Abstract: A displacement measuring method that measures phase changes between a reference and a phase-shifted signal from -.infin. to .infin. degrees (limited by the size of counters) in precise incremental steps using a method referred to as Digital Phase Signature Comparison. Digital Phase Signature Comparison uses an n-bit digital pulse train synchronized to a reference signal to sample a binary phase-shifted signal of a known duty cycle. This n-bit sampling creates a unique phase signature which is stored in a memory device. One digital n-bit phase signature is created for each synchronized pulse train. Each stored phase signature is compared with the previous phase signature to determine whether the phase of the phase-shifted signal has changed, the magnitude of that change, and the direction of displacement. Error detection can protect against unknown phase signatures and phase signature transitions, thus ehminating accumulated or incident inaccuracies.