Emerson AMS Trex Device Communicator User Manual page 159

User Guide
5.5
User Guide
1.800.561.8187
Figure 5-4: Connect to an externally-powered fieldbus segment
For small fieldbus segments, the power conditioner and terminators can be contained in a
single wiring block.
Note
You can connect the Trex unit at any convenient place along the fieldbus segment (bus). In
the field, this is typically done at the device or at the fieldbus junction box. The drawing
below is one example.
A. Terminators
B. Power conditioner
C. Fieldbus power supply
D. Host system
Power a FOUNDATION fieldbus device
The Trex unit can power one FOUNDATION fieldbus device. The Trex unit can provide
approximately 10 volts at 25 mA to power a FOUNDATION fieldbus device. (The Trex unit
will draw approximately 12 mA when it is online)
If you try to apply power from the Trex unit when the device is externally-powered, the
Fieldbus Diagnostics application prevents the Trex unit from supplying power. This
protects the Trex unit from damage.
Note
When the Trex unit powers a FOUNDATION fieldbus device, two internal terminators and a
power conditioner are applied. Ensure the device is not connected to a fieldbus segment,
even if the segment is unpowered.
CAUTION
Remove the USB cable from the Trex unit before connecting to a device.
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Fieldbus Diagnostics application
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September 2021
159