I/O Signals; Field Wiring Considerations; Noise; Crosstalk - National Instruments NI 660 Series User Manual

I/O Signals

Field Wiring Considerations

To prevent incorrect results caused by environmental noise and crosstalk,
make sure the NI 660x and the peripheral device share a common ground
reference. Connect one or more NI 660x device D GND lines to the ground
reference of your peripheral device.
You can also use the digital filters available on each PFI line to reduce
errors that these problems might cause.

Noise

For noise immunity, take the following precautions:
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Crosstalk

Crosstalk mainly occurs when the capacitance between lines in a cable
induces a smaller transition on another line. Figure 3-10 shows an example
of crosstalk.
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When routing signals to the TIO device, keep cabling away from noise
sources.
Separate the TIO device signal lines from high-current or high-voltage
lines. High-current or high-voltage lines that run in parallel paths at a
close distance can induce currents in or voltages on the TIO device
signal lines. To reduce the coupling between lines, separate parallel
lines by a reasonable distance or run the lines at right angles to one
another.
Do not run signal lines through conduits that also contain power lines.
Protect signal lines from magnetic and electric fields caused by
monitors, electric motors, welding equipment, breakers, transformers,
or other devices by running them through special metal conduits.
Use appropriate digital filtering to remove noise.
3-17
Chapter 3 Signal Connections
NI 660x User Manual