Emerson AMS Trex User Manual page 136

Loop Diagnostics application
Figure 4-3:
Power a transmitter
The Trex unit can power one transmitter. When the Trex unit powers a transmitter, an
internal 167 Ohm resistor is used, so an external resistor is not necessary. If you already
connected an external resistor in series with the red or black HART terminal on the Trex
unit, there will be less voltage available for the device, especially at 20 mA. This may cause
the device to power off. The Trex unit begins providing power when you tap OK.
WARNING!
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.
128
Select the type of device to power
User Guide