Electricity: electrical systems and devices – Electrostatic capacitors – Variable
Patent
1987-03-17
1988-06-21
Levy, Stewart J.
Electricity: electrical systems and devices
Electrostatic capacitors
Variable
H01G 500
Patent
active
047528559
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 BaRuO.sub.3, V.sub.2 O.sub.5 and Na.sub.2 WO.sub.4, 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.degree. C. to 850.degree. 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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Leppavuori, "New Thick Film Sensors", Electrocomponent Science and Technology, vol. 6, pp. 193-197, 1980.
Jones et al., "A Barium Fluoride Film Hygrometer Element", Journal of Geophysical Research, vol. 65, No. 7, Jul. 1960.
"Thick Film Circuits: Present State and Future Development", J. Novotny, Electrocomponent Science and Technology, 1981, vol. 9, pp. 131-137.
De La Prieta Claudio
Fedter Horst
Grunwald Werner
Nolting Peter
Schmid Kurt
Levy Stewart J.
Raevis Robert R.
Robert & Bosch GmbH
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