Float switches are essential for many businesses in which the levels of fluids need to be changed and carefully controlled. With the focus on practical applications in specific industries, it’s easy to overlook or get confused about exactly how a float switch works. In this post, we’re going to take a step back and explain some fundamentals.

How Float Switches Operate

The basic function of a switch is to open and close a circuit, which allows a signal current to pass through or prevents it from flowing. A float switch, which is also sometimes called a liquid level switch, adheres to that same basic principle.

If a float switch is normally open, it is incomplete, which means an electric current is unable to flow and the circuit is unable to be activated. In that position, a float switch can be used to pump down or empty a tank.

float switch

When a float switch is normally closed, there are no gaps, which means the current is able to flow throughout the circuit. In that case, a pump can be activated and used to fill a tank, or an alarm can be activated.

Before a float moves up or down, it is at rest, or in a normal position in which it is not suspended in the liquid. As the liquid rises or falls, it drives the float up or down. That, in turn, opens or closes the switch.

The distance a float travels is set using stops based on the way the magnetic field affects the reed switch. Under most circumstances, it is not necessary to move the stops. If they are moved, there may be float overrun.

How Float Switches Can Be Used in Commercial Applications

In most cases, float switches are in a normally closed position so that power can be activated while the float is at rest. Some customers prefer to have float switches normally open so the power is off. This can be accomplished by flipping the float 180 degrees.

If a pump needs to be turned on to remove liquid from a tank, the float switch would be in the normally open position. If a pump needs to be activated to add water to a tank, the float switch would be normally closed.

A float switch can easily be changed from normally closed to normally open to suit the customer’s needs. To do that, an employee simply needs to remove the bottom of the slosh shield from the liquid level float switch and flip the float over.

Choose the Right Float Switches for Your Company’s Needs

SMD Fluid Controls manufactures switches that are designed to be used in a variety of commercial applications. Our standard float switches contain reed switches in the stems and permanent magnets in the floats.

Contact us today to learn more about how our float switches could benefit your business.


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