| 摘要 |
PURPOSE:To enable the detection of gas with high sensitivity by using a plurality of detecting elements, by changing the frequency of a signal to one element when the detection of gas is performed by the other element, and enlarging thereby the dependency on the density of the output of the elements when the density is low. CONSTITUTION:Both of the resistance values of gas detecting elements 6 and 8 decrease under the presence of a gas to be detected. When the oscillation frequency of a CR oscillator 7 is f1 in an ambience wherein the density of gas is 300ppm, for instance, an output voltage is E1, since the element 8 is located in said ambience. Next, when the density turns to be 800ppm, the resistance value of the element 6 decreases to 1/k, the oscillation frequency changes from f1 to f2, the relation of the frequency of a signal impressed on the element 8 with the output voltage is transferred from a point (b) to a point (c), and the output voltage turns to be E3. As the result, the gas can be detected with high sensitivity, and the dependency on the density of gas also increases in a region wherein the density of the gas to be detected is low. |
