Multimeter mistake: worried about outlet - Page 1
Forum section: electronics / beginners

author: greybond
author_rank: Newbie
timestamp: July 25, 2018, 10:54:59 pm
content: I made a mistake while attempting to use a multimeter to measure the voltage on a wall outlet that I was about to hook up an appliance to. I set the multimeter to ACV, but I put the probes into the mains. There was a spark, the wires to the multimeter blew, but the multimeter is fine and the outlet still works. I just want to make sure that there isn't anything else I should be worriesd about, except for the fact that I made a bad mistake with something I obviously shouldn't have been messing with.

author: Simon123
author_rank: Regular Contributor
timestamp: July 25, 2018, 11:22:02 pm
content: So you had the input leads connected to amps jack?

author: Muttley Snickers
author_rank: Unknown
timestamp: July 25, 2018, 11:30:22 pm
content: Welcome to the forum.From what you have described it sounds like you had the leads placed in the incorrect inputs on the meter, most likely the inputs intended for current measurement instead of those for voltage.Please provide the multimeter make, model and ideally a picture, this will save people guessing or making assumptions as to what occured and what you may now need to check in regards to the meters safe operation.

author: greybond
author_rank: Newbie
timestamp: July 26, 2018, 02:55:57 am
content: This is how I had the multimeter set up before I attempted to read the voltage.

author: james_s
author_rank: Super Contributor
timestamp: July 26, 2018, 04:15:01 am
content: That looks fine, are you sure you weren't imagining the spark?

author: SG-1
author_rank: Regular Contributor
timestamp: July 26, 2018, 04:24:23 am
content: Can you show us a picture of the blown leads ?There could be damage to the blades in the outlet.How did you test the outlet to see that it still works ?Trip a breaker ?

author: bitseeker
author_rank: Super Contributor
timestamp: July 26, 2018, 04:35:13 am
content: Quote from: greybond on July 26, 2018, 02:55:57 amThat setup looks fine and should not result in any sparks. I've measured much higher voltages in ACV and DCV modes with no such incident, although not with the same multimeter. If the meter was configured as pictured, it should've operated just fine unless there's a defect inside.Is it possible that the rotary switch was set one click to the right oninstead? That would be more in line with bad things happening.Could you have had the probes crossed such that the exposed metal sections came into contact with each other?Anything rattling around inside the meter?

author: mikerj
author_rank: Super Contributor
timestamp: July 26, 2018, 06:25:28 am
content: Hmm, the mA range uses the voltage input terminal, never a good sign. Could you maybe have accidentally selected AC mA rather than ACV?

author: alsetalokin4017
author_rank: Super Contributor
timestamp: July 26, 2018, 06:54:44 am
content: Time to open up the meter and give it a thorough internal examination.I wouldn't trust it to be safe, or accurate, until the reason for this event is found and corrected.

author: greybond
author_rank: Newbie
timestamp: July 27, 2018, 04:27:28 am
content: I threw away the leads, but they were blown out mostly by the probes and somewhat further along the cord. The outlet still works and the breaker didn't flip when it blew.

author: greybond
author_rank: Newbie
timestamp: July 27, 2018, 04:32:22 am
content: Also I definitely didn't imagine the sparks... my hands were burnt.(Sorry I'm doing a bad job of replying and quoting text... New here)I'm sure that is the way I had the multimeter set up when I tested it. I'll take a look at it tomorrow and see if there's anything rattling in it... Not planning on using it again any time soon until I figure out what happened.

author: TERRA Operative
author_rank: Super Contributor
timestamp: July 27, 2018, 05:00:45 am
content: Time to pull that sucker open and take some photos of the insides to see what went pop.If you are lucky it's just a fuse, if you weren't so lucky it'll mean some interesting photos.

author: SG-1
author_rank: Regular Contributor
timestamp: July 27, 2018, 12:45:55 pm
content: If the metal ends were damaged, then similar damage occurred inside the outlet.I always use a CAT IV instrument to probe my mains. If you are checking an outlet, the next thing you know, there you are inside the panel.