... to sense the level of liquid in a tank.When the float ball moves along the stem with the water level, the magnet ... reed switch will energized or cut off the circuit, this will send the control board a signal that the liquid level is ... switch, to prevent overflow or to prevent dry-fire. Application:water heater, water dispenser, air-condition, air-cooler, BSD-P, humidifier, dehumidifier,fluid control ...