Capacitative-type humidity sensing element and system, and method of manufacture
First Claim
1. A method of making a capacitative-type humidity sensor, to measure relative humidity by change of capacitance between two electrodes located on a substrate, in which a ceramic material is applied between the electrodes,comprising the steps ofhomogenizing a mixture of BaRuO3, V2 O5 and Na2 WO4 ;
- presintering said homogenized mixture;
adding the presintered mixture to a glass paste to form an application paste;
applying the application paste between said two electrodes; and
firing the substrate with the electrodes and the application paste to form said ceramic material.
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Accused Products
Abstract
A humidity sensor, and particularly a sensor which can distinguish between low humidity values, for example below 60% humidity, and high humidity values, for example 90% humidity and thereover, and change the capacitance between output electrodes (5, 6) is formed by applying interdigited comb electrodes (1, 2) on a substrate (8) and applying over the substrate a ceramic mass formed of BaRuO3, V2 O5 and Na2 WO4, with a weight relationship of (1±0.4):(1±0.4):(0.6±0.2) preferably 1:1:0.6. The sensor is made by first making a powder of the components, mixing it with a glass paste and, if necessary, a thinner, and applying the resulting paste by thick-film technology to a ceramic substrate on which the electrodes have been applied, and then firing the substrate at a temperature of between 550° C. to 850° C. The sensor is particularly sensitive in humidity ranges above 60% relative humidity and is especially suitable to sense fogging of the inside of a windshield of an automotive vehicle.
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Citations
16 Claims
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1. A method of making a capacitative-type humidity sensor, to measure relative humidity by change of capacitance between two electrodes located on a substrate, in which a ceramic material is applied between the electrodes,
comprising the steps of homogenizing a mixture of BaRuO3, V2 O5 and Na2 WO4 ; -
presintering said homogenized mixture; adding the presintered mixture to a glass paste to form an application paste; applying the application paste between said two electrodes; and firing the substrate with the electrodes and the application paste to form said ceramic material. - View Dependent Claims (2, 3, 4, 6)
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5. The method of claim 5, wherein the substrate (8) comprises Al2 O3, and the electrodes are applied to a surface thereof in interdigited or double-comb form.
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7. A mixture for manufacturing a capacitative-type humidity sensor, wherein the mixture is applied between two capacitative measuring electrodes and fired, said mixture comprising
a mixture of ceramic material consisting essentially of BaRuO3, V2 O5 and Na2 WO4 with glass paste.
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10. A capacitative-type relative humidity sensor
comprising a ceramic substrate; -
two interdigited double-comb electrodes applied to the substrate; and a homogenized thick-film ceramic located between said electrodes comprising a fired mixture of BaRuO3, V2 O5 and Na2 WO4. - View Dependent Claims (11, 12)
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13. In an automotive vehicle, a capacitative-type humidity sensor positioned within the passenger copartment of the vehicle, said humidity sensor comprising
a ceramic substrate plate; -
interdigited comb-like electrodes applied to the surface of said plate; and a ceramic material on said substrate plate between said electrodes, said ceramic material comprising a fired powder mixture of BaRuO3, V2 O5 and Na2 WO4, and a glass paste to form said ceramic material, which changes the capacitance between the electrodes upon change in ambient humidity in said passenger compartment. - View Dependent Claims (14, 15, 16)
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Specification