Emerson Rosemount 3490 Series, Reference Manual

Page: 186 / 190

Care must be taken in checking compatibility of the control unit when selecting the
required HART transmitter. Ensure that the input voltage requirements of the transmitter
and the loop resistance are below the limits given in
Table E-1 .
Some Explosion-proof (Exd) rated transmitters have a high input voltage requirement
which can result in HART communication failing to function at high loop currents. For
example, the Explosion-proof version of the Rosemount 5400 Series Transmitter has a
minimum input voltage requirement as follows:
• 15.5 Vdc at 21.75 mA
• 20 Vdc at 3.75 mA
The Exd version of Rosemount 5400 Series Transmitter would not be suitable for use with
the control unit.
Table E-1 shows the minimum control unit terminal output voltage (worst case
conditions) for varying load conditions.
Table E-1: Minimum Control Unit Terminal Output Voltages
Load current mA Rosemount 3490
terminal voltage
Vdc
Maximum loop
resistance ohms
3.75 20.9 2370 Minimum fault current
4.0 20.8 2195 Normal minimum output
20.0 13.9 95 Normal maximum output
21.75 13.5 50 Maximum o/p Rosemount fault level
22.5 12.8
(1)
35 Maximum o/p NAMUR NE43 fault level
(1) Minimum output voltage is 12.8 Vdc. The maximum loop resistance quoted ensures there will be
at least 12 Vdc available at the transmitter.
E.3.2 Universal and common practice commands
Support for the Universal and Common Practice commands of all other HART 5/6/7
transmitters is provided in accordance with HART practice.
Table C-2 shows the menu structure and parameters for generic HART 5/6/7 transmitters
parameters as seen on a control unit and other HART-based devices.
Universal commands
• #0 Read unique identifier
• #1 Read primary variable
• #2 Read loop current and percent of range
• #3 Read dynamic variables and loop current
• #6 Write polling address
• #7 Read loop configuration
• #12 Read message
Support for HART
®
Transmitters Reference Manual
January 2021 00809-0100-4841
186 Emerson.com/Rosemount