Motor shaft encoder is one type of rotation sensor. Currently, it is the most often used sensor. The motor shaft encoder includes optical disc and photoelectric detecting parts. The optical disc and motor shaft rotate at the same speed. The led electrical parts detect it and output pulse signals at the same time.

An incremental rotary encoder working principle is provides cyclical outputs (only) when the encoder is rotated. The incremental rotary encoder is the most widely used of all rotary encoders due to its low cost and ability to provide signals that can be easily interpreted to provide motion related information such as position and velocity.