Quadrature measurements
The Quadrature() instruction is used to measure shaft or rotary encoders. A shaft encoder outputs a signal to represent the angular position or motion of the shaft. Each encoder will have two output signals, an A line and a B line. As the shaft rotates the A and B lines will generate digital pulses that can be read, or counted, by the data logger.
In the following example, channel A leads channel B, therefore the encoder is determined to be moving in a clockwise direction. If channel B led channel A, it would be determined that the encoder was moving in a counterclockwise direction.
Terminals Quadrature() instruction can return:
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The accumulated number of counts from channel A and channel B. Count will increase if channel A leads channel B. Count will decrease if channel B leads channel A.
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The net direction.
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Number of counts in the A-leading-B direction.
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Number of counts in the B-leading-A direction.
Counting modes:
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Counting the increase on rising edge of channel A when channel A leads channel B. Counting the decrease on falling edge of channel A when channel B leads channel A.
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Counting the increase at each rising and falling edge of channel A when channel A leads channel B. Counting the decrease at each rising and falling edge of channel A when channel A leads channel B.
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Counting the increase at each rising and falling edge of both channels when channel A leads channel B. Counting the decrease at each rising and falling edge of both channels when channel B leads channel A.
For more information, see Digital input/output specifications.