What's your definition of 'ghost voltage' ?

[Lucien Nunes]

I don't like the term 'ghost voltage' a.k.a. 'phantom voltage*' much, not least because it's rather loosely defined and probably means different things to different people. I also suspect that quite a few people use the term without really understanding what it is they are referring to.

My definition of what constitutes 'ghost voltage' is quite specific, but first, what is yours?

*OTOH 'phantom power' (as used to power condenser mics and other audio sources via the signal cable) is a different kettle of spooks and very clearly defined.

 

[SparkyChick]

I'm assuming you're talking about the sometimes spurious voltage readings we can get when testing for dead at various points in a circuit?

If so, I don't like the term ghost voltage... my personal choice is induced voltage because it is induced in the conductors by either induction, capacitance or a combination of both. It could also be residual voltage, from say a capacitor in a capacitive dropper or a filter.

 

[Lucien Nunes]

I'm assuming you're talking about

My point exactly. I know what I'm talking about, you know what you're talking about, but there's no guarantee we are talking about the same thing as there's no official definition.

It could also be residual voltage, from say a capacitor in a capacitive dropper or a filter.

I would not include this under the heading of 'ghost voltage'. It's the voltage due to residual charge in a capacitor, fair and square.

 

[snowhead]

I don't think I've ever use the term Ghost voltage but as S - Chick above, to me it's describing a measured (induced) voltage, but if you connected an appliance to it the voltage would drop to zero.

Not the same as a poor connection / failing switch or isolator where the circuit won't sustain a load, as that voltage comes from a true source.

There's no official definition because the term is too vague, almost Ghostly,,,

 

[DPG]

A voltage arising from incidental pickup by either inductive or capacitive effect rather than by direct and intentional connection.

That's mine, let me know what you think.

 

[SparkyChick]

I would not include this under the heading of 'ghost voltage'. It's the voltage due to residual charge in a capacitor, fair and square.

I agree, which is partly why I don't like/use the term ghost voltage because it's just too vague.

 

[ipf]

My point exactly. I know what I'm talking about, you know what you're talking about, but there's no guarantee we are talking about the same thing as there's no official definition.

Entirely agree. It might take a séance to fathom that one out as it's potentially spiritual.

 

[littlespark]

Ghost voltages. Measured in “caspers” apparently.

 

[Lucien Nunes]

A few people have mentioned capacitive or inductive coupling, what about resistive leakage into a conductor?

rather than by direct and intentional connection

This is very similar to one of my own criteria for qualifying something as ghost voltage.

 

[DPG]

A few people have mentioned capacitive or inductive coupling, what about resistive leakage into a conductor?


This is very similar to one of my own criteria for qualifying something as ghost voltage.

Resistive would be a different thing for me,as it would imply some sort of direct connection.

 

[static zap]

a)-- Not advisable ...
One that doesn't tingle
(turn you into a Ghost if touched !)
But detectable on delicate hang nail flesh.
------------------
b)... I would say vanishes with 22k ohm --
or am I not tripping here
c) Disappearing when drummond applied ?
(MFT test impedances are high enough to show phantom voltages)

 

[Lucien Nunes]

Aha, an actual number. Not sure what ratio 'vanishes' constitutes so can't convert that 22k into a source impedance, but a step towards my own definition.

To me the distinction between resistive leakage and capacitive leakage seems arbitrary. In any case if one wants to classify between deliberate and accidental sources, capacitance is often built-in but resistive leakage sources are just non-infinite insulation resistance, hence unintentional.

 

[DPG]

Good discussion Lucien.

 

[static zap]

So I need to hunt ghosts with an Oscilloscope , for their " Phase " relationship.
(My status will be spooked)
(or can we even squeeze this relationship out using phase rotation built into some 2 pole testers !)

 

[littlespark]

After my Casper joke.... I should have thought “who you gonna call?....”

But only if they’re registered with a ghost hunter competence scheme and listed on “trusted ghostbuster dot com”

 

[R-fur]

The National Grid Co have very specific terms for voltages on conductors and how they got there. I think they have four terms from memory, Trapped charge, capacitive coupled, induced voltage, cant remember the other one. They are talking about EHV circuits obviously the theory is similar.

 

[buzzlightyear]

funny you mention the post ,I had one to day on my megger no voltage present
and started do show OL ghost voltage , the last time it came up I rang megger the person on the other phone said how spooky , I started to singing goat busters bang me head against a wall.lol

 

[Darkwood]

It's obvious that none of you have ever seen a supernatural film, a ghost voltage is the thing that makes the lights flicker and the tv come on when it's not plugged in... seriously, where you been!

 

[dmxtothemax]

My definetion of ghost voltage is a measurable voltage that is of such a low current it can do no real work.

 

[telectrix]

it can do no real work.

a bit like an Aussie then.