EZ Digital DS-1000 Series, Руководство по эксплуатации

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2-3-3 USING FFT(FAST FOURIER TRANSFORMATION)
With Fast Fourier Transform (FFT), you can transform a waveform from a
displayed value of its amplitude against time to one that plots the amplitudes
of the several discrete frequencies the waveform has. Use FFT in the
following applications:
A
Analyzing impulse response of filters and Amplifier
A
Analyzing noise in DC power source
A Measuring harmonic content and distortion in systems
A
Analyzing harmonics in 50 and 60 Hz power lines
A
Analyzing vibration frequency
The FFT computes and displays the frequency content of a waveform you
acquire as an FFT math waveform. This frequency domain waveform is based on
the following equation:
Where: x(n) is a point in the time domain record data array
X(k) is a point in the frequency domain record data array
n is the index to the time domain data array
k is the index to the frequency domain data array
N is the FFT length
j is the square root of -1
X(k) =
N
-
1
N-1
- j2 kn/N
(n)e
n=0
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