Absolute encoders are so defined since they maintain the absolute position value also after an interruption or a power-loss, so it’s essential that all data referring to the position should be always available. For this purpose binary codes are employed, set by the pattern of transparent and opaque segments placed crosswise or lengthwise on the disc, in relation to the direction of the movement.

Binary code

The natural binary code presents the disadvantage to have more binary digits changing between two consecutive positions. Because of mechanical tolerances, bounces or noise, it could happen that the commutation signals do not operate all at the same time when the state changes, causing intermediate situations that could produce errors in the calculation of the position. To avoid this inconvenient and, therefore, to avoid errors in the output code, an output sync signal (STROBE) is used.

Gray code

In Gray code a single binary digit changes between consecutive steps; the code tracks are read crosswise, with respect to the direction of movement, avoiding encoding errors caused by bits changing in contiguous positions.