DETECTOR FOR COMPOSITE GAS

摘要

PURPOSE:To detect plural gases by controlling the temp. of a sensor with self- temp. control type heating elements which exhibit the heating temp. different from each other. CONSTITUTION:Au-Pt paste is printed and calcined at a specified interval on an alumina substrate 102 to form output electrodes 109, 110, and an SnO2 metallic oxide semiconductor is printed together with palladium salt thereon and is calcined, by which a gas-sensitive body 101 is formed. Two kinds of PTCs (ceramic semiconductors having a positive characteristic) are arrayed alternately and are printed on the rear of such sensor to form a PTC heater 103 for low temp. and a PTC heater 104 for high temp. The electrical conductivity of the metallic oxide semiconductors with various gases varies with temp. and therefore the detection of plural gases is made possible by changing over the heaters 103, 104.