Emerson AMS Trex - Power a Positioner

4.8 Power a positioner
If you try to apply power from the Trex unit when the device is externally-powered, the
Loop Diagnostics application prevents the Trex unit from supplying power. This protects
the Trex unit from damage.
CAUTION!
Remove the USB cable from the Trex unit before connecting to a device.
CAUTION!
Do not add any external power to the device when the Trex unit is powering the device. This
can blow a fuse inside the Trex unit. The repair/replacement will need to be completed at an
authorized service center. Ensure the device is disconnected from the loop/segment and no
other wires are connected to the device before providing power from the Trex unit.
Procedure
1. Connect the lead set to the HART + pwr terminals on the Trex unit and to the
positioner.
Connection for powering a positionerFigure 4-16:
2. On the Loop Diagnostics screen, tap Trex Unit Power.
3. Select one of the following:
Option Description
Power Positioner with 4 mA (0%) Power a positioner using 4 mA.
Power Positioner with 20 mA (100%) Power a positioner using 20 mA.
Power Positioner with other mA value Power a positioner using a specified mA
value.
4. Tap OK.
Loop Diagnostics application
User Guide 139