| 摘要 |
PURPOSE:To enable the detection of concentrations of serveral kinds of combustible gases separately corresponding thereto by a method wherein a heater is energized sequentially and repeatedly at a plurality of power values, according to which the resistance values of combustible gas detection elements are computed and a level discrimination is made based on the results of the computation. CONSTITUTION:A heater H of combustible gas detector elements S is energized at a fixed voltage E by a D.C. power source 1. A resistance R1 is connected in series to a resistance RS given equivalently of the detection elements S which is retained at a constant temperature heated by the heater H. Output voltage V of the resistance R1 depends on the resistance RS, hence the concentration of the combustible gases. In the detection element S, electrodes 3 and 4 are fixed at a space on a cylindrical body 2 made of electrically insulating ceramics or the like and covered with a metal oxide semiconductor 5 such as SnO2. The heater H inserted into the cylindrical body 2 is energized at a fixed 4.5V normally when the concentration of the gas is low. In an abnormal case, a voltage of 5V and 4.5V is applied alternately in a cyclical manner and changes in the resistance value are computed. A level discrimination is made based on the results of the computation to detect concentrations of the combustible gases. |
