Loop Diagnostics Application - Emerson AMS Trex User Manual

4

Loop Diagnostics application

Topics covered in this chapter:
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The Loop Diagnostics application helps you troubleshoot the wiring of a 4-20 mA current
loop by measuring the voltage and the current. The application can also power a
transmitter or positioner to isolate the device from its current loop and to verify its
operation.
Note
The Trex unit needs the Device Communicator Plus communication module to use the Loop
Diagnostics application. You may also need a second lead set.
If you connect the Trex unit's HART terminals in series with an externally-powered loop,
you can enable Trex Unit Current and have the Trex unit control current (similar to how a
transmitter controls current). Controlling current lets you do the following:
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If the Trex unit is not connected to an externally-powered loop, you can enable Trex Unit
Power to power one transmitter or positioner. This helps you isolate a problematic device
from its current loop and verify its operation. Powering a device lets you do the following:
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User Guide
Open or close the Loop Diagnostics application
Loop Diagnostics screen
Powering transmitters or positioners from Loop Diagnostics
Voltage and current measurements in Loop Diagnostics
Wiring diagrams for the Loop Diagnostics application
Power a 2-wire transmitter
Power a 2-wire transmitter and measure analog output
Power a positioner
Stroke a valve
Settings for controlling current
Loop checks
Verify the input module on a digital control system.
Verify the cabling between the connection point and the input module on a digital
control system.
Move a positioner.
Verify a transmitter in isolation by powering the device and measuring the output.
Verify a positioner in isolation by powering and moving the positioner.
Perform wiring continuity checks on cables where no power exists.
Loop Diagnostics application
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