Get n-th harmonic of acquisition by API

QA40x
1

I’ve been using Arta and Steps for years before I got the QA403. The Steps program was able to create a graph which plots the first 6 harmonics over frequency which is assential when designing an amplifier. I think I need the same data wich is displayed in the THD Bargraph visualizer. I could not find any sourcecode of [ThdBargraph] How can I get the n-th harmonic via the REST api after doing an acquisition? Or do I have to process the fft data myself for that?
I want to create an opensource c# program which plots this graph:

Distortion vs Frequency % - 8 Ohm
Distortion vs Frequency % - 8 Ohm1793×981 21.7 KB

Thanks.

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I think I figured it out. I got the idea to use wireshark and see what ThdBargraph does.

{C9D53270-C126-409F-8D97-824566FBE7F9}
{C9D53270-C126-409F-8D97-824566FBE7F9}1038×338 26.5 KB

I will create an application which sets the generator to a certain frequency and then I will get the harmonics by calculating the bins and get their value with PeakDbv.

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Hi @breedj, via REST you can run an acquisition, and then ask the REST server to compute the THD for you. For example, if you did the acq with a 1 kHz tone and wanted to look at all harmonics through 20k that would be:

GET localhost:9402/ThdDb/1000/20000

Note that you can adjust the stop frequency for the calc. So, if you want to look at the THD with a 100 Hz fundamental with just the harmonics up to and including 500 Hz you could issue:

GET localhost:9402/ThdDb/100/500

That would return the left/right channel THD ratio expressed in dB. You can also do ThdPct if you’d like in percent.

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BTW, have you seen the REST API? Hit the link below with the QA40x app running and it should dump the entire API.

http://localhost:9402/

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Thanks Matt. I’ve discovered the api and already started using it. I think it is perfect for what I like to do and easy to use. I will use PeakDbv instead of ThdDb because it does not give me the distortion of the single harmonics, only a range where the start is always the fundamental. But I have tested PeakDbv where you can specify a custom frequency range and it is perfect for what I need. And I noticed I can also use /Data/Frequency/Input and do my own calculations as well.

I will post a link to the repository of my program after I’ve have made a working version. I will first compare the results with some other systems like Audio Precision.