Capacitive pressure sensor having encapsulated resonating components
First Claim
1. A capacitive pressure sensor comprising:
- an elastic member having a first side and a second side, said elastic member comprising a conductive surface at said first side;
a support member supporting an edge of said elastic member, wherein said support member and said elastic member separate two pressure regions across said elastic member, a first pressure region contiguous with said first side of said elastic member and a second pressure region contiguous with said second side of said elastic member, wherein a central portion of said elastic member is displaceable along an axis in response to a pressure differential between said two pressure regions across said elastic member;
an electrically conductive, capacitive plate disposed substantially adjacent to said elastic member so as to define a gap between said first side of said elastic member and said capacitive plate, wherein said gap, capacitive plate and elastic member define a capacitor having a characteristic capacitance; and
, an elongated electrical conductor characterized by an associated inductance value, said conductor being fixedly attached, along a substantial portion of its entire length, to said capacitive plate;
wherein said capacitor and said electrical conductor are electrically coupled to form a resonant tank circuit;
wherein said gap varies as a predetermined function of the pressure differential between said two pressure regions across said elastic member so as to vary said characteristic capacitance, and consequently vary a resonant frequency of said tank circuit.
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Accused Products
Abstract
A capacitive pressure sensor for measuring a pressure applied to an elastic member includes a capacitive plate disposed adjacent to the elastic member so as to define a gap between a planar conductive surface of the elastic member and a corresponding planar surface of the capacitive plate. The gap, capacitive plate and elastic member together define a capacitor having a characteristic capacitance. The sensor further includes an elongated electrical conductor characterized by an associated inductance value. The conductor is fixedly attached to and electrically coupled with the capacitive plate. The gap between the capacitive plate and the elastic member varies as a predetermined function of the pressure applied to the elastic member so as to vary the characteristic capacitance. The capacitor and the electrical conductor together form an electrical resonator having a characteristic resonant frequency. Varying the capacitance of this tank circuit varies the resonant frequency of the tank circuit. Thus, the resonant frequency of the tank circuit is indicative of the pressure applied to the elastic member. The close physical proximity of the capacitor and the electrical conductor equalizes the effects of environmental influences such as temperature variations, vibration and shock, thus making such effects more predictable.
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Citations
42 Claims
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1. A capacitive pressure sensor comprising:
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an elastic member having a first side and a second side, said elastic member comprising a conductive surface at said first side;
a support member supporting an edge of said elastic member, wherein said support member and said elastic member separate two pressure regions across said elastic member, a first pressure region contiguous with said first side of said elastic member and a second pressure region contiguous with said second side of said elastic member, wherein a central portion of said elastic member is displaceable along an axis in response to a pressure differential between said two pressure regions across said elastic member;
an electrically conductive, capacitive plate disposed substantially adjacent to said elastic member so as to define a gap between said first side of said elastic member and said capacitive plate, wherein said gap, capacitive plate and elastic member define a capacitor having a characteristic capacitance; and
,an elongated electrical conductor characterized by an associated inductance value, said conductor being fixedly attached, along a substantial portion of its entire length, to said capacitive plate;
wherein said capacitor and said electrical conductor are electrically coupled to form a resonant tank circuit;
wherein said gap varies as a predetermined function of the pressure differential between said two pressure regions across said elastic member so as to vary said characteristic capacitance, and consequently vary a resonant frequency of said tank circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A capacitive pressure sensor comprising:
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an elastic member having a first side and a second side, said elastic member comprising a conductive surface at said first side;
a housing for supporting said elastic member, said elastic member and said housing forming a first pressure region contiguous with said first side of said elastic member, and a second pressure region contiguous with said second side of said elastic member, wherein said first pressure region and said second pressure region generate a pressure differential across said elastic member, wherein a central portion of said elastic member is displaceable along an axis in response to the pressure differential;
a capacitive plate disposed substantially parallel to said elastic member so as to define a gap between said conductive surface and a corresponding surface of said capacitive plate, said gap, capacitive plate and elastic member defining a capacitor having a characteristic capacitance; and
,an elongated electrical conductor characterized by an inductance value and fixedly attached, along a substantial portion of its entire length, to said capacitive plate;
wherein said capacitor and said electrical conductor are electrically coupled to form a resonant tank circuit;
wherein said gap varies as a predetermined function of said pressure differential across said elastic member so as to vary said characteristic capacitance, and consequently vary a resonant frequency of said tank circuit. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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32. A sensor for measuring a pressure differential across an elastic member having at least a first substantially planar, electrically conductive surface and being supported by at least one edge, comprising:
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a housing for supporting said elastic member by said edge, forming (i) a first pressure region disposed on a first side of said elastic member corresponding to said first planar surface, and (ii) a second pressure region disposed on a second side of said elastic member opposite said first side, wherein said first pressure region and said second pressure region generate said pressure differential across said elastic member, and wherein a central portion of said elastic member is displaceable along an axis in response to said pressure differential;
an electrically conductive, capacitive plate disposed substantially adjacent to said elastic member so as to define a gap between said first planar surface and a corresponding planar surface of said capacitive plate, said gap, capacitive plate and elastic member defining a capacitor having a characteristic capacitance; and
,an elongated electrical conductor characterized by an associated inductance value, disposed, along a substantial portion of its entire length, upon a substrate in a substantially planar configuration;
wherein said capacitor and said electrical conductor are electrically coupled to form a resonant tank circuit;
wherein said gap varies as a predetermined function of said pressure differential so as to vary said characteristic capacitance, and consequently vary a resonant frequency of said tank circuit. - View Dependent Claims (33, 34, 35, 36, 37, 38, 39, 40, 41, 42)
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Specification