Gas sensor

A gas sensor capable of sensing a predetermined gas component in a measurement gas, the gas sensor comprising:

• a sensor element formed of an oxygen-ion conductive solid electrolyte;
• and
• a controller controlling operation of the gas sensor, wherein
• the sensor element includes:
• a plurality of internal spaces which sequentially communicate with each other from an inlet for the measurement gas under predetermined diffusion resistance, and in which respective inner electrodes are arranged;
• an out-of-space pump electrode disposed at a location other than the plurality of internal spaces;
• a porous body region covering the out-of-space pump electrode;
• and
• a plurality of electrochemical pump cells arranged to correspond to the respective internal spaces, the plurality of electrochemical pump cells pumping in or out oxygen between the plurality of internal spaces and an outside of the sensor element by applying pump voltages across the inner electrodes in the respective internal spaces and the out-of-space pump electrode from predetermined pump power supplies,
• the plurality of internal spaces include:
• a first internal space which is located closest to the inlet, and in which a main pump electrode is disposed as one of the inner electrodes;
• and
• a measurement internal space which is located farthest from the inlet, and in which a measurement electrode is disposed as one of the inner electrodes,
• the plurality of electrochemical pump cells include:
• a main pump cell including the main pump electrode and the out-of-space pump electrode;
• and
• a measurement pump cell including the measurement electrode and the out-of-space pump electrode,
• the controller is configured to:
• control operation of the plurality of electrochemical pump cells other than the measurement pump cell to adjust an oxygen concentration in one or more of the plurality of internal spaces corresponding to the plurality of electrochemical pump cells other than the measurement pump cell,
• control operation of the measurement pump cell to allow a measurement pump current in accordance with a concentration of the predetermined gas component to flow between the measurement electrode and the out-of-space pump electrode, and
• determine the concentration of the predetermined gas component based on a magnitude of the measurement pump current, and
• the controller is further configured to
• control the main pump cell to pump in oxygen to the first internal space so as to allow a reference pump-in current of magnitude A to flow as a limiting current in a case where a pump-in current evaluation gas having a known oxygen concentration is introduced from the inlet to the plurality of internal spaces, and
• control the main pump cell to pump out oxygen from the first internal space so as to allow a reference pump-out current of magnitude B to flow as a limiting current in a case where a pump-out current evaluation gas having a known oxygen concentration is introduced from the inlet to the plurality of internal spaces,
• wherein a ratio A/B is 0.07 or more.