FFT of vibration data, please help

Dear friends

I have vibration data from the device, I need to convert it into Freq Domain (Magnitude vs Freq). I've tried several times and still stuck, I can't import that data into the formula/function. I've attached an excel file I got from the device. maybe you can download and see the excel files for complete information. Could you guys help me, what function/formula should I write? and how to find the max point in the plot?

[karim Bouaouiche]

Hello Monte

Please help me

I want the vibration signals of the bearing as MATLAB or csv files for complete a signal processing study.

Cordially.

Answer 1

[Star Strider]

Try this:

D = xlsread('TEK0000.csv');
t = D(:,3);
s = D(:,4);

figure
plot(t, s)
grid
xlabel('Time (s)')
ylabel('V')

Ts = mean(diff(t));                                     % Sampling Interval
Fs = 1/Ts;                                              % Sampling Frequency
Fn = Fs/2;                                              % Nyquist Frequency
L = numel(t);                                           % Signal Length
sm = s - mean(s);                                       % Mean-Corrected Signal (Eliminates 0 Hz Offset)
FTs = fft(sm)/L;                                        % Fourier Transform
Fv = linspace(0, 1, fix(L/2)+1)*Fn;                     % Frequency Vector
Iv = 1:numel(Fv);                                       % Index Vector
[MaxV,idx] = max(abs(FTs(Iv))*2);                       % Maximum V & Index
Freq = Fv(idx);                                         % Frequency Of Maximum V

figure
plot(Fv, abs(FTs(Iv))*2)
grid
text(Freq, MaxV, sprintf('\\leftarrow %.4f V, %.0f Hz', MaxV, Freq), 'HorizontalAlignment','left')

See the documentation for the various functions for details.

[Star Strider]

The online Run feature provides with that code —

D = readmatrix('https://www.mathworks.com/matlabcentral/answers/uploaded_files/240300/TEK0000.CSV');
t = D(:,4);
s = D(:,5);

figure
plot(t, s)
grid
xlabel('Time (s)')
ylabel('V')

Ts = mean(diff(t));                                     % Sampling Interval
Fs = 1/Ts;                                              % Sampling Frequency
Fn = Fs/2;                                              % Nyquist Frequency
L = numel(t);                                           % Signal Length
sm = s - mean(s);                                       % Mean-Corrected Signal (Eliminates 0 Hz Offset)
FTs = fft(sm)/L;                                        % Fourier Transform
Fv = linspace(0, 1, fix(L/2)+1)*Fn;                     % Frequency Vector
Iv = 1:numel(Fv);                                       % Index Vector
[MaxV,idx] = max(abs(FTs(Iv))*2);                       % Maximum V & Index
Freq = Fv(idx);                                         % Frequency Of Maximum V

figure
plot(Fv, abs(FTs(Iv))*2)
grid
text(Freq, MaxV, sprintf('\\leftarrow %.4f V, %.0f Hz', MaxV, Freq), 'HorizontalAlignment','left')

.

Answer 2

[ndiaye bara]

Hello ,

Try this code

%%

clear; close all; clc

data = readtable('TEK0000.csv') ;

t = data.Var4;

amp = data.Var5;

amp = amp-mean(amp);

figure, plot(t/1e-3,amp), grid on

xlabel('Time [ms]')

ylabel('Amp [V]')

nfft = 2^15;

dt = t(2) - t(1);

df = 1/dt/nfft;

f = (0:(nfft-1))*df;

spec = abs(fft(amp,nfft));

figure, plot(f,spec,'r'), grid on

xlabel('Frequency [Hz]')

ylabel('|FFT|')

set(gca,'xlim',[0 12500])

Regards