Rockwell Automation 1761-HHP-B30 MicroLogix 1000 with Hand-Held Programmer (HHP) - Manual (Page 50)

Chapter 2
Wiring Your Controller
2–20
Inputs on analog 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
t 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 other wiring. Additional noise
immunity can be obtained by routing the cables in grounded conduit.
A system may malfunction due to a change in the operating environment
after a period of time. We recommend periodically checking system
operation, particularly when new machinery or other noise sources are
installed near the MicroLogix 1000 system.
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
earth ground the drain wire and foil shield at both ends of the cable.
Foil Shield
Black Wire
Drain Wire
Clear Wire
Insulation
Minimizing Electrical Noise on
Analog Controllers
Grounding Your Analog Cable