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Over sensitive non-contact voltage indicator or normal behaviour?

Discussion in 'Electrics UK' started by eveares, 26 Dec 2020.

  1. eveares

    eveares

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    Is my Di-Log PL107N Voltage Indicator over sensitive or are all similar non contact voltage indicators/detectors what rely on the principle of capacitive coupling going to detect unwanted sources and give false positives like featured in the video?



    Regards: Elliott.
     
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  3. bernardgreen

    bernardgreen

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    The hand held no contact sensor illuminates if the voltage difference between the sensors tip and the hand of the person holding the handle is more than about 90 volts.

    The circuit is normally completed via a capacitive connection between the person's body and earth.

    A person on a wooden floor far from any earthed item will not have enough capacitive coupling to ground for the current necessary for the sensor to indicate Live when the tip is close to a Live conductor

    If the person is close to a switch drop wire their body could be more capacitively coupled to that Live potential than to earth. In this situation the sensor would NOT activate when the tip was close to a Live conductor and may well indicate a false indication of Live when close to a neutral or earthed conductor.

    THEY ARE NOT A SAFE WAY TO TEST FOR LIVE. or the absence of Live before working on the circuit
     
  4. crystal ball

    crystal ball

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  5. ericmark

    ericmark

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    Normally test by rubbing on cloths, rather poor testers.
     
  6. eveares

    eveares

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    I am well aware of that, I have a GS38 compliant voltage tester for that.

    I am also aware I can trigger it by rubbing it on my clothes by creating static electricity.

    I was just a bit surprised that it was detecting when it was so far away from any sources of electricity and was standing still on my wooden floor.
     
  7. Harry Bloomfield

    Harry Bloomfield

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    Actually, they do not work that way at all. They do not work in the same way as a neon screwdriver, rather they work by detecting the AC field around a live part, no earth required at all.

    The Volt Stick is an absolutely brilliant bit of kit, in the proper hands that know how to use one and its limitations.

    That does puzzle me and I have no suggestions - it needs some further thought.

    [EDIT] My best guess is that shelf unit is very slightly conductive and there is some capacitive coupling between the unit and something electrical placed on the unit [1].

    [1] Double insulated items often have metal casings, or bases. If you are grounded, you can sometimes feel a slight tingle when touching such items and a volt stick will light up if placed near the item. That metal, capacitively coupled to your shelf unit, might be enough to trigger the volt stick.
     
    Last edited: 27 Dec 2020
  8. bernardgreen

    bernardgreen

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    Voltage detection not electromagnetic field detection
     
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