Publication 1763-UM001E-EN-P - June 2015
Connecting to Networks via RS-232/RS-485 Interface 207
• type of process being controlled.
• network configuration.
The major hardware and software issues you need to resolve before installing a
network are discussed in the following sections.
Hardware Considerations
You need to decide the length of the communication cable, where you route it,
and how to protect it from the environment where it will be installed.
When the communication cable is installed, you need to know how many
devices are to be connected during installation and how many devices will be
added in the future. The following sections help you understand and plan the
network.
Number of Devices and Length of Communication Cable
The maximum length of the communication cable is 1219 m (4000 ft). This is
the total cable distance from the first node to the last node in a segment.
However, two segments can be used to extend the DH-485 network to 2438 m
(8000 ft.). For additional information on connections using the AIC+, refer to
the Advanced Interface Converter (AIC+) User Manual, publication 1761-6.4.
Planning Cable Routes
Follow these guidelines to help protect the communication cable from
electrical interference:
• Keep the communication cable at least 1.52 m (5 ft.) from any electric
motors, transformers, rectifiers, generators, arc welders, induction
furnaces, or sources of microwave radiation.
• If you must run the cable across power feed lines, run the cable at right
angles to the lines.
• If you do not run the cable through a contiguous metallic wireway or
conduit, keep the communication cable at least 0.15 m (6 in.) from AC
power lines of less than 20 A, 0.30 m (1 ft.) from lines greater than 20 A,
but only up to 100K VA, and 0.60 m (2 ft.) from lines of 100 K VA or
more.
• If you run the cable through a contiguous metallic wireway or conduit,
keep the communication cable at least 0.08 m (3 in.) from AC power
lines of less than 20 A, 0.15 m (6 in.) from lines greater than 20 A, but
only up to 100 K VA, and 0.30 m (1 ft.) from lines of 100 K VA or more.
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