SENSOR AND METHOD OF SENSING
First Claim
1. A sensor for determining the presence of an object from a change in a capacitance of a sensing element, the sensor comprisinga capacitance measurement circuit operable to perform measurement cycles to measure a capacitance of the sensing, element, anda controller circuit operableto detect a periodic noise signal induced on the sensing element,to determine a first part of a repeating pattern of the periodic noise signal, which causes a change in an amount of charge present on the sensing element, which affects the measurement of the capacitance of the sensing element by the capacitance measurement circuit,to determine a second part of the repeating pattern of the periodic noise signal, which does not cause a change in the amount of charge present on the sensing element, andto control the measurement cycles of the capacitance measurement circuit to perform the measurement cycles during the second part of the periodic noise signal and not to perform the measurement cycles during the first part of the periodic noise signal.
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Accused Products
Abstract
A sensor is arranged to determine the presence of an object from a change in a capacitance of a sensing element. The sensor includes a capacitance measurement circuit operable to perform measurement cycles to measure a capacitance of the sensing element, and a controller circuit. The control circuit is operable to detect a periodic noise signal induced on the sensing element, to determine a first part, of a repeating pattern of the periodic noise signal, which causes a change in an amount of charge present on the sensing element, which affects the measurement of the capacitance of the sensing element by the capacitance measurement circuit, to determine a second part of the repeating pattern of the periodic noise signal, which does not cause a change in the amount of charge present on the sensing element, and to control the measurement cycles of the capacitance measurement circuit to perform the measurement cycles during the second part of the periodic noise signal and not to perform the measurement cycles during the first part of the periodic noise signal.
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Citations
22 Claims
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1. A sensor for determining the presence of an object from a change in a capacitance of a sensing element, the sensor comprising
a capacitance measurement circuit operable to perform measurement cycles to measure a capacitance of the sensing, element, and a controller circuit operable to detect a periodic noise signal induced on the sensing element, to determine a first part of a repeating pattern of the periodic noise signal, which causes a change in an amount of charge present on the sensing element, which affects the measurement of the capacitance of the sensing element by the capacitance measurement circuit, to determine a second part of the repeating pattern of the periodic noise signal, which does not cause a change in the amount of charge present on the sensing element, and to control the measurement cycles of the capacitance measurement circuit to perform the measurement cycles during the second part of the periodic noise signal and not to perform the measurement cycles during the first part of the periodic noise signal.
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10. A method of determining the presence of an object from a change in a capacitance of a sensing element, the method comprising
detecting a periodic noise signal induced on the sensing element, determining a first part of a repeating pattern of the periodic noise signal, which causes a change in an amount of charge present on the sensing element, which affects the measurement of the capacitance of the sensing element, determining a second part of the repeating pattern of the periodic noise signal, which does not cause a change in the amount of charge present on the sensing element, performing measurement cycles to measure a capacitance of the sensing element during the second part of the periodic noise signal and not performing the measurement cycles during the first part of the periodic noise signal.
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19. A controller for sensing the presence of an object from a change in an amount of charge present on a sensing element, the controller being operable
to detect a periodic noise signal induced on the sensing element, to determine a first part of a repeating pattern of the periodic noise signal, which causes a change in an amount of charge present on the sensing element, which affects a measurement of a capacitance of the sensing element, to determine a second part of the repeating pattern of the periodic noise signal, which does not cause a change in the amount of charge present on the sensing element, and to control measurement cycles of a capacitance measurement circuit to perform the measurement cycles during the second part of the periodic noise signal and not to perform the measurement cycles during the first part of the periodic noise signal.
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21. An apparatus for determining the presence of an object from a change in a capacitance of a sensing element, the apparatus comprising
means for detecting a periodic noise signal induced on the sensing element, means for determining, a first part of a repeating pattern of the periodic noise signal, which causes a change in an amount of charge present on the sensing element, which affects the measurement of the capacitance of the sensing element, means for determining a second part of the repeating pattern of the periodic noise signal, which does not cause a change in the amount of charge present on the sensing element, means for performing measurement cycles to measure a capacitance of the sensing element during the second part of the periodic noise signal and not performing the measurement cycles during the first part of the periodic noise signal.
Specification