I have an anti-static-discharge mat similar to the one in this question. Like the OP in that question I doubt the mat's effectiveness, mostly because my ohmmeter measures an open circuit across small distances on it. Would I be wise to place the mat on aluminum foil and to ground the foil? Is it enough to ground the foil to the ground pin of an electrical outlet?

  • \$\begingroup\$ why do you doubt the effectiveness? (Can you pinpoint that?) \$\endgroup\$ – Marcus Müller Sep 6 '20 at 14:55
  • \$\begingroup\$ @MarcusMüller: Thank you, I updated the question with my reasoning. \$\endgroup\$ – dotancohen Sep 6 '20 at 14:57
  • \$\begingroup\$ put the foil on top of the mat \$\endgroup\$ – jsotola Sep 6 '20 at 17:18

If your mat is an dielectric, it won't allow charge to flow from its top side to its bottom side and through the metal to ground. So, if your mat is actually a proper dielectric, this won't help.

However, your testing method is incorrect: the standards for such mats require a resistance of several megaohms (over about 30 cm or so, can't fully remember) when pressing large-diameter (thing: coffee mug crossection) metal electrodes with some serious force (>20 N, IIRC) to the mat to test. Compare the cross-section of your multimeter's probe to that: no wonder it doesn't see any conductance!

You could probably emulate such tests with e.g. a small 5cm diameter puddle of soapy saltwater for each multimeter probe (or of course, ECG gel), and come barely into the region of resistances your multimeter can measure. I haven't tried that, though!

  • \$\begingroup\$ Thank you. So I understand there is no way to test the mats in a home environment. \$\endgroup\$ – dotancohen Sep 6 '20 at 15:41
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    \$\begingroup\$ Sure we do but I still get an open circuit! There's even a bit of coffee in there for good measure. \$\endgroup\$ – dotancohen Sep 6 '20 at 15:56
  • \$\begingroup\$ Nice! The coffee is a nice touch, really :) in all honesty, over this small distance, and this large contacting area, I would've expected some conductance, so maybe your mat is really isolating. I'm not in the lab today, but I'll test this method tomorrow! \$\endgroup\$ – Marcus Müller Sep 6 '20 at 15:58
  • \$\begingroup\$ Thank you Marcus! Any excuse for an experiment! \$\endgroup\$ – dotancohen Sep 6 '20 at 15:59
  • \$\begingroup\$ yea the mats are meant to give a very weak discharge path to earth ground, so that static charge doesn't accumulate on their surface. You would not want them carrying large amounts of current in a failure mode... that would be bad. \$\endgroup\$ – vicatcu Sep 6 '20 at 19:15

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