| 摘要 |
PURPOSE:To maintain detection sensitivity stably for a long period of time by using an oxide semiconductor as a combustible gas sensitive element and providing the 1st heater which heats the sensitive element and the 2nd heater which burns and removes the combustibles in the gas in the stage of compensating the resistance of the sensitive element periodically. CONSTITUTION:In a combustible gas sensor such as municipal gas, propane gas, H2, CO and the like, a gas sensitive element 1 is made of an oxide semiconductor such as a sintered body of SnO2 or a sintered body consisting of ZnO added with PdCl and is heated with the 1st heater 2. To remove combustible gas, by the 2nd heater 3, a heater 3 is formed of a wire net (about 100mu hole diameter) made of Pt or the like, and a wire net for explosion prevention is provided in such a way as to cover the heater 3. Such heaters 2, 3 and the element 1 are provided on an insulation characteristic pedestal 5, and lead wires 6 are provided to each of these. The 2nd heater 3 is used once every half year or one year, and a compensation circuit which corrects the output value of the element 1 of the resistance varying with time to the output value at the initial setting is provided. Thereby, the detection sensitivity of the element 1 maintained stably without replacement. |
