Should I attached metal chassis of the filtered powerline module directly to the Faraday cage?

Discussion in 'General Electronics Chat' started by Dong-gyu Jang, Feb 21, 2016.

  1. Dong-gyu Jang

    Thread Starter Member

    Jun 26, 2015
    100
    4
    Hello.

    I'm using AC power entry module filter (http://www.mouser.com/Search/Produc...irtualkey69300000virtualkey693-DD12.4111.1111, DD12.4111.1111, Schurter) to construct the Faraday cage to protect circuit against strong EM wave during gas discharge experiment.

    So far, the module is inserted to the cage with insulator such that ground of the module (so signal ground of the circuit) is not directly connected to the Faraday cage as intended for the circuit not to be affected by possible fluctuated voltage of the cage.

    However, I read some article which seems suggest that the signal reference of the circuit and corresponding shield are to be at the same ground. Yeah maybe in this scheme, voltage of the cage and circuit's ground are the same so no current can induces between them but...Is it really good idea for strong EMI environment? If so, why? My vision is shaking between original thought and this...new finding.

    Please give me clear view of shielding.

    Thanks!
     
  2. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    5,005
    745
    A Faraday cage requires that it be connected to the mains earth supply to prevent RF radiation from penetration to the outside world.
     
  3. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,546
    1,252
    Yes, connect the power line filter ground to the chassis or cage. In this way the metal can of the filter helps to cover the hole caused by the plastic power connector.

    ak
     
  4. Dong-gyu Jang

    Thread Starter Member

    Jun 26, 2015
    100
    4
    Hello.

    The main earth supply means powerline to the circuit to be protected? Does it mean The Faraday cage and the powerline filter should share the same ground?
     
  5. Dong-gyu Jang

    Thread Starter Member

    Jun 26, 2015
    100
    4
    I see. The direct metal contact is necessary to minimize hole.

    Then..what about coaxial cable adapter? I'm using coaxial cable (BNC) to communicate the circuit to the other instrument through the cage and currently isolation BNC adapters (http://www.mouser.com/Search/ProductDetail.aspx?R=3846virtualkey56520000virtualkey565-3846, 3846, Pomona Electronics) are used. This one has insulation thus no direct contact from this to the cage but it seems you suggests fully contact for all other components.
     
  6. Picbuster

    Member

    Dec 2, 2013
    376
    50
    This may answer some of your questions;
    http://www.elmac.co.uk/meast_t.htm
    http://www.thomasnet.com/articles/automation-electronics/effective-emi-shielding
     
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