| 摘要 |
PURPOSE:To enable the operation failure condition of a gas sensor to be detected by judging the degree of transient changes in the resistance of the gas sensor element and detecting the gas sensibility of the gas sensor element. CONSTITUTION:When a normal gas detecting condition is continued for a month, the output voltage E of an output element R is measured via an A/D converter 4 and an input circuit 5 by a command from a CPU 6 and a measured value is stored 10 as E0. Then, a switch 9 is opened via an output circuit 8 to stop the heating of the heater of a gas sensor element 1, the temperature of the heater is lowered by rendering the gas sensor element a non-electrification condition, after about 1min, the switch 9 is closed to again electrify the heater of the element 1 and the heater is again heated. After about 25sec from the start of re-electrification, the voltage E of the element R is measured again via the converter 4 and the circuit 5 and a measured value is stored 10 as Em. The voltage E0 is read from a memory 10 and a value Em/E0 is obtained. When the value Em/E0 is smaller than 1.3, an alarm 11 is operated via the circuit 8 to display or alarm an abnormality, urging inspection and the replacement of the element 1.
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