Why did my multimeters blew up? (AC voltage) - Page 1
Forum section: electronics / beginners

author: evlo
author_rank: Contributor
timestamp: March 29, 2024, 07:27:15 pm
content: I tried to measure AC VOLTAGE, 100% sure multimeter was set to AC voltage, i even have eye witness.I tried to measure between L1 and L2 - result: spark, house elcb down, mutimeter does not measure. Hopefully fuse, it was my good meter.So now, second meter AC voltage, unfussed between L1 and PE, same thing, spark, house main elcb down.I was fault finding my installation, fault was not connecting Neutral wire to the distribution rail. I was doing measurements on the wires coming right from the electrical company meter. Nothing after that was connected.3 phase 230V connection.

author: Grandchuck
author_rank: Super Contributor
timestamp: March 29, 2024, 07:30:35 pm
content: Can you supply a photo showing the leads plugged into the meter?

author: schmitt trigger
author_rank: Super Contributor
timestamp: March 29, 2024, 07:31:53 pm
content: Please provide meter's brand and model number.A photo of the damage inside would be nice, although not strictly necessary.

author: CaptDon
author_rank: Super Contributor
timestamp: March 29, 2024, 07:40:26 pm
content: Probably had the leads connected to meter COM and AMP inputs. Surely did something wrong! If the meter was indeed set to A.C. Volts and not A.C. Amps then you had the meter leads plugged into the wrong holes.

author: IanB
author_rank: Super Contributor
timestamp: March 29, 2024, 07:42:25 pm
content: Quote from: evlo on March 29, 2024, 07:27:15 pmThis is not sufficient to avoid mishaps. You also need to ensure the test leads are plugged into the right sockets on the meter. Some good meters will warn with an alarm if you plug the leads into the wrong sockets for the measurement.

author: pcprogrammer
author_rank: Super Contributor
timestamp: March 29, 2024, 07:48:54 pm
content: Quote from: CaptDon on March 29, 2024, 07:40:26 pmSounds like the most likely fault. A normal multimeter set to AC volts and connected properly should not cause a short.Some newer ones have mechanical protection to prevent such a fault. My old Agilent has an electronic warning setup for this. With the test lead inserted in the A connection it will buzz and show Aerr on the screen when dialed onto anything other then the A settings. Does not give the warning on the mA connector though.

author: golden_labels
author_rank: Super Contributor
timestamp: March 29, 2024, 08:12:40 pm
content: Also mind that amplitude between any two phases is around 600 V in 3-phase 230 V network. I did see DT83x family members rated for less than that.

author: evlo
author_rank: Contributor
timestamp: March 29, 2024, 08:16:18 pm
content: well i did measure 230V and even 400V in some wall sockets before, and pretty sure i did have it plugged in com the normal "20A" socket. I do not think there are special slots for the leads for AC volts.The good one is owon ow18Epretty sure it was connected to com and 20A and than sparksIt is possible that the times i did measure the 400V and 230V I did use different meters, well it is very probable. Now I'm very confus.I did tried the com + V but that was ... too lateI guess maybe just the probes might have burned out.Other meter is this onehttps://shop.fkt.cz/digitalni-multimetr-fk8550-ean7120272-skupsf0000000005.php- here I would guess that I used the "V", but at the moment I was very confused about how everything is behaving, so I'm not sure.This one does have backlight toggle, no timeouts, etc. As interesting quirk.I usually use owon and have leads in "20A" and COM "holes" (ports?) and it does continuity and voltage etc. for DC in that setup, maybe I should use the other hole for that and that 20a is for current measurement, really, but until now it always worked ....Also I'm still very confused, how 230v LED "bulb" can turn on when it is only connected to N and L1 lead, but the N leads is never ever connected to anywhere final, like PE, just to the air. Well it does turn on for a bit and then dies. But still, i measured, between N and L1, hopefully correctly that time about 0,8V, so how can it light up?

author: Veteran68
author_rank: Frequent Contributor
timestamp: March 29, 2024, 08:54:51 pm
content: Quote from: evlo on March 29, 2024, 08:16:18 pmThen that is exactly your problem, as others have pointed out. You had the leads plugged into current measuring socket, not the voltage socket (the socket to the far right). By measuring from live to PE or live to neutral, you've shorted out the meter. Hopefully you only blew the fuse(s).

author: evlo
author_rank: Contributor
timestamp: March 29, 2024, 09:06:41 pm
content: But still weird that when I use it for continuity, ohms, etc. I would not use the slot that is marked for that, maybe I just got confused by what people here are writing. Should it even measure ie. DC resistance when connected to "20A"?

author: Gyro
author_rank: Super Contributor
timestamp: March 29, 2024, 09:17:48 pm
content: Probably a really good (actually, overdue) time to read the manual. It's all set out clearly there.Edit: It's not possible for you to have been measuring continuity, voltage, etc. via the 20A jack as that would be connected to the COM jack by the very low resistance high current shunt and fuse.

author: ArdWar
author_rank: Frequent Contributor
timestamp: March 29, 2024, 09:29:22 pm
content: Quote from: evlo on March 29, 2024, 08:16:18 pmThis doesn't make any sense at all.Granted electrometer-type current sensing in theory can do that but I'm pretty confident that 99.999% of handheld DMM ever made is not that.I also pretty confident that 100.00% of them can't do voltage and continuity from 20A port.Some serious misunderstanding is definitely on play here.

author: BeBuLamar
author_rank: Super Contributor
timestamp: March 29, 2024, 09:42:57 pm
content: Replace the fuse in the meter then try to measure resistance with it and see.

author: wraper
author_rank: Unknown
timestamp: March 29, 2024, 09:45:27 pm
content: Quote from: BeBuLamar on March 29, 2024, 09:42:57 pmThat fuse is only relevant to current range. The rest is completely separate. Condition of the fuse does not affect any measurements other than current.

author: IanB
author_rank: Super Contributor
timestamp: March 29, 2024, 10:03:47 pm
content: Quote from: evlo on March 29, 2024, 08:16:18 pmThis is ahugemistake on your part. You donotever want to plug the test lead into the 20 A socket, or even the μA mA socket, unless you are an expert who knows exactly what you are doing. Youalwaysplug the red lead into the VΩHz socket. You should put tape over the other sockets to prevent you from plugging into them again.

author: tunk
author_rank: Super Contributor
timestamp: March 29, 2024, 10:14:46 pm
content: And stay far away from high voltage until you have learned far more. It can be fatal.

author: amyk
author_rank: Super Contributor
timestamp: March 30, 2024, 01:42:58 am
content: I like how everyone immediately identified, and the OP confirmed, the cause of this.The 20A and uA mA sockets are for measuring current only, not voltage.Please do read a bit more on how your meter works before using it!

author: CaptDon
author_rank: Super Contributor
timestamp: March 30, 2024, 01:56:31 am
content: Unbelievable how anyone would plug a lead into the current jack to measure volts!!! Buy a couple more meters and measure how many OHMS your power company has. Second thought......DON'T!!!

author: xrunner
author_rank: Super Contributor
timestamp: March 30, 2024, 02:08:01 am
content: Quote from: tunk on March 29, 2024, 10:14:46 pmA good "tip for young players" as has been said around here.

author: themadhippy
author_rank: Super Contributor
timestamp: March 30, 2024, 02:51:45 am
content: QuoteNot just high voltage,but high energy .12v sounds harmless enough,until its able to kick out a few hundred amps,it might not kill you,but at the very least your going to need some clean underwear if you accidentally short it out

author: BennoG
author_rank: Frequent Contributor
timestamp: March 30, 2024, 08:00:55 am
content: The previous measurements of the OP where probably done between the 2 outermost jacks.so the 20A and the Volt Ohm connector.Because the 20A is connected to the COM the measurement worked as expected.He later used the com jack and blew the meter.Benno

author: pcprogrammer
author_rank: Super Contributor
timestamp: March 30, 2024, 08:04:25 am
content: Quote from: wraper on March 29, 2024, 09:45:27 pmYep, but I guess BeBuLamar was hinting that it would show impossible to measure resistance or continuity with the leads in 20A and COM connections, like the OP was sure he had done before.The OP can count his blessings that nothing bad happened while measuring directly after the power companies meter on two phases. Fused at maybe 64A it will have been quite the blast. The fuse in the meter might not have helped against damage caused by the flash, but maybe the fuse contained it. Only way to know for sure is to open up the meter and see.A simple test to see if the meter survived is to plug the leads in the proper connectors, COM and V..., The two connections on the right side of the meter and turn it on to continuity and see if it beeps when the probes touch each other.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: March 30, 2024, 02:22:03 pm
content: Quote from: CaptDon on March 30, 2024, 01:56:31 amNot unbelievable at all. First, there is the ignorant, who have not read the manual or know much about electronics or DMM's. Second, there is simple user error or absent mindedness. This mistake is so common that most of the "better quality" meters have a protection against exactly this mistake. A few have a mechanical interlock, which covers those banana plug holes when the meter dial is in a non-current measurement mode. But far more common is that the DMM turns on the beeper when a cord is jacked into an amps socket when it should not be. The first meter I bought with this feature (Dynatec 112) is now in my possession for over 30 years, and in that time it has saved a bunch of meter fuses.

author: GLouie
author_rank: Regular Contributor
timestamp: March 30, 2024, 04:06:22 pm
content: Confirming, as BennoG noted, that on some meters you can get volt and ohm readings with the probes in the high Ampere jack and the V-Ω jack. An Aneng 8008 will do this, but the EEVBlog-Brymen beeps an error with this configuration. OP thinks it was COM and 20A, but must be mistaken.

author: BeBuLamar
author_rank: Super Contributor
timestamp: March 30, 2024, 04:11:23 pm
content: Quote from: pcprogrammer on March 30, 2024, 08:04:25 amI don't know about the OP meter but I have blown the fuse of my Fluke 87V many times by forgetting to put the test lead back to the correct jack and the meter survived. Just the fuse is gone.

author: Gyro
author_rank: Super Contributor
timestamp: March 30, 2024, 07:28:33 pm
content: Quote from: GLouie on March 30, 2024, 04:06:22 pmYes, putting one probe in the highest current jack and the other in the V-Jack would give readings. As previously noted, the high current jack is naturally connected to COM via the fuse and shunt, this probably wouldn't be noticed apart from maybe on the lowest resistance range.It makes no sense that the OP would do that though, short of liking to plug the probes into the jacks in the bottom corners of the meter. It still requires moving a probe to the COM jack to measure current - most likely, he did that. I think it can only be put down to lack of knowledge and failing to read the instructions.

author: radiolistener
author_rank: Super Contributor
timestamp: March 31, 2024, 12:14:16 am
content: Quote from: evlo on March 29, 2024, 08:16:18 pmMains can provide much more than 20 Amps, so this is the reason why it burned your DMM. Say thanks, that it didn't killed you.If you want to measure voltage, you're needs to connect probes to Volts socket, not Amps socket.

author: coppercone2
author_rank: Super Contributor
timestamp: March 31, 2024, 01:12:51 am
content: the short circuit current of the mains can be as high as 2000A in the worst casesNotice what your breakers are rated for, its KA. That is kilo ampers. The circuit breakers are like 5kA rated to give you a safe margin.That is why you have a 30 dollar fuse in the multimeter, incase you do this inside of the electrical panel in a commercial building.Gossen meters block the amps jack with a mechanical slider thingy, those are the best for total noobs doing electricity works (not electronics). I can't stand them in the lab though, awful, you need to be wearing a leather tool belt to make use of a gossen IMO.

author: Fredderic
author_rank: Regular Contributor
timestamp: March 31, 2024, 03:02:26 am
content: Quote from: Doctorandus_P on March 30, 2024, 02:22:03 pmIn defence of "the young players"; Also worth noting that everyone who's looked in a fuse box, knows that there's two or three different amp rated fuses for different circuits, usually even more different values in a car. Never different V's, though. And on every product, the V's are mostly always the same, and only matters to make sure it's not somehow a product from an incompatible region, you learn it's the W's you have to be aware of, you probably know that the A's make up the W's (and those V's too, they're just there to help you convert between W's and A's), and probably that it's the W's that will overload your power board. So knowing what the A's are at all, probably makes you smarter than average, doubly so if you actually understand and use them instead of the W's. So you see the A's on the meter, and of course you know to use the right one! And they did.

author: joeqsmith
author_rank: Super Contributor
timestamp: March 31, 2024, 03:30:48 am
content: Quote from: coppercone2 on March 31, 2024, 01:12:51 amNot according to the IEC standards. There is a reason they rate the fault currents on safety fuses much higher.

author: 44kgk1lkf6u
author_rank: Regular Contributor
timestamp: March 31, 2024, 04:03:43 am
content: Quote from: CaptDon on March 30, 2024, 01:56:31 amIt should be fine. My indecisive power company goes back and forth between -1k to 0L ohms.

author: 44kgk1lkf6u
author_rank: Regular Contributor
timestamp: March 31, 2024, 04:05:12 am
content: Quote from: joeqsmith on March 31, 2024, 03:30:48 amWhat number do they say it is?

author: Xena E
author_rank: Frequent Contributor
timestamp: March 31, 2024, 07:58:31 am
content: Quote from: 44kgk1lkf6u on March 31, 2024, 04:05:12 amHow long is a piece of string?Icu is the figure that is quoted on devices for safe breaking protection. Whatever the instantaneous fault current it has to be interruptedSAFELY.Check out the local regulations, however a clue to that question is the breaking capacity rating printed on your MCB or RCD etc.,6 - 10kA is normal for a final circuit in a domestic property in the UK. Some large MCCB are commonly available to safely interrupt 200kA.One poster here put "in defence of the newbie". The fact is in these circumstances when things go horribly wrong because of abject arrogance and ignorance you don't have to defend the newbie because they are dead.If people are willing to piss around with high energy circuits without even READING THE MANUAL for the test instrument they are trying to use, they are then nominating themselves for a Darwin award.There are good "electricians" meters available that have no current range on them at all, any in service current measurements of high energy circuits, should for safety be made with non contact methods.Remember RTFMRegards,Xena.

author: MrAl
author_rank: Super Contributor
timestamp: March 31, 2024, 09:02:31 am
content: Quote from: evlo on March 29, 2024, 07:27:15 pmNot sure if anyone said this yet but there are a few reasons how this could happen.First, the meter was really set to measure AC current. That would cause this kind of problem.Second, the meter is set to AC voltage, but the leads are plugged into the wrong terminal holes on the meter.Third, the leads are not meant for those meters but are a special type.There could be other reasons too.On some meters the terminal holes are all the same color so you have to be very careful where you plug the leads in.

author: IanB
author_rank: Super Contributor
timestamp: March 31, 2024, 09:07:35 am
content: Quote from: MrAl on March 31, 2024, 09:02:31 amOP already explained they plugged the leads into the 20 A and COM sockets on the meter, "as is normal for such measurements". The exploding meter is therefore no mystery.

author: Zero999
author_rank: Super Contributor
timestamp: March 31, 2024, 09:44:47 am
content: Quote from: Doctorandus_P on March 30, 2024, 02:22:03 pmI confess, I've done it before. but through absent mindedness, rather than ignorance. I'm used to using a meter with a warning and the one time I didn't I blew the fuse because someone had been using it for current before and had left it plugged into the current socket. Fortunately it wasn't mains, just a current limited bench supply and no harm was done, other than an expensive fuse. I learned a lesson and am more careful now.

author: BeBuLamar
author_rank: Super Contributor
timestamp: March 31, 2024, 09:45:21 am
content: the mystery is the OP claimed that he can measure resistance using the same jacks 20A and COM.

author: radiolistener
author_rank: Super Contributor
timestamp: March 31, 2024, 02:19:18 pm
content: Quote from: joeqsmith on March 31, 2024, 03:30:48 amCAT III and CAT IV is tested for source impedance 2 Ω.For 300 V line test transient voltage is 4000 V for CAT III and 6000 V for CAT IV.6000 V / 2 Ω = 3000 Amps for transient pulse.Working current for CAT III and CAT IV is 300 V / 2 Ω = 150 Amps (45 kW).This is for high current load socket like kitchen electric stove which is usually rated for 10 kW power.But usual home wall outlet is CAT II, which is tested for source impedance 12 Ω.For 300 V line test transient voltage is 2500 V for CAT II.2500 V / 12 Ω = 208 Amps for transient pulse.Working current for CAT II is 300 V / 12 Ω = 25 Amps (7.5 kW).

author: joeqsmith
author_rank: Super Contributor
timestamp: March 31, 2024, 02:39:19 pm
content: Quote from: 44kgk1lkf6u on March 31, 2024, 04:05:12 am61010-2-033:2012 shows for category IV, the typical short circuit current >> 50kA.The short-circuit current is calculated for a 1 000 V line-to-neutral voltage and theminimum loop impedance. The values of loop impedances (installation impedances) donot take into account the resistance of the probe assemblies and impedances internalto the measuring equipment. These short-circuit currents vary, depending on thecharacteristics of the installation.

author: joeqsmith
author_rank: Super Contributor
timestamp: March 31, 2024, 02:45:45 pm
content: Last time fault current came up, I took the time to measure a few of my home outlets for one of the members here. Sadly, they were not able to measure theirs so we only have a few data points.https://www.eevblog.com/forum/testgear/trashy-meters-redux/msg4835948/#msg4835948

author: joeqsmith
author_rank: Super Contributor
timestamp: March 31, 2024, 05:03:05 pm
content: Leads in wrong positionhttps://youtu.be/IzwN8yibjjA?t=848Other dumb mistakes like reading the resistance of live mains...https://youtu.be/IzwN8yibjjA?t=1135While they run the surge test and talk about the what ifs of an arc flash event if something were to flash over, they never show any testing. The following was taken from an article on arc flash testing that describes the setup.Quotehttps://www.ecmag.com/magazine/articles/article-detail/safety-lets-blow-it-arc-flash-testing

author: alm
author_rank: Super Contributor
timestamp: March 31, 2024, 05:17:39 pm
content: Quote from: radiolistener on March 31, 2024, 02:19:18 pmThis is the source impedance for the transient test which will also include inductance. Is there a specification for source impedance at mains frequency?

author: coppercone2
author_rank: Super Contributor
timestamp: April 01, 2024, 02:54:28 am
content: well i hope they don't let this guy near the IV before a few classes'But in the house it should be around the 2000 mark I think. And less in a distant outlet, I think I ran the numbers to what it should be in the garage and it was slightly lower because of the inductance and resistance of the wire.I think its like 3% impedance in north america for the transformer infront of your house.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 01, 2024, 01:03:39 pm
content: Quote from: coppercone2 on April 01, 2024, 02:54:28 amAssuming we are talking about the typical 110V outlets in the USA, none of mine are even close to 2kA. The ones I measured were all under 500A. Consider that one outlet I checked was very close to the distribution panel. The problem is, it's only one data point. Maybe there are cases where a standard 110 outlet in the USA would be higher. Maybe my meter has 100% error.

author: CaptDon
author_rank: Super Contributor
timestamp: April 01, 2024, 01:16:37 pm
content: The O.P. also stated "In the 20A Normal Jack"!!! For 99% of technicians and 99% of their tests the '20A' jack IS NOT the 'normal' jack!!

author: schmitt trigger
author_rank: Super Contributor
timestamp: April 01, 2024, 01:28:15 pm
content: I am pretty sure that by now, the OP has learned the lesson.As others have mentioned, damaging a multimeter by applying the AC mains to an incorrect range, is a common newbie mistake.It was worse with analog meters, with its rotary selector. I myself as a curious youngster damaged a Radio Shack analog meter, attempting to measure AC volts while in the resistance range. Not only several components burned, but the meter’s needle pegged with such force that it was completely bent.My relative was upset but not completely surprised. That is the reason he loaned me the inexpensive Radio Shack but wouldn’t allow me to touch his expensive Simpson 260.

author: themadhippy
author_rank: Super Contributor
timestamp: April 01, 2024, 01:50:52 pm
content: QuoteFor prospective fault current the distance to your fuseboard dont really matter,its how far the supply transformer is that makes the difference.

author: bdunham7
author_rank: Super Contributor
timestamp: April 01, 2024, 02:10:38 pm
content: Quote from: themadhippy on April 01, 2024, 01:50:52 pmThat may be true in the UK, but things are different in the US. Transformers are often quite close and the fault currents at the panel can be many thousands of amps, but 50 feet of 14-2 wiring and 120V will limit the fault current to under 500A.

author: BeBuLamar
author_rank: Super Contributor
timestamp: April 01, 2024, 02:15:15 pm
content: Well the OP use the 20A jack to measure voltage so the fuse blown. That's no mystery but the OP said he can measure resistance with the 20A jack I wonder how? I don't know about the OP's meter but I have blown fuse on the Fluke meters 87V and 287 by doing exactly what the OP did and only the fuse was blown and some damage to the test probe but the meters were fine.

author: IanB
author_rank: Super Contributor
timestamp: April 01, 2024, 02:23:05 pm
content: Quote from: themadhippy on April 01, 2024, 01:50:52 pmHome wiring is a little different in the USA. Homes often have a larger footprint than UK homes, and there can be long runs of Romex in the walls and attic spaces from the panel to the receptacles. This, combined with the lower voltage, means that the possible fault current at a room outlet can be much less than the fault current at the panel.

author: IanB
author_rank: Super Contributor
timestamp: April 01, 2024, 02:27:29 pm
content: Quote from: BeBuLamar on April 01, 2024, 02:15:15 pmIf you were to put the black lead in the 20 A socket and the red lead in the V-Ω-Hz socket, then measurements of voltage and resistance would continue to work normally.

author: BeBuLamar
author_rank: Super Contributor
timestamp: April 01, 2024, 03:10:46 pm
content: Quote from: IanB on April 01, 2024, 02:27:29 pmOh thank you! Now I understand why the OP think the 20A jack is normal. I think he thinks the 20A for measurement stuff up to 20A so a lead is always there.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 01, 2024, 07:00:34 pm
content: Quote from: bdunham7 on April 01, 2024, 02:10:38 pmCorrect and I assume coppercone2 is in the USA which is why I provided the link to the data I collected. To add to your post, we also do not use a ring. Everything is point to point (inside the house). Our distribution transformer is located in the neighbor's yard and I would not run fault tests across the two bus bars located inside the house. I had opened the distribution box for inspection after lightning struck a tree in the front yard. You can get an idea what it looks like here:https://youtu.be/40TaqXOIrHo?t=150