To determine which direction an
encoder is revolving, encoders output quadrature signals: two streams of
pulses, A & B, generated at 90° timing angles.
(Also called A Quad B) A leading B indicates rotation
in one direction; B leading A indicates the encoder is rotating in the
opposite direction. Example: “A leads B with clockwise rotation as viewed
from the encoder face on an M4 encoder.” Many encoders with quadrature
outputs also have complementary outputs: A NOT and B NOT signals
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