Why is it called "absolute encoder"?

"Absolute encoder" relative to the "incremental encoder type".

"Absolute encoder" said and remember to use some way absolute position of the object, Angle and the number of turns. Once the position, Angle and the number of turns is fixed, when the encoder is the only fixed value, including power cuts after electricity. "Incremental encoder type" can't do it. General type "incremental encoder" output two pulse signal A, B, A Z (L) and zero signal, A and B pulse differential phase Angle of 90 degrees to each other. By pulse counting can know the position, Angle and the number of turns increment, through A, B or pulse signal lead lag can know the direction, after the blackout, must from the appointed benchmark start counting again. "Incremental encoder type" position, Angle and the number of turns needed to do the post-processing, return of electricity to do "zero", so "incremental encoder type" than the "absolute encoder" much cheaper in price.