Abstract: A device for determining whether a lubricant to be examined effects the formation of a deposit on a sensor element has a sensor element for detecting values of at least one physical parameter of the lubricant. The sensor element is in contact with the lubricant. Furthermore, there is provided a potential difference source for applying a potential difference between the sensor element and the lubricant. Moreover, there is provided an evaluator for evaluating at least two values of the physical parameter which are detected at different potential states between the sensor element and the lubricant in order to thus determine whether the lubricant causes a deposit formation on the sensor element.

Abstract: A liquid sensor has comb-shaped electrodes, applied to a piezoelectric substrate, as interdigital transducers for generating an electroacoustic wave from a transmitting transducer to a receiving transducer. The number of finger pairs of the interdigital transducers and the material out of which the electrodes are made are so chosen that a surface shear wave generated by the transmitting transducer and a bulk shear wave generated by the transmitting transducer have different frequencies.