| 摘要 |
PURPOSE:To carry out the detection of a gas accurately, by a method wherein first and second energizing powers are applied to the heater of a combustible gas detecting element successively and repeatedly and plural measured values in the second energizing power and the measured value in the first energizing power are operated. CONSTITUTION:A power energizing circuit 8 supplies first energizing power and second energizing power to the heater H of a combustible gas detecting element S alternately and repeatedly at a preset cycle. The resistance RS of the combustible gas detecting element S is detected from a resistor R1 connected thereto in series through switches SW1, SW2 and SW3 successively operated in synchronized relation to the variation of the energizing power of the power energizing circuit 8. SW1 is closed when the first energizing power is supplied while SW2 and SW3 are closed when the second energizing power is supplied. These detected signals are imparted to respective inputs of an operation amplifier A4 and the difference between the detected signal when the first energizing power is supplied and the average value of two detected signals when the second energizing power is supplied is operated. When this operated output exceeds a reference value, an alarm circuit operated. |
