| 摘要 |
PURPOSE:To inform a user of occurrence of a failure of an oxygen sensor element and expiration of the lifetime thereof by providing a function of self- diagnosis of the failure and the lifetime of the oxygen sensor element. CONSTITUTION:A triangular wave voltage generating device 1 is connected to the positive electrode of a limiting-current type oxygen sensor element 4 for which an oxygen-ion-conductive solid electrolyte is used, while a device 2 for detecting an output current and conducting a comparative operation of detected data and a device for informing a failure and the lifetime of the oxygen sensor element are connected to the negative electrode of the element. By repeating slowly an increase and decrease of a voltage impressed on the solid electrolyte of the oxygen sensor element 4, between the maximum and minimum values, the failure and the lifetime can be diagnosed regularly without causing hindrance in detection of the concentration of oxygen. The diagnosis of the failure and the lifetime of the oxygen sensor element 4 can be executed simultaneously with the detection of the concentration of oxygen regularly without deteriorating virtually the precision in the detection of the oxygen sensor element 4. |
