Ams trex™ Device Communicator

4.7
Power a 2-wire transmitter and measure
analog output
You can remove a 2-wire HART transmitter from a loop, use the Trex unit to power the
transmitter, and then measure the analog output.
If you try to apply power from the Trex unit when the device is externally-powered, the
Loop Diagnostics application prevents the Trex unit from supplying power. This protects
the Trex unit from damage.
 CAUTION
Remove the USB cable from the Trex unit before connecting to a device.
Loop Diagnostics application
User Guide
September 2021
140
User Guide

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 CAUTION
Do not add any external power to the device when the Trex unit is powering the device.
This can blow a fuse inside the Trex unit. The repair/replacement will need to be
completed at an authorized service center. Ensure the device is disconnected from the
loop/segment and no other wires are connected to the device before providing power
from the Trex unit.
Note
Do not insert a resistor in parallel with either the HART + pwr or HART terminals on the
Trex unit, or in parallel with the device's communication terminals. This will interfere with
the current measurements.
Procedure
1. Connect the lead set to the 
HART + pwr
terminals on the Trex unit and to the
transmitter.
Figure 4-15: Connection for providing power to the device
2. On the 
Loop Diagnostics
screen, tap 
Trex Unit Power
.
3. Tap 
Power Transmitter
.
The Trex unit uses an internal resistor while powering the device.
4. Tap 
OK
.
The Trex unit powers the device. The voltage and current measurements are
displayed.
5. To stop powering the device, do one of the following:
•
Tap 
Trex Unit Power
to set the option to 
Off
.
•
Tap 
Exit
.
•
Remove the lead set from the Trex unit.