Patent ID: 6468478
Filing Date: 2002-10-22
Classification: G01N,Y10T

Abstract:
An impedance detecting apparatus for an oxygen concentration sensor element, said apparatus comprising:an oxygen concentration sensor in which electric current according to oxygen concentration in a gas to be detected flows to an element having a voltage applied thereto; a control device for switching the voltage applied to said element at a switching time from a reference voltage used for detecting oxygen concentration to a sweeping voltage used for detecting element impedance, to compute said element impedance from a voltage change &Dgr;Vo at the switching time and a voltage change &Dgr;Vi according to a current change caused by said voltage change &Dgr;Vo, wherein said control device switches said element application voltage from said reference voltage to said sweeping voltage at least twice for every detection of said element impedance; an A/D converter for A/D converting said voltage applied to said element and a voltage according to said electric current, wherein said control device computes said element impedance based on an A/D conversion result of said A/D converter; and wherein said control device performs one A/D conversion on said oxygen concentration sensor during a sweeping period when said sweeping voltage is applied.