Instruction Manual

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 - highpower 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 article725 class 1
• corresponds to IEEE levels 3 (low susceptibility) &
4 (power)
Category 1
• ac power lines
• highpower digital ac I/O lines - to connect ac I/O
modules rated for high power and high noise
immunity.
• highpower digital dc I/O lines - to connect dc I/O
modules rated for high power or with input circuits
with long timeconstant filters for high noise rejection.
They typically connect devices such as hardcontact
switches, relays, and solenoids.
Signal & Communication - lowpower 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 article725 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
• lowpower digital ac/dc I/O lines - to connect to I/O
modules that are rated for low power such as
lowpower contactoutput modules.
• lowpower digital dc I/O lines - to connect dc I/O
modules that are rated for low power and have input
circuits with short timeconstant filters to detect short
pulses. They typically connect to devices such as
proximity switches, photoelectric sensors, TTL
devices, and encoders.
• communication cables (remote I/O, extendedlocal
I/O, DH+, DH485, RS232C, RS422, RS423
cables) - to connect between processors or to I/O
adapter modules, programming terminals,
computers, or data terminals.
I/O Raceway Layout
Considerations