EMI levels from PC's?

[BossNoodleKaboodle]

I've been wondering what the actual EMI levels produced by a PC would be. Some cases say "fully EMI shielded" and others have a big plastic window on the side, so I'm wondering just what sort of emissions are given off and how much.

 

[deltron3030]

that's a good question but unfotunatly i cant answer it. Although i have wondered about it myself. i am thinking about investing in a deionizer which is supposed to make you feel alot better by neutralizing positive or negative ions,i forget which way it works but apparantly alot of the "bad" ions are given out by electricial equipment and judging my most of us here were probably sitting in front of a whole heap of ion producing devices. apparantly standing at the bottom of a waterfall makes you fell really good because of the good ions produced,just like when your in the shower!

 

[templarknightx]

To add to the first question. Would it be enough to damage anything if you, say, put a CRT next to your plexi-windowed case?

 

[ryuji]

emi != damage emi=undesired operation, with accordance to fcc rules every device needs to be able to cope with emi

 

[liquidtrance123]

not sure if this puts things into perspective but i work at a hospital and we have normal HP boxes sitting right outside/near the patient rooms, where the heart monitors and shit are at. No problems at all. However we do restrict Wireless access to a specific Band of Cisco brand equipment in the patient buildings. And of course cell phones are definately not allowed.

 

[Elledan]

The problem with PCs and EMI lies not so much in that they radiate a lot of EMI, but that they're sensitive to EMI from external sources.

This excludes the PSU, of course, which is so noisy (from an EMI perspective), that it has been put inside its own Faraday cage.

 

[ryuji]

The problem with PCs and EMI lies not so much in that they radiate a lot of EMI, but that they're sensitive to EMI from external sources.

This excludes the PSU, of course, which is so noisy (from an EMI perspective), that it has been put inside its own Faraday cage.

untill you cut a window into it

 

[qdemn7]

I've been wondering what the actual EMI levels produced by a PC would be. Some cases say "fully EMI shielded" and others have a big plastic window on the side, so I'm wondering just what sort of emissions are given off and how much.

Just a minute, let me ask my other head.......

 

[Ballz2TheWallz]

do imacs worry about EMI?cmon they are build into a case with the crt adn pc components,my school has ones like 10yrs old going strong today

 

[Elledan]

do imacs worry about EMI?cmon they are build into a case with the crt adn pc components,my school has ones like 10yrs old going strong today

CRTs produce a lot of EMI, but they're shielded. Just open a CRT (make sure it's turned off ) and notice the (grounded) metal cover surrounding the tube.

 

[Elledan]

untill you cut a window into it

Beauty requires sacrifices

 

[Apallohadas]

Just looking for clarification on the original question.

I've been wondering what the actual EMI levels produced by a PC would be.

Electro-Magnetic Interference.

How much is generated by a PC? Unless that PC is being used as some type of active transmitter (like a cellphone or other device who's purpose is to intentionally give *off* a signal,) probably not much. A wireless router would be an example of an active transmitter. But even in a cellphone, the range of EMI near, say medical devices is only a yard.

And regarding medical devices, there isn't an FDA or FCC ban on cellphones, however some hospitals have taken the urban myth to heart (to play it safe, can't blame them.) link Properly shielded equipment is the answer in a world where more and more people are carrying PDAs, Cellphones, Blackberries linking them to the devil, and Tomaguchi pets.

Back to the original point, I was momentarily distracted by a dustbunny, anything using electricity will generate some level of EMI right? But your PS is shielded, your cables are shielded, your case (to some extent, minus giant windows) acts as a shield. Unless gramma is running her wheelchair over your computer, she probably won't go swerving out of control.

Ever have your cellphone next to a CRT, and when you get a call, or the cell links up with the provider to test the network, you see wavey lines or blurring? Well, the cell has a field strength of about 3-5 V/m at 1 m. Low voltage at close range, and only for a moment.

So, we now know that your computer is shielded, as is your monitor, that EMI isn't necessarily dangerous (unless you're gramma running over an open computer or monitor, and in that case EMI is the least of your lunacy worries), and that the dustbunny in my office looks like Jesus Christ.

Bidding opens at 15K.

 

[Squalish]

Since it's several pages, here:
http://www.google.com/search?hl=en&lr=&c2coff=1&q=+site:www.dansdata.com+RFI&btnG=Search
Dan's one of the best technical writers I've read

I always hated the word "electromagnetic radiation," though. It can describe anything from fluxing magnetic fields to beta radiation (electrons) to any kind of photon waves (gamma radiation, radio waves, visible light, anything).

Short answer:

No, it produces negligible amounts of magnetic fields (produced intentionally in inductors, or wires wound repeatedly around a shape, or transformers, which are field-coupled inductors[you can find most of the major ones in your power supply]).

A computer does produce a significant, but not really important, amount of radio wave radiation - enough to MAYBE interfere with the TV/radio in the same room, but not much more. Even so, cases with windows aren't sellable in some countries without a protective cover, as they violate RFI standards since the faraday cage [shield] of the grounded case is violated.

 

[corebreach]

Even so, cases with windows aren't sellable in some countries without a protective cover, as they violate RFI standards since the faraday cage [shield] of the grounded case is violated.

Whoever put two and two together and banned the sale of cases with windows is my hero.