In M.D. Micro Detectors encoders the angular movement transduction is based on the photoelectric scanning principle.

On M.D. Micro Detectors encoders pulse error is ±18° e max. on full operating range, which
corresponds to a ±10% from nominal value.
Regarding the 90 electrical degrees phase relation between the two channels, it differs in ±35
electrical degrees max which corresponds to ±10% respect to signal period.