| 摘要 |
PROBLEM TO BE SOLVED: To give a warning in case of deterioration and at the same time perform self recovery and prevent erroneous measurement by performing the self diagnosis of the presence or absence of deterioration when using a sensor for measuring the oxygen concentration in atmosphere. SOLUTION: A critical current type oxygen sensor 1 has electrodes 2a and 2b. In a DC power supply 3, a closer circuit is formed by the electrodes 2a and 2b and a current detection means 4. A sensor output detection means 5 detects current flowing through the current detection means 4 as sensor output and compares a sensor output A with a threshold E3 and a lower-limit threshold E4 which are stored previously. When the sensor output A is equal to or less than the threshold E3 and the lower-limit threshold E4 continues at least for a specific amount of time, an alarm generation means 9 generates an alarm and a voltage changing means 12 increase the application voltage to the electrodes 2a and 2b. |
