Choosing Between Incremental and Absolute Rotary Encoders for Automation
Publish Date: November 01, 2025
In automation systems, rotary encoders are pivotal for converting shaft rotation into measurable electrical signals to control position, speed, and direction. Two fundamental types of rotary encoders are incremental and absolute, each offering distinct operational benefits and suited for different application needs. Selecting the right encoder type is crucial for ensuring system accuracy, reliability, and safe operation in industrial automation.
Understanding Incremental Rotary Encoders
Incremental rotary encoders generate pulses as the shaft rotates, providing relative position information by counting the pulses from a known reference or zero point. They output two quadrature signals (channels A and B), which are 90 degrees out of phase, enabling detection of rotation direction and speed. An optional index channel (Z) signals a reference position once per revolution.
However, incremental encoders do not retain position information when power is lost. After a power outage, the system must find the home position (index) to establish an absolute location before meaningful positional data can be derived. These encoders are prized for their cost-effectiveness, high resolution, and are widely used in applications where speed or relative motion tracking is sufficient, such as conveyor systems, motor feedback, and printing machinery.
Understanding Absolute Rotary Encoders
Absolute encoders provide a unique digital code for each shaft position, delivering exact position feedback even after power loss. They achieve this through an optical or magnetic sensing mechanism reading a coded disc, which produces a multi-bit digital word representing the absolute angle. Absolute encoders come in single-turn and multi-turn forms, suitable for short-range or extended-range positional feedback, respectively.
In automation requiring high reliability and precise position awareness immediately upon startup — such as robotics, CNC machines, and safety-critical systems — absolute encoders are favored. They reduce downtime and eliminate the need for mechanical homing procedures post power failure.
Key Differences and Applications
| Feature | Incremental Encoder | Absolute Encoder |
|---|---|---|
| Position feedback | Relative (pulse count from reference) | Absolute (unique position code) |
| Power loss impact | Position information lost, needs homing | Position retained, immediate feedback |
| Output signals | Pulses (A, B, optional index Z) | Digital multi-bit position code |
| Typical applications | Speed measurement, conveyor control, basic motor feedback | Robotics, CNC, safety-critical automation |
| Cost | Generally lower | Generally higher due to complexity |
| Complexity and integration | Simpler, fewer integration needs | More complex, better suited for sophisticated systems |
Choosing the Right Encoder for Your Application
The decision depends on your system requirements for accuracy, reliability, and cost. For systems where relative motion tracking and cost are critical, incremental encoders are ideal. For applications demanding precise, immediate, and fail-safe position feedback, absolute encoders are the preferred choice. Consider the operational environment, budget, and system complexity when making your selection.
Product Examples from MISUMI India
| Product | Description | Link |
|---|---|---|
| Rotary Encoder Incremental Type High Resolution [E6D-C] | A high resolution incremental rotary encoder suitable for precise speed and position feedback, featuring quadrature output signals. | Link |
| Rotary Encoder Absolute Robust Type [E6F-A] | Robust absolute rotary encoder offering reliable position feedback with options for single-turn and multi-turn configurations. | Link |
| Rotary Encoder Absolute Robust Type [E6C3-A] | Another model offering absolute position feedback with high accuracy, suitable for demanding automation applications. | Link |
