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

wrote in message
oups.com...
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

Probably not the best answer, someone else can chime in to clear up my
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.

On Feb 23, 10:09 pm, "Eigenvector" wrote:
wrote in message

oups.com...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

Probably not the best answer, someone else can chime in to clear up my
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.

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?

"spudnuty" wrote in
ups.com:

On Feb 23, 10:09 pm, "Eigenvector" wrote:
wrote in message

oups.com...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

Probably not the best answer, someone else can chime in to clear up
my 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.

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?


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.

--
Jim Yanik
jyanik
at
kua.net

On 23 Feb 2007 16:33:13 -0800, wrote:

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?

Because the fail-safe device failed.




Tom

On 23 Feb 2007 16:33:13 -0800, wrote:

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

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?

On Feb 24, 6:52 am, wrote:
On 23 Feb 2007 16:33:13 -0800, wrote:

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

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?

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

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:
On Feb 24, 6:52 am, wrote:
On 23 Feb 2007 16:33:13 -0800, wrote:

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
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?

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

/snip


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.

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


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

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

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

On Sat, 24 Feb 2007 13:18:08 -0500, "jackson"
wrote:

/snip


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.

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


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


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


--
Mark Lloyd
http://notstupid.laughingsquid.com

"Unlike biological evolution. 'intelligent design' is
not a genuine scientific theory and, therefore, has
no place in the curriculum of our nation's public
school classes." -- Ted Kennedy

On Feb 24, 2:23 pm, Mark Lloyd wrote:
On Sat, 24 Feb 2007 13:18:08 -0500, "jackson"
wrote:

/snip

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.

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

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



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

--
Mark Lloydhttp://notstupid.laughingsquid.com

"Unlike biological evolution. 'intelligent design' is
not a genuine scientific theory and, therefore, has
no place in the curriculum of our nation's public
school classes." -- Ted Kennedy

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?

wrote:
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

Hi,
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.

On Sat, 24 Feb 2007 14:48:20 GMT, Art Todesco
wrote:

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.

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 +.

On Sun, 25 Feb 2007 13:28:20 -0500, wrote:

On Sat, 24 Feb 2007 14:48:20 GMT, Art Todesco
wrote:

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.

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 +.

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.