An encoder is a sensor which turns a position into an electronic signal. There are two forms:
- Absolute encoders give an absolute position value.
- Incremental encoders count movement rather than position. With detection of a datum position and the use of a counter, an absolute position may be derived.
The position may be measured as either linear or angular position:
- A Linear encoder converts linear position to an electronic signal
- A Rotary encoder converts rotary position to an electronic signal