Hi,
I was looking into ghost voltages on open neutrals and unused adjacent wiring when using high impedance multi-meters. I looked at a couple of articles but its still not clear to me. I set up a basic experiment using a transformer and a couple of multi-meters ( attached pic ). In the fig 1, I can see how the primary winding capacitively couples to the secondary and when I touch the probe of the multi-meter, I complete the circuit to earth and this accounts for the 3uA on the meter ( this is one of the articles I looked at on compensating currents ).
In fig 2, when I take my hand off the meter probe, where is the completed circuit now, is there further capacitive coupling from this probe to the earth itself ?

David

 

Pics

 

 

A transformer couples electromagnetically (field), as it is an inductor, not so much capacitively (although capacitance in the windings can exist- the idea is that these cancel due to the wrapping and interraction of cores).

However, _YOU_ act as a large capacitance on the ground-side, and hence you have a charge difference.

This may help you learn something about transformers (if you don't know):

Title: Understanding Basic Electronics, 1st Ed.
Publisher: The American Radio Relay League
ISBN: 0-87259-398-3

 

...is there further capacitive coupling from this probe to the earth itself ?

Yes, I believe air can provide a small amount of coupling.