Sensing apparatus and method
First Claim
1. A position sensor comprising:
- first and second members which are movable relative to each other along a measurement direction, the first member comprising first and second excitation windings and a sensor winding, and the second member comprising an intermediate coupling element, wherein the electromagnetic coupling between the first excitation winding and the intermediate coupling element varies with the relative position along the measurement direction of the first and second members in accordance with a first function and the electromagnetic coupling between the second excitation winding and the intermediate coupling element varies with the relative position along the measurement direction of the first and second members in accordance with a second function which is different from the first function;
a signal generator operable to generate first and second excitation signals and to apply the first and second excitation signals to the first and second excitation windings respectively, the first excitation signal comprising a first periodic carrier signal having a first frequency modulated by a first periodic modulation signal having a second frequency and the second excitation signal comprising a second periodic carrier signal at the first frequency modulated by a second periodic modulation signal at the second frequency, wherein in response to the first and second excitation signals being applied to said first and second excitation windings, a periodic electric signal is generated in the sensor winding having a timing which varies in accordance with the relative position of the first and second members along the measurement direction;
a demodulator operable to demodulate the periodic electric signal generated in the sensor winding to obtain a signal at the second frequency; and
a signal processor operable to process the signal at the second frequency output by the demodulator in response to the first and second excitation signals being respectively applied to the first and second excitation windings to determine a first timing measurement representative of the relative position along the measurement direction of the first and second members,wherein the signal generator is further operable to generate a third excitation signal and to apply the first and third excitation signals to the first and second excitation windings respectively, the third excitation signal comprising a third periodic carrier signal at the first frequency modulated by a third periodic modulation signal at the third frequency, the third periodic modulation signal being in anti-phase with the second periodic modulation signal,wherein the signal processor is operable to process the signal at the second frequency output by the demodulator in response to the first and third excitation signals being respectively applied to the first and second excitation windings to determine a second timing measurement, andwherein the position sensor is operable to determine a position value using the first and second timing measurements.
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Abstract
There is described a sensor comprising an excitation winding, a signal generator operable to generate an excitation signal and arranged to apply the generated excitation signal to the excitation winding, a sensor winding electromagnetically coupled to the excitation winding and a signal processor operable to process a periodic electric signal generated in the sensor winding when the excitation signal is applied to the excitation winding by the signal generator to determine a value of a sensed parameter. The excitation signal comprises a periodic carrier signal having a first frequency modulated by a periodic modulation signal having a second frequency, the first frequency being greater than the second frequency. In this way, the sensor is well suited to using digital processing techniques both to generate the excitation signal and to process the signal induced in the sensor windings. In an embodiment, the sensor is used to detect the relative position of two members. In other embodiments, the sensor is used to detect environmental factors such as temperature and humidity.
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Citations
25 Claims
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1. A position sensor comprising:
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first and second members which are movable relative to each other along a measurement direction, the first member comprising first and second excitation windings and a sensor winding, and the second member comprising an intermediate coupling element, wherein the electromagnetic coupling between the first excitation winding and the intermediate coupling element varies with the relative position along the measurement direction of the first and second members in accordance with a first function and the electromagnetic coupling between the second excitation winding and the intermediate coupling element varies with the relative position along the measurement direction of the first and second members in accordance with a second function which is different from the first function; a signal generator operable to generate first and second excitation signals and to apply the first and second excitation signals to the first and second excitation windings respectively, the first excitation signal comprising a first periodic carrier signal having a first frequency modulated by a first periodic modulation signal having a second frequency and the second excitation signal comprising a second periodic carrier signal at the first frequency modulated by a second periodic modulation signal at the second frequency, wherein in response to the first and second excitation signals being applied to said first and second excitation windings, a periodic electric signal is generated in the sensor winding having a timing which varies in accordance with the relative position of the first and second members along the measurement direction; a demodulator operable to demodulate the periodic electric signal generated in the sensor winding to obtain a signal at the second frequency; and a signal processor operable to process the signal at the second frequency output by the demodulator in response to the first and second excitation signals being respectively applied to the first and second excitation windings to determine a first timing measurement representative of the relative position along the measurement direction of the first and second members, wherein the signal generator is further operable to generate a third excitation signal and to apply the first and third excitation signals to the first and second excitation windings respectively, the third excitation signal comprising a third periodic carrier signal at the first frequency modulated by a third periodic modulation signal at the third frequency, the third periodic modulation signal being in anti-phase with the second periodic modulation signal, wherein the signal processor is operable to process the signal at the second frequency output by the demodulator in response to the first and third excitation signals being respectively applied to the first and second excitation windings to determine a second timing measurement, and wherein the position sensor is operable to determine a position value using the first and second timing measurements. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. A position sensor comprising:
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first and second members which are movable relative to each other along a measurement direction, the first member comprising first and second excitation windings, and the second member comprising a sensor winding, wherein the electromagnetic coupling between the first excitation winding and the sensor winding varies with the relative position along the measurement direction of the first and second members in accordance with a first function and the electromagnetic coupling between the second excitation winding and the sensor winding varies with the relative position along the measurement direction of the first and second members in accordance with a second function which is different from the first function; a signal generator operable to generate first and second excitation signals and to apply the first and second excitations signals to the first and second excitation windings respectively, the first excitation signal comprising a first periodic carrier signal having a first frequency modulated by a first periodic modulation signal having a second frequency and the second excitation signal comprising a second periodic carrier signal at the first frequency modulated by a second periodic modulation signal at the second frequency, wherein in response to the first and second excitation signals being applied to said first and second excitation windings, a periodic electric signal is generated in the sensor winding having a timing which varies in accordance with the relative position of the first and second members along the measurement direction; a demodulator operable to demodulate the periodic electric signal generated in the sensor winding to obtain a signal at the second frequency; and a signal processor operable to process the signal at the second frequency output by the demodulator in response to the first and second excitation signals being respectively applied to the first and second excitation windings to determine a first timing measurement representative of the relative position along the measurement direction of the first and second members, wherein the signal generator is further operable to generate a third excitation signal and to apply the first and third excitation signals to the first and second excitation windings respectively, the third excitation signal comprising a third periodic carrier signal at the first frequency modulated by a third periodic modulation signal at the third frequency, the third periodic modulation signal being in anti-phase with the second periodic modulation signal, wherein the signal processor is operable to process the signal at the second frequency output by the demodulator in response to the first and third excitation signals being respectively applied to the first and second excitation windings to determine a second timing measurement, and wherein the position sensor is operable to determine a position value using the first and second timing measurements.
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Specification