Sensor for detecting reducing gases - in which resistance of a semiconducting oxide varies with concn. of reducing gas

摘要

Sensor for reducing gases, the novelty being the use of a tubular heating element using a multi-turn coil of wire coated by a refractory material to prevent adjacent turns from touching each other. In the middle of the tube is a sensor in which electrical leads are partly embedded, and the sensor does not touch the heating coil, which is designed to heat the sensor by radiation. The refractory material is pref. applied at two locations on each turn of wire, or it may completely cover the coil to form a tube. The coil of wire is pref. made from (a) Pt-Ir; or (b) Fe-Cr-Al alloy. The refractory material pref. consists of an inorganic binder, whereas the sensor is pref. a semiconducting metal oxide with a specific resistance which alters in the presence of a reducing gas. In the pref. mfg. process a conducting laminar frame is used with a straight base and two pairs of projecting parts, one pair being used to support the heating coil, the other pair to support the sensor via its electric leads. Accurate and reliable measurement of the concn. of a reducing gas even when the temp. in the vicinity of the sensor varies, as the heater coil keeps the sensor at a constant temp., necessary for accurate measurement.