Emerson Smart Wireless THUM Quick Start Manual page 4

Quick Start Guide
Field Communicator connections
In order for the Field Communicator to interface with the THUM Adapter, the
wired device must be powered. The Field Communicator must be put into poll
mode and should use the THUM Adapter address of 63.
1.5 Power supply
Minimum loop load of 250 Ohms.

The THUM Adapter communicates via and derives power from a standard

4–20 mA/HART
loop which is linear from 2.25 V at 3.5 mA to 1.2 V at 25 mA. Under fault
conditions, the maximum voltage drop is 2.5 V. The THUM Adapter will not
affect the 4–20 mA signal under normal or fault conditions as long as the loop
has at least a 2.5 V margin at the maximum loop current (25 mA for a typical
4–20 mA/HART device).
Limit the power supply to 0.5 Amps maximum and voltage to 55 Vdc.

Loop current
3.5 mA
25 mA
1.6 Load resistor
If required, add a load resistor as shown in
page 13, and
the application (1W minimum) and be compatible with the supplied splice
connector which accepts wire sizes from 14 to 22 AWG.
1.7 Loop
To ensure proper operation, the THUM Adapter should not be installed on a HART
loop with other active HART masters. HART masters that are active periodically,
such as a field communicator can be used on a loop with a THUM Adapter.
4
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loop. The THUM Adapter causes a small voltage drop on the
THUM Adapter voltage drop
2.25 V
1.2 V
Figure 16 on page
Figure 8 on page
15. The resistor should be adequately rated for
June 2016
10, Figure 12 on