Summary: This article introduces the basic structure, working principle, and application areas of magnetic rotary encoders. In a magnetic rotary pulse encoder, the magnetic sensor generates pulse signals by detecting changes in the magnetic field. Compared with optical encoders, magnetic encoders use magnetic sensing to generate pulses, thereby providing stronger resistance to contamination and better environmental adaptability. Simply put, pulses are the means by which the encoder converts rotational movement into electrical signals, providing important feedback on angle, position, speed, and direction, enabling precise monitoring and control of rotary motion.

1) Types of Magnetic Rotary Encoders and Their Working Principles

Magnetic rotary encoders can be classified into three types based on their structure, each with a different working principle (for ease of understanding, all output electrical signals are collectively referred to as pulse signals in this article):

1. Gears with Magnetic Teeth Sensor
   This type of encoder generates voltage signals when the magnetic gear teeth pass by the sensor. However, due to the physical limitations on the number of gear teeth, such designs typically produce 120 or 240 voltage pulses per revolution.
2. Magneto Resistive Encoder
   This encoder consists of a magneto resistive sensor and a wheel or ring with alternating magnetic regions. These alternating magnetic regions can be physical areas or created by a thin-film resistor array. As the wheel or ring rotates, the magnetic regions pass by the sensor, causing resistance changes that generate pulse signals. This type of encoder is relatively larger and more precise, but it can be challenging to integrate.
3. Hall-Effect Magnetic Encoders
   Similar to the magneto resistive encoder, except that the magneto resistive sensor is replaced by a Hall-effect sensor, which is a semiconductor material that generates pulses when it passes through a magnetic field. This design allows the integration of sensors and processors, achieving the highest precision currently available, although it comes at a higher cost.

2) The Importance of Filtering

Between the encoder structure and application, an important concept needs to be mentioned—filtering. Filtering is a critical factor that affects the final measurement accuracy of an encoder, though it is often not emphasized in many articles. Filtering acts on the pulse signal feedback process and is one of the methods manufacturers use to improve measurement accuracy.

Each pulse signal has a specific duration, and if more pulses are to be generated per rotation (e.g., by increasing the number of pins), the duration of each pulse must be shortened. For a magneto resistive sensor, the pulse duration after filtering can be as short as 20 microseconds (μs), which is very brief and often overlooked by many buyers.

3) Application Areas of Magnetic Rotary Encoders

1. Position Detection
   Used to determine the position of a rotating shaft, commonly found in industrial automation equipment and robots for precise measurement of moving parts.
2. Speed and Direction Monitoring
   By outputting pulse signals, the speed and direction of rotating objects can be measured, making it suitable for motor feedback control and speed monitoring of various rotating machinery.
3. Automation Control Systems
   Widely used in servo systems, machine tools, and conveyor equipment to ensure precise control of the rotation angle and movement of shafts.
4. Angle Measurement
   Used in applications that require measuring rotation angles, such as in medical devices and wind turbines.
5. Incremental Position Feedback
   Incremental encoders generate pulse signals that provide feedback to controllers, enabling precise positioning and incremental motion control, commonly used in CNC machine tools and printing equipment.

4) Conclusion

The main advantage of magnetic rotary encoders lies in their use of magnetic sensing, which provides strong resistance to interference and allows them to operate reliably in harsh environments. Therefore, they are widely used in demanding industrial applications. Additionally, compared with optical encoders, magnetic encoders are less affected by dust and oil contamination, making them suitable for a broader range of applications.