Parkhurst & Wendel, L.L.P.
Gas sensor
 Disclosed is a gas sensor comprising a main pumping cell for pumping-processing oxygen in a first chamber; an auxiliary pumping cell for pumping-processing oxygen in a second chamber; and a measuring pumping cell for pumping-processing oxygen in a measurement gas introduced through a third diffusion rate-determining section; wherein a NOx component contained in the measurement gas is measured on the basis of a pumping current flowing through the measuring pumping cell. The gas sensor further comprises a heater for heating at least the main pumping cell, the auxiliary pumping cell, and the measuring pumping cell to predetermined temperatures; an impedance-detecting circuit for detecting an impedance between an inner pumping electrode and an auxiliary pumping electrode; and a self-diagnosis unit for comparing an impedance value detected by the impedance-detecting circuit with a prescribed value to decide whether or not any trouble occurs, on the basis of a result of comparison. Accordingly, it is possible to provide the gas sensor which has a self-diagnosis function capable of quickly and reliably detecting whether or not the gas sensor has any trouble. 
NGK Insulators, Ltd.
G
G01N
inventional
Yasuhiko Nobuhide
Hamada Kato