reed switch

What Is a Reed Switch?

A reed switch is an electrical switch operated by a magnetic field. It contains two flat ferromagnetic reeds sealed inside a glass capsule, usually within an inert atmosphere that helps protect the contacts from contamination and corrosion.

When a magnet or magnetic field moves close to the switch, the reeds are drawn together and complete the electrical circuit. When the magnetic field is removed, the reeds return to their original position and the circuit changes state.

This simple operating principle allows reed switches to provide reliable and repeatable switching without the need for exposed mechanical contacts. They are available in different formats and contact ratings to suit a wide range of sensing, monitoring and control applications.

How Are Reed Switches Used in Liquid Level Sensors?

Reed switch sensors are widely used within float switches and liquid level sensors. In a typical design, a buoyant float containing a magnet moves up and down a stem as the liquid level changes.

When the float reaches a specified position, its magnet activates a reed switch sealed inside the stem. This produces a signal that can be used to:

  • Start or stop a pump
  • Open or close a valve
  • Activate a high- or low-level alarm
  • Provide a switching point to a control system
  • Protect equipment against overflow or dry running

Multiple reed switches can also be positioned at different points within a sensor to provide several fixed level indications.

Deeter Electronics manufactures sensors and switches for use with water, wastewater, oils, fuels and other compatible fluids. Product selection should take account of the liquid, temperature, pressure, mounting position and required switching points.

How Does a Magnetic Reed Switch Work?

A magnetic reed switch responds to the presence or movement of a magnet. The switch itself does not need to make physical contact with the moving component, making it suitable for applications where the switching element must remain sealed or protected.

  • A magnet approaches the reed switch.
  • The magnetic field causes the internal reeds to attract.
  • The contacts open or close, depending on the switch configuration.
  • The connected controller, indicator, alarm or other equipment receives the resulting electrical signal.
  • When the magnet moves away, the reeds return to their normal position.

Because the contacts are sealed inside the glass capsule, the switching action is protected from moisture, dust and many other environmental contaminants.

Deeter Electronics manufacture and supply a variety of liquid level sensors using reed switches, the design in choice for many applications, as they are effective in wet and dirty conditions with wide operating temperature ranges.

For liquid level measurements, an example of which would be for fuel tank level sensing, the Reed switch uses a magnetic float that adjusts with the liquid surface, actuating a hermetically sealed switch in the stem. This simple and comparatively low-maintenance design installs readily, minimizes shock, vibration, and pressure, and works with a variety of fluids.

What Is a Reed Switch Sensor?

A reed switch sensor combines the reed switch with a magnet, protective housing and, where required, additional electronic components. This creates a complete sensing device capable of detecting position, movement or changes in liquid level.

Unlike the individual reed switch component, a reed sensor switch is designed to form part of a finished monitoring or control system. The magnet may be attached to a moving component, positioned within a float or installed separately from the sealed sensor.

The lack of direct mechanical contact between the magnet and switch helps reduce wear. It also allows the sensitive switching element to remain protected within the sensor housing.

Advantages of Reed Switch Sensors

Reed switch sensors are often chosen for industrial applications because they offer:

  • Reliable and repeatable switching
  • Sealed electrical contacts
  • Low mechanical wear
  • Straightforward integration with control equipment
  • Operation across wide temperature ranges, depending on the sensor design
  • Suitability for wet, dirty or demanding environments
  • A choice of formats, materials and contact ratings

The correct reed switch sensor will depend on the application and operating environment. Deeter Electronics can also provide custom liquid level sensors and float switches where a standard product does not meet the required dimensions, materials or switching arrangement.

What is a reed switch?
A reed switch is a type of electrical switch that is activated by a magnetic field. It consists of two thin metal contacts (called reeds) sealed inside a small glass tube. When a magnet comes close, the reeds attract each other and close the electrical circuit. When the magnetic field is removed, the reeds separate again and the circuit opens.
What is a reed sensor?
A reed sensor is typically a complete sensing device built around a reed switch. While a reed switch is the small internal component, a reed sensor usually includes the switch inside a protective housing, sometimes with wiring, mounting hardware, or additional electronics to make it easier to install in equipment or systems.
What is a reed switch sensor?

The term “reed switch sensor” generally refers to the same thing as a reed sensor. It simply describes a sensor that uses a reed switch as its sensing element to detect position, movement, or the presence of a magnetic field.

In most cases, the phrases reed sensor, reed switch sensor, and magnetic reed sensor are used interchangeably to describe a sensor device based on a reed switch.