From the incremental value encoder to the absolute encoder
   Rotary incremental encoder output pulse is rotated by counting device to calculate its position, when the encoder does not move or power outage, rely on the internal memory to remember the location of a counting device. Thus, when the power failure, the encoder can not have any movement, when the call comes to work, the encoder output pulse process, it can not have interference and loss of pulse, or count device will calculate and zero offset memory, and this Species shift amount is impossible to know in order to know the results only after the production error appears.
The solution is to increase the reference point, the encoder after every reference point, the position of the reference position correction into the memory device count. In the reference point before, there is no guarantee the accuracy of the location of. To this end, every operation in the industrial in there to go first reference point, turn the change and other methods.
Such an approach is too much trouble for some industrial projects, not even allowed to turn the change (after the boot must know the exact location), so there is an absolute encoder appears.
Many dynasty channel groove absolute encoder optical encoder, each engraved lines sequentially 2 lines, 4 lines, 8 lines, 16 lines. . . . . . Choreography, so that in each position encoder by reading through every line carved, dark, get a unique set of binary encoding n-1 from the 2 to the power of the zero-th to 2 (Gray Code), which is called n-bit absolute encoder. Such mechanical position of the encoder is a photoelectric encoder of the decision, it is not a power outage, the impact of interference.
Each position of absolute encoder position determined by the machine is unique, it does not need memory, no need to find a reference point, and do not have counted, when the need to know where and when to go to read its position. Thus, anti-jamming features encoder, greatly improving the reliability of the data.