Wide dynamic range capacitive transducer
First Claim
1. A variable area capacitor comprising:
- a. a flexible electrode responsive to a physical effect;
b. a rigid electrode with a three-dimensional surface contour facing said flexible electrode;
c. a dielectric spacer sandwiched between said flexible electrode and said rigid electrode;
d. said dielectric spacer maintains a substantially fixed capacitance spacing between regions of mutually opposed areas of said rigid electrode and said flexible electrode, said regions of said fixed capacitance spacing increasing as said flexible electrode deflects in response to said physical effect;
e. said surface contour having a shape that provides a substantially linear change in capacitance of said variable area capacitor in response to said physical effect.
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Abstract
A variable area capacitor with a flexible electrode responsive to a physical effect and a rigid electrode with a predetermined surface contour. The surface contour is dimensioned to provide a specific change in capacitance with deflection of the flexible electrode. A thin dielectric layer maintains a substantially fixed spacing between the two electrodes. Preferred embodiments include a pressure sensor, microphone and accelerometer. A differential transconductance amplifier detects changes of the variable capacitor in a low-impedance, bridge-like circuit and feeds back current to balance the bridge. The voltage that controls the feedback current is proportional to capacitance over a wide dynamic range.
118 Citations
36 Claims
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1. A variable area capacitor comprising:
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a. a flexible electrode responsive to a physical effect; b. a rigid electrode with a three-dimensional surface contour facing said flexible electrode; c. a dielectric spacer sandwiched between said flexible electrode and said rigid electrode; d. said dielectric spacer maintains a substantially fixed capacitance spacing between regions of mutually opposed areas of said rigid electrode and said flexible electrode, said regions of said fixed capacitance spacing increasing as said flexible electrode deflects in response to said physical effect; e. said surface contour having a shape that provides a substantially linear change in capacitance of said variable area capacitor in response to said physical effect. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A variable area capacitor comprising:
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a. a flexible electrode responsive to a physical effect; b. a rigid electrode with a surface contour facing said flexible electrode; c. a dielectric spacer sandwiched between said rigid electrode and said flexible electrode that extends at least up to an inflection point of said surface contour; d. said dielectric spacer maintains a substantially fixed capacitance spacing between regions of mutually opposed areas of said rigid electrode and said flexible electrode, said regions of said fixed capacitance spacing increasing in extent as said flexible electrode deflects in response to said physical effect. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. A variable area capacitor constructed to avoid a saturation-type of nonlinear capacitance response comprising:
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a. a flexible electrode responsive to a physical effect; b. a rigid electrode with a surface contour facing said flexible electrode; c. a dielectric spacer sandwiched between said rigid electrode and said flexible electrode; d. said dielectric spacer maintains a substantially fixed capacitance spacing between regions of mutually opposed areas of said rigid electrode and said flexible electrode, said regions of said fixed capacitance spacing increasing in extent as said flexible electrode deflects in response to said physical effect; e. said surface contour having a shape that provides an increase in said regions of said fixed capacitive spacing at least up to an inflection point on said surface contour, whereby said capacitance response of said variable area capacitor is prevented from reaching a level of saturation. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36)
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Specification