Incremental Rotary Encoders: How They Work and Why They Matter
What Is an Incremental Rotary Encoder?
An incremental rotary encoder is a position feedback device that emits a specific number of pulses per revolution (PPR) at equal intervals. These pulses can also correspond to linear movement in inches or millimeters. Incremental encoders are widely used in industrial automation, robotics, and motion control systems for precise positioning.
How Incremental Encoders Work
Incremental encoders generate output signals that represent movement rather than absolute position. Here’s how they function:
Single-Channel Output
A single-channel output is ideal for applications where the direction of movement is irrelevant. It provides a simple pulse train for speed or distance measurement.
Two-Channel Quadrature Output
When direction matters, a two-channel output with a 90° phase shift is used. The phase difference between channels determines the direction of rotation. This is critical for processes involving reversal of motion or vibration, where accurate net position must be calculated.
Why Quadrature Counting Improves Resolution
Machine vibrations can cause unidirectional encoders to produce false pulses, misleading control systems. Using a quadrature counter prevents this issue.
- x2 Resolution: Count rising and falling edges of one channel.
- x4 Resolution: Count both edges on both channels for maximum precision.
Position Display and Homing
Incremental encoders require a reference point after power loss or interference. A marker signal (also called index or Z-channel) is generated once per revolution at a known position. This enables homing sequences and accurate initialization of position counters.
Applications of Incremental Rotary Encoders
- Industrial Automation: Speed and position feedback for motors and conveyors
- Robotics: Precise motion control in dynamic environments
- Packaging & Printing: Synchronization of cutting and feeding operations
- Machine Tools: Accurate spindle and axis positioning
Advantages and Limitations
Advantages:
- High resolution and cost-effective
- Simple signal processing
Limitations:
- Requires homing after power loss
- Sensitive to environmental interference without proper design
Hengstler Solutions for Incremental Rotary Encoders
Hengstler’s ICURO series offers robust incremental encoders designed for demanding industrial environments:
- High PPR options for fine resolution
- Rugged construction for vibration and shock resistance
- Wide range of interfaces for easy integration