IDEA #5IGJGI Capacitive level detector with optimized electrode geometry

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 12 between water 10 and oil 11 in a separator tank. The known sensor principle is based on measuring the environmentally dependent capacitance between neighboring electrodes 13, 4; 4, 5; 5, 6 of a rod-shaped probe 1. According to the invention, the probe 1 is designed such that large ionic double-layer capacitors occur on the electrodes 4, 5, 6, 13 in the more conductive medium 10, and small capacitors occur between electrodes 4, 5, 6, 13 in the insulating medium 11. 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 10, 11. 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 14 on the capacitance signal is eliminated by suitable measuring frequencies and/or by radially offsetting the electrodes 4, 5, 6, 13. https://app.acclaimip.com/pdf/dvIZWWLfXBF38hk8h99cHRzNQ-opSxWBGDpWIXc/US6318172