Multimeter + outlet = spark


I mistakenly left my digital multimeter on DC when i went to test a wall outlet, and it threw a spark and charred the tips of my multimeter. I had always been told it would not do such a thing, even on the wrong setting. However, I am now timid to recheck the outlet on the AC setting. So, I used a outlet plug light indicator and it said everything was kosher with the outlet. Can anyone tell me why the spark?
Tom
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response, but on DC setting one probe is for negative the other for positive (highly simplistic). Pull the positive terminal off a car battery and you'll see a spark too - basically the charge is jumping the gap until it becomes too large to generate a potential difference. In your multimeter when the AC switched from positive to negative the same thing probably happened.
Like I said pretty simplistic answer, but it sounds right to me.
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Well My cheap Micronta has 1000 VDC max on the inputs, 750VAC. If you're overvoltage on the range setting you'll just get a blinking display. Sure you weren't on the 10A unfused amps setting?
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Or in DCmA,or ACmA. If he had connected the 10A *unfused* range to 120VAC,it would have SHORTED the outlet and popped a breaker,and made a REALLY big spark,and a loud noise[KAPOW].It also would have melted the metal tip,perhaps also the probe wires.. The shunt for the 10A range is generally a heavy piece of solid wire with a tap for the output to the meter circuitry.
I believe you have to move the positive(red) lead to another jack to use the 10A range on most DMMs.Some DMMs play it safe and you have to move the red lead for ALL current ranges,for this reason.
You may want to check the internal mA fuse,it is probably open.
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On 23 Feb 2007 16:33:13 -0800, snipped-for-privacy@yahoo.com wrote:

Because the fail-safe device failed.

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On 23 Feb 2007 16:33:13 -0800, snipped-for-privacy@yahoo.com wrote:

It shouldn't spark at all. If the multimeter is of any decent design it should have a high ohm/volt rating and should not present a meaningful load to a circuit even on DC.
Did you rotate the switch while connected? Did you fumble one of the leads? Did you have it on current?
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On Feb 24, 6:52 am, snipped-for-privacy@mucks.net wrote:

I agree, in the DC mode, there shouldn't have been sparks. did the meter have autorange? If you are concerned that the meter is mdamaged and do not want a repeat spark event; try checking the meter against itself in the ohms setting, or measuring a 1.5 battery, or a low voltage AC source such as a no longer needed wall wart from an old cell phone. If the wall receptacle had a metal plate on it, you might have also accidentally shorted a lead against it. I suppose that if you do not use a meter on a regular basis, you would purchase the least expensive one you could find, and you consequently would also have minimal experience making measurements; if you use a meter on a regular basis, you know that having a good quality meter is imperative for safety and accuracy, and you also have expertise in taking measurements. If you cooked your meter, and did not stop your heart, then you paid a small price for a valuable lesson in taking measurments safely, and selecting higher quality when shopping for a new meter. hope this helps
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As others indicated, if you were on DC current, that is basically a short circuit. Most, if not all meters have a fuse inside to protect against just that type of thing. If the fuse is now open, the meter will still work on AC and DC volts, and ohms scales, just not on current settings. BTW, if you use a multimeter a lot, changing scales, etc., this is a pretty common thing to happen.
timO' wrote:

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wrote:

This is not so. If such a circuit was in place every time you'd measure DC you would have to have the polarity correct otherwise you would blow this fuse you are talking about.
Fuses exist in some multimeters but they are not in the DC voltage circuit. Instead a high impedance circuit is in place whether it is AC or DC, + to - , - to +.
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On Sun, 25 Feb 2007 13:28:20 -0500, snipped-for-privacy@mucks.net wrote:

I should read your post more carefully. I assumed you were referring to DC voltage, not current.
Ignore the above reply as it is referring to voltage.
Dc current circuits do, as you say create a short that will spark when used on voltage.
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/snip

Wouldn't that be a DC voltage coming out of the cell phone wall wart?

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Most I've seen are indeed DC, but I have seen a few AC ones for answering machines or computer modems.
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wrote:

I have seen a few AC wall warts, although most do seem to be DC.

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the person has to READ the side of the transformer/wall wart to determine if it is DC or AC.gee whiz.
the suggestion was intended to provide Sparky with a safe low voltage source to use to test the meter, that's all. Hey Sparky, are you still there?
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snipped-for-privacy@yahoo.com wrote:

My guess is your meter setting was wrong causing the meter act like direct short. In any event fuse must blow unless wrong fuse was in the meter.
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