PURPOSE: To attain to prolong the life of an oxygen sensor by conserving the discharge quantity of electricity of a negative pole active substance, by connecting a resistor at the time of non-use over a long period of time and shortcircuiting the same at the time of continuous use or intermittent use including a short-term non-use period.

CONSTITUTION: The main body of a galvani battery type oxygen sensor, a positive pole, a negative pole and a temp. compensating thermistor are respectively shown by numerals 1, 2, 3 and 4. In the case of an operation method A, a switch 7 used at the time of non-use is turned ON for 30 days from the beginning and a switch 6 used at the time of normal use is turned ON for the next 30 days and these operations are repeated. In an operation method B, the switch 7 at the time of non-use is always turned OFF and the switch 6 used at the time of normal use is always turned ON. In the case of the conventional type B, an output current is lowered to a large extent up to about 200 days while, in the case of the operation method A, output voltage is stable even if about 700 days are elapsed. By this mechanism, the life of the sensor, of which the non-use period extends over a relatively long period of time, can be made longer and the operation method of the sensor 9, of which the rising time at the time of use is short, can be provided.