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"Anti static" mats

Discussion in 'Electronic Design' started by Nemo, Feb 4, 2013.

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  1. Nemo

    Nemo Guest

    I got a "static dissipative" mat and measured its resistance between two
    points. On the underside, which is black, it's just kilohms. But on the
    top surface it's too high to measure - I checked the DVM with a 50Mohm
    resistor and it measured 51M, so I trust the DVM. I asked the
    manufacturer how this insulating surface is meant to prevent static
    building up and damaging components... tellingly, no answer was
    forthcoming, "we'll, uh, get back to you".

    I reckon it is possible that these mats work on the principle that
    static flows over surfaces, so it leaks round the edges to the
    conductive layer below. I can quite imagine this being worked out by
    some genius in the 1920s and no one remembers why it works any more:
    "we've always made them that way"; there seems to be an increasing
    number of technologies where the fundamental knowledge is lost. But
    here, the top surface does really seem to be basically a plastic
    insulator. I don't have an electrometer or other handy device to see if
    it holds charge, can anyone reassure me these mats really do work? Or a
    test to prove they do not, like levitating paper after rubbing the mat
    to build up a charge?

    TIA
     
  2. Ecnerwal

    Ecnerwal Guest

    They are quite well understood, if not by the person in charge of
    fielding phone calls.

    The details are easy to find. As best I recall from when I bought mine
    and actually looked this stuff up (which I'm not going to repeat - you
    can do it yourself) there are problems with using the highly conductive
    side up due to too-quickly discharging things. The more-resistive side
    conducts through to the more conductive side at a moderate but adequate
    rate - the more conductive side keeps everything equipotential.
     
  3. Nemo

    Nemo Guest

    Thanks. I'll have a go at the electrometer but the responses are already
    reassuring.

    Nemo
     
  4. gregz

    gregz Guest

    I would use an old VTVM. any deflection can easily be seen. I don't
    remember trying this test. I just believed.

    Greg
     
  5. There's a 1 meg ohm resistor in the grounding strap that I put one
    when working on sensitive (expensive) stuff.

    (go measure your's)

    George H.
     
  6. The cleaner is $122 for a spray bottle. What's so special?

    I don't see any resistance specified on that site.

    That site has mats that are $10/sq ft, but most are $100/sq ft with no
    specifics about the difference.
     
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