Why multimeter safety matters

[Simon]

The bottom line is: you get what you pay for, and many people only look at the price

[Neilm]

can i buy this super quality HRC fuse, install it in my $100 Uni-T or even the $20 No brand DMM and considered it settled (safe)?

No -the reason you can't is that you don't know what other circuitry is there and if it is correctly rated and laid out. As I mentioned earlier I have seen over voltage protection devices that have been almost "short circuited" but poor layout - in that case a metal screw between the legs. This meant that if there was a transient it would jump from one leg to the metal screw and then to the other leg completely bypassing the protection.

Somthing that is quite often overlooked is the effects of the fuse blowing. When a fuse blows you have a lot of current flowing through an inductor (the leads). This then causes the voltage to rise and if there is poor layout this can jump the fuse protection and cause (or continue) an arc.

There is also the possiblilty that a poorly designed meter may have a fuse fitted that you can not get the correct rating HRC fuse for.

Neil

[Mechatrommer]

can i buy this super quality HRC fuse, install it in my $100 Uni-T or even the $20 No brand DMM and considered it settled (safe)?

No -the reason...

well, so maybe at least the word for me is "better than nothing" who knows one day, thats the only thing that can cause the arc. or at least i've fixed one flaw out of many. buying more expensive DMM is in order. but i think not soon enough

[joe72205]

shafri:

I would consider fused leads a safety upgrade for a cheap meter.  Even if the two leads were connected by a bolted-down dead short (like the 10A range of a multimeter), properly rated HRC-fused leads should eliminate arc flash in many cases.

The article i referred to at http://www.iaei.org/magazine/?p=556 makes this conclusion:

The resultant testing indicated that when properly applied, fused leads prove to be an effective method in preventing at least four of the five most common user error scenarios and most other internal failures. The only scenario the fused leads could not protect the user from was an extreme overvoltage condition. This was due to the voltage limitations of the fuse itself.

Note the author: "Steve Smith, CFEI, CEI, C-Tech, RME , is projects manager, regulatory affairs, with the Electrical Safety Authority of Ontario. ... Steve is the project administrator for ESA's Multimeter Safety Initiative. ."

At http://www.flukecommunity.com/forums/showthread.php?p=2820 Fluke seems to disagree:

It is additionally Fluke's position that a fused test probe is potentially more hazardous when used with any DMM  for the following reason. It is estimated that over 90% of most electrician measurements use the AC VOLTS functions of a meter. Current measures are generally less than 10%, more probably in the few percentage points. If the fuse in the test probe is damaged and not noticed or properly corrected, then false voltage measurements will occur which potentially create a shock hazard for the user.

In other words, they consider a measurement of Zero volts (due to blown fuse) a more relevant hazard because it looks like the circuit is de-energized.  To them, if you are using a Fluke meter you are already protected from arc flash, so there is no need to introduce the additional likelihood of an opened fuse in the test leads.

To me that means you should buy test leads with an indicator that shows a blown fuse.  And since wear and tear can also damage your test leads, make sure your working habits include a probe check against "known voltage" before you use them to ensure safe conditions are present.

[Zero999]

I would consider fused leads a safety upgrade for a cheap meter.  Even if the two leads were connected by a bolted-down dead short (like the 10A range of a multimeter), properly rated HRC-fused leads should eliminate arc flash in many cases.

The article i referred to at http://www.iaei.org/magazine/?p=556 makes this conclusion:

The resultant testing indicated that when properly applied, fused leads prove to be an effective method in preventing at least four of the five most common user error scenarios and most other internal failures. The only scenario the fused leads could not protect the user from was an extreme overvoltage condition. This was due to the voltage limitations of the fuse itself.

Note the author: "Steve Smith, CFEI, CEI, C-Tech, RME , is projects manager, regulatory affairs, with the Electrical Safety Authority of Ontario. ... Steve is the project administrator for ESA's Multimeter Safety Initiative. ."

Agreed.

To summarise: fused leads will make a cheap dangerous meter safer but it won't make it as safe as a decent meter.

[NiHaoMike]

I know a guy that was a witness of such thing. He was working with guy that used some cheap chinese no-name multimeter to check circuits in wiring cabinet. He accidentally left it on resistance range (probably after checking some fuses) and connected to live circuit. The meter was blown to pieces and the probes were glowing red and burned his hands.  If he would use a good certified meter he would see overload on the screen and nothing else would happen.

This is the difference between cheap crappy instruments and high quality ones.

Those things do happen in reality and safety matters the most.

What about the Extech that was rated to 600V CAT III but blew up on a properly operating 240V CAT II circuit? I'm sure it would have really blew up if it were connected to a CAT III circuit.

[alm]

What about the Extech that was rated to 600V CAT III but blew up on a properly operating 240V CAT II circuit? I'm sure it would have really blew up if it were connected to a CAT III circuit.

Did anyone claim Extech made high-quality meters? I certainly didn't. I consider Extech somewhere halfway between cheap crap and high quality.

I believe IEC61010 is self certified, although you may be able to get independent labs (like UL) to verify. So you have to trust the manufacturer to have done a good job. They can easily put 600V CAT IV on a cheap meter, especially Chinese manufacturers where there's basically no product liability.

[Kiriakos-GR]

I believe IEC61010 is self certified, although you may be able to get independent labs (like UL) to verify. So you have to trust the manufacturer to have done a good job. They can easily put 600V CAT IV on a cheap meter, especially Chinese manufacturers where there's basically no product liability.

I hate doing comments on this type of descriptions , but I had to do it ... ( common sense)

By slapping all day one country with one billion of people , you do not look as smart.

Simple because its not an smart act ...


1)  Its like the American KKK to attack on the new enemy ..
2)  By Insulting  the " number one "  currently financial and industrial source in the planet ,
you do not look any better ,  the opposite  ... looks like that there is  envy for those people.

3) Its more wise to blame an brand if you have an good reason , than all China !!!

4) I expect to meet and people from China, as members in this forum .. and so this generic expressions against China  it works out by causing an hostile climate .

I have more  than 1000 historical generic reasons , to blame the Americans and mostly their government acts , but I do no see how this is going to help the forum life ..

So my opinion is , any comment from now and on , it must to be specifically targeted to the one who worth's to be blamed.

   

[alm]

By slapping all day one country with one billion of people , you do not look as smart.

Instead of ranting, can you support the statement that I'm wrong with facts? I will happily change it to something like 'especially Chinese and American' if you can show that the practice of widespread fake certifications in the electronics industry and lack of product liability is just as common in other countries. I didn't claim that all or even most Chinese did it, so I'm not sure where your rant about insulting a billion people comes from, just that it seems more common in China. If you can show this to be incorrect, I will edit this statement.

The problem with name and shame is that many products are sold under many different brands, and brands may disappear overnight.

[Kiriakos-GR]

I will give an single fact ...   If your country was such large as China are ,  the bureaucracy and the low speed about running the country  ( law system ) , would be an good reason so the all country to look like as a giant airplane that has true hard times if it needs to turn left or right ..

Its all an matter of time ...  There is few that they take advantage of the holes of the law system in China.

But I bet that this is an international sport ..   

   

[Mambo]

I will give an single fact ...   If your country was such large as China are ,  the bureaucracy and the low speed about running the country  ( law system ) , would be an good reason so the all country to look like as a giant airplane that has true hard times if it needs to turn left or right ..

Its all an matter of time ...  There is few that they take advantage of the holes of the law system in China.

But I bet that this is an international sport ..   

   

And in that "matter of time" you could be dead !!!

Common Sence when measuring "High Energy Circuits" is clear. Stay away from Forums advice and do your research. Some brands are renowned for meeting or exceeding IEC tests.

What some of you are overlooking is that the fuse even a decent HRC fuse is not always the answer. Fused Leads (decent leads - most being made in the UK or Germany are an Answer), but CAT Rating in part  relates to "Voltage Creep" & "Flashover". Track spacing and board layering is a very real consideration.

Guys....if you buy a cheap car and it won't start "big deal". If you buy a cheap meter and you measure High Energy Circuits then "Good Luck" !!

[Mechatrommer]

The problem with name and shame is that many products are sold under many different brands, and brands may disappear overnight.

generically, we may call it "No Name" Brand. we'll have a heavier liability by pointing and shaming, you probably get shot in the head
Chinese products are well known for their "crappiness", they are cloners. even our local community "hibby jibby" nontech people got the impression. but yet, their products (ee or not ee) are humongous in quantity in our local and even international market, and people are like fungus scattered around looking for it, including... me, for some certain noncritical application and daily life needs that dont require complicated mechanical and electronical functionalities and short/temporary/panic time use.

[Mechatrommer]

China is quoted as "Sleeping Dragon", what we felt today is only coming from its calm breath. I'm afraid when its fully wake up, it will flash fires to Germany continents throughout the perimeter radius (what?!) including the Danaher thing. my crappy dusted 2cnts.

[Simon]

I'll repeat again, china is the big photocopier, when I was working for a man that wanted to import garments from china we received terrible items as samples. I know that you get what you pay for but if the manufacturers refuse to make rubbish and charge the extra for the good product there will be no problem.

Enforcing liability for a bad or dangerous product across continents is nigh on impossible. The safety certification can easily be faked and you will never catch them.

when Chinese manufacturers start acting morally maybe we can stop giving them the beating they deserve, and it's partly a cultural thing and you can say the same for any country with a poor population that will do anything it can to bring in the money.

The best thing would be that a variable import duty is applied to goods, work out what it is worth and if it's being imported so cheap it's silly then the European importer who is as much to blame can pay the difference in import tax, we will benefit by suddenly finding properly made items affordable and local manufacturers will be able to compete and give us what we should be getting while getting our unemployed back into work. and the now expensive rubbish will not be bought any more.

But then money makes the world go round and instead of trying to get European industry going again the governments try to lick the back sides of the chinese and I can't see how they are helping their country, probably their own pockets !

[Mechatrommer]

and i'll repeat again, politic sucks!

[Kiriakos-GR]

and i'll repeat again, politic sucks!

Its not politics .... its the American dealers who buy the cheapest crap and selling them at the American mega stores .

I do wonder WHY some people insist to close their eyes deliberately , at the who has the fault ...
WHO IS REALLY RESPONSIBLE !!

And I will say it wide open .... in anything related  with the American market imports ,
its responsibility of the Americans ... blame your self's ..  

[Simon]

@shafri it sure does, instead of people pointing the finger at each other they should point it at themselves

Yes Kiriakos, blame is on both sides but both are thinking of money alone

[Mambo]

Blame the User.  You need to take your own safety as your responsibility.   

[Mechatrommer]

Blame the User.  You need to take your own safety as your responsibility.   

i agree and add... you need to take your own knowledge as well. dont let luxury makes you ignorant.

[MrPlacid]

Blame the User.  You need to take your own safety as your responsibility.   

i agree and add... you need to take your own knowledge as well. dont let luxury makes you ignorant.

Dave was almost killed by one of his tested multimeters. I cannot always blame the user's carelessness or lack of knowledge in every instances.

[Simon]

unfortunately manufacturers often miss the obvious, or don't do proper testing

[Neilm]

And I will say it wide open .... in anything related  with the American market imports ,
its responsibility of the Americans ... blame your self's ..  

If you are in the Eu the responibility of ensuring a multimeter is safe is down to the company that first placed it on the market in Europe. This is the manufacturer (if manufactured in Europe) or the importer.

If it is unsafe then they can be hit with unlimited fines and / or jail sentances for the managing and technical directors.

Yours

Neil

[armandas]

And I will say it wide open .... in anything related  with the American market imports ,
its responsibility of the Americans ... blame your self's .. 

If you are in the Eu the responibility of ensuring a multimeter is safe is down to the company that first placed it on the market in Europe. This is the manufacturer (if manufactured in Europe) or the importer.

If it is unsafe then they can be hit with unlimited fines and / or jail sentances for the managing and technical directors.

Yours

Neil

In theory, you mean?

[Simon]

quite, we know of many blown up meters there have been but have we ever heard of the manufacturer being chased for it, the British trading standards office is well loaded with all sorts of complaints and there are more and more dodgy goods being made by the day, basically too many to have any control over. I personally would like to see half of ALL goods found on shop shelves refused importation because they are intentionally made cheaply with the view that they will be replaced when broken because they are so cheap. Things are no longer made to carry out a function, they are made to make money, the amount of useless 5 minute wonder items around is ridiculous, our STUPID and IGNORANT government preaches about how they want to make us more green yet they are giving full authorisation to a continual train of rubbish, into the country, into the consumers hands for 10 minutes, then into the bin and landfill.

We have this stupid WEEE thing in the UK but hec, I'm out and happen to remember that the stupid mouse i bought is broken after only 3 months and that i need another one, I haven't got the old one on me there and then to give back to the shop, and it will cost more fuel than the recycling of the mouse will yield to take it back later and hope they really do stick to the regulations and no just bin it.

I know that people will cry out with indignation if they have to pay twice as much for an item but that's because people are to damn stupid to see that they could pay twice as much and get an item that lasts 10+ times longer. I no longer own a CD player, because you cannot find one that will withstand a fair amount of use for more than 3 months, my dad has been through many, they now sit around as radios only because the laser diode has failed and just because this one cheap little part has failed because they use ones that are deliberately crap the whole unit becomes rubbish, how come we have CD players that are 15 years old and still work ?

And it's all valid for multimeters as well, the only people that can force change if the consumer cannot see the difference is the government, but then they are so scared of upsetting other countries (rather than looking after the people that elect and pay them) and lining their own pockets whilst not telling people that things are not right they let it go on.

[Kiriakos-GR]

Dave was almost killed by one of his tested multimeters. I cannot always blame the user's carelessness or lack of knowledge in every instances.

Yes, he had not see the sign " made in China "  = The land that had choose to terrorize the world with exploding multimeter s ..      

To all.

If the excuse about average products , its an good reason to throw rocks at this direction,
instead throwing them to its other , yes agree its preferable to blast the small China,
day and night.  ( space program - army - plus wealthy ) 

Dave had offered to us by his videos , all the basic knowledge that one consumer must have in order to make correct choices.

And I will totally agree here with @Mambo  

Blame the User.  You need to take your own safety as your responsibility.

1000+ to that ..

By the same way that the Europeans does not accept to eat the mutant farming goods "Made in USA"
and we choose the biological ones,  by the same style pick up and your DMM ..