1 principle of photoelectric encoder
The photoelectric encoder is a sensor which converts the mechanical geometric displacement of the output shaft into a pulse or a digital quantity by photoelectric conversion. This is the most widely used sensor, photoelectric encoder is composed of grating disc and photoelectric detection device. Grating disc is divided and opened a plurality of rectangular holes in certain diameter circular plate. Due to the photoelectric encoder is coaxial with the motor, motor rotation, grating disc and a motor rotate at the same speed, composed of the light emitting diodes and other electronic components detection device detection output a certain number of pulse signal, as shown in Figure 1 Schematic diagram of the principle, through calculations per second photoelectric encoder output pulse number can reflect the current of the motor speed. In addition, to determine the direction of rotation, the encoder can also provide a phase difference of 90 Mu Chen Xiao lotus imitation dry hinge screw
According to the detection principle, the encoder can be divided into optical, magnetic, inductive and capacitive. According to its calibration method and the signal output form, it can be divided into three kinds of incremental, absolute and mixed type.
1.1 incremental encoder
Incremental encoder is directly using the principle of photoelectric conversion output three groups of square wave pulse a, B and Z phase; a, B two groups of pulse phase difference 90 sea Commission evil spirit award stunned to discharge milling bream is Ying magnificus phase for each turn a pulse, used to benchmark positioning. Its advantages are simple structure, the average life span of the machine can be in the tens of thousands of hours, strong anti-interference ability, high reliability, suitable for long distance transmission. The disadvantage is that the absolute position information of the output shaft can not be rotated.
1.2 absolute encoder
Absolute encoder is directly output digital quantity sensor, in the round disc along the radial direction with several concentric code, each composed by the transparent and opaque, a sector of the interphase and adjacent code a number of sectors is double, encoder code number is the second digit of the digital business, at the encoder side light, the other side corresponding to each code has a photosensitive element; when the disc is in a different position, the photosensitive element under the light and not convert a voltage signal corresponding to form a binary number. The encoder is characterized in that a fixed position corresponding to a digital code can be read at any position of the rotating shaft. Obviously, code number, the higher the resolution, for an encoder with N binary resolution and its code must have n barcode way. At present, there are 16 absolute encoder products in china.
