Rockwell Automation Allen-Bradley MicroLogix 1000 Instructions D'installation page 17

Minimizing Electrical Noise on Analog Controllers
Inputs on analog controllers 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 MicroLogix 1000 system in a properly rated (i.e., NEMA)
enclosure. Make sure that the MicroLogix 1000 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 separate 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. Do not ground the drain
wire and foil shield at both ends of the cable.
Insulation
Clear Wire
Installation Instructions
MicroLogix 1000 Programmable
Controllers
Foil Shield
Black Wire
Drain Wire
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