Sources Of Noise And Phantom Signals - EA Technology UltraTEV Plus2 Operating Manual

EA Technology UltraTEV Plus

8.3.8 Sources of Noise and Phantom Signals

The following images present some examples of how unwanted signals may be introduced
during the PD detection process when using the Ultrasonic Contact Probe. These can be
categorised as sources of noise and sources of phantom PD signals. The difference between
the two is that noise decreases our detection capabilities by masking the PD signal, whereas
phantom signals may be confused as a PD source.
The first image shows that when the UCP is kept in the hand during measurements, even
tiny movements of the hand can introduce significant noise to measurements through
surface noise. In cases where it is necessary to hold the Ultrasonic Contact Probe during
measurements (e.g. pushing the sensor to obtain more signal or non-magnetic asset
enclosure), a coupling fluid may help to reduce this type of noise.
Any vibrations of the asset surface caused for example by rain in outdoor assets or vibration
of transformers may cause phantom signals. In such cases the audible signal may be appear
exactly the same as a genuine PD source. These two examples are illustrated in the second
and third images.
Contact
1) Shaking Ultrasonic Contact Probe, e.g. when held in the hand
2) Rain in outdoor assets
3) Vibration (including transformers) of asset enclosure where the Ultrasonic Contact
Probe is attached
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