| 摘要 |
PURPOSE:To detect the air/fuel ratio at a high accuracy by a method wherein potential is made ready to be applied between a pair of electrodes of an oxygen sensor in a specified range and a large current with the applied potential close to 0V runs to measure the current potential difference. CONSTITUTION:A first electrode 13, an oxygen ion conductive solid electrolyte 14, a second electrode 15 and a gas diffusion layer 16 are provided on a porous substrate 11 of a gas diffusion layer to form an oxygen sensor 10. A heat generating body 12 is buried into a substrate 11. The oxygen sensor 10 acts as oxygen pump depending on the difference in the oxygen partial pressure bettween a measuring gas and a reference gas. At this point, the potential difference between the electrodes 13 and 15 is measured with an upper peak hold circuit 21 or a lower peak hold circuit 27 and current is sent to the electrodes 13 and 15 from constant current circuits 33 and 38 to ensure a constant current. The current potential between the electrodes 13 and 15 is measured. Thus, as a constant current is fed between the electrodes to measure the potential, the air/ fuel ratio can be measured continuously from the air excessive side to fuel excessive side. |
