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Chapter 8: RS-485 Modbus Output
65-2670XL-XX-07 M2A-XL Transmitter
Alternate Modbus Wiring For Existing Installations
Although the wiring shown in Figure 11 is recommended, it is possible to wire the M2A-XL into
a Modbus system with only 4 wires in situations where a pre-existing system is being replaced
and wiring is already in place. This should only be done if wiring for a system that is being
replaced is already installed and it is not practical to run another wire. See Figure 12 below for
this wiring configuration. In this configuration, the wire between the “C” terminal on the M2A-
XL and the Common terminal on the Modbus controller is omitted. Instead, the Common terminal
on the Modbus controller is connected to the “-” of the 24 VDC power supply.
The ground jumper
must be installed in this wiring configuration.
Adding an M2A-XL to an Existing M2 Modbus Installation with
Alternate Wiring
An M2A-XL can be wired into an existing M2 Modbus system. The shape of the terminal PCB
will be different but the wiring connections are identical and the ground jumper on the M2A-XL
must still remain installed.
+
-
S
+
PW
R
/S
IG
+
-
S
+
PW
R
/S
IG
A
B
C
RS
4
8
5
A
B
C
RS
4
8
5
+
-
10-30 VDC
Power Supply
Modbus Controller
D1
Common
D0
Input
Terminals
TO
X
IC
O
X
Y
C
N
C
NO
AL
A
R
M
1
C
NC
N
O
AL
A
R
M
2
C
N
C
N
O
FA
IL
See
Detector
Wiring
C
N
C
NO
AL
A
R
M
1
C
NC
N
O
AL
A
R
M
2
C
N
C
N
O
FA
IL
To
Additional
M2As
+
TO
X
IC
O
X
Y
+
See
Detector
Wiring
Figure 12: Alternate Modbus Wiring
