Rotary encoder is used to measure the speed and with PWM technology can achieve fast speed device, photoelectric rotary encoder through photoelectric conversion, can output shaft angular displacement, angular velocity and other mechanical quantities into the corresponding electrical pulse digital output (REP).

Divided into two kinds of single output and double output. The main technical parameters are the number of pulses per revolution (dozens to thousands), and power supply voltage. Single-channel output refers to that the output of the rotary encoder is A set of pulses, while the two-channel output of the rotary encoder outputs two sets of pulses with A/B phase difference of 90 degrees, through which the rotation speed can be measured and the direction of rotation can be judged.