Everything You Need to Know About Float Switches

A float switch is a type of level sensor, and it is used to detect the level of liquid in a tank, well, or other kind of container. Based on the level it measures, it may then activate an alarm or turn other equipment on or off to raise or lower the liquid level as necessary. They are used in lots of different industries, for lots of different types of projects. If you are considering installing one, here is a quick overview of what you need to know about these useful devices:

Working of float switches

As the name implies, a float switch works by literally floating on the surface of the liquid it’s measuring the level of. Many use an airtight reed switch inside, with wires leading outside of the tank. A reed switch is an electrical switch that is operated by an applied magnetic field. As the water level changes, the float rises or falls with it. This then turns the switch on or off by moving the magnet. Float switches can be used with all sorts of liquids, from both clean water and industrial wastewater to oil and even acids.

Different types of float switches

A float switch isn’t just one type of device. There are actually a few different varieties, and the one that’s right for you will depend on exactly what liquid you want to use it to measure and in what type of vessel. For example, a vertical level sensor is mounted on either the top or the bottom of a tank, whereas a horizontal level sensor is mounted on the side. There are also highly customizable multi-level sensors available for more complicated requirements.


Another difference is the way in which the switches are wired. The two main methods are ‘normally open’ and ‘normally closed’. The former is usually used in cases where you want to detect when the liquid you’re measuring rises to a certain level, and the latter when you want to detect when it falls to a certain level (although this may vary depending on whether you are fixing the switch to the top or bottom of the tank).

Float switches also come in a variety of materials, from plastic to corrosion-resistant stainless steel. The right one for you will depend upon the liquid you intend to use it with.

Key considerations

The position of installation is very important with float switches. For example they should never be installed on a sloping surface, because this affects the accuracy of the readings from it. Similarly you want to avoid having then near inlets or outlets where there is a flow of water, because the waves created can cause a time delay. As float switches work using magnets, it’s also best to avoid having them near other magnetic fields in case of interference.

Finally, any vibrations can also cause issues and it is recommended to avoid submerging the cables. Plus of course, always handle them with care!

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