GAS SENSOR AND GAS CONCENTRATION CONTROLLER

摘要

PROBLEM TO BE SOLVED: To obtain a gas sensor by which an oxygen concentration is detected with good accuracy by a method wherein the oscillation phenomenon of the feedback control system of a control voltage to an oxygen pump is eliminated effectively and the error of a voltage drop portion due to the impedance of the oxygen pump is observed. SOLUTION: A comparison amplifier 32 is installed in such a way that a voltage across both ends of a reference electrode 26 and an inside pump electrode 24a is compared with a reference voltage Vb and that their difference is amplified at a prescribed gain so as to be output. The comparison amplifier is wired and corrected in such a way that an output voltage from the comparison amplifier 32 is used as a pump voltage Vp to an oxygen pump 22 so as to be applied across the inside pump electrode 24a and an outside pump electrode 24b. A resistance Ri for pump current detection is inserted and connected across the output end of the comparison amplifier 32 and the outside pump electrode 24b at the oxygen pump 22. Both ends of the resistance Ri are short-circuited by a capacitor C. In addition, one electrode of the capacitor C is connected to the noninverting terminal of a differential amplifier 44, and the other electrode is connected to the inverting terminal of the differential amplifier 44.