Author Topic: Multimeters that do not appear to meet their safety specs. (updated frequently)  (Read 156418 times)

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Offline tinhead

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BK Precision 2709B/2712  CATIII/600V CATII/1000V  Ceramic fuses used on both current ranges rated at 500V with no warning on meter. (Submitted by Lightages, reviewed by Dave Jones and 2712 by carloscuev)


user manual speaks about "0.5 A/500 V & 10 A/600 V fast blow ceramic fuses", on the PCB you can clearly
read exact the same values, and they are of course installed as well. So where is the problem?
I don't want to be human! I want to see gamma rays, I want to hear X-rays, and I want to smell dark matter ...
I want to reach out with something other than these prehensile paws and feel the solar wind of a supernova flowing over me.
 

Offline Lightages

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The latest CAT specs require that all input jacks be rated for the same rating. They also specify that any design or part of the meter must meet the maximum rating of the meter. In other words lower value fuses than what the meter is rated at may not be used. Technically it may have passed its rating tests under the older rules but it does not.

It would also be much safer for the user to know that the meter has a lower rating on its current jacks without needing to remember it. It should have been marked on the face so that anyone picking up the meter can see.

I am not saying that it is not a good meter, just that it does not meet current day safety requirements under the latest CAT rating rules.

Quote
The intent of this thread is to provide at least a partial list of multimeters that are to be assessed on their physical and feature merits rather than to rely on their stated CAT ratings for assumption of safety.
 

Offline Spunky

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All this fear about multimeters blowing up and I hardly ever hear anyone talk about fused test leads. Look in any sparkies tool bag and you'll find a bunch of HRC fused leads. I have probably £200-£300 of leads in my bag right now. Even a cheap meter can be made a lot safer by just changing the leads.

Also my main meter is a clamp, so I will never have leads in the wrong jacks because they don't exist.

That said I do make a judgement on what meters go in the electrical kit and what stays on the electronics bench based on what I see inside them.
 

Offline Sigmoid

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I just blew a 500mA fuse on my BK Precision 2709b... Thankfully it originally came with a replacement in the package, lol!

Anyway, since it's really easy to hamfist these into blowing, I'm out to get a replacement... Should I try to get a 1000V one in the same form factor? Any good sources for these? :)
 

Offline Lightages

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Yes you can use a 1000V fuse. It will be an "upgrade" of sorts but it does not change the rating of the meter. It would be helpful to know where you are to give you  place to buy the fuses.
 

Offline Sigmoid

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Sorry, you're right. New York City, US. XD
 

Offline Lightages

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Well you could call up http://www.tequipment.net and ask them. Or you can go to http://www.testequipmentdepot.com/amprobe/accessories/fuses.htm and select a fuse that matches what you want. You can also buy them on ebay.
« Last Edit: August 04, 2013, 07:13:14 am by Lightages »
 

Offline ElectroIrradiator

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Should I try to get a 1000V one in the same form factor? Any good sources for these? :)
Yes and yes.

440mA.
11A.

Note there is a misprint on one of those pages. These fuses are meant to be able to interrupt 1KV *DC* without exploding, which is in a whole other league compared to the flimsy glass fuses we use for the AC mains. That is why they cost a bundle. Not sure if these fits your meter though.
 

Offline rexxar

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I'm sure this isn't surprising, but I bought an Elenco M-2666K multimeter kit that is supposedly rated for 1kV. Unsurprising, there is no isolation slots on the PCB, and in fact there's about 5mm between the voltage input and the common trace. Same deal with the other Elenco meter mentioned here, there's a standard 250V glass fuse for the mA range, and the 20A range is unfused, though there's footprints for it on the board, which I populated because I had a holder handy. I wouldn't trust this thing for mains voltages, but I've got another meter for that, so it's okay. I can upload pics if anyone's interested.
 

Offline madsci

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We can add the Mastech MS8229 and it's badge-engineered brother the Protek 6300.

Claims CAT-III 600V and CAT-II 1kV but contains a 500V ceramic fuse like the  Mastech 8218.

I have not performed a thorough teardown of mine. I'll have to see if I can find it.
 

Offline safetyfirst

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Extech perhaps don't deserve to be given such a critical assessment.

I have an EX510 with what looks like a revision 2 board, and better use of space around the probe terminals, with no possibility for any component to short.

The Fuses are both 1000V SIBA HRC

One of the fuse mounts for the 0.8 Amp fuse looks soldered on the wrong way around, so they probably should really get rid of the factory they are using to resolve the remaining issues as it seems clear this is where the problem lies (and they may have done that by now as this is probably at least a few years old I would guess as it was old new stock I got cheap (under $50)

It was also able to forward bios a white LED

They really should use a better selector on the front though.

The EX510 is spec'd to handle 20A, but the pic shows a 10A fuse.
 

Offline Lightages

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The EX510 is spec'd to handle 20A, but the pic shows a 10A fuse.

This is actually not a problem. 10A fuses will withstand 20A for a short time. Also, the amperage rating of the fuse is not an indication of its safety. What the fuse needs to do is break a current and voltage as defined in in the meter's CAT rating.
 

Offline WhiteWolf

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CE marking is a joke and a farce, there is the "C E" mark, the real one and there is the "CE" mark that means china export (well we know what they hope we think it will mean).

The CE mark for safety will remain a joke unless local regulatory bodies start enforcing it. There have not been many cases in the UK that I am aware of where non-compliant meters were removed from the market. When they are, the issue should be published in as many trade issues as possible to make the fact that they are taking action as public as possible.

What is the state in other countries? I know that several non EU countries have complained about non compliant meters on sale.

Neil

In Sweden and Finland, back in the 90's the real "CE" mark was a important thing on most of the electrical equipment for installation in buildnings and electrical/electronic equipment also. But then after 2000 it has becoming less and less important. And today I can see in stores, both in Sweden and Finland electrical/electronic stuff without the "CE" marking.
"OT: And even sometimes no safety markings at all on eletrical equipment for building installation."

On my electronic engineer education at the university we got taught that the "CE" marking is just bullsh*t and we shouldn't even bother to look after it. Just because of the "China Export" thing. And when I worked at a well known company who are developing and producing car battery chargers. They went after the "CE" criterias but they didn't take them too seriously. Tuv and other criterias where more important to meet.
 

Offline safetyfirst

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According to the User Manuals and specs, all of the following Amprobe products are currently designed to 61010-1 2nd edition, but it appears that only the AM160a meets the 3rd edition (at least the fuse voltage req't on the A & mA/uA circuits).

AM220  Cat3-600V but F1 & F2 are rated 250V (ding)
AM240  same

AM250  Cat3-1000, Cat4-600 but F1 & F2 are rated 500V (ding)
AM270  same
The AM270 is a re-packaged Brymen BM817a

AM140a Cat3-1000, Cat4-600 but F1 & F2 are 600V (ding)
AM160a Cat3-1000, Cat4-600 with F1 & F2 rated at 1000V (great!)

Based on the criteria used for the AM140a, then the AM250 and AM270 should be moved to the suspect list.
I have a call into Amprobe about this awaiting a reply.
But I am going to swap the fuses in my AM270 to 1000V versions.
 

Offline delmadord

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Probably known info but maybe it will be handy for someone:

TENMA 72-7740 uses only glass fuses.
 

Offline Lightages

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According to the User Manuals and specs, all of the following Amprobe products are currently designed to 61010-1 2nd edition, but it appears that only the AM160a meets the 3rd edition (at least the fuse voltage req't on the A & mA/uA circuits).

AM220  Cat3-600V but F1 & F2 are rated 250V (ding)
AM240  same

AM250  Cat3-1000, Cat4-600 but F1 & F2 are rated 500V (ding)
AM270  same
The AM270 is a re-packaged Brymen BM817a

AM140a Cat3-1000, Cat4-600 but F1 & F2 are 600V (ding)
AM160a Cat3-1000, Cat4-600 with F1 & F2 rated at 1000V (great!)

Based on the criteria used for the AM140a, then the AM250 and AM270 should be moved to the suspect list.
I have a call into Amprobe about this awaiting a reply.
But I am going to swap the fuses in my AM270 to 1000V versions.

You have valid points. Even the BM867 ha the same issue as the AM140 vs AM160. I sincerely believe that installing better fuses in this case brings them back up to spec. The lesser fuses must be a cst cutting measure for the less expensive model. I don't like it.

The BM257 has a similar situation. The A fuse is rated for 600V but the mA fuse is only rated for 500V. Not a big discrepancy but till not right with the latest CAT rating requirements. I will be buying fuses to correct any meters like this to make them have the right fuses.

With that being said, adding better fuses does not necessarily make the meter safer for higher voltages. The rest of the circuit board and design might fail at a lower voltage anyway.
 

Offline Lightages

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The TENMA 72-7740 is a re-branded Uni-T UT60C. I have yet to see a Uni-T multimeter that probably meets its CAT ratings except for the German version of the UT61E and possibly the just recently released UT139C. All other Uni-T meters are suspect and are so are their re-brands.
 

Offline ElectroIrradiator

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Not sure if this has been mentioned on the forum before: This oldie but goodie video demonstrates why the old hands try to instill people should buy a quality DMM for high voltage/high energy work. Video by VDE in Germany, recorded during a test for VDE certification. The meter failed the test. :P

The meter manufacturer had marked the meter with a fake VDE certification mark without actually having the model tested by VDE. Yet that didn't prevent somebody else sending the meter to VDE for testing. >:D
 

Offline Lightages

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Thanks for that video link. I would like to know what voltage and current they used in that test.
 

Offline ElectroIrradiator

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No idea. There is a silly number of relevant DIN standards, and I don't have access to them. I'm speculating they used 1KV DC at a significant energy level (though less than 20kA), as that would be the most severe test while staying within CAT III spec.
 

alm

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IEC61010 calls for much larger transients. From memory I believe that a CAT III 1000 V meter should be tested with an 8 kV transient from 2 ohm source impedance. Not sure about the duration or charge. Fluke has a table in one of the app notes (ABCs of DMM safety?) on their website.
 

Offline Lightages

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alm

You remember correctly.
 

Offline anwe

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The Brymen 820 series do not appear to meet their rating either.
I did a quick teardown on my 827, and it has KTK-1 and KTK-10 fuses which AFAICT are rated for 600 VAC.
I'm not 100% sure here, could it mean they meet the previous revision of the spec?
The 820 series is listed in the manual as having 600 VAC fuses, so Brymen is completely honest about this fact.

The 520 series do meet the spec according to the manual.
The markings on the PCB indicates that both series share the same PCB, upgrading the fuses may be all that it takes if there are no differences in MOVs et.c.
(all models 821-829 and 521/525 are listed with copper island indicators, there's a solder blob on the island matching the actual product number).

/Andreas
 

Offline chiefengineer

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PeakTech 2010 DMM

CAT II 1000V rated

Self recovery fuse 250V 200mA over current protector on milliamps range
I have used my one for quite some time and it shows heat damage near the amps input jack. Maybe caused by some transistors on the milliamp range overheating.

I don´t feel save using this.



heat damaged case


the transistors next to the fuse may overheated



more heat damage around these transistors
 

Offline orjan-

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On the brymen BM867, the printed cat4 1000V rating on the multimeter is only for the V/ohm++ input. The manual clearly states that the A/mA inputs is rated for cat4 600V AC/300V DC. That's why the fuses are not rated 1000V. Many of the brymen multimeter's have different cat ratings for the A/mA input and the V/ohm++ input.

From the manuals:
BM867 Terminals (to COM) measurement category:
V :   Category IV 1000 Volts AC & DC
mA?A :   Category IV 600 Volts AC and 300 Volts DC
A :   Category IV 600 Volts AC and 300 Volts DC

BM869 Terminals (to COM) measurement category:
V / mA?A / A :   Category IV 1000 Volts AC & DC

BM857 Terminals (to COM) ratings:
V :   Category III 1000 Volts AC & DC, and Category IV* 600 Volts AC & DC.
A / mA?A :   Category III and Category IV* 500 Volts AC and 300 Volts DC.

BM859CF Terminals (to COM) ratings:
V / A / mA?A :   Category III 1000 Volts AC & DC, and Category IV* 600 Volts AC & DC.

TBM811, TBM812 & TBM829 Terminals (to COM) measurement category:
V :   Category IV 1000 Volts AC & DC
mA?A :   Category IV 600 Volts AC and 300 Volts DC
A :   Category IV 600 Volts AC and 300 Volts DC

TBM811XEX, TBM812XEX & TBM525 Terminals (to COM) measurement category:
V / mA?A / A :   Category IV 1000 Volts AC & DC

BM250(251,252,255,257) Series:
Terminals (to COM) measurement category:
V :   Category II 1000V, CAT III 600V and CAT IV 300V AC & DC.
mA?A :   Category III 500Vac and 300Vdc.
A :   Category III 600Vac and 300Vdc.

Link to some of the brymen manuals:
http://www.brymen.com/product-html/0000-User/
 


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