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EMI Shielding Gaskets

  1. Jul 30, 2007 #1
    Hello everyone,
    Can anybody tell me that, actually what is the main function of EMI shielding gaskets?And i would also like to know the applications of EMI shielding gaskets.
    Best regards
     
  2. jcsd
  3. Jul 30, 2007 #2

    xez

    User Avatar

    The main function is to reduce electromagnetic
    radiation noise from electronics causing undesirably
    high electromagnetic noise levels outside of the
    equipment chassis.

    Of course it also works in reverse and
    keeps some of the noise from outside from entering the
    chassis, but usually that is not the problem.

    It functions by keeping a conductive contact around the
    seams and gaps in a chassis and around areas where
    panels or other openings / bezels break the solidity of
    the chassis' conductive RF shielding panels. By sealing
    the cracks and holes with conductive pathways it better
    keeps the electromagnetic waves from being able to exit from those areas.

    Usually it is used because equipment might not meet
    governmental regulations for EMC / EMI if it were not
    used.
     
  4. Jul 30, 2007 #3
    Thank you xez for the above information.

    I saw some EMI chambers, which are used in pcb,s and in other electronic circuits and they are made up of tin-steel, and i think it is a conductable material, so i am quite confuse with the concept.
    And i also have seen some more gaskets which are made up of some flexible material, so can you please tell me that in which type of equipments are they used.
    best regards!
     
  5. Jul 30, 2007 #4

    berkeman

    User Avatar

    Staff: Mentor

    Generally with EMI shielding you are trying to form as good of a Faraday cage as possible around the noisy (or sensitive) circuitry, and then you would also filter the signals that pass in and out of the shielded volume. Since doors and other access openings compromise how "good" of a Faraday cage you can have, gasketing is used to help bridge the conductivity across the seams of the openings when the doors are closed. To be an effective conductive bridge, the gasketing needs to be flexible and conductive.

    Here is a good page about shielding:

    http://www.emi-shielding.net/info/emi-shielding/
     
  6. Jul 30, 2007 #5
    hello Berkeman,
    thank you very much for your concern.
    I am getting what you are saying but I am still unable to imagine actually where these faraday cages are used. I just want to know the name of equipments.
    I am also aware about the concept of the gasket, i know gaskets are used for the purpose of sealing. But i also have studied that EMI gaskets are used for insulating two conducting plates in various electronic equipments.
    and what you are saying is that these gasket should be flexible and conductive. i am getting the word flexible but about conductive, i think i am quite confused. so can you please clear these things.
     
  7. Jul 30, 2007 #6

    berkeman

    User Avatar

    Staff: Mentor

    I don't think you would refer to insulating gaskets as "EMI" gaskets. They probably have some vibration/shock purpose if they are truly insulating.

    I'll give you a very practical example of EMI shielding and gasketing. Take your desktop PC apart a bit -- as you remove the outside cover, you will see that the PC is basically a metal (or metalized) box, with some spring fingers or something similar making the contacts between the cover and the internal metal structures. This is done in order to help minimize the amount of RF "EMI" noise that can radiate out of the PC and cause harmful interference with nearby radio and TV broadcast receivers.

    And in the other direction, if you've ever taken apart a TV (careful!), or an FM radio receiver, or a spectrum analyzer, or anything that deals with the amplification and processing of very small signals, then you've seen areas in those instruments where little metal boxes cover various parts of the circuitry. This is done to keep outside RF noise from getting into the small signal circuitry, so that it does not interfere with the fidelity of that signal. The inputs and outputs from these boxes are filtered, and you can often see the filters at the feedthroughs in the walls of the boxes.
     
  8. Jul 30, 2007 #7
    Thak you very much berkeman,
    Now i understand the concept.
    i would like to thank you once again for the example that you have given above.
     
  9. Dec 20, 2007 #8
    If you want to know more about EMI!

    If you want to know more about EMI shielding you can take a look at www.hollandshielding.com.

    You can also request a sample package and catalog for free so that you can get to know more about it.
     
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