Patent ID: 8635900

Claim:
A method for evaluating a state of a soot sensor having at least two measuring electrodes that are electrically connected to an evaluation circuit which is permanently installed in a motor vehicle having an internal combustion engine, comprising: detecting a loading of an exhaust gas stream of the internal combustion engine with soot particles by the soot sensor; detecting and evaluating by the evaluation circuit a conductivity between the at least two measuring electrodes of the soot sensor; applying heating current pulses to a soot sensor heater to indirectly heat the measuring electrodes of the soot sensor to a plurality of increasing stepped temperatures, each stepped temperature below a soot burn off temperature; measuring the conductivity between the at least two measuring electrodes at times between the heating current pulses, wherein the stepped temperature of the soot sensor is substantially constant during the measuring of the electrical conductivity; and increasing the temperature of the soot sensor to the soot burn off temperature.