Types of Magnetic Sensor Applications in the Pneumatic Industries

Magnetic Sensor Switch in Industrial Automation

In pneumatic industrial automation, compressed air is used to achieve energy conversion and mechanical motion output, in which the piston rod or magnetic coupling slider drives the load.For complex pneumatic circuits, motion detection of each key pneumatic component becomes important especially for cylinder.It is not only used for detecting abnormal states but also serves as the reference signal for the control system.

In the entire pneumatic system, magnetic sensor switch provides position, status, and motion detection, ensuring precise control, safety protection, and efficient operation in industrial manufacturing.

Types of Magnetic Sensor switch in pneumatic cylinder

The magnetic sensors are usually embedded inside the piston of the pneumatic actuator to detect the position changes during piston movement. The types of sensors used in pneumatic actuators are as follows:

Reed Sensor:
This type of magnetic sensor is one of many types of sensor switches, also known as a limit magnetic switch.Inside a small glass tube, there are two separated metal reeds that mechanically open or close.When a magnetic field approaches, the metal reeds are attracted by the magnetic force and close together, completing the circuit.

Reed magnetic sensor can be used for cylinder stroke detection, limit sensor switch for valve and actuator, and linear slide table position detection.

Hall Sensor:
This type usually outputs either digital or analog voltage signals.Through the Hall effect, when a conductor or semiconductor is exposed to a magnetic field, a voltage change occurs, and the sensor converts that voltage change into an output signal.

Magnetoresistive Sensor:
This type works by detecting resistance changes, usually providing analog or digital signal outputs.

Working Principle of Magnetic Sensor

Reed Sensor

This sensor magnetic limit glass tube mainly consists of two thin nickel–iron alloy reeds that do not touch each other.When an external magnet approaches, the reeds become magnetized and attract each other until the contacts close, making the circuit conductive.
When the magnet moves away, the elasticity of the reeds separates the contacts again, returning to the open state.

Hall Sensor

When current passes through a conductor or semiconductor and a magnetic field is applied perpendicular to the current, the magnetic field exerts a Lorentz force on the moving charge carriers, causing them to deflect to one side.This creates a transverse voltage — known as the Hall effect.The output signal is positively correlated with the magnetic field strength; the stronger the magnetic field, the greater the output voltage.

Magnetoresistive Sensor

Based on the magnetoresistive effect, when a magnetic field is applied, the motion of electrons in the material changes the resistance value.This resistance change is converted through a bridge or amplifier circuit into a continuous voltage signal that reflects the magnetic field strength or position variation.

Advantages of Different Magnetic Sensors in Industrial Automation

Reed limit magnetic sensor 

Features:No internal circuit required, low cost, suitable for mass application, easy installation, stable and reliable in industrial environments.

Disadvantages: Mechanical contacts cause wear, slower response speed, not suitable for high-speed motion detection.

Digital Hall Magnetic Sensor

Features:No mechanical contact, no wear; stable for fast-moving cylinders or sliders; suitable for harsh environments.It can provide a digital signal (1 for magnetic field detected, 0 for no field) or an analog voltage signal (0–5V) representing field strength.

Disadvantages: Higher cost than reed sensors, requires power supply support.

Analog Magnetoresistive Sensor

Features:This sensor type detects magnetic field variation through resistance change.It has high measurement accuracy and can detect angular or micro-position changes.Commonly used in closed-loop control, precise position feedback, and high-accuracy automation systems.

Disadvantages: Sensitive to external magnetic interference, high cost, requires complex circuitry, and precise installation alignment.

Key Points to Consider When Selecting a Magnetic Sensor

Output signal type: Whether it outputs a digital signal (on/off) or an analog signal representing field strength.

Sensitivity and detection distance: Ensure the sensor can be reliably triggered within the target magnet's range.

Mounting method and space requirements: The sensors' size, mounting holes, and fixing method must match the pneumatic base components.

Environmental adaptability: Ability to operate under high temperature, dust, humidity, or vibration conditions.

Response speed and frequency: Choose Reed sensor switch for low-frequency operations and Hall sensor for high-frequency actions.

Electrical compatibility: Ensure Hall and Magnetoresistive sensors match the system's operating voltage.

Accuracy: Includes both numerical precision and magnetic alignment accuracy.

There are various types of magnetic sensors, but if the purpose is only to detect whether the piston rod within a stroke of several tens to hundreds of millimeters is in the “in-position” or “not-in-position” state, a Reed switch sensor is sufficient.

Service life and maintenance

Reed switches have mechanical contacts that wear out and require periodic inspection or replacement;Hall and Magnetoresistive sensors have longer lifespans and lower maintenance requirements.