GAS CONCENTRATION DETECTOR

摘要

PROBLEM TO BE SOLVED: To reduce effect due to noise, and prevent the false detection of gas concentration. SOLUTION: The detection signal of a gas concentration sensor 100 is inputted to a sensor control circuit M10 and a control circuit M10 calculates oxygen concentration output and NOx concentration output from the sensor detection signal and also detects the element impedance of the gas concentration sensor 100. A heater control circuit M20 controls the passage of a current to a heater 103. Both of the sensor control circuit M10 and the heater control circuit M20 are built in a connector 300. The gas concentration sensor 100 and the sensor control circuit M10 in the connector 300 are electrically connected by a signal line H1 and the heater 103 and the heater control circuit M20 in the connector 300 are electrically connected by a signal line H2. The lengths of the signal lines H1, H2 from the gas concentration sensor 100 are prescribed corresponding to the level of the detection signal of the sensor 100 and, as the sensor signal becomes weak, the signal lines H1, H2 are shortened.