Hioki MEMORY HiCORDER 8855, Instruction Manual

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4.8 FFT Analysis Function
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4.8.12 Octave Analysis [OCT]
Function
Horizontal
cursor
Vertical
cursor
Vertical axis Display
LIN-REAL (real number) -
LIN-IMAG (imaginary number) -
LIN-MAG (amplitude) OCT
LOG-MAG (logarithmic amplitude) 10log (OCT)
PHASE -
This function displays the spectrum of a noise signal or other signal, using
1/1-octave or 1/3-octave band filters with fixed ratio.
Main uses
Frequency analysis of noise
OCT
1/1 OCT 1/1-octave band filtering
1/3 OCT 1/3-octave band filtering
LIN-MAG Linear display of octave analysis value as voltage
LOG-MAG Logarithmic display of octave analysis value as dB
For frequency analysis of a noise signal or similar, the signal is passed
through fixed-ratio band filters with 1/1-octave or 1/3-octave bandwidth.
As opposed to the power spectrum function, where the signal is divided into
bands of identical width and the power in each band is displayed, octave
analysis divides the frequency axis evenly on a logarithmic scale and
expresses the level as a bar for each band.
In analog octave analysis, the octave band center frequencies and filter
characteristics are determined according to the ANSI CLASS 3 standard. In
the 8855, the power spectrum is measured first and bundling is then used to
perform 1/1-octave or 1/3-octave analysis. This allows the following analysis
functions:
5-band 1/1-octave analysis
15-band 1/3-octave analysis
15-band 1/3-octave analysis and filter characteristics of the 8855 correspond
to the ANSI CLASS 3 standard. However, in the upper bands of frequency
analysis, there are no leak components from higher frequencies.
For example, the 20 kHz band contains no leak components from the 25 kHz
band or other bands.
15-band 1/3-octave analysis
In this mode, the 400 spectrum lines of regular frequency analysis are
bundled into 1/3 octave bands and shown as a bar graph.
5-band 1/1-octave analysis
In this mode, the 400 spectrum lines of regular frequency analysis are
bundled into 1/1 octave bands and shown as a bar graph.