An electrostatic discharge (ESD) question... 2

[Tobalcane]

I have asked this question in onther forum with no luck, so I will try it here.

I inherited shock test equipment that is very crude, but the company has been using it for years. The vibrator is fasten to a patio paver and in turn sits in a wooden box full of sand. The wood, sand, and patio paver are insulators, can they generate a static charge; are they ESD safe? The vibrator is grounded, so I am not worried about "zaps", butI would rather be safe than sorry.

Your comments would be appreciated.

Thank you in advance.


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Tobalcane


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Tobalcane

 

[Skogsgurra]

It is all a question of humidity.

If you are in an area where humidity is in the 10 - 25 percent range, there could be a risk that charges build up. But you can easily reduce that risk by adding some moisture to the sand and let it seep into the wood. You could also use conductive paint. Talk to 3M, they have lots of stuff for these things.

Gunnar Englund

http://www.gke.org

 

[Tobalcane]

Thanks skogsgurra for responding.

The area that it is in I think is humidiy controled, I have to look into that. But, do you know if the wood, sand, and pato paver is ESD safe? Do you know if the items can generate static?

Thanks again.

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Tobalcane

 

[Skogsgurra]

Anything that isolates and rubs/shakes/glides/separates does generate static electricity. But the insulation level has to be very hich for the levels to build up. This reference:

http://www.school-for-champions.com/science/static_materials.htm

has a simple explanation and also shows how different materials behave with respect to charging.

As you can see, wood is neutral and not prone to building up any charge. There are several other sites that you can find if you google "triboelectricity" (that is what ESD and related things are called in academia).

Gunnar Englund

http://www.gke.org

 

[Tobalcane]

Thanks skogsgurra!

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Tobalcane

 

[IRstuff]

sand is mostly glass

TTFN

 

[Tobalcane]

Good point IRstuff...

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Tobalcane

 

[Tobalcane]

Im just thinking out loud...is it safe to say (according to Triboelectric Series) that the sand will charge up like glass?

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Tobalcane

 

[IRstuff]

The individual grains will probably charge up, but I not sure what the aggregate would do.

TTFN

 

[Skogsgurra]

Yes, sand is mostly glass - or kind of. But sand as we meet it in nature has a rather low resistivity due to impurities and humidity as well as a grainy structure - not solid glass. It is not at all difficult to have below hundred ohms from a ten feet grounding rod driven into sand.

You need gigaohms (1000 000 000 ohms) or more to have an ESD problem from the described setup.

Gunnar Englund

http://www.gke.org

 

[Tobalcane]

Well in my case the patio paver is vibrating on top of the sand, I would feel that the paver is neutral and since there is no striping of electrons with the sand there is no static being generated, the same for the wood box. Since there is no static being generated I guess it is safe.

Thanks for the information and thoughts on this matter.

If you want to add more comment, please do.


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Tobalcane