Fried meter

C

Claude Hopper

Guest
I was using my little analog meter in dim light. I thought it was off so
set it to 250 volts and probed a 120v circuit. There was a flash and a
smell. Turns out I set it on 50ma DC instead of 250vac (opposite side of
switch). Well the voltage meter still works and the ohm meter still
works, I thought it blew a fuse but I guess that is just for ohms. So
what blew? Why no fuse? I can smell but can't see, must be on the back side.


--
Claude Hopper :)

? ? Ľ
 
Look for a very low ohm (~0.1 ohm) precision resistor that is used to
determine the current by measuring the voltage across it.

Bob

"Claude Hopper" <boobooililililil@roadrunner.com> wrote in message
news:5--dnQTGJpkmsbbUnZ2dnUVZ_o7inZ2d@giganews.com...
I was using my little analog meter in dim light. I thought it was off so
set it to 250 volts and probed a 120v circuit. There was a flash and a
smell. Turns out I set it on 50ma DC instead of 250vac (opposite side of
switch). Well the voltage meter still works and the ohm meter still
works, I thought it blew a fuse but I guess that is just for ohms. So
what blew? Why no fuse? I can smell but can't see, must be on the back
side.


--
Claude Hopper :)

? ? Ľ
Click to expand...
 
A few years ago a friend gave ma a meter that got 'blown up'. I think
someone tried to measure a 120Vac outlet with it set and connected in
"amps" mode. The tips of the probes were gone,and one was missing a big
piece out of the side.
I opened it up,and it had a hunk of heavy 'piano wire' looking
stuff(approx 12awg?,solid) used as the current shunt. There *was* a
little wire soldered about 1/4 way up the wire shunt,which had been
completely nuked. I soldered a new wire on the PCB,and soldered the
other end to the same place on the shunt where the old wire was. It
worked perfectly fine! I still have that old beast. :)

Bob Shuman wrote:
Look for a very low ohm (~0.1 ohm) precision resistor that is used to
determine the current by measuring the voltage across it.

Bob

"Claude Hopper" <boobooililililil@roadrunner.com> wrote in message
news:5--dnQTGJpkmsbbUnZ2dnUVZ_o7inZ2d@giganews.com...
I was using my little analog meter in dim light. I thought it was off so
set it to 250 volts and probed a 120v circuit. There was a flash and a
smell. Turns out I set it on 50ma DC instead of 250vac (opposite side of
switch). Well the voltage meter still works and the ohm meter still
works, I thought it blew a fuse but I guess that is just for ohms. So
what blew? Why no fuse? I can smell but can't see, must be on the back
side.


--
Claude Hopper :)

? ? Ľ
Click to expand...
 
"Claude Hopper" <boobooililililil@roadrunner.com> wrote in message
news:5--dnQTGJpkmsbbUnZ2dnUVZ_o7inZ2d@giganews.com...
I was using my little analog meter in dim light. I thought it was off so
set it to 250 volts and probed a 120v circuit. There was a flash and a
smell. Turns out I set it on 50ma DC instead of 250vac (opposite side of
switch). Well the voltage meter still works and the ohm meter still
works, I thought it blew a fuse but I guess that is just for ohms. So
what blew? Why no fuse? I can smell but can't see, must be on the back
side.


--
Claude Hopper :)

? ? Ľ
Click to expand...
Its a sign that you should get a cheap DMM.
 
ian field wrote:
"Claude Hopper" <boobooililililil@roadrunner.com> wrote in message
news:5--dnQTGJpkmsbbUnZ2dnUVZ_o7inZ2d@giganews.com...
I was using my little analog meter in dim light. I thought it was off so
set it to 250 volts and probed a 120v circuit. There was a flash and a
smell. Turns out I set it on 50ma DC instead of 250vac (opposite side of
switch). Well the voltage meter still works and the ohm meter still
works, I thought it blew a fuse but I guess that is just for ohms. So
what blew? Why no fuse? I can smell but can't see, must be on the back
side.


--
Claude Hopper :)

? ? Ľ

Its a sign that you should get a cheap DMM.
Click to expand...
I have a DMM but I like that little analog.


--
Claude Hopper :)

? ? Ľ
 
In article <07GWk.31774$MM5.16168@newsfe27.ams2>,
ian field <gangprobing.alien@ntlworld.com> wrote:
I was using my little analog meter in dim light. I thought it was off
so set it to 250 volts and probed a 120v circuit. There was a flash
and a smell. Turns out I set it on 50ma DC instead of 250vac (opposite
side of switch). Well the voltage meter still works and the ohm meter
still works, I thought it blew a fuse but I guess that is just for
ohms. So what blew? Why no fuse? I can smell but can't see, must be on
the back side.

Its a sign that you should get a cheap DMM.
Click to expand...
They blow up equally as well when used like this. ;-)

Better designs use a separate terminal for current measurement to help
prevent such mistakes.

On something like a Fluke the protection fuse can cost more to replace
than a cheap DVM.

--
*They call it PMS because Mad Cow Disease was already taken.

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.
 
Better designs use a separate terminal for current measurement
to help prevent such mistakes.
Click to expand...
On a Fluke -- and likely other products -- plugging the test cable into the
current jack when the switch is set for volts produces a warning beep. (The
opposite doesn't occur because there's no need for it.)


On something like a Fluke the protection fuse can cost more
to replace than a cheap DVM.
Click to expand...
Perhaps, but would you rather have the good Wilkens coffee, or some of the
cheap stuff?

I once asked a Fluke engineer why their DVMs were so expensive. He said that
the protection circuitry cost more than the measurement circuitry!

Old timers will remember an Electronics World series, "Mac's Electronics
Service", written by John T. Frye. In one episode an obnoxious salesman
comes in to demonstrate a revolutionary Triplett * meter (I've often
wondered how much they paid Triplett for this article) which was essentially
burn-out proof. He sets it to the most-sensitive current range, then shoves
the probes into a wall outlet. An internal relay disconnects the inputs
before any damage occurs. (Well, that was the claim.)

* I think. I'm pretty sure it wasn't Weston.
 
In article <gggrlg$et1$1@news.motzarella.org>,
William Sommerwerck <grizzledgeezer@comcast.net> wrote:
Better designs use a separate terminal for current measurement
to help prevent such mistakes.

On a Fluke -- and likely other products -- plugging the test cable into
the current jack when the switch is set for volts produces a warning
beep. (The opposite doesn't occur because there's no need for it.)
Click to expand...

On something like a Fluke the protection fuse can cost more to replace
than a cheap DVM.

Perhaps, but would you rather have the good Wilkens coffee, or some of
the cheap stuff?
Click to expand...
I'm not the one to ask because I'm addicted to instant coffee. ;-)

But I do own a Fluke - but wouldn't use it for what the OP was doing. I
prefer a pukka one designed for electricians - this sort of thing:-

http://www.tlc-direct.co.uk/Main_Index/Test_Meters_Index/Dilog_TM6741/index.html

Which is easier to use on mains. The Fluke tends to stay put in the
workshop.

I once asked a Fluke engineer why their DVMs were so expensive. He said
that the protection circuitry cost more than the measurement circuitry!
Click to expand...
I can believe it - but like all good tools is worth the cost.

--
*Rehab is for quitters.

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.
 
"Dave Plowman (News)" <dave@davenoise.co.uk> wrote in message
news:5003d9296fdave@davenoise.co.uk...
In article <gggrlg$et1$1@news.motzarella.org>,
William Sommerwerck <grizzledgeezer@comcast.net> wrote:
Better designs use a separate terminal for current measurement
to help prevent such mistakes.

On a Fluke -- and likely other products -- plugging the test cable into
the current jack when the switch is set for volts produces a warning
beep. (The opposite doesn't occur because there's no need for it.)


On something like a Fluke the protection fuse can cost more to replace
than a cheap DVM.

Perhaps, but would you rather have the good Wilkens coffee, or some of
the cheap stuff?

I'm not the one to ask because I'm addicted to instant coffee. ;-)

But I do own a Fluke - but wouldn't use it for what the OP was doing.
Click to expand...
I have a variety of go/no-go mains checkers so none of my meters would ever
be in contact with the mains unless I specifically wanted to check the mains
voltage was within spec.

What I think is the real lesson for the OP to learn is: Never mess with a
mains outlet in inadequate light conditions..
 
On Mon, 24 Nov 2008 16:38:34 -0500, Claude Hopper
<boobooililililil@roadrunner.com> wrote:

There was a flash and a smell.
Click to expand...
Bright green flash = fused copper trace
Bright white flash = vaporized steel trace (wire wound resistor)
Black smoke = burned carbon comp resistor
Black smoke and foul smell = burned rubber
Grey smoke = burned clay coated film resistor
White smoke = burned paper label, phenolic, or cardboard insulator
White smoke and fould smell = burned plastic
Brown smoke = burned PCB

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
 
"Jeff Liebermann" <jeffl@cruzio.com> wrote in message
news:qrnoi4tn48385jk0iie4jd1tcrsd9ssq3b@4ax.com...
On Mon, 24 Nov 2008 16:38:34 -0500, Claude Hopper
boobooililililil@roadrunner.com> wrote:

There was a flash and a smell.

Bright green flash = fused copper trace
Bright white flash = vaporized steel trace (wire wound resistor)
Black smoke = burned carbon comp resistor
Black smoke and foul smell = burned rubber
Grey smoke = burned clay coated film resistor
White smoke = burned paper label, phenolic, or cardboard insulator
White smoke and fould smell = burned plastic
Brown smoke = burned PCB
Click to expand...
Do you have a colour chart for various combinations of the above?
 
In article <gggrlg$et1$1@news.motzarella.org>,
William Sommerwerck <grizzledgeezer@comcast.net> wrote:
I once asked a Fluke engineer why their DVMs were so expensive. He said
that the protection circuitry cost more than the measurement circuitry!
Click to expand...
Got an email flyer from one of my suppliers pushing Fluke meters. Idly
glanced at the spec of one to notice it was made in China. Is nothing
sacred?

--
*If a mute swears, does his mother wash his hands with soap?

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.
 
On Tue, 25 Nov 2008 10:31:47 -0000, Dave Plowman (News) <dave@davenoise.co.uk> wrote:

In article <07GWk.31774$MM5.16168@newsfe27.ams2>,
ian field <gangprobing.alien@ntlworld.com> wrote:
I was using my little analog meter in dim light. I thought it was off
so set it to 250 volts and probed a 120v circuit. There was a flash
and a smell. Turns out I set it on 50ma DC instead of 250vac (opposite
side of switch). Well the voltage meter still works and the ohm meter
still works, I thought it blew a fuse but I guess that is just for
ohms. So what blew? Why no fuse? I can smell but can't see, must be on
the back side.

Its a sign that you should get a cheap DMM.

They blow up equally as well when used like this. ;-)

Better designs use a separate terminal for current measurement to help
prevent such mistakes.
Click to expand...
Bad idea. Then you forget to move it from current to voltage plug, and just turn the dial to volts. BANG!

On something like a Fluke the protection fuse can cost more to replace
than a cheap DVM.
Click to expand...
--
http://www.petersparrots.com http://www.insanevideoclips.com http://www.petersphotos.com

Why does sour cream have an expiration date?
 
On Tue, 25 Nov 2008 20:31:26 -0000, Jeff Liebermann <jeffl@cruzio.com> wrote:

On Mon, 24 Nov 2008 16:38:34 -0500, Claude Hopper
boobooililililil@roadrunner.com> wrote:

There was a flash and a smell.

Bright green flash = fused copper trace
Bright white flash = vaporized steel trace (wire wound resistor)
Black smoke = burned carbon comp resistor
Black smoke and foul smell = burned rubber
Grey smoke = burned clay coated film resistor
White smoke = burned paper label, phenolic, or cardboard insulator
White smoke and fould smell = burned plastic
Brown smoke = burned PCB
Click to expand...
Brilliant!


--
http://www.petersparrots.com http://www.insanevideoclips.com http://www.petersphotos.com

A patient complained to his doctor, "I've been to three other doctors and none of them agreed with your diagnosis."
The doctor calmly replied, "Just wait until the autopsy, then they'll see that I was right."
 
"Peter Hucker" <none@spam.com> writes:

On Tue, 25 Nov 2008 20:31:26 -0000, Jeff Liebermann <jeffl@cruzio.com> wrote:

On Mon, 24 Nov 2008 16:38:34 -0500, Claude Hopper
boobooililililil@roadrunner.com> wrote:

There was a flash and a smell.

Bright green flash = fused copper trace
Bright white flash = vaporized steel trace (wire wound resistor)
Black smoke = burned carbon comp resistor
Black smoke and foul smell = burned rubber
Grey smoke = burned clay coated film resistor
White smoke = burned paper label, phenolic, or cardboard insulator
White smoke and fould smell = burned plastic
Brown smoke = burned PCB

Brilliant!
Click to expand...
Should add in electrolytics. :)

--
sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
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Important: Anything sent to the email address in the message header above is
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"Samuel M. Goldwasser" <sam@seas.upenn.edu> wrote in message
news:k5a7u7m1.fsf@seas.upenn.edu...
"Peter Hucker" <none@spam.com> writes:

On Tue, 25 Nov 2008 20:31:26 -0000, Jeff Liebermann <jeffl@cruzio.com
wrote:

On Mon, 24 Nov 2008 16:38:34 -0500, Claude Hopper
boobooililililil@roadrunner.com> wrote:

There was a flash and a smell.

Bright green flash = fused copper trace
Bright white flash = vaporized steel trace (wire wound resistor)
Black smoke = burned carbon comp resistor
Black smoke and foul smell = burned rubber
Grey smoke = burned clay coated film resistor
White smoke = burned paper label, phenolic, or cardboard insulator
White smoke and fould smell = burned plastic
Brown smoke = burned PCB

Brilliant!

Should add in electrolytics. :)
Click to expand...
Technically, its not smoke when an electrolytic vents.
 
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