A  high voltage measurement blew my multimeter. - Page 1
Forum section: electronics / beginners

author: J4e8a16n
author_rank: Regular Contributor
timestamp: June 10, 2017, 12:56:58 pm
content: Hi,Can't read voltage....I don't see anything burned in the (ordinary) multimeter pcb.What are the odds?Would I loose my time working on it?)JPD

author: negativ3
author_rank: Regular Contributor
timestamp: June 10, 2017, 01:36:30 pm
content: Fuses ok?Multimeter model?Picture of PCB top & bottom...

author: Brumby
author_rank: Unknown
timestamp: June 10, 2017, 01:54:02 pm
content: Make and model?Replacement cost?

author: Nusa
author_rank: Super Contributor
timestamp: June 10, 2017, 02:12:44 pm
content: Verify battery is good, and didn't happen to die at that moment?What were you measuring when it died? How big a voltage are we talking about?

author: Brumby
author_rank: Unknown
timestamp: June 10, 2017, 02:20:08 pm
content: Quote from: J4e8a16n on June 10, 2017, 12:56:58 pmCan you read anything else?Resistance?Current?

author: P90
author_rank: Frequent Contributor
timestamp: June 10, 2017, 04:20:48 pm
content: kind of vauge. Could have been in the wrong range selection, wrong jack, etc. what meter, what voltage?

author: J4e8a16n
author_rank: Regular Contributor
timestamp: June 10, 2017, 07:16:13 pm
content: Battery goodfuses goodscreen no goodnothing gives up except the soundMastercraft Canadian Tire on sell 30$1000 volts Igniton coilWould not loose my time on it.

author: bktemp
author_rank: Super Contributor
timestamp: June 10, 2017, 07:21:48 pm
content: It looks like there is no overvoltage protection at all at the voltage input.Try removing the rotary switch and look for arc damage. If the input voltage has arced over to a neighbouring contact, it has probably fried the ADC.

author: vltr
author_rank: Contributor
timestamp: June 10, 2017, 08:11:08 pm
content: Quote from: J4e8a16n on June 10, 2017, 07:16:13 pmIt's done. Ignition coils usually put out well above 1000 volts. 10kV-30kV is much more likely especially if open circuit.http://www.autoserviceprofessional.com/article/91646/Ignition-coils-What-every-tech-needs-to-know?Page=5

author: brainwash
author_rank: Frequent Contributor
timestamp: June 10, 2017, 10:04:28 pm
content: Beginner trap. I also tried to measure a fly swatter, those are usually >3kV.My multimeter was a pretty old model, had a lot of the chips separate, multiplexer, ICL... Never managed to get it running again.Long story short, it's probably dead. Next time use a 10:1 or 100:1 voltage divider.For reference, if the display is showing useless stuff on ANY range, the main IC is probably dead.

author: dave_k
author_rank: Frequent Contributor
timestamp: June 10, 2017, 10:35:30 pm
content: Kaboom!Looks like vaporised PCB trace.

author: nuno
author_rank: Frequent Contributor
timestamp: June 10, 2017, 11:47:27 pm
content: I've seen a cheap chinese whose probes acted as a fuse. There were no external damage though, so it took a while to find out what was wrong (broken probe wire inside the plastic encapsulation, no visible external damage at all).

author: brainwash
author_rank: Frequent Contributor
timestamp: June 11, 2017, 01:37:37 am
content: It's always fun and games until the real fuse becomes YOU. There's less than a mm separating you from the DUT on those cheap probes. A lot of the times, a soldering point is just at the start of the probe's plastic body. So you're almost making contact with your wrist. Sorry to say, those things are just not suitable for anything >100V. However, I use them 90% of the time for low voltage stuff.

author: nuno
author_rank: Frequent Contributor
timestamp: June 11, 2017, 01:47:22 am
content: The DMM wasn't mine... The owner was measuring mains voltage at a socket... but he had been measuring a current before... so you see.

author: brainwash
author_rank: Frequent Contributor
timestamp: June 11, 2017, 02:13:28 am
content: Yes, those multimeters have a 6th sense, they provide a tingling sensation when mains voltage is measured. However, with a CDI circuit, both you and the multimeter give out sparks. Not trying to bring down those cheap meters, they work GREAT (when probes are not oxidized and make contact), are precise (after calibration), safe (at low voltages) and repeatable (with a fully charged battery).I would just treat any of those meters as disposable, since they cost <20$, and count myself lucky if I'm not getting a shock. Any half-decent multimeter should survive 1500V. However I haven't seen anyone test them for 20kV. I don't think any professional puts 20kV on the probes, but beginners are likely to do that. So I would add that to the range of multimeter tests, in addition to 'ohms-range on mains voltage'.

author: Brumby
author_rank: Unknown
timestamp: June 11, 2017, 03:48:29 am
content: Quote from: nuno on June 11, 2017, 01:47:22 amI had a friend who was a guitarist. He had to have the best of things wherever possible, which included 3 guitars that even I could appreciate. I was asked to re-solder a pickup on one of them. This was a great honour (as anyone who has had dealings with a serious guitarist would understand) - and nerve-wracking as well.Well, he wanted to get a multimeter and asked me what was the best. I pointed him to Fluke - so he went out and spent some hundreds of dollars and came home with one. I forget which model it was, but I was green with envy - and thinking that this was too much meter for him. I was wrong about that - just as I was right about suggesting Fluke....One day he wanted to check the AC current at a power point... Yes, he did.All he did was end an HRC fuse - and wonder what he did wrong. I replaced the fuse and the meter was fine. I tried to explain what went wrong - and I believe I succeeded enough for him to stay safe. That was over 20 years ago - and he is still alive today.The Fluke was definitelynottoo much meter for him.

author: Electro Detective
author_rank: Super Contributor
timestamp: June 11, 2017, 05:59:56 am
content: some gaffa tape over the current inputs fixes up sunday hangover muso prodders real quick,and looks RNFR