Confusing odd situation!

[JohnW2]

I've not used a voltstick myself but seen a few used and read the instructions for one (when I considered getting one) and that gave instructions to hold just the end to 'provide the earth' that term was used several times. seeing different people using the same voltstick I've seen differing responses, ie one found a cable to be live and the other wasn't so sure.

I believe that there are at least two types of 'electronic voltage testers around'. Some (more common, and fairly cheap) are little more than an 'electronic' version of a neon screwdriver, relying on a very small current to earth, usually through capacitive coupling through a user's body, and would therefore come with the sort of instructions you mention.

My understanding is that other ('more sophisticated') ones include true 'field detection' (as has been discussed), which requires no current to flow to earth, and therefore do not require someone to be holding them etc. I would imagine that methodology would probably 'fail' if there were no current flowing through a conductor being tested, so I might suspect (but don't know) that they might well also have the other ('capacitive coupling') methodology built into them (does anyone know?).

Near infinite is an impossible state to reach

Are you just quibbling about how near to 'infinite' one can get in practice? Technologically, speaking, the input impedance of an 'electronic voltmeter' couldbe made to be incredibly high. If a device such as a DVM had a MOSFET input stage, I think we might theoretically be talking in the ballpark of 100,000,000 MΩ - would that be near enough to 'infinite' for you?

so every DVM is current dependant/affected.

Unless, as above, you're quibbling about minute input currents, I'm not sure why you keep suggesting that. In diametric contrast with analogue multimeters, which, in the final analysis, can only measure current (and hence have to covert voltages to current to measure it), DVMs can only measure voltage (and hence can only measure current), can't they?

At school our electroscope was a man made fibre ....

I imagine that any very light (but flexible and visible) material would do (which is why gold leaf was traditionally used)

but yes it is where I was going in my previous but for the life of me the term would not come into my head. However the electroscope requires resetting regularly IIRC, although if it is using such a method to detect I'd imagine some automation is built in.

I'm not sure what you mean by 'resetting'. Once an electroscope has become charged, I imagine that it has to be discharged before it is used again -s that what you mean? However, I only mentioned it to refute your suggestion (seemingly a generalisation) that voltage could not be detected or measured without current flowing into the measuring device. I imagine that such devices would be of no practical use outside of physics laboratories.

I've just done a quick google and 3 different hits describe voltsticks as capacitively coupled to the item under test and also to earth. That to me sounds like current detection ...

As above, that is how the most common types work, but ....

rather than electrostatic.

Electroscopes are 'electrostatic' (which is a third method of 'detection'), and of no use to electricians, but the second method we've been talking about is 'electromagnetic' ('field sensing'). Of those three methods, only the first ('capacative coupling') one requires any current to be flowing into or out of the measuring device.

Kind Regards, John

 

[Harry Bloomfield]

I've not used a voltstick myself but seen a few used and read the instructions for one (when I considered getting one) and that gave instructions to hold just the end

You need to get one, to experiment with. There is no need to hold the end, at least that does not apply to the voltsticks I currently have, the Fluke ones.

I do remember the first one I bought many years ago, which lacked the sounder, may have needed to be held. I found it very unreliable and it soon ended up in the bin.

 

[Harry Bloomfield]

I believe that there are at least two types of 'electronic voltage testers around'. Some (more common, and fairly cheap) are little more than an 'electronic' version of a neon screwdriver, relying on a very small current to earth, usually through capacitive coupling through a user's body, and would therefore come with the sort of instructions you mention.

My understanding is that other ('more sophisticated') ones include true 'field detection' (as has been discussed), which requires no current to flow to earth, and therefore do not require someone to be holding them etc. I would imagine that methodology would probably 'fail' if there were no current flowing through a conductor being tested, so I might suspect (but don't know) that they might well also have the other ('capacitive coupling') methodology built into them (does anyone know?).

I think you have hit the nail on the head there..

 

[SUNRAY]

I believe that there are at least two types of 'electronic voltage testers around'.

I think you have hit the nail on the head there..

And I thank you for that. It clears up my lack of experience with them