Abb Research Ltd.

Anghony Byatt

Daniel A Matter

Thomas Kleiner

Thomas Christen

Walter Ruegg

The subject matter of the present invention is a method and a device for capacitive liquid level measurement which are particularly suitable for determining liquid level between adhesive media 10, 11 of different conductivity. The known sensor principle is based on the fact that the environmentally dependent capacitance is measured between neighboring electrodes 13, 4; 4, 5; 5, 6 of a rod-shaped probe 1. According to the invention, the probe 1 has electrodes 4, 5, 6, 13 with covers 7 of different thicknesses d.sub.i. The effective thickness d.sub.s /.epsilon..sub.s of an insulating pollutant film 14 can then be determined by capacitance measurements between at least two pairs of electrodes 4, 5, 6, 13. The influence of a conductive pollutant film 14 on the capacitance signal can be eliminated by selection of at least one suitable measuring frequency. Furthermore, by optimizing the electrode height h, a large capacitance jump is achieved for a digital liquid level display, and/or a largely continuous increase in capacitance is achieved for an analog liquid level display. The sensor is preferably used to determine the location of an interface 12 between water 10 and oil 11 in a separator tank.

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Klingnau, Switzerland

Anghony Byatt