ESD article comments

Discussion in 'Feedback and Suggestions' started by davebee, Mar 14, 2009.

  1. davebee

    Thread Starter Well-Known Member

    Oct 22, 2008
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    I have a few minor edits to suggest for the ESD article

    http:// www.allaboutcircuits.com/vol_3/chpt_9/1.html

    In a couple of places, the current that may be associated with static electricity is treated a little too casually, in my opinion, as in the quotes "there is no current capacity behind it. " and "Static electricity is voltage with no real current".

    Static electricity may discharge in a wide range of currents, both small and large (think lightning) so I think that low current when the stored charge flows is not a consistant property of static electricity.

    Is this quote from the article really true: "pulling tape off a dispenser can generate millions of volts"? I'd be surprised. Most articles I've casually browsed suggest that a million volts will spark at least several feet! I can't imagine a tape dispenser generating this much voltage.

    And about this quote "continuously bleeding off this voltage is needed." I would say that what is bled off is charge. Voltage is a property of this charge, and while it's true that bleeding off charge results in bleeding off voltage, I think that charge is more fundamental thing.
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    Pulling tape off a reel in a vacuum will generate x-rays, this published in a recent article published by the site http://www.physorg.com/. The number has been stated in more than one source concerning ESD control. Transparent tape is an excellent insulator, as well as an excellent static electricity generator (the two aren't the same).

    You have to look at the focus of the article, which is ESD control on a work station handling ESD components. Lightening is an ESD event (which was pointed out in the article), but doesn't really apply in context of what the intent of the article was.

    Charge in this case is measured in voltage. At the end of the day, it is voltage that counts. During a ESD event this voltage translates into current, but it is the voltage that ionizes the air and creates the initial discharge.
     
  3. Wendy

    Moderator

    Mar 24, 2008
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  4. davebee

    Thread Starter Well-Known Member

    Oct 22, 2008
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    That's an amazing tape phenenomon!

    But still, as I remember from repairing color TV sets back when they had big glass tubes, it only takes about 30 kV to generate a harmful amount of X-rays.

    It's really the electric field, as measured in the volts per meter, not the voltage itself, that ionizes air and causes a discharge. I found a nice description at this link -

    http://www.myelectricengine.com/info/plasma-physics/plasma-physics.html

    I'm only including this link out of general interest; I understand that it goes into much more detail than the article intended to go.
     
  5. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    Don't worry about the link.

    Never Stop Learning or Building!
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    Tell you what, you bring up some valid points about the magnitude of voltages. I'm going to do a bit more research and get back with you.
     
  7. Wendy

    Moderator

    Mar 24, 2008
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    OK, this fell through cracks, but I did do the research. Second paragraph...

    Should read...

    Side note: I tried very hard to pin down the voltage generated when scotch tape generates x-rays in a vacuum with no luck. The most comprehensive article was found here. Apparently it takes 15keV to do this, my understanding of physics in this area is a bit shaky, but I don't think this translates to 15KV.

    I would put the criticism as verified.
     
    Last edited: Feb 14, 2010
  8. Wendy

    Moderator

    Mar 24, 2008
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    7th Paragraph down...

    Should be...

     
  9. Dcrunkilton

    E-book Co-ordinator

    Jul 31, 2004
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    Bill,

    I have entered the change at ibiblio.

    Dennis
     
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