The Trex unit can provide up to 16 volts (at 22.5 mA) to power a HART device. You do not need to add an external resistor. The Trex unit has a 167 Ohm internal resistor in the HART + pwr terminals that is used when the Trex unit provides power to the transmitter.
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.
Connect the lead set to the
HART + pwr terminals on the Trex unit and to
Power a 2-wire transmitter
- On the Loop Diagnostics screen, tap Trex Unit Power.
The Trex unit uses an internal resistor while powering the device.
Loop Diagnostics is now powering the transmitter and measuring voltage and current.
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.