THD calculation for ADC

[samiti]

Hello all,

I'm trying to calculate THD(total harmonic distorsion) parameter of an ADC, the point is that i must calculate the FFt
in order to get THD without using any of the labview VIs (FFt and Vrms VIs) i've made the VI
joined below(i used some vis found on NI forums), the problem is that i still don't have an idea how to replace Vrms vi with math nodes.
 
If anyone could help me, i would be greatfull

Regards,

NB:i'm using 2009 labview basic version

[GerdW]

Hi smiti,

you have been asking this in a different thread, so why don't you stick with your original one?

To replace the Vrms VI you could simply look into it to get it's internals. To replace the FFT vi is just silly...

[samiti]

  hi GerdW!

thank you for being interessted with my work,i want to notice that i'm new in this forum, i've posted THD calculation in a different topic beacause the first one was too much complicated i understood that because i didn't get many suggestions from forum members.that's why i've decided to go easy with begenning with THD problem.

Now you suggested me to look for Vrms Block diagram and the point is that i don(t know how to do it ( i've noticed in my first message that i didn't have the signal toolkit)

thank you for hrlping me.

Best regards,

SAMiti

[Sivakanth]

You can try interfacing FFTW dll into labview.

The FFTW can be found at http://www.fftw.org/install/windows.html 

Interfacing to dlls in LabVIEW is discussed here: https://www.ni.com/docs/en-US/bundle/370109b/resource/370109b.pdf

When you have FFT result, arriving at various Vrms values should be a breeze through.

Good Luck!