The Ketwells, KWLS-F21 Liquid Level Float Switches low-cost, hermetically sealed level switch is designed for mounting upper on the tanks. Its operating concept is based on two scientific principles, buoyancy and magnetism.

The float is specifically engineered to match the specific gravity and viscosity of the target liquid. Inside the float is a magnet, while the stationary stem houses a reed switch. When the liquid level changes, the float rises or falls accordingly. As the magnet inside the float moves into proximity with the reed switch, it activates or deactivates the electrical contact, depending on its position.