Professional Selection Guide for Servo Motor Encoders

(Including Motor Pole Number & UVW Commutation Signal Matching | Taking DELBURG JRT Series as Example)

This article analyzes the core logic of servo motor encoder selection based on industrial practical applications, focusing on two critical matching 

factors: motor pole number and UVW commutation signal. It balances professionalism and practicality to help engineers complete efficient selection and avoid matching errors. The final chapter takes the DELBURG JRT series as a practical application case.

1. Basic Classification: Incremental vs. Absolute Encoder

1.1 Incremental Encoder

Working principle: Output A/B quadrature pulses and Z-phase zero signal to realize relative position feedback through pulse counting.

Key features: Cost-effective, excellent high-speed response, compact structure; position data will be lost after power failure, and homing is required after power-on with potential cumulative errors.

Application: Conveyors, packaging machinery, fans, pumps and general speed and positioning equipment.

1.2 Absolute Encoder

Working principle: Each mechanical position corresponds to a unique digital code, enabling direct reading of absolute position after power-on.

Key features: Power-off position retention, no cumulative error, high positioning stability and control accuracy; higher cost and complex structure.

Application: Robots, CNC machine tools, semiconductor equipment, AGVs and high-precision multi-axis synchronous scenarios.

1.3 Classification by Sensing Principle

Photoelectric Encoder: High precision and resolution, stable signals, suitable for clean workshops and precision equipment.

Magnetic Encoder: Excellent oil resistance, dust resistance and vibration resistance, adaptable to harsh industrial working conditions.

Resolver: Ultra-high temperature resistance and strong anti-interference, widely used in special extreme working conditions.

2. Core Parameter Selection Key Points

2.1 Resolution

Incremental type: 1000～10000 PPR, supporting quadruple frequency subdivision.

Absolute type: 12～23 bit; higher bits represent higher position segmentation accuracy.

Selection basis: Determine reasonable resolution according to transmission ratio, lead screw lead and system positioning tolerance.

2.2 Maximum Speed & Response Frequency

The encoder response frequency must match the maximum motor speed with a margin of 20%~30%, to prevent pulse loss and low-speed jitter under high-speed and frequent start-stop conditions.

2.3 Electrical Interface & Communication Protocol

Incremental signal: TTL, HTL, A/B/Z differential signal; differential output features strong anti-interference for long-distance transmission.

Absolute protocol: SSI, BiSS-C, EnDat, EtherCAT, CANopen.

Note: The interface protocol must be fully compatible with the servo driver to avoid communication failure and signal distortion.

2.4 Environmental Adaptability

Protection grade: IP65 for standard workshops, IP67 for spray and oil mist environments, IP69K for high-pressure washing scenarios.

Operating temperature: Standard range -20℃～85℃; wide-temperature models for extreme temperature environments.

Vibration resistance: Magnetic encoders and high-shock-resistant structures are preferred for heavy-duty industrial equipment.

2.5 Mechanical Structure

Mounting forms include hollow shaft, solid shaft and flange installation. The shaft diameter, outline size and cable outlet mode shall be matched with the servo motor to avoid secondary processing and installation deviation.

2.6 Servo Motor Pole Number

The motor pole number directly affects low-speed stability, torque output and encoder matching:

4-pole motor: Strong versatility, balancing high speed and medium and low-speed operation.

6-pole / 8-pole motor: High low-speed torque and stable operation, suitable for precision automation equipment.

12-pole and above: Ultra-low speed and high torque; high-resolution encoders are required to optimize low-speed pulsation.

Conclusion: Motors with more poles have higher requirements for encoder signal stability and anti-interference.

2.7 UVW Commutation Signal

As the core signal of servo vector control, UVW magnetic pole signal is used for the driver to identify the rotor position and complete phase commutation.

Core functions: Realize fast start-up without phase searching, optimize low-speed torque smoothness, and suppress startup jitter.

Matching requirement: The UVW signal cycle must correspond strictly to the motor pole pairs; mismatching will cause abnormal commutation and insufficient torque.

Selection rule: High-precision and high-torque servo motors must be equipped with UVW commutation signals.

3. Standard Selection Process

Confirm power-off position retention demand to select incremental or absolute type.

Define positioning accuracy indicators to determine encoder resolution.

Verify maximum motor speed and calculate matching response frequency margin.

Check motor pole pairs to confirm UVW commutation signal specifications.

Select encoder type and protection level according to on-site environmental conditions.

Confirm signal interface and communication protocol compatibility with the driver.

Match mechanical size and mounting structure for on-site assembly.

4. Recommended Selection for Typical Scenarios

General packaging & textile machinery: 4-pole motor + 2500PPR incremental encoder with UVW signal

Robots & precision platforms: 6/8-pole motor + high-bit absolute encoder

High-speed spindle equipment: 4-pole high-speed motor + high-frequency incremental encoder

Severe working conditions with oil and dust: Vibration-resistant magnetic encoder complete with UVW signal

5. Practical Selection Case: DELBURG JRT Series

The DELBURG  JRT series is a high-performance hollow-shaft incremental servo encoder, fully optimized for industrial servo systems. It integrates position feedback and commutation output, and serves as a universal and reliable matching solution for mainstream servo motors.

Core Specifications

Resolution: Optional 1000～10000 PPR to cover multi-level accuracy requirements.

Signal output: A/B/Z differential signal + standard UVW commutation signal, with strong anti-interference capability.

Mechanical design: Hollow shaft structure, suitable for rear installation of servo motors with high coaxiality.

Environmental performance: IP65 protection grade, wide temperature adaptation, stable operation in complex factory environments.

Speed capacity: High-frequency response design, supporting continuous operation of high-speed servo motors up to 6000rpm.

Adaptation with Motor Pole Number

For 4-pole general servo: The JRT series realizes fast rotor position identification, ensuring smooth startup and stable daily operation.

For 6/8-pole low-speed precision servo: High-resolution models cooperate with customized UVW signals to reduce low-speed fluctuation and improve motion stability.

For multi-pole high-torque servo: Accurate UVW phase commutation suppresses torque pulsation and effectively improves overall control accuracy.

Product Overview

With standardized dual output of position signal and UVW commutation signal, the DELBURG  JRT series is compatible with 4/6/8/12-pole servo motors. The universal hollow shaft structure supports convenient replacement and installation, covering general automation, precision processing and heavy-duty equipment scenarios.

6. Summary

Scientific encoder selection must comprehensively consider accuracy, speed, interface, environment, motor pole characteristics and UVW commutation signal matching. Reasonable parameter matching can effectively improve servo operation stability and avoid hidden equipment risks.

With comprehensive parameter matching and strong scene adaptability, the DELBURG  JRT series provides a mature and reliable reference for standardized selection of industrial servo encoders.