w2aew | #305: Measuring Total Harmonic Distortion THD using an FFT on an oscilloscope @w2aew | Uploaded October 2019 | Updated October 2024, 3 hours ago.
This video shows how to use the FFT function on an oscilloscope to measure the relative amplitude of the harmonic distortion components of a signal, and then take those results and compute the THD, or Total Harmonic Distortion. Actual measurements are shown, and results are validated by a THD calculator in the scope as well as a THD measuring multimeter.

Videos mentioned in this video are:
Audio Compressor project: youtu.be/1h0FZJYXQ_w
Demo of above: youtu.be/pUii_pDQxg8
Basics of using FFT: youtu.be/oRf-IpG6XAw
Basics of dB: youtu.be/1mulRI-EZ80
Notes from this video:
qsl.net/w2aew/youtube/THD_with_FFT.pdf