Incremental or absolute encoder - which one fits?
Incremental encoders count pulses, absolute encoders always know their position - even right after switch-on. This guide compares both principles, explains singleturn and multiturn plus interfaces, and shows when position retention after a power loss justifies the higher price.
View encodersHow do incremental and absolute differ?
An incremental encoder delivers a fixed number of pulses per revolution (for example 1024 or 5000) via channels A and B. The controller counts these pulses to derive distance, speed and direction. It does not know the absolute position - only the change since power-on.
An absolute encoder instead outputs a unique digital value for every angular position, usually from a coded glass or magnetic disc. After switch-on the position is immediately known, without the machine having to perform a homing run first.
- Incremental: channels A, B and reference pulse Z, counted in the controller.
- Absolute singleturn: unique value within one revolution (0‑360 degrees).
- Absolute multiturn: also counts the full revolutions.
- Absolute retains its position even when de-energised.
When does position retention justify the price?
Absolute encoders cost more but save the homing run and the clearance it needs. The extra cost pays off wherever a homing move is dangerous, slow or simply impossible - for heavy axes, hoists, or when production must resume immediately after a power loss.
Which resolution and interface do I need?
The resolution of an incremental encoder is stated in pulses per revolution (PPR), that of an absolute one in bit. 12 bit equals 4096 steps per revolution, high-end optical encoders reach up to 22 bit. The interface must match the controller.
- Incremental: HTL (push-pull) or RS-422/TTL for longer cables and higher frequencies.
- Absolute serial: SSI - robust, simple and widely used.
- Absolute over fieldbus: PROFINET, EtherCAT, CANopen or PROFIBUS.
- Modern drives: BiSS-C or EnDat for fast digital position transfer.
Frequently asked questions
Does an incremental encoder lose its position on power loss?
Yes. It only counts pulses from switch-on. After a power failure the absolute position is unknown and the machine must run a reference move to the index pulse.
What is the difference between singleturn and multiturn?
Singleturn gives a unique value within one revolution. Multiturn also counts the full revolutions and keeps them even when de-energised - ideal for spindles, hoists and gearboxes.
When is an absolute encoder worth it?
When a homing run is too slow, dangerous or impossible - for heavy axes, cranes, or when production must resume immediately after a failure.
Which interface is the right one?
It depends on the controller. HTL/TTL for incremental, SSI for simple absolute applications, PROFINET or EtherCAT for networked plants, BiSS-C or EnDat for modern servo drives.
Looking for the right encoder?
We supply incremental and absolute rotary encoders with singleturn and multiturn, the matching interface and protection rating - including sizing advice.
Both principles
Incremental and absolute from one source.
Multiturn available
Position held safely across many turns.
Rugged designs
Optical and magnetic up to IP67.
Expert advice
We help with resolution and interface.