proving units

[granthamarms]

are all proving units from different manufacturers the same? if so surely everyone would buy the cheapest one wouldnt they?

 

[PrenticeBoyofDerry]

in theory they should serve the same purpose, but it's very much like saying are all cars the same. They go from A to B.
but a skoda's not the same as a bentley!

 

[Click-Sure]

I've got a Kewtech one, putting the probes of my 2-pole voltage and continuity tester makes the light on the unit light up, and it shows 230v on the tester.

Putting my megger into voltage mode and it registers nothing.

Its good enough for what I want, don't use it a lot, known live is never far away in most places.

 

[granthamarms]

so does this mean you cannot mix and match some equipment?

 

[Spark123]

Nah - the proving unit I have puts out about 700v DC (Martindale)
Set your tester to measure AC and it will not register it.
You shouldn't be using a megger or any other instrument which requires setting for proving dead anyhoo

 

[Click-Sure]

There is always the possibility, however, I'm sure any 2-pole voltage/continuity tester (such as most sparks carry) would be compatible with it.

I wouldn't have any need to 'prove' an MFT, its for measuring resistances and impedances, not for 'checking if the juice is still on'.

 

[BS3036]

You know it always stuck me as strange logic to use a 700V source to show that a voltage tester worked and then use the voltage tester to show whether 230V was present. Isn't it possible that the voltage tester responds to 700V but not 230V?

I'd have felt safer using a 230V source in the first place.

 

[ColJack]

AC 253V R.M.S. = about 357.8V peak..
so that's 715.6V peak to peak... ...

( 253V is max permissable voltage.. )

so your volt meter is actually reading 715V when it's across a 230V supply..

 

[flameport]

If you only have the newer electronic type of voltage indicators, then probably any unit will be suitable.

If you have the older filament lamp voltage indicator, the proving unit needs to have enough output current to ensure the lamp will illuminate - they need a lot more current to work.

 

[BS3036]

so your volt meter is actually reading 715V when it's across a 230V supply..

Mmm... That's a bit of a reach. Peak I'd maybe accept, if the proving unit is dc, but peak to peak? Can't see any justification.

Logic dictates that if you want show that you get an indication on any dangerous voltage, that you demonstrate an indication on the lowest dangerous voltage, not the highest you can think of.

 

[ban-all-sheds]

Mine doesn't say what it puts out, but it doesn't light the 400/560 neon on my indicator.

Or the 400/560 on my indicator is kaput..../

 

[NotHimAgain]

Dr Who could probably measure peak to peak voltage directly, but mere mortals could not .

 

[davelx]

AC 253V R.M.S. = about 357.8V peak..
so that's 715.6V peak to peak... ...

( 253V is max permissable voltage.. )

so your volt meter is actually reading 715V when it's across a 230V supply..

715 pk-pk, but the max L/N or L/E PD is +/- 357.8 so your meter never sees 715v since +ve and -ve half cycles are never present at the same time

(3 phase supplies are different of course)

 

[ColJack]

wouldn't the neutral be on the negative half cycle while the live is on the positive?
or at least it would be on an isolating transformer where the neutral isn't earthed?

 

[BS3036]

wouldn't the neutral be on the negative half cycle while the live is on the positive?

Mmm... remembering that the neutral is connected to earth back at the distribution transformer... what do you think?

or at least it would be on an isolating transformer where the neutral isn't earthed?

If, for example, you earthed the midpoint of the secondary, then the voltage at each end would be halved.