SENSING CONTROLLER FOR INFLAMMABLE GAS

PURPOSE:To hold the level of the detection signal of a gas sensor optimum by providing a means which compares a detection signal of flammable gas thickness with a detection level signals which is settable in plural stages and sets the detection level automatically. CONSTITUTION:The detection signal of the gas sensor 1 which detects the air in a car being tainted by smoke of cigarettes is inputted to a detection level setting circuit 2 through a buffer amplifier 3. This detection level setting circuit 2 is provided with a detection signal level decision part 21, detection level setting part 22, and level difference detection part 24. This detection level setting circuit 2 decides the difference between the set detection level and the level of the detection signal and re-sets the detection level when the difference exceeds a specific value. Namely, a new detection level is set automatically when the difference between the detection signal of target gas to be detected and the set detection level is larger than the specific value, and when miscellaneous gases do not vary beyond a specific width. Therefore, the detection level is adjusted automatically and malfunction is eliminated.