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???
11/12/06 03:34
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 		 #127797 - I think, yes
Responding to: ???'s previous message
Andy said:
On that basis, wouldn't it be simpler to just do a (digital) filter to separate the harmonics (all of 'em) from the fundamental?

You would need a sharp filter to separate the 50Hz fundamental from all the harmonics, providing a slope of at least 60dB/ocatve. When using a FIR this means lots of taps, at least 200, I guess.

So, I don't think that digital filtering is much simpler.

Kai

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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