Capacitive pressure transducer
First Claim
1. A capacitive pressure transducer comprisinga pressure responsive movable capacitor plate assembly including a metal diaphragm attached to support means at its periphery,a fixed hat-shaped capacitor plate having a central surface closely spaced from the diaphragm to form with said diaphragm a capacitor of substantial value which is variable according to the position of the diaphragm and further having a peripheral surface widely spaced from the said support means to form a capacitor of fixed capacitance which is small relative to the said variable capacitance,an insulating layer of metal oxide formed on at least one of the diaphragms and the fixed capacitor plate for preventing electrical contact therebetween,an insulating spacer between the peripheral surface of the fixed capacitor plate and the said assembly,conductive leads connected to the fixed capacitor plate and the movable capacitor plate assembly, andmeans for applying a pressure differential across the diaphragm whereby when pressure is applied the diaphragm flexes to vary the capacitance according to the value of the pressure differential.
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Accused Products
Abstract
A variable capacitor includes a metal diaphragm arranged to flex in response to an applied pressure differential serving as a movable capacitor plate and a fixed capacitor plate closely spaced from the diaphragm. At least one of the two capacitor plates has an insulating layer of metal oxide formed thereon to prevent electrical contact therebetween. By making the capacitor plate of an iron-chrome-aluminum alloy and heating the capacitor plate, an aluminum oxide layer is formed thereon. The fixed capacitor plate is formed in a hat-shaped configuration with the brim portion spaced far from the diaphragm by an insulating spacer to minimize the fixed capacitance around the edge of the capacitor assembly.
11 Citations
3 Claims
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1. A capacitive pressure transducer comprising
a pressure responsive movable capacitor plate assembly including a metal diaphragm attached to support means at its periphery, a fixed hat-shaped capacitor plate having a central surface closely spaced from the diaphragm to form with said diaphragm a capacitor of substantial value which is variable according to the position of the diaphragm and further having a peripheral surface widely spaced from the said support means to form a capacitor of fixed capacitance which is small relative to the said variable capacitance, an insulating layer of metal oxide formed on at least one of the diaphragms and the fixed capacitor plate for preventing electrical contact therebetween, an insulating spacer between the peripheral surface of the fixed capacitor plate and the said assembly, conductive leads connected to the fixed capacitor plate and the movable capacitor plate assembly, and means for applying a pressure differential across the diaphragm whereby when pressure is applied the diaphragm flexes to vary the capacitance according to the value of the pressure differential.
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2. A capacitive pressure transducer comprising
a pressure responsive movable capacitor plate assembly including a metal diaphragm welded to metal support means at its periphery, the diaphragm comprising an iron-chromium-aluminum alloy with its surface oxidized to form thereon an insulating coating of aluminum oxide, a fixed hat-shaped capacitor plate having a central surface closely spaced from the diaphragm to form with said diaphragm a capacitor of substantial value which is variable according to the position of the diaphragm and protected from electrical contact therewith by the said insulating oxide coating, the fixed capacitor plate further having a peripheral surface widely spaced from the said support means to form a capacitor of fixed capacitance which is small relative to the said variable capacitance, an insulating spacer between the peripheral surface of the fixed capacitor plate and the said assembly, conductive leads connected to the fixed capacitor plate and the movable capacitor plate assembly, and means for applying a pressure differential across the diaphragm whereby when pressure is applied the diaphragm flexes to vary the capacitance according to the value of the pressure differential.
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3. A capacitive pressure transducer comprising
cup-shaped support means having an annular rim about its opening a pressure responsive movable capacitor plate assembly including the said support means and a metal diaphragm attached and sealed to the annular rim of the support means to define a closed chamber, a gas within the closed chamber at a preset reference pressure, the diaphragm having an insulating layer of metal oxide formed on the surface thereof, a fixed hat-shaped capacitor plate mounted outside the closed chamber and having a central surface closely spaced from the diaphragm to form with said diaphragm a capacitor of substantial value which is variable according to the position of the diaphragm and protected from electrical contact therewith by the said insulating oxide layer, the fixed capacitor plate further having a peripheral surface widely spaced from the said support means to form a capacitor of fixed capacitance which is small relative to the said variable capacitance, an insulating spacer between the peripheral surface of the fixed capacitor plate and the said assembly, conductive leads connected to the fixed capacitor plate and the movable capacitor plate assembly, and means for applying a pressure on the diaphragm outside the closed chamber whereby when pressure is applied the diaphragm flexes to vary the capacitance according to the value of the applied pressure.
Specification
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Current AssigneeGeneral Motors Corporation (Motors Liquidation Co. GUC Trust)
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Original AssigneeGeneral Motors Corporation (Motors Liquidation Co. GUC Trust)
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InventorsMann, Gamdur S.
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Primary Examiner(s)Goldberg, E. A.
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Application NumberUS05/961,995Time in Patent Office512 DaysField of Search361/278, 361/283, 73/718, 73/724US Class Current361/283.4CPC Class CodesG01L 9/0072 using variations in capacit...
