Setting The Average Type - Commtest Instruments vb Series Instrument Reference Manual

Setting the Average Type

When vibration is measured, several spectra are usually measured
and then averaged to produce an average vibration chart. The
averaging process minimizes the effect of random variations or noise
spikes that are inherent in vibration signals. Averaging is applied to
amplitude values, not to the frequency range.
Linear averaging is suitable for most cases. The amplitude value at
each frequency of a spectrum is added to the same frequency of the
next spectrum. The sum is then divided by the number of averages
taken.
Exponential averaging is normally used only if vibration behavior
varies significantly during measurement, such as during run-up and
coast-down measurements. The most recent spectra have more
influence on the final average than earlier measurements. Averaging
is continuous until the measurement is stopped.
Peak hold is useful for measuring the maximum amplitude peak that
occurs over a period of time and for measuring resonances during a
bump test. Peak hold does not actually average the amplitude values
but records and displays the maximum amplitude of each spectral
line.
•
Press
Exponential and Peak hold.
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to cycle through the Average Types, Linear,
Section 4: Manual Setup Measurement Parameters 73