
GDS-68XP Operation & Maintenance Manual, Revision 3.5
Page 51
If
4
‐
20mA
output
is
off
‐
scale
low
or
high
and
cannot
be
adjusted
using
DIAGNOSTICS
mode,
IO/Power
Supply
board
may
be
defective
and
should
be
replaced.
CONTROLLER
MODBUS
DATA
INCORRECT
Verify
that
MODBUS
master
is
requesting
data
from
correct
data
register
(31002).
Verify
that
controller
MIN
and
MAX
count
settings
are
correct.
MIN
counts
should
be
“800”
which
corresponds
to
4mA
and
MAX
counts
should
be
“4000”
which
corresponds
to
20
mA.
Verify
that
the
GDS
‐
68XP
MODBUS
address
matches
the
address
programmed
into
the
controller’s
channel
configuration.
CONTROLLER
SHOWING
MODBUS
COMM
ERROR
Check
for
incorrect
MODBUS
polarity
(swap
“A”
and
“B”
if
unsure;
no
damage
will
occur).
Verify
that
MODBUS
master
is
requesting
data
from
correct
MODBUS
address.
Verify
that
MODBUS
master
is
requesting
data
from
register
31002.
Verify
that
there
are
no
other
MODBUS
slave
devices
with
identical
MODBUS
address.
GDS
‐
68XP
DISPLAY
BLANK
Verify
DC
power
at
IO/Power
Supply
board,
TB2,
terminals
1
(+24)
and
4
(Gnd).
Verify
ribbon
cable
connected
between
IO/Power
Supply
board
and
Display
Assembly.