PURPOSE: To obtain a small-sized gas kind discriminating sensor which properly discriminates between several kinds of gas having nearly the same mass by installing a base plate having a hollow part, heat insulating film whose periphery is supported on the base plate, covering the hollow part, and a thermistor. ;CONSTITUTION: A gas kind sensor is equipped with a base plate 2 having a hollow part 3 and a heat insulating thin film 4 whose peripheray is supported on the base plate 2, covering the hollow part 3, and a thermistor 5 is installed on the region covering the hollow part 3 of the heat insulating thin film 4. The sensor 1 is installed in a decompressed environment, and the thermistor 5 is put into electric conduction, and set in a heat generation state. While, the calorific heat is determined by the thermal conductivity of the gas free particle existing in the hollow part 3, and the thermistor 5 is set at the temperature determined by the heat generation quantity and the calorific heat. While, the thermal conductivity of the free particle is different according to the kind of gas, and if the kind of the gas existing in the hollow part 3 changes, the calorific heat varies, and the temperature of the thermistor 5 varies. When the temperature of the thermistor 5 varies, the resistance value varies. Accordingly, the resistance value of the thermistor 5 varies according to the kind of the gas existing in the hollow part 3, and the kind of the gas can be known on the basis of the resistance value of the thermistor 5.;COPYRIGHT: (C)1994,JPO&Japio
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