DMM safety - Page 1
Forum section: electronics / testgear

author: Traceless
author_rank: Frequent Contributor
timestamp: December 01, 2022, 10:13:03 pm
content: Does anyone know which safety standard guarantuees that a meter is not going to blow up (given it is used in the specified environment, but accounting for hazards like transients), reglardless of the mode selected? (Or in other words how do I know that a meter behaves like the fluke in the video below and not like the little CEN-Tech. [Time-Stamp 5:57])I guess it would be covered one of the IEC/EN61010-XXXX norms? Is there some way to find out if the meter has actually been tested against said standard and is not falsely advertised with specs it does not meet?https://youtu.be/OEoazQ1zuUM?t=357

author: bdunham7
author_rank: Super Contributor
timestamp: December 01, 2022, 10:35:08 pm
content: Quote from: Traceless on December 01, 2022, 10:13:03 pmFrom a previous discussion:https://www.eevblog.com/forum/testgear/hear-kitty-kitty-kitty-nope-not-that-kind-of-cat/msg3714598/#msg3714598One of the problems is that even if the company or seller submits a sample to a certification lab for testing, there's no guarantee that the meter you receive will actually be manufactured the same way as the sample. So even if you verified that the claimed certification is valid and appropriate, you still have no way of knowing if what you buy is compliant and safe. So who do you trust?

author: ogden
author_rank: Super Contributor
timestamp: December 01, 2022, 10:49:08 pm
content: Quote from: bdunham7 on December 01, 2022, 10:35:08 pmReputable manufacturers usually do not go route of changing standards because in case of many safety incidents whole existence of company may be at risk. So, simple rule - do not buy safety-related equipment from disposable companies.

author: Martin72
author_rank: Super Contributor
timestamp: December 01, 2022, 10:58:49 pm
content: QuoteSerious known brands and the prices.A Meter which meets the safety standards couldn´t cost under 100 bucks (only example given), otherwise it will be a lie.

author: Traceless
author_rank: Frequent Contributor
timestamp: December 02, 2022, 12:15:16 am
content: Quote from: bdunham7 on December 01, 2022, 10:35:08 pmI do see your point - and of course I can not know that what I buy is compliant and safe but what I can at least try to do is to filter our stuff, that is at best questionable due to a missing or non-genuine certification. If an independent, reputable certification lab tests a product against a safety standard at least someone has put the product to test and verified that it meets that standard. Also the vendor was at least willing to spend money for that certification process. If they wanted to maximize profit no matter the costs they could have slapped the china export mark on the meter and called it a day. Of course a company could have made a modified product for certification and sell cost reduced ones with less protection but still slap the label on them.@bdunham7, @ogden, @Martin72At that point the question indeed is who should I trust? Fluke because everyone on the internet says so and they have the most expensive meters? Maybe Brymen, but then again their BM235 costs under 100$ so it can't be safe? I mean certification is by far not perfect but do you really think reputation/cost is a better indicator for safety?

author: bdunham7
author_rank: Super Contributor
timestamp: December 02, 2022, 12:50:07 am
content: Quote from: Traceless on December 02, 2022, 12:15:16 amOne advantage you have being in Germany is that anything sold by a German retailer is a bit more likely to not be grossly non-compliant due to stricter regulations and enforcement. Beyond that, brand and reputation are all that you have. Based on experience and previous forum discussions, I'm pretty sure that the following companies will not deliberately sell you a bogus meter: Fluke, Gossen, CA/Metrix, Brymen, Klein, Brymen/Greenlee, Yokagawa, Hioki, Testo, UEI/Kane, Megger, Fieldpiece. There may be others and I apologize to anyone I left out. Simpson and Triplett are companies that I don't believe have mismarked meters, but many of their products may have no ratings at all. I don't want to claim that any specific meters are likely not to comply, but I personally would avoid anything from Uni-T, Extech, Mastech, Aneng, Zoyi, Kaiweets, CEM (and anyone that rebadges them, like Southwire). BK Precision is iffy--they are a re-badger and some of their stuff is good, some may be less good.You can check this thread for examples where meters appear not to meet their safety markings:https://www.eevblog.com/forum/testgear/a-list-of-multimeters-that-do-not-appear-to-meet-their-claimed-safety-specs/The whole safety thing is often discussed, but in reality not many people are injured by blowing up their meter in a home environment, even on mains. Long ago I 'blew up' my unfused Mastech-built Harbor Freight meter by the time-proven method of testing a wall socket with the lead in the amp jack. Blew the traces off the board, burned up the test lead and wall socket and tripped the breaker. Both I and the meter survived (with repairs) but the wall socket didn't. I now have a meter for electrical work that makes this impossible (Fluke 116).

author: Gregg
author_rank: Super Contributor
timestamp: December 02, 2022, 01:08:05 am
content: QuoteThe only one you should trust is your own well informed judgement taking into account all of the situations applicable to your needs. A good start would be to review joeqsmith’s videos on YouTube and his posts here discussing possible choices. I’d trust Joe over any corporate marketing any day. Dave also did some very good DMM teardowns where he points out differences between good and bad design and components.Most DMM blowups are due to user error, namely having trying to measure high power voltage with the settings on current mode. Proper fuses can keep you safe but still may damage the meter via improper use.

author: Fungus
author_rank: Super Contributor
timestamp: December 02, 2022, 07:00:54 am
content: Quote from: Traceless on December 01, 2022, 10:13:03 pmYes.Quote from: Traceless on December 01, 2022, 10:13:03 pmLook on the back for logos of independent testers. eg. There's UL, CSA, TUV...Normally a manufacturer can provide you with a certification number which you can look up on the websites of the testers. Some even stamp the number on the back of the device.Edit: There are some worthy Japanese brands like Hioki that don't do third party testing but you can trust them to not lie about the rating printed on the front.

author: Fungus
author_rank: Super Contributor
timestamp: December 02, 2022, 07:17:31 am
content: Quote from: bdunham7 on December 02, 2022, 12:50:07 amYep. Look at how many utter garbage multimeters Harbor Freight have given away in the USA.Quote from: bdunham7 on December 02, 2022, 12:50:07 amYep. If you're working on mains, use a meter that's designed for that job.No multimeter relieves you of the responsibility to be careful. Real safety comes from procedure, not from the device, eg. wear gloves when testing anything industrial.

author: Fungus
author_rank: Super Contributor
timestamp: December 02, 2022, 07:22:59 am
content: Quote from: Traceless on December 02, 2022, 12:15:16 amFluke makes asub-$50 meterthat you buy on Aliexpress.Brymen meters are as safe as any. They make some meters with higher ratings than any Fluke.(Fluke doesn't make any CAT IV 1000V meters, Brymen does...)Quote from: Traceless on December 02, 2022, 12:15:16 amSome companies have both.

author: Traceless
author_rank: Frequent Contributor
timestamp: December 02, 2022, 08:21:37 am
content: Thanks everyone for the feedback.@Gregg: I've seen wuite some of joeqsmiths reviews they are indeed awesome.The reason I'm asking my original question is that I'm currently looking at a meter that noone, including Joe has tested yet. TheBrymen BM089which according to its datasheet complies with:UL/IEC/EN61010-1 Ed. 3.0, IEC/EN61010-2-033 Ed. 1.0, CAN/CSA C22.2 No. 61010-1 Ed. 3.0, IEC/EN61010-2-032 Ed. 3.0 & IEC/EN61010-031 Ed. 1.1:Measurement Category III 1000V & Category IV 600V AC & DC.At the first glance it is a pretty nice meter from a reputable vendor. One of the special features this meter has is a 3-phase rotation measurement function, so basically you can hook it up to a three phase mains supply and measure the phase sequence (it shows a little R with a clockwise arrow around, if L1, L2, and L3 are connected to the corresponding inputs). If you look at the meter closely it also has a test-lead-based DC µA range which happens to be the function right next to the phase rotation measurement. Also because it is a clamp meter it seems to have no fuse. So what is going to happen if that thing is attached to a 3-phase mains supply and someone accidentally turns the knob one position to the left (DC µA)? At first glace that seemed like pretty horrible design safety-wise. If you look at the specs more closely though, they say that the DC µA range of that meter has a burden voltage of 3.5mV/µA aka. 3.5kV/A which is pretty high. Still DC µA will create a short across the mains and there is a lot of energy involved...So the question is basically does any of the aforementioned safety-standards imply that they actually tested the meter with all three leads connected to mains and put it in the µA range and it didn't blow up?

author: mqsaharan
author_rank: Regular Contributor
timestamp: December 02, 2022, 09:52:01 am
content: There is no mention of fuse in the user manual (http://www.brymen.com/images/ProductsList/BM080_List/BM080-manual.pdf) as well. They may be using a PTC instead of a fuse there. I think it is best to ask the manufacturer directly about the safety of the meter and the user in case of user error. Also, the manual states that the third terminal is for 3 phase rotation measurement only. So, ask them about that too how well it is protected against misuse. Brymen is very responsive as per a few members who have contacted them. I'm sure they'll explain better.Also, their design choice of using 2xAA for a chip with 2.5V low battery threshold (2.85V low battery for Cap and Hz), in my opinion, is a poor choice. There is a little mistake in the manual regarding 2 captive screws on the battery cover. The picture on the next page clearly shows that there will be only one. Anyway, not important.I particularly liked the high sensitivity mode for phase rotation measurement for motors. It is a unique feature.Edit: Oh, I forgot to mention that in my humble opinion, it is always best to use fused probes like Fluke FTP with industrial mains regardless what meter someone is using.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 02, 2022, 10:08:46 am
content: The BM080 is a clamp meter and thus has no classical shunts for the current measurement and thus no fuse for the current ranges. The voltage/resistance ranges are normally not protected by a classical fuse, but more like PTC (the transition to polymer fuses can be a bit fluent) and resistors as series elements. These are not meant to be changed and thus not mentioned.A clamp meter is usually safe in the current ranges, however they are normally limited to higher currents and most for AC only.P.s.:The DC-µA range may indeed use a PTC of similar element as fuse. So it would not hard clamp the voltage with diodes as most other meters do when measuring current, but respont with a high resistance. Chances are the burden resistance would go up (at least with a little delay) when overloading.

author: mqsaharan
author_rank: Regular Contributor
timestamp: December 02, 2022, 10:13:59 am
content: He is talking about uADC function, which is, as per manual, using input jacks for measurement. Thus the concern regarding the safety of the user and meter when there is no mention of fuse in its literature.

author: Traceless
author_rank: Frequent Contributor
timestamp: December 02, 2022, 10:54:44 am
content: Quote from: mqsaharan on December 02, 2022, 09:52:01 amThat sounds like a good idea I'll ask Brymen themselves - cant hurt. Then again I'm pretty sure they would never write back "Yeah, sorry we screwed up on this one, sorry", even if they did. So I'm still interested in additional less biased opinions on the forum.Quote from: mqsaharan on December 02, 2022, 09:52:01 amYes that is not great but can probably be mitigated a bit by using 1.7V lithium-AAs.Quote from: mqsaharan on December 02, 2022, 09:52:01 amThis is indeed a cool feature but not the only nice trick that meter has up its sleeve. It also supports 1-lead-contact-phase detection and thus can replace avoltage-testerand enable you to find the phase even without access to a ground terminal.Quote from: mqsaharan on December 02, 2022, 09:52:01 amFused probes would be nice, but I took a look at the Fluke FTPs and they cost almost twice as much as the Brymen including accessories.Quote from: Kleinstein on December 02, 2022, 10:08:46 amThe high burden voltage I mentioned above also points in that direction. Still my gut-feeling about this still is more along the lines of: "This could be safe-ish, maybe?"

author: J-R
author_rank: Super Contributor
timestamp: December 02, 2022, 11:03:14 am
content: I have the Amprobe-branded version of the BM089 and sent some reasonable voltages through the uA DC mode as a test. I think their rating limit of 1,000VDC/VAC is correct, but above that it may have to sacrifice a component or two. I didn't try it...My opinion on these safety ratings is that they are not something you should trust on a daily basis, no matter what some governing body states. Even measuring typical mains voltages a homeowner should have safety glasses along with insulated gloves and shoes, then only use one hand to take the measurement. If you go around using two hands to shove test leads into sockets on a regular basis without a second thought, then the one day you do it out of habit with wet hands and some test leads that maybe have some cracks in the insulation, you're going to have a bad day.Of course if you're in the industrial space, you are going to be schooled up on proper PPE for this stuff, so honestly the ratings on the test equipment don't even matter for your personal safety, IMHO. Multiple protections will have to fail before there is an incident. So maybe measurement device protections, PPE, good habits, and maybe even a buddy to get help just in case!

author: BeBuLamar
author_rank: Super Contributor
timestamp: December 02, 2022, 11:23:34 am
content: Quote from: bdunham7 on December 02, 2022, 12:50:07 am

author: 2N3055
author_rank: Super Contributor
timestamp: December 02, 2022, 11:43:53 am
content: Quote from: Traceless on December 02, 2022, 08:21:37 amNo it will not create a short on mains. It's internal resistance is equivalent to 3500 Ω in that mode. At 240 V that is 70mA. And there are protection circuits to limit current going into the meter. Brymen says it is protected up to 1000V.And amount of energy in mains voltage is directly related to where are you measuring. That is what CAT categories are all about.Your socket inside normal office or apartment will pretty much make medium loud "poof" when shorted, without much drama.Doing that on 400A master fuse going into the building (with wires as thick as your finger) will be different story..I would hope people would not play there if they are not certain what are they doing.It is all about available short circuit current...

author: mqsaharan
author_rank: Regular Contributor
timestamp: December 02, 2022, 11:58:43 am
content: Quote from: Traceless on December 02, 2022, 10:54:44 amYou specifically mentioned 1.7V lithiums. I guess you are going to discharge them a bit or put a schottky or germanium diode in series with them. Because some meters like Brymen 235 don't accept them. At least they'll not leak.Quote from: Traceless on December 02, 2022, 10:54:44 amI haven't used many meters personally but a few meters that I have used so far that have high input impedance can do that trick (shows higher voltage when input jack is connected to phase than to the neutral).Quote from: Traceless on December 02, 2022, 10:54:44 amSorry about that. I used it only as an example and suggested only for industrial work. There are a few other manufacturers in Europe offering fused probes, fused leads and even small fused attachment that connects directly to the meter and accepts normal probes.

author: HKJ
author_rank: Super Contributor
timestamp: December 02, 2022, 12:27:22 pm
content: Quote from: mqsaharan on December 02, 2022, 10:13:59 amA uA range can/will piggy-bag on the same protection as the ohms ranges, it is basically the same current. Only disadvantage is that the burden voltage is higher than on a traditional uA range with a fuse and diodes.

author: BeBuLamar
author_rank: Super Contributor
timestamp: December 02, 2022, 12:48:20 pm
content: Our company issued the 116 to some of our people. One of the meter behaves like bad test leads. It doesn't read anything but the the display looks fine. Just like you're not connecting it to anything. I sent it to Fluke and they gave me a new one but I wonder if the problem was caused by someone trying to measure 480V while the meter is in microamps mode?By the way when I called Fluke they said they can't repair the 116. Just send the bad one to them and they send me a new one.

author: mqsaharan
author_rank: Regular Contributor
timestamp: December 02, 2022, 01:07:17 pm
content: Quote from: Kleinstein on December 02, 2022, 10:08:46 amQuote from: HKJ on December 02, 2022, 12:27:22 pmThank you both, Kleinstein and HKJ for reminding me that. It had actually slipped my mind. Sorry, I didn't notice your P.S. before, Kleinstein. I missed it.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 02, 2022, 01:18:32 pm
content: Quote from: BeBuLamar on December 02, 2022, 12:48:20 pmNormally the meters should withstand a connection to mains and similar voltage even in the ohms or similar protected low current mode. However there can still be aging. Some of the PTCs specify a limited number (e.g. 100 or 1000) of cycles they can withstand, probably voltage dependent.With such lower cost DMMs there is not much that can be repaired (e.g. the rubber holster, stand and battery compartment, possibly known weak points / series defects). Ideally a repair would need strickt testing, a new calibration and safety tests. This alone can cost more than the meter. Chances are Fluke would not like poorly repaired meters to come back to the market - so they probably get destroyed and not send to India or Vietnam for a cheap repair.

author: BeBuLamar
author_rank: Super Contributor
timestamp: December 02, 2022, 01:31:42 pm
content: Quote from: Kleinstein on December 02, 2022, 01:18:32 pmThe 116 is made in Malaysia (not India and I don't think Fluke has factory in Vietnam yet). Age? It's less than 1 year old that's why Fluke gave me the replacement meter. The 116 doesn't have lifetime warranty like the higher end ones. It was made less than 1 year old because Fluke determined that the meter is in warranty just by the serial number. I don't have to give them any receipt or anything like that.

author: bdunham7
author_rank: Super Contributor
timestamp: December 02, 2022, 02:42:31 pm
content: Quote from: BeBuLamar on December 02, 2022, 11:23:34 amThe input in this case is virtually the same as in the Lo-Z/Auto mode, so there would be no more chance of burning up the PTC(s) than if you were checking the 480V circuit in the range you typically would start with anyway.Also, FWIW, the warranty is 3 years.

author: Fungus
author_rank: Super Contributor
timestamp: December 02, 2022, 02:43:03 pm
content: Quote from: Traceless on December 02, 2022, 08:21:37 amIf Bryman says that in the user manual then it's a safe bet that it met those standards.Quote from: Traceless on December 02, 2022, 08:21:37 amYes.

author: Fungus
author_rank: Super Contributor
timestamp: December 02, 2022, 02:46:00 pm
content: Quote from: Traceless on December 02, 2022, 08:21:37 amThe uA range is for measuring flame sensors so it will have a very limited range, hence the high burden voltage.(and also the safety rating - the internal resistance in uA mode isnowhere nearzero so only a low current will pass).

author: BeBuLamar
author_rank: Super Contributor
timestamp: December 02, 2022, 02:46:11 pm
content: Thanks! I didn't know but when I called Fluke and told them they said it's underwarranty. Just have to send the old one for them to destroy they send me a new one.

author: tautech
author_rank: Super Contributor
timestamp: December 02, 2022, 05:51:20 pm
content: Quote from: Fungus on December 02, 2022, 02:46:00 pmMaybe you have never built and needed to measure the quiescent draw of a micro power device.

author: Fungus
author_rank: Super Contributor
timestamp: December 02, 2022, 06:16:11 pm
content: Quote from: tautech on December 02, 2022, 05:51:20 pmI've built a lot of coin cell powered devices that lasted for years.OTOH I wouldn't want "flame sensor test" to be the only uA range on my multimeter, and I certainly wouldn't want that huge burden voltage.

author: BeBuLamar
author_rank: Super Contributor
timestamp: December 02, 2022, 06:27:07 pm
content: Actually I bought the meter because the guys need to measure flame rod current and I can measure flame current well with very high burden voltage (the voltage that feed the flame rod is about 400V). That turns out to be a good things because I am afraid that someone will try to measure voltage with the selector set at microamps.

author: Traceless
author_rank: Frequent Contributor
timestamp: December 03, 2022, 11:29:29 am
content: Quote from: mqsaharan on December 02, 2022, 11:58:43 amI didn't know that Brymen meters had problems with Lithium batteries. I'll check back with Brymen and ask them if those are okay for that meter.Quote from: mqsaharan on December 02, 2022, 11:58:43 amI have noticed that too but not sure if I would trust this to work reliably every time - sometimes the readings are pretty similar. My favourite trick so far was remove the leads from the DMM touch one of the terminals with a disconnected lead and then use the NCV against the lead to detect the phase. While that works, the brymen's single probe voltage detection is more convenient. Of course it is not an indispensable feature, you could also always use a regular DMM + one of thoseflim-flam-sticks, I really like the swiss-army-knife nature of that particular brymen model it just replaces a lot of dedicated tools.Quote from: mqsaharan on December 02, 2022, 09:52:01 amThanks for mentioning it I've never thought about fused probes. As you said those are probably well suited for industrial high energy work. For regular CAT II/III stuff it is probably overkill plus those probes can also be a safety hazard if you are not super diligent with testing your equimpment beforeeverymeasurement. If the probe fuse is open circuit and you think a circuit is not energized when it is still live there might be an upleasant surprise around the corner.