Encoder Principle！

Encoder Principle

Photoelectric encoder, a photoelectric conversion by a mechanical displacement of the output shaft of the geometry into a pulse or digital sensors. This is currently the most widely used sensors, optical encoder is a grating disk and the photo detector device component. Grating disk is partially a certain diameter circular plate, etc. opening of a number of rectangular holes. Since the photoelectric encoder coaxial with the motor, the motor is rotated, with the grating disk and the motor rotation speed, number of pulse signals output by the detection means detecting light-emitting diodes and other electronic components, the schematic diagram shown in Figure 1; calculated per second the number of photoelectric encoder output pulse can reflect the current motor speed.

1.1 Incremental encoder
Incremental encoder is the direct use of the photoelectric conversion principle square wave pulse output three groups A, B and Z phase; A, B two pulse phase 90 helpers evil sea Prize startled Gu Ying Qian unloading milling bream compared with a per revolution pulse for homing. The advantage is that the principle of simple structure, mechanical average life of more than tens of thousands of hours, anti-interference ability, high reliability, suitable for long distance transmission. The disadvantage is that the absolute position information can not be output shaft rotation.

1.2 Absolute encoders
Absolute encoder is a direct digital output sensor in its circular code wheel has a plurality of radially concentric code channels, each track by the translucent and opaque sector composed of white, fan-adjacent code channel the number of zones is a double relationship, number of tracks on the disc code code is its digital binary digits on one side of the disc is the source code, on the other side corresponding to each code channel having a photosensitive member; when the code disk in a different position when, in accordance with each of the photosensitive member by light or not to convert the corresponding level signal, the formation of a binary number. This is not characteristic of the encoder counter at any position on the reels can be read with a fixed position corresponding to the digital code. Obviously, the more code channel, the higher the resolution, for having an N-bit resolution encoder, the encoder must have a bar code N channel. Currently there are 16 absolute encoder products.

Absolute encoders is the use of natural binary or binary cycle (Gray code) for photoelectric conversion mode. The difference absolute encoder and incremental encoder that the disc translucent, opaque line graphics, the absolute encoder can have several codes, according to the coding read code on the disc, to detect the absolute position. The design can be encoded binary code, cyclic code, twos complement, and the like. It is characterized by:
1.2.1 can be directly read out the absolute angular coordinates;
1.2.2 no cumulative error;
1.2.3 location information is not lost after power cut. But the resolution is determined by the binary digits, that accuracy depends on the number of bits, there are 10, 14, and other.

1.3 Hybrid absolute encoder
Hybrid absolute encoder, which outputs two sets of information: a set of information for detecting the magnetic pole position with absolute information function; the other group is completely output with incremental encoders.

Photoelectric encoder is an angle (angular velocity) detection means which amount to enter the angle of the shaft, the use of photoelectric conversion principle into a corresponding electrical pulse or digital, small size, high precision, reliable, digital interfaces, etc. . It is widely used in CNC machine tools, turret, servo drives, robotics, radar, and other military targets required detection angle measuring devices and equipment.

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