About Multimeter Safety.. - Page 1
Forum section: electronics / beginners

author: ABHIRAMSHIBU
author_rank: Contributor
timestamp: December 09, 2015, 11:47:02 am
content: I was using cheap-ass multimeters for quiet a long time now. So many of the blew up instantly by checking invertor ( Square Wave) voltage. Some of them blew up when I accidentally measured high voltage 50- 230 v sign wave with wrong dial.For example when I was repairing a UPS I had to look the continuity and also the output voltage. After measuring continuity I forget to turn the dial to volts and connect the probes and guess what happened ( It blew the holly crap out of the nob contacts ).Now I changed my meter to UNI-T UT33D (again cheap-ass but more costly than the other meter. The other meter costs about 150 inr where this meter costs abut 650 inr.) Now there is no problem measuring square wave, of course its not true rms, but we can compare the value though.I think I saw a video were David told that these meters especially UNI-T is a peace of crap ( No safety and reliability at all ).Now coming to my questionI am planning to buy a good multimeter may be fluke.... I cant afford that much price but any way I will buy one. My question is thatif I use a fluke decent multimeter to check the voltage of an ac circuit, with the dial set to diode mode what will happen. Will the fuse blow or the multimeter will be killed( I like to know will I survive also lol )I'm very young 17 years, I have not learned electronics via classes. I just experimented, done research in internet and learned. Any way I have basic knowlage of electronics. And I like building stuff from scratch and also repairing.Thanks in advance....

author: Gyro
author_rank: Super Contributor
timestamp: December 09, 2015, 12:37:19 pm
content: It sounds as if you are maybe a little accident prone when it comes to working on high powered circuits, you should maybe become a bit more cautious (check settings twice etc) when probing high voltage / high energy circuits. That will hopefully let you enjoy a long life beyond your current years.The thing about higher quality meters is not that they will not get damaged but that they are a lot less likely to damage YOU. Yes, if you put them across the mains when on a current range you will (reasonably safely) blow an internal fuse. Things like diode and resistance modes are protected by clamps, ptc thermistors etc. I don't think the manufacturers would guarantee that the meter will survive (especially more than once), there are too many possible situations, it might, but there are limits. If it does fail then it will do so safely though (no exploding switch contacts).

author: ABHIRAMSHIBU
author_rank: Contributor
timestamp: December 14, 2015, 01:24:50 am
content: Yes I got it now....Thank you for your awesome reply

author: VK5RC
author_rank: Unknown
timestamp: December 14, 2015, 01:35:29 am
content: One comment I got years ago and has saved me a few times, is, for a 'big' measurement, set it up, then walk out the room, (if really big have a cup of tea!) come back and recheck before switch on, for me it is mainly rf gear that is easily fried by too high a level or dc and it could cost a few grand! Personal safety is also a factor especially in power supplies.

author: EEVblog
author_rank: Unknown
timestamp: December 14, 2015, 02:05:24 am
content: Quote from: ABHIRAMSHIBU on December 09, 2015, 11:47:02 amNo the fuse will not blow. The fuse is only on the Amps jacks.Any decent multimeter (not just Fluke) will survive measuring voltage on the diode range.

author: tautech
author_rank: Super Contributor
timestamp: December 14, 2015, 02:11:00 am
content: Haave a study of this thread to see the robustness of DMM's:https://www.eevblog.com/forum/testgear/hear-kitty-kitty-kitty-nope-not-that-kind-of-cat/

author: Brumby
author_rank: Unknown
timestamp: December 14, 2015, 03:57:50 am
content: I don't work on high energy circuits that often, so when I do I get rather conscientious in checking meter ranges and where the probes are plugged in - but I will admit I gave my very first multimeter (20Kohm/volt moving coil) a terminal zap which resulted in a very nice vapour deposition of copper on the inside of the rear cover.The concern everyone has with a newcomer wrangling their first multimeter is that, the knowledge andunderstandingto be able to use it appropriately andsafelyis lacking experience. Feeling like a technician because you've got the gear is the same as feeling you're ready for Indianapolis because you bought a car. Just because your $9.95 meter has 600vac range printed on the front cover does NOT mean you can go shove the probes into a 230v power point willy nilly.One example I had was with a friend of mine sometime last century. He was into music, guitars and Marshall gear. Among other things, I did equipment repairs, a master volume mod (on valve gear), developed a high power attenuator, played around with wireless links and so on. He was always one to aim for 'the best' - and was extremely particular about the care of his equipment. (If you've ever dealt with guitarists, you will know how protective they are of their guitars. I believe it's not uncommon for the guitars to be referred to as their 'wives'. Well, this guy was an 8 or 9 on the anxiety scale.)One day he asked me what the best multimeter was and, at the time, Fluke was the name that came to mind that I thought would be suitable. I told him they were pricey, but they have a good reputation. So he shells out about $600-$700 (I think) and gets himself a Fluke. When I found out, I was crying inside and just atinybit jealous. I knew he would read whatever manuals were included, but I was concerned about his lack of understanding in using it properly.A couple of weeks later, he called to say there seemed to be a problem with his multimeter - so I went over to check. I asked him what he was he doing and he told me he was "Just checking the 240v current".To all those now cringing .... Yes, he did.Inside was one very open circuit fuse - and no signs of any damage whatsoever. This is just once example of why quality gear is worth the money. Another is that the operator was protected - as much as the equipment was able to. Replacing the fuse saw everything come good - and I made it a point to offer some fundamental instruction on how to use his multimeter.

author: MrSlack
author_rank: Frequent Contributor
timestamp: December 14, 2015, 08:52:24 am
content: I've been lurking here for a couple of years and the mulimeter lore is quite scary. YMMV but I saw a Fluke 77 blow up spectacularly many years ago. They're not safety goggles. Any idiot can kill and maim themselves with anything given the right level of competence.As a mere averagely funded person, I'm a fan of cheaper meters. Most measurements are within a certain tolerance anyway (most of our components are 5-20% tol for R/Cs typically, crazy amounts for transistor parameters). For me, that's a few UT33A units. If you need anything better get a bench top 5-6 digit model (keysight if you can afford it).The weak points on all meters are non-autorangers (these blow up all the time, especially old VOMs), bad quality probes or damaged probes (yup 240v 1mm from your fingers on £2 probes with random insulation - nope) and ammeter shunts (boom) I find. I stay away from anything that is likely to throw more than 5A through a shunt and use a clamp or an external shunt and voltmeter. If its high voltage (>mains) use a resistor divider built into the circuit; keep the problem far away from you.As for wrong mode, this hasn't ever happened to me. Never probe around live circuits. 99% of explosions happen due to accidentally probing something or shorting something with the probe tip. Always power down, attach, power up, measure, power down. Label your meters with the test point and the mode (masking tape+pencil is good). Before power up, check that the labels are true. Think before you measure too. Oh and check your probes aren't damaged before you use them every time.Spend some cash on an isolation transformer, some decent probes and some safety glasses if dealing with high energy circuits first. Better investment if you don't want to kill or injure yourself.

author: dmills
author_rank: Super Contributor
timestamp: December 14, 2015, 09:44:01 am
content: Worst multimeter blowup I had was a slipped probe on a 24V supply, said supply being a 3000 amp hour marine battery bank with less then 2M of 35mm^2 cable between it and where I was probing (I was trying to measure charging current from a lowish current float charger).I think it was the arc as it ate the probe tips that caused the real pain, so no working on low voltages does not always save you (A note particularly relevant given the number of hobby projects using Lipo and similar technology)...Regards, Dan.

author: saturation
author_rank: Super Contributor
timestamp: December 14, 2015, 06:51:47 pm
content: Many of the best meters in the linked review, the Brymen and Chinese market Fluke, are reasonably priced and I think the Fluke 100s series is sold locally in India.Quote from: tautech on December 14, 2015, 02:11:00 am