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65-2661RK-03-04 M2A Transmitter Operator’s Manual
Recommended Modbus Wiring
The recommended Modbus wiring for the M2A is illustrated in Figure 9 below. In this
configuration, 5 wires are used for wiring the M2A into a Modbus system. Figure 9 also
illustrates typical alarm device wiring.
The ground jumper must be removed in this wiring
configuration.
Figure 9: Recommended Modbus Wiring
Adding an M2A to an Existing M2 Modbus Installation with Recommended Wiring
An M2A 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 must still be removed.
Alternate Modbus Wiring For Existing Installations
Although the wiring shown in Figure 9 is recommended, it is possible to wire the M2A
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 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
+
-
10-30 VDC
Remove Ground Jumper
Power Supply
Common
D1
D0
Input
Terminals
Modbus Controller
Remove
Ground
Jumper
C
NC
N
O
AL
AR
M
1
C
NC
N
O
AL
AR
M
2
C
N
C
N
O
FA
IL
-
S
+
A
B
C
R
S
485
PW
R
/S
IG
R
W
G
B
LE
L
-
S
+
A
B
C
R
S
485
PW
R
/S
IG
R
W
G
B
LE
L
See
Detector
Wiring
C
NC
N
O
AL
AR
M
1
C
NC
N
O
AL
AR
M
2
C
N
C
N
O
FA
IL
To
Additional
M2As
See
Detector
Wiring
+
-
10-30 V DC
Power Supply
Input
Terminals
Modbus Controller
D1
Common
D0
C
N
C
N
O
AL
A
R
M
1
C
N
C
N
O
AL
AR
M
2
C
N
C
N
O
FA
IL
-
S
+
A
B
C
R
S
485
PW
R
/S
IG
R
W
G
B
LE
L
-
S
+
A
B
C
R
S
485
PW
R
/S
IG
R
W
G
B
LE
L
See
D etect or
W iring
C
N
C
N
O
AL
A
R
M
1
C
N
C
N
O
AL
AR
M
2
C
N
C
N
O
FA
IL
To
Additional
M2As
See
Detect or
W iring
