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I know how to plot the Fourier transform, but is there a more precise way to measure the total harmonic distortion?

I have this graph:

fourier

As you see, there's only one distinguishable component at 1 kHz which is what I want. I need a THD less than 5% . Is the ThD zero here?

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  • \$\begingroup\$ Well it certainly is, based on your plot, but your plot is rather useless. Try removing the mean of your input signal before computing the FFT. Either way, the calculation from your fixed data set is going to largely depend on the number of samples and on your windowing function. \$\endgroup\$ Jul 10 '18 at 21:42
  • \$\begingroup\$ @BlairFonville How do i remove the mean? \$\endgroup\$
    – Mah
    Jul 10 '18 at 21:53
  • \$\begingroup\$ Take the ratios of rms harmonics to fundamental \$\endgroup\$ Jul 10 '18 at 23:57
  • \$\begingroup\$ @TonyEErocketscientist The thing is I can only see one peak at 1 kHz. \$\endgroup\$
    – Mah
    Jul 11 '18 at 1:49
  • \$\begingroup\$ Yes I see better now. Can't you normalize it on a log scale? \$\endgroup\$ Jul 11 '18 at 2:03
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I ended up transferring the data to a DAT file. You can access that in the graph tab for that.

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