Encoders for signal formation from movements work optically, magnetically or mechanically with contacts. Transducers or input devices detect the current position of a shaft or drive unit and output it as an electrical signal. There are two types of encoders: rotary and linear encoders. Rotary encoders are mounted on rotating components, for example on a motor shaft. Linear encoders are typically mounted on components with straight movements.
Encoders have incremental, countable or even absolute material measures as line patterns (light barrier), magnetization or contacts. In the case of permanent magnetization, the magnetic field modulation can be controlled by means of AMR, GMR, hall sensors or inductive sensors can be evaluated. For incremental inductive sensors, non-magnetic toothing is often sufficient.
Absolute encoders operate on the basis of material measures which assign a unique signal pattern to each position (see absolute encoders).
Non-absolute measuring encoders are called incremental encoders. They are used on motor shafts but also as input devices for digitally operating devices, to set parameters (e.g. volume) or to control motor movements manually (e.g. at CNC control systems).
With the help of the output signal of an encoder, a suitably equipped drive unit can carry out reproducible movements and – in the case of an absolute encoder – move back exactly to the starting position (reference position) even after the machine has been switched off. Incremental encoders require an additional encoder to find the reference position, for example a limit switch. An example of a linear incremental encoder is the optical scanning of a line pattern applied to a strip in a printer which allows the print carriage to perform a defined movement along the line.
Source: German Wikipedia