Jun 07, 2024

What are the Two Main Types of Rotary Encoders?

There are two primary kinds of rotary encoders: absolute and incremental. Both types of encoders are used to measure the angular position in a variety of industries and applications, such as machine tools, automation, packing, printing, and label and marking equipment.

Incremental vs. Absolute Encoders

Incremental encoders and absolute encoders are both used to measure the position, speed, and direction of a rotating shaft, but they operate on fundamentally different principles and offer distinct advantages depending on the application.

Incremental Encoders

How They Work:

  • Generate a series of pulses as the shaft rotates.
  • The number of pulses per revolution determines the resolution.
  • Position is calculated by counting the pulses from a known reference point.

Key Characteristics:

  • Simplicity: Typically less complex and less expensive than absolute encoders.
  • Power Loss: Lose position information if power is interrupted.
  • Resolution: Can offer high resolution by increasing the number of pulses per revolution.
  • Direction Sensing: Use quadrature encoding (A and B channels) to determine direction of rotation.
  • Index Pulse: Some incremental encoders have a Z channel, providing a single pulse per revolution for a reference point.


  • Speed and direction measurement.
  • Position tracking in systems where power loss is not critical.
  • Simple feedback loops in industrial machinery.

Absolute Encoders

How They Work:

  • Provide a unique code for each position within a single or multi-turn rotation.
  • Position is available as soon as power is applied, without needing a reference point.

Key Characteristics:

  • No Loss of Position: Retain position information even if power is lost and restored.
  • Single-Turn vs. Multi-Turn:
    • Single-Turn: Measures position within one revolution.
    • Multi-Turn: Tracks position across multiple revolutions.
  • Resolution: Can offer high resolution, determined by the number of bits in the output code.
  • Output: Provides a binary or gray code, representing the absolute position.


  • Precise position control systems.
  • Applications where the position must be known immediately upon startup.
  • Complex motion control systems requiring accurate position feedback.


Incremental Encoder:

  • Like a tally counter where you count each step from a known starting point. If you lose power, you lose count and need to start over.

Absolute Encoder:

  • Like a GPS system where you always know your exact location, regardless of power cycles.

Advantages and Disadvantages

Incremental Encoders:

  • Advantages:
    • Lower cost.
    • Simpler design and implementation.
    • Suitable for high-speed applications.
  • Disadvantages:
    • Loses position information if power is interrupted.
    • Requires a homing procedure to establish a reference point.

Absolute Encoders:

  • Advantages:
    • Retains position information even after power loss.
    • No need for a homing procedure.
    • Provides precise and immediate position information.
  • Disadvantages:
    • Higher cost.
    • More complex design and implementation.
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