Difference between incremental and absolute encoders

The rotary incremental value encoder outputs pulses as it rotates, calculates its position by counting equipment, and relies on the internal memory of the counting equipment to remember the position when the encoder does not move or when there is a power failure. In this way, the encoder cannot have any movement when there is a power outage, and when the incoming power is working, the encoder cannot have interference and lose pulses during the output pulse process, or else the zero point calculated and memorized by the counting device will be shifted, and there is no way to know the amount of this shift, only after an erroneous result occurs.

The solution is to add reference points, and every time the encoder passes a reference point, the reference position) is corrected into the memory position of the counting device. Before the reference point, there is no guarantee of the accuracy of the position. In the industrial control there is every operation first find the reference point, power on to find zero and other methods.

Such a method is more troublesome for some industrial control projects, and even does not allow power-on zeroing, and there are some working conditions that do not allow the use of positional errors due to the influence of interference, thus the emergence of absolute encoders.

The absolute value rotary encoder optical code disk has a number of optical channel engraved lines, each engraved line in order to 2 lines, 4 lines, 8 lines, 16 lines. The coding is so arranged that at each position of the encoder, a set of binary codes from the zero power of 2 to the n-1 power of 2* is obtained by reading the pass and dark of each of the channels of the engraved lines, which is called an n-bit absolute encoder. Such an encoder is determined by the mechanical position of the code disk, it is not affected by power outages, interference, because the absolute encoder is determined by the mechanical position of each position, it does not need to memorize, no need to find a reference point, and do not have to count all the time, when you need to know the position, when it goes to read its position. In this way, the anti-interference characteristics of the encoder, the reliability of the data is greatly improved