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Chapter 2 Power and I/O
© National Instruments Corporation 2-7 NI 17xx Smart Camera User Manual
Connecting to a Quadrature Encoder
This section applies only to the following NI Smart Cameras:
Connect RS-422 compatible differential quadrature encoders to the
NI 17xx Smart Camera to provide positional information. A quadrature
encoder uses two output channels, Phase A and Phase B, to track the
position of a rotary shaft. Generally, the shaft is coupled to a motor drive
that controls the movement of an object. By providing Phase A and Phase B
signals to the smart camera, you can obtain a precise measurement of the
object position. Using a quadrature encoder gives you the ability to specify
your trigger delay in terms of positional units—such as inches or
centimeters, after applying the resolution information of your
encoder—rather than time.
National Instruments does not recommend the use of single-ended
encoders with the smart camera. This configuration would require the
ground for a single-ended encoder to be connected to the COM pin of the
smart camera, and the PhaseA– and PhaseB– signals would be left
unconnected. In this configuration, the system is susceptible to significant
noise that would be eliminated by using a differential encoder.
Shielded encoder cables are recommended for all applications. Unshielded
cables are more susceptible to noise and can corrupt the encoder signals.
Refer to the External Trigger section of Chapter 5, Image Acquisition,
for information about using a quadrature encoder to delay a trigger.
• NI 1742 • NI 1762
• NI 1744 • NI 1764