Reed Sensor : for what applications ?

Magnetic proximity sensors are a proven and popular choice for many types of applications. They are often used to monitor the open or closed status of windows, doors, gates, … and more in security applications. Basically, magnetic proximity sensors are a first class solution for any application where there is a need to monitor the position of a moving surface (e.g. a door, window, gate, etc…).

The simplicity of design and function is translating into new applications and use cases for these types of sensors. In contrast to other technologies and sensing solutions, here are their key advantages :

• Magnetic sensors exhibit a far higher sensitivity and have an extensive sensing range (depending on the magnetic sensitivity of the switch, the power of the magnet as well as the magnetic environment),
• They aren’t affected by dust, dirt, oil, grease, water, or other contaminants that can damage capacitive and optical sensors, so magnetic sensors can operate in harsh environments,
• The magnetic field operates freely through plastic and non-ferrous metals, allowing for sensing even across hermetic barriers.
• They do not require an active supply voltage to operate, simplifying design complexity, reducing overall cost, and minimizing power consumption in battery-powered applications.

To sump-up magnetic proximity sensors beat out the competition.

There are so many existing and potential applications for Reed Sensors that it would be impossible to discuss them all in this article. Here are some of the basic applications that we hope will give insight and new considerations for your present and future projects :

Industrial Applications

Magnetic sensors are used in many industrial applications for non-contact detections. celduc’s magnetic proximity sensors are designed to provide superior performance in all of these applications.

Industrial Automation applications

In Industrial Automation applications, every hydraulic or pneumatic cylinder or actuator requires a Reed Sensor and Magnet combination for end position sensing. Unlike inductive sensors or Hall-effect sensors, Reed Sensors use no power and have a good isolation.

Hoists and Fork Lifts

Hoists and Fork Lifts are used to transport materials over short distances, mostly for loading and unloading into trucks. For higher weight, hydraulic systems are required. Magnetic Proximity Sensors are mounted on the outside of these hydraulic pistons and cylinders to sense end positions and intermediary positions. These signals are then used by the proportional pressure valves for controlling the oil pressure to the cylinders and pistons to ensure efficient power usage. As such vehicles work in an industrial environment, the reed switches that are used in Magnet Sensors are hermetically sealed and encapsulated in epoxy to ensure dust will not affect their functionality.

Ensuring safe operations

Safety at work is encouraged and more and more industrial machineries are equipped with safety sensors to ensure safe operation. Celduc’s expertise in this field allows us to offer you a wide range of magnetic safety sensors. Our reliable and durable sensors have already been adopted by many major players in the industry to :

1. Ensure the safety of machine operators and machine operating reliability!
2. Securely lock the access to the machine.
3. Automatically shut it down when a hazardous area close to it is breached.

Medical Equipment

Reed Magnetic Sensors are used in many types of medical equipment that require an End Limit Position detection, as for example on Hospital Beds and Mobility Equipment.
Hospital beds, motorized chairs, special lifts…, require end-position detection. The magnet is usually mounted to the movement mechanism and the Reed Sensor is mounted at the end position detection point. When the magnet is closed to the sensor, the reed contacts will close sending a signal to the system in order to provide reliable operation.

Domestic Equipment

Domestic Appliances need to support higher Shock and vibration, and also extremes of humidity and temperature. Reed Magnetic Proximity sensors withstand all of these working conditions. The most widely used white goods applications is Door position sensing.

Domestic appliances, particularly refrigerators and freezers, must have their doors closed at all times to ensure the freshness of food. Reed Sensors are a simple choice to ensure this. The Reed Sensor is usually mounted on the chassis of the equipment. When the door is opened, the contacts open, activating a timer in the electronics and then an alarm will be activated – giving the user that the door has been left open.

In electronic toilet flush system and solar energy systems, magnetic proximity sensors can detect the water level.

Building Construction / Centralized Building Management

The building construction, infrastructure and Security industry require equipment to work reliably in dirty environments (dust, grease, and oil). Unlike optic sensors, Reed Magnetic Proximity Sensors used are maintenance free and do not need any cleaning or other frequent maintenance.

Sensors for Lifts

The electrical motors in elevators however should start and stop at the required floors. So a feedback on the exact position of the elevator cabine should be given. This feedback is very accurately provided by latching reed sensors that stay in an actuated state as an elevator passes floors on the way up and stay in a non-actuated state as the elevator passes floors on its way down. These Latching reed sensors are mounted on every floor and are changed state by the magnet on the elevator, as it moves up or down, past each sensor.

Sensors for Window Frames

Reed Switches Magnetic sensors are used for monitoring the state of doors and windows (open or closed). Magnets are mounted on the interior frames of doors and windows, and the reed sensors, on the fixed frames. As long as the doors or windows remain closed, the contact is not activated. Normally Open, or Normally Closed reed sensors can be used depending on the circuit logics but in most cases, normally-open devices are preferred.

Smoke Ventilation Systems

Magnetic Proximity sensors are also used in Smoke ventilation systems and are mounted on smoke traps / smoke vents in order to alert when a smoke extraction or vent hatch is opened. This fire-fighting equipment is essential to prevent the fire from spreading too quickly and to allow a good smoke extraction to protect the occupants. The reliability of a smoke extraction hatch or a mechanical smoke extraction device is essential to ensure the safety of the occupants in a building.

Aviation, space

Serving this industry is proof of reliability. celduc ® relais has developed special sensors to detect the opening/closing of the doors as for example push-buttons used to detect open/closed doors in Airbus A380 ; sensors to detect tank refueling in Mirage Rafale and Saab Jas 39 fighters ; level sensors for AIRBUS humidifiers, …

Nuclear energy

celduc® relais has designed and made sensors used for nuclear reactor regulation. These sensors are part of the system’s highest security level. The qualification phase has therefore been very important in this project and our sensors have been tested in extreme situations. This development of sensors for nuclear reactors demonstrates yet again celduc® relais ability to create specific solutions in fields where reliability is essential.

Remote installations

Historically, remote installations like fuel depots, drop boxes, or other similar points of access would be otherwise unmonitored an little secured. It means there was no way to know if anyone had actually been to the locations, taken or left anything, or otherwise gained access without someone physically visiting the site and viewing it directly. The addition of a proximity sensor system with remote communication capabilities can send an alert when a triggering event occurs. This has huge cost savings over the life of the system as it saves time, personnel, and potentially asset loss for the system owners by avoiding unnecessary trips and responding in a more timely way only when actually necessary.

To conclude, Magnetic proximity sensors are ideal for a number of different applications and beat out the competition with several innate advantages. At celduc® relais, we are constantly evolving in line with new applications and market developments. With you, we want to share our 45-years of experience in the reed switch technology.

Tell us about your project and we will provide the solutions.