Rockwell Automation 1770 DH,DHII,DH485 CABLE - Manual (Page 105)

Planning a DHĆ485 Cable System
Chapter 8
8-4
ATTENTION: When determining cable lengths, do not allow
tension to be exerted on the cable. Tension on the cable can damage
the cable and connectors. To minimize tension, allow sufficient slack
in the cable.
You must install a link coupler for each non-isolated node on the
DH-485 network.
If you plan to add non-isolated nodes at a later date, provide additional link
couplers when you install the initial cable system. This will help avoid the
disruption of recabling after the network is in operation.
The I/O raceway layout of a system is reflective of where the different types of
I/O modules are placed in an I/O chassis. Therefore, you should determine I/O
module placement prior to any layout and routing of wires. However, when
planning your I/O module placement, segregate the modules based upon the
conductor categories published for each I/O module so that you can follow these
guidelines. These guidelines coincide with the guidelines for “the installation of
electrical equipment to minimize electrical noise inputs to controllers from
external sources” in IEEE standard 518-1982.
Categorize Conductors
Segregate all wires and cables into the three categories shown in
Table 8.A. Refer to the publication for each I/O module for the conductor
category classification of each I/O line.
Selecting the Number of
Link Couplers
I/O Raceway Layout
Considerations