Measuring harmonic components

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teemumm
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Measuring harmonic components

Post by teemumm » Sun May 05, 2019 3:14 pm

In PicoScope 6 spectrum view you can measure THD% of the signal. But is there any way to measure automatically harmonic components of the distortion? Of course you can do this by looking from the graph, but I guess the software measures the components when calculating THD%. Can you somehow see them?

Gerry
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Joined: Mon Aug 11, 2014 11:14 am

Re: Measuring harmonic components

Post by Gerry » Tue May 07, 2019 10:11 am

Hi teemumm,

I'm not entirely sure what you're asking.

THD is measured using a sine wave with no harmonics, so the components of THD are the harmonics that appear in the captured the signal. So a square wave will have 40-50% THD (an ideal squarewave will have 48.3%), and you can see all of the harmonics visible above the noise floor in the display.

If you go to the Measurements menu and select THD for the measurement, then you will get a measurement automatically appearing at the bottom of the screen. As long as you are in 'Magnitude Display Mode', the THD measurement will always reflect what is being captured, so it is automatically applied to real-time data. If you are capturing more than one waveform and using Average Display Mode, so that the statistics of the measurement are also being calculated, then the measurement will be a running total. If you then change the waveform, the data continues to be accumulated, so the THD value will be incorrect (as it will be now accumulating data from the new waveform to add to the old one), so if you then need to see the true THD value for the new waveform, you need to stop and restart the capture.

If the answer to your question is not in the information that I've provided, then could you explain in more detail exactly what you are looking for.

Regards,

Gerry
Gerry
Technical Specialist

teemumm
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Joined: Sun May 18, 2014 1:32 pm

Re: Measuring harmonic components

Post by teemumm » Tue May 07, 2019 11:58 am

What I mean is that I would like to know the distribution of different harmonic components in distortion. For example how much of THD% consist 2nd harmonic and how much of it is 3rd harmonic. Surely I can measure this visually from the graph, but is there way to measure it automatically numerically?

Gerry
PICO STAFF
PICO STAFF
Posts: 443
Joined: Mon Aug 11, 2014 11:14 am

Re: Measuring harmonic components

Post by Gerry » Wed May 08, 2019 10:06 am

Hi teemumm,

No, there is no way to do what you ask automatically (unless you use our Software Development Kit to perform your own FFT plot and create the measurement in code).

Regards,

Gerry
Gerry
Technical Specialist

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