Capacitive Sensors for Contactless Level and Composition Measurement in Automotive Clear Vision Systems

This publication presents an innovative concept for contactless liquid measurement with an integrated capacitive transducer in containers of automotive cleaning systems. In contrast to the currently installed electromechanical systems, the capacitive measurement allows a chemically and mechanically isolated, continuous and inherently wear-free measurement. An integration of the sensor directly into the container's wall offers a considerable savings potential in terms of miniaturization and installation efforts. The contribution focuses on the operating principle of capacitive sensors for implementing a continuous liquid level measurement, a measurement of the specific electric conductivity of the liquid to distinguish between deionized and tap water and a measurement of the alcohol concentration for the prediction of the solutions' freezing point. For this purpose, the impedance of the transducers were carried out in a spectral range from 100 Hz to 10 MHz, to gain the characteristic impedance spectra for deionized and tap water, methanol, ethanol and isopropanol.