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ESD mats and grounding

  1. Nov 27, 2013 #1
    Can you claim to have ESD protection if you have just the wrist strap connected to ground and not the ESD mats on a typical workbench?

    With just the wrist strap, ESD is instantly discharged to ground. With the ESD mat, the charge is gradually discharged to ground.
     
  2. jcsd
  3. Nov 27, 2013 #2
    Wrist straps are never connected directly to ground. Typically a 1Meg ohm resistor should be in series.

    A static dissipative work surface is necessary on a typical workbench.
     
  4. Nov 27, 2013 #3
    Why exactly do you need the static dissipative work surface.
     
  5. Nov 28, 2013 #4

    davenn

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    definately not

    wrist straps DONT instantly discharge to ground ( well not in the way you are probably thinking
    as said by the_emi_guy .... they are not connected directly to ground. that would present the wearer of the strap with the potential of being electrocuted

    The wrist strap, like the mat, are high resistance to ground

    so that you and the equip you are working on are BOTH static grounded

    cheers
    Dave
     
  6. Nov 29, 2013 #5

    Averagesupernova

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    The wrist strap is always connected to ground. Usually through a resistor as has been stated. The static mat is similarly connected.
    -
    ESD mats behave a little differently than one might expect. Take your ohmmeter probes and stab them into the mat and you will be hard pressed to get a reading. But, take two wet sponges and lay on the mat a short distance apart and then stab the ohmmeter probes into the sponges. You will definitely find a low enough of an impedance to drain away ESD charges. I have found if you have a wooden surface on the bench that has gotten soiled with use makes a pretty good ESD mat all by itself. This assumes it is mounted to something that is grounded.
     
  7. Nov 29, 2013 #6
    The sponge experiment, I will definitely do.

    I guess without the mat, a regular surface might be a source for picking up static, like when you wipe it with a piece of cloth or when your sweater rubs against the surface?
     
  8. Nov 29, 2013 #7
    Another ESD related question - I have seem some tables with ESD mats wired to a metal ball at the bottom of the table, lying on the ground.
    Is the ball used as ground instead of connecting to real Earth.
     
  9. Nov 29, 2013 #8

    Averagesupernova

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    I would assume the ball contacting the floor is considered a good enough ground to protect against ESD.
     
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