For simultaneous monitoring of the minimum and maximum liquid levels in conductive liquids. The sensors (not included) can be easily self-made with contact surfaces on the container wall or with rod or cable electrodes.

Operation: Four electrodes are mounted in the liquid container, extending into the medium up to the desired switching point. The liquid level is indicated by four LEDs according to water contact. When the container is completely empty, the red LED lights up. The lower pair of electrodes is used, for example, to control a filling valve. When the lowest electrode is released, the filling valve or pump is activated, and it turns off again when the second electrode is wetted (hysteresis). The upper pair of electrodes serves the same function to regulate the upper level, such as a pump. The second channel does not have to be used. The switching behavior of the evaluation (filling/draining) can be selected via two jumper bridges. The sensitivity of the electrodes is adjustable via potentiometers. Two potential-free relays with changeover contacts are used to control the valves or the pump.

Applications: Water replenishment and monitoring in rainwater cisterns, monitoring of condensate trays and compressor pressure vessels, boilers, springs and wells, livestock watering, pump control.