I/o raceway layout considerations, 2ć14, Categorize conductors – Rockwell Automation 1770 DH,DHII,DH485 CABLE User Manual

Page 30

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Planning a Data Highway or Data Highway Plus

Cable System

Chapter 2

2-14

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 2.B. Refer to the publication for each I/O module for the conductor
category classification of each I/O line.

Table 2.B

Follow these guidelines for grouping conductors

Group conductor cables fitting this description:

Into this

category:

Examples:

Control & ac Power - highĆpower conductors that are more

tolerant of electrical noise than category 2 conductors and

may also cause more noise to be picked up by adjacent

conductors.

corresponds to NEC articleĆ725 class 1

corresponds to IEEE levels 3 (low susceptibility) &

4 (power)

Category 1

ac power lines

highĆpower digital ac I/O lines - to connect ac I/O

modules rated for high power and high noise

immunity.

highĆpower digital dc I/O lines - to connect dc I/O

modules rated for high power or with input circuits

with long timeĆconstant filters for high noise rejection.

They typically connect devices such as hardĆcontact

switches, relays, and solenoids.

Signal & Communication - lowĆpower conductors that are

less tolerant of electrical noise than category 1 conductors

and should also cause less noise to be picked up by

adjacent conductors (they connect to sensors and

actuators relatively close to the I/O modules).

corresponds to NEC articleĆ725 classes 2 & 3

corresponds to IEEE levels 1 (high susceptibility) &

2 (medium susceptibility)

Category 2

analog I/O lines and dc power lines for analog

circuits

lowĆpower digital ac/dc I/O lines - to connect to I/O

modules that are rated for low power such as

lowĆpower contactĆoutput modules.

lowĆpower digital dc I/O lines - to connect dc I/O

modules that are rated for low power and have input

circuits with short timeĆconstant filters to detect short

pulses. They typically connect to devices such as

proximity switches, photoĆelectric sensors, TTL

devices, and encoders.

communication cables (remote I/O, extendedĆlocal

I/O, DH+

, DHĆ485, RSĆ232ĆC, RSĆ422, RSĆ423

cables) - to connect between processors or to I/O

adapter modules, programming terminals,

computers, or data terminals.

I/O Raceway Layout

Considerations

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