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Chapter 8: RS-485 Modbus Output
65-2660XL-XX-04 M2A-XL Transmitter
Alternate Modbus Wiring For Existing Installations
Although the wiring shown in Figure 9 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 10 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.
Figure 10: Alternate Modbus Wiring
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.
Power Supply
10-30 VDC
-
+
To
Additional
M2As
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
-
S
+
A
B
C
RS
4
8
5
PW
R
/S
IG
R
W
G
B
LE
L
-
S
+
A
B
C
RS
4
8
5
PW
R
/S
IG
R
W
G
B
LE
L
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
D1
Modbus Controller
Input
Terminals
D0
Common
See
Detector
Wiring
