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???
11/11/06 11:44
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 		 #127775 - How about this method for THD.
Responding to: ???'s previous message
Dear Friends,

1. Measure the Line frequency to determine sampling interval.
2. Take 64 samples in one cycle using sampling interval above.
3. Determine RMS of the sample and call it SIGNALRMS.
4. Do 64 point FFT on above data and compute peak amplitude of fundamental amplitude[1] in Albertos code.
4. Compute TRMS of fundamental by Peak Amplitude of fundamental / 1.414 and call it FUNDRMS

5. Now THD = (SIGNALRMS-FUNDRMS)*100/SIGNALRMS

will the above method work or ther are any loopholes.

Thanks & Regards,
Prahlad Purohit

List of 32 messages in thread
TopicAuthorDate
Measuring THD [ Total Harmonic distortion ]            01/01/70 00:00      
   ANalogue method.            01/01/70 00:00      
      Re: Analogue method.            01/01/70 00:00      
         fundamental flaw?            01/01/70 00:00      
            Re: Fundamental Flaw.            01/01/70 00:00      
               Digital filter            01/01/70 00:00      
                  Re: Fundamental Frequency.            01/01/70 00:00      
               FFT            01/01/70 00:00      
                  mains frequency            01/01/70 00:00      
                     Why rely on an assumption?            01/01/70 00:00      
                  Re: FFT            01/01/70 00:00      
                     FFT            01/01/70 00:00      
         What use?            01/01/70 00:00      
   Goertzel filters, maybe ?            01/01/70 00:00      
   FFT is the first choice            01/01/70 00:00      
      Is it?            01/01/70 00:00      
         If you know the fundamental.            01/01/70 00:00      
            Re: Fundamental            01/01/70 00:00      
               Multiple cycles            01/01/70 00:00      
                  The 50Hz fundamental must dominate            01/01/70 00:00      
               Fundamental and harmonics!            01/01/70 00:00      
                  Re: Fundamental and harmonics.            01/01/70 00:00      
                     You're getting into theory            01/01/70 00:00      
                     That is very simple!            01/01/70 00:00      
         I think, yes            01/01/70 00:00      
   Alfredos Code Doesnt seem to work properly.            01/01/70 00:00      
      Do you want it to write in "C"?            01/01/70 00:00      
         Yes Kai,            01/01/70 00:00      
      Eh? Endian issue.            01/01/70 00:00      
         Tags            01/01/70 00:00      
   How about this method for THD.            01/01/70 00:00      
      Mix of numerical calculation and FFT            01/01/70 00:00      

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