Patent ID: 7608176

Claim:
A gas concentration detecting apparatus comprising: a gas sensor further comprising: a first cell for detecting a concentration of oxygen in a measurement gas, the first cell having a first chamber and a pair of first electrodes, discharging or pumping in oxygen contained in the measurement gas introduced from an external space into the first chamber to generate a pumped measurement gas which contains an excessive oxygen and to output a first electric current indicating the concentration of oxygen in the measurement gas when a first electric voltage is applied between the pair of the first electrodes; and a second cell for detecting a concentration of a specific gas in the pumped measurement gas, the second cell having a second chamber and a pair of second electrodes and decomposing the specific gas contained in the pumped measurement gas which is generated by the first cell and is introduced from the first chamber into the second chamber to output a second electric current indicating a concentration of the specific gas in the measurement gas when a second electric voltage is applied between the pair of the second electrodes; and a controller that determines a completion of activation of the first cell for allowing to start making use of the first electric current at a first time moment at which a first predetermined period of time elapses after the electric power has been started to be supplied to the first and the second cells to activate at least the one of the first cell and the second cell, and determines a completion of activation of the second cell for allowing to start making use of the second electric current when the second electric current flowing in the second cell of the gas sensor is fallen into a predetermined range and when a predetermined time elapses.