Emerson 1420 - Rs-485

20
Reference Manual
00809-0200-4420, Rev HC
Section 3: Installation
July 2015
Installation
Figure 3-6. Terminal Block Diagram
Figure 3-7. PoE Compatible Gateway Terminal Block
Ethernet connections should use Cat5E or better shielded cable to connect to an Ethernet hub,
switch, or router. The maximum cable length should not exceed 328 ft. (100 m).
Note
Unless dual Ethernet ports were specified at the time of order, the secondary Ethernet port
(Ethernet 2) will not be active.
3.4.3 RS-485
The Gateway may be ordered with an optional RS-485 (serial) connection (Figure 3-6). It is
referenced by the A and B Serial Modbus terminals. This connection is used to communicate
Modbus RTU on an RS-485 data bus.
Use 18 AWG single twisted shielded pair wiring to connect the Gateway to the RS-485 data bus.
The total bus length should not exceed 4000 ft. (1220 m). Connect the Tx + (positive, transmit)
wire to terminal A and the Rx - (negative, receive) wire to terminal B. The wiring shield should be
trimmed close and insulated from touching the Gateway enclosure or other terminations. Only
terminated at one end typically at the power supply end.
+
+
+
+
+
-
-
-
-
-
AB
S
S
S
S
24 VDC
(nominal)
Power Input
Serial
Modbus
N
ot Used
Not Use
d
N
ot Use
d
Not Use
d
Case
(Covered)
S
Ethernet 2
with Power
Ethernet 2
Ethernet 1
(Secondary) (Primary)
+
-AB
24 VDC
(nominal)
Power Input
Serial
Modbus
Case
S
Ethernet 2
Ethernet 1
(Secondary) (Primary)