REED switch Magnetic sensors

With more than 40 years of expertise in the magnetic sensors technology, celduc relais is the leading expert in the manufacturing of 100% Made in France magnetic sensors. Celduc relais offers several ranges of sensors using different technologies. Today we will talk about REED switch sensors. But first, for which purpose are magnetic sensors used?

What are the functions of a magnetic sensor ?

The functions of magnetic sensors are various:

  • to detect a position,
  • to secure a machine,
  • to control the level of a liquid…

Magnetic sensors are used to monitor or control a level, a passage, a movement, a position, a speed … .

Their functions and uses have no limits except the imagination of the user.

Control detection

 In what applications are they used?

The applications of our sensors are also numerous. They can be used in many domestic appliances but also in industry : automotive, aircraft, telecom and also for automation …

Our sensors are also used in buildings.

Our Market

What are the working principles of REED sensors?

A magnetic sensor is made of a REED switch that reacts to a magnetic field.  A magnet is used to control the sensor.

How does a REED  switch operate ?

The REED  switch consists of two or three ferromagnetic flexible metal contacts in a hermetically sealed glass envelope, filled with an inert gas, which will come into contact under the influence of a magnetic field.

Ampoule REED GB

There are three types of REED switch

  •  The  Form A (or NO): Normaly Open when there is a sensing object


  •  The Form B (or NC) : Normaly Closed when there is a sensing object.




  • The Form C (or NO+NC) : change-over contact that switches from one state to another under the influence of a magnetic field.


Reed detector approach mode

A REED detector is a magnetically activated omnipolar switch. This means that a magnet can approach it from any angle, with any pole.  Many configurations are possible, the most common being parallel and perpendicular approach.

-the dotted area represents the opening area
-the area with continuous draw is the closing area

The advantages of a REED sensor

AC ou DC

AC and DC switching

no electricity

No power supply required

environnement difficile

Can operate in harsh environments

detecting area Extensive sensing range (depending on the magnetic sensitivity of the switch, the power of
the magnet as well as the magnetic environment),

solution economique

Cost-effective solution

duré de vie Long service life

celduc references

Here is a selection of REED Switch  sensors.

 Level Sensors

Operation: A float equipped with one or more magnets moves with the fluid and activates a hermetically sealed REED contact thanks to its magnetic field.

Ptfa sensorsPFA2125EX


Position and presence sensors

celduc relais offers a wide range of position/presence sensors which are general purpose sensors for industrial and domestic applications (rebate sensors, door opening, presence of protective covers, white goods, …). They are characterized by their fixing methods which are either screw or tubular.

PAA sensors



Special customers products

At celduc relais 50% of our sensors are made according to our customers’ specifications. So if you have a new project, contact us, we will bring you an adapted solution