Level gauge for measuring filling level of liquids with low conductivity especially water

摘要

The level gauge works according to the principle of capacitive filling level measurement. It has probe rods (4, 5) and an electronic evaluation unit controlling their probe capacitances. A constant current source charges the probe capacitances (13, 14) of the probe rods (4, 5), for forming a linear voltage rise per unit time. The probe capacitances are discharged using a transistor, pulsed with a constant frequency. A blanking out signal of the same frequency pulses a further transistor. Which together with an evaluation circuit, also a low pass with resistor and capacitor, taking account of a highly stable voltage. Effects the formation of a DC voltage proportional to the filling level of the relevant liquid to be measured, for the control of an indicating instrument.