Problem with THD+N from HarmonicAnalyzer

[xearthl]

Hello,

I have saved the screenshot of the document in a .jpg file.

From my point of view Harmonic Analyzer Using Signal is giving a perfect result.

But I am really curious about the result given by that instrument.

It seems that the sampling rate is OK.  And I think you can get a better result if the number of samples covers exactly n periods of the square wave, like 262000 samples. But I don’t think the error coud be that large since you have sampled more than 1000 periods.

And have you used any window to avoid spectrum leakage?

Thanks,

Joyce

[Asky2010]

Hi, thanks a lot.

I wil check the operation of equipmen later.

I have ever try to set the samples to be n periods and use window, but it didn't work well.

And with using window, it will get error when the input is simple sanewave.

Are there other places where I may make mistakes？

[Asky2010]

I make the test with different input size which are 262000 and 262144. The results of THD are the same, but a little diference in THD+N.

With the window, the THD becomes lower.

[xearthl]

Hello,

What kind of window are you using?

Could you please try Hanning window?

Thanks,

Joyce

[Asky2010]

I have try Hanning window, but it make the result lower than 48%.

Thanks for your patient very much