Abstract: Capacitive device to measure changes in liquids, such as changes in the mixing ratio of composite liquids, utilizing capacity measured by an electrode probe. An isolating body is located between the electrodes in the liquid and causes a deviation of the field lines to lower the field strength on the electrodes to avoid measurement disturbances from dirt and air bubbles or other contaminants. Furthermore, circuitry for measuring the capacity independently of any disturbing effects of variable ion concentration in the liquid. This is carried out by separately evaluating the phase of a high-frequency signal on a resonance circuit connected to the electrodes.