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Energy
8. Connect a ground
reference line to
the
te1minal
labeled
SHLD
The
shield
of
a
communications
cable
may
be used
for this reference as
long as
the
shield is connected
to
ea1th
ground
at one point only. AE
recommends
that
all AE inve1ters have
connected grounds when
possible.
~
Important
Some Modbus
devices do not have
a
shield
or reference
input. In
these
cases
the device most
often uses
the
DC
power
supply (-)
as the RS-485
reference.
It
may
be
necessa1y to place an
RS-485
isolator
on
these
devices
or
power them
from
a
common
DC
supply
that
has its DC (-)
referenced
to eaith
ground
at
the
same
point
where
the network
cable
shield
is
eaithed.
Setting the Jumper Pins
6-12
By
default,
the te1mination pins have three
slave
jumpers
installed
in the disabled
positions when
the
inve1ter
is
shipped.
The location
of
the jumpers
can
dete1mine
the
following
settings
for an
inve1ter:
•
Te1minate the network
•
Dete1mine the center inve1ter(s)
on
the network
•
Tum
on
biasing
Termination jumpers
(shown
in
"disabled"
position)
Address switch
Modbus slave port
terminal blocks
Figure 6-10.
Termination
jumpers
on the communications interface
PCB
The pe1fo1mance of
your
Modbus
network
may
require
each
end
of
the
network
to be
te1minated using 120
Q
te1mination
resistors.
When the network
is long
relative
to
the
RS-485
bit
rate
in
use,
bus
te1minations
must be
installed.
The network
length
is
dete1mined
by the total backbone
cable
length
rather than the
line-of-sight
between
the
two
ftuthest
apait devices.
Data
Monitoring and Controls
570-1001793-0SB
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Troubleshooting
