Determining the temperature of an exhaust gas sensor by means of calibrated internal resistance measurement

摘要

For achieving a highest possible measuring accuracy of a circuit for measuring the internal resistance of an exhaust-gas sensor, a method and a circuit for measuring the internal resistance R1 (10) of an electrochemical cell (12) are provided for determining the temperature of an exhaust-gas sensor, especially of a motor vehicle. The circuit is provided with the objective to improve the control to a constant temperature to therefore also improve the performance of the exhaust-gas sensor. A measurement current I_Mess (20) is applied to the internal resistance R1 (10) of the electrochemical cell (12) and a resulting first voltage is detected. A switchover to a reference resistor R2 takes place from time to time or at regular time intervals. With a switchover to the reference resistor R2, the resulting second voltage is stored and thereafter is applied as a reference value for the measurement of the internal resistance R1 (10). The switchover (18) to the reference resistor R2 takes place, for example, via force/sense lines.