Glossary · Motion control and drives
Encoder
Also known as: Rotary encoder, Shaft encoder
German: Drehgeber
In motion control, an encoder is a sensor that converts the position or motion of a shaft or linear scale into electrical signals, either as incremental pulses or as an absolute position value, for use as feedback by a drive or controller.
- Motion control
In one sentence
An encoder converts shaft or linear position into signals, incremental pulses or absolute values, used as feedback for drives and controllers.
Example
A servo motor has a multiturn absolute encoder, so the axis knows its position after power-up and does not need to be homed.
How it applies
- Engineering: Encoders are chosen by type (incremental, singleturn or multiturn absolute), resolution, interface (for example A/B quadrature, SSI, BiSS, EnDat, HIPERFACE DSL) and environment. Safety-rated encoders exist for drive-integrated safety functions.
- Commissioning: Scaling, counting direction and, for absolute encoders, the position offset are set up; incremental systems need Homing.
- Maintenance: Replacing an encoder can change the offset and the commutation angle, so the axis must be re-referenced before operation.
- Documentation: State in the maintenance instructions which settings must be restored after an encoder replacement and how to check the position afterward. Describe encoder alarms in the fault list with cause and remedy.
Encoder vs. resolver
A resolver is an analog, transformer-based rotary position sensor, robust against heat and vibration. An encoder usually works optically or magnetically and provides digital signals with higher resolution.