[sdiy] Measuring THD of a sine wave

[Tiago Ventura]

Greetings folks!

The technical literature in general, *whenever* it bumps into the
topic of sine wave generation techniques the difficulty of generating
such a signal is always mentioned. And then, several techniques and
circuits are presented and analyzed. The THD% of these circuits are
mentioned for comparison purposes.

How the heck are these distortion levels measured or calculated in practice?
What are the main techniques and procedures applied in order to
measure the total harmonic distortion (THD%) of a given sine wave?

The idea of using a second sine wave as a comparative reference of
what is "pure" is pretty obvious, but what kind of source would be
able to present an acceptable "purity" for this purpose? (a digital
source sounds ridiculous for this but I can't think about anything
else!)

Remembering that it is essential to also calculate the accuracy of
this measurement. Are there other alternative techniques for making
such a measurement? Is there anything available in the technical
literature exploring this subject?

Any thoughts/comments/suggestions would be greatly appreciated.

Tiago Ventura

Greetings from Porto Alegre/Brazil
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