What are the differences between incremental encoders and absolute encoders and how to purchase them

What are the differences between incremental encoders and absolute encoders and how to purchase them?

The absolute encoder is a sensor that directly outputs numbers. There are several concentric code discs along the radial direction on its circular code disc. Each track is composed of light-transmissive and opaque sectors. The sectors of adjacent code channels The relationship between the trees in the area is doubled. The number of code channels on the code disc is the number of binary digits. On one side of the code disc is the light source, and the other side has a photosensitive element corresponding to each code channel. When the disc is in different positions When, each photosensitive element converts a corresponding level signal according to whether it receives light or not, and forms a binary number. The characteristic of this kind of encoder is that it does not need a counter, and can read a fixed digital code corresponding to the position at any position of the shaft. Obviously, there must be N doctrines. Currently there are 16-bit absolute encoder products in China.

What are the differences between incremental encoders and absolute encoders and how to purchase them?

Incremental encoders directly use the principle of photoelectric conversion to output three sets of square wave pulses A, B, and Z; the phase difference between the A and B pulses is 90. , So that the direction of rotation can be easily judged, and the Z phase is one pulse per revolution, used for reference point positioning. Its advantages are simple structure, average mechanical life of more than tens of thousands of hours, strong anti-interference ability, high reliability, and suitable for long-distance transmission. The disadvantage is that the absolute position information of the shaft rotation cannot be output.

To distinguish whether an encoder is an incremental encoder or an absolute encoder, the best way is to refer to the manufacturer’s selection manual, because the encoder involves many parameters, such as the protection level of the housing, the size of the encoder shaft, and the flange. The form and connection form, output circuit and output signal, number of pulses, etc., may sometimes not be used because of a different letter.

But to simply judge the incremental encoder or the absolute encoder, there is an experience: look at the wiring diagram on the nameplate, the incremental encoder usually has 8 wires, and the wiring symbols are: u, gnd, a, a (reverse ), b, b (reverse), z or o, z or o (reverse).

Absolute encoders usually have a large number of lines (indicated by two-color floral lines), and the wiring symbols are: u, gnd, 2^0, 2^1, 2^2, 2^3, 2^4, 2^5, 2^6,, 2^7, 2^8...

What are the differences between incremental encoders and absolute encoders and how to purchase them? The above are general encoders. There are many types of encoders. Please refer to the manufacturer's selection manual when purchasing.

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