Emerson AMS Trex Device Communicator User Manual page 147

User Guide
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.
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.
www.
Loop Diagnostics application
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September 2021
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