Allen-Bradley 2080-LC20-20QWB User Manual page 49

Rockwell Automation Publication 2080-UM005B-EN-E - March 2015
Minimize 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 will be
removed by the input filters.
Several specific steps can be taken to help reduce the effects of environmental
noise on analog signals:
• install the Micro800 system in a properly rated enclosure, for example,
NEMA/IP. Make sure that the shield 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.
Insulation
IMPORTANT Do not ground the drain wire and foil shield at both ends of the cable.
Wire Your Controller
Foil shield
Black wire
Clear wire
Chapter 4
Drain wire
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