Types Of Float Switches

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There are two types of float switches: stem-mounted float switches and cable-suspended switches. These float switches can be horizontal or vertical. 

There are many ways of monitoring the amount of liquid in a tank. Pressure sensors give you high accuracy; ultrasonic sensors are contact-free but the simplicity and low cost of a float switch cannot be beaten. 

Float switches monitor the level of liquid in a tank by using a float, magnet, and reed switch system that automatically opens and closes when water levels lower and rise within the tank.

Atlas Scientific offers plastic float switches for highly corrosive applications and stainless-steel float switches for food or drinking water applications. If you are looking for a simple solution that can easily integrate into your control system, look no further.

What Is A Float Switch?

A float switch is a type of sensor that measures a circuit inside a tank as the level of liquid rises or falls. There are different types of float switches, however, they all serve the same purpose – to activate pump control panels and alarm systems if needed.

Float switches are one of the most effective and reliable instruments to monitor liquid levels in a wide range of industries, including industrial processes that need to monitor liquid levels stored in large chambers and tanks. 

Choosing The Right Float Switch

Selecting which float switch is best suited for your application, will depend on what type of tank is being used. There are two types of float switches: stem-mounted float switches and cable-suspended switches. These float switches can be horizontal or vertical. 

Stem-mounted Float Switches

Stem-mounted float switches move a float up and down a stem, operating on a one-float-one-level basis. They can be simple or complex, depending on how many floats are attached to the single stem. These types of float switches are used in both vertical and horizontal switches.

Cable-suspended Float Switches

Cable-suspended float switches must be tethered, so the float switch cannot move with the flow inside the tank. These types of float switches are much more electronically diverse than stem-mounted float switches.

Cable-suspended float switches can either be simple or complex, depending on the switch points. For example, simple cable float switches will use a single point that controls the switch, whereas complex switches can have up to four switch points.

Horizontal Float Switches

Horizontal float switches are perfect when the access to the top and bottom of a tank is limited. They are used when applications are mounted through the side of a tank with a hinged float attached to a fixed housing unit, where the horizontal float switch rises and falls with the level of the liquid. The float’s movement is what causes the switch to open or close the circuit.

Horizontal float switches can be easily mounted internally or externally, depending on the placement requirements, and can be used for high-level or low-level alarms.

They are also extremely flexible and are a good economic choice that is based on a simple design and tried and trusted technology. Their reliability offers long-term use, without having to calibrate the switch.

Vertical Float Switches

A vertical switch has two parts: a stem and a magnetic float. Vertical switches can either have a plastic or a stainless steel ball, which is then mounted at the top or bottom of the tank. 

One of the two floats is attached to the top of the tank, and the other moves with the liquid level inside the tank. 

Once the float switch is attached and the stem is stationary, one or more hermetically sealed reed switches go inside the tank, and the wires go on the outside of the tank. 

The movement of the float causes the magnetic force to open or close the circuit.

As vertical switches can either be mounted at the top or bottom of the tank, they are perfect in applications where there is no side access to the tank. 

Vertical float switches are also a tried and trusted technology that works on a simple design, offering long-term use, without having to calibrate the switch.

Float Switch Wiring

When using a float switch, it is important to understand the float switch wiring, based on the switch’s open or closed position. 

The word “normal” when working with float switches refers to the lowest position the float is when it is not floating. It is essential to know whether you require a normally open float switch or a normally closed float switch, as many float switches will automatically come with one or the other when you purchase it. Some float switches are reversible, so always check your requirements before selecting the type of float switch.

Below are the generic workings of the switches, however, operations can differ between float switch brands and the type of float switch you will be using. Therefore, always check with the manufacturer’s manual before use. 

  • Normally Open Float Switches

The electrical circuit in an open float switch will be opened in the down position and closed in an up position. When gravity pulls down the float when it is open, and when the liquid rises to the pre-set level in the tank, the float switch closes. 

Open float switches are often used when liquid levels in a tank get too low.

  • Normally Closed Float Switches

Normally closed float switches work the opposite; the electrical circuit in a closed float switch will be closed in the down position and open in the up position. Therefore, when gravity pulls the float down it is closed, and when the liquid rises inside the tank to the pre-set level, the float switch will open. 

A closed switch is used when you want the float switch to trigger a low-level alarm.

What Causes A Float Switch To Fail?

Failure of a float switch is usually from:

  • Incorrect configuration.
  • Poor maintenance. 
  • Using a float switch that is not designed for that specific purpose or application.

Float Switch Applications

As float switches come in a variety of types, they can be used in a wide variety of applications. Some examples are:

  • Sump and sewage pits.
  • Potable water, rainwater, wastewater, and sewage systems. 
  • Refrigerators and air conditioning units.
  • Beverage industries.
  • Industrial washers. 

Summary

There are two types of float switches: stem-mounted float switches and cable-suspended switches. These float switches can be horizontal or vertical. 

Float switches monitor the level of liquid in a tank by using a float, magnet, and reed switch system that automatically closes and opens when water levels lower and rise within the tank.

Regardless of which type of float switch you choose, you can always rely on Atlas Scientific. If you have any questions regarding float switches or are unsure which float switch is for you, please do not hesitate to contact our world-class team. 

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