Multimeters that do not appear to meet their safety specs.

[KD2FVM]

I thought the safety rating of the meter and leads (600V for example) meant that the user would be safe connected to (and protected from) voltages that high, not that the meter could measure that level. That said, a 250V fuse would be appropriate if the meters range was 250V and less. The fuse is to protect the meter, safety rating or class rating is an insulation safety rating and measure of dielectric strength.

[AVGresponding]

The fuse rating of 250V is a bit odd, when you find it in meters supposedly safe for measuring at higher voltages.

The fuse of course only sees a much smaller voltage, in normal conditions. However, in the event of the fuse blowing due to overcurrent, both the voltage rating and the breaking capacity come into play.
Essentially, the fuse only meets its breaking capacity if it's operating within its voltage range. Use it outside that range and you're going to get reduced protection.
In reality you're only going to see voltages larger than that if you make a mistake measuring current in a mains voltage circuit or similar.
I wouldn't trust or use a meter that has this type of fuse for this measurement.

[joeqsmith]

Some videos on multimeter safety.     

[joeqsmith]

Looks like he has a new video on safety. 

[rsjsouza]

Funny the issue with the decimal point on the Amazon meter. I just received my Fluke 101 that is missing both resistance multiplier indicators (M and k). I am working to convince the seller this is actually a defect.

[exit_failure]

Looks like he has a new video on safety. 

I think that what he says in his video is wrong or at least dangerously incomplete: Having a device tested by a certified testing house is fine and dandy but what's really important is what norms and standards it has been tested against. UL or any other similar testing institution will only do the test you ask them to do. So being UL listed may for example only mean that they tested it for environmental or fire safety or but not electrical safety and then the CAT rating may just as much be a lie as for any 5 dollar meter from aliexpress.
That means that the really important step is not finding the meter in some database but looking at the tests they actually performed.

edit: spelling and last sentence

[Lightages]

What one needs to keep in mind when thinking about multimeter safety is if it has a rating is that it actually has a testing house proof of its safety. CE is useless IMHO. Anyone can place CE on their product and all they are doing is hanging themselves out for liability should it actually not pass the CE directives.Some countries don't care or worry about the liability so it is a useless certification. If a product has a TUV, UL, CSA, or some other certification then the records of what criteria has been tested are available for the asking. This thread was started to help people understand the differences between safe (or safer) meters and pure BS. I am glad that has raised some awareness.

Oh yes..... I am back!

[tautech]

Oh yes..... I am back!

And nearly 2 years since you posted last. 

Settled back in the GWN ?

[Lightages]

GWN, Great White North? I am worried about that phrase right now.....

I was getting bored with my new 9-5 life so I decided to get active again. There will be videos!

[rsjsouza]

Welcome back, Lightages! You were missed.

[Lightages]

Thanks. I missed my interactions here too.

[dylanmitchell]

What companies always meet or exceed listed specs? Fluke, Agilent/ Keysight? Others?

Didn't see Fluke on the list but Amprobe was on there.

[Lightages]

If I were to try to name the companies that always meet listed specs, it would be a very short list. I would say, with reservation, that you could basically pick up an new meter from Fluke, Keysight, Brymen, Amprobe, Hioki, Yokogawa, and be sure you have a meter that actually is as "safe" as it claims. That is not to say that Flir, or others would be equally as good just that I don't have enough experience with them to say anything useful.

The point of this thread is not to say that the meters listed are unsafe in any circumstance. The point is to point out the flaws. Safety is not just about the meter. The idiot holding the meter has more to do with safety than does the meter. But if you trust a meter to do what it says and it can't and the specs are a lie then you need to know so you can adjust your behavior to be safer.

[ElektroHS]

If I were to try to name the companies that always meet listed specs, it would be a very short list. I would say, with reservation, that you could basically pick up an new meter from Fluke, Keysight, Brymen, Amprobe, Hioki, Yokogawa, and be sure you have a meter that actually is as "safe" as it claims. That is not to say that Flir, or others would be equally as good just that I don't have enough experience with them to say anything useful.

The point of this thread is not to say that the meters listed are unsafe in any circumstance. The point is to point out the flaws. Safety is not just about the meter. The idiot holding the meter has more to do with safety than does the meter. But if you trust a meter to do what it says and it can't and the specs are a lie then you need to know so you can adjust your behavior to be safer.

you are right... any electrical device is "dangerous" in case of incorrect usage. Therefore "end-user" should follow all rules to be safe... otherwise the result of incorrect usage even certified meters can be ended not so good.

[Andrew LB]

UL or any other similar testing institution will only do the test you ask them to do. So being UL listed may for example only mean that they tested it for environmental or fire safety or but not electrical safety and then the CAT rating may just as much be a lie as for any 5 dollar meter from aliexpress.

What you say is no longer the case. To have a meter UL listed it must adhere to the adopted IEC standards and include category overvoltage testing to ensure compliance. UL610101 and IEC610101

The old standards found in IEC348 and UL1244 did not require cat compliance.

[Rita]

Scanning through this thread there are repeated mentions of meters bearing the CE mark.  Not all CE marks are the same.



There's the The Conformité Européenne CE mark and the China Export mark.  I'll leave you to decide which is a copy of which and why they look so similar.

More info here: https://starfishmedical.com/blog/conformite-europeenne-mark-vs-a-china-export-mark/

[ksio89]

I'm in the middle of an online course about safety (Electrical Measurement Safety Online Course), and now I understand why I should keep Chinese DMMs away from mains or larger voltage sources, why measurement equipment from reputable brands such as Fluke or Keysight cost what they cost and why professionals pay more for safer equipments. It shows a lot of pictures of toasted DMMs due to low quality fuses, fake CAT ratings or cheap test leads. They even show what happens to a dummy in a arc flash blast and a interview with a electrician who survived such incident, very scary stuff.

According to the presentation by Fluke, around 15-20% of the cost of good electrical meters is composed by input protection, either manufacturing or testing, it's way more serious that I thought it to be. Guess I'll stick my Chinese DMM, which does not have a single certification mark, to use on low power electronics only.

[VK5RC]

I can't comment about meter safety but fully support issues with the user, even a well trained user having a bad day, distracted or in a rush can stuff up - I have, do and will again in the future, I appreciate other safety systems that I try NOT to rely upon - but appreciate their presence. One of the better comments I got from an experienced field technician - before you power stuff up, have a break then come back, look it over and re-check. Has been very helpful advice for me.

[Brumby]

Bump - just to demonstrate a point.

[floobydust]

Wavetek Meterman HD110 (2nd generation Taiwan build) with huge LCD 21mm or 3/4", circa 2000.
Trashbin find, I was repairing it and then saw this at the input jack board 
Spacings are maybe 1mm at best, in many places. Basically terrible. Rated 1,000VAC 1,500Vpk, 3kV for 10usec and has no formal agency approvals.

[siealex]

DT832 from an unknown Chinese manufacturer.
On the front panel I read: 200 mA MAX. On the PCB near the fuse: 0.5 A 250 V.
Now the fuse itself. A miniature fuse (approx. as a germanium diode), but its filament looks WAY too thick. No marking at all.
Several AA batteries, a 10 A meter, this fuse...
2.5 A: no reaction at all.
4 A: no reaction, only some heat.
4.6 A: the filament starts glowing red, but does not melt. 30 seconds (I couldn't resist that heat any more) - no melting.
The resistance of test leads did not allow me to push higher currents into the fuse.
Then... FIVE!!! AA alkaline batteries in series (typically ~10..12 A short-circuit current), a piece of thick wire, no meters. The fuse tripped in TWO SECONDS!
Is it a 5 or 6 A fuse? A slow-acting fuse typically melts in several seconds at 2x load. A 0.5 A fuse should melt in two seconds at 1 A, not 10 A.

WHY??? Now it's unsurprising that the first thing burning in these meters is the PCB or resistors on it, then the ADC chip, the switch contacts, but not that damn fuse.