Emerson AMS Trex Device Communicator User Manual page 178

Fieldbus Diagnostics application
September 2021
178
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Fieldbus signal
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Possible cause
The Trex unit is powering a
FOUNDATION fieldbus device,
but it is not attached directly to
the device terminals.
When the Trex unit powers a
FOUNDATION fieldbus device,
non-standard terminators are
used to meet Intrinsic Safety
requirements. This slightly
changes the fieldbus signal, and
the signal amplitude is increased
by 20 to 30 percent. The signal
amplitude for the Trex unit is not
impacted.
The fieldbus segment is missing
a terminator.
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User Guide
Action
Ensure the Trex unit is
connected directly to a single
FOUNDATION fieldbus device.
No other wires should be
connected to the device.
Ensure there are no resistors in-
series with the device's
terminals.
None. This is normal when the
Trex unit is providing power.
The higher signal level is
acceptable on these
terminators.
Attach another fieldbus
terminator to the fieldbus
segment.
User Guide
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