| 摘要 |
PURPOSE:To protect reliably the detector from an excessively heavy current by providing an impedance control circuit for controlling the terminal voltage to a fixed voltage by comparing the terminal voltage of the detector with the set voltage. CONSTITUTION:A current passes a detector 11 through a resistance 13 and a transistor 12, and the oxygen concn. is detected by the voltage drop V2 due to the resistance 13. The voltage basing on the earth potential impressed to the dector 11 through a resistance 21 to a comparator 16 wherein the voltage is compared with the set voltage V1. The output voltage signal of the comparator 16 controls the discharge of a condenser 19, and the smoothed terminal potential of the capacitor 19 controls the base of the transistor 12. The transistor 12 controls the impedance so that the voltage impressed to the detector 11 may be regulated to V1. In this way, the detector 11 is protected from an excessively heavy current. |
