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Waterline Controls

Water Level Controls & Sensors

Float Switch – Magnetic Reed Switch, Level Switch for Water Tanks

Waterline Controls builds precision magnetic reed switches for various applications. Our reed level switches provide reliability and flexibility for detecting the water & liquid levels.

Theory of operation

Typically, in this sensor the detection is achieved by a magnetic float moving up and down on the outside of a hollow tube. Inside of the tube are reed switches that open or close as the magnetic float moves into position over the reed switch. There are stops placed on the tube to restrict the movement of the magnetic float to the proper range around the reed switch. The magnetic level sensor can have multiple levels of sensing built into one tube.

Design Challenges

The design of the magnetic level sensor requires that the reed switches be accurately placed inside of the tube and the magnetic floats also be placed properly. These placements need to be secured so that shipping, operational and handling stresses do not change to component locations.


The magnetic float sensor only requires one mounting location and can provide multiple level detection locations. The magnetic floats and tube can be easily made from inert materials. The magnetic float assembly is generally a sealed unit and can be used in hazardous environments. Also being sealed the switch contacts (which are also sealed reed switches) have a very long life when used within their rating.


The reed switches generally are rated for low energy switching, although there are some reed switches that can switch high voltages. But generally currents below 1 Ampere are common. When used in a multiple level switching applications the tube can become lengthy. For the multiple level applications, some method of managing the various outputs will need to be addressed.


Waterline Controls has a sensor submittal sheet for these types of sensors.  The submittal sheet requires the user to set the points on the sensor prior to shipping.