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Article 2: Servo Motor Encoders – Key Parameters, Communication Protocols, Industrial Applications and Selection Guide
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Knowledge
Release Time：
2026-03-10
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Abstract
On the basis of understanding encoder classification and working principles, mastering their key parameters, communication protocols and typical applications is crucial for selecting the right encoder and ensuring servo system stability. This article focuses on key parameters (resolution: single-turn 17/23/25/26 bit, multi-turn 16 bit; precision: up to 10 arcseconds; outer diameter: 35, 46, 47, 48, 50, 56 mm; motor compatibility: 40/60/80/110 mm motors), details RS485 NRZ protocol, analyzes typical industrial applications, provides a scientific selection guide, and looks forward to development trends, helping engineers and manufacturers better apply servo encoders.
1. Introduction
As the core feedback component of servo systems, encoders' parameters and protocols directly affect control effect, while their compatibility with motors and adaptability to scenarios determine equipment stability. With the upgrading of industrial automation, encoders are required to have high precision, small size, standardized protocols, strong environmental adaptability and wide compatibility. On the basis of the previous article, this article focuses on parameters, protocols, applications and selection, helping readers select the most suitable encoder to improve system performance and reduce costs.
2. Key Performance Parameters of Servo Encoders
Encoder performance parameters are the core basis for evaluation, mainly including resolution, precision, outline dimensions and motor compatibility.
2.1 Resolution: Single-Turn and Multi-Turn
Resolution refers to the minimum detectable angular displacement, expressed in bits. Single-turn resolution (17/23/25/26 bit) determines control fineness: 17 bit (131072 positions/turn) for general precision; 23 bit (8388608 positions/turn) for medium-high precision; 25/26 bit for micron-level high-precision positioning. Multi-turn resolution is 16 bit (up to 65536 turns), suitable for multi-loop motion (e.g., lifting equipment, robotic arms), retaining position data after power failure to avoid homing.
2.2 Precision: Up to 10 Arcseconds
Precision is the deviation between measured and actual angles, expressed in arcseconds (smaller = higher precision). High-end integrated photoelectric and opto-magnetic hybrid encoders reach up to 10 arcseconds for high-end equipment; magnetic encoders (20-60 arcseconds) meet most general industrial needs. Installation accuracy and operating environment also affect precision, requiring correct installation and suitable working conditions.
2.3 Outline Dimensions and Motor Compatibility
Standardized outer diameters (35, 46, 47, 48, 50, 56 mm) match 40, 60, 80, 110 mm frame servo motors: 40 mm motors with 35 mm encoders; 60/80 mm motors with 46/47/48/50 mm encoders; 110 mm motors with 50/56 mm encoders. Encoders have small size and compact structure, suitable for equipment with limited installation space, reducing weight and improving flexibility.
3. Communication Protocol: RS485 NRZ
RS485 NRZ is the mainstream industrial serial protocol for servo encoders, acting as a bridge between encoder and servo drive. It adopts differential transmission, with strong anti-interference, long-distance transmission (hundreds of meters), simple wiring (two signal lines), high reliability and strong compatibility with most servo drives, realizing plug-and-play. Its fast response ensures real-time data transmission and high-dynamic servo response, widely used in industrial automation scenarios.
4. Typical Industrial Applications
Different encoders suit different scenarios, combined with their characteristics and parameters:
4.1 Industrial Robots and Collaborative Robots
Robot joints require high precision, small size and stability. Opto-magnetic hybrid encoders (10 arcseconds, 48/50/56 mm outer diameter, 23-26 bit single-turn, 16 bit multi-turn) are preferred for high-end collaborative/surgical robots. Separated photoelectric and high-end integrated magnetic encoders are used for general industrial robots, matched with 60/80/110 mm motors to ensure precise, stable movement.
4.2 CNC Machine Tools and Precision Machining
CNC axes need ultra-high precision. Integrated photoelectric and opto-magnetic hybrid encoders (10 arcseconds, 25/26 bit, RS485 NRZ, 35/48 mm) are main choices, matched with 40/80 mm motors, improving machining accuracy, surface quality and efficiency for machining centers, lathes and grinders.
4.3 Packaging, Printing and Textile Machinery
These high-speed equipment require anti-pollution, vibration resistance and small size. Separated magnetic encoders (17/23 bit, 46/48 mm, 60/80 mm motors) have high cost-performance and long service life; separated photoelectric encoders have high precision and vibration resistance, ensuring high-speed stable operation and reducing downtime.
4.4 New Energy and Automotive Equipment
These harsh-environment equipment require reliability and vibration resistance. Integrated/separated magnetic encoders (17/23 bit, 16 bit multi-turn, RS485 NRZ, 35/48 mm, 40/80 mm motors) are preferred, with dust/oil resistance and long service life, suitable for new energy vehicle drives and automotive AGVs.
4.5 Precision Test and Measuring Instruments
These require ultra-high precision. Integrated photoelectric and opto-magnetic hybrid encoders (10 arcseconds, 25/26 bit, 35/46 mm, 40/60 mm motors) provide high-precision feedback, ensuring accurate, traceable test results for coordinate measuring machines and precision angle instruments.
5. Encoder Selection Guide
Scientific selection steps:
1. Determine precision: 10 arcseconds (photoelectric/opto-magnetic); 20-60 arcseconds (magnetic).
2. Determine environment: clean (photoelectric); dusty/oily/vibrant (magnetic/opto-magnetic).
3. Determine structure: limited space/high integration (integrated); high speed/vibration (separated).
4. Confirm size compatibility: match motor frame with encoder outer diameter (40→35 mm; 60/80→46/47/48/50 mm; 110→50/56 mm).
5. Confirm protocol: RS485 NRZ for high compatibility and anti-interference.
6. Development Trend
Servo encoders will develop toward higher precision (26+ bit, <10 arcseconds), smaller size (35 mm and below), opto-magnetic hybrid mainstream, intelligentization (self-calibration, condition monitoring) and standardization (unified interfaces/protocols), supporting industrial automation upgrading.
7. Conclusion
Servo encoders are core components of motion control systems, with key parameters (resolution, precision, size, compatibility) and RS485 NRZ protocol determining their applicability. Different encoders suit different fields: integrated photoelectric for high-precision clean environments; separated photoelectric for high-speed/vibration; integrated magnetic for cost-effective harsh environments; separated magnetic for large-scale harsh applications; opto-magnetic hybrid for high-end equipment. The selection guide helps engineers choose the right encoder, and future innovation will drive encoder performance upgrading, supporting intelligent manufacturing development.
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