Verfahren zur Bestimmung der Dielektrizitätskonstante und/oder der Leitfähigkeit mindestens eines Mediums sowie Vorrichtung zur Durchführung des Verfahrens

摘要

The aim of the present invention is to optimize a capacitative level detector, which is particularly suitable for determining the location of a boundary layer (12) between water (10) and oil (11) in a separator tank. The known sensor principle consists of measuring the environment-dependent capacity between neighbouring electrodes (13, 4; 4, 5; 5, 6) of a rod-shaped probe (1). The invention is characterized in that the probe (1) is designed in such a way that in a more conductive medium (10) large ionic double-layer capacities occur at the electrodes (4, 5, 6, 13) and in a more isolating medium (11) small capacities are present between the electrodes (4, 5, 6, 13). To this end, the invention provides for a large electrode size (h), a relation of electrode size (h) to electrode distance (a) preferably in the range 1 < h / a < 6, and, in particular, a measuring frequency (f) between the dielectric limit frequencies of the media (10, 11). This enables a large capacity shift for a digital level indicator and/or a largely continuous capacity increase for an analogue level indicator to be obtained. In addition, the effect of conductive and/or isolating contaminant films (14) on the capacity signal is eliminated by suitable measuring frequencies and/or radial displacement of the electrodes (4, 5, 6, 13).