| 摘要 |
PURPOSE:To enable highly accurate detection of activation of a sensor quickly and accurately, by directly measuring an internal resistance at a detection element section. CONSTITUTION:An activation detecting circuit 20 is equipped with a constant current circuit 21 for supplying a fixed current to an oxygen pump element 4 of a sensor S from a porous electrode 3 side and a voltage detecting circuit 22 for detecting voltages generated in porous electrodes 2 and 3 at both ends of the element 4. It is also provided with an activation discriminating circuit 23 or the like which detects the activation of the sensor S and outputs an activation detection signal. The circuit 20 supplies a fixed current from the electrode 2 side which is directly contacting an ambient measuring gas of the element 4 with the circuit 21 and detects voltages currently generated between the electrodes 2 and 3 of the element 4 to measure an internal resistance of the element 4. Then, the circuit 23 determines whether the resulting measured value, namely, the voltage between the electrodes 2 and 3 is below a set voltage E0 to find that the element is activating with the internal resistance of the element 4 below a specified value thereby enabling accurate detection. |
