On page 325 of this book, specific steps are given on how to check an
AC outlet with a multimeter.... I would just use a circuit tester
myself, but I'm wondering how is it safe to put leads in an outlet
looking for 120 volts when doing the same (albeit stupid) thing with
another object (such as a screwdriver) will give you a POP you won't
soon forget. I guess I'm thinking about the times when all of us were
very young and we were always warned never to stick anything in an
outlet ather than a plug. Why don't you get zapped using the
multimeter?

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"Lindsey Matthews" <sparenowon@crucible.com> wrote in message
news:cjeu2vg2mvm5vo15s74pjlpsq
89ia12mrs@4ax.com...
> On page 325 of this book, specific steps are given on how to check an
> AC outlet with a multimeter.... I would just use a circuit tester
> myself, but I'm wondering how is it safe to put leads in an outlet
> looking for 120 volts when doing the same (albeit stupid) thing with
> another object (such as a screwdriver) will give you a POP you won't
> soon forget. I guess I'm thinking about the times when all of us were
> very young and we were always warned never to stick anything in an
> outlet ather than a plug. Why don't you get zapped using the
> multimeter?

You dont get zapped because thats what they are designed to do ie test
voltage (among other things) it just acts like a ordinary appliance and acts
as a load to the supply..apart from the fact that its the current that kills
you not the voltage, the main thing you have to be aware of is what you have
got the MM set on, if you try and measure current while having it set on
voltage, you will get the POP...when testing the voltage you might not wanna
hang on to the metal parts of the probes, also always start at the highest
measurement range and work down through the scale.

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On Thu, 23 Jan 2003 00:56:34 GMT, Lindsey Matthews
<sparenowon@crucible.com> wrote:

>On page 325 of this book, specific steps are given on how to check an
>AC outlet with a multimeter.... I would just use a circuit tester
>myself, but I'm wondering how is it safe to put leads in an outlet
>looking for 120 volts when doing the same (albeit stupid) thing with
>another object (such as a screwdriver) will give you a POP you won't
>soon forget. I guess I'm thinking about the times when all of us were
>very young and we were always warned never to stick anything in an
>outlet ather than a plug. Why don't you get zapped using the
>multimeter?

You won't get zapped using a screwdriver either, unless you touch the
netal and are grounded. The screwdriver has no purpose in the AC
receptacle, while the meter leads do...they are properly insulated for
that purpose, and, unless you find a way to touch the metal parts
together (a nice way to make an arc welder), or touch them, or shove
them in too far, nothing much should go wrong.

Having been in the electronics repair business for a number of years,
I have seen a few things. I have heard it recommended that any
measurement should have the power removed first, then the leads
connected, then the power applied. That is indeed the safest approach,
but it eats too much time, and time is always money. I have also seen
people who put an electrical plug on both ends of an AC cord, instead
of plug-socket...not a good plan. I have seen 3-phase 208 VAC wired to
a regular 120 VAC receptacle on a light pole in a public park area,
which would turn an 11 watt curling iron into a 40 watt soldering
iron, and a hotplate or toaster into ???

Electricity shouldn't be feared, but it MUST be respected, and that
means knowing how it does what it does before trying too many things
with it.

Tom

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On Thu, 23 Jan 2003 12:33:18 +1100, "Cackling Pipes"
<NOSPAMnytro308@hotmail.com> wrote:

>
>"Lindsey Matthews" <sparenowon@crucible.com> wrote in message
> news:cjeu2vg2mvm5vo15s74pjlpsq
89ia12mrs@4ax.com...
>> On page 325 of this book, specific steps are given on how to check an
>> AC outlet with a multimeter.... I would just use a circuit tester
>> myself, but I'm wondering how is it safe to put leads in an outlet
>> looking for 120 volts when doing the same (albeit stupid) thing with
>> another object (such as a screwdriver) will give you a POP you won't
>> soon forget. I guess I'm thinking about the times when all of us were
>> very young and we were always warned never to stick anything in an
>> outlet ather than a plug. Why don't you get zapped using the
>> multimeter?
>
>You dont get zapped because thats what they are designed to do ie test
>voltage (among other things) it just acts like a ordinary appliance and acts
>as a load to the supply..apart from the fact that its the current that kills
>you not the voltage,

The voltage pushes the current, and the current on an AC receptacle is
at least 15 amps, more than enough to kill. A human body wouldn't draw
that much, at least not at first.

the main thing you have to be aware of is what you have
>got the MM set on, if you try and measure current while having it set on
>voltage, you will get the POP

No...if you try to measure current while testing a voltage source, you
get the pop.

Tom
....when testing the voltage you might not wanna
>hang on to the metal parts of the probes, also always start at the highest
>measurement range and work down through the scale.
>

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I work with voltages of 24VDC up to 2300VAC every day. The only time you'll
"get a pop" is if your meter is under sized and your up in the 1000V+ range.
You'll blow the internal fuse on the meter if the current range is set too
low but that's really all the fireworks you're gonna see.
It's actually required by some companies to do a three point test on all
measurements. First measure a known source, usually an outlet, second take
your measurement and finally confirm that your meter is still valid by
measuring the known source again. Sound like a lot of work but its better
than getting poked because of a faulty meter. (Fluke had a recent recall on
some of their meters)

A good meter has extremely high resistance when measuring EMF so the current
you draw is very low and reasonably safe.

I'm a little confused as to how you could wire 3 phase into a single phase
outlet and get the results Tom described???


"Tom MacIntyre" <tom__macintyre@hotmail.com> wrote in message
news:anhu2v4d5gdb2do36otqesla0
i01tfbr7i@4ax.com...
> On Thu, 23 Jan 2003 00:56:34 GMT, Lindsey Matthews
> <sparenowon@crucible.com> wrote:
>
> >On page 325 of this book, specific steps are given on how to check an
> >AC outlet with a multimeter.... I would just use a circuit tester
> >myself, but I'm wondering how is it safe to put leads in an outlet
> >looking for 120 volts when doing the same (albeit stupid) thing with
> >another object (such as a screwdriver) will give you a POP you won't
> >soon forget. I guess I'm thinking about the times when all of us were
> >very young and we were always warned never to stick anything in an
> >outlet ather than a plug. Why don't you get zapped using the
> >multimeter?
>
> of plug-socket...not a good plan. I have seen 3-phase 208 VAC wired to
> a regular 120 VAC receptacle on a light pole in a public park area,
> which would turn an 11 watt curling iron into a 40 watt soldering
> iron, and a hotplate or toaster into ???
>

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On Sat, 25 Jan 2003 02:21:04 GMT, "klassick" <alluvitt@attbi.com>
wrote:

>I work with voltages of 24VDC up to 2300VAC every day. The only time you'll
>"get a pop" is if your meter is under sized and your up in the 1000V+ range.
>You'll blow the internal fuse on the meter if the current range is set too
>low but that's really all the fireworks you're gonna see.
>It's actually required by some companies to do a three point test on all
>measurements. First measure a known source, usually an outlet, second take
>your measurement and finally confirm that your meter is still valid by
>measuring the known source again. Sound like a lot of work but its better
>than getting poked because of a faulty meter. (Fluke had a recent recall on
>some of their meters)
>
>A good meter has extremely high resistance when measuring EMF so the current
>you draw is very low and reasonably safe.
>
>I'm a little confused as to how you could wire 3 phase into a single phase
>outlet and get the results Tom described???

It was 1 phase of a 3-phase system. I was performing in an outdoor
concert there, and I turned my (tube) guitar amplifier on first,
before anyone else, to warm it up. Good thing...the standby switch was
set so only the filaments were powered (no plate voltage), the tubes
glowed like the sun (lucky I didn't lose one or more) and the power
transformer groaned. I shut it off very quickly, told the boys to not
turn on their (all solid state, all gear would have died horrible and
likely complete deaths) equipment, and removed the power.

If you do the math, 11 watts from 110 volts means the curling iron's
resistance is 110^2*11, or about 1100 ohms. For 208 VAC, it's
208^2/1100, or 39.3 watts, close to my 40W guesstimate.

Tom

>
>
>"Tom MacIntyre" <tom__macintyre@hotmail.com> wrote in message
> news:anhu2v4d5gdb2do36otqesla0
i01tfbr7i@4ax.com...
>> On Thu, 23 Jan 2003 00:56:34 GMT, Lindsey Matthews
>> <sparenowon@crucible.com> wrote:
>>
>> >On page 325 of this book, specific steps are given on how to check an
>> >AC outlet with a multimeter.... I would just use a circuit tester
>> >myself, but I'm wondering how is it safe to put leads in an outlet
>> >looking for 120 volts when doing the same (albeit stupid) thing with
>> >another object (such as a screwdriver) will give you a POP you won't
>> >soon forget. I guess I'm thinking about the times when all of us were
>> >very young and we were always warned never to stick anything in an
>> >outlet ather than a plug. Why don't you get zapped using the
>> >multimeter?
>>
>> of plug-socket...not a good plan. I have seen 3-phase 208 VAC wired to
>> a regular 120 VAC receptacle on a light pole in a public park area,
>> which would turn an 11 watt curling iron into a 40 watt soldering
>> iron, and a hotplate or toaster into ???
>>
>

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"Tom MacIntyre" <tom__macintyre@hotmail.com> wrote in message
news:fu053vo34tat1shd19m2mejv7
feku1lsd0@4ax.com...
> On Sat, 25 Jan 2003 02:21:04 GMT, "klassick" <alluvitt@attbi.com>
> wrote:
> snip
>> >I'm a little confused as to how you could wire 3 phase into a single
phase

> >outlet and get the results Tom described???
>
> It was 1 phase of a 3-phase system. I was performing in an outdoor
> concert there, and I turned my (tube) guitar amplifier on first,
> before anyone else, to warm it up. Good thing...the standby switch was
> set so only the filaments were powered (no plate voltage), the tubes
> glowed like the sun (lucky I didn't lose one or more) and the power
> transformer groaned. I shut it off very quickly, told the boys to not
> turn on their (all solid state, all gear would have died horrible and
> likely complete deaths) equipment, and removed the power.
>
> If you do the math, 11 watts from 110 volts means the curling iron's
> resistance is 110^2*11, or about 1100 ohms. For 208 VAC, it's
> 208^2/1100, or 39.3 watts, close to my 40W guesstimate.
>
> Tom

Well putting aside true power and looking at apparent power without taking
into consideration inductive impedence Ohm's Law states E=I*R & P=I*E
11 = I * 120 so I = .092 and R = 1304
then 208 = 1304 * I and I = .16 then 208*.16 = 33.17 W (but the
true power would be less until the curling iron coils melted) But I see your
point. What I missed was that you were outside. The transformer was wired in
Delta. The outlet was wired wrong. A 250V rated receptacle can look very
similar to a 125V. The difference is the blade configuration. I hope you
contacted the municipality about the error.

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On Sat, 25 Jan 2003 14:45:11 GMT, "klassick" <alluvitt@attbi.com>
wrote:

>
>"Tom MacIntyre" <tom__macintyre@hotmail.com> wrote in message
> news:fu053vo34tat1shd19m2mejv7
feku1lsd0@4ax.com...
>> On Sat, 25 Jan 2003 02:21:04 GMT, "klassick" <alluvitt@attbi.com>
>> wrote:
>> snip
>>> >I'm a little confused as to how you could wire 3 phase into a single
> phase
>> >outlet and get the results Tom described???
>>
>> It was 1 phase of a 3-phase system. I was performing in an outdoor
>> concert there, and I turned my (tube) guitar amplifier on first,
>> before anyone else, to warm it up. Good thing...the standby switch was
>> set so only the filaments were powered (no plate voltage), the tubes
>> glowed like the sun (lucky I didn't lose one or more) and the power
>> transformer groaned. I shut it off very quickly, told the boys to not
>> turn on their (all solid state, all gear would have died horrible and
>> likely complete deaths) equipment, and removed the power.
>>
>> If you do the math, 11 watts from 110 volts means the curling iron's
>> resistance is 110^2*11, or about 1100 ohms. For 208 VAC, it's
>> 208^2/1100, or 39.3 watts, close to my 40W guesstimate.
>>
>> Tom
>
>Well putting aside true power and looking at apparent power without taking
>into consideration inductive impedence Ohm's Law states E=I*R & P=I*E
>11 = I * 120 so I = .092 and R = 1304
>then 208 = 1304 * I and I = .16 then 208*.16 = 33.17 W (but the
>true power would be less until the curling iron coils melted) But I see your
>point.

Well, you used 120 VAC and I used 110 also (around here it's actually
usually 115-117). If the iron's rated wattage happened at 110, that
would be worst case, because it means lower resistance. I don't know
what the typical reactive versus resistive components are for one
either, of course. :-)

>What I missed was that you were outside. The transformer was wired in
>Delta. The outlet was wired wrong. A 250V rated receptacle can look very
>similar to a 125V. The difference is the blade configuration. I hope you
>contacted the municipality about the error.
>

It was definitely a 110-120 VAC receptacle. I am not an electrician,
and don't know anything about the practical application, but I
understand the basics of Delta and Wye configurations because I was
taught that stuff 20+ years ago in an electronics engineering
technology course. I notified the park attendant of course.

It's scary, but I once was told by a licensed electrician that the hot
and neutral wires stayed on the same side of the ground pin, whether
the ground was above or below the neutral and hot. I wonder where he
lost in the translation what most Joe Fix-it's know from the colour of
the connections inside. :-(

Tom

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