| 摘要 |
PROBLEM TO BE SOLVED: To provide a method that detects appropriate air fuel ratio while protecting a gas sensor.SOLUTION: An O2 sensor 17 has a sensor element 31 that comprises a solid electrolyte layer 32 and a pair of electrode 33, 34 provided at positions of holding the solid electrolyte layer 32; and outputs signals of electromotive force according to air fuel ratio of exhaust gas, with the exhaust gas of an engine as a detection object. A constant current circuit 43 supplying predetermined constant current is connected to the sensor element 31. A microcomputer 41 calculates the resistance value (element resistance) of the sensor element 31, and regulates constant current supplied by the constant current circuit 43 on the basis of the element resistance. |
