Apparatus for and method of sensing a measured input
First Claim
1. Apparatus for use in sensing a measured input, comprising:
- a capacitor having a capacitance that varies non-linearly in response to the measured input, the capacitor comprising a first electrode, a second electrode and a gap defined by a space between the electrodes; and
circuitry that derives, from the capacitance, a signal that varies substantially linearly with the measured input, the circuitry comprising an amplifier comprising a first input terminal being in electrical communication with the first electrode, a second input terminal, and an output terminal being in electrical communication with the second electrode;
wherein the capacitance of the capacitor varies as an inverse of the gap of the capacitor, wherein the gap of the capacitor varies in response to changes in the measured input, wherein the capacitor is a first capacitor, wherein the circuitry is a first circuitry, and wherein the signal is derived from an output of the amplifier.
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Abstract
Apparatus is used in sensing a measured input. The apparatus includes a capacitor with a capacitance that varies non-linearly in response to the measured input, and a circuitry that derives, from the capacitance, a signal that varies substantially linearly with the measured input. The capacitor includes a first electrode, a second electrode, and a gap defined by a space between the electrode. The circuitry includes an amplifier with a first input terminal in electrical communication with the first electrode, a second input terminal, and an output terminal in electrical communication with the second electrode. The capacitance of the capacitor varies as an inverse of the gap of the capacitor, the gap of the capacitor varies in response to changes in the measured input, and the signal is derived from an output of the amplifier.
23 Citations
23 Claims
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1. Apparatus for use in sensing a measured input, comprising:
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a capacitor having a capacitance that varies non-linearly in response to the measured input, the capacitor comprising a first electrode, a second electrode and a gap defined by a space between the electrodes; and
circuitry that derives, from the capacitance, a signal that varies substantially linearly with the measured input, the circuitry comprising an amplifier comprising a first input terminal being in electrical communication with the first electrode, a second input terminal, and an output terminal being in electrical communication with the second electrode;
wherein the capacitance of the capacitor varies as an inverse of the gap of the capacitor, wherein the gap of the capacitor varies in response to changes in the measured input, wherein the capacitor is a first capacitor, wherein the circuitry is a first circuitry, and wherein the signal is derived from an output of the amplifier. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of generating a substantially linear signal in response to an input detected by a sensor, the sensor comprising a capacitance value that varies non-linearly in response to the input, the method comprising the steps of:
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in response to a sensor input, varying a gap of a first sensing capacitor connected in a feedback circuit of a first amplifier;
in response to the sensor input, varying a gap of a second sensing capacitor connected in a feedback circuit of a second amplifier; and
generating a substantially linear signal comprising a sum of an output of the first amplifier and an output of the second amplifier, wherein capacitance of the first capacitor varies as an inverse of the gap of the first sensing capacitor, and wherein capacitance of the second capacitor varies as an inverse of the gap of the second sensing capacitor. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. A linear open loop micro electro-mechanical system comprising a capacitive pickoff, the system comprising:
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a first amplifier comprising a first input terminal, a second input terminal, and an output terminal;
a second amplifier comprising a first input terminal, a second input terminal, and an output terminal;
a first capacitor comprising a moveable electrode and a fixed electrode;
a second capacitor comprising a moveable electrode and a fixed electrode;
a first proof mass comprising the movable electrode of first capacitor; and
a second proof mass mechanically coupled to the first proof mass, the second proof mass comprising the movable electrode of second capacitor, wherein one of the moveable electrode and the fixed electrode of the first capacitor are in electrical communication with the output terminal of the first amplifier, and wherein a substantially linear signal representative of a measured input is generated in response to changes in a capacitance of the first capacitor and changes in a capacitance of the second capacitor.
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20. A method of improving linearity of an output signal generated in response to a non-linear capacitive input, the method comprising the steps of:
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connecting a first variable capacitance responsive to a sensor input in a feedback circuit of a first amplifier;
connecting a second variable capacitance responsive to the sensor input in a feedback circuit of a second amplifier; and
generating an output signal by summing an output of the first amplifier and an output of the second amplifier.
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21. Apparatus for use in sensing a measured input, comprising:
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an amplifier having an output and an input, the output and input defining a feedback path between the output and the input;
a sensor in the feedback path, the sensor comprising a capacitor comprising a capacitance that varies non-linearly with the measured input; and
circuitry that derives, from the output of the amplifier, a signal that varies substantially linearly with the measured input. - View Dependent Claims (22, 23)
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Specification