Harmonic distortion

Discussion in 'Homework Help' started by ronybhai, Sep 17, 2013.

  1. ronybhai

    Thread Starter Member

    Sep 18, 2012
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    what method could be used to estimate the harmonic distortion in the output of an oscillator?
     
  2. vk6zgo

    Active Member

    Jul 21, 2012
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    If you want to simply estimate the harmonic distortion,you could compare the waveshape to an ideal sinewave,but there are a number of ways in which you can test for it:

    (1) Examine the signal with a Spectrum Analyser,or perhaps the FFT function of a DSO.

    (2) Use a Band Stop (notch) filter centred on the fundamental frequency.
    Everything at the output will be either distortion or noise,so you will read Distortion +Noise--if the noise is very low level it may be neglected.(this is the classic method used in the Noise & Distortion test set).

    (3) Use a Selective Millivoltmeter.
    First,tune to the fundamental,then to each harmonic in turn.
     
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  3. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    This is homework forum. Normally one expects the OP to show some effort before some form of answer is furnished.

    Why not simply look at Wikipedia for a start? Or Google THD meter ....
     
  4. vk6zgo

    Active Member

    Jul 21, 2012
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    True,but if he doesn't know anything,my answers won't make any sense to him!
     
  5. WBahn

    Moderator

    Mar 31, 2012
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    And he may not care if all he wants is the answers to copy onto his homework and turn in.

    I don't think that is the case with this OP, if I'm recalling from prior experience. But who knows?

    Actually -- with this OP that may well be all he cares about. I just went and looked at a couple of prior threads of his, such as this one:

    http://forum.allaboutcircuits.com/showthread.php?t=78015

    and getting him to do anything other than want the answer spoon fed to him was like pulling teeth.
     
  6. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    There are waveform analyzers that are designed to specifically read THD. They are the easiest to use.
     
  7. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    Presumably that reasoning would apply to anyone who posts in the homework forum. They don't know so they ask for help.
     
  8. ronybhai

    Thread Starter Member

    Sep 18, 2012
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    I was kind of thinkig about the 1st answer you gave. Thanks
     
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