Principle of Photoelectric Encoder

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Photoelectric encoder is a sensor that converts the mechanical geometric displacement on the output shaft into pulses or digital quantities through photoelectric conversion. It is the most widely used sensor at present. The general photoelectric encoder is mainly composed of a grating disk and a photoelectric detection device. In the servo system, since the photoelectric code disk is coaxial with the motor, when the motor rotates, the grating disk rotates at the same speed as the motor. The detection device composed of electronic components such as light-emitting diodes detects and outputs a number of pulse signals, and its principle is shown in the figure. By calculating the number of pulses output by the photoelectric encoder per second, the current motor speed can be reflected. In addition, in order to determine the direction of rotation, the code disk can also provide two channels of optical code output with a phase difference of 90°, and determine the direction of the motor according to the state change of the dual-channel optical code. According to the detection principle, encoders can be divided into optical, magnetic, inductive and capacitive types. According to its scale method and signal output form, it can be divided into three types: incremental, absolute and hybrid.