Abstract: The present invention relates to a method for calibrating a UWS quality sensor arranged in a motor vehicle. In the method, the calibration of the UWS quality sensor takes place in an installed situation of the UWS quality sensor in the UWS tank.

Abstract: A method and an apparatus for determining the fill level of a fluid (2) in a tank (1), wherein a propagation time of an ultrasonic signal between an ultrasound element (4) and a reflection at the surface (3) of the fluid (2) is measured. A first, single reflection and a second, double reflection are evaluated, wherein the measurement of the reflections is carried out with a measurement setting with an excitation energy of the ultrasonic signal and a sensitivity. The sensitivity is indicated by a gain and a comparison value (13). Via measurements with different measurement settings, a suspected first reflection and a suspected second reflection are located and a plausibility check is carried out of the propagation times of the first and second reflections with respect to each other.

Abstract: The present invention relates to a method for calibrating a UWS quality sensor arranged in a motor vehicle. In the method, the calibration of the UWS quality sensor takes place in an installed situation of the UWS quality sensor in the UWS tank.