Patent ID: 6868713

Claim:
Device for determining the internal resistance of a linear oxygen probe of an internal combustion engine, comprising: an oscillator for producing an alternating current which is superimposed on the probe internal resistance through a decoupling capacitor via a probe terminal and which, after being amplified in an amplifier then rectified, generates a voltage proportional to the probe internal resistance as a regulating signal for a probe heater, and a voltage divider to whose two terminals the oscillator output signal is supplied which produces a voltage at its tap which generates the alternating current flowing through the probe internal resistor, wherein the output signal of the oscillator with a phase position that is mutually opposed is supplied to the two terminals of the voltage divider from the time the operating voltage is switched on, through which the oxygen probe is heated, until the voltage at the output of the amplifier that is proportional to the probe internal resistance falls below a pre-determined set value, and at this point in time the output signal of the oscillator is supplied to both terminals of the voltage divider with the same phase position.