Introduction to Three Types of Magnetic Reed Sensors

The reed switch sensor is a device that uses a magnet or electromagnet to create a magnetic field that opens or closes the reed switch inside the sensor. This seemingly simple device can reliably control circuits in various industrial and commercial products.

Reed Switch Sensor Working Principle

A magnetic reed switch sensor operates by utilizing a pair of ferromagnetic reeds enclosed in a hermetically sealed glass envelope. In the absence of a magnetic field, the reeds remain separated, keeping the circuit open. When a magnet is brought near, the magnetic field causes the reeds to attract and touch, closing the circuit and allowing current to flow. This interaction can trigger various actions, such as activating alarms or sending signals to control systems. The entire assembly is housed in a sealed container to protect against environmental factors, ensuring durability and safety. This simple yet effective mechanism makes magnetic switch sensors widely used in security systems, industrial automation, consumer electronics, and automotive applications.

Three types of reed switch sensors

There are three types of reed switch sensors: normally open, normally closed, and latching. All three types can use traditional magnets or electromagnets, and each type of magnet has a slightly different driving method.

Normally open reed switch sensor

As the name suggests, these reed switch sensors are normally in the open (disconnected) position. When the magnet in the sensor reaches the reed switch, it polarizes each connection into opposing electrical charges. The new attraction between the two connections forces them to close the circuit together. Equipment with normally open reed switch sensors is mostly in a power-off state unless the magnet is intentionally moving.

Normally closed reed switch sensor

Conversely, normally a closed pneumatic reed switch sensor creates a closed circuit as their default position. The reed switch only opens and breaks the circuit connection when the magnet triggers a specific attraction force. Current flows through the normally closed reed switch until the magnet forces the two reed switch connectors to share the same magnetic pole, separating the two components.

Latching reed switch sensor

This type of reed switch magnetic sensor for cylinders combines the functions of normally open and normally closed reed switch sensors. The latching reed switch sensor is not defaulted to being powered or unpowered, but rather held in the last position until forced to change. If the electromagnet forces the switch into an open circuit state, the switch will remain in an open circuit state until the electromagnet is powered and closes the circuit, and vice versa. The operation and release points of the switch will produce natural hysteresis, locking the reed switch in place.

The reed switch is a unique technology that can be used in almost any environment due to its fully sealed characteristics. Although the structure of the reed switch is simple, its production process includes multiple processes. Over the years, the size of the reed switch has evolved from approximately 50 mm (2 inches) to as small as 6 mm (0.24 inches), making it applicable to more fields, especially meeting the needs of radio frequency and fast time-domain applications.