[sdiy] Measuring THD of a sine wave

[Jackalope Billy]

I think it comes down to what level of accuracy you need to achieve with
your THD measurement. You can get a decent estimation of THD by looking at
an FFT of the output resulting from your stimulus signal.

If you need high accuracy you can go big with equipment from Audio
Precision. They actually have a decent amount of relevant technical
documentation on their website that is available once you register with
them.

https://www.ap.com/technical-library/?search_type=tech-library&search=THD&load_page=1

-Bill


On Fri, Nov 11, 2022 at 4:42 PM Tiago Ventura via Synth-diy <
synth-diy at synth-diy.org> wrote:

> 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
> -30.03376474999071, -51.238242916392814
> https://www.instagram.com/psychoincorp/
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at synth-diy.org
> http://synth-diy.org/mailman/listinfo/synth-diy
> Selling or trading? Use marketplace at synth-diy.org
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://synth-diy.org/pipermail/synth-diy/attachments/20221111/d9130f0f/attachment.htm>