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Question about shielding

Discussion in 'Electronic Design' started by Nemo, Apr 3, 2009.

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  1. Nemo

    Nemo Guest

    I know some things about how to keep RF and ESD out of a circuit... and
    I'm confused about some others.

    I understand from this thread:
    "Ferrite on audio leads passing near PC?"
    that for low frequencies it is sometimes advantageous to only connect
    the shield of a cable at one end. And connect different boxes' grounds
    in a star formation. But when is it a good idea to connect it at both?

    Up to now I'd thought it was always best to connect the shield at BOTH
    ends unless there were significant ground loops, to get a Faraday cage
    which keeps out RF and, if the shield is good enough, probably ESD too.
    Also I'd heard that multiple points of grounding of a PCB helps to avoid
    ringing.

    Perhaps I am getting confused between signals going down a single core
    coax cable and multicore shielded cable? Or does it just depend on the
    particular installation, geometry, types of signal, strength of
    interfering signal?

    Thanks in advance for any clarification,
     
  2. Eeyore

    Eeyore Guest

    Quite different things.
    But it's a kludge and VERY bad practice. If you MUST do it, connect the
    shield at the sending end and connect it at the receiving end via an 10nF
    low-loss capacitor.

    If you want to learn about real EMC you need a damn good book or a mentor. I
    was lucky enough to have the latter and a damn good one at that.

    Graham
     
  3. Guest

    Do you recall the reason for grounding the driven end?
     
  4. krw

    krw Guest

    There is only one? Though turntables (the driven end) tend to not
    have the shields connected. They're not likely to drive more than one
    (pre)amp either.
     
  5. Guest

    OK then , how about giving all the reasons why the driven end is
    grounded.

    My recollection, and I will admit I haven't research ground loops in a
    long time, is you picked the driven end because it is likely one
    driver would go to many inputs. But if you just had one driver and one
    input, it really didn't matter. The key was to not have current
    flowing in the shield.

    I never heard of the AC ground trick.
     
  6. krw

    krw Guest

    I did. There is only one driven end. There may be more than one
    sink. Grounding one end, and standardizing on which end, makes it
    more likely that there is one and only one grounded end.
    Why don't you read what I wrote? Illiterate?
    Amazing.
     
  7. Nemo

    Nemo Guest

    Thank you for the responses,
     
  8. Guest

    KRW uttered:
    "There is only one?"

    Clearly, this implies you know more that one reason to ground the
    driven end. So lets. hear your list. Maybe you should cut down on your
    drug intake.
     
  9. krw

    krw Guest


    Clearly you are illiterate.

    M: "Do you recall the reason for grounding the driven end?"
    K: There is only one?

    i.e. there is only one driven end.
    Don't do drugs. Maybe you should pull your head out of your ass.
     
  10. Guest

    I gather you are either a **** head, English is your second language,
    or a combination of both. Clearly "there is only one" refers to there
    is only one reason.
     
  11. krw

    krw Guest

    Clearly, you're illiterate.
     
  12. Guest

    As if I want to be on your white-list. Your loss, my gain.
     
  13. Guest

    Let's get real here. You have no knowledge of the subject at hand,
    hence you start these insult threads to cover up your ignorance. I'm
    here to both help and learn, but really have no use for your useless
    bullshit.
     
  14. krw

    krw Guest

    No, let's be clear here. You simply cannot read. Go back to grade
    school. Come back when you grow up.
     
  15. krw

    krw Guest

    You prove otherwise with every post.
     

  16. Pompous? PKB ALERT!!!
     
  17. Eeyore

    Eeyore Guest

    It returns capactive currents to the driver.

    Graham
     
  18. Eeyore

    Eeyore Guest

    All too true.

    Also true. I'd like to see hi-fi adopt 'balanced' connections. It costs so
    little to implement these days and solves so many problems.

    If anyone's interested I could tell a very interesting story about how well
    balanced audio works.

    Graham
     
  19. Guest

    I'm all ears. ;-)

    The nice thing is high quality connectors already exist for balanced
    signals.

    Fully differential circuits would make analog leap frog filter designs
    a snap since the inversion is already present.
     
  20. Guest

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