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One of my family members recently sent me a link to this Better Earthing website about the alternative therapy of "earthing".

The site includes which includes a video that claims to show "excess AC voltage" and how to reduce it with their product. (The video on YouTube if you don't want to visit the site itself: https://www.youtube.com/watch?v=pJJNQWKXUpE)

I'm curious about what physical or electrical effect is actually being demonstrated in the video.

The description on the video says:

Peter demonstrates how to use an autorange multimeter to measure the conductivity of [the earthing] products. You'll see a 100 times reduction in excess AC voltage in Peter's body when he starts Earthing.

The setup:

The setup in the video shows:

  • a multimeter connected to ground (via the ground pin of a power outlet, no connections to the live wires)
  • the multimeter set to read "AC voltage"
  • a person touching the test lead to the multimeter
    • there is no current source in the circuit - i.e. no connection to AC power source at the wall socket

They then taking readings from the multimeter in a couple of sitations:

  • A. just holding the test lead
  • B. holding the test lead whilst holding a hand over a light switch
  • C. holding the test lead whilst sitting or lying on an earthing mat, which is also connected to ground

The video:

I've transcribed what he says at the different points of the video:

  • A. 1:17 "I've got 3.1 volts of AC voltage in my body"
  • B. 1:20 "If I put my hand [on] this light switch I'm ... up over 10 volts, I'm up to 11. So I've now got 11 volts of voltage in my body that I'm picking up from live wires."
  • C. 2:08 "I'm sitting directly on [the earthing bed sheet] and I've just gone down 2.1 [volts], to one third of a volt from about 3 volts. So that's about a 25-, almost 30-fold, decrease"
    • the measurement seems to go down to a reading of 0.13V

I only have a very basic understanding of electronics/electricity, but it doesn't make sense to me what the multimeter could be measuring without a flow of electrons to measure as current.

Questions:

So my question is pretty much: what is actually going on in this video?

  • In situation A (just holding the lead of the multimeter) what is the multimeter measuring?
    • is it any sort of meaningful measurement if there is no electricity source?
    • is it even considered a circuit if a person is just connected to ground?
    • if there is no source or load in the circuit then what flow of current is the multimeter reading as the AC voltage?
  • In situation B, how might holding the hand over a light switch cause the reading to increase?
  • In situation C, what is happening to cause the voltage reading to decrease?
    • the circuit ground-to-ground connection with a person and multimeter in between - how is that different to the "circuit" in situation A?

This question seems to be asking a similar question. However, there isn't a clear answer that I could understand and the experience of the question-asker seemed to be the opposite of what was being shown in this video (unless I'm mistaken?).

Thanks!


Previous discussin of earthing in the Skeptics community:

Not sure if it helps, but the multimeter being used is the Digitech QM1529.

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  • \$\begingroup\$ What they said. | Summary; probably mainly capacitive coupling. Hand on switch plate increases this. | Earth mat causes high capacitance to ground. The capacitor to mains and the ground cap form a voltage divider and yields far less body voltage. || MUCH research has been done on this over decades. There is no reason to think that this is worth being concerned about. While just maybe there are minor second order effects they are so buried in the noise (of all sorts) of everyday life as to be of utterly no effect. \$\endgroup\$
    – Russell McMahon
    Jul 30 at 12:48
  • \$\begingroup\$ Equally valid argument against this product (that is, both true and misapplicable): When you ground (earth) something that was previously floating at some AC voltage (indeed induced by whatever's around it), you end up with some non-zero current to keep that earth-potential. \$\endgroup\$
    – AaronD
    Jul 30 at 20:00
  • \$\begingroup\$ Very roughly, you have an AC circuit with a capacitor and a resistor in series. The cap is between you and the source (AC wiring in this case), and has a ridiculously low value but still there. The resistor is you. Now run a circuit analysis on that...and get out the popcorn for the nutcases who are going to take off and run with it! ("it's the current that kills, you know...", completely disregarding the negligible magnitude as they always do) \$\endgroup\$
    – AaronD
    Jul 30 at 20:00
  • \$\begingroup\$ Q: "What is actually being measured in this video ..." A: Gullibility. \$\endgroup\$
    – Transistor
    Jul 31 at 17:15
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TL;DR; Nothing in that video is measuring anything particularly interesting, beyond the normal magnetic fields produced by mains wiring. It's nicely demonstrating how the live wire detector wands work (sticks that glow when near a live wire).

There is no "excess voltage in your body" to be concerned about. The video was made soley to extract money out of people by tricking them into buying a useless product.


So my question is pretty much: what is actually going on in this video?

  • In situation A (just holding the lead of the multimeter) what is the multimeter measuring?

A mixture of capacitive coupling, radiative pickup (person acting like giant antenna), and inductive coupling between the earth cable in the socket and the live cable that runs along side it for a long distance.

  • is it any sort of meaningful measurement if there is no electricity source?

I suppose it depends on what you mean by meaningful. You're not measuring "excess voltage in the body", but largely the voltage fluctuations of the earth wire in the socket.

  • is it even considered a circuit if a person is just connected to ground?

The person is capacitively and magnetically coupled to other things, just very weakly. Because the fields are weak, the currents involved are tiny.

  • if there is no source or load in the circuit then what flow of current is the multimeter reading as the AC voltage?

The source of the voltage reading is the mains. The load is the mains wiring and to a tiny extent you.

  • In situation B, how might holding the hand over a light switch cause the reading to increase?

Touching the light switch is effectively forms a large ground loop between the socket, whatever cabling is involved, you, and back to the multimeter.

This has increased the amount of inductive coupling because you are now measuring a much longer length of earth wire - you've now got a path which runs from the socket back to the consumer unit (or wherever the earth wire goes), then back from the CU to the light switch. This might now be the entire length of your house for example.

  • In situation C, what is happening to cause the voltage reading to decrease?
    • the circuit ground-to-ground connection with a person and multimeter in between - how is that different to the "circuit" in situation A?

By sitting on the earthing mat, you are effectively shorting out the antenna affect back through the map - effectively like connecting the two ends of the probe together.

The mats act to form an equipotential region, which is only of any use if you are handling sensitive electronics - ESD mats are common in many electronics manufacturing facilities and testing labs.

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  • \$\begingroup\$ Note that many of the things you are talking about are how touch lamps work. \$\endgroup\$ Jul 31 at 2:34
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  1. the human body contains a lot of (salty) water.

  2. salty water is an electric conductor, not a good conductor but a conductor none the less.

  3. Modern houses have mains wires in the walls and all cables connected to the mains sockets of the house will also carry mains voltage. These wires are also conductors.

  4. Two conductors always have a certain capacitance between them. A capacitance can conduct AC currents.

  5. So a capacitance exists between a human body and its surroundings which in a house is mainly the cables carrying AC mains voltage.

  6. This capacitance increases as the distance decreases, that can result in a higher voltage .

  7. As the mains voltage is AC (not DC) this capacitance will conduct some of the AC mains to your body. With a sensitive meter (voltage or current) it is possible to measure this voltage.

  8. Flipping a switch can mean connecting a wire to neutral instead of phase. The neutral wire will usually carry a much lower voltage than the phase wire.

  9. These currents and voltages are too low to be dangerous or have any effect at all on the human body.

  10. when measuring a voltage or current, one always needs to connect between two points. Often voltages are measured relative to a grounding on earth point which we then define as being 0 V. I write define as I could measure your ground relative to my ground and there could still be a voltage. And that's OK as the grounding is just a reference point.

Be wary of non-engineers "explaining" the behavior of mains AC coupling and measuring voltages as, when you don't have the background knowledge I describe above, it seems "magic". Yet with the correct knowledge the effects one sees are logical and make perfect sense.

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  • \$\begingroup\$ Which countries/regions use switching (in building wiring) that connects to null (US English "neutral")? \$\endgroup\$
    – Theodore
    Jul 30 at 13:43
  • \$\begingroup\$ @Theodore I don't know about what you ask. I do know that in the EU I can buy a lamp with a switch in the cord, for example: Ikea INGARED. The plug on that cord can be inserted in 2 ways into the mains socket. So there's a 50% chance that I will be switching the neutral when switching the lamp on/off. \$\endgroup\$ Jul 30 at 20:09
  • \$\begingroup\$ @Bimpelrekkie: Don't those appliance switches normally switch off both live and neutral, precisely because one can't be sure which is which if the plug is non-polarized? \$\endgroup\$ Jul 31 at 10:44
  • \$\begingroup\$ @IlmariKaronen Not in any of these cable switches that I have seen, they're all single pole. It is not actually an issue as you would have to take out the lightbulb to be able to touch the live metal parts. \$\endgroup\$ Jul 31 at 12:05
  • \$\begingroup\$ @Bimpelrekkie isn't that exactly the issue though? People generally assume that if the light is switched off, it's safe to replace the bulb, where you may accidentally touch the metal parts. Now, I'm not sure if that assumption is actually correct, but if not, I suppose my parents should have cautioned me more on this than they already did. \$\endgroup\$ Aug 8 at 2:18
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Well, since humans are basically meatbags with conductive saltwater in them, essentially humans are conductors just like wires, but just not very good wires.

Now, you are a conductor and you are insulated from your surroundings, i.e. not touching anything conductive. Electric wiring is also a conductor that has insulation. OK, what do you get if you have two conductors that are insulated nearby each others? A capacitor!

So the video demonstated that there is capacitive coupling between a human body and AC mains live wire which is usually referenced to earth/ground potential, so potential of human body also has AC voltage coupled to it when measured agains AC neutral or earth/ground. And to no surprise, if the human body is connected to earth/ground, the potential difference will be 0V compared to earth/ground, since the capacitively coupled charge flows through you to earth/ground as current to keep your potential at 0V.

And since humans are such bad conductors, typically approximated as 1500 ohms, the voltage will not be exactly 0V, but very much less when touching a grounded object than not touching a grounded object.

The capacitance of humans is approximated as about 100pF, so impedance at mains frequency is about 25 to 30 megaohms.

Comparing that to the multimeter, it most likely has 10 megaohms of input impedance.

So that's the facts what happens.

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What's actually being measured is the voltage on a capacitive divider, formed by the mains conductors in the light switch, and the conducting bag of electrolytes that is the human body.

Without earthing, the division ratio is one thing, and with earthing, the division ratio is much lower. So you will read different voltages in the two cases.

It's a real effect, just totally irrelevant to health. You might as well shine a light on somebody, notice that they are now much easier to see, and start selling high-priced illumination on the strength of that. Now I come to think of it, they do advertise high-priced spot illumination in the back of my newspaper.

Earthing mats do exist for the very good reason that when charges build up on non-earthed engineer bodies, tools or equipment, they can damage the sensitive components that they are working on. All professional and many amateur engineers use an earthing system at their place of work, an earthed mat on their bench, and an earthing strap to their body.

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This is nonsense as we know it is energy absorbed that matters not this low voltage. In this case there is no energy absorbed.

If anyone has touched a 10Meg scope probe before ungrounded, they may see more than 50V until you touch the scope or any gnd with a fingertip that is about 100 pf and ~ 1Mohm or less.

For line voltage Fields this is a natural phenomena for the body capacitance to act as an antenna. The energy is almost unmeasurable and so far below safe limits, this is a joke. Your body also makes a good little antenna for AM radio signals but energy absorption increases with frequency , yet radio signals are in the xx uV range, so there is nothing to worry about consumer E field voltages, unless you actually touch it and are grounded.

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