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Grounding mat not working

  1. Jul 14, 2016 #1
    Overview:
    I've made a grounding mat using a piece of copper speaker wire attached to the grounding prong on a wall plug (I removed the other two prongs). The other end of my copper wire is attached to a sheet of aluminum which I set on the floor like a mat. I checked to make sure that my wall outlets are grounded before plugging it into the wall.

    I have 2 appliances which trigger my volt meter alarm. If I hold the volt meter in my right hand (away from the appliance) then touch the appliance with my left hand, the meter is once again triggered as the voltage travels through my body.

    While I'm standing on the grounded mat, I cannot trigger the meter by touching an appliance.... I thought everything was good.....and yet....

    Something seems wrong:

    -The aluminum mat itself triggers the volt meter alarm. The plug does not.

    -When I am in contact with the mat, the hand-held meter becomes about 3x more sensitive to surrounding appliances.

    -When the appliance and the mat share the same grounded power strip, the appliance registers at a lower voltage rate, and the mat registers at a higher rate (just sitting side by side)

    -When the mat triggers the voltage meter, I can stop it by touching the mat with my hand


    Is this unusual for a correctly set-up grounding mat?
    I split the speaker wire in half as demonstrated in a couple of online tutorials. The tutorials indicated that I only needed to use the copper half of the wire. Should I have left the wire intact?
    Thanks!

    PS: I could not find my regular voltage multi-meter, so I was working with a no-contact volt meter.

     
  2. jcsd
  3. Jul 14, 2016 #2

    Baluncore

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    How did you make that Cu to Al contact.
    Al can be difficult to bond electrically because of the surface layer of oxide = sapphire.
    Check the bonding by measuring the electrical resistance across the bond.
    It may be necessary to first clean the bond area and coat it with petroleum jelly or dielectric grease to prevent oxidation.
     
  4. Jul 14, 2016 #3

    marcusl

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    Baluncore's advice is sound--aluminum always develops an insulating oxide layer. Also how are you measuring voltage? Digital multimeters have such a high input impedance that they register stray potentials picked up out of the air. Essentially your body is a capacitor to stray fields. Such readings don't have practical meaning.
     
  5. Jul 14, 2016 #4
    Baluncore,
    The aluminum has a hole drilled in it. I threaded the copper wire through the hole a few times (in a sunburst pattern). I pulled the wire tightly against the aluminum and then crimped it down just be sure there was good contact. The Aluminum appears to be very clean. I wasn't sure how best to clean it, so I didn't. It is a recently purchased sheet.
    If this works nicely, I will use copper rather than aluminum, and I will solder it with a conductive solder. I was just experimenting with some less expensive materials first.
     
  6. Jul 14, 2016 #5

    Baluncore

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    That Cu-Al is probably a very poor contact. Check the resistance of that bond.
     
  7. Jul 15, 2016 #6

    davenn

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    what you have done is also very dangerous and you have left yourself open to electrocution if things go wrong

    true grounding mats ( antistatic mats) be they on the floor or on the bench top have hi resistance ( usually several Meg-Ohms)
    across their surface and to the earth pin in the wall socket

    Please use the correct mats .... I don't want to see your name in the obituaries


    Dave
     
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