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Quick Installation Guide
00825-0100-4075, Rev BA
February 2010
Smart Wireless THUM Adapter
4
Power Supply
Minimum loop load of 250 Ohms.
The THUM Adapter communicates via and derives power from a standard 4-20 mA/HART
®
loop. The THUM Adapter causes a small voltage drop on the 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 Volts DC.
Load Resistor
If required, add a load resistor as shown in Figure 8, 12, and 16. The resistor should be
adequately rated for the application (1W minimum) and be compatible with the supplied
splice connector which accepts wire sizes from 14 to 22 AWG.
BENCH TOP CONFIGURATION
When performing bench top configuration it is suggested that you connect the THUM
Adapter to a wired device. If this is not possible the following wiring diagrams can be used.
For bench top configuration ensure that the power supply that you are using is limited to 0.5
Amps maximum.
Figure 2. THUM Adapter Only, Powered by a Current Source (Such as a Fluke 744)
Loop Current THUM Adapter voltage drop
3.5 mA 2.25 V
25 mA 1.2 V
Ground
-
20 mA
Current
Source
HART
Modem
THUM Adapter
Green
Red
Black
White
Yellow
+
4075_QIG_Rev_BA.fm Page 4 Friday, February 19, 2010 11:08 AM