MATLAB: FFT of vibration data

fft

I have vibration data in time domain and i m unable to do FFT of this. please guide me

sampling rate 800 sample/sec

thanks

Best Answer

     Fs = 800; % sampling rate of 1000 Hz
     t = 0:1/Fs:1-1/Fs;
     x = ad2;
     xdft = fft(x);
     xdft = xdft(1:length(x)/2+1);
     DF = Fs/length(x); % frequency increment
     freqvec = 0:DF:Fs/2;
     plot(freqvec,abs(xdft))

I hope this can work

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MATLAB: Sampling rate and fft

No, you don't need to specify the sampling rate, but if you wish to create a meaning frequency vector, then you need to know the sampling rate.

For example:

    Fs = 1000; % sampling rate of 1000 Hz
    t = 0:1/Fs:1-1/Fs;
    x = cos(2*pi*100*t)+randn(size(t));
    xdft = fft(x);
    xdft = xdft(1:length(x)/2+1);
    DF = Fs/length(x); % frequency increment
    freqvec = 0:DF:Fs/2;
    plot(freqvec,abs(xdft))

so the output of fft() is agnostic about frequency, but if you want to interpret that output in physical frequencies, then you need to know the sampling rate.

MATLAB: Code for ploting fourier transform spectrum

spectrogram()

Best Answer

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MATLAB: Sampling rate and fft

MATLAB: Code for ploting fourier transform spectrum

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