MATLAB: Trying to take FFT of a signal but not getting the correct result

digital signal processingfftMATLABsignal processing

t1=load('201710h1.lvm'); %test 1
t2=load('201710h2.lvm'); %test 2
Fs = 100000; % frequency sample
x = t1 (:,1); % time for test 1
sin = t1 (:,2); % test 1 sesnor 1
plot(sin)
title('Sensor1')

Best Answer

Perhaps calling the fft function would get you closer.
Example — 
t{1}=load('201710h1.lvm');  %test 1 
t{2}=load('201710h2.lvm');  %test 2
Fs = 100000; % frequency sample
for k = 1:numel(t)
    L = numel(t{k});
    Ts = 1/Fs;
    Fn = Fs/2;
    tv = linspace(0, L, L)*Ts;
    FTt = fft(t{k})/L;
    Fv = linspace(0, 1, fix(L/2)+1)*Fn;
    Iv = 1:numel(Fv);
    
    figure
    plot(tv, t{k})
    grid
    xlabel('Time (sec)')
    ylabel('Signal (Units)')
    title(sprintf('t_{%d} Time Domain',k))
    
    figure
    plot(Fv, abs(FTt(Iv))*2)
    grid
    xlabel('Frequency (Hz)')
    ylabel('Amplitude (Units)')
    title(sprintf('t_{%d} Frequency Domain',k))
end
Note that I loaded your signals into cell arrays to make the analysis easier.
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