Absolute pulse encoder: APC incremental pulse encoder: SPC both are generally used in speed control or position control system detection components. Rotary encoder is used to measure the speed of the device. It can be divided into single output and double output. The main technical parameters are the number of pulses per revolution (dozens to thousands), and power supply voltage. The single output means that the output of rotary encoder is a group of pulses, while the two-way output rotary encoder outputs two groups of pulses with phase difference of 90 degrees. Through these two groups of pulses, not only the rotational speed can be measured, but also the direction of rotation can be judged. The difference between incremental encoder and absolute encoder. If the encoder is divided by signal principle, there are incremental encoder and absolute encoder. The working principle of incremental encoder (rotary type): it consists of a photoelectric encoder with an axis in the center, on which there are ring-shaped through and dark lines, which are read by photoelectric transmitting and receiving devices. Four groups of sine wave signals are combined into a, B, C and D.