Ams trex™ Device Communicator

Checks after installation
Use the Field Communicator application on the Trex unit to verify the device is
communicating.
For transmitters, use the Loop Diagnostics application to verify power and loop current.
The HART terminals on the Trex unit can measure voltage. Connect the HART terminals to
the communication terminals on the device to ensure there is adequate voltage. To
measure the current, connect the mA terminals to the test terminal on the device to
measure the 4-20 mA output. If the device does not have a test terminal and the loop is
removed from control, connect the mA terminals in series with the device's negative
communication terminals to verify the 4-20 mA output.
For positioners, connect the HART terminals to the device's communication terminals to
measure and verify there is adequate voltage. If you suspect a bad digital control system
output current, connect the mA terminals in series with the positioner's negative
communication terminals to measure and verify the 4-20 mA output.
Troubleshoot a HART loop
•
Attempt the tasks from the "Checks after installation" section.
User Guide 
Loop Diagnostics application
September 2021
User Guide 
147

---

•
Simplify the problem by removing one or more components from the HART loop.
Attempt tasks from the "Checks after installation" section.
•
Isolate the device and perform tasks from "Checks before installation."
4.11.1
Measure voltage on an externally-powered loop
You can use the HART terminals on the Trex unit to measure the voltage on an externally-
powered device/loop.
Note
Use the HART + pwr terminals if you want the Trex unit to power the device and measure
voltage. See 
Power a 2-wire transmitter
.