| 摘要 |
PROBLEM TO BE SOLVED: To prevent deterioration in a gas concentration sensor by inhibiting the application of an excessive voltage to the gas concentration sensor. SOLUTION: An A/F signal proportional to the concentration of oxygen from a gas concentration sensor such as A/F sensor (limited current type air/fuel ratio sensor) 30 for detecting the concentration of a gas in an exhaust gas from an internal combustion engine 10 with the application of a voltage by a microcomputer 20. When the deviation of the voltage applied to the A/F sensor 30 is found from a specified voltage range by an excessive voltage detection circuit 60, the potential is made the same at both terminals of the A/F sensor 30 by a changeover switch or the like. This arrangement keeps any excessive current from flowing through a sensor element thereby preventing deterioration in the A/F sensor 30. |
