Encoder: Measuring device that converts the angular positions of a shaft into coded data.
On principle, a distinction is made between incremental and absolute encoders.
Based on a photoelectrically scanned graduated disc, incremental systems supply increments in the form of signal pulses to an electronic evaluation system [up to 10000 pulses per revolution]. Incremental encoders are ideally suited for speed and angle detection. With motion systems, they are also very well suited for detecting travel paths and travel speeds for linear motions. Advantages of incremental encoders are their simple structure and, accordingly, their low price. A disadvantage is, however, that they can only detect positions when they are switched on. This requires a homing run after every switch on.
Absolute systems supply the shaft position absolutely coded over one revolution to the electronic evaluation system [single-turn encoder]. Therefore, they are safe from power failure.
Multi-turn encoders are used for absolute angle measurement over several revolutions. They usually consist of several code discs coupled by means of a precision gearbox or of a single-turn part coupled with a revolution counter.
