Instruction Manual

Planning a DH485 Cable System
Chapter 8
8-5
Table 8.A
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.
Intraenclosure - Interconnect the system components
within an enclosure
•corresponds to NEC article725 classes 2 & 3
•corresponds to IEEE levels 1 (high susceptibility) &
2 (medium susceptibility)
Category 3
•lowvoltage dc power cables - provide backplane
power to the system components
•communication cables - to connect between system
components within the same enclosure
NOTE: Remote I/O, DH, and DH+ networks must be made of catalog number 1770CD cable or a cable from the approved vendor list.
DH485 networks must be made of a cable from the approved vendor list.
Route Conductors
To guard against coupling noise from one conductor to another, follow the
general guidelines shown in Table 8.B when routing wires and cables (both
inside and outside of an enclosure). Where it is stated that cables must be in
separate raceways, they can be routed in the same ladder or trough if barriers
are used as required and defined by NEC to provide the separation specified in
Table 8.B. Use the spacing given in these general guidelines with the following
exceptions:
where connection points (for conductors of different categories) on end
devices are closer together than the specified spacing