Soft dB Opus Suite Data Logger Module - Manual (Page 33)

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This is the type spectrum. Narrow Band, octave, 1/3-octave and 1/12-
octave set-ups are possible. The octave, 1/3 octave and 1/12-octave
types are computed with a frequency bank of filters applied on the
narrow band spectrum. To avoid low frequency imprecision, we suggest
using the maximum number of lines (8192) set-up when an octave type
is selected.
The dB/Lin. parameter allows choosing the amplitude scale format. The
choices are dB, dB(A), lin. rms, lin. peak, lin. rms 2 , ISO2631-XY (dB),
ISO2631-Z (dB), ISO2631-XY (lin. rms et lin. peak) and ISO2631-Z (lin.
rms et lin. peak). The ISO2631 selections allow applying standard
frequency weighting to the average power spectrum.
The Integration parameter allows applying a simple or double
integration in the frequency domain for an acceleration measurement.
For the simple integration option, the power spectrum is divided by jω.
For the double integration option, the spectrum is divided by –ω 2 .
The function Export .txt allows exporting the average power spectrum in text format.
9.1.3 Statistics
This module allows computing the standard Lx% statistics on the global level historic for the entire
framework of the selected channel. The Statistic function starts by computing the global levels of the
framework with an adjustable time resolution. The global level calculation is done with power
spectra using blocks with a number of samples adjusted to match the requested time step. A Hanning
time window is used for the FFT computation. The power spectrum approach is used to facilitate the
A-weighting and integration options. When the global level historic is computed, the Statistics
module computes the statistics of the global levels and presents a graph of the sorted global levels.
The interface of the Statistics function is presented in the next figure.