Rockwell Automation 1758-RTU202 DataSite Hardware User Manual - Manual (Page 32)

Publication 1758-UM001D-EN-P - June 2011
32 Wiring the Controller
Minimizing Electrical Noise on Analog Channels
Inputs on analog channels employ digital high-frequency filters that
significantly reduce the effects of electrical noise on input signals. However,
because of the variety of applications and environments where analog
controllers are installed and operated, it is impossible to ensure that all
environmental noise is removed by the input filters.
Several specific steps can be taken to help reduce the effects of environmental
noise on analog signals:
• install the DataSite controller system in a properly rated (i.e., NEMA)
enclosure. Make sure that the DataSite controller system is properly
grounded.
• use Belden cable #8761 for wiring the analog channels, making sure that
the drain wire and foil shield are properly earth grounded.
• route the Belden cable separately from any AC wiring. Additional noise
immunity can be obtained by routing the cables in grounded conduit.
Grounding Your Analog Cable
Use shielded communication
cable (Belden #8761). The
Belden cable has two signal wires
(black and clear), one drain wire,
and a foil shield. The drain wire
and foil shield must be grounded
at one end of the cable.
IMPORTANT
Do not ground the drain wire and foil shield at both ends of
the cable.
Foil Shield Black Wire
Drain Wire
Clear Wire
Insulation