Electronic instrument that controls the level of a liquid din rail mounting . Through the use of three probes, it is possible to control the level of a liquid into a tank, both in empty mode, that in filling up mode (functions named LD or LS).
While the standard impedance of the liquid is 10 kOhm, other values are on demand. Through the probes there is flowing a small alternating current not to polarize them. The instrument is powered by an alternating voltage through a transformer. Fixed hysteresis.