Why are proving units so expensive?

[spark 68]

I have two smaller faulty ones that I got given, I may take one of these to bits later and post the pics.

I would rather not take the afore mentioned PD690 one apart.

 

[brman]

as spark68 said you need a step up circuit. This can either be done with a transformer (but you also need to create an AC supply from the battery to supply the tranformer) or a charge pump.

A bit of info here.... Voltage multiplier - Wikipedia, the free encyclopedia



Or of course you could just use the IR test mode on your MFT on the odd occasion when you don't have a live supply to use!

 

[ickleant]

Talking of info:

Why Are Proving Units So Expensive? / Tester Blog

That explains it pretty well but dosen't make my wallet feel any happier!

they seem to have a lot of articles that people have been asking on this forum....

 

[stef]

I have a circuit diagram somewhere, only a few tranny's and a transformer, not much to it. Basically a battery powered oscillator (sine) which transforms up to 240 v. But when you build one yourself you might get problems getting it calibrated.

 

[ickleant]

I vave a corcuit diagram somewhere, only a few tranny's and a transformer, not much to it. Basically a battery powered oscillator (sine) which transforms up to 240 v. But when you build one yourself you might get problems getting it calibrated.

then you just need to build a calibrator

 

[stef]

... Which needs to be calibrated as well. I don't know actually whether a proving unit has to be calibrated at all. If not then yes, you can build one yourself.

 

[1shortcircuit]

I know I will get slapped wrists for this but I have got into the habit of testing for dead with my voltage indicator then double check with my voltage stick(non contact type). At least I can wave my voltage stick around the tails to check it is still working. Something I cannot do with a VI if the isolator/meter is sealed.

I reckon proving units are so expensive purely because they don't sell enough of them to get economies of scale!

That's going to do more than bite you on the arse one day, fine to use to prove live but using it to prove dead could well make you dead :lol Silly sausage

 

[snowhead]

... Which needs to be calibrated as well. I don't know actually whether a proving unit has to be calibrated at all. If not then yes, you can build one yourself.

I've just checked the instructions on my new Martindale.

Proving unit, no mention of calibration.
Voltage indicator, to be calibrated yearly.

 

[madseb]

i got one free as an "incetive"at an old firm. and didnt realy use it. must admit ive allways used the incoming supply as a means of proving my tester.
although after looking at what my little kewtech unit would have cost. cant belive the prices?

 

[IzzyS]

Proving on the incomer is no good when there is no supply on the incomer.

In 45 years I've never felt the need to own or use one, I've always used the 3 meter system.
If you test with 3 different meters the chances of all 3 being U-S are about as high as being hit by lightning in a cellar.

However I've just been given one by my current employer so I'm now looking for the chance to use it. I think I may use my 3 meters to prove the prover just in case it's no good. And then a final poke with an earthed cable.

Woman struck by lightning in Wakefield - Boston News, Massachusettts News, WHDH-TV 7NEWS WHDH.COM

 

[the pict]

£50 plus vat is the cheapest I'V seen I need to get one for my 1st assesment soon so when the guys gone it'll be out with battery back in its box till next year I mean who the hell is going to test the tester, go up a ladder test the incoming tails, turn it of test the tails test the out side of the iso go down the ladders test the tester go back up the ladders and test the dead side again I mean whats the punter going to think, jeez I mean if the little lights go out it dead ffs
Pict

 

[Remooc]

£50 plus vat is the cheapest I'V seen I need to get one for my 1st assesment soon so when the guys gone it'll be out with battery back in its box till next year I mean who the hell is going to test the tester, go up a ladder test the incoming tails, turn it of test the tails test the out side of the iso go down the ladders test the tester go back up the ladders and test the dead side again I mean whats the punter going to think, jeez I mean if the little lights go out it dead ffs
Pict

Hello first post on the forum,
I have just had my yearly inspection with the nic and was asked to do safe isolation and at the end I told the inspector that I was checking the incoming side to make sure the voltage indicator was still working and his reply was "very good making sure that the unit is still working so you know that you are now safe to work" looks like proving units can stay on the shelves.

 

[Rob Smith 643]

I got one 'free' when I bought a Martindale VT a little while ago, foolishly believing it would be a Martindale brand proving unit. Wrong! Piece of cack arrived instead. But it works and was free, though a little awkward to use - so I generally don't. :lipsrsealed2:

 

[the pict]

one went for 26quid on ebay, I got a martindale 690 for £40ish there
Pict