| 摘要 |
PROBLEM TO BE SOLVED: To prevent erroneous judgement of contamination due to temporarily disturbance by changing a reference value to a cleaner side later after this change when a level of an output signal of a gas sensor changes to the cleaner side than the reference value, and interrupting control of change of the reference value when the level changes to more contamination side than the reference value during this time. SOLUTION: In the gas sensor 1, an output signal level Lo changes from the clean side to the contamination side in accordance with ascending of gas concentration in the air. The output signal level Lo at this reference clean state is stored as the reference value Lo with a reference value storing part 12, and also the output signal level Lo is compared to the reference value Lo, and an occurrence of contamination is discriminated by the contamination discrimination part 11. When the output signal level Lo changes to the cleaner side than the reference value Lo, the reference value Lo changes to a level value at the cleaner side with a reference value change part 13 later after this change, and also when the output signal level Lo changes to more contamination side than the reference value Lo during this change control, this change control is interrupted with a reference value change interruption part 14. |
