Can anyone tell me why I would get a 27 volt reading on a 120v circuit.
I have a old home but some of the home has been re-wired. I am
remodeling my bath room and removed old florescent lights. I tested
the power at the connections and got a reading of 27v. I climbed in
the attic and it looks like the wire is coming from a junction box with
several other wires. It looks like the work was done by a pro. The
upstairs has 2-20amp (connected together) circuits.

In article .com, wrote:
Can anyone tell me why I would get a 27 volt reading on a 120v circuit.

Probably because you're using a digital voltmeter, which is reading a very
very low amperage induced current in the conductor you're testing. Try using
an analog meter instead, and you'll probably see -zero- volts.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

wrote in news:1161608374.490859.297690
@h48g2000cwc.googlegroups.com:

Can anyone tell me why I would get a 27 volt reading on a 120v circuit.
I have a old home but some of the home has been re-wired. I am
remodeling my bath room and removed old florescent lights. I tested
the power at the connections and got a reading of 27v. I climbed in
the attic and it looks like the wire is coming from a junction box with
several other wires. It looks like the work was done by a pro. The
upstairs has 2-20amp (connected together) circuits.




You are using a low impedance (resistance) meter (cheapo). It is not
invisible to the circuit when you connect it. All meters have an internal
resistance.

The lower the resistance of anything, the more current (amps) will flow
through it. The more current that flows through it the higher the voltage
drop across it.

The sum of the voltages in a loop with 120v source will be 120. How the
120 is divided among the components in the loop depends on the resistance
of each device but it will always add up to 120.

I have a cheapo digital and an old high impediance analog meter. When I
get a reading such as you did, I get out the analog. It always proves the
cheapo wrong.

You have a few choices he

a) Trust me (ill advised according to many).
b) Get a high impedance digital or analog (needle type) meter.
c) Get a cheap test lamp for 120. Compare brightness of lamp to an outlet
working normally.
d) Grab the alleged 27v wires. Do you get a tingle or jolt? (ill advised
according to many)

Option d has the advantage of a free ekg if you survive. If you don't
survive, as the Monty Python "Bring out your dead" skit went:
---------------------

[clang] Bring out your dead!

Customer
Here's one.

Cart Master
Ninepence.

Dead Person
I'm not dead!

Cart Master
What?

Customer
Nothing. Here's your ninepence.

Dead Person
I'm not dead!

Cart Master
'Ere. He says he's not dead!

Customer
Yes, he is.

Dead Person
I'm not!

Cart Master
He isn't?

Customer
Well, he will be soon. He's very ill.
---------------------


The upstairs has 2-20amp (connected together) circuits.

I'm no electrician but this sounds fishy.

Al Bundy wrote:
wrote in news:1161608374.490859.297690
@h48g2000cwc.googlegroups.com:

Can anyone tell me why I would get a 27 volt reading on a 120v circuit.
I have a old home but some of the home has been re-wired. I am
remodeling my bath room and removed old florescent lights. I tested
the power at the connections and got a reading of 27v. I climbed in
the attic and it looks like the wire is coming from a junction box with
several other wires. It looks like the work was done by a pro. The
upstairs has 2-20amp (connected together) circuits.




You are using a low impedance (resistance) meter ...

Precisely backwards...a _high_ impedance meter can load a circuit and
read "phantom" voltages. For such tests of household wiring circuits
an inexpensive analog meter is probably more reliable than the digital.

To OP, need more. Were the lights functioning before and where/what
are you measuring?
Breaker on/off, at the switch or the feed.

What you're seeing at the upstairs junction box is probably simply a
feed junction. Two circuits connected together is one circuit.

If you're actually measuring something that should be a true voltage,
it implies a loose neutral or hot. If you're simply measuring the
leads from the switch you just disconnected w/ the switch off, it is
almost certain your _HIGH_ (not low) impedance digital meter is loading
the circuit. Put a light bulb across the wires and measure again and
it will undoubtedly be zero.

dpb spake thus:

Al Bundy wrote:

wrote in news:1161608374.490859.297690
:

Can anyone tell me why I would get a 27 volt reading on a 120v circuit.
I have a old home but some of the home has been re-wired. I am
remodeling my bath room and removed old florescent lights. I tested
the power at the connections and got a reading of 27v. I climbed in
the attic and it looks like the wire is coming from a junction box with
several other wires. It looks like the work was done by a pro. The
upstairs has 2-20amp (connected together) circuits.

You are using a low impedance (resistance) meter ...

Precisely backwards...a _high_ impedance meter can load a circuit and
read "phantom" voltages. For such tests of household wiring circuits
an inexpensive analog meter is probably more reliable than the digital.

Nope, *you've* got it backwards: high impedance = high sensitivity. For
a meter with an impedance in the megohm range, it's very easy to pick up
stray, "phantom" voltage readings.


--
Just as McDonald's is where you go when you're hungry but don't really
care about the quality of your food, Wikipedia is where you go when
you're curious but don't really care about the quality of your knowledge.

- Matthew White's WikiWatch (http://users.erols.com/mwhite28/wikiwoo.htm)

wrote:
Can anyone tell me why I would get a 27 volt reading on a 120v circuit.
I have a old home but some of the home has been re-wired. I am
remodeling my bath room and removed old florescent lights. I tested
the power at the connections and got a reading of 27v. I climbed in
the attic and it looks like the wire is coming from a junction box with
several other wires. It looks like the work was done by a pro. The
upstairs has 2-20amp (connected together) circuits.
..
Some replies are making this too complicated. Forget the volts and amps
and impedance stuff.

Your question has been asked frequently here; it's sensible one but
usually asked by someone without much electrical experience and
training and almost always involves voltage read with one of those
digital display meters.

Non technical reply:

Digital meters are so sensitive (even the cheapest ones) that they can
pick up voltages induced into even dead/disconnected wires from
adjacent working/activated wires.

In some circumstances they can pick up the faint voltages of the
multitude of radio and wireless-device waves that surround us these
days! Even if a wire is grounded at the far end it can still act as an
antenna at many frequencies and thus pick up enough electrical energy
to read 'something' on a meter. Depends on the location, radio field
strengths the meter etc.

Heck; I have one meter sensitive enough that, if I touch the leads with
my fingers it will pick up enough energy for a reading even if I'm
standing in my basement. Hook it up to a spare coil of wire hung up and
not connected to anything and one gets a higher reading again.

For house AC work a spare bulb screwed in a lamp socket with a couple
of leads is often the best way to test whether a wire is permanently
'live' from the AC breaker/fuse panel, is (switch on/off) switched
live, a neutral or a ground.

The mention of two 20 amp circuits 'connected together' is confusing.
It also might be confusing/unsafe for anyone working on that/those
circuits; my understanding is that once the breaker/fuse for a circuit
is off/removed there should be no other power (from another connection
circuit etc.) to anything on that circuit or in the same AC boxes.
That's a little worrying and possibly not up to code? Possibly an
insurance concern?

Maybe you mean two 'separate' 20 amp circuits; or is the breaker a
'double 20 amp' with the handles connected together so that both
breakers will trip at same time?????????

In article m, David Nebenzahl wrote:
dpb spake thus:

Al Bundy wrote:

wrote in news:1161608374.490859.297690
:

Can anyone tell me why I would get a 27 volt reading on a 120v circuit.
I have a old home but some of the home has been re-wired. I am
remodeling my bath room and removed old florescent lights. I tested
the power at the connections and got a reading of 27v. I climbed in
the attic and it looks like the wire is coming from a junction box with
several other wires. It looks like the work was done by a pro. The
upstairs has 2-20amp (connected together) circuits.

You are using a low impedance (resistance) meter ...

Precisely backwards...a _high_ impedance meter can load a circuit and
read "phantom" voltages. For such tests of household wiring circuits
an inexpensive analog meter is probably more reliable than the digital.

Nope, *you've* got it backwards: high impedance = high sensitivity. For
a meter with an impedance in the megohm range, it's very easy to pick up
stray, "phantom" voltage readings.

Ummmm.... that's exactly what he said. What's "backwards"?

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

terry wrote:
wrote:
Can anyone tell me why I would get a 27 volt reading on a 120v circuit.
I have a old home but some of the home has been re-wired. I am
remodeling my bath room and removed old florescent lights. I tested
the power at the connections and got a reading of 27v. I climbed in
the attic and it looks like the wire is coming from a junction box with
several other wires. It looks like the work was done by a pro. The
upstairs has 2-20amp (connected together) circuits.
.
Some replies are making this too complicated. Forget the volts and amps
and impedance stuff.

Your question has been asked frequently here; it's sensible one but
usually asked by someone without much electrical experience and
training and almost always involves voltage read with one of those
digital display meters.

Non technical reply:

Digital meters are so sensitive (even the cheapest ones) that they can
pick up voltages induced into even dead/disconnected wires from
adjacent working/activated wires.

In some circumstances they can pick up the faint voltages of the
multitude of radio and wireless-device waves that surround us these
days! Even if a wire is grounded at the far end it can still act as an
antenna at many frequencies and thus pick up enough electrical energy
to read 'something' on a meter. Depends on the location, radio field
strengths the meter etc.

Heck; I have one meter sensitive enough that, if I touch the leads with
my fingers it will pick up enough energy for a reading even if I'm
standing in my basement. Hook it up to a spare coil of wire hung up and
not connected to anything and one gets a higher reading again.

For house AC work a spare bulb screwed in a lamp socket with a couple
of leads is often the best way to test whether a wire is permanently
'live' from the AC breaker/fuse panel, is (switch on/off) switched
live, a neutral or a ground.

The mention of two 20 amp circuits 'connected together' is confusing.
It also might be confusing/unsafe for anyone working on that/those
circuits; my understanding is that once the breaker/fuse for a circuit
is off/removed there should be no other power (from another connection
circuit etc.) to anything on that circuit or in the same AC boxes.
That's a little worrying and possibly not up to code? Possibly an
insurance concern?

Maybe you mean two 'separate' 20 amp circuits; or is the breaker a
'double 20 amp' with the handles connected together so that both
breakers will trip at same time?????????

Thanks to all who replied. I will check the wire using a light because
I did use a digital multimeter. I may very well be explaining the two
20amp circuits wong. I do think both breakers will trip at the same
time. The handles are connected together.

terry wrote:
wrote:
Can anyone tell me why I would get a 27 volt reading on a 120v circuit.
I have a old home but some of the home has been re-wired. I am
remodeling my bath room and removed old florescent lights. I tested
the power at the connections and got a reading of 27v. I climbed in
the attic and it looks like the wire is coming from a junction box with
several other wires. It looks like the work was done by a pro. The
upstairs has 2-20amp (connected together) circuits.
.
Some replies are making this too complicated. Forget the volts and amps
and impedance stuff.

Your question has been asked frequently here; it's sensible one but
usually asked by someone without much electrical experience and
training and almost always involves voltage read with one of those
digital display meters.

Non technical reply:

Digital meters are so sensitive (even the cheapest ones) that they can
pick up voltages induced into even dead/disconnected wires from
adjacent working/activated wires.

In some circumstances they can pick up the faint voltages of the
multitude of radio and wireless-device waves that surround us these
days! Even if a wire is grounded at the far end it can still act as an
antenna at many frequencies and thus pick up enough electrical energy
to read 'something' on a meter. Depends on the location, radio field
strengths the meter etc.

Heck; I have one meter sensitive enough that, if I touch the leads with
my fingers it will pick up enough energy for a reading even if I'm
standing in my basement. Hook it up to a spare coil of wire hung up and
not connected to anything and one gets a higher reading again.

For house AC work a spare bulb screwed in a lamp socket with a couple
of leads is often the best way to test whether a wire is permanently
'live' from the AC breaker/fuse panel, is (switch on/off) switched
live, a neutral or a ground.

The mention of two 20 amp circuits 'connected together' is confusing.
It also might be confusing/unsafe for anyone working on that/those
circuits; my understanding is that once the breaker/fuse for a circuit
is off/removed there should be no other power (from another connection
circuit etc.) to anything on that circuit or in the same AC boxes.
That's a little worrying and possibly not up to code? Possibly an
insurance concern?

Maybe you mean two 'separate' 20 amp circuits; or is the breaker a
'double 20 amp' with the handles connected together so that both
breakers will trip at same time?????????


Were the lights functioning before and where/what
are you measuring?

One light was and on wasn't, I thought that may be it was because they
were old crappy florescent lights.

wrote:
Can anyone tell me why I would get a 27 volt reading on a 120v circuit.
I have a old home but some of the home has been re-wired. I am
remodeling my bath room and removed old florescent lights. I tested
the power at the connections and got a reading of 27v. I climbed in
the attic and it looks like the wire is coming from a junction box with
several other wires. It looks like the work was done by a pro. The
upstairs has 2-20amp (connected together) circuits.

my first thought is that you have your meter set at DC.

my second thought is that you are not using it correctly. one probe on
black, the other to the ground, then the first probe on the white.
(white should be zero, black 100-140V, unless i got em reversed in my
head)

another thought is that you are measuring voltage on a dead line (to
see if it is live before you work on it), and you are reading DC off of
other devices on the circuit. or you are reading 27 millivolts and are
picking up stray radio signals.

yet another thought is that you are reading oddball stuff off the
ballast, which does not equal yer usual voltages, thats why the ballast
is there. not sure though.

STILL yet another thought is your battery in your meter is dead.

does anyone notice I dont say any rubbish about meter loading? if the
meter is designed to read line voltage, it was designed to work at the
proper loads, maybe not perfect, but i'd point at the first few
thoughts before I'd even think of loading.

lets try to keep the common sense handy people

hope the OP replies, I betting my money on dead battery

Tater wrote:
wrote:
Can anyone tell me why I would get a 27 volt reading on a 120v circuit.
I have a old home but some of the home has been re-wired. I am
remodeling my bath room and removed old florescent lights. I tested
the power at the connections and got a reading of 27v. I climbed in
the attic and it looks like the wire is coming from a junction box with
several other wires. It looks like the work was done by a pro. The
upstairs has 2-20amp (connected together) circuits.

my first thought is that you have your meter set at DC.

my second thought is that you are not using it correctly. one probe on
black, the other to the ground, then the first probe on the white.
(white should be zero, black 100-140V, unless i got em reversed in my
head)

another thought is that you are measuring voltage on a dead line (to
see if it is live before you work on it), and you are reading DC off of
other devices on the circuit. or you are reading 27 millivolts and are
picking up stray radio signals.

yet another thought is that you are reading oddball stuff off the
ballast, which does not equal yer usual voltages, thats why the ballast
is there. not sure though.

STILL yet another thought is your battery in your meter is dead.

does anyone notice I dont say any rubbish about meter loading? if the
meter is designed to read line voltage, it was designed to work at the
proper loads, maybe not perfect, but i'd point at the first few
thoughts before I'd even think of loading.

lets try to keep the common sense handy people

hope the OP replies, I betting my money on dead battery

Tater thanks for your reply.

I have used this meter a lot over the years and it has always worked
when checking circuits. It works on other circuits in my home however
I tried as you suggested on a few different outlets. All but the line
in question reads as follows. Black wire about 122. White wire .694.
I am reading volts not mV and I do have my tester set to AC. The
battery indicator is not showing low but I haven't changed it in a long
time.

Doug Miller wrote:
Can anyone tell me why I would get a 27 volt reading on a 120v
circuit.
I have a old home but some of the home has been re-wired. I am
remodeling my bath room and removed old florescent lights. I
tested
the power at the connections and got a reading of 27v. I climbed
in
the attic and it looks like the wire is coming from a junction
box with
several other wires. It looks like the work was done by a pro.
The
upstairs has 2-20amp (connected together) circuits.

You are using a low impedance (resistance) meter ...

Precisely backwards...a _high_ impedance meter can load a circuit
and
read "phantom" voltages. For such tests of household wiring
circuits
an inexpensive analog meter is probably more reliable than the
digital.

Nope, *you've* got it backwards: high impedance = high sensitivity.
For
a meter with an impedance in the megohm range, it's very easy to
pick up
stray, "phantom" voltage readings.

Ummmm.... that's exactly what he said. What's "backwards"?

I usually place the terminals of a battery across my tongue. A sour taste
implies the battery is good. Haven't tried that technique as a test for
impedence. Maybe impudence.

Tater wrote:
wrote:
Can anyone tell me why I would get a 27 volt reading on a 120v circuit.
I have a old home but some of the home has been re-wired. I am
remodeling my bath room and removed old florescent lights. I tested
the power at the connections and got a reading of 27v. I climbed in
the attic and it looks like the wire is coming from a junction box with
several other wires. It looks like the work was done by a pro. The
upstairs has 2-20amp (connected together) circuits.

my first thought is that you have your meter set at DC.

my second thought is that you are not using it correctly. one probe on
black, the other to the ground, then the first probe on the white.
(white should be zero, black 100-140V, unless i got em reversed in my
head)

another thought is that you are measuring voltage on a dead line (to
see if it is live before you work on it), and you are reading DC off of
other devices on the circuit. or you are reading 27 millivolts and are
picking up stray radio signals.

yet another thought is that you are reading oddball stuff off the
ballast, which does not equal yer usual voltages, thats why the ballast
is there. not sure though.

STILL yet another thought is your battery in your meter is dead.

does anyone notice I dont say any rubbish about meter loading? if the
meter is designed to read line voltage, it was designed to work at the
proper loads, maybe not perfect, but i'd point at the first few
thoughts before I'd even think of loading.

lets try to keep the common sense handy people

hope the OP replies, I betting my money on dead battery

Tater thanks for your reply.

I have used this meter a lot over the years and it has always worked
when checking circuits. It works on other circuits in my home however
I tried as you suggested on a few different outlets. All but the line
in question reads as follows. Black wire about 122. White wire .694.
I am reading volts not mV and I do have my tester set to AC. The
battery indicator is not showing low but I haven't changed it in a long
time.

"Tater" wrote in
oups.com:


wrote:
Can anyone tell me why I would get a 27 volt reading on a 120v
circuit.
I have a old home but some of the home has been re-wired. I am
remodeling my bath room and removed old florescent lights. I tested
the power at the connections and got a reading of 27v. I climbed in
the attic and it looks like the wire is coming from a junction box
with several other wires. It looks like the work was done by a pro.
The upstairs has 2-20amp (connected together) circuits.

my first thought is that you have your meter set at DC.

my second thought is that you are not using it correctly. one probe on
black, the other to the ground, then the first probe on the white.
(white should be zero, black 100-140V, unless i got em reversed in my
head)

another thought is that you are measuring voltage on a dead line (to
see if it is live before you work on it), and you are reading DC off
of other devices on the circuit. or you are reading 27 millivolts and
are picking up stray radio signals.

yet another thought is that you are reading oddball stuff off the
ballast, which does not equal yer usual voltages, thats why the
ballast is there. not sure though.

STILL yet another thought is your battery in your meter is dead.

does anyone notice I dont say any rubbish about meter loading? if the
meter is designed to read line voltage, it was designed to work at the
proper loads, maybe not perfect, but i'd point at the first few
thoughts before I'd even think of loading.

lets try to keep the common sense handy people

hope the OP replies, I betting my money on dead battery



Well Tater, I'm never shy about admitting "...but I was wroooooong" :-)

Doug Miller spake thus:

In article m, David Nebenzahl wrote:

dpb spake thus:

Al Bundy wrote:

wrote in news:1161608374.490859.297690
:

Can anyone tell me why I would get a 27 volt reading on a 120v circuit.
I have a old home but some of the home has been re-wired. I am
remodeling my bath room and removed old florescent lights. I tested
the power at the connections and got a reading of 27v. I climbed in
the attic and it looks like the wire is coming from a junction box with
several other wires. It looks like the work was done by a pro. The
upstairs has 2-20amp (connected together) circuits.

You are using a low impedance (resistance) meter ...

Precisely backwards...a _high_ impedance meter can load a circuit and
read "phantom" voltages. For such tests of household wiring circuits
an inexpensive analog meter is probably more reliable than the digital.

Nope, *you've* got it backwards: high impedance = high sensitivity. For
a meter with an impedance in the megohm range, it's very easy to pick up
stray, "phantom" voltage readings.

Ummmm.... that's exactly what he said. What's "backwards"?

The part where he said "a high impedance meter can load a circuit". I
shoulda been more clear; a high-impedance meter reads phantom voltages
because it loads the circuit *less*, not more.


--
Just as McDonald's is where you go when you're hungry but don't really
care about the quality of your food, Wikipedia is where you go when
you're curious but don't really care about the quality of your knowledge.

- Matthew White's WikiWatch (http://users.erols.com/mwhite28/wikiwoo.htm)

Could be 27 milivolts, I've done that.

--

Christopher A. Young
You can't shout down a troll.
You have to starve them.
..

"Doug Miller" wrote in message
om...
In article .com,
wrote:
Can anyone tell me why I would get a 27 volt reading on a 120v
circuit.

Probably because you're using a digital voltmeter, which is reading a
very
very low amperage induced current in the conductor you're testing. Try
using
an analog meter instead, and you'll probably see -zero- volts.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

In article m, David Nebenzahl wrote:
Doug Miller spake thus:

In article m, David
Nebenzahl wrote:

dpb spake thus:

Al Bundy wrote:

wrote in news:1161608374.490859.297690
:

Can anyone tell me why I would get a 27 volt reading on a 120v circuit.
I have a old home but some of the home has been re-wired. I am
remodeling my bath room and removed old florescent lights. I tested
the power at the connections and got a reading of 27v. I climbed in
the attic and it looks like the wire is coming from a junction box with
several other wires. It looks like the work was done by a pro. The
upstairs has 2-20amp (connected together) circuits.

You are using a low impedance (resistance) meter ...

Precisely backwards...a _high_ impedance meter can load a circuit and
read "phantom" voltages. For such tests of household wiring circuits
an inexpensive analog meter is probably more reliable than the digital.

Nope, *you've* got it backwards: high impedance = high sensitivity. For
a meter with an impedance in the megohm range, it's very easy to pick up
stray, "phantom" voltage readings.

Ummmm.... that's exactly what he said. What's "backwards"?

The part where he said "a high impedance meter can load a circuit". I
shoulda been more clear; a high-impedance meter reads phantom voltages
because it loads the circuit *less*, not more.

Since when does a high impedance place less load on a circuit than a low
impedance??

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

On Tue, 24 Oct 2006 13:35:09 GMT, (Doug Miller)
wrote:

In article m, David Nebenzahl wrote:
Doug Miller spake thus:

In article m, David
Nebenzahl wrote:

dpb spake thus:

Al Bundy wrote:

wrote in news:1161608374.490859.297690
:

Can anyone tell me why I would get a 27 volt reading on a 120v circuit.
I have a old home but some of the home has been re-wired. I am
remodeling my bath room and removed old florescent lights. I tested
the power at the connections and got a reading of 27v. I climbed in
the attic and it looks like the wire is coming from a junction box with
several other wires. It looks like the work was done by a pro. The
upstairs has 2-20amp (connected together) circuits.

You are using a low impedance (resistance) meter ...

Precisely backwards...a _high_ impedance meter can load a circuit and
read "phantom" voltages. For such tests of household wiring circuits
an inexpensive analog meter is probably more reliable than the digital.

Nope, *you've* got it backwards: high impedance = high sensitivity. For
a meter with an impedance in the megohm range, it's very easy to pick up
stray, "phantom" voltage readings.

Ummmm.... that's exactly what he said. What's "backwards"?

The part where he said "a high impedance meter can load a circuit". I
shoulda been more clear; a high-impedance meter reads phantom voltages
because it loads the circuit *less*, not more.

Since when does a high impedance place less load on a circuit than a low
impedance??

Since "impedance" took on its current meaning.
--
62 days until the winter solstice celebration

Mark Lloyd
http://notstupid.laughingsquid.com

"How could you ask be to believe in God when there's
absolutely no evidence that I can see?" -- Jodie Foster

Doug Miller spake thus:

Since when does a high impedance place less load on a circuit than a low
impedance??

Instead of "impedance", substitute "resistance" (which is essentially
the same in this context) and then re-think the question: I'm assuming
you know enough about basic electricity to work it out for yourself.


--
Just as McDonald's is where you go when you're hungry but don't really
care about the quality of your food, Wikipedia is where you go when
you're curious but don't really care about the quality of your knowledge.

- Matthew White's WikiWatch (http://users.erols.com/mwhite28/wikiwoo.htm)

In article , Mark Lloyd wrote:
On Tue, 24 Oct 2006 13:35:09 GMT, (Doug Miller)
wrote:

In article m, David
Nebenzahl wrote:
Doug Miller spake thus:

In article m, David
Nebenzahl wrote:

dpb spake thus:

Al Bundy wrote:

wrote in news:1161608374.490859.297690
:

Can anyone tell me why I would get a 27 volt reading on a 120v circuit.
I have a old home but some of the home has been re-wired. I am
remodeling my bath room and removed old florescent lights. I tested
the power at the connections and got a reading of 27v. I climbed in
the attic and it looks like the wire is coming from a junction box with
several other wires. It looks like the work was done by a pro. The
upstairs has 2-20amp (connected together) circuits.

You are using a low impedance (resistance) meter ...

Precisely backwards...a _high_ impedance meter can load a circuit and
read "phantom" voltages. For such tests of household wiring circuits
an inexpensive analog meter is probably more reliable than the digital.

Nope, *you've* got it backwards: high impedance = high sensitivity. For
a meter with an impedance in the megohm range, it's very easy to pick up
stray, "phantom" voltage readings.

Ummmm.... that's exactly what he said. What's "backwards"?

The part where he said "a high impedance meter can load a circuit". I
shoulda been more clear; a high-impedance meter reads phantom voltages
because it loads the circuit *less*, not more.

Since when does a high impedance place less load on a circuit than a low
impedance??

Since "impedance" took on its current meaning.

Please explain.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

In article m, David Nebenzahl wrote:
Doug Miller spake thus:

Since when does a high impedance place less load on a circuit than a low
impedance??

Instead of "impedance", substitute "resistance" (which is essentially
the same in this context) and then re-think the question: I'm assuming
you know enough about basic electricity to work it out for yourself.

Perhaps we're actually arguing over the word "load". If by "load" you mean
"current draw", then I have no disagreement with you.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

On Tue, 24 Oct 2006 17:34:36 GMT, (Doug Miller)
wrote:

In article , Mark Lloyd wrote:
On Tue, 24 Oct 2006 13:35:09 GMT, (Doug Miller)
wrote:

In article m, David
Nebenzahl wrote:
Doug Miller spake thus:

In article m, David
Nebenzahl wrote:

dpb spake thus:

Al Bundy wrote:

wrote in news:1161608374.490859.297690
:

Can anyone tell me why I would get a 27 volt reading on a 120v circuit.
I have a old home but some of the home has been re-wired. I am
remodeling my bath room and removed old florescent lights. I tested
the power at the connections and got a reading of 27v. I climbed in
the attic and it looks like the wire is coming from a junction box with
several other wires. It looks like the work was done by a pro. The
upstairs has 2-20amp (connected together) circuits.

You are using a low impedance (resistance) meter ...

Precisely backwards...a _high_ impedance meter can load a circuit and
read "phantom" voltages. For such tests of household wiring circuits
an inexpensive analog meter is probably more reliable than the digital.

Nope, *you've* got it backwards: high impedance = high sensitivity. For
a meter with an impedance in the megohm range, it's very easy to pick up
stray, "phantom" voltage readings.

Ummmm.... that's exactly what he said. What's "backwards"?

The part where he said "a high impedance meter can load a circuit". I
shoulda been more clear; a high-impedance meter reads phantom voltages
because it loads the circuit *less*, not more.

Since when does a high impedance place less load on a circuit than a low
impedance??

Since "impedance" took on its current meaning.

Please explain.

Would you be saying you don't know what "impedance" means?

A high impedance source (such as that 27VAC probably is), is
essentially a voltage source in series with a resistor. The effect of
this is that any attempt to draw current from this source will lower
the voltage, potentially to near zero. Phone lines are like this.

A high impedance load (such as a digital meter or VTVOM/FETVOM) will
draw very little current from a source (not lowering the voltage very
much). Note that such a meter is necessary for some sensitive
electronic circuits (that would be disturbed by a low impedance load).

An analog meter on a high impedance source will give inconsistent
readings on different ranges, since it has a different impedance on
each range, loading the circuit differently. Adding a (120V 60W) light
bulb in parallel will make the impedance MUCH lower.
--
62 days until the winter solstice celebration

Mark Lloyd
http://notstupid.laughingsquid.com

"How could you ask be to believe in God when there's
absolutely no evidence that I can see?" -- Jodie Foster

In article , Mark Lloyd wrote:
On Tue, 24 Oct 2006 17:34:36 GMT, (Doug Miller)
wrote:

In article , Mark Lloyd
wrote:
On Tue, 24 Oct 2006 13:35:09 GMT, (Doug Miller)
wrote:

In article m, David
Nebenzahl wrote:
Doug Miller spake thus:

In article m, David
Nebenzahl wrote:

dpb spake thus:

Al Bundy wrote:

wrote in news:1161608374.490859.297690
:

Can anyone tell me why I would get a 27 volt reading on a 120v
circuit.
I have a old home but some of the home has been re-wired. I am
remodeling my bath room and removed old florescent lights. I tested
the power at the connections and got a reading of 27v. I climbed in
the attic and it looks like the wire is coming from a junction box
with
several other wires. It looks like the work was done by a pro. The
upstairs has 2-20amp (connected together) circuits.

You are using a low impedance (resistance) meter ...

Precisely backwards...a _high_ impedance meter can load a circuit and
read "phantom" voltages. For such tests of household wiring circuits
an inexpensive analog meter is probably more reliable than the digital.

Nope, *you've* got it backwards: high impedance = high sensitivity. For
a meter with an impedance in the megohm range, it's very easy to pick up
stray, "phantom" voltage readings.

Ummmm.... that's exactly what he said. What's "backwards"?

The part where he said "a high impedance meter can load a circuit". I
shoulda been more clear; a high-impedance meter reads phantom voltages
because it loads the circuit *less*, not more.

Since when does a high impedance place less load on a circuit than a low
impedance??

Since "impedance" took on its current meaning.

Please explain.

Would you be saying you don't know what "impedance" means?

Not at all -- and if by "a high impedance ... loads the circuit less" you mean
that a high impedance draws less current than a low impedance, I have no
disagreement with you.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

Precisely backwards...a _high_ impedance meter can load a circuit and
read "phantom" voltages.

Precisely backwards...a _high_ impedance meter can't load a circuit
and read "phantom" voltages.

On Tue, 24 Oct 2006 20:18:25 GMT, (Doug Miller)
wrote:

In article , Mark Lloyd wrote:
On Tue, 24 Oct 2006 17:34:36 GMT, (Doug Miller)
wrote:

In article , Mark Lloyd
wrote:
On Tue, 24 Oct 2006 13:35:09 GMT, (Doug Miller)
wrote:

In article m, David
Nebenzahl wrote:
Doug Miller spake thus:

In article m, David
Nebenzahl wrote:

dpb spake thus:

Al Bundy wrote:

wrote in news:1161608374.490859.297690
:

Can anyone tell me why I would get a 27 volt reading on a 120v
circuit.
I have a old home but some of the home has been re-wired. I am
remodeling my bath room and removed old florescent lights. I tested
the power at the connections and got a reading of 27v. I climbed in
the attic and it looks like the wire is coming from a junction box
with
several other wires. It looks like the work was done by a pro. The
upstairs has 2-20amp (connected together) circuits.

You are using a low impedance (resistance) meter ...

Precisely backwards...a _high_ impedance meter can load a circuit and
read "phantom" voltages. For such tests of household wiring circuits
an inexpensive analog meter is probably more reliable than the digital.

Nope, *you've* got it backwards: high impedance = high sensitivity. For
a meter with an impedance in the megohm range, it's very easy to pick up
stray, "phantom" voltage readings.

Ummmm.... that's exactly what he said. What's "backwards"?

The part where he said "a high impedance meter can load a circuit". I
shoulda been more clear; a high-impedance meter reads phantom voltages
because it loads the circuit *less*, not more.

Since when does a high impedance place less load on a circuit than a low
impedance??

Since "impedance" took on its current meaning.

Please explain.

Would you be saying you don't know what "impedance" means?

Not at all -- and if by "a high impedance ... loads the circuit less" you mean
that a high impedance draws less current than a low impedance,

That's what I meant.

I have no
disagreement with you.
--
62 days until the winter solstice celebration

Mark Lloyd
http://notstupid.laughingsquid.com

"How could you ask be to believe in God when there's
absolutely no evidence that I can see?" -- Jodie Foster

On Tue, 24 Oct 2006 17:10:17 -0400, wrote:


Precisely backwards...a _high_ impedance meter can load a circuit and
read "phantom" voltages.

Precisely backwards...a _high_ impedance meter can't load a circuit
and read "phantom" voltages.

Ambiguous language.

Can't load a circuit, and can't read "phantom" voltages.

OR

Can't load a circuit, and CAN read "phantom" voltages.
--
62 days until the winter solstice celebration

Mark Lloyd
http://notstupid.laughingsquid.com

"How could you ask be to believe in God when there's
absolutely no evidence that I can see?" -- Jodie Foster

My shop teacher used to have a sign "Danger, 100,000 ohms".

--

Christopher A. Young
You can't shout down a troll.
You have to starve them.
..

"David Nebenzahl" wrote in message
s.com...
Doug Miller spake thus:

Since when does a high impedance place less load on a circuit than a
low
impedance??

Instead of "impedance", substitute "resistance" (which is essentially
the same in this context) and then re-think the question: I'm assuming
you know enough about basic electricity to work it out for yourself.


--
Just as McDonald's is where you go when you're hungry but don't really
care about the quality of your food, Wikipedia is where you go when
you're curious but don't really care about the quality of your
knowledge.

- Matthew White's WikiWatch
(http://users.erols.com/mwhite28/wikiwoo.htm)

Finding the keyboard operational
Stormin Mormon entered:

My shop teacher used to have a sign "Danger, 100,000 ohms".

--

Christopher A. Young
You can't shout down a troll.
You have to starve them.
We used to keep the cleaning crew away from the benches with a sign that
said "Danger high impedance".
Bob

--?
--?
Coffee worth staying up for - NY Times
www.moondoggiecoffee.com

In article ,
Doug Miller wrote:
In article .com, wrote:
Can anyone tell me why I would get a 27 volt reading on a 120v circuit.

Probably because you're using a digital voltmeter, which is reading a very
very low amperage induced current in the conductor you're testing. Try using
an analog meter instead, and you'll probably see -zero- volts.

I've had only HORRIBLE experience with digital voltmeters (plural).

Please do say more about the problems with them.

And if some are OK, or even EXCELLENT -- what is it that
makes them that way -- as compared with the el-cheapo ones
that seem reliable only on DC (batteries, etc). AC -- forget
it.

(At least that's my experience.)

Thanks,

David

In article ,
Mark Lloyd wrote:
On Tue, 24 Oct 2006 17:34:36 GMT, (Doug Miller)
wrote:

....
....

You are using a low impedance (resistance) meter ...

Precisely backwards...a _high_ impedance meter can load a circuit and
read "phantom" voltages. For such tests of household wiring circuits
an inexpensive analog meter is probably more reliable than the digital.

Nope, *you've* got it backwards: high impedance = high sensitivity. For
a meter with an impedance in the megohm range, it's very easy to pick up
stray, "phantom" voltage readings.

Ummmm.... that's exactly what he said. What's "backwards"?

The part where he said "a high impedance meter can load a circuit". I
shoulda been more clear; a high-impedance meter reads phantom voltages
because it loads the circuit *less*, not more.

Since when does a high impedance place less load on a circuit than a low
impedance??

Since "impedance" took on its current meaning.

Please explain.

Would you be saying you don't know what "impedance" means?


---------------- question about *this* post:


#1:
A high impedance source (such as that 27VAC probably is), is
essentially a voltage source in series with a resistor. The effect of
this is that any attempt to draw current from this source will lower
the voltage, potentially to near zero. Phone lines are like this.

#2:
A high impedance load (such as a digital meter or VTVOM/FETVOM) will
draw very little current from a source (not lowering the voltage very
much). Note that such a meter is necessary for some sensitive
electronic circuits (that would be disturbed by a low impedance load).

#3:
An analog meter on a high impedance source will give inconsistent
readings on different ranges, since it has a different impedance on
each range, loading the circuit differently. Adding a (120V 60W) light
bulb in parallel will make the impedance MUCH lower.


About #1, please explain what effect the impedance of the "source" has on
this problem. (I'm sure it has one, just not sure what it is.)


About #2: You're trying to measure volts (as opposed to current);
thus you're putting the two leads "across" the load.

eg, you have an extension-cord onto which is plugged three
floor-lamps, a stereo, etc. So mentally you'd like
to rub off the outside insulation on the two wires
in the extension cord and touch your two leads there.

Obviously you want to NOT disturb the situation (by
merely measuring it), you want your meter to have
HIGH impedance -- so that only a TINY bit of current
runs through it.

Whereas one with low impedance (resistance here) would
get more (much more?) current running through it,
"disturbing" the situation.

So that sort of "proves" (well, restates) #2.


About #3: Here you mix in the source-concept with the meter.

Could you perhaps explain this part a bit more?


Thanks!

David

(Way, WAY back when, I recall the name "Thevenin's Theorem",
something to do with the source, maybe, but I surely
have no concept now (not sure I ever did back then!).)

David Combs wrote:

eg, you have an extension-cord onto which is plugged three
floor-lamps, a stereo, etc. So mentally you'd like
to rub off the outside insulation on the two wires
in the extension cord and touch your two leads there.



I was in Lowe's recently and heard this over the loud speaker:

"mr smith to aisle 6, wirecutting emergency"

mk5000

"The question is this: What is the best (or at least a good) way to
search all the
machines on a LAN for running instances of this COM object? (I've seen
SQL Server's
Enterprise Manager do something like this when adding a server
registration and
hitting the "..." button to select the server.)"--John Fisher

On Wed, 22 Nov 2006 02:00:50 +0000 (UTC), (David
Combs) wrote:

In article ,
Mark Lloyd wrote:
On Tue, 24 Oct 2006 17:34:36 GMT, (Doug Miller)
wrote:

...
...

You are using a low impedance (resistance) meter ...

Precisely backwards...a _high_ impedance meter can load a circuit and
read "phantom" voltages. For such tests of household wiring circuits
an inexpensive analog meter is probably more reliable than the digital.

Nope, *you've* got it backwards: high impedance = high sensitivity. For
a meter with an impedance in the megohm range, it's very easy to pick up
stray, "phantom" voltage readings.

Ummmm.... that's exactly what he said. What's "backwards"?

The part where he said "a high impedance meter can load a circuit". I
shoulda been more clear; a high-impedance meter reads phantom voltages
because it loads the circuit *less*, not more.

Since when does a high impedance place less load on a circuit than a low
impedance??

Since "impedance" took on its current meaning.

Please explain.

Would you be saying you don't know what "impedance" means?


---------------- question about *this* post:


#1:
A high impedance source (such as that 27VAC probably is), is
essentially a voltage source in series with a resistor. The effect of
this is that any attempt to draw current from this source will lower
the voltage, potentially to near zero. Phone lines are like this.

#2:
A high impedance load (such as a digital meter or VTVOM/FETVOM) will
draw very little current from a source (not lowering the voltage very
much). Note that such a meter is necessary for some sensitive
electronic circuits (that would be disturbed by a low impedance load).

#3:
An analog meter on a high impedance source will give inconsistent
readings on different ranges, since it has a different impedance on
each range, loading the circuit differently. Adding a (120V 60W) light
bulb in parallel will make the impedance MUCH lower.


About #1, please explain what effect the impedance of the "source" has on
this problem. (I'm sure it has one, just not sure what it is.)


I forgot what they CALL that, but any real voltage source can be
considered as an ideal voltage source (one that never changes voltage
under any load) in series with some impedance. That impedance
determines how much the voltage will drop when a load is applied.

BTW, one high impedance source people have is a phone line. 48VDC or
so, dropping to 6-10V when a phone is in use.

About #2: You're trying to measure volts (as opposed to current);
thus you're putting the two leads "across" the load.


Yes, that's how you measure voltage.

eg, you have an extension-cord onto which is plugged three
floor-lamps, a stereo, etc. So mentally you'd like
to rub off the outside insulation on the two wires
in the extension cord and touch your two leads there.

Obviously you want to NOT disturb the situation (by
merely measuring it), you want your meter to have
HIGH impedance -- so that only a TINY bit of current
runs through it.


Right.

Whereas one with low impedance (resistance here) would
get more (much more?) current running through it,
"disturbing" the situation.


An effect almost unnoticable when the voltages source has low
impedance.

So that sort of "proves" (well, restates) #2.


About #3: Here you mix in the source-concept with the meter.

Could you perhaps explain this part a bit more?


I found the idea of source impedance difficult to understand once.
Think of a 12V battery with an internal series resistor, where you
have NO access to the point between the battery and resistor. You just
measure the voltage at the terminals.

1. Measure the voltage with no load.

2. Measure the voltage with a load. This voltage will be lower than
the no-load voltage. The amount of this drop depends on the resistance
of that hidden resistor.

The load has resistance, which is in series with than internal
resistance. Voltage is divided between the series resistors, according
to resistance.

Real batteries aren't normally made with resistors, but they do have
some internal resistance and will show a voltage drop with load.

Impedance is like resistance, but with AC. It considers that some
components react differently to AC.

Where you read 120V with a DIGITAL meter, but 27V with an ANALOG
meter, you've found a high impedance source. When a wire that's not
connected is physically close to one with current in it, these wires
act as a transformer (not a very good one).


Thanks!

David

(Way, WAY back when, I recall the name "Thevenin's Theorem",
something to do with the source, maybe, but I surely
have no concept now (not sure I ever did back then!).)


--
33 days until the winter solstice celebration

Mark Lloyd
http://notstupid.laughingsquid.com

"I have found Christian dogma unintelligable. Early
in life I absented myself from Christian assemblies."
-- Benjamin Franklin