Patent ID: 7445698

Claim:
A gas concentration detecting apparatus applied to a gas concentration sensor including a sensor element sensing a concentration of a gas to be detected, the sensor element being equipped with a solid electrolyte member and one or more pairs of electrodes disposed on the solid electrolyte member, the apparatus comprising: a control unit configured to control a voltage applied to at least one of positive and negative terminals connected to the electrodes of the sensor element; a measurement unit configured to measure either an element current flow caused by the applied voltage corresponding to a concentration of a specific component of the gas, every time the voltage is applied under the control of the applied voltage, or an electromotive force generated between the electrodes of the sensor element corresponding to the concentration of the specific component of the gas, every time the voltage is applied under the control of the applied voltage; a change causing unit configured to cause a change in either the applied voltage to the sensor element or the element current through the sensor element; a change amount measuring unit configured to measure an amount of a change in each of a current value and a voltage value caused in response to the change caused in either the applied voltage or the element current; a calculation unit configured to calculate an amount of a resistance component to resist the element current flow through the sensor element on the basis of a ratio between the amounts of the changes in the current value and the voltage value; and a detection unit configured to detect abnormality relating to controlling the sensor by utilizing information relating to the amount of the resistance component calculated by the calculation unit, the information being at least one of the amounts of the changes in the current value and the voltage value, wherein the detection unit comprises a monitor unit configured to monitor the measured amount of the change in either the current value or the voltage value; and a determination unit configured to determine occurrence of the abnormality on the basis of the amount of the change monitored by the monitor unit, when the amount of the change in either the current value or the voltage value is equal to zero or a value substantially regarded as zero.