GAS SENSOR

To measure a deterioration state of a pump cell.SOLUTION: A gas sensor 100 includes a sensor element 101, a main pump cell 21, an impedance measuring section 47, and a control section. The main pump cell 21 has an inner pump electrode 22 disposed in a gas-to-be-measured flow section of the sensor element 101 and an outer pump electrode 23 disposed outside an element body of the sensor element 101 to come into contact with gas to be measured to adjust oxygen concentration in a vicinity of the inner pump electrode 22. The impedance measuring section 47 performs first measurement for measuring a first impedance R1 by applying voltage having a first frequency to the main pump cell 21, and second measurement for measuring a second impedance R2 by applying voltage having a second frequency higher than the first frequency to the main pump cell 21. The control section calculates reaction resistance index Rr correlated with reaction resistance of the main pump cell 21 on the basis of the first and second impedances R1 and R2.SELECTED DRAWING: Figure 1 【課題】ポンプセルの劣化状態を測定する。【解決手段】ガスセンサ１００は、センサ素子１０１と、主ポンプセル２１と、インピーダンス測定部４７と、制御部とを備える。主ポンプセル２１は、センサ素子１０１の被測定ガス流通部に配設された内側ポンプ電極２２と、被測定ガスと接触するようにセンサ素子１０１の素子本体の外側に配設された外側ポンプ電極２３と、を有し、内側ポンプ電極２２の周囲の酸素濃度を調整する。インピーダンス測定部４７は、主ポンプセル２１に第１周波数の電圧を印加して第１インピーダンスＲ１を測定する第１測定と、主ポンプセル２１に第１周波数よりも大きい第２周波数の電圧を印加して第２インピーダンスＲ２を測定する第２測定と、を行う。制御部は、第１，第２インピーダンスＲ１，Ｒ２に基づいて主ポンプセル２１の反応抵抗と相関のある反応抵抗指標Ｒｒを算出する。【選択図】図１