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Old 08-18-2011, 02:58 PM
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Question Faraday Cage ~ 2 Ground or Not 2 Ground



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I have read Both ways?? Anyone know for a fact which is the proper way????
Old 08-18-2011, 03:40 PM
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Good luck with that.

What I've read is that to properly ground a Faraday cage is not that simple. Further, that small Faraday cages don't really need it.

The problem is that if you don't do it properly, you may end up simply conducting the EMP pulse, amplified of course, right to your Faraday cage.

Have some small aluminum boxes that I use as my Faraday cages. I do not ground them, nor do I intend to unless I find some good reason to do it:





I've lined them with cardboard to insulate the contents from the case. The lids connect electrically to the body of the box via the clamps. I've tested it with a multi-meter.
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Old 08-18-2011, 04:43 PM
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Quote:
Originally Posted by lildrestl3 View Post
I have read Both ways?? Anyone know for a fact which is the proper way????
I agree, there is an unresolved debate out there. I found the better written, more scientifically believable articles saying not to ground.

If you have a necessity item (medical device or whatever), store two in identical ammo or similar faradays cages, one grounded, one not.
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Old 08-18-2011, 04:50 PM
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Here are a few articles from which I draw some of the conclusions I've made. Unfortunately, there is also an article online written by an electrical engineer or some such that explains clearly how to ground a Faraday cage, and why it's difficult to do so effectively. I keep searching for it, if I find it I'll post the link.

Meanwhile, these articles are, IMO, pretty good:

http://www.futurescience.com/emp/emp-protection.html

http://www.aussurvivalist.com/nuclear/empprotection.htm
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Old 08-18-2011, 05:03 PM
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Jeez, all current runs to "ground",...a bar of copper ten feet in length sunk eight feet into the Ground.

The cage does not destroy the charge, it merely stops it from entering, the ground connection bleeds the charge to GROUND, basic.
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Old 08-18-2011, 06:02 PM
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Here's another article I found about EMP grounding. IMO, worth reading:

http://www.futurescience.com/emp/emp-grounding.html
Old 08-18-2011, 06:06 PM
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Quote:
Originally Posted by Eyebone View Post
Jeez, all current runs to "ground",...a bar of copper ten feet in length sunk eight feet into the Ground.

The cage does not destroy the charge, it merely stops it from entering, the ground connection bleeds the charge to GROUND, basic.
Eyebone is correct, all current tries to find a path to ground. Anyone asking the grounding question should realize that the path to ground can be through a person who touches the box.
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Old 08-18-2011, 06:18 PM
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The article provided by Goose is spot on. My cage is copper. Its a box. Its under ground. The box is grounded on all 4 corners to ground rods. It sits on a rubber mat. The articles inside it are wrapped in foil then rubber(old waders) then more foil. They sit on the rubber floor and do not touch the sides or each other.. The cage is in a root cellar with 3 feet of earth over the top. Im not concerned. Kingfish
Old 08-18-2011, 06:20 PM
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Quote:
Originally Posted by goose3 View Post
Here's another article I found about EMP grounding. IMO, worth reading:

http://www.futurescience.com/emp/emp-grounding.html
That article leaves me with a question, why would anyone leave 10 feet of ground bar above the ground?, that is not common practice.

+1 for the shielded ground wire.
Old 08-18-2011, 07:39 PM
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Let me grab the popcorn...

Yet another thread were the experts can't even explain to 1st graders about magnetism....


THIS is going to get good ... I can feel it ...
Old 08-18-2011, 07:50 PM
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Let me grab the popcorn...

Yet another thread were the experts can't even explain to 1st graders about magnetism....


THIS is going to get good ... I can feel it ...
Come on, you give it a shot.
Old 08-18-2011, 09:55 PM
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Quote:
Originally Posted by lildrestl3 View Post
I have read Both ways?? Anyone know for a fact which is the proper way????
It makes no difference.

On the inside, cage potential IS the reference voltage -- no matter what it's doing relative to anything outside the cage.

That's what a Faraday cage does -- that's the whole point of the thing.
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Old 08-19-2011, 01:06 AM
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My understanding is ,grounding attracts attention, like a lightening rod.
An ungrounded shield is simply shielding ,if there is no flow the charge has no where to initiate much less need to travel it.
Lightening doesn't strike a car setting on rubber tires.
But people have died standing inside a steel gazibo during a thunder storm.
How much simpler can this get ?
Old 08-19-2011, 02:04 AM
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Lightning is not the same thing as an electromagnetic pulse.
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Old 08-19-2011, 08:09 AM
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Quote:
Originally Posted by Eyebone View Post
Jeez, all current runs to "ground",...a bar of copper ten feet in length sunk eight feet into the Ground.

The cage does not destroy the charge, it merely stops it from entering, the ground connection bleeds the charge to GROUND, basic.
What he said. The bolt or pulse may last only a micro-second, but all that energy's got to go SOMEwhere at the speed of light or, if through a wire, pretty close to it. A grounding wire directs where it goes. Keep it short, without sharp bends, and of the biggest gauge you can get, and connected to a serious grounding bar or bar array.
Old 08-19-2011, 08:27 AM
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Quote:
Originally Posted by Eyebone View Post
Jeez, all current runs to "ground",...a bar of copper ten feet in length sunk eight feet into the Ground.

The cage does not destroy the charge, it merely stops it from entering, the ground connection bleeds the charge to GROUND, basic.
I can see this working for E1 and E2 charges but E3 will produce GICs that travel through the earth in form of quasi dc. You could be looking at tens of thousands Ampers feeding it's way up through the grounds and neutral wires. My concern would be the basic fundamentals of electricity. We know electricity will always take the path of least resistance and we know anytime you rapidly increase and decrease electricity it tends to excite molecules which will produce an electrical arc in the path of least resistance. It also tends to seek and find equilibrium and produces magnetic fields. To me it seems like an EMP could create all kinds of electrical phenomenon that otherwise would go undetected.
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Old 08-19-2011, 09:24 AM
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i got a question.

if your electronic device was grounded to earth, would an emp blast destroy the electronic device or would the energy be directed towards earth and become harmless?
Old 08-19-2011, 09:50 AM
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Now you see Why I posted this
Old 08-19-2011, 10:53 AM
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Quote:
Originally Posted by lildrestl3 View Post
Now you see Why I posted this
Yes, I do. This question/discussion (albeit short) arose at the talk I was at with the One Second After author, Dr. Bill Forstschen, the other night. And there was no clear resolution there either. He had brought along someone who is doing 'research' apparently into this sort of thing but even he has no clear answers for us right now.

On the other hand, I guess it is not wrong to ground everything if you can. I cannot see that it would do any harm. Whether it is ok not to ground up to a certain size or with a certain material or whatever the variable may be seems to be the question.
Old 08-19-2011, 11:11 AM
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From everything I know, grounding is not good. An EMP works through induced current. That means any length of wire will be automatically given a current through it. It's called an antenna. From what i understand, it can completely undermine the Faraday cage. The cage acts as a shield, not allowing too much current to be produced and letting the EMP pass over it. My recommendation, no ground.
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