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Discussion in 'Electronic Design' started by Duane Peterson, Jun 6, 2007.

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  1. I was observing a 2MHz sinewave on my CRO, 200V at very low amperage.

    When I shorted the test leads, with one hand on the probe and the
    other on the ground clip, the waveform reduced to one quarter the
    original amplitude, and was distorted. This raised a number of
    questions regarding impedance.

    Is the lost amplitude being absorbed by my body? If so, is it absorbed
    as the waveform represented on the CRO _before_, or _after_, the
    shorting?

    Is such reduction in amplitude indicative of an impedance match, or
    would a good match result in little or no waveform degradation?

    Thank you for any insights.

    Duane Peterson
     
  2. mpm

    mpm Guest

    A good match would result in more power transfer, hence a lower
    voltage available at the scope terminal. An open circuit would
    present minimum loading.

    Implicit in your premise is the notion that the 2MHz is a constant
    voltage source.
    More likely, you are simply de-tuning it in addition to providing an
    alternate path to ground - even if some of that path is capacitively
    coupled. Or electromagnetically coupled. This is 2MHz after all.
    Does that help? -mpm

    Be thankful it wasn't higher current.
    RF burns can take a while to heal. (Don't ask me how I know that. :)
     
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