Patent ID: 6895800

Claim:
A gas concentration measuring apparatus comprising: a gas concentration sensor including a gas chamber into which gasses are admitted, a pump cell responsive to application of a voltage to pump oxygen molecules contained in the gasses out of and into the gas chamber selectively and produce a pump cell current, a sensor cell working to produce a sensor cell current indicating a concentration of a specified gas component contained in the gasses having passed through the pump cell, and a monitor cell working to produce a monitor cell current indicative of a concentration of residual oxygen molecules within the gas chamber; a pump cell-applied voltage determining circuit looking up a predetermined voltage-to-current relation to determine an initial value of the voltage to be applied to said pump cell as a function of the pump cell current produced by said pump cell; and a pump cell-applied voltage correcting circuit working to apply the initial value of the voltage to the pump cell and sweep the initial value to at least one of higher and lower level sides, said pump cell-applied voltage correcting circuit correcting the initial value of the voltage applied to the pump cell as a function of a magnitude of the sensor cell current produced by the sensor cell upon a sweep of the initial value of the voltage applied to the pump cell.