| 摘要 |
PURPOSE:To enable both propane gas and methane gas to be detected by making the gas sensor in the bridge circuit act as a contact burn type device for propane gas, and making it act as a heat conducting type device for methane gas. CONSTITUTION:In the gas detecting bridge circuit, the gas sensor R1 is constituted by applying a high-melting-point oxide such as TiO2ZnO2, HfO2, NiO2, and the like as a catalyst on a platinum coil. When said sensor R1 is heated to 350-400 deg.C, even minute amount of propane gas, butane gas, and the like is reacted, the temperature of the platinum wire is increased, the resistance thereof is increased, and an output voltage is generated across A and B. If said high-melting-poing oxide is used as the catalyst, the reaction is not caused for methane gas, and the action as the contact burning is not carried out. Since heat conductivity of methane gas is higher than that of the air, the sensor R1 is cooled, the resistance is decreased, and the output voltage, whose polarity is opposite to that in the case of the contact burning method, is generated. |
