Skin contact loading
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Posted by Duane Peterson on June 6, 2007, 3:49 am
Please log in for more thread options 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 | |||||||||||||
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Posted by mpm on June 6, 2007, 12:32 pm
Please log in for more thread options 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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