Absolute rotary type encoder is widely applied to angle, length and motion control in industrial system because of the sole position. The sole location function of absolute rotary type encoder is obviously better than incremental encoder. It is with high resolution and high accuracy. So absolute type encoder is more and more used in industrial control. In mechanical, absolute rotary encoder is similar to incremental type encoder. There are also solid shaft absolute encoder and hollow shaft absolute encoder, which meets different mounting requirement.