Advantage of cost/quality and cost/performance P4x is a hydrostatic level sensor, that works by measuring the water pressure which is proportional to the water level in a tank. The output is a standard two-wire, 4-20 mA current loop, which corresponds to the full scale of 0-100 mBar for P40, 0-200 mBar for P42, 0-300 mBar for P43, 0-400 mBar for P44 and 0-500 mBar for P45. The sensor is mounted to the DIN-rail in the panel.