About Reed SensorsComments Off on About Reed Sensors
Reed sensors use a magnet or electromagnet to create a magnetic field that opens or closes a reed switch within the sensor. This deceptively simple device reliably controls circuits in a wide range of industrial and commercial goods.
In this article, we’ll discuss how reed sensors operate, the different types available, the differences between Hall Effect Sensors and reed sensors, and the key benefits of reed sensors. We’ll also provide an overview of industries that use reed sensors and how MagneLink can help you create custom reed switches for your next manufacturing project.
How Do Reed Sensors Work?
A reed switch is a pair of electrical contacts that create a closed circuit when they touch and an open circuit when separated. Reed switches form the basis for a reed sensor. Reed sensors have a switch and a magnet that power the opening and closing of the contacts. This system is contained within a hermetically sealed container.
There are three types of reed sensors: normally open reed sensors, normally closed reed sensors, and latching reed sensors. All three types may use either a traditional magnet or an electromagnet, and each relies upon slightly different methods of actuation.
Normally Open Reed Sensors
As the name implies, these reed sensors are in the open (disconnected) position by default. When the magnet in the sensor reaches the reed switch, it turns each of the connections into oppositely charged poles. That new attraction between the two connections forces them together to close the circuit. Devices with normally open reed sensors spend most of their time powered off unless the magnet is purposefully active.
Normally Closed Reed Sensors
Conversely, normally closed reed sensors create closed circuits as their default position. It isn’t until the magnet triggers a specific attraction that the reed switch disconnects and breaks the circuit connection. Electricity flows through a normally closed reed sensor until the magnet forces the two reed switch connectors to share the same magnetic polarity, which forces the two components apart.
Latching Reed Sensors
This reed sensor type includes the functionality of both normally closed and normally open reed sensors. Rather than defaulting to a powered or unpowered state, latching reed sensors stay in their last position until a change is forced upon it. If the electromagnet forces the switch into an open position, the switch will stay open until the electromagnet powers up and makes the circuit close, and vice versa. The operate and release points of the switch create natural hysteresis, which latches the reed in place.
Reed Sensors vs. Hall Effect Sensors
Hall Effect sensors also use the presence of magnetic force to power the opening and closing of a switch, but that’s where their similarities end. These sensors are semiconductor transducers that produce a voltage to activate solid-state switches rather than switches with moving parts. Some other key differences between the two switch types include:
- Durability. Hall Effect sensors may need additional packaging to protect them from the environment, whereas reed sensors are protected within hermetically sealed containers. However, since reed sensors use mechanical movement, they are more susceptible to wear and tear.
- Electricity demand. Hall Effect switches require a constant flow of current. Reed sensors, on the other hand, only require power to generate a magnetic field intermittently.
- Vulnerability to interference. Reed switches can be prone to mechanical shock in certain environments, while Hall Effect switches are not. Hall Effect switches, on the other hand, are more susceptible to electromagnetic interference (EMI).
- Frequency range. Hall effect sensors are useable over a wider frequency range, while reed sensors are usually limited to applications with frequencies below 10 kHz.
- Cost. Both sensor types are fairly cost-effective, but overall reed sensors are cheaper to produce, which makes Hall Effect sensors somewhat more expensive.
- Thermal conditions. Reed sensors perform better in extreme hot or cold temperatures, while Hall Effect sensors tend to experience performance issues at temperature extremes.
Characteristics for Reed Sensors
Reed sensors have many unique characteristics that make them ideal for many different applications. Those characteristics include:
Operators can control the conditions and effectiveness of their reed sensors. For example, manufacturers may either mount reed switches on non-ferrous materials or insert a non-ferrous material barrier between the sensor and the mount. At MagneLink, we specialize in adding anti-shock protections, long-lasting mechanisms, and more.
Reed sensors only need to be powered when the switch is active in its non-default position. Latching sensors have even more efficient power demands because the switch stays in its last position until actively triggered.
Reed sensors resist damage from adverse environmental conditions like moisture, temperature, and extreme weather. This is due to the simplicity of the mechanism, the protective seal, and its sensitivity to the magnetic field regardless of operating conditions.
Safe use in different conditions
Magnetic reed sensors can perform in extreme and hazardous environments. The hermetic seal, resistance to shock, and simplicity of the circuit let it withstand proximity to explosions, vibrations, and other hazards. Reed sensors may also operate safely near explosive gases due to the hermetic seal on the protective container.
A reed sensor’s sensitivity to the magnetic field stays strong regardless of environmental factors. It will grow more responsive to magnetic fields as the temperature increases.
Applications of Reed Sensors
Reed sensors are heavily used in almost every industry. They provide a very simple and controllable mechanism for safely opening and closing circuits. Industrial facilities typically use one of the various reed sensor types for equipment that passively runs without direct intervention or equipment that automatically powers down in the event of a malfunction.
These default controls, governed by normally open and normally closed switches, create workspaces that are safe and efficient. MagneLink is proud to serve the following industries with high-quality reed sensors:
- Appliances. Reed sensors operate well in appliances that create moist or humid environments, such as dishwashers, refrigerators, and washers.
- Automation and manufacturing. Reed sensors have countless practical applications in production. Conveyor belts, cylinder pistons, and automated factory machinery all use reed sensors to detect limits and facilitate on/off functionality.
- Automotive. Automotive goods need to meet strict standards that protect against failure. Both automotive accessories and OEM parts use reed sensors to create circuits that operate in car engines. These devices need circuitry that can withstand high temperatures, proximity to other circuits (aided by non-ferrous metal barriers), vibration, and gases.
- Electronics. Reed sensors facilitate opening and closing of automatic doors. They also serve as proximity contacts for security devices used on doors and windows, or in devices that use a clamshell design.
- Extreme conditions. Reed sensors offer reliable performance in applications with extreme temperatures or other harsh conditions.
- General Original Equipment Manufacturing (OEM). OEM manufacturers use reed sensors for a myriad of purposes, such as speed sensors for gears and safety switches.
- Medical. Electronic medical devices such as pacemakers use reed sensors to provide efficient, reliable circuitry operations with minimal maintenance requirements. Equipment such as defibrillators, sensors, feeding tubes, and hospital beds also implement reed sensors.
- Recreational and fitness products. Reed sensors can be used in a variety of recreational and fitness equipment. For example, reed sensors serve as speed sensors in bicycle wheels and treadmills.
Reed Sensors from MagneLink Inc.
MagneLink, Inc. specializes in creating standard and custom reed switches for a variety of industrial and commercial applications. Each sensor comes in several options to best match the applications and intended environment of the sensors. Some of our options for custom switches include:
- Housings. We provide a variety of housings that further protect each sensor and allow for easy mounting.
- Electrical specifications. Our sensors can be adapted with transformers for use with different switch types and input or output requirements. We also provide different cable and connector types.
- Environmental protections. Talk to our engineering team about different protections, such as our anti-shock mechanisms that make reed sensors even more durable.
- Accessories. Our accessories include transformers, cables, and connector mate options.
MagneLink has been producing high-quality switches and sensors for more than 25 years. We prioritize customer service and expert custom switch design to produce exactly the right parts for your next project. Contact us today to learn more about our capabilities or request a quote to place your order from our extensive inventory of available switches and accessories.