Ams trex™ Device Communicator

4.11
Loop checks
The Loop Diagnostics application enables loop checks by measuring voltage and current,
and controlling the current to simulate a transmitter.
Loop Diagnostics application
User Guide
September 2021
146
User Guide

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Checks before installation
Before a device is installed, verify its operation. You can enable the Trex Unit Power option
to power the device. For a transmitter, use the Trex unit to power the transmitter and
measure the 4-20 mA output. For a positioner, use the Trex unit to power the positioner,
control the current, and ensure the positioner moves as expected when the current
changes.
Checks during installation
You can use the Trex unit to verify a partially-installed loop. You can do the following:
•
Connect the Trex HART terminals where the device will be installed. Verify the power
supply voltage is measured, and that the voltage is large enough for a device.
•
Connect the Trex HART terminals where a transmitter will be installed and enable 
Trex
Unit Current
to simulate a transmitter's 4-20 mA output. Verify the digital control
system reads current from the Trex unit.
•
Connect the Trex HART + pwr terminals where the power supply will be installed on a
transmitter loop and enable 
Trex Unit Power
. The Trex unit can measure the 4-20 mA
output from the transmitter.
•
Connect the Trex HART + pwr terminals where the power supply will be installed on a
positioner loop and enable 
Trex Unit Power
. Verify the device is powered and the
voltage level is set by the positioner.
•
Connect the Trex HART + pwr terminals where the device will be installed on an
unpowered transmitter loop and enable 
Trex Unit Power
to simulate a transmitter.
Verify the digital control system reads output current from the Trex unit.
•
Connect the Trex mA terminals at the location where a positioner will be installed.
Verify the ammeter reads 4-20 mA when the digital control system output module is
enabled.