Re: [Ee] Field mill

Well, I finally found the odd duck I was looking for.  Pasco scientific,
PS-3211

It has a 30V bipolar range and communicates by bluetooth by phone app.

About $40 on ebay.


On Sat, Jun 7, 2025, 3:56 PM David VanHorn <[email protected]> wrote:

> " As a hypothetical, if you lay a 100ft pair of 24AWG wires with 300V
> insulation on the ground, and lightning strikes one end, what potential
> appears on the other end? The potential is with respect to what? And for
> how long does the potential exist? Is it likely and/or possible and/or
> desirable for the wire to survive a direct strike at one end of the cable?"
>
> The potential that matters is what ends up across me or my vehicle, or my
> equipment.  It lasts some milliseconds.  It's not likely that the field
> mill or the wire would survive a direct hit.  20 to 50 kA does interesting
> things.
> The old trueism that lightning never strikes the same place twice isn't
> really true, but frequently it's somewhat true as "the same place" isn't
> there anymore. :)
>
> I'd urge you to read up on Charles Steinmentz and everything by Martin
> Uman.
> https://en.wikipedia.org/wiki/Martin_A._Uman
>
> That copper wire MAY perf it's insulation near the tripod and leave me
> with only a few hundred volts, or it may become a plasma channel with
> resistance of a few ohms leading the bulk of the strike directly to me.
> I'm not willing to risk a copper path that leads directly to me.   Even if
> only a few hundred volts, it could easily be lethal. It will be rather
> humid, and I may well be very wet.
> I will also be FAR from any medical support. Heart goes into Vfib and I'm
> done.
>
>
> On Sat, Jun 7, 2025 at 4:02 AM Jason White <
> [email protected]> wrote:
>
>> I used to design direct lightning strike circuit protection networks for
>> avionics - so I might be biased.
>>
>> You probably already possess about a dozen ways of getting a reading to
>> you
>> safely with stuff you have just laying around.
>>
>> As a hypothetical, if you lay a 100ft pair of 24AWG wires with 300V
>> insulation on the ground, and lightning strikes one end, what potential
>> appears on the other end? The potential is with respect to what? And for
>> how long does the potential exist? Is it likely and/or possible and/or
>> desirable for the wire to survive a direct strike at one end of the cable?
>>
>> Suppose the end of the cable was attached to an indicator: a $5 meter, or
>> LED sting, or whatever. What would it take to render said indicator safe
>> to
>> stand next to and look at? Is it possible for the indicator to be usable
>> without ever touching it? Is it likely and/or possible and/or desirable
>> for
>> the indicator to survive a direct strike at one end of the cable?
>>
>> I can speculate, but I'd like to hear what you and others think.
>>
>> I'm genuinely curious about the answers. My intuition tells me one thing,
>> but maybe I could be wrong.
>> --
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>
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