User Manual Appendix C
GFK-1742F Jan 2020
Position Feedback Devices 417
C-3.4 Incremental Quadrature Encoder
Incremental Quadrature Encoders provide three output signals to the DSM314: Channel A,
Channel B, and Marker. The Channel A and Channel B signals transition as the encoder turns,
allowing the DSM314 to count the number of signal transitions and calculate the latest
encoder position change and direction of rotation.
Incremental Quadrature Encoders are incremental feedback devices; they do not provide a
continuous indication of absolute shaft angle as the input shaft rotates. For this reason, the
DSM314’s Actual Position %AI status word must be initialized with a known physical position
before positioning control is allowed. This position alignment can be accomplished using
the Set Position %AQ Immediate command or the %Q Find Home cycle. The home cycle
makes use of the encoder marker channel, which is a once per revolution pulse produced at
a known encoder shaft angle. Successful completion of the %Q Find Home cycle or a Set
Position %AQ command causes the DSM314 to set the axis Position Valid %I bit. Position
Valid must be set before motion programs will be allowed to execute. Position Valid is only
cleared by an encoder Quadrature Error (Channel A and Channel B switching at the same
time) or by turning on the Find Home and Abort %Q bits simultaneously.
Note: In Digital Mode, only incremental quadrature encoders are supported for the Follower mode
master axis.
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