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Incremental vs. Absolute Encoders: Key Differences Explained

Differences Between Incremental and Absolute Encoders

I. What Is an Encoder

An encoder is a sensor component that converts mechanical motion signals into electrical signals. It is mainly used to detect rotation angle, displacement, speed, or direction. Based on the output signal type, encoders fall into two major categories:

  • Incremental Encoder: Outputs pulse signals that require counting to determine position.

  • Absolute Encoder: Outputs a unique position code directly, with each position having a unique value.

II. Working Principle and Features of Incremental Encoders

  1. Principle

    When the shaft rotates, an incremental encoder generates A, B, and Z pulse signals. Devices count these signals in real-time to determine position and direction.

  • A/B phase difference determines rotation direction.

  • Z signal (zero pulse) serves for reference or resetting.

  1. Features

  • Requires zeroing or referencing upon each power-up.

  • Fast response, suitable for high-speed rotation.

  • Simple structure and low cost.

  • Cannot retain position after power loss.

III. Working Principle and Features of Absolute Encoders

  1. Principle

    An absolute encoder assigns a unique binary or Gray code value to every angular position. Even after power failure, it retains the current position.

  • Single-turn absolute encoder: Identifies each position within one full rotation.

  • Multi-turn absolute encoder: Tracks position across multiple rotations.

  1. Features

  • No need for zeroing after power loss.

  • Accurate data, compatible with bus communication.

  • Ideal for systems requiring high precision and stability.

  • Higher cost compared to incremental encoders.

IV. Key Differences Between Incremental and Absolute Encoders

  • Output: Incremental encoders output pulse signals; absolute encoders provide unique position codes.

  • Power Loss: Incremental encoders lose position info; absolute encoders retain it.

  • System Complexity: Incremental types rely on external processing; absolute types offer integrated position data.

  • Application Goals: Incremental is for speed/relative position; absolute is for precise positioning with power-off protection.

  • Cost vs. Precision: Absolute encoders are more precise and expensive; incremental types are cost-effective.

V. Practical Application Comparison

Incremental Encoders Used In:

  • High-speed motor feedback control

  • Industrial conveyor belt counting

  • Basic position detection systems

  • Cost-sensitive applications

Absolute Encoders Used In:

  • Smart servo motors

  • CNC machines

  • Robotic arms

  • Smart AGV navigation systems

VI. Selection Advice

When choosing an encoder, consider:

  • Is zeroing allowed after power loss?

  • Required positioning accuracy and repeatability

  • Whether the system can process pulse signals

  • Budget and expected equipment lifespan

  • Need for bus communication (CANopen, Profibus, etc.)

VII. Conclusion

Though both incremental and absolute encoders are position sensors, they differ significantly in output principles, system integration, and applications. Understanding their distinctions helps improve the reliability and control efficiency of automation systems.

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