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Chapter 8: RS-485 Modbus Output
65-2646XL-05-04 M2A Transmitter Operator’s Manual
Ground Jumper
The M2A includes a 2-pin ground header (see Figure 4 on page 12) that is used when the M2A is
used in a Modbus system. Every M2A is supplied with a ground jumper (a jumper block) installed
onto this header. If the M2A isn’t wired into a Modbus system or if it is wired into one as shown
in Figure 12, the ground jumper should be installed. If the M2A is wired in a Modbus system as
shown in Figure 11, the ground jumper should be removed.
Recommended Modbus Wiring
The recommended Modbus wiring for the M2A is illustrated in Figure 11 below. In this
configuration, 5 wires are used for wiring the M2A into a Modbus system. Figure 11 also
illustrates typical alarm device wiring. The ground jumper must be removed in this wiring
configuration.
Figure 11: 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.
-
S
+
+
PW
R
/S
IG
PW
R
/S
IG
+
-
S
+
RS
4
8
5
A
B
C
A
B
C
RS
4
8
5
+
-
10-30 VDC
Input
Terminals
Modbus Controller
Remove Ground Jumper
Power Supply
Common
D1
D0
+
C
N
C
N
O
AL
A
R
M
1
C
NC
N
O
AL
A
R
M
2
C
N
C
NO
FA
IL
See
Detector
Wiring
C
N
C
N
O
AL
A
R
M
1
C
NC
N
O
AL
A
R
M
2
C
N
C
NO
FA
IL
To
Additional
M2As
Remove
Ground
Jumper
TO
X
IC
O
X
Y
+
TO
X
IC
O
X
Y
See
Detector
Wiring
