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ECT MODBUS The RS485 Network and Hardware Setup • 6-15
CAUTION: If you change any dip switch
settings while the board is powered, disconnect
the power and re-power the board to reset.
WIRING FOR 640-0056, 56VA Transformer,
and 640-0080, 80VA Transformer
24VAC Center-Tapped Transformer
PRIMARY SIDE
240 208
C
120
(
N
E
U
T
R
A
L
)
(
H
O
T
)
120/208/240 VAC
L2
L1
Three-conductor non-shielded cables
are the recommended wire
for connecting between the
center-tapped transformer
and I/O boards.
Power Wiring Types:
14 AWG Belden 9495
18 AWG Belden 9493
SECONDARY SIDE
24V CT 24V
AC1
0V
AC2
AC1
AC2
0V
SHIELDED TWISTED PAIR
BELDEN #8761. FOR PLENUM,
USE BELDEN #82761 OR #88761
OR EQUIV.
WIRE + to + (same color)
WIRE 0V to 0V
WIRE - to - (same color)
BAUD RATE
1. Connect the 4AO board to the RS485 I/O Network.
2. Set the network address on the first five
rockers of dip switch S1.
3. Set the network baud rate using rockers 6
and 7 of dip switch S1.
4. Set RS485 termination jumpers UP (terminated) if at
either end of a daisy chain. Otherwise, set
jumpers DOWN (not terminated).
5. Optionally, connect the 4-20mA outputs in either a 2-wire
or 4-wire hookup as illustrated in Step 5, or if a 4-20mA is
not used, it may be left unconnected.
6. Connect board to the 24VAC secondary
of the power transformer.
center-tapped
(Terminated)
(Not Terminated)
(Term)
(Term)
J9 J10 J11
J9 J10 J11
I
/
O
N
E
T
Note:
Either the “2-wire” or “4-wire”
Hookup may be used at either
4-20mA output. The Hookups may
be the same or different. If a 4-20mA
is not used, it may be left unconnected.
“2-wire” 4-20mA
(Externally Powered)
Hookup example.
(Isolated)
+12V
+4-20
4-20 OUT
0V
+
+
_
_
24V
1-5V
Not Used
Not Used
4-20mA
Analog
Output
4-20mA
Analog
Output
“4-wire” 4-20mA
(Internally Powered)
Hookup example.
(Not Isolated)
+12V
+4-20
4-20 OUT
0V
_
+
250 ohms
Jumper
Grounded
1-5V
6
6
250 ohms
+
V
OUT
15-K
15-K
+
-
-
V
IN
NOTE: The voltage divide function capability
on the previous model (P/N 810-3030) 4AO board is
no longer supported. This can now be accomplished
by using two external 15-K resistors. If used with E2,
scale output range.