Controller for gas concentration sensor

摘要

An oxygen sensor (10) is employed for determining whether the exhaust air-fuel ratio is rich or lean. A voltage is applied to the oxygen sensor (10) at device impedance calculation intervals to calculate device impedance (Rs). After device impedance calculation, a reverse voltage is applied to the oxygen sensor (10) with a view toward promptly negating the influence of voltage application on the sensor output. Subsequently, the sensor output of the oxygen sensor (10) is sampled at sampling time intervals until it is concluded that the device impedance calculation period is over.