Louis Bernard GAUME
Original assignee: Vishay S.A.
Priority date: 2020-01-16
Filing date: 2020-01-16
Publication date: 2021-07-22

Abstract

Systems and methods for non-contact rotary sensing are discussed herein. An example position sensing device may include a position sensor circuit comprising at least a magnetic sensor that is a tunnel magneto resistance (TMR) sensor and a processing circuit. The magnetic sensor, located in a magnetic field of a magnet coupled to a rotary shaft, measures at least one component of the magnetic field generated by the magnet. The processing circuit calculates an angular position value of the magnet based on the measurement of the at least one component of the magnetic field, and generates at least one output signal representing the angular position value of the magnet. The output signal may be analog or digital. An example contactless angular position sensing system may include to one or more cups using one or more position sensor circuits in parallel for redundancy.

Description

LOW CONSUMPTION CONTACTLESS SENSOR

FIELD OF INVENTION

[0001] The disclosure relates generally to position sensors, and more particularly, to systems and methods for non-contact rotary sensing.

BACKGROUND

[0002] Position sensors are used for example in mechanical and electromechanical applications to provide absolute position or displacement measurement information of an object. Angular or rotary sensors measure the angular mechanical position of a rotating object (e.g., by measuring position of a shaft connected to the rotation object), which can be used to determine other useful information such as frequency and speed of the object. Rotary position sensors are used in variety of applications including aeronautics, automotive, electric motor applications, consumer electronics and appliances, industrial applications, wind generators, solar energy systems, test and measurement equipment, robotics, and medical equipment.

[0003] An example of a position sensor is a potentiometer that measures a voltage drop as electrical contact(s) slides along a resistive track, such that the (linear or rotational) position is proportional to voltage output. Potentiometers are typically low cost, simple to produce, lightweight, and have lower power consumption (e.g., on the order of 1mA at 10V operating power). However, potentiometers are contact sensors that are susceptible to high vibration environments and the presence of foreign particles such as dust. [0004] Examples of contactless sensors include optical and magnetic sensors. Optical sensors, also referred to as encoders, operate by measuring a light beam through a grating using a photo detector to generate a position signal. Optical sensors can provide high resolution position measurements but are highly susceptible to foreign particles such that measurement fails if the lens or grating system becomes obscured.

[0005] Magnetic sensors use a magnetic detector to measure the change in magnetic field of a magnet as it moves relative to the magnetic detector, such that the magnetic field changes in proportion to their relative displacement. Magnetic sensors are contactless (non-contact) sensors because there is no contact between the detector and the rotor axis. An example of a magnetic angular position sensor is a Hall Effect sensor that generates, from a bar-shaped conducting material known as a Hall element, a voltage proportional to the intensity of a rotating magnet’s magnetic field passing through it.

[0006] Potentiometers are commonly used in aeronautical apphcations

(e.g., cockpit flight control equipment) in part because they have low power consumption, however they also suffer from quahty issues, such as issues arising from the contact between the track and the cursor, or sensitivity to external pollution that can deteriorate the contact. Thus, there is a desire for a contactless position sensor system that has low power consumption and can be used in place of potentiometers and achieve the same performance in aeronautical apphcations.

SUMMARY

[0007] Systems and methods for non-contact rotary sensing are discussed herein. An example position sensing device may include a position sensor circuit comprising at least a magnetic sensor that is a tunnel magneto resistance (TMR) sensor and a processing circuit. The magnetic sensor, located in a magnetic field of a magnet coupled to a rotary shaft, measures at least one component (e.g., two components for an angle greater than 180°) of the magnetic field generated by the magnet. The processing circuit calculates an angular position value of the magnet based on the measurement of the at least one component of the magnetic field, and generates at least one output signal representing the angular position value of the magnet. The output signal may be analog or digital. An example contactless angular position sensing system may include to one or more cups using one or more position sensor circuits in parallel for redundancy. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1A shows a functional block diagram of an example contactless angular position sensing system including one measurement path with two analog outputs, in accordance with the disclosures herein;

[0009] FIG. IB shows a functional block diagram of an example tunnel magneto resistance (TMR) magnetic sensor circuit that may be used in the example contactless angular position sensing system, in accordance with the disclosures herein;

[0010] FIG. 1C shows a functional block diagram of another example contactless angular position sensing system including one measurement path with one analog output, in accordance with the disclosures herein;

[0011] FIG. ID shows a functional block diagram of another example contactless angular position sensing system including one measurement path with a digital output, in accordance with the disclosures herein;

[0012] FIG. 2 shows an example active-sleep duty cycle for the contactless angular position sensing system, in accordance with the disclosures herein;

[0013] FIG. 3A shows a three-dimensional (3D) diagram of an example contactless angular position sensing system with two cups, in accordance with the disclosures herein;

[0014] FIG. 3B shows a localized diagram of the magnet, magnet support, shaft pin, and pin hood of the contactless angular position sensing system in FIG. 3 A;

[0015] FIG. 4A shows a top view diagram of an example contactless angular position sensing system with three cups, in accordance with the disclosures herein;

[0016] FIG. 4B shows a 3D side view diagram of an example contactless angular position sensing system with three cups, in accordance with the disclosures herein; and

[0017] FIG. 4C shows a 3D side view diagram of an example contactless angular position sensing system with three cups, in accordance with the disclosures herein. [0018] These and other aspects, advantages, and novel features of the disclosed teachings will become apparent upon reading the following detailed description and upon reference to the accompanying drawings. In the drawings, similar elements have similar reference numerals.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Embodiments disclosed herein include contactless angular position sensing systems and methods for measuring the position of an object employing a low consumption high-speed magnetic sensor to measure the magnetic field of a rotating magnet and employ circuitry to produce an output signal proportional to the angular position.

[0020] In the following, example contactless angular position sensing systems are shown and described including some, but not all, possible components. The example contactless angular position sensing systems described and illustrated herein may include other components not shown such as external objects, external systems, housings, shafts, gears, magnets, circuits, protection shields, sources of power etc. Moreover, the components and arrangements of components described are provided as examples and may be substituted with other components or arrangements with equivalent or similar functionality. Moreover, any of the components shown or described may be omitted. The disclosed contactless angular position sensing systems may include one or more measurement channels/paths/cups, in order to provide redundancy and hence reliability for critical apphcations (e.g., aeronautical control systems). Each measurement channel has a corresponding magnetic sensor (e.g., a tunnel magneto resistance (TMR) sensor) and may operate in parallel in the same manner, as described below. Moreover, the measurement channels may use the same type or a different types of magnetic sensors (e.g., channel 1 and 3 use a first type of TMR sensor; channel 2 uses a different sensor such as a Hall effect sensor, a potentiometer or a second type of TMR sensor).

[0021] FIG. 1A shows a functional block diagram of an example contactless angular position sensing system 100A including one measurement path (one cup) and two analog outputs 140 and 142, in accordance with the disclosures herein. The example contactless angular position sensing system 100A could be generahzed to two or more cups using two or more position sensor circuits 103A in parallel. A non-contact rotary position sensor circuit 103A implemented on PCB 101 may include, but is not required to include, any one or more of the following components: a magnetic sensor 104; an analog-to-digital converter (ADC) 108; a processing circuit 112; a memory 114; a power source (e.g., pulse generator) 118; a digital-to-analog converter (DAC) 120; a voltage divider 122; a direct-current-to-direct-current (DC/DC) converter 128; voltage amphfiers 130 and/or 132; and/or protection circuits 126, 134 and/or 136. The non-contact rotary position sensor circuit 103A measures at least one component of the magnetic field created by magnet 102 (e.g., two components of the magnetic field may be measured, for example the radial field and the tangential field), calculates an angular position value of the magnet 102, and generates an output signal 140 representing the angular position value of the magnet 102. In different implementations, the output signal may be analog or digital, as described below.

[0022] The components of the example contactless angular position sensing system 100A are powered by an external power supply 124 (e.g., a 10V power supply). The measurement components forming the chain of acquisition 105 (i.e., magnetic sensor 104, ADC 108, and processing circuit 112) may be powered by an internal power source 118. The internal power source 118 may be powered by the power supply 124 and may be for example a pulse generator 118 in order to allow the components in the chain of acquisition 105 to periodically power down to reduce power consumption, as explained below.

[0023] The contactless angular position sensing system 100A measures the angular position of magnet 102, which in turn may be coupled to a rotating object (not shown) that is subject to measurement. The measurement of the angular position of magnet 102 is made by the magnetic sensor 104 positioned in the rotating magnetic field of magnet 102. In an example, the magnetic sensor 104 is a high-sensitivity, low-consumption magnetic sensor. An example of a magnetic sensor that can be used is a Hall effect sensor, but which may have higher power consumption than a typical potentiometer (e.g., on the order of 10mA- 100mA at 10V operation). However, Hall effect sensors have a high noise level and reduced speed due to the need to add an offset elimination system (e.g., chopper technology) to minimize Hall offset on the chip. Another example of a magnetic sensor that can be used is an anisotropic magnet resistance (AMR) sensor. AMR sensors have higher power consumption than for example TMR sensors. AMR sensors also have a much lower output voltage (e.g., a few tens of millivolts) which requires the addition of an amphfication stage. This amplification stage consumes energy, may cause additional defects (e.g., non-linearity, noise, etc.), takes up space on the PCB 101, and reduces the overall reliability.

[0024] Thus, a preferred example of a magnetic sensor 104 is a tunnel magneto resistance (TMR) sensor, which has a further reduced power consumption that is comparable to the power consumed by a potentiometer (e.g., on the order of 5mA or less at 10V operation, or 5 to 10 times less than a typical Hall effect sensor). In addition to low power consumption, other advantages of a TMR sensor over a Hall effect sensor include low output noise (approximately 10 times less) and the speed of measurement, which enables further power savings through longer sleep cycles as described below. A TMR sensor has a quick measurement time (e.g., on the order of a few ps or less, for example l-2ps) compared to the measurement time of a Hall effect sensor (e.g., on the order of 10-20ps). Hall effect sensors have a high noise level and the speed reduction of the Hall effect sensors is due to the need to add an offset elimination system (e.g., chopper technology) to the Hall effect sensor. For example, a TMR sensor may have a measurement speed that is 50 times faster than a Hall effect sensor. A TMR sensor does not have internal components or software, and has a high output voltage level permitting direct reading of the analog output voltage by an ADC without the need for an amphfier. Thus, a TMR magnetic sensor 104 is preferably used.

[0025] FIG. IB shows a functional block diagram of an example TMR magnetic sensor 104 that may be used in the example contactless angular position sensing system 100, in accordance with the disclosures herein. The TMR magnetic sensor 104 has two measurement bridges offset by 90° (sine+/- and cosine+/-) to detect the radial field and the tangential field, respectively. The outputs 106 of the bridges allows a differential measurement of the sine and the cosine of the magnetic field generated by magnet 102 present at the center of the magnetic sensor 104.

[0026] A TMR cell 104 can be placed at any angle (0°-360°) relative to the magnet 102. In contrast, a Hall effect sensor must be perpendicular to the magnet 102 in order to measure the magnetic field and the rotation position. TMR cell type magnetic sensor 104 may require the magnet 102 to have a large magnetic field (e.g., on the order of 20-50mT) in order to accurately measure the angular position. For example, magnet 102 may be a samarium- cobalt (SmCo) dipolar ring magnet. SmCo material offers a high level of magnetization, a low temperature coefficient and very good resistance to demagnetization and oxidation. The analog outputs 106 from the magnetic sensor 104 are provided to and measured by an ADC 108, which converts analog outputs 106 into digital signal 110. The ADC 108 may be for example a fast 12-bit 4-channel ADC, and may produce two 12-bit digital output signals 110 (one for sine, and one for cosine). In another example, ADC 108 may be a two differential channel ADC.

[0027] The ADC 108 provides the digital signal 110 to the processing circuit 112. The processing circuit 112 performs the calculations to convert the digital signal 110 (e.g., based on the sine and cosine signals 106) to a value proportional to the angle of rotation of the magnet 102 and hence the rotating object (e.g., by computing arctg (sin / cos)). The calculation can be done directly by the processing circuit 112 and/or using a table stored in memory 114. For example, the processing circuit 112 may be a microcontroller, a field programmable gate array (FPGA) or a complex programmable logic device (CPLD). In an example, an FPGA or CPLD may be more suitable for aeronautical applications (with no internal software) than microcontroller. In particular, an aeronautical FPGA processing circuit 112 may be specially designed for fast switching between a sleep state and an active state, as described below. In an example, the processing circuit 112 acquires the digital signal 110 from the ADC 108 and performs an angle calculation (e.g., arctg (sin / cos)) via a conversion table stored in an external memory 114. In an example, the processing circuit 112 performs the calculation on a set of 24 bits (sine + cosine). A conversion table may be specific to each measurement channel/path/cup (e.g., one table per cup) and may be stored in memory 114 during calibration of the corresponding channel (e.g., during manufacturing or initial configuration), and is used to correct possible non-linearity defects and to define the absolute position. The radial and tangential components of the magnetic field are generally not exactly sinusoidal and thus a correction table may be used to compensate for these distortions of the signal 106.

[0028] Once the digital data signal 110 has been processed, the processing circuit 112 provides a digital rotational measurement value 113 to the digital-to-analog converter (DAC) 120 (e.g., a 16-bit DAC), which converts the digital measurement value 113 into an analog output voltage 140 representation of the angular rotation position of the magnet 102, and/or sends a numerical value through a digital interface (e.g. serial synchronous interface (SSI), not shown) to the user. In an example, a voltage divider 122 may be used in cases where the input voltage 125 is too high (e.g., 10V) for the ADC 108 reference input. Thus, the voltage divider 122 divides the supply voltage 125 provided by power supply 124 and further generates the middle point voltage value 142. The analog output voltage 140 and the middle point voltage value 142 may be ratiometric, and the middle point voltage value 142 may be used as a fixed reference when a relative position with respect to a reference position is desired by a user. The middle point voltage output 142 may be omitted, as shown in the example contactless angular position sensing system lOOC of FIG. 1C.

[0029] Voltage amphfiers 130 and 132 may be used to amplify the output signals from the DAC 120, and the voltage protection circuits 126, 134 and/or 136 may be included in contactless angular position sensing system 100A to provide protection for the components against unwanted effects from electromagnetic energy (e.g., electromagnetic compatibility (EMC), electrostatic discharge (ESD) and/or hghting protection, etc.). Although three protection circuits 126, 134, 136 are shown, any number of protection circuits may be included (0 or greater) and may be added between any two components in the contactless angular position sensing system 100.

[0030] The contactless angular position sensing system 100A is able to measure the rotary position of the magnet 102 in a short period of time (e.g., on the order of a few microseconds, ps) because of the high operation speed of the TMR magnetic sensor 104, the ADC 108 and the FPGA processing circuit 112, relative the rotation of rotating object being measured. As a result of the fast speed of measurement, it is possible to allow at least one of the measurement components in chain of acquisition 105 (i.e., the magnetic sensor 104, the ADC 108, and/or the FPGA processing circuit 112) to quickly power down into an inactive or sleep state (powered-down state) in between measurements and enter an active powered-on state for only as long as necessary to refresh the measurement. This power cycling of the magnetic sensor 104, the ADC 108, and/or the processing circuit 112 can be controlled for example using a pulse generator 118 to control the sleep/wake cycle. The periodic power cycling further reduces the overall power consumption of the contactless angular position sensing system 100. The power cycling may or may not be used. For example, periodic power cychng may be used if a very low consumption is needed. In another example, the chain of acquisition 105 may be powered permanently to further increase the speed of response of the magnetic sensor 104.

[0031] In an example aeronautical apphcation involving manual flying commands, the speed of rotation of an object (e.g., a moving part in the aeronautical system) requires measurement approximately every 0.5ms- lms. A total measurement time that is approximately 10ps (including measurement and processing performed by the magnetic sensor 104, the ADC 108, and/or the FPGA processing circuit 112) permits the components of contactless angular position sensing system 100A to have a duty cycle less than 10% (e.g., 6% with 30ps in ON state and 500ps in OFF state). In this case, the consumption of the magnetic sensor 104, the ADC 108, and/or the FPGA processing circuit 112 can be reduced by a factor of approximately 16. [0032] Other components, such as the DAC 120 and the amphfiers 130 and 132 are not power down on a cycle. In an example, the DAC 120 and the amplifiers 130 and 132 remain continuously powered on in order to maintain the output signal 140.

[0033] The assembly of the contactless angular position sensing system

100A may include inserting the PCB(s) 101 and TMR cell(s) 104 at the same time into a housing (e.g., housing 346 in FIG. 3A), securing the TMR cell(s) 104 with screws and securing the PCB(s) 101 with spacers (e.g., spacers 466 in FIG. 4C).

[0034] As described above, the components and arrangements of components shown in the example contactless angular position sensing system 100A may be substituted with other components or arrangements with equivalent or similar functionality; moreover, not all components are shown, and any subset of the components shown or described may be omitted. For example, FIG. 1C shows another example contactless angular position sensing system lOOC, where the position sensor circuit 103B includes the same acquisition system 105 but only one analog output 140 is produced and no middle point signal is generated. FIG. ID shows another example contactless angular position sensing system 100D, where the position sensor circuit 103D also includes the same acquisition system 105 but where the output of the example system 100D is a digital output signal 113, such that a DAC is not needed. For the example system 100D, the digital output value 113 of the angle may be read by an external digital system (not shown) using digital data transmission (e.g., using serial peripheral interface (SPI) or SSI standard protocols).

[0035] FIG. 2 shows an example active-sleep duty cycle for the contactless angular position sensing system 100. In the example of FIG. 2, the chain of acquisition 105 (i.e., the magnetic sensor 104, the ADC 108, and the FPGA processing circuit 112) is active and performing a rotation measurement for approximately 30ps and repeating said measurement approximately every 500ps, with an effective measurement frequency of 2kHz. In this case, the chain of acquisition 105 is active approximately 6% of the time, and can power down to conserve power approximately 94% of the time without interfering with the response time of the magnetic sensor 104. For example, if the magnetic sensor 104 has a response time of 300° / s, if a measurement is made every 500ps, there will be only 0.15° of variation between two measurements. During the 500ps period when the chain of acquisition 105 is powered down, the output voltage 140 remains constant. By waking up the chain of acquisition for 30ps every 500ps, the consumption of the components in the acquisition system 105 is divided by approximately 16. Other measurement frequencies and/or ON time/OFF time durations may be used.

[0036] In order to improve the robustness of an angular measurement system for critical aeronautical applications that have zero tolerance for error for safety reasons, multiple redundant measurement paths or cups may be used. An example measurement system including two redundant cups may include two angular position sensing systems 100A as shown in FIG. 1A implemented on two respective PCBs. Similarly, an example measurement system including three redundant cups may include three angular position sensing systems 100A as shown in FIG. 1A implemented on three respective PCBs (and similarly for four or more cups). In an example, the overall external size of the contactless angular position sensing system may be the same with 2 cups as with 3 cups. In another example, multiple magnets may be mounted on the same rotary shaft. For example, the number of magnets may be equivalent to the number of cups (the number of position sensor circuits) in the contactless angular position sensing system.

[0037] FIG. 3A shows a three-dimensional (3D) diagram of an example contactless angular position sensing system 300 with two cups (for redundancy), in accordance with the disclosures herein. Each cup in the example contactless angular position sensing system 300 may have an equivalent configuration to the example contactless angular position sensing system 100A in FIG. 1A. The movement of a rotating object (not shown) may be input to the system 300 by coupling or connecting the rotating object to the entry shaft 344 that follows the movement of the rotating object. The rotation of the entry shaft 344 inside the housing 346 is measured by internal electronics located on PCB 301 including magnetic sensor 304, which is preferably a TMR sensor (the general location of the magnetic sensor 304, although not visible, is shown in FIG. 3A; an example configuration of magnetic sensors 401i-40l₃ with multiple cups is shown in FIG. 4A). The entry shaft 344 may be cylindrical or cubic in shape, and may be guided within the housing 346 by pre-stressed precision bearings 348.

[0038] A magnet 302 is coupled to the entry shaft 344 and may include a magnet support 350 (e.g., a non-magnetic part that supports the magnet). The magnet 302 and magnet support 350 are locked in rotation on the longitudinal axis of the entry shaft 344 by a steel shaft pin 352. A pin hood 355 keeps the magnet cover in place, which secures the shaft pin 352. The shaft pin 352 keeps the magnet 302 in rotation. The angular movement of the shaft 344 gives an angular rotation of the magnet 302. The magnet 302 is diametrically magnetized, such that the north and south poles of the magnet 302 are perpendicular to the axis of rotation of the entry shaft 344. In an example, a multipole magnet can be used for magnet 302 (e.g., for incremental sensors or for small angle range).

[0039] The magnet 302 may be positioned centrally within the contactless angular position sensing system 300 so as to reduce the moment of inertia and the vibrations. One or more TMR cells 304 (only general location shown) mounted one or more PCBs 301 are arranged outside the magnet 302 and between the magnet 302 and the magnetic shield 356. One PCB 301 may be used for each TMR cell 304. For example, in the case of two cups, two TMR cells 304 may be mounted on two respective PCBs 301 and positioned around the magnet 302. Each of the PCBs 301 are electrically connected to a dedicated processing board by PCB connectors or wires. Using one corresponding PCB 301 for each TMR cell 304 may increase the reliability of the system 300, however any number of PCBs may be used. In an example, one common PCB 301 may be used for multiple TMR cells 304. Positioning of the magnetic cells 304 with respect to the poles of the magnet 302 does not matter as compensation can be made during factory calibration (a preferred example positioning of magnetic sensors 401i-40l₃ with multiple cups is shown in FIG. 4A).

[0040] The magnetic shield 356 located in the housing 346 confines the magnetic field of the magnet 302 to inside the contactless angular position sensing system 300. Each PCB 368 or 370 includes a small connector (not shown) used during the calibration. PCB 368 may contain some or all the electronic parts for track 1, and similarly PCB 370 may contain some or all the electronic parts for track 2, except the magnetic cell 304, which resides on PCB 301. The output signal generated by the internal electronics located on the PCB(s) 368 or 370 may be provided to the user via output terminals 360. The example contactless angular position sensing system 300 may further include, but is not required to include, a cover 364. FIG. 3B shows a localized diagram of the magnet 302, magnet support 350, shaft pin 352, and pin hood 355 of the contactless angular position sensing system 300 in FIG. 3A. As shown in FIG. 4B, the magnet 302 may be locked in a magnet holder 350 and thus locked in rotation and in axial displacement by a shaft pin 352. Using a magnet holder 350 prevents error in case of cracking, and prevents jamming due to complete potting. To prevent the displacement of the shaft pin 352, an additional cover 354 is used. The cover 354 is locked using the deformable pin hood 355.

[0041] FIGs. 4A, 4B and 4C show top and side view diagrams of an example contactless angular position sensing system 400 with three processing boards, PCBs and TMR cells 4021, 402₂, 402₃ surrounded by magnetic shield 456 and with the magnet 402 at the center. FIG. 4C further shows entry shaft 444, magnet support 450, and pin hood 455. The example contactless angular position sensing system 400 may be generahzed to any number of cups. For example, contactless angular position sensing systems with one or two cups may be configured similarly and using one or two PCBs and one or two magnetic cells.

[0042] Any of the example contactless angular position sensing systems described herein may include protections and/or security, including essential protections for onboard aeronautical application. For example, lightning protection may be included such as diodes of protection and resistances on any or all component inputs and/or outputs between components. In another example, electromagnetic compatibility (EMC) protection may be included such as filters on any or all component inputs and/or outputs, hood shielding, and/or grounding of the housing. In another example, electrostatic discharge (ESD) protection may be included such as ESD protection diodes, and internal shielding ensuring immunity to external fields as well as a lack of disturbance of the devices in the neighborhood.

[0043] Other features and components of the example contactless angular position sensing systems provide security and robustness against fault and error. For example, shafts, bearings, pin, and/or pinhoods (circlips), similar to those used with potentiometers, may be mounted on the flight controls. Minimizing the length of components, such as the shafts axes length, provides better vibration resistance. In another example, a mono block case with flange may be used to provide electrical continuity ( in terms of EMC), and so that deformation of the cover does not lead to an output error (fixing on the flange).

[0044] The disclosed contactless angular position sensing system may replace potentiometers, for example in aeronautical applications, and can provide the same specifications as potentiometers (e.g., a 10 KOhm (EW) potentiometer with low consumption on the order of 1mA at 10V).

[0045] In addition to the example embodiments described above, other example configurations may be used. Any number redundant sensor circuits may be used to within the housing of the contactless position sensing system thus supplying multiple independent and redundant output signals each indicating angular position provide more robust measurement information. In another example, different combinations of different types of magnetic sensing circuits may be implemented within the same contactless angular position sensing system, such as using both Hall effect sensors and magnetoresistance sensors. [0046] In the example disclosures herein, the size and combinations of components may be adaptable according to user requirements such as size, length, and mode of attachment. k k k

Claims

CLAIMS What is claimed is:

1. A position sensing device, comprising: a first position sensor circuit comprising at least a magnetic sensor that is a tunnel magneto resistance (TMR) sensor, an analog-to-digital converter (ADC), a processing circuit, and a memory; wherein, the memory is configured to store a conversion table; the magnetic sensor is located in a magnetic field of a magnet coupled to a rotary shaft and is configured to measure two components of the magnetic field generated by the magnet to generate analog measurement signals; the ADC is configured to convert the analog measurement signals to digital measurement signals; and the processing circuit is configured to generate an angular position value of the rotary shaft based on the digital measurement signals and based on the conversion table.

2. The position sensing device of claim 1, wherein the magnetic sensor is not in contact with the rotary shaft and is not in contact with the magnet.

3. The position sensing device of claim 1, wherein the first position sensor circuit consumes 5mA or less at 10V power supply operation.

4. The position sensing device of claim 1, wherein the magnetic sensor has a response time of a few ps or less.

5. The position sensing device of claim 1, wherein: the magnetic sensor and the processing circuit are configured to power down for a period of time after the angular position value of the rotary shaft is generated.

6. The position sensing device of claim 1, wherein: the magnetic sensor and the processing circuit are in a powered-on state less than 10% of an operating time and are in a powered-down state greater than 90% of the operating time.

7. The position sensing device of claim 1, wherein the magnet is a samarium-cobalt (SmCo) dipolar ring magnet.

8. The position sensing device of claim 1, wherein the magnet is a multipole magnet.

9. The position sensing device of claim 1, wherein the rotary shaft is coupled to an external rotating object that drives the rotation of the rotary shaft.

10. The position sensing device of claim 1, wherein the processing circuit comprises a field programmable gate array (FPGA) or a complex programmable logic device (CPLD), and the processing circuit is configured for fast switching between a sleep state and an active state.

11. The position sensing device of claim 1 further comprising: a plurahty of position sensor circuits equivalent to the first position sensor circuit, wherein each of the plurality of position sensor circuits generates an independent output angular position value of the rotary shaft.

12. The position sensing device of claim 11, further comprising a plurality of magnets mounted to the rotary shaft, where a number of magnets in the plurahty of magnets is equal to a number of position sensor circuits in the plurality of position sensor circuits.

13. The position sensing device of claim 1 further comprising a magnetic shield, wherein the magnetic sensor is located in between the magnet and the magnetic shield.

14. The position sensing device of claim 1, wherein the angular position value is an numerical output.

15. The position sensing device of claim 1, the first position sensor circuit further comprising: a digital-to-analog converter (DAC) configured to convert the angular position value into an analog angular position value.

16. The position sensing device of claim 1, the first position sensor circuit further comprising: at least one protection circuit configured to protect against electromagnetic energy.

17. The position sensing device of claim 1, wherein the first position sensor circuit is implemented on a printed circuit board (PCB).

18. The position sensing device of claim 1, the first position sensor circuit further comprising: at least one voltage amplifier configured to amplify the angular position value.

19. The position sensing device of claim 1, the first position sensor circuit further comprising: a voltage divider configured to divide a supply voltage to generate a middle point voltage value of the angular position value.

20. The position sensing device of claim 1 further comprising: a housing configured to encompass at least a portion of the rotary shaft, the magnet and the first position sensor circuit; and at least one pre-stressed precision bearing configured to guide the rotary shaft within the housing.