PURPOSE: To make comparative detection of good accuracy possible for a sensor having a wide range of resistance change by fixing reference potential roughly at the intermediate potential of an electric power source and operating the comparing potential side including sensor like pulses.
CONSTITUTION: The signal of a pulse oscillation part 10 is transmitted via resistances 11, 12 to a transistor 13 which is a switch means, and a resistance 25 is connected in parallel and disconnects to a resistance 24 connected in series to a sensor 5. Thereby, the comparative input potential of a comparator 14 is made pulse voltage. The reference potential of the comparator 14 is set roughly at the intermediate of source voltage E by resistances 26, 27. For example, when a combustion state is detected by using TiO2 as a sensor 5, the output of the comparator 14 is a low level until the ignition is detected but the sensor exposed to a high temp. atmosphere after the ignition decreases its resistance value owing to thermistor characteristics and a pulse signal is generated in the output of the comparator 14. Further when the sensor goes into a flame in the state of oxygen default, its resistance sharply decreases and the output of the comparator 14 is fixed at a high level.
MAEHARA NAOYOSHI
UNO TAKASHI
TANAKA EIICHI
KOMAI YUKIROU
