Method and apparatus for self-calibration of capacitive sensors
First Claim
1. A method for determining operational characteristics of capacitive sensors, comprising the steps of:
- providing at least one capacitive sensor, said capacitive sensor having plates, said plates including a suspended element and a pick-up plate, said suspended element capable of displacement relative to said pick-up plate by application of a force, said displacement and said force related by a spring constant;
applying an AC input signal to one of said plates, providing force between said plates, said force capable of variation, measuring a displacement current signal or a signal derived from said displacement current which is induced by application of said AC input signal to one of said plates, and determining at least one operational characteristic of said capacitive sensor from parameters including said measured displacement current signal or a signal derived from said displacement current signal.
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Abstract
A method for determining operational characteristics of capacitive sensors adapted for self-calibration includes the steps of providing at least one capacitive sensor having a suspended element and a pick-up plate. An AC input signal is applied to one of the plates, while force is provided between the plates, the force capable of variation. At least one operational characteristic of capacitive sensors can be determined, such as the suspended element spring constant and the gap distance between the plates. A capacitive sensor system adapted for self-calibration includes at least one capacitive sensor having a suspended element and a pick-up plate, a self-testing and calibration network, and a structure for generating force between the plates, the force capable of variation.
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Citations
48 Claims
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1. A method for determining operational characteristics of capacitive sensors, comprising the steps of:
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providing at least one capacitive sensor, said capacitive sensor having plates, said plates including a suspended element and a pick-up plate, said suspended element capable of displacement relative to said pick-up plate by application of a force, said displacement and said force related by a spring constant;
applying an AC input signal to one of said plates, providing force between said plates, said force capable of variation, measuring a displacement current signal or a signal derived from said displacement current which is induced by application of said AC input signal to one of said plates, and determining at least one operational characteristic of said capacitive sensor from parameters including said measured displacement current signal or a signal derived from said displacement current signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method for operating capacitive sensors, comprising the steps of:
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providing at least one capacitive sensor and at least one self-testing and calibration network, said capacitive sensor having plates, said plates including a suspended element and a pick-up plate, said suspended element capable of displacement relative to said pick-up plate by application of a force, said displacement and said force related by a spring constant;
applying an AC input signal to one of said plates, providing force between said plates, said force capable of variation, measuring a displacement current signal or a signal derived from said displacement current which is induced by application of said AC input to one of said plates, and determining at least one operational characteristic of said capacitive sensor from parameters including said measured displacement current signal or a signal derived from said displacement current signal. - View Dependent Claims (19, 20, 21, 22, 23)
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24. A method for determining gap distances between capacitive sensor plates, comprising the steps of:
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providing at least one capacitive sensor, said capacitive sensor having plates, said plates including a suspended element and a pick-up plate, said suspended element capable of displacement relative to said pick-up plate by application of a force, said displacement and said force related by a spring constant;
applying an AC input signal to one of said plates for generating a displacement current signal across said capacitive sensor;
measuring said displacement current signal or a signal derived from said displacement current, and determining a gap distance between said plates from said resulting output signal from parameters including said measured displacement current signal or a signal derived from said displacement current signal. - View Dependent Claims (25, 26, 27, 28, 29, 30)
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31. A method for determining at least one operational charactertistic of capacitive sensors, comprising the steps of:
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providing at least one capacitive sensor, said capacitive sensor having plates, said plates including a suspended element and a pick-up plate, said suspended element capable of displacement relative to said pick-up plate by application of a force, said displacement and said force related by a spring constant;
providing force between said plates, said force capable of variation;
applying an AC input signal to one of said plates to produce a displacement current through said capacitive sensor;
directing an optical beam onto said suspended element to generate a reflected beam;
detecting said reflective optical beam, and determining at least one operational characteristic of said capacitive sensor from parameters including said measured displacement current signal or a signal derived from said displacement current signal. - View Dependent Claims (32, 33)
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34. A capacitive sensor system, comprising:
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at least one capacitive sensor, said capacitive sensor having plates, said plates including a suspended element and a pick-up plate, said suspended element capable of displacement relative to said pick-up plate by application of a force, said displacement and said force related by a spring constant;
at least one self-testing and calibration network switchably connected to said capacitive sensor, said self-testing and calibration network including a processor, structure for generation of force between said plates, said force capable of variation, structure for applying an AC input signal to one of said plates, and structure for measuring a displacement current signal or a signal derived from said displacement current which is induced by application of said AC input signal across said capacitive sensor. - View Dependent Claims (35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48)
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Specification