Emerson AMS Trex Device Communicator User Manual page 155

User Guide
5.3
User Guide
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communication on an externally- powered fieldbus segment, Go Online starts fieldbus
network communications so fieldbus signals can be measured.
Note
If you connect the Trex unit to an active fieldbus segment with a LAS, the devices, the
device addresses, and signal measurements are displayed on the Details screen. However,
the device's tag is displayed only after you tap Go Online.
Note
The Fieldbus Diagnostics application does not show which device is the LAS on the fieldbus
segment. The Trex unit will become the LAS if no other LAS is on the fieldbus segment.
CAUTION
The Trex unit draws approximately 12 mA from the fieldbus segment when it is online.
(The Trex unit draws 0 mA when it is offline.) Ensure the power supply or barrier on the
fieldbus segment has the capacity to provide this additional current when the Trex unit is
online. If a heavily loaded fieldbus segment is drawing near the capacity of the segment's
power supply, connecting the Trex unit may result in loss of communication.
GOOD, BAD, and CHECK measurements in
Fieldbus Diagnostics
The Fieldbus Diagnostics application uses labels of GOOD, BAD, and CHECK to indicate the
status of a measurement. The label is applied based on the measurement being within a
set of ranges that you can adjust. By default, the range of values includes typical operating
levels of DC voltage, noise, and signal-level based on the Fieldbus standard.
You can set the range of measurement values that are labeled GOOD, BAD, or CHECK in
the Settings. (Tap Settings → Measurement criteria.) You may want to increase or
decrease the range of values based on where the Trex unit is connected on the fieldbus
segment.
Status
GOOD
BAD
www.
Description
The measurement is within the minimum and maximum values set
in the measurement criteria.
The measurement is below the minimum value set in the
measurement criteria. The BAD status is used for the DC voltage and
signal measurements.
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Fieldbus Diagnostics application
September 2021
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