Parkhurst & Wendel, L.L.
Gas sensor and gas concentration controller
 Disclosed are a gas sensor and a gas concentration controller each comprising a comparative amplifier for comparing a reference voltage with a terminal voltage between a reference electrode and an inner pumping electrode to obtain a difference therebetween, and amplifying the difference with a predetermined gain to make an output. Wiring connection is arranged so that the output voltage from the comparative amplifier is applied, as a pumping voltage to an oxygen pump, between the electrode and an outer pumping electrode. A resistor for detecting a pumping current is inserted and connected between an output terminal of the comparative amplifier and the electrode of the oxygen pump. A short circuit is formed between both ends of the resistor by using a capacitor. One electrode of the capacitor is connected to a non-inverting terminal of a differential amplifier, and the other electrode is connected to an inverting terminal of the differential amplifier. Accordingly, it is possible to effectively avoid the oscillation phenomenon of the feedback control system for the oxygen pump, and absorb the error in the amount corresponding to voltage drop resulting from the impedance of the oxygen pump. 
NGK Insulators, Ltd.
G
G01N
inventional
Noriyuki Nobuhide
Ina Kato