GAS CONCENTRATION DETECTOR

摘要

PROBLEM TO BE SOLVED: To always ensure the detection accuracy of gas concentration even if the temperature or flow velocity of the gas to be detected is changed. SOLUTION: A gas concentration sensor 100 has a pump cell 110 for detecting the concentration of oxygen in exhaust gas and a sensor cell 120 for detecting the concentration of NOx in the exhaust gas and a porous diffusion layer 101 is provided between the cells 110, 120. The sensor 100 is equipped with a heater 103 for heating the cells 110, 120. A control circuit 200 changes the voltage applied to the sensor cell alternately to detect the impedance of the sensor cell 120 and controls the passage of a current to the heater 103 on the basis of the detected impedance of the sensor cell 120.