Capacitive level detector with optimized electrode geometry

Abstract

The subject matter of the present invention is the optimization of a capacitive liquid level sensor which is suitable, in particular, for determining the location of a boundary layer,between water,and oil,in a separator tank. The known sensor principle is based on measuring the environmentally dependent capacitance between neighboring electrodes,of a rod-shaped probe,. According to the invention, the probe,is designed such that large ionic double-layer capacitors occur on the electrodes,in the more conductive medium,, and small capacitors occur between electrodes,in the insulating medium,. For this purpose, the electrode height h is selected to be large, the ratio of the electrode height h to the electrode spacing a is preferably selected to be in the range of 1<h/a<6 and, in particular, the measuring frequency f is selected to be in the dielectric cut-off frequencies of the media,. As a result, it is possible to achieve a large jump in capacitance for a digital liquid level display and/or a largely continuous increasing capacitance for an analog liquid level display. Furthermore, the influence of more conductive and/or insulating dirt films,on the capacitance signal is eliminated by suitable measuring frequencies and/or by radially offsetting the electrodes