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https://www.youtube.com/shorts/JaT8jT_vL24

In the video above where I was standing about 3.5 feet away from the EEG unit and electrodes connected to it. Whenever I waved my hands, there were large amplitude distortions in the EEG display (zoomed in but still 3.5 feet away). Before and after the waveforms were more uniform and have flatter amplitudes.

Can electric flux from the human body or hands travel 3.5 feet away to affect the electrode wires serving as antenna? What is the magnitude of this electric flux that can do it? Is this called capacitive coupling? or is the effect somehow magnetic field?

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What you're seeing is probably the effect of changing field of electric potential in the room, and thus also changing electrostatic component of total electric field. Moving your body can cause such changes, because potential is not the same everywhere (air is not very conductive), and human body can carry electric charge. I recall that similar effects on oscilloscope can be seen when rubbing your shoes against the floor. It is most probably not caused by induced electric field, this is usually noticeable only at high frequencies and only for some convenient wire geometries (coils).

You can call this effect "capacitive coupling" but that is more of an engineering term for one electric circuit component interacting with another component via electrostatic part of total electric field. Here we have interaction of voltmeter/"oscilloscope in DC mode" with environment in which charges can move.

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  • $\begingroup$ What is usually the frequency of this electric potential in the room? $\endgroup$
    – Jtl
    Commented Jan 22, 2023 at 6:47
  • $\begingroup$ By the way. This effect only happens when the electrodes or leads were NOT connected to the head. If they are connected, the ambient changing electric potential from moving hands can no longer affect the waveforms. Why is that? and what frequency is it all? Thanks. $\endgroup$
    – Jtl
    Commented Jan 22, 2023 at 20:35
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    $\begingroup$ Electric potential "in the air" usually does not have single frequency. I meant changes associated with changes in body position. If you wave your hands or jump up and down, potential will follow those motions. $\endgroup$
    – Ján Lalinský
    Commented Jan 22, 2023 at 23:40
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    $\begingroup$ When probes are well connected to a body, they measure potential difference between parts of that body, not potential difference between two probes without contact in the air. A well conductive contact with the body changes potential on the probe, but mere close proximity without contact much less so. So in the two cases naturally the result is different. Somebody waving hands/jumping up and down can influence potential field substantially in the air, but only weakly in the conductive human body. $\endgroup$
    – Ján Lalinský
    Commented Jan 23, 2023 at 0:11
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    $\begingroup$ It may lower the effect, but not completely. The two probes are not in the same position in space, and thus they are not being influenced in the same way by redistribution of charge in the room. $\endgroup$
    – Ján Lalinský
    Commented Jan 23, 2023 at 0:37
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This is actually a type of artifact seen in hospitals when performing sEEG, which I've seen firsthand. I even jumped up and down a few feet from the machines which resulted in similar spikes as you are seeing.

I've been trying to figure out this issue as well, but you are absolutely NOT the only one who has encountered this. Surprisingly, however, I have not been able to locate any useful research.

I'm interested to find an answer as well, so if you've managed to figure anything out, please share!

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  • $\begingroup$ Welcome to PSE! Please do not post an answer, if you do not really answer the question, it will usually be downvoted or deleted. If you're interested in this post, you can mark it below the buttons to vote and later look, if an answer has appeared. With a little bit of reputation (>50) if I remember correctly, you can also comment on the question. If you have questions, I'd like to help you. $\endgroup$
    – Samuel Adrian Antz
    Commented Jan 18, 2023 at 18:29
  • $\begingroup$ This does not provide an answer to the question. Once you have sufficient reputation you will be able to comment on any post; instead, provide answers that don't require clarification from the asker. - From Review $\endgroup$
    – Michael Seifert
    Commented Jan 18, 2023 at 18:49

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