Flash-bang with Multimeter?

[Hib]

Hi folks,

is it possible to cause components to blow just by checking them for continuity, or by checking continuity between different components.

In other words can i just randomly check continuity in an appliance w/o fear of something blowing as long as i don't make any mistakes - like grabbing hold of the live for example?

Cheers

 

[mikhailfaradayski]

continuity testing shouldn't cause an issue, insulation testing on the other hand...

What meter are you using?
What are you testing?
Why haven't you isolated the appliance before carrying out any tests?

 

[Hib]

I'm using a £10 tester jobbie - quality stuff

An old cooker

Isolated? Can be done sure, but aren't there some tests for which the power has to be on?

Thanks for your help

 

[efiste2]

If your not 100% on basic multimeter use, best to do any testing with the appliance isolated from its power source, or even better leave it to someone who knows how to..... However if you do decide to do it "LIVE" so to speak.Its a good idea to have FUSED test leads. these £10 jobs usually dont have! You would be suprised how many people who think they know how to use one, dont understand the basic principle of how the meter actually measures volts and amps, ie in terms of impedance....

checking coninuity on an isolated appliance shouldnt damage any components, unless your poking about on sensitive chipsets etc etc.

 

[mikhailfaradayski]

I'm using a £10 tester jobbie - quality stuff

An old cooker

Isolated? Can be done sure, but aren't there some tests for which the power has to be on?

Thanks for your help

ah, any further info on what is wrong with the cooker, what are you (specifically) testing and what tests you think need to be done live?

 

[1john]

Doing a continuity test on a live appliance will upset your multimeter.

 

[Hib]

My query has to do with a job that's already done - here's the link - //www.diynot.com/forums/viewtopic.php?p=1410850#1410850

That was a about 6 months ago.

When i was testing, i reckon i had pretty much narrowed it down to the problem component/connection and was checking for continuity between that component and everything it was connected to when all of sudden something strange happened... then i realised i'd been initiated into the flash-bang electrical club!

One of the probes wasn't looking so good and the fuse at the main board needed replaced.

Anyway - it just took me by surprise as i had thought that i could do all the continuity testing i wanted w/o danger of that happening.

I've been busy since then, that's why i'm only getting around to mentioning it now. Obviously since then i've been a little hesitant to go poking around at these things b4 i understand what happened.

Unfortunately i've forgotten exactly what i was testing between - it was between one of the connections to the main oven controller and something else - i realise that's probably a little vague to be of much use. I thought i'd remember - but it was 6 months ago - way too long for my goldfish memory.

i was testing live because i was getting different readings depending on whether the power was on or off.

Yes, i know - health and safety and all - but hey...

Freedom includes the freedom to take risks with one’s own health (within reason)

Thanks for ur advice

 

[mikhailfaradayski]

just a guess really, but does your meultimeter have the facility to measure current? How many holes are there in the meter to accept the test probes? some have 2, 3 or 4

If you had it set to check current and then tested across L to N or E, then that would explain the bang

 

[Hib]

The meter is a 'skytronic digital multimeter 600.006'

3 holes on the right for the probes, one different socket on the left - can't remember what that's for - someone thought that the multimeter packaging and instructions were so nice that they'd really help the look of the inside of a bin - unfortunately.

It can measure DC amps, but i'm sure it was set to continuity.

So, unless anyone has any further suggestions, can i assume that i was right in assuming that it is normally safe to test continuity between just about anything w/o causing damage? (not according to John1 - in what way would it upset the meter John?)

Just the other day a shower decided to stop working but i didn't want to use the meter in case something similar happened.

in ur opinion, should i be able to do all the necessary checks while the appliance is isolated? Are there not circumstances when it needs to be on?

Thanks

 

[ban-all-sheds]

There are.

But continuity tests are not one of them.

 

[mikhailfaradayski]

I suspect there is a different socket for the probes depending on whether you are testing for voltage(and continuity) or current.

If you had a probe in the 'test for current' socket, not the 'test for voltage' but you then touched on something live, it could rapidly go into melt down. (some current meters are unfused, which makes them more accurate, but care needs to be used) this would probably happen irrespective of the setting on the meter control.

 

[mikhailfaradayski]

also, about Johns comment-

Continuity testers work by outputting a certain known voltage(probably quite low), when connected to something of a certain resistance, the current that then flows through the meter is used to calculate the resitance you wanted to find. If the thing that you connect to already has voltage present, the meter will give the wrong result.

 

[Hib]

Cheers Mik and BAS

the probes definitely weren't connected for the current.

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

Either way, 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)? Just so i know for again as i mentioned about the shower above.

Also - while u are being so helpful (which i appreciate) - 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? The other power circuits in the house are ok. What are ur suggestions - loose earth wire at the fuse board?

Thanks

 

[mikhailfaradayski]

Cheers Mik and BAS

the probes definitely weren't connected for the current.

well, it was probably alien intervention, or sumthink

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

You could electrocute yourself

Either way, 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

no, that is not a good conclusion at all

(although it may give dodgy readings with the power on)?

next time, why not just guess, about as accurate and less dangerous

Just so i know for again as i mentioned about the shower above.

Also - while u are being so helpful (which i appreciate) - 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? The other power circuits in the house are ok. What are ur suggestions - loose earth wire at the fuse board?

Thanks

oh dear, do you have a picture of your meter?

 

[STI]

I am probably wrong here but shouldnt all continuity tests, my very simple definition "does the circuit/cable run without a break/damage in/to it, from one end to the other", be done without power and therefore the breakers wont/cant trip.