What are the Two Main Types of Rotary Encoders?

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.

Applications:

• 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.

Applications:

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