Digital Meter

En el artículo , Sam escribió:

Thanks again. Bookmarked. May combine that with a few days in Swansea, never been down that way and believe it's well worth a visit.

John

I remember the cooking dust and slow baking plastic smells, and ozone if ar cing.

Mercury rectifiers don't smell, they're just a bit like having a nicely pol ished hand grenade in the room. They should never go wrong. But you know th ey could.

NT

I do indeed. However, I *am* still here. ;-)

I have so I couldn't use that one. ;-)

Don't I know it. ;-)

Ok.

Or any other 240V 'thing' etc ...

Or there was a car after all ... or the gas bottle you used for the compressor expansion was weakened somehow or the time you forgot you put your safety glasses or gloves on etc etc. ;-(

Which is where I thought we were in this case?

What would you expect for £2.99. ;-)

Cheers, T i m

damn, you got stung!

Personally I don't mind using such meters after a low value mains fuse eg 5 A lighting circuit. If things go wrong it will destroy the meter, not you. But inside the CU? Not with a China special.

NT

Mike Tomlinson wrote in news:GYoySJD5$OcZFw+1 @jasper.org.uk:

Hope you go:

https://www.google.co.uk/maps/@53.0625974,-1.386387,101m/data=!3m1!1e3

On the positive side I'm living rent free in your head (troll) and that makes me happy. ;-)

I did (effectively), as a kid, when using my teeth to strip the insulation off the two ends of some broken xmyth tree lights ... and yet somehow I'm still here?

Anyway, I'll have to check the current legal status of 'incitement to commit suicide' ... (so thanks for that).

Cheers, T i m

I wouldn't use one if I had something 'better' to hand, if only because the leads are often not particularly nice.

I can't see how likely it would be to need to use one inside a CU (not that anyone was talking about doing such specifically) but if you had lost all power, it was late / dark / cold and had nothing else ...

Cheers, T i m

Museum of Internal Fire -

Just to the north of Cardigan. Well worth a visit, mention my name to the guy who runs it, if you ever get there.

This subject comes up from time to time, and always seems to end up in a discussion that goes around in circles for one reason or another. Usually because someone will caution that there are risks associated with dealing with higher energy electrical feeds and that some test gear is better able to mitigate those risks than others. Someone else then normally then get all anecdotal and reminds us they have managed with a £2.49 meter from the market stall for the last 4 decades and their grandfather before them and never had a problem.

The reality is that for lots of DIY activities, the cheap meter will be adequate - you are probably not interested in high accuracy, and it will beep nicely while buzzing out that USB lead or appliance flex. If you are into electronics or computing or appliance repair etc then you will find it invaluable for all kinds of things.

The pro electrician will carry pro level gear plus have a much more nuanced knowledge of what situations pose more risk. They are also far more likely to be making measurements on live installations in more risky situations.

The difficulty comes when those two worlds mix. Say for example someone decides they need to test if a socket is live, so they defeat the shutters on it and poke their test leads into the socket. Usually this will be safe enough. However there may be a problem like they forgot they had the meter still set to an ohms range, or set on a current measurement range (or they are on the right range but unlucky enough to pick the moment there is a big transient spike on the supply).

What happens next will then be determined by a bunch of factors outside the users control that range from the meter indicating an error on the display, to it blowing an internal fuse, to going pop, to going bang, to going bang and catching fire, to exploding, to exploding and showering those nearby with flying bits of meter and some molten test leads and bits of copper, to doing all that and causing an arc flash explosion a the socket, to - well worse - you get the picture.

It might be you live in a place where you are very close to a sub station and have a very low supply impedance. It might be that the prospective fault current in your CU, and for that matter, at any socket or light fitting relatively near to it, will have a prospective fault current that is high enough for these bad things to happen. It might be so high that it even exceeds the breaking capacity of the circuit breakers in the CU itself, meaning that in the worst case you are relying on the incomer main fuse for ultimate fault protection. On a supply rated at ~24kW nominal continuous (and probably ten times that under fault conditions) you can probably see there is potential for things to get out of hand quickly.

So how does one advice on a choice of meter? Its difficult without being cautious and including relevant warnings to the prospective user - especially if you don't know if they are the type likely to know what a prospective short circuit current is, or know what it actually measures in their house, or which accessories are within very low ohms range of the consumer unit.

Mike Tomlinson wrote in news: snipped-for-privacy@jasper.org.uk:

Part of a battery charging system from 1958

... and for whom? If I told my BIL he needed to spend even 20 quid on a meter that he might use a couple of times to check a battery or a fuse ... before forgetting where he put it or finding it 'dead' (flat battery) I know he's going to say 'no thanks'.

If I gave him a DMM I bought 5 of for £1.99 each (+ a PP3) he would probably (not) use that either, especially anywhere near anything mains voltage.

However, if I'm ever over there and they ask me to test / fix something, at least I will have *something* to work with and that might be safer than some other test I might try to rig up instead. ;-)

Of course, but I'm not sure anything I say (for example) would have any impact on that ... and as they say, 'buyer beware'.

The problem is, even a 'good' meter in the wrong hands could be a liability (to that user ... and using your usage of 'poking about in a CU'), as could a screwdriver ... or a finger. ;-(

So, for the record, I'm not and never have *recommended* the use of any sub-par test equipment under any circumstances to anyone. What I would like though is every house to own a DMM, a foot pump, battery charger, a reasonable range of tools etc etc so that when I happen round there and find myself having to fix something for them, I've got something more than my Leatherman PST II to use. ;-)

Cheers, T i m

But the problem is that, because they don't use the tools, they get relegated to somewhere in the back of a damp shed and get rusted up to the point of being next to useless by the time they need you to use them.

En el artículo , Harry Bloomfield escribió:

Many thanks. Added to the list

Well the obvious thing is to have two meters, one that only does volts and one a clamp on for current. Its pretty safe then.

Of course there isn't really much need to poke about in a live CU.

En el artículo , Mike Clarke escribió:

Either that or they're cheap s*it - e.g. screwdrivers made of cheese - which is useless.

Before I married Mrs Tim Mk2 (and had kids) I kept and used my Myford ML10 lathe, bandsaw and pillar drill etc in (what others would have called) the middle bedroom, where it all stayed nice and warm and dry.

Now they are in the workshop, I have to make sure I keep the lathe covered in the winter to (as you reference), stop it going rusty.

On the other hand, the kids wouldn't have gone rusty in the workshop//////// annexe building ... ;-(

Cheers, T i m

The other issue is that *possession* of one of these alone, even if you know what its limitations are and use it appropriately, can still cost you dearly. One of your teenage kids may pick it up one day, see it's rated for 250V and stick it in the mains right at wrong moment. I'd sooner have no meter at all if I had kids around.

On 18/07/2017 12:47, Martin Brown wrote: o consider the possibility that your leads are less than perfect.

The problem is the failure mode ... if neon blows a user can assume no glow = safe

But I do have some more than 40 years old still working - so pretty reliable.

For most things I use a Digital Multimeter or a Martindale Tester (I know this is neon - but lots of them)

The thing that I like about volt sticks is that you are not waving a bit of metal against and around other bits of metal which could be either live, neutral, or earthed.

That said, I have known volt sticks not play at one moment, then work fine the next. I think both volt sticks and neons have their place.

Most important is a healthy amount of caution on the part of the person holding them. Less so if you are *sure* you have RCD protection, as long as you remember that this is no help if you touch live and neutral at the same time.