Magnetrol float level switch controls use a float paired with magnetic coupling to operate a switch based on the rise and fall of a liquid. As the float moves with the level of the liquid, it triggers the switch through a magnetic apparatus.
A float level switch uses the buoyancy principle established by Archimedes, which states that "the buoyancy force action on an object is equal to the mass of liquid displaced by the object." The apparatus uses a float that is partially submerged and rises and falls the same distance as the liquid level.
As the float rises or falls, it causes a magnetic sleeve to move into or out of the field of a magnet that triggers a switch, effectively toggling the switch when the change in liquid level reaches a certain threshold. The apparatus is protected by a non-magnetic barrier tube that keeps the switch mechanisms from contaminating the controlled liquid.
A variety of models are available, including top mounting, side mounting, external cage, single, dual and three switch models. There are also models available that use a float that rides on the interface between two liquids, which allows for interface control. Switches can operate in temperatures up to 1,000 degrees F and in pressures up to 5,000 psig with specific gravities as low as 0.32.