| 摘要 |
PURPOSE:To prevent the change of an output characteristic by adsorbed oxygen by impressing a DC or AC voltage at every specified time to an oxygen partial pressure ratio detecting cell of an oxygen pump type sensor. CONSTITUTION:Oxygen ions migrate from an electrode 2b side to an electrode 2a side and the oxygen in a gap part G is pumped to the outside of an oxygen pump element 2 when a voltage is impressed between the electrodes 2a and 2b of said element 2. A difference in the oxygen concn., therefore, arises between the outside of the oxygen partial pressure ratio detecting cell 3 and the gap part G. Electromotive force is generated in the cell 3 by such concn. difference. This electromotive force is detected by an electromotive force detecting means 61 and the voltage impression to the element 2 is so controlled by a pump current control means 63 that the detection output VS attains equal to a reference voltage VREF. Since the pump current Ip to the element 2 is approximately linearly proportional to the content of the oxygen in an ambient atmosphere, the oxygen concn. is measured by measuring the current Ip. The adsorbed oxygen is removed and the change of the output characteristic occurring in the adsorbed oxygen is prevented in spite of long-term use by impressing the DC or AC voltage to the cell 3 at every specified time. The oxygen concn. is thus exactly measured. |
