Many buyers ask: should I choose an "incremental" or an "absolute" encoder? The names differ by only two words, but in practice they behave very differently. Here's a plain-language explanation.
1. Difference in Principle
- Incremental encoders: output A/B phase pulses; position is obtained by counting pulses — a relative position. They do not "remember" position — after power-off, position resets to zero and a homing/return-to-reference operation is needed.
- Absolute encoders: every position has a unique code value, so position is not lost after power-off — on power-up the absolute position can be read directly, with no homing needed.
2. Pros and Cons
| Dimension | Incremental | Absolute |
|---|---|---|
| Position memory after power-off | No — needs homing | Yes — read directly on power-up |
| Response speed | Fast | Depends on interface (parallel/serial) |
| Interference resistance | Fair (pulse counting is susceptible) | Strong (serial digital transmission) |
| Cost | Low | High |
| Typical interfaces | A/B/Z pulses (RS422/1Vpp) | RS485, SSI, BISS, etc. |
3. How to Choose?
- General machine feed, spindle feedback, general automation: incremental is sufficient and economical — one homing cycle is all you need. KOSEND EIS/EIH optical encoders and DA ring encoders (RS422/1Vpp) fall in this category, resolution 100-5000 pulses (ring series up to 150k pulses custom).
- Robot joints, lines needing fast power-up recovery, anti-power-loss applications: choose absolute. KOSEND DT series magneto-electric encoders use RS485 digital communication, resolution up to 29.36M, overall accuracy ±0.0011°; cycle and continuous counts are directly readable after power-off — ideal for such demanding applications.
4. Advice for Buyers
- Ask the system first: whatever interface your drive/CNC supports, choose that interface.
- Then calculate accuracy: incremental = "pulses per rev × subdivision"; magnetic/gear types can also boost output resolution via interpolation.
- Finally look at the environment: oily/vibrating environments favor magnetic types (fully potted, IP67); clean environments favor optical for higher accuracy.
Need selection help? Call KOSEND at 400-100-6802 with your equipment and accuracy requirements — we'll match the right encoder solution.