| 摘要 |
PURPOSE:To prevent the generation of a detection error due to the change with the elapse of time, by adding calibration means for automatically correcting the variation in the characteristics of a galvanic cell type oxygen sensor due to the change with the elapse of time and the backup means thereof. CONSTITUTION:A calibration means consisting of an amplifier 2, an A/D converter 4 and CPU 5 and a backup means consisting of a backup cell 8 for the backup of said calibration means at the time of the cutting-off of a main power source, a relay 10 and a delay relay 12 are added to a galvanic cell type oxygen sensor 1. The sensor 1 detects the concn. of oxygen in air to generate output voltage which is, in turn, amplified by an amplifier 2 and converted by an A/D converter 4 to be written in the memory of CPU 5. The ratio of the value written in CPU 5 and an initially set value is operated to be compared with a reference set value. Therefore, if the ratio of the output voltage to the concn. of oxygen in the atmosphere and a danger value in an initial product is preliminarily written in CPU 5 as a reference set value, the ratio of terminal voltage to the concn. of oxygen is equal to the reference set value even in a deteriorated product and, therefore, the concn. oxygen in air can be always accurately detected. |
