DS-0321 FFT解析機能ソフトウェア

DS-0321 FFT解析機能ソフトウェア
DS-0321 FFT Analysis Software
Integration method of the time waveform by using the IFFT
ONO SOKKI CO., LTD.
DS-0321 FFT Analysis Software
Integration method of the time waveform by using the IFFT
■Overview of the function
This document describes the method to convert the time waveform of acceleration into displacement
by using the IFFT function.
Obtain the Fourier spectrum by the FFT analysis of the time waveform of acceleration.
After that, perform the frequency axis (j ω calculation) double integration to the obtained Fourier
spectrum. Then, cuts out unnecessary low-frequency component and limits the bandwidth. The time
waveform of the displacement that is double integrated can be obtained by returning it to the time
waveform by IFFT calculation.
This document describes the operation procedure which uses a frequency differential and integral
function and IFFT calculation function. The basic operation procedure is omitted in here.
■ Operation flow
1. Displaying the time waveform and power spectrum
of acceleration value
2. Displaying the Fourier spectrum
3. Operating double integral
4. Operating IFFT calculation by using band limitation
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■Operation procedure
1.
Displaying the time waveform and power spectrum of the acceleration value.
Display the shock waveform measured by accelerometer. Select rectangular for the window function.
Click [Input/ Output Setting] > [Window Function Setting] in this order to select [Rectangular].
Display the time waveform in the upper side and Fourier spectrum in the lower side.
Change the graph display and data kind.
Time
Time Real
Fourier Spectrum Meg
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2.
Perform double integration to the Fourier spectrum.
Select the lower Fourier spectrum graph, and click [Analysis Setting] > [Freq Calculus] in this order to
select [Double integral].
Double Integral
Fourier Spectrum
Time Real
Execute the double integration.
Fourier Spectrum Mag
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3.
Execute the IFFT calculation by applying the band-limit.
Set a band to be limited by using the Delta cursor. Select 0 Hz to 10 Hz in here and cut out this
range.
Select Delta
Execute the IFFT calculation by applying the band limitation.
Activate the band limitation function and IFFT function. The horizontal axis of the Fourier spectrum
graph becomes time and the graph is changed from acceleration to displacement time waveform.
-4-
Time Real
Fourier Spectrum Real
When you operate the analysis setting, the time waveform of acceleration can be converted to the
time waveform of displacement which applies band limitation in the real-time measurement.
― END ―
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