Omron NV3Q Series, Connection Manual

Page: 134 / 145

110
Modbus Slave (RTU Mode)
Section 11-1
Note If there is a lot of noise in the environment, implement noise countermea-
sures, such as using shielded cables and attaching ferrite cores. Make sure
that the shield is not exposed, which would make it vulnerable to static elec-
tricity.
The number of nodes, transmission distance, and baud rate will depend on
the devices on the network. Confirm operation using the actual devices.
The maximum transmission distance for 24-V RS-232C for NV-series PTs is 15 m.
The maximum transmission distance for 5-V RS-232C for NV3W PTs is 30 m.
The maximum transmission distance for 24-V RS-422A for NV-series PTs is 500 m.
Connection for RS-485 may not be possible depending of the switchover tim-
ing between sending and receiving at the remote device. Confirm operation
using the actual devices.
Connection diagram PT
NV3W, NV4W, or
NV3Q for RS-485
No.1
No.2
No.N
1
2
3
4
5
6
7
8
Pin No.
+
−
NC (or FG)
+SD
−
SD
+RD
−
RD
E
Signal
PT (Modbus-RTU Slave)
To power
supply
1
2
3
4
5
6
7
8
Pin No.
+
−
NC (or FG)
+SD
−
SD
+RD
−
RD
E
Signal
PT (Modbus-RTU Slave)
To power
supply
1
2
3
4
5
6
7
8
Pin No.
+
−
NC (or FG)
+SD
−
SD
+RD
−
RD
E
Signal
PT (Modbus-RTU Slave)
To power
supply
Signal
+
−
PLC
(Modbus-RTU Master)
Terminating resistance
120
Ω
Connect.
Connect the E terminal and -RD terminal at the end node only.
Wire each node to the next node.
Do not branch the wire from one node to more than one other node.
Correct Wiring
Incorrect Wiring
RS-485
1:N Connections