FFT results correct for following filtering?

I have inductive measurement data that i want to filter with a lowpass, so first i want to get the frequency spectrum to know what to filter out.

I used the following code to do the FFT motivated by an answer to a question i was reading here.

%% FFT
load('CH0.mat');
load('t.mat');

L = numel(CH0);
Ts = mean(diff(t));
Fs = 1/Ts;
Fn = Fs/2;
CH0FT = fft(CH0-mean(CH0),[],1)/L;
Fv = linspace(0, 1, fix(L/2)+1)*Fn;
Iv = 1:numel(Fv);
CH0abs = abs(CH0FT);
plot(Fv,mag2db(CH0abs(Iv)*2));

As you see it look like this:

Usually i would expect a peak at a certain frequency so i could filter the other frequencys out but here is just a big peak near zero and also the frequencys are smaller than i would expect.

Do you see any mistakes or is it just the way my sensor measures? How would you filter it? I also attached the data. Thank you!

Answer 1

[Star Strider]

It is my code ( apparently copied from is the FFT right? ) and I do not see any mistakes in it!

That signal and ‘CH0’ here are apparently quite noisy with a large low-frequency component. Consider using a lowpass filter if you only want to isolate the low-frequency component (likely 0 to 0.001 frequency units here).