Emerson AMS Trex User Manual page 134

Loop Diagnostics application
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Loop Diagnostics when powering a positioner and taking measurements
The voltage measured at the HART or HART + pwr terminals
Enable/disable the Trex unit to provide power to a transmitter or power and source current to a
positioner. This lets you isolate a problematic device from its HART loop and verify its operation.
Use the HART + pwr terminals on the Trex unit.
Enable/disable the Trex unit to control current to an externally-powered positioner or to an analog
input card on a digital control system. The Trex unit controls current the same way as a
transmitter. Use the HART terminals on the Trex unit when the Trex Unit Power option is off. This
option is automatically enabled if Trex Unit Power is on and the Trex unit is powering a positioner.
Change the settings for supplying/controlling current, including the values of the quick buttons, the
scale for the up and down arrows, and the time to change to a new current value. This option is
enabled only when Trex Unit Power or Trex Unit Current is on.
The quick buttons to control the current to the positioner or 4-20 mA current loop. You can change
the values of the buttons from the More Options button.
The current measured at the mA, HART + pwr, or HART terminals on the Trex unit. If Trex Unit Power
is off and Trex Unit Current is on, use the HART terminals to measure current.
The terminals that are controlling/measuring current and voltage are circled in green. Tap the
image to see a larger version.
The current that the Trex unit is supplying.
The up and down arrows to gradually increase or decrease the current. The default increment is
0.10 mA. You can change this increment from More Options.
Tap the pencil icon to enter a new current value to be supplied.
User Guide