Do cheap meters explode when you abuse them?

[paulie]

Apparently not. At least not in my initial crude non-scientific tests  (see pics below). BTW this is a continuation of the discussion in another thread which was totally hijacked starting on second page: https://www.eevblog.com/forum/testgear/the-uni-t-ut33c-or-d-how-good-they-are/15/

First abuse involved applying to a car type battery while set up for ohms measurment. No detectable damage. Meter still works fine in all ranges. Then tried it in milliamp range. This time meter stopped working. Later verified fuse was blown which is to be expected.

Next came shorting directly across the battery with probes plugged into 10a jacks. Range settings do not matter under these conditions because probes are essentially connected only to the shunt which is really a dead short. No bright flash, explosion, or shrapnel. What did happen was NOTHING at first. Even pressing hard to ensure good contact.

I put the camera down and checked battery voltage with another meter in parallel (set  to measure VOLTAGE!). It drops from 14.3v to a little over 14.1v indicating considerable current drain but holding up well. For about the first 20 seconds no indication anything was amiss except probe handles heating up. I'm sure the cables themselves were getting real hot but holding probes and camera not enough hands to check.

Then the cables started squirming and a few seconds later hints of smoke. This went on for about another half minute after which the smoking got serious. At about a minute and a half the smoking decreased until after another minute no hint of smoke or heat. I assumed at this point one of the leads had opened and verified using the same meter with new fuse and another set of probes. See photo below of the obvious damage.

I also experimented with applying lines voltage in a variety of incorrect settings. results were pretty much the same as smjcuk in that other thread:

I just stuck one of my UT33As on an extension block in the kitchen across live/neutral and poked it on ohms and turned on the mains. No explosion, no lead heating. Ohms range still works. Turned off, switched to amps, fuse popped instantly as expected.

I don't recommend you do this, but it at least it is a data point.

We are talking dead short across 240vac, serious abuse. Blown fuse but no damage to meter or  probes.

So being much braver than him (and meter that did not cost even one penny) I decided to see what happens there but with probes plugged into the 10a jacks. Unlike with the battery there WAS a bright flash this time but no damage to the meter or leads because the six outlet strip breaker tripped. Reset breaker and one more time same thing, flash and nothing  except some pitting on probes.

I do believe the videos of exploding meters are real and have no doubt top end products like Fluke are much safer under those conditions. However we're talking kilovolt potentials with nearly unlimited current. That bank took up half the room. Strictly a scientific curiosity. Nothing anyone using one of these cheap meters would conceivably encounter.

No doubt playing around with mains is dangerous and unless you know what you are doing make no attempt. Grabbing the wrong wires or careless handling of a tool can be fatal. However IMO the fear mongers go a bit overboard with warning to never use cheap meters for anything except low voltage and low current. I'm convinced ratings manufacturers put on these are reasonable and personally would not hesitate to use them as designed. Certainly in the case of Harbor Freight or Uni-T products. Like any tool though misuse can have tragic consequences so be careful and make sure you know what you are doing.

update: I did some kilovolt testing of the above meter but joeqsmith did a much better job on a similar Harbor Freight cheapie so I hope he don't linking it here:



Not as entertaining as ones posted in this thread from Dave, Fungus, the Fluke guy, and others but unbiased objective reviews do have a place too. Probably most out there, by taking note of demeanor and  body language, can judge for themselves where these fit in that respect.

[SeanB]

See Martin's video of his visit to Fluke.

http://mjlorton.com/forum/index.php?topic=821.0

There you see that meter being tested to the marked standard, inside a cabinet. Then a well used Fluke meter is plugged in for the same test, and this time the meter is out of the cabinet and is being held in the tester's hand.

He also indicated that the supplied leads with the meters was always going to fail at high current, and that often they were faulty out of the box.

[Muxr]

Isn't the lead damage you show in those pictures exactly what I warned about? You called me a fearmonger for pointing out something you actually reproduced on a first try? I remember your response being, "bah, it's alright PCB trace is a fuse!".

Kids don't buy unfused meters, $38 saved isn't worth it over a properly fused meter.

[Fungus]

The problem with giving out multimeter 'wisdom' in online forums is that people read it and repeat it.

If you've never played Chinese Whispers then maybe you should. It's astonishing. Even five or six people can utterly change a simple message. You have to see it with your own eyes to believe it. It doesn't seem possible.

A posting that says "I plugged my UT33C" into a car battery and nothing happened" will soon change into "Yeah, dude, I know this guy who totally knows electronics and he says these $4 meters are fine and that all those people who pay $200 for meters are fools. Let's see how many Amps your house is using".

The ONLY correct advice in online forums IMHO is to tell people to do things correctly. Don't poke multimeters into mains sockets.

PS: Here's some more "data points" to peruse...

CAT III meter nearly kills our host:

Expensive CAT III meter kills two people: http://ecmweb.com/arc-flash/case-deadly-arc-flash

Edit: Nope, it wasn't "CAT III", my feeble memory was mixing it up with another story about a dangerous meter.

[Monkeh]

Expensive CAT III meter kills two people: http://ecmweb.com/arc-flash/case-deadly-arc-flash

Errr, no, if you read that, you'll find that not only was it never CAT rated, but that it was never even tested to full supposed operating voltage.

The electrician probing a high energy circuit with an inappropriate tool and no PPE killed himself and the guy foolish enough to stand next to him.

[paulie]

The problem with giving out multimeter 'wisdom' in online forums is that people read it and repeat it.

We absolutely agree on that. The previous thread and many others before that too are a clear example.

[Fungus]

The electrician probing a high energy circuit with an inappropriate tool and no PPE killed himself and the guy foolish enough to stand next to him.

Oh, memory failed me since last time I read it (which was in a thread about a dangerous meter with "CAT III" stamped on the front).

How about we change it to: "A trained electrician plus bystanders were killed by a cheap-ass meter. Would still be alive if he'd used a $200 meter..."

Happy now?

[Fungus]

The problem with giving out multimeter 'wisdom' in online forums is that people read it and repeat it.

We absolutely agree on that. The previous thread and many others before that too are a clear example.

Every forum has a variant of this thread.

eg. In Arduino forums it's, "I connect LEDs to my Arduino without any resistors and they work perfectly! I do it every day!!"

[Mr Simpleton]

Long time ago I had this quality meter, think it was a Metrawatt... problem was that the range selector was a round wheel and very easy to set in the wrong position. I ended up with mA range and put the test leads into a mains socket... Yes this was pretty close to what I would call an explosion! The shunt desintegrated and tried to penitrate the box in several places, I guess it not only tried by force but also melted the plastic...

Now having done this I promtly borrowed a Simpson meter, and yes do not ask why but this was set into 10 A range and used in the same mains socket. This took out the wall fuse, but damage to the meter was minor.

So I would say, considering my first hand experience: It depends!

[Fungus]

One more datapoint (last one, I promise):

A Fluke 101 with shipping can be had for less than $43, eg. http://www.ebay.com/itm/331068818894

If you work with household mains and need to measure actual voltages then that's as much as you need to spend to be pretty damn safe.

[Fungus]

So being much braver than him (and meter that did not cost even one penny) I decided to see what happens there with new probes plugged into the 10a jacks. Unlike with the battery there WAS a bright flash this time but no damage to the meter or leads because the six outlet strip breaker tripped. Reset breaker and one more time same thing, flash and nothing  except some pitting on probes.

How close were you to the distribution panel? A few meters of wire between you and the panel can make a big difference (it's the main difference between CAT II and CAT III ratings).

[paulie]

The ONLY correct advice in online forums IMHO is to tell people to do things correctly. Don't poke multimeters into mains sockets.

We ALMOST agree on that. I would slightly modify as follows:

"The ONLY correct advice in online forums IMHO is to tell people to do things correctly. Don't poke multimeters into mains sockets UNLESS YOU KNOW WHAT YOU ARE DOING."

Certainly more deaths occur every year involving mains voltage and paper clip or hairpin. I am serious.

CAT III meter nearly kills our host:

LOL. Thanks for that one. I love that guy. I've collected over a dozen of his dealing exclusively with "shit" meters and every one a gem. None of the others even hinted at "death by bang" though. Yours are up there too. In addition to the actually good advice I find specially amusing the way you guys cradle and coo over the "good" product and snarl and toss around the "bad" one.

ps. I also got a kick out of the time over-voltage blew the dial right off the Fluke and across the room. After picking it up and popping it back in he said "Good as gold!" even though it was obviously trash. Or the time the Fluke was dropped from huge heights and finally broke from 100' or so. "No problem... just a broken display and dislocated inductor!".  Priceless, or should I say "Un... Buh... Leeeevable !!!".

[Fungus]

LOL. Thanks for that one. I love that guy. I've collected over a dozen of his dealing exclusively with "shit" meters and every one a gem. None of the others even hinted at "death by bang" though. Yours are up there too. In addition to the actually good advice I find specially amusing the way you guys cradle and coo over the "good" product and snarl and toss around the "bad" one.

Not so fast: I dissed a Fluke 27 in my "Sparkfun" video.

Took some flak over it, too. 

[paulie]

Isn't the lead damage you show in those pictures exactly what I warned about? You called me a fearmonger for pointing out something you actually reproduced on a first try? I remember your response being, "bah, it's alright PCB trace is a fuse!".

I don't recall using that phrase, maybe something from somebody misquoting me in a moment of passion. But IIRC you were probably the first to bring up leads melted by car battery. And not so prone to exaggeration and excessive FUD as HW calls it. Not like some of these guys anyway.

I do think it's great to bring up these points, even the hysterical extremes, as anything to promote care around high voltage and current can only be a good thing. If a noob spends a few buck more than necessary based on advice from an over excitable pundit, no big deal. Underestimating the dangers of electricity... different story.

[paulie]

Not so fast: I dissed a Fluke 27 in my "Sparkfun" video.

Took some flak over it, too. 

Yes, 99% of the time you guys provide sound and balanced advice. Hard to hide prejudice over cheapo product.

BTW many comments in that review rang true. For example we both appreciate small compact packages. One reason I am partial to the cheapies is they are no so bug and clunky as "real" DMMs.

ps. "big" not "bug"

[Fungus]

I would slightly modify as follows:

"The ONLY correct advice in online forums IMHO is to tell people to do things correctly. Don't poke multimeters into mains sockets UNLESS YOU KNOW WHAT YOU ARE DOING."

Dave's video says the multimeter exploded in his hand. I'm sure Dave knows what he's doing.

Maybe we can agree on: "Don't poke multimeters into mains sockets UNLESS YOU KNOW WHAT YOU ARE DOING and bought a Fluke."

(Yes, there are other brands out there apart from Fluke but this is 'general advice for Joe Public' and how many non EEVBLOG-readers would know where to buy a Brymen/Gossen/Agilent/whatever?)

[c4757p]

Nothing wrong with inexpensive meters, but you're a chump and the seller a prick if you buy one that's unfused. This very controlled experiment is not evidence against the need for fuses.

[smjcuk]

Notes about my experiment:

1. I didn't use the unfused 10A section of the UT33A. You'd have to be a fucktard to poke any meter in a 10A circuit or more even if Bono from U2 himself cast it from his own molten ego. That's what clamps are for. I wouldn't even trust my Fluke 77 with this.
2. I'm a qualified EE so understand the safety consequences of this experiment and how to control and isolate the power safely.
3. I'd be happy to use a UT33A for casual electrical work around the house and office i.e. AC voltage go/no go testing and earthing continuity/resistance as well as electronic work.
4. I'm in the UK so we have real 240v *everywhere*, not just in some circuits.
5. This applies to this UT33A and this revision of this UT33A

TBH I was expecting it to explode. But it didn't.

The important point is not "and buy a fluke" but "know what you are doing and check and double check before you do it".

Now I know someone who just blew up a Megger MFT1730 on a 415V circuit so at £950 don't expect miracles either if you do something stupid.

[Ian.M]

You are also a chump if you hold a cheap meter in your hand while probing a mains circuit.  That violates the basic safety practice of keeping one hand in your pocket when probing circuits that exceed SELV voltages to avoid the risk of getting a shock across the chest.

If you need to hold the meter in your hand while probing fused mains circuits, then you should get a professional quality, appropriately rated one with a rubber sleeve on it as that adds extra protection where you are most likely to be gripping it, which can only help if it fails catastrophically.   If you are probing high current high voltage circuits, you should be using individually fused test leads as well.

Dave should probably have been more cautious and initially tested the meter on his bench, not in his hand, but that was many many EEVblogs ago and I'd bet that after all the cheap multimeters he has seen since then, his sense of self-preservation is a lot more finely tuned now.

[DanielS]

When I troubleshoot something that might literally blow up in my face, I plug the DUT into a switched power strip under my bench and use that to turn power on/off. This way, I'm ducking under my bench when applying power and if something has to go horribly wrong, it will usually be over before my finger is off the switch.

[smjcuk]

I take it outside and put it in the porcelain bath that lives in my back garden on an industrial extension lead and an RCD 

You are also a chump if you hold a cheap meter in your hand while probing a mains circuit.  That violates the basic safety practice of keeping one hand in your pocket when probing circuits that exceed SELV voltages to avoid the risk of getting a shock across the chest.

Definitely. This should be #1 rule. Always probe with one hand. Even on low voltage, low current circuits it stops probe slippage and accidental shorts that blow things up.

Also safety glasses.

[Lightages]

Do cheap meters explode when you abuse them?

It depends on the abuse, and the situation. One test with unknown conditions does not make a definitive test, nor does it give a definitive result. The test showed some indications of danger but that was dismissed. I am not surprised.

[nanofrog]

"The ONLY correct advice in online forums IMHO is to tell people to do things correctly. Don't poke multimeters into mains sockets UNLESS YOU KNOW WHAT YOU ARE DOING."

This is the heart of it IMHO. 

Bad habits picked up on low energy circuits can easily injure or even prove fatal on high energy circuits. And very easy to happen on a bench IMHO as most work isn't high energy (mistakes might blow stuff up, but not nearly the possibility of severe injury or death).

Safety glasses are also recommended, but also often ignored on a bench. I spent many years without any kind of lenses between my eyes and meters & DUT's. Now I rely on my prescription eyewear as they're polycarbonate.

If you need to hold the meter in your hand while probing fused mains circuits, then you should get a professional quality, appropriately rated one with a rubber sleeve on it as that adds extra protection where you are most likely to be gripping it, which can only help if it fails catastrophically.

This is also where the magnetic holders come in handy IMHO (not saying a substitute for a good rubber holster/boot, but in addition as it further aids in promoting the "keep one hand-in-pocket" safety rule).

[joeqsmith]

Apparently not. At least not in my initial crude non-scientific tests  (see pics below). BTW this is a continuation of the discussion in another thread which was totally hijacked starting on second page: https://www.eevblog.com/forum/testgear/the-uni-t-ut33c-or-d-how-good-they-are/15/

First abuse involved applying to a car type battery while set up for ohms measurment. No detectable damage. Meter still works fine in all ranges. Then tried it in milliamp range. This time meter stopped working. Later verified fuse was blown which is to be expected.

.....

No doubt playing around with mains is dangerous and unless you know what you are doing make no attempt. Grabbing the wrong wires or careless handling of a tool can be fatal. However IMO the fear mongers go a bit overboard with warning to never use cheap meters for anything except low voltage and low current. I'm convinced ratings manufacturers put on these are reasonable and personally would not hesitate to use them as designed. Certainly in the case of Harbor Freight or Uni-T products. Like any tool though misuse can have tragic consequences so be careful and make sure you know what you are doing.

I have been thinking about this as well .  I was unable to find any details about 1010 and am curious just what they really do require.   I have the 1010 standard coming. 

Seems like if you are going to do a review, and safety is part of what you want to talk about, you need to test them to this standard.  Maybe test them to failure and see what sort of head room they have.   

[Fungus]

I'm curious about why people would be arguing in favor of probing household mains circuits with multimeters.

Under what circumstances do you need to do that as opposed to just plugging in a lamp or using one of those volt sticks?

I'm sure there must be some but I think it will be a very short list.