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Gas sensor with temp. gradient region useful in portable battery powered detectors - has temp. sensors provided with exothermic reaction catalyst
Gas sensor with temp. gradient region useful in portable battery powered detectors - has temp. sensors provided with exothermic reaction catalyst
Sensor structure includes heating element (4) on a substrate (1) to enclose an area (5) in which a temp. gradient is produced during heating element operation. Two or more temp. sensors (6,7), each arranged along an isotherm, are provided on the enclosed area (5) and are provided with a catalyst, at the surface of which a gas reacts with evolution of heat deflected by the temp. sensors (6,7). Heating element (4) and the temp. sensors (6,7) are thermally insulated from the substrate (1). Temp. sensors (6,7) are pref. in the form of thin film resistors having an electrical resistance which varies markedly in the detection temp. range. Sensors (6,7) may be provided with layers of pref. different catalyst materials or may consist of electrically conductive catalyst material. Pref. the heating element (4) is also in the form of a thin film resistor. Substrate (1) pref. consists of Si and is thermally insulated from the heating element (4) and the temp. sensors (6,7) pref. by provision of a cavity (2) and an insulating membrane e.g. of Si3N4. USE/ADVANTAGE - Gas sensor structure is useful in portable, battery powered detectors for detecting e.g. combustible gases and can detect several gases simultaneously and is suitable for use in portable equipment
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