Low-Frequency noise Possible cause Action
The device or shield is not
properly grounded.
Ensure the device is properly
grounded.
Ensure the shield is properly
isolated from the terminal
housing. The shield should be
grounded at only one location
on the entire fieldbus segment
and it should be a high-quality
ground.
Repeat these checks for all
devices on the fieldbus segment.
The power supply is not
supplying a good, stable
voltage.
Ensure the power supply is
properly installed. Isolate the
power supply and check for
noise.
In-band frequency noise Possible cause Action
Higher than expected The device or shield is not
properly grounded.
Ensure the device is properly
grounded.
Ensure the shield is properly
isolated from the terminal
housing. The shield should be
grounded at only one location on
the entire fieldbus segment and
it should be a high-quality
ground.
A cable may be damaged. Visually inspect the cables and
test the resistance between the
two wires and each wire against
the ground.
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.
Fieldbus Diagnostics application User Guide
September 2021
176 User Guide
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