SVT THD and Harmonic Components VI

[James985]

when I using SVT THD and Harmonic Components VI to analysis waveforms, sometimes it will report THD as NaN. 

I want to know in which situation will report the THD as NaN.

 

[altenbach]

Please attach a simplified VI and some data that gives you NaN as a result. Is THD the only NaN output? What are the values of all the other inputs to the function? Do you get an error code?

[James985]

Hi Altenbach,

Thanks for replying.

Attached a VI a waveform to analysis the waveform THD performance.

The waveform is a step sine sweep waveform, there is a pilot signal 0.01s 1000Hz added before the sweep waveform, need to cut off before the analysis. And the sweep waveform is start from 20000Hz to 100Hz. Min Cycles is 10,Min Time is 10, Octave is 12.

Not every frequency THD is NaN, but some of the result is NaN.

[altenbach]

Thanks.

Sorry, I don't have the SV toolkilt, but I am sure I can do some more troubleshooting.

• Please don't use unusual archives (.7z) because not everybody wants to install useless software. Please use plain "zip" where compression and extraction is already built into any modern OS and no extra software is needed..
• Can you also wire from the THD output to the loop boundary to create an array. Run your VI then make the values of the THD array the default before saving. This way we can tell where the NaNs occur. (Or just make the data in the THD graph the default before saving).

[altenbach]

Did you ever look at the subset output right before the THD measurements?

(Just place a 1000ms delay in the loop and hook up a waveform graph to that wire, then watch the graph!) 

I really think you are not slicing&dicing the waveform correctly. can you double-check the math (There are just plain silly things, for example taking 1/x of the frequency then dividing by that. That's just a multiplication!). Merging a single error does not really do anything useful. etc)