# Why is there a positive body voltage when grounded, but none when not?

So after reading about earthing and earthing mats, I decided to make myself a very basic one for cheap to test the concept before jumping in with purchasing more sophisticated products.

Here's what I have:

• A grounding plug wired on the ground pin with a 2m speaker cable. (I split the 2-wire cable and only used one wire. ).
• The other end is connected to an alligator clip, which is clipped to my basic earthing mat.
• The earthing mat is a cardboard sheet with aluminum foil taped on one side with aluminum tape. The clip is connected to this tape.

Here's how I measured my body voltage and the associated readings:

• Insert black-prong of multimeter into a separate outlet ground. Other end connected to COM port on multimeter.
• Put multimeter in V AC mode. Mine only has 200V and 500V, so I picked 200V.
• Hold red-prong of multimeter in hand. Reading is 00.0 but briefly reads up to 00.2V (200mV) if I move around.
• Now, when I ground myself by stepping onto the earthing mat, the reading jumps to 00.5 (500mV) and stays there.
• A second person in the house read 00.6 (600mV).

This didn't make any sense to me. It appears that my body is drawing positive voltage either from ground or from the earthing 'mat'.

I also tried connecting the black-prong of the multimeter to the alligator-clip on the earthing mat and also got the same result.

Can someone please explain what is going on? Did I make a poor earthing mat or is the earthing "mat" acting as an antenna and defeating the very purpose of grounding?

How is it that all other DIY earthers get the exactly opposite result?

• How far apart are the outlet used to ground the mat and the outlet used to connect the black prong of the meter? Are they two outlets in the same box in the wall, or across the room from each other? May 8 '19 at 3:41
• The two grounds are about 5 feet apart in different boxes, same room. May 8 '19 at 11:39

I purchased a cheap multi-meter which also have only 200 and 500 volts ac (alternating current) settings. These settings are much, much too high to measure the low body voltages of more or less 1 volt to 3 volts.

But your multi-meter will have very low dc (direct current) settings which you can use, if you were to convert the ac of your body voltage to dc voltage.

Connect a diode in series with your/the +ve of the multi-meter, which will convert the ac to dc which is then measured on the 200 millivolt dc scale/setting.

+ of multi-meter}...................k(diode)..........connected to earth peg.
-ve of multi-meter....................................probe in hand


Your multi-meter will now measure very low body voltage/s in dc, instead of (as a function of) ac.

A diode can be purchased from your radio repair shop. I use a (1N4007) diode.

it is not straightforward measuring such things. A schematic of what you have done would help the discussion. Please, take into account the following points:

1. as said by @Roberto , the scale of the multimeter must be selected to match the expected value, otherwise reading will be inaccurate (note: however, it should be proportionally correct, that is an increase of reading is an increase of reading)
2. you pick up usually electric and magnetic field from your AC distribution and appliances, but also from mother Earth (static field); if you move you get also the Earth's contribution in AC terms.
3. these picked up signals are read especially well if you have a high input impedance instrument (e.g. a multimeter) or the oscilloscope probe (10 Mohm); any low/medium value impedance will reduce (kill) such readings; to avoid floating readings of this kind during electrical safety checks of touch voltage, the body of the person touching is simulated with 1 kohm (or 1.5 kohm) (stds E 50122-1, EN 50522).
4. for electrical safety, grounding provided by an electrode in the soil (or a set of) is measured using another electrode in the soil, far away, i.e. 5 times the largest dimension of the earthing system to measure (stds IEEE Std. 81, BS 7430).