RKI Instruments M2A - Manual (Page 57)

M2A Transmitter Operator’s Manual 52
Recommended Modbus Wiring
The recommended Modbus wiring for the M2A is illustrated in Figure 27 below. In this
configuration, 5 wires are used for wiring the M2A into a Modbus system. Figure 27 also illustrates
typical alarm device wiring. The ground jumper must be removed in this wiring configuration.
Figure 27: 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 27 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 28 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 28: Alternate Modbus Wiring
Power Supply
Remove Ground Jumper
10-30 VDC
-
+
Modbus Controller
Input
Terminals
D0
D1
Common
To
Additional
M2As
C
NC
NO
AL
AR
M
1
C
N
C
N
O
AL
A
R
M
2
C
N
C
N
O
FA
IL
See
Detect or
W iring
-
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
C
NC
NO
AL
AR
M
1
C
N
C
N
O
AL
A
R
M
2
C
N
C
N
O
FA
IL
See
Detect or
W iring
+
-
10-30 V DC
Power Supply
Input
Terminals
Modbus Controller
D1
Common
D0
C
N
C
N
O
AL
AR
M
1
C
N
C
N
O
AL
AR
M
2
C
N
C
N
O
FA
IL
-
S
+
A
B
C
RS
4
8 5
PW
R
/SI
G
R
W
G
B
LE
L
-
S
+
A
B
C
RS
4
8 5
PW
R
/SI
G
R
W
G
B
LE
L
See
Detect or
W iring
C
N
C
N
O
AL
AR
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