The term encoder describes a technical device for the optical, mechanical or magnetic detection of movements on the basis of electric signals. A distinction is made between rotary and linear encoders. A rotary encoder is attached to rotating components. Linear encoders are suitable for use with components that perform straight movements. The category is further divided into absolute and non-absolute encoders. A representative of the latter is the incremental encoder. Absolute encoders are also called absolute value devices.

Depending on their concept, different encoders are suitable for different applications. Incremental encoders can be used, for example, to measure data from a motor or as an input device to set certain parameters, such as frequency or volume of a radio. They work by detecting changes in position (linear) or angle (rotating). Absolute encoders are used, among other things, in position measurement technology or as displacement encoders on machine tools. Technological progress permits precise measurements for all types of high-quality encoders.