Ams trex™ Device Communicator

Trex internal resistor
Note
The Trex unit must be connected in series with the transmitter to use the internal resistor.
Do not put more than 25V DC on the circuit.
A — Voltage source
Device connection wizard prompts
Answer
Do you intend to provide power from the
Trex unit?
No
Leads are attached to:
Transmitter
Change Polling Option?
Tap 
Yes
if the device is not at address zero.
Increase loop resistance?
Tap 
Yes
to enable the internal resistor.
User Guide 
Field Communicator application
September 2021
User Guide 
73

---

Figure 3-15: Connect to a 4-wire HART transmitter
If you have a 250 Ohm resistor, you can insert it in between the device terminals and
connect the lead set across the resistor. Otherwise, you can enable the internal resistor in
the device connection wizard.
Note
Ensure you review the device documentation for connecting/setting up HART
communication. Devices may have different terminals or requirements.
A — Voltage source
Device connection wizard prompts
Answer
Do you intend to provide power from the
Trex unit?
No
Leads are attached to:
Transmitter
Change Polling Option?
Tap 
Yes
if the device is not at address zero.
Increase loop resistance?
Tap 
Yes
if there is no external resistor between the
device terminals.
Figure 3-16: Power and connect to a HART positioner
Field Communicator application
User Guide
September 2021
74
User Guide

---

Device connection wizard prompts
Answer
Do you intend to provide power from the
Trex unit?
Yes
Are you providing power to a transmitter or
positioner?
Positioner
Change Polling Option?
Tap 
Yes
if the device is not at address zero.
Increase loop current?
Tap 
Yes
to increase the current from 4 mA to
another value, if the device did not initially
communicate.