Patent ID: 6901785

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 as a function of 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, the sensor cell having a given pump cell applied voltage-to-sensor cell current characteristic in which the sensor cell current changes as a function of a pump cell-applied voltage applied to the pump cell; and a controller working to determine a value of the pump cell-applied voltage when a value of the sensor cell current changes at a given rate in the pump cell applied voltage-to-sensor cell current characteristic, said controller also determining a control point to which the voltage applied to the pump cell is to be controlled using the value of the pump cell-applied voltage.