Emi

Given that personal computers must be designed to class B electromagnetic interference regulations from EEC directives and that the metal case is an integral part in this regulation, then in what way do perspex cases or windows in the PC case effect other household appliances or vice-versa from the functioning of the PC?

Surely its the metal case that helps in this regulation of EMI and by fitting a perspex window or perspex case will cause an adverse affect of functioning of other household appliances and the PC itself. Or is the perspex just as good at "insulating" the PC from EMI?

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I gather the way it works is similar to Faraday cages, where the EMI takes the shortest route. I couldn't say if the overall cage of the box is enough to stop interference, But I'm sure it helps.

If you really wanted to be on the safe side you would have to put a kind of perspex sheet that has a metal mesh in it like safety glass to deal with the EMI.

Also you should note that around the environment of mainstream Backbones on the internet, their entire rooms caged within cages so as to attempt to deal with interference from outside (Like mobile phone signals etc) So if you were really concerned then you should start caging your room out.

 

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Yes; if perspex is plastic (it sounds like it might be related to Lexan, which is) then it provides practically no EMI protection in and of itself. Stryderunknown is correct about the mesh as far as I know. I think that it will provide shielding for wavelengths of four times the mesh hole size and longer.

As a side note, a fully cased computer next to a ham radio set at school roduced up to something like 10dB of interference at various frequencies.

 

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So If I were to get a perspex case for my PC, the EMI would start affecting other household appliances as these type of cases dont have any metal protection. I gather that EMI isnt harmful?

 

Lets just say if you place a magnet next to a monitor you can not just discolour the pixels, but potentially in the CRT cause it to error, thats why most of the newer CRT's have a Magnetic protection "PURGE" button. (however you should find that LCD FLT's don't use the same mechanics so aren't effect)

You might also find that speakers near the computer "Hiss" or potentially have sounds occur when your drive startsup or is activated. However this can be fixed by either placing the box away from the equipment that would be effected (like on the floor), using a mesh, or placing the speakers and monitor away from the box.

Also if you have a Floppy Diskette rack next to your box, it could potentially cause the disks to fail.

 

At a guess, anything further than 3m wouldn't have a problem.

 

http://www.allproducts.com/manufacture1/kaostar/p06.html
Whats this all about? I cant make out what it means.

 

That would be a vest for people with Pace makers I would guess. Pace makers being an implanted timing device for heart beats usually placed into some people that have problems with their own system of timing. (Usually after heart attacks)

It's renouned that people with Pace Makers can't utilise some things that output Electromagnetic radiation (Like Microwaves) as it might interfer with their pace maker (You can imagine the problems with the increase of mobile phones)

So I would guess such a jacket it's to help save them from the interference to their Pace makers.