Flash-bang with Multimeter?

[LoveRocket]

When you say "testing for continuity", what do you actually mean? I don't think you understand.

As has been said, you can't test for continuity with power on, because:
1) All the unnecessary dangers of live working
2) You will not get an accurate reading
3) You will destroy your meter
4) You can destroy yourself

As Mikey said, when you're testing resistance with your multimeter, it supplies a very low voltage (a couple of volts) to the circuit you're testing, measures the very small current that this very small voltage causes to flow, and calculates the resistance in ohms.

When you've shoved the probes across L&N or L&E, this very small voltage is increased to 340v (peak), the very small current becomes a very large current, your meter says bye-bye, quite possibly any sensitive electronics says bye-bye, and you are feck1n lucky that you didn't too.

The only testing you should be doing live is VOLTAGE checks, NOT continuity.

PS. I am glad you are still alive to type this post.

 

[Hib]

Ok fellas, i think we'll have to leave it at that, it was 2 or 3 years ago that i bought the meter and read the instructions plus a few other bits in books and on the net and wasn't overly concerned about any health risks based on what i'd read.

There's obviously some confusion here and i suspect overly dire health warnings (circuit breakers plus insulated probes = licence to stab stuff with said probes w/o risk of injury unless you start caressing the electrics with you hand or throwing buckets of water over it). I'll read up on this stuff and get back. But that may well not happen for a long time.

Again, i appreciate your help

PS - beside the probe jacks it says:

Fused
DC 200mA Max
DC 1000V Max
AC 750V Max

Should be OK

Thanks again

 

[Monkeh]

There's obviously some confusion here and i suspect overly dire health warnings (circuit breakers plus insulated probes = licence to stab stuff with said probes w/o risk of injury unless you start caressing the electrics with you hand or throwing buckets of water over it).

If you really believe that, put the multimeter down and step away from the electrics.

 

[ban-all-sheds]

may i safely conclude that continuity testing can normally be done with the power on or off w/o danger of any flash-bang incidents (although it may give dodgy readings with the power on)?

FFS.

Are there not circumstances when it needs to be on?

There are.

But continuity tests are not one of them.

If i had been testing for voltage with the power on would there then have been a risk of something going wrong?

Yes, but you can hardly test for voltage with the power off, can you, unless you mean check for absence of voltage.

on a different property i've tested 2 sockets for continuity between the live and earth and it throws the trip. This likely means the circuit is not earthed properly right?

No, it means you've generated a L/E fault.

You must, really MUST spend a lot more time learning the basics, like what voltage, current and resistance are, how and where current flows in circuits, how domestic AC installations are wired, what RCDs do, what your meter does on each of it's settings, and how it works, where and under what circumstances you introduce it into electrical circuits and what characteristics the circuits will see when the meter is part of them, and so on and so forth.

You've missed out on "Electricity 101", and to carry on despite that is stupidly dangerous.

 

[LoveRocket]

Buddy, no-one's having a go at you or trying to scare you away. But if you'd just have read up on (or asked on here) the differences between voltage checks and con checks, you could probably have safely diagnosed and fixed your oven.

However, you didn't, you dived in THINKING you knew what you were doing, and put an ohmmeter across 240VAC. You now have a fried control circuit on your oven and probably a broken multimeter.

You must realise the enormity of what you've done: you proudly state that you're meter is good for 750VAC - when it's measuring VOLTS, not ohms. You put 340 through a circuit designed for 1-2v. It can handle 200mA. You put enough to trip an MCB instantly through it (120A+).

You were very lucky to walk away from this unscathed. Insulated probes are there to keep you safe when working properly, not to keep you safe when you do things dangerously incorrectly.

 

[Hib]

Cheers Mik and BAS
the probes definitely weren't connected for the current.

well, it was probably alien intervention, or sumthink

That's basically answered my initial question, there should not have been a flash bang, no matter power on or off, regardless of dodgy readings - no flash bang - as you indicate - it doesn't make sense. I know that the current testing socket is something that i have no use for and have never used it.

However, you didn't, you dived in THINKING you knew what you were doing, and put an ohmmeter across 240VAC. You now have a fried control circuit on your oven and probably a broken multimeter

I'm not sure wot ur saying - r u suggesting i had the meter set to ohms rather than continuity by mistake. If so then ur wrong.
If not, and ur saying that testing for continuity is a type of resistance test then that's ok.

However it doesn't explain why Mike can't see any good reason why there should have been a flash bang. To u it's apparently blatantly obvious, but not to the previous posters. I appreciate that u've explained urself, but why does Mike think it required alien intervention?

The meter is fine - when i was buying new probes they tested it - no problems.

on a different property i've tested 2 sockets for continuity between the live and earth and it throws the trip. This likely means the circuit is not earthed properly right?

No, it means you've generated a L/E fault.

So why is L/E fault not being generated on the other circuits?

The only reason I even noticed this is that I was playing around with the meter when I first bought it and ‘generated a L/E fault’ as u say. And that’s what I immediately thought – “aye, L/E connection means thrown trip, all is OK, don’t do it again because it annoys others living in the house”.

I think that was actually 3 years ago, which helps explain why I’ve forgotten so much of what I’ve read in Trevor Linsley’s two books – Basic and Advanced Electrical Installation Work.

However recently on another job, I tried it again (can’t remember why), expecting the same to happen, but to my mild surprise nothing did. So I checked the original socket again – fault. Checked another circuit in the same house – no fault.

Just to clarify -
That's two sockets on 1 power circuit in property A - fault.
1 socket on different power circuit in property A - no fault
1 socket on power circuit in property B - no fault

What's going on?

Sorry – should’ve kept these two issues separate, but too late now.

Thanks for your help

 

[mikhailfaradayski]

well, if it wasn't aliens ( they do exist, you want to see my next door neighbour, either a ponytailed IT geek, or a 'visitor') then it must have been some spurious chance happening that you have overlooked.
If you have disregarded the suggestions so far, then it looks like old mother hubbard has an idea cupboard.

I guess you'll just have to guess (like you do with your continuity results)

BTW, continuity testing from live to earth on a live system is not a clever thing to do. If you want to grow old, please stop doing that!

 

[1john]

r u suggesting i had the meter set to ohms rather than continuity by mistake. If so then ur wrong.

Continuity is measured in ohms, this reading is to be done DEAD, with no power on, you are likely to seriously damage yourself or your meter, as for doing jobs in other peoples property, this all sounds quite scary and I hope for their sake you have public liability insurance that will cover them, sadly insurance cant bring back a loved one.

 

[ban-all-sheds]

I'm not sure wot ur saying - r u suggesting i had the meter set to ohms rather than continuity by mistake. If so then ur wrong.
If not, and ur saying that testing for continuity is a type of resistance test then that's ok.

Oh good grief.

You must, really MUST spend a lot more time learning the basics, like what voltage, current and resistance are, how and where current flows in circuits, what your meter does on each of it's settings, and how it works, where and under what circumstances you introduce it into electrical circuits and what characteristics the circuits will see when the meter is part of them, and so on and so forth.



And please write in English.

 

[Hib]

well, if it wasn't aliens ( they do exist, you want to see my next door neighbour, either a ponytailed IT geek, or a 'visitor') then it must have been some spurious chance happening that you have overlooked.

Right, so Mike and Rocket are in complete disagreement but i'm the only one who thinks that's strange, given that both are equally dogmatic in their opposite conclusions. Dandy-O

Thank u John and Sheds, i heard u the first time (regarding safety) and haven't done any testing since. Nevertheless, surely once again u can see why i think the test results are strange? Why are L/E faults not always being generated?

sadly insurance cant bring back a loved one

That's Ok, i don't love anyone

C'mon fellas, the testing and damage are done, stop the b*tchiness and answer the questions please. I promise i won't do any more dodgy testing.
If u can't answer the above points just say so. Stop hiding ur lack of answers behind health warnings.

Why are Mike and Rocket in complete disagreement? Mike says there absolutely should not have been a problem while Rocket says it's practically a miracle that i'm alive!!!!!!
Someone's talking rubbish somewhere

Why aren't all the sockets generating faults?

Appreciate ur help.

 

[LoveRocket]

DON'T PUT A ****ING OHMMETER ACROSS A POWER SUPPLY. ESPECIALLY NOT A MAINS POWER SUPPLY.

You still haven't grasped the difference between a continuity (resistance) check and a voltage check, have you?

If you want to do a live test for earth continuity at an outlet, measure the VOLTAGE between L & E. DON'T ATTEMPT TO MEASURE THE 'RESISTANCE' OF A LIVE CIRCUIT ACROSS THE POWER SUPPLY. Have you got that?

As to your question, an RCD can only trip if it's there in the first place. Not all circuits are RCD protected.

PS. I can't see where Mikey has disagreed with anything I've said...

 

[Hib]

You still haven't grasped the difference between a continuity (resistance) check and a voltage check, have you?

Yes Rocket, believe it or not i have. U keep goin on and on about how it's not a good test which i've accepted.

Ok the RCD thing, so maybe property B wasn't RCD protected? Right, that's grand. So why are two different circuits on property A, which is RCD protected, giving different results. Surely that's a reasonable question now that the tests are already done.

PS. I can't see where Mikey has disagreed with anything I've said...

I generally don't swear Rocket, but if i did, i reckon now would be a pretty appropriate time. U can't be serious

Thanks again

 

[ban-all-sheds]

...u ...u ...u ...u ...ur ...ur

Please write in English.

 

[LoveRocket]

1. It's not that it's "not a good test", IT'S NOT A TEST AT ALL.

2. Please explain the difference between a voltage test and a resistance/continuity test.

3. NOT. ALL. CIRCUITS. ARE. RCD. PROTECTED.

 

[Hib]

C'mon Sheds - don't be like that. Why don't u criticise all the spelling mistakes made on here simply because people couldn't be bothered correcting them.

Ok Rocket - i'll grant that it's not a 'test', lets call it an 'action' then. Why aren't the results of my 'action' the same. I'm almost certain that the entire property is protected by the same RCD - i'll confirm that later. If so, why the different results?

2. Please explain the difference between a voltage test and a resistance/continuity test.

I'll explain when you (or at least someone here) admits that you and Mike are in complete disagreement over the oven testing. Stop calling black white.

Thanks fellas