How does a multi-turn absolute encoder integrate single-turn photoelectric sensing and multi-turn magnetic induction technology to achieve high-precision absolute position detection?
Release Time : 2026-02-05
In precision motion scenarios such as high-end servo control, robot joints, CNC machine tools, and wind power pitch systems, extremely high demands are placed on the accuracy, reliability, and power-off memory capability of position feedback. Traditional incremental encoders cannot provide absolute position information, while early multi-turn absolute encoders relied on mechanical gear sets to record the number of turns, resulting in defects such as wear, short lifespan, and poor shock resistance. The multi-turn absolute encoder innovatively integrates single-turn photoelectric sensing and multi-turn magnetic induction technology, achieving a single-turn resolution of 0.001° to a multi-turn counting capability of over 4096 turns without any mechanical transmission components, and supports power-off position memory, becoming an ideal solution for high-reliability absolute position detection.
1. High Precision per Turn: Photoelectric Encoding Establishes Angular Reference
The single-turn position is measured by an optical encoding system. A light source illuminates a high-precision glass or metal code disk, which is engraved with a grating pattern of thousands to millions of line pairs. The photodetector receives transmitted or reflected light signals and converts them into orthogonal square wave or sine/cosine analog signals. Through subdivision circuitry, high resolution of 17-bit or even 24-bit can be achieved. This part inherits the advantages of traditional photoelectric encoders: fast response, high accuracy, and good repeatability, providing a sub-arcsecond angle reference for the entire system.
2. Multi-turn Wear-free: Magnetic Induction Technology Achieves Turn Count Memory
The core challenge of multi-turn counting lies in how to record the number of rotations without batteries or mechanical structures. Solid-state multi-turn encoders solve this problem using non-contact magnetic induction technology: a permanent magnet is mounted on the main shaft, rotating synchronously with the shaft; a set of giant magnetoresistive or Hall effect sensor arrays are arranged nearby. When the shaft rotates, the direction of the magnetic field changes periodically, and the sensor outputs a corresponding electrical signal. Crucially, the system incorporates a low-power microcontroller that reads the magnetic sensor status instantly upon power-on and updates the turn count register using internal algorithms. More importantly, this counting data is stored in non-volatile memory, so even after a complete power outage, the position information can be retained for more than ten years, truly achieving "absolute position known upon power-on."
3. Dual-Technology Collaboration: Seamless Integration of Single-Turn and Multi-Turn Data
Single-turn angle and multi-turn counting do not operate in isolation but are deeply integrated through internal digital logic. Whenever the single-turn angle returns from 359.9° to 0°, the system automatically increments or decrements the multi-turn counter by 1 based on the rotation direction, ensuring continuous position without jumps throughout the entire stroke. The final output 32-bit absolute position code, with its "photoelectric angle determination, magnetic turn counting" architecture, avoids the limitations of pure magnetic encoders in single-turn accuracy and overcomes the shortcoming of pure photoelectric solutions in multi-turn counting.
4. Anti-interference and Reliability Design
Industrial environments are complex electromagnetic environments. The encoder circuit integrates multiple anti-interference measures: the power supply uses TVS diodes and LC filters; the signal lines use shielded twisted-pair cables with built-in ESD protection; the GMR sensor itself has a high signal-to-noise ratio and temperature stability; and the photoelectric section uses modulation and demodulation technology to suppress ambient light interference.
The multi-turn absolute encoder achieves an excellent balance between accuracy and robustness, high resolution and long stroke, and high-speed response and power-off memory through the ingenious integration of photoelectric and magnetic induction technologies. It abandons the vulnerable mechanical structure and redefines the reliability boundary of absolute position sensing with a fully electronic solution, providing a solid position sensing foundation for intelligent manufacturing, green energy and automated equipment.
1. High Precision per Turn: Photoelectric Encoding Establishes Angular Reference
The single-turn position is measured by an optical encoding system. A light source illuminates a high-precision glass or metal code disk, which is engraved with a grating pattern of thousands to millions of line pairs. The photodetector receives transmitted or reflected light signals and converts them into orthogonal square wave or sine/cosine analog signals. Through subdivision circuitry, high resolution of 17-bit or even 24-bit can be achieved. This part inherits the advantages of traditional photoelectric encoders: fast response, high accuracy, and good repeatability, providing a sub-arcsecond angle reference for the entire system.
2. Multi-turn Wear-free: Magnetic Induction Technology Achieves Turn Count Memory
The core challenge of multi-turn counting lies in how to record the number of rotations without batteries or mechanical structures. Solid-state multi-turn encoders solve this problem using non-contact magnetic induction technology: a permanent magnet is mounted on the main shaft, rotating synchronously with the shaft; a set of giant magnetoresistive or Hall effect sensor arrays are arranged nearby. When the shaft rotates, the direction of the magnetic field changes periodically, and the sensor outputs a corresponding electrical signal. Crucially, the system incorporates a low-power microcontroller that reads the magnetic sensor status instantly upon power-on and updates the turn count register using internal algorithms. More importantly, this counting data is stored in non-volatile memory, so even after a complete power outage, the position information can be retained for more than ten years, truly achieving "absolute position known upon power-on."
3. Dual-Technology Collaboration: Seamless Integration of Single-Turn and Multi-Turn Data
Single-turn angle and multi-turn counting do not operate in isolation but are deeply integrated through internal digital logic. Whenever the single-turn angle returns from 359.9° to 0°, the system automatically increments or decrements the multi-turn counter by 1 based on the rotation direction, ensuring continuous position without jumps throughout the entire stroke. The final output 32-bit absolute position code, with its "photoelectric angle determination, magnetic turn counting" architecture, avoids the limitations of pure magnetic encoders in single-turn accuracy and overcomes the shortcoming of pure photoelectric solutions in multi-turn counting.
4. Anti-interference and Reliability Design
Industrial environments are complex electromagnetic environments. The encoder circuit integrates multiple anti-interference measures: the power supply uses TVS diodes and LC filters; the signal lines use shielded twisted-pair cables with built-in ESD protection; the GMR sensor itself has a high signal-to-noise ratio and temperature stability; and the photoelectric section uses modulation and demodulation technology to suppress ambient light interference.
The multi-turn absolute encoder achieves an excellent balance between accuracy and robustness, high resolution and long stroke, and high-speed response and power-off memory through the ingenious integration of photoelectric and magnetic induction technologies. It abandons the vulnerable mechanical structure and redefines the reliability boundary of absolute position sensing with a fully electronic solution, providing a solid position sensing foundation for intelligent manufacturing, green energy and automated equipment.