3Rs-485 Bus; 4Installation Cases - Emerson Rosemount 5400 Series Reference Manual

Reference Manual
00809-0100-4026, Rev HA
4.10.3 RS-485 bus
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4.10.4 Installation cases
Install the Rosemount 5400 Series Transmitter as shown in
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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 4-17. Multidrop Connection of Rosemount 5400 Series Transmitters
120 W
Electrical Installation
The Rosemount 5400 transmitter does not provide electrical isolation between the
RS-485 bus and the transmitter power supply
Maintain a bus topology and minimize stub length
Figure 4-17 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
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)
RS-485 bus
HART to Modbus Converter
MB
MA
MODBUS
(RS-485)
POWER
HART Ambients > 60 ºC
Use wiring rated
for min 90 ºC
Internal
ground screw
External
ground screw
Figure
HART to Modbus Converter
MB
MA
MODBUS
(RS-485)
POWER
HART Ambients > 60 ºC
Use wiring rated
for min 90 ºC
Internal
ground screw
External
ground screw
Section 4: Electrical Installation
November 2014
4-17.
120 W
B
A
Modbus
master
Z
Power
supply
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