Due to its reliability, a float switch is one of the most frequently used measurement technologies for monitoring liquid media levels. Its simple yet effective design consists of a hollow float within a guide tube, rising and falling with liquid levels and activating switches along the way. Find out more about what a float switch is and how it works.
A float switch is versatile, consistent and exceptionally reliable. Its simple mechanics have been used to control water flows in mills and fields for centuries. Despite various level-measurement innovations in the past decades, the modern float switch is still the most frequently used method for monitoring liquid media levels today.
In its simplest form, a float switch consists of a hollow float body with a built-in magnet, a guide tube to guide the float, adjusting collars to limit the movement of the float, and an inert gas switch contact on the inside. See this short videofor a visual representation of level monitoring with a float switch.Â
How Does a Float Switch Work?
The buoyant float with a permanent magnet rises or falls along a guide tube with the rising or falling levels of the medium being measured. The guide tube is fitted with a reed contact, which is energized by the movement of the magnet. When a preset switch point is reached, the reed contact is actuated.
The guide tubeâ€™s reed contacts consist of contact leaves within the hermetically sealed glass body. These move together or apart when a magnetic field is applied from the float. When a reed contact has a normally open function, the leaves are brought into contact when a magnetic field is applied. When the contact between the leaves is made, a current flows through the closed leaves and a switching signal is detected.
For a float switch with a normally closed switching function (SPST, or single-pole single-throw), the contact or circuit is interrupted when a magnetic field is applied. If one selects a change-over contact (SPDT, or single-pole double-throw), the glass body contains three contact leaves where, at all times, normally closed and normally open contact are simultaneously made for every operation.
Since the contact leaves are under a mechanical preload, a magnetic field must be applied for the contact leaves to close or open. This generates the desired switching signal (monostability). The adjusting collars serve as a limitation for the float body in the correct position, to ensure the desired switching signal is accurate in reaching the defined level.Â
WIKA: A Leading Provider of Float Switches
The simple and proven functional principle of a float switch enables a very wide range of applications, from general industrial systems to maritime vessels. One of WIKAâ€™s most versatile float switches is the Model WFS.Its operation is non-contact and free from wear. It works independently of foaming, conductivity, dielectric, pressure, vacuum, temperature, vapors, condensation, bubble formation, boiling effects, and vibrations â€“ making it a cost-efficient, simple solution suitable for almost all liquid media and many industrial applications.