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.
Note
Do not insert a resistor in parallel with either the HART + pwr or HART terminals on the
Trex unit, or in parallel with the device's communication terminals. This will interfere with
the current measurements.
Procedure
1. Connect the lead set to the HART + pwr terminals on the Trex unit and to the
transmitter.
Figure 4-15: Connection for providing power to the device
2. On the Loop Diagnostics screen, tap Trex Unit Power.
3. Tap Power Transmitter.
The Trex unit uses an internal resistor while powering the device.
4. Tap OK.
The Trex unit powers the device. The voltage and current measurements are
displayed.
5. To stop powering the device, do one of the following:
• Tap Trex Unit Power to set the option to Off.
• Tap Exit.
• Remove the lead set from the Trex unit.
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.
User Guide Loop Diagnostics application
September 2021
User Guide 141
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