ENCODER

摘要

In order to detect faults as accurately as possible without an increase in the number of position detection signals, an encoder is provided with: a plurality of position detection signal generation systems (light source (1), tracks (3a-3c), photoelement units (4a-4c)) for generating electrical signals as position detection signals having different periods; a first electrical-angle calculation unit (8) and a first preparation unit (9) for single rotation position data which function as a first computation unit for calculating first position data on the basis of the position detection signals generated by the plurality of position detection signal generation systems; a second electrical-angle calculation unit (11) and a second preparation unit (12) for single rotation position data which function as a second computation unit for calculating second position data on the basis of electrical signals generated by a fewer number of position detection signal generation systems than that for the first computation unit; and a comparison unit (10) as a fault determination unit for determining, on the basis of the first position data and the second position data, whether the local encoder is faulty.