Emerson Rosemount 5402 - Bus; Installation Cases

91
Reference Manual
00809-0100-4026, Rev KC
Electrical Installation
October 2018
Electrical Installation
4.11.3 RS-485 bus
 The Rosemount 5400 does not provide electrical isolation between the RS-485 bus and the
transmitter power supply.
 Maintain a bus topology and minimize stub length.
 Figure 4-15 identifies multidrop wiring topology, where up to 32 devices may be wired on one RS-485
bus.
 The RS-485 bus needs to be terminated once at each end, but should not be terminated elsewhere on
the bus.
4.11.4 Installation cases
Install the Rosemount 5400 as shown in Figure 4-15.
 Use common ground for Modbus master and power supply.
 The power cables and RS-485 Bus are in the same cable installation.
 A ground cable is installed and shall be used (cable size > 4 mm according to IEC60079-14, or size
according to applicable national regulations and standards). A properly installed threaded conduit
connection may provide sufficient ground.
 The cable shielding is grounded at master site (optional).
Note
The HMC equipped transmitter contains intrinsically safe circuits that require the housing to be
grounded in accordance with national and local electrical codes. Failure to do so may impair the
protection provided by the equipment.
Figure 4-15. Multidrop Connection of Rosemount 5400
MODBUS
POWER
HART
(RS-485)
HART to Modbus Converter
MB
MA
-
-
+
+
MODBUS
POWER
HART
(RS-485)
HART to Modbus Converter
MB
MA
-
-
+
+
Ambients > 60 ºC
Use wiring rated
for min 90 ºC
Ambients > 60 ºC
Use wiring rated
for min 90 ºC
Power
supply
120 
120 
RS-485 bus
B
A
Modbus
master
Z
External
ground screw
Internal
ground screw
External
ground screw
Internal
ground screw