Capacitive based pressure sensor design
First Claim
1. A pressure transducer assembly, comprising:
- (A) a housing member defining an interior cavity, said housing member having a first coefficient of thermal expansion;
(B) a diaphragm mounted in said housing member and dividing said interior cavity into a first chamber and a second chamber, a portion of said diaphragm flexing in a first direction in response to a pressure in said first chamber being higher than a pressure in said second chamber, said portion of said diaphragm flexing in a second direction opposite said first direction in response to said pressure in said second chamber being higher than said pressure in said first chamber;
(C) an electrode disposed in said first chamber and joined to said housing member, said electrode including a conductor, said electrode having a second coefficient of thermal expansion, said second coefficient being different from said first coefficient; and
(D) a low thermal coefficient of expansion member rigidly connected to said housing member proximate where said electrode is joined to said housing member, said low thermal coefficient of expansion member having a third coefficient of thermal expansion, said third coefficient being lower than said first and second coefficients.
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Abstract
A pressure transducer assembly includes a first body, a second body, a diaphragm, and an electrode. The diaphragm is mounted between the first and second bodies. The first body and the diaphragm form a first chamber. The second body and the diaphragm form a second chamber. The electrode is disposed in the first chamber. A portion of the diaphragm flexes in a first direction in response to pressure in the first chamber being greater than pressure in the second chamber. A portion of the diaphragm flexes in a second direction, opposite the first direction, in response to pressure in the second chamber being greater than pressure in the first chamber. A capacitance between the electrode and the diaphragm is representative of a difference between the pressures in the first and second chambers. In some embodiments, the electrode is suspended from a hub and spoke mounting. In some embodiments the electrode is entirely metallic. In other embodiments, the electrode includes a ceramic disk with a conductive film formed on the disk and the disk is coupled to the housing with a ceramic rod. In some embodiments, the transducer also has a low thermal coefficient of expansion member connected to the housing for reducing warping in response to temperature changes. In additional embodiments, the disk includes a groove that reduces the effects of temperature variations on a ceramic electrode.
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Citations
29 Claims
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1. A pressure transducer assembly, comprising:
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(A) a housing member defining an interior cavity, said housing member having a first coefficient of thermal expansion;
(B) a diaphragm mounted in said housing member and dividing said interior cavity into a first chamber and a second chamber, a portion of said diaphragm flexing in a first direction in response to a pressure in said first chamber being higher than a pressure in said second chamber, said portion of said diaphragm flexing in a second direction opposite said first direction in response to said pressure in said second chamber being higher than said pressure in said first chamber;
(C) an electrode disposed in said first chamber and joined to said housing member, said electrode including a conductor, said electrode having a second coefficient of thermal expansion, said second coefficient being different from said first coefficient; and
(D) a low thermal coefficient of expansion member rigidly connected to said housing member proximate where said electrode is joined to said housing member, said low thermal coefficient of expansion member having a third coefficient of thermal expansion, said third coefficient being lower than said first and second coefficients. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A pressure transducer assembly comprising:
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(A) a body defining an interior cavity;
(B) a diaphragm mounted in said body and dividing said interior cavity into a first chamber and a second chamber, a portion of said diaphragm flexing in a first direction in response to a pressure in said first chamber being higher than a pressure in said second chamber, said portion of said diaphragm flexing in a second direction opposite said first direction in response to said pressure in said second chamber being higher than said pressure in said first chamber;
(C) an electrode mounting defining an aperture in said first chamber;
(D) a first electrode having a first conductive plate and a first support that are both metallic;
(E) a second electrode having a second conductive plate and a second support that are both metallic; and
(F) a dielectric material at least partially disposed in said aperture, said dielectric material joining said first electrode and said second electrode to said electrode mounting and insulating said first electrode from said second electrode. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A pressure transducer assembly comprising:
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(A) a housing member defining an interior cavity;
(B) a diaphragm mounted in said housing member and dividing said interior cavity into a first chamber and a second chamber, a portion of said diaphragm flexing in a first direction in response to a pressure in said first chamber being higher than a pressure in said second chamber, said portion of said diaphragm flexing in a second direction opposite said first direction in response to said pressure in said second chamber being higher than said pressure in said first chamber;
(C) an electrode disposed in said first chamber, including a ceramic disk having a conductor disposed on a first surface facing said diaphragm and a ceramic post joined to the ceramic disk at a second surface opposite said first surface; and
(D) a groove formed on said second surface around the ceramic post. - View Dependent Claims (21, 22, 23, 24, 25, 26)
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27. A pressure transducer assembly comprising:
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(A) a body having an interior surface and defining an interior cavity;
(B) a diaphragm mounted in said body and dividing said interior cavity into a first chamber and a second chamber, a portion of said diaphragm flexing in a first direction in response to a pressure in said first chamber being higher than a pressure in said second chamber, said portion of said diaphragm flexing in a second direction opposite said first direction in response to said pressure in said second chamber being higher than said pressure in said first chamber;
(C) a hub disposed in said first chamber;
(D) one or more spokes disposed in said first chamber, each of said spokes extending from a first end to a second end, said first end of each of said spokes contacting said interior surface, said second end of each of said spokes contacting said hub;
(E) a conductor disposed in said first chamber, said conductor being connected to said hub, a capacitance between said conductor and said diaphragm being representative of a difference between said pressures in said first and second chambers. - View Dependent Claims (28, 29)
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Specification