Index (Ch. I)

The Index is a unique location on an encoder disk or linear strip used as a reference point. The index output is provided via a third channel on quadrature encoders and is often referred to as the “I” channel (index) or the “Z” channel (zero position). The index enables position to be determined after a homing cycle. US Digital index outputs are internally gated to coincide with the low states of channels A and B. This provides a precise index position that is ¼ of one quadrature cycle wide. The use of a single index is most common, but some applications use multiple indices with distinctive spacing requiring less movement to determine the exact position. US Digital specializes in creating custom disks to match applications.