An encoder is a sensor device used to measure the position of rotational or linear motion, and convert this position information into digital signals that can be read and recognized by a computer or controller.

Encoder is a passive sensor that does not provide any power on its own. It is driven by the external detected part through connectors such as gears or belts, and detects the relevant position information of the operation.

Encoders are often used in conjunction with motors and motion joints to form closed-loop control systems. For example, a general motor usually starts to rotate when it is powered or given an electrical signal, but the computer or controller does not know the angle of its rotation. This is an open-loop control that is not precise and reliable, but in many applications, precise and reliable control of the motor's speed and rotation angle is required. This requires the encoder and motor to be linked, reading the position information feedback from the encoder to form a precise and reliable closed-loop control