High-frequency noise Possible cause Action
Higher than expected There may be loose wire
connections.
Check for loose connections.
Vibration from nearby motors
or wind gusts may cause loose
connections to be displayed as
high-frequency noise.
Water or moisture may be in
the device's terminal housing.
Check the device's terminal
housing.
A cable may be damaged. Use the signal or DC voltage
measurement to find the cable
portion that may be damaged.
Visually inspect the cables, and
test the resistance between the
two wires and each wire to the
ground.
Variable-frequency drives
installed near the fieldbus
segment may not have the
recommended grounding and
filtering.
Check the grounding and
filtering that are used.
Fieldbus signal Possible cause Action
Lower than expected The Trex unit is attached far
away from the FOUNDATION
fieldbus device that is
transmitting the signal.
Connect the Trex unit directly
to the communication
terminals on the device. No
other wires should be
connected to the device.
Ensure the device is
disconnected from any other
terminators or devices.
Connect the Trex unit to a
connection point that is closer
to the device on the fieldbus
segment.
The cable between the Trex unit
and the device is damaged.
Determine if the signal loss is
acceptable. If it is not, replace
the cable between the Trex unit
and the device.
Fieldbus signals can be received
when they are 250 mVp-p or
higher, so loss of signal
amplitude is tolerable.
Fieldbus Diagnostics application
176 User Guide
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