The rotary incremental encoder outputs pulses when it is rotated, and its position is known by the counting device. When the encoder is in motion or power failure, the position is recorded by the internal memory of the counting device. In this way, when the power failure, the encoder can not have any movement, when the call work, the encoder output pulse process, there can not be interference and loss of pulse, otherwise, the counting device memory zero will be offset, and this The amount of shift is no way to know, only the wrong production results can be seen before.
The solution is to increase the reference point, the encoder through the reference point, the reference position correction into the counting device memory location. Before the reference point, there is no guarantee of the accuracy of the location. To this end, there are every time in the industrial control to find a reference point, boot and other methods.
For example, the positioning of the printer scanner is to use the incremental encoder principle, each boot, we can hear the bursts of crackling, it is looking for zero, and then work.
This method is too cumbersome for some industrial projects, or even allow the boot to change the zero (after the boot will know the exact location), so there will be the emergence of absolute encoders.
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