[Bored chemist]

Concrete is a much better conductor than people think.
https://en.wikipedia.org/wiki/Electrical_resistivity_measurement_of_concrete

Plastic chairs are notorious.
To generate static, you usually need a couple of insulators rubbing.
Cotton is hygroscopic enough not to be good at the job.
(Hair is less conductive.)

[talanum1 (OP)]

The charge Q = CV depends on the human body's capacitance.

[alancalverd]

No.

Until V exceeds the breakdown potential of air, Q depends on the area of contact between the static-generating surfaces, the nature of the surfaces, and the precise movement of rubbing and separating them. C is a constant, so the dependent variable is V. You can see this clearly in any controllable static generator like a Van der Graaff or Wimshurst machine - or even the adhesive tape generator depicted in this website https://www.thenakedscientists.com/get-naked/experiments/glowing-tape.  The initial voltage is zero and increases as more charges are separated and the separation is increased.   

[Bored chemist]

Does anyone have the tech etc. to model a door, its frame and so on as a transmission line?
:-)
I'm fairly sure that the "lumped element" version's not up to the job.

[vhfpmr]

The current charging the handle capacitance is tens of amps for a few ns, the current leaking to ground through the door is 100uA for 20ms, my guess is that it's the former that you feel, not the latter.

[alancalverd]

Neat sim!

The IEC assumption of human body impedance for shock protection purposes is 1kΩ in parallel with 0.1μF for hand-to-hand full contact (normally damp hands). However for single finger dry touch the measured value is in the range 100 kΩ - 10 MΩ. This will give you more realistic i and t values for the discharge characteristic, but the curves will look the same.     

[Bored chemist]

Does the (order of 2µH) inductance make a difference?
https://www.qsl.net/in3otd/ind1calc.html

I suspect it must
You have 20Kv to play with and that's going to change the current in the inductor by 20,000 = 0.000002 dI/dT
About 10^10 A/sec
You have something like 10^-9 seconds to change it, so that limits the current to about 10A.
That's roughly the same as the current you calculated, so the effect of the inductor will be comparable with that of the "resistor" used to model the arc. (And an established arc has a negative incremental resistance).
The approximate value calculated for  the inductance might be more accurate than the guessed value of the resistance.

[vhfpmr]

So this is fairly close to the IEC standard for ESD testing. The specification is behind a paywall, and the snippets I can glean from application notes are a bit sparse, but their model for the body appears to be 150pF and 330Ω, with four levels of 2, 4, 6, & 8kV. I found reference to source inductance for risetime shaping, but no inductance. The risetime is specified as 700ps - 1ns, so an inductance of about 150nH plonks it in that range.

I've seen mention of IEC standard and 'human body' standard, but no detail of the difference. There's also mention of air discharge vs contact discharge, but no detail. The waveform I'm getting into a short circuit matches the published one in all but peak amplitude. It refers to 30A, but I'm getting 24A (8kV/330Ω)


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2μH is quite a lot of inductance, it's about right for a 2m loop of wire, but I'm not sure how representative that is. Inductance is dependent on conductor cross section, but I'm not sure quite how you'd go about quantifying that when the dielectric for the body capacitance amounts to the whole room volume. A 2μH inductor gives a very slow risetime and is significantly underdamped, but that brings us back to the need to know what load the test circuit is calibrated into.


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[Bored chemist]

I wasn't kidding when I said

I'm fairly sure that the "lumped element" version's not up to the job.

The "single turn inductor calculator I found on line does take account of the conductor diameter.
I think I put 5 cm in as representative of a wrist and a 3m perimeter.
Apparently people have a resistivity of about 200 ohm cm.
https://pubmed.ncbi.nlm.nih.gov/10593226/
And if this  calculator
https://www.allaboutcircuits.com/tools/skin-depth-calculator/
 is right, that means we have an electrical skin depth of about 5cm at 0.2 GHz
So I think we can pretty much ignore that.

I'm not sure how one would model the whole lossy capacitive inductive system.

One quick sanity check, If you have a current of 20A in an inductor of 2 µH then you have  as stored energy of 0.5*20*20*0.000002 J
That's 400 µJ
And the capacitor stores 0.5* 150 E-12 * 20,000*20,000
about 30mJ
So there's plenty of energy available to drive the current.

[talanum1 (OP)]

The resistance between the door handle and the door frame is 10k - 175 k Ohm.

[Bored chemist]

The resistance between the door handle and the door frame is 10k - 175 k Ohm.

That's interesting to know.

Are you able to measure the resistance to Earth- perhaps  a metal water pipe?