| 摘要 |
PURPOSE:To obtain the detected signal coping with the danger of CO gas, by alternately heating a gas sensor periodically in a high temperature region and in a low temperature region, converting the outputs of the gas sensor in the low temperature region into digital values, and adding the results. CONSTITUTION:A timer 2 is operated, e.g., at 150sec period. A heat cleaning signal is generated during the initial 60sec. A sensor 10 is heated, e.g., to 300(e). Then the sensor 10 is kept at 80 deg.C during the next 90sec. The electrical conductivity of the sensor at this temperature is proportional to the concentration of CO. Said electrical conductivity is detected by an operation amplifier 12, an inverter 14 and a power operation circuit 16. The output, which is proportional to the square of the concentration of CO, is obtained. The output of the power operation circuit 16 is converted into the digital value by an A/D converter, and the result is inputted to an adder 26. The effect of CO on the human body is determined by the product of the concentration, power and time. The output of the adder 26 corresponds to danger of CO. The output of the adder 26 is sent to a decoder 44, and a ventilating fan 48, an LED50 and a buzzer 52 are operated. |
