Abstract: A method is disclosed for determining a current temperature of a heating element with a PTC thermistor property (PTC) with which a urea-water solution for cleaning the exhaust gas in an internal combustion engine of nitrogen oxides can be heated. According to the invention there is provision that a correction factor is formed from the quotient of a minimum resistance of the heating element and of a minimum resistance of a reference heating element, in that a resistance which is determined at a current temperature of the heating element is multiplied by the correction factor, and in that the current temperature of the heating element is determined from the corrected resistance value and a temperature dependence of the resistance of the reference heating element. The method according to the invention permits more precise determination and regulation of the temperature of the heating element.

Abstract: A method is disclosed for determining a current temperature of a heating element with a PTC thermistor property (PTC) with which a urea-water solution for cleaning the exhaust gas in an internal combustion engine of nitrogen oxides can be heated. According to the invention there is provision that a correction factor is formed from the quotient of a minimum resistance of the heating element and of a minimum resistance of a reference heating element, in that a resistance which is determined at a current temperature of the heating element is multiplied by the correction factor, and in that the current temperature of the heating element is determined from the corrected resistance value and a temperature dependence of the resistance of the reference heating element. The method according to the invention permits more precise determination and regulation of the temperature of the heating element.

Abstract: A method for operating a reagent dosing system (12), in which at least one dosing valve (14) doses a reagent upstream of at least one SCR catalytic converter (16) which is arranged in an exhaust-gas duct of an internal combustion engine (10), in which method the reagent, which is stored in a tank (28), is heated by means of a heater (30), and in which method a cavity (44) in the region of the heater (30) is detected on the basis of the evaluation of a characteristic variable of a measure of the heating current (32). The approach according to the invention is characterized in that, in the event of a cavity (44) being detected, a notification signal (52) is provided.

Abstract: Fill level sensors designed as potentiometers are known, having two resistor strips on an electrically insulating carrier, on each of which a plurality of conductor segments are disposed at a distance from each other and act together with a pickup shoe that can move relative to the carrier, wherein the conductor segments of the one resistor strip are disposed offset from the resistors of the other resistor strip in the direction of motion of the pickup shoe. The pickup shoe electrically connects one conductor segment of the one resistor strip to a conductor segment of the other resistor strip. In order to contact the two conductor segments to be bridged, the pickup shoe has two contacts.