The back porch light stopped working, a new bulb didn't help.

So. I put a meter on the socket. 0 V.

I pulled the switch plate off (just a normal single pole). 80 V
terminal to terminal. Hmmm?

Killed the power, put an ohmeter terminal to terminal, infinite
resistance at both switch positions. Diagnosis bad switch, supported
by the fact that before it died completely, flipping the switch
several times made it work. Besides I've always had a CFL in that one
and I suspect the capacitor shortens the switch life due to arcing.

Okay, a new switch is $1.29, no big loss if wrong. Took the old
switch off, turned the power back on and checked wire to wire just for
grins, still 80 V. Uh oh.

Put the new switch in. Turned power on, checked the socket, 120 V.
Put bulb in, (CFL), lights up fine.

Well, I have a working porch light again, but I'm left with the 80 V
mystery. I don't know any way to get 80 V on a normal residential
power setup. The meter was a digital Radio Shack multimeter. If I'd
had time I'd have checked again with the Simpson analog, digitals
sometimes give funny readings, but I've never seen 80 V. What am I
missing?

TimR wrote in news:2fad4ded-a0ce-4fae-9166-
:

The back porch light stopped working, a new bulb didn't help.

So. I put a meter on the socket. 0 V.

I pulled the switch plate off (just a normal single pole). 80 V
terminal to terminal. Hmmm?

Killed the power, put an ohmeter terminal to terminal, infinite
resistance at both switch positions. Diagnosis bad switch, supported
by the fact that before it died completely, flipping the switch
several times made it work. Besides I've always had a CFL in that one
and I suspect the capacitor shortens the switch life due to arcing.

Okay, a new switch is $1.29, no big loss if wrong. Took the old
switch off, turned the power back on and checked wire to wire just for
grins, still 80 V. Uh oh.

Put the new switch in. Turned power on, checked the socket, 120 V.
Put bulb in, (CFL), lights up fine.

Well, I have a working porch light again, but I'm left with the 80 V
mystery. I don't know any way to get 80 V on a normal residential
power setup. The meter was a digital Radio Shack multimeter. If I'd
had time I'd have checked again with the Simpson analog, digitals
sometimes give funny readings, but I've never seen 80 V. What am I
missing?


A bad contact somewhere? Put a heavy load, an iron or vacuum cleaner on
it to make sure there is a solid feed.
If those work, stop worrying. If not, start worrying, and start checking
backward along the feed.
A lousy job, but loose contacts can cause a fire.

On May 15, 7:40*pm, Sjouke Burry s@b wrote:


A bad contact somewhere?

Not sure that makes sense.

Pulling a current across a resistance, like from a bad connection,
should cause a voltage drop. But no-load open circuit should be full
voltage.

TimR wrote:
The back porch light stopped working, a new bulb didn't help.

So. I put a meter on the socket. 0 V.

I pulled the switch plate off (just a normal single pole). 80 V
terminal to terminal. Hmmm?

Killed the power, put an ohmeter terminal to terminal, infinite
resistance at both switch positions. Diagnosis bad switch, supported
by the fact that before it died completely, flipping the switch
several times made it work. Besides I've always had a CFL in that one
and I suspect the capacitor shortens the switch life due to arcing.

Okay, a new switch is $1.29, no big loss if wrong. Took the old
switch off, turned the power back on and checked wire to wire just for
grins, still 80 V. Uh oh.

Put the new switch in. Turned power on, checked the socket, 120 V.
Put bulb in, (CFL), lights up fine.

Well, I have a working porch light again, but I'm left with the 80 V
mystery. I don't know any way to get 80 V on a normal residential
power setup. The meter was a digital Radio Shack multimeter. If I'd
had time I'd have checked again with the Simpson analog, digitals
sometimes give funny readings, but I've never seen 80 V. What am I
missing?

An old analog would likely show different voltages with each range. Carbon
in switch ??

Greg

TimR wrote:
The back porch light stopped working, a new bulb didn't help.

So. I put a meter on the socket. 0 V.

I pulled the switch plate off (just a normal single pole). 80 V
terminal to terminal. Hmmm?

Killed the power, put an ohmeter terminal to terminal, infinite
resistance at both switch positions. Diagnosis bad switch, supported
by the fact that before it died completely, flipping the switch
several times made it work. Besides I've always had a CFL in that one
and I suspect the capacitor shortens the switch life due to arcing.

Okay, a new switch is $1.29, no big loss if wrong. Took the old
switch off, turned the power back on and checked wire to wire just for
grins, still 80 V. Uh oh.

Put the new switch in. Turned power on, checked the socket, 120 V.
Put bulb in, (CFL), lights up fine.

Well, I have a working porch light again, but I'm left with the 80 V
mystery. I don't know any way to get 80 V on a normal residential
power setup. The meter was a digital Radio Shack multimeter. If I'd
had time I'd have checked again with the Simpson analog, digitals
sometimes give funny readings, but I've never seen 80 V. What am I
missing?

You cannot believe the accuracy of a multimeter with no load on the circuit.
The reason is too complicated to divulge here, but it's a fact.

If your meter reads anything above about five volts - when it should be
120 - it really IS 120.

"TimR" wrote in message
...
The back porch light stopped working, a new bulb didn't help.

So. I put a meter on the socket. 0 V.

I pulled the switch plate off (just a normal single pole). 80 V
terminal to terminal. Hmmm?

Killed the power, put an ohmeter terminal to terminal, infinite
resistance at both switch positions. Diagnosis bad switch, supported
by the fact that before it died completely, flipping the switch
several times made it work. Besides I've always had a CFL in that one
and I suspect the capacitor shortens the switch life due to arcing.

Okay, a new switch is $1.29, no big loss if wrong. Took the old
switch off, turned the power back on and checked wire to wire just for
grins, still 80 V. Uh oh.

Put the new switch in. Turned power on, checked the socket, 120 V.
Put bulb in, (CFL), lights up fine.

Well, I have a working porch light again, but I'm left with the 80 V
mystery. I don't know any way to get 80 V on a normal residential
power setup. The meter was a digital Radio Shack multimeter. If I'd
had time I'd have checked again with the Simpson analog, digitals
sometimes give funny readings, but I've never seen 80 V. What am I
missing?

It is often normal to get strange readings with a digital meter, as someone
said, too much to go into here. Short answer is the wiring is acting like a
capacitor or transformer and the high impedance of the meter is picking up
voltage with a very small current. Almost any load and the voltage will
dissapear.. If the bulb was still in the circuit, it may be a small ammount
of feed through in the CFL.

On Tue, 15 May 2012 16:21:14 -0700 (PDT), TimR
wrote:

The back porch light stopped working, a new bulb didn't help.

So. I put a meter on the socket. 0 V.

I pulled the switch plate off (just a normal single pole). 80 V
terminal to terminal. Hmmm?

Killed the power, put an ohmeter terminal to terminal, infinite
resistance at both switch positions. Diagnosis bad switch, supported
by the fact that before it died completely, flipping the switch
several times made it work. Besides I've always had a CFL in that one
and I suspect the capacitor shortens the switch life due to arcing.

Okay, a new switch is $1.29, no big loss if wrong. Took the old
switch off, turned the power back on and checked wire to wire just for
grins, still 80 V. Uh oh.

Put the new switch in. Turned power on, checked the socket, 120 V.
Put bulb in, (CFL), lights up fine.

Well, I have a working porch light again, but I'm left with the 80 V
mystery. I don't know any way to get 80 V on a normal residential
power setup. The meter was a digital Radio Shack multimeter. If I'd
had time I'd have checked again with the Simpson analog, digitals
sometimes give funny readings, but I've never seen 80 V. What am I
missing?
80 volts terminal to terminal on the switch means 80 volt drop across
the bulb. Same with switch o or off means the switch was no good. Feed
to ground would read approxemately 120 volts. With bad switch load to
ground would read zero. Good switch, load to ground 120.

Sometimes, with no load, a digital meter will pick up a
"ghost load" reading. Or ghost voltage, can't remember.
The two wires next to each other have a very slight
transformer effect. Not enough to light a bulb, but
enough to read with a DMM.

Christopher A. Young
Learn more about Jesus
www.lds.org
..

"TimR" wrote in message
...
The back porch light stopped working, a new bulb didn't help.

So. I put a meter on the socket. 0 V.

I pulled the switch plate off (just a normal single pole). 80 V
terminal to terminal. Hmmm?

Killed the power, put an ohmeter terminal to terminal, infinite
resistance at both switch positions. Diagnosis bad switch, supported
by the fact that before it died completely, flipping the switch
several times made it work. Besides I've always had a CFL in that one
and I suspect the capacitor shortens the switch life due to arcing.

Okay, a new switch is $1.29, no big loss if wrong. Took the old
switch off, turned the power back on and checked wire to wire just for
grins, still 80 V. Uh oh.

Put the new switch in. Turned power on, checked the socket, 120 V.
Put bulb in, (CFL), lights up fine.

Well, I have a working porch light again, but I'm left with the 80 V
mystery. I don't know any way to get 80 V on a normal residential
power setup. The meter was a digital Radio Shack multimeter. If I'd
had time I'd have checked again with the Simpson analog, digitals
sometimes give funny readings, but I've never seen 80 V. What am I
missing?

On 15 May 2012 23:40:33 GMT, Sjouke Burry s@b wrote:

TimR wrote in news:2fad4ded-a0ce-4fae-9166-
:

The back porch light stopped working, a new bulb didn't help.

So. I put a meter on the socket. 0 V.

I pulled the switch plate off (just a normal single pole). 80 V
terminal to terminal. Hmmm?

Killed the power, put an ohmeter terminal to terminal, infinite
resistance at both switch positions. Diagnosis bad switch, supported
by the fact that before it died completely, flipping the switch
several times made it work. Besides I've always had a CFL in that one
and I suspect the capacitor shortens the switch life due to arcing.

Okay, a new switch is $1.29, no big loss if wrong. Took the old
switch off, turned the power back on and checked wire to wire just for
grins, still 80 V. Uh oh.

Put the new switch in. Turned power on, checked the socket, 120 V.
Put bulb in, (CFL), lights up fine.

Well, I have a working porch light again, but I'm left with the 80 V
mystery. I don't know any way to get 80 V on a normal residential
power setup. The meter was a digital Radio Shack multimeter. If I'd
had time I'd have checked again with the Simpson analog, digitals
sometimes give funny readings, but I've never seen 80 V. What am I
missing?


A bad contact somewhere? Put a heavy load, an iron or vacuum cleaner on
it to make sure there is a solid feed.
If those work, stop worrying. If not, start worrying, and start checking
backward along the feed.
A lousy job, but loose contacts can cause a fire.
Just learn how to use the meter.

On Tue, 15 May 2012 17:07:58 -0700 (PDT), TimR
wrote:

On May 15, 7:40Â*pm, Sjouke Burry s@b wrote:


A bad contact somewhere?

Not sure that makes sense.

Pulling a current across a resistance, like from a bad connection,
should cause a voltage drop. But no-load open circuit should be full
voltage.
OP said they measured across the switch.

Learn how to use a meter for troubleshooting, and what the reading
mean.

The problem IS FIXED. There was a BAD SWITCH.

On Tue, 15 May 2012 19:57:53 -0500, "HeyBub"
wrote:

TimR wrote:
The back porch light stopped working, a new bulb didn't help.

So. I put a meter on the socket. 0 V.

I pulled the switch plate off (just a normal single pole). 80 V
terminal to terminal. Hmmm?

Killed the power, put an ohmeter terminal to terminal, infinite
resistance at both switch positions. Diagnosis bad switch, supported
by the fact that before it died completely, flipping the switch
several times made it work. Besides I've always had a CFL in that one
and I suspect the capacitor shortens the switch life due to arcing.

Okay, a new switch is $1.29, no big loss if wrong. Took the old
switch off, turned the power back on and checked wire to wire just for
grins, still 80 V. Uh oh.

Put the new switch in. Turned power on, checked the socket, 120 V.
Put bulb in, (CFL), lights up fine.

Well, I have a working porch light again, but I'm left with the 80 V
mystery. I don't know any way to get 80 V on a normal residential
power setup. The meter was a digital Radio Shack multimeter. If I'd
had time I'd have checked again with the Simpson analog, digitals
sometimes give funny readings, but I've never seen 80 V. What am I
missing?

You cannot believe the accuracy of a multimeter with no load on the circuit.
The reason is too complicated to divulge here, but it's a fact.

If your meter reads anything above about five volts - when it should be
120 - it really IS 120.

The OP stated "I pulled the switch plate off (just a normal single
pole). 80 V terminal to terminal. Hmmm?"

What's wrong with this situation?
What is being measured?
What is indicated by the fact there is no voltage at the socket and 80
volts across the switch?
Don't need to be a member of MENSA to figure this one out.
The voltage reading is likely accurate - accurate enough, anyway. Just
so happens it is immaterial because it is not a valid measurement. The
voltmeter was being used as an ammeter instead of a voltmeter.

On Tue, 15 May 2012 21:14:57 -0400, "Ralph Mowery"
wrote:


"TimR" wrote in message
...
The back porch light stopped working, a new bulb didn't help.

So. I put a meter on the socket. 0 V.

I pulled the switch plate off (just a normal single pole). 80 V
terminal to terminal. Hmmm?

Killed the power, put an ohmeter terminal to terminal, infinite
resistance at both switch positions. Diagnosis bad switch, supported
by the fact that before it died completely, flipping the switch
several times made it work. Besides I've always had a CFL in that one
and I suspect the capacitor shortens the switch life due to arcing.

Okay, a new switch is $1.29, no big loss if wrong. Took the old
switch off, turned the power back on and checked wire to wire just for
grins, still 80 V. Uh oh.

Put the new switch in. Turned power on, checked the socket, 120 V.
Put bulb in, (CFL), lights up fine.

Well, I have a working porch light again, but I'm left with the 80 V
mystery. I don't know any way to get 80 V on a normal residential
power setup. The meter was a digital Radio Shack multimeter. If I'd
had time I'd have checked again with the Simpson analog, digitals
sometimes give funny readings, but I've never seen 80 V. What am I
missing?

It is often normal to get strange readings with a digital meter, as someone
said, too much to go into here. Short answer is the wiring is acting like a
capacitor or transformer and the high impedance of the meter is picking up
voltage with a very small current. Almost any load and the voltage will
dissapear.. If the bulb was still in the circuit, it may be a small ammount
of feed through in the CFL.

Short answer is the voltmeter was not being used properly, and the
longer answer is nobody else here caught it.
Nothing to do with inacuracies of digital meters - totally a case of
not knowing how to use a meter to troubleshoot - or knowing how to
interpret the readings when the meter is mis-connected.

The readings are accurate

On Tue, 15 May 2012 21:44:22 -0400, wrote:

A bad contact somewhere? Put a heavy load, an iron or vacuum cleaner on
it to make sure there is a solid feed.
If those work, stop worrying. If not, start worrying, and start checking
backward along the feed.
A lousy job, but loose contacts can cause a fire.
Just learn how to use the meter.

Don't you have a vacuum cleaner in your tool kit?

wrote:

It is often normal to get strange readings with a digital meter, as
someone said, too much to go into here. Short answer is the wiring
is acting like a capacitor or transformer and the high impedance of
the meter is picking up voltage with a very small current. Almost
any load and the voltage will dissapear.. If the bulb was still in
the circuit, it may be a small ammount of feed through in the CFL.

Short answer is the voltmeter was not being used properly, and the
longer answer is nobody else here caught it.
Nothing to do with inacuracies of digital meters - totally a case of
not knowing how to use a meter to troubleshoot - or knowing how to
interpret the readings when the meter is mis-connected.

The readings are accurate

The readings are NOT accurate. The indicated voltage is a phantom.

Consider your assertion that the meter is "mis-connected:" The meter has two
probes. There are two wires. There are two and only two possible ways to
connect the meter and the wires. Which of the two, according to you, is the
correct way to connect all this stuff? If both of the two possibilities
yield the same result, where is the "mis-connection"?

wrote:
80 volts terminal to terminal on the switch means 80 volt drop across
the bulb. Same with switch o or off means the switch was no good. Feed
to ground would read approxemately 120 volts. With bad switch load to
ground would read zero. Good switch, load to ground 120.

Huh?

By definition, with a functioning switch energized, both sides MUST read the
same and that "same" must be zero. With the switch in the OFF position, and
using a digital voltmeter, you can get any reading from zero to 120.

On May 15, 7:21*pm, TimR wrote:
The back porch light stopped working, a new bulb didn't help.

So. *I put a meter on the socket. *0 V.

I pulled the switch plate off (just a normal single pole). *80 V
terminal to terminal. *Hmmm?

Killed the power, put an ohmeter terminal to terminal, infinite
resistance at both switch positions. *Diagnosis bad switch, supported
by the fact that before it died completely, flipping the switch
several times made it work. *Besides I've always had a CFL in that one
and I suspect the capacitor shortens the switch life due to arcing.

Okay, a new switch is $1.29, no big loss if wrong. *Took the old
switch off, turned the power back on and checked wire to wire just for
grins, still 80 V. *Uh oh.

Put the new switch in. *Turned power on, checked the socket, 120 V.
Put bulb in, (CFL), lights up fine.

Well, I have a working porch light again, but I'm left with the 80 V
mystery. *I don't know any way to get 80 V on a normal residential
power setup. *The meter was a digital Radio Shack multimeter. *If I'd
had time I'd have checked again with the Simpson analog, digitals
sometimes give funny readings, but I've never seen 80 V. *What am I
missing?

If you measured across the two wires that were connected to the
switch, you're measuring the potential from hot *through the bulb* to
neutral. If you want to sleep better, pull the switch off again and
measure from hot to ground, you should then read 120V or thereabouts.
If the bulb is a CFL there may be some odd effects causing an
incorrect voltage reading the way you measured it.

nate

On May 15, 8:07*pm, TimR wrote:
On May 15, 7:40*pm, Sjouke Burry s@b wrote:



A bad contact somewhere?

Not sure that makes sense.

Pulling a current across a resistance, like from a bad connection,
should cause a voltage drop. *But *no-load open circuit should be full
voltage.

You were pulling a current through that circuit and
it had two resistances in it. One presumably was the
light bulb, otherwise measuring from terminal to
terminal of the open switch should not read anything..
The other resistance is that of the multimeter itself.
How much of the 120V in the circuit appears
across the bulb and how much across
the multimeter is proportional to their resistance.
I would expect the multimeter to have such a high
resistance that you'd read close to 120V. But with
a CFL presented with a tiny current, not able to light,
who knows what that resistance/impedance is.

On 5/16/2012 5:48 AM, HeyBub wrote:
wrote:

It is often normal to get strange readings with a digital meter, as
someone said, too much to go into here. Short answer is the wiring
is acting like a capacitor or transformer and the high impedance of
the meter is picking up voltage with a very small current. Almost
any load and the voltage will dissapear.. If the bulb was still in
the circuit, it may be a small ammount of feed through in the CFL.

Short answer is the voltmeter was not being used properly, and the
longer answer is nobody else here caught it.
Nothing to do with inacuracies of digital meters - totally a case of
not knowing how to use a meter to troubleshoot - or knowing how to
interpret the readings when the meter is mis-connected.

The readings are accurate

The readings are NOT accurate. The indicated voltage is a phantom.

Consider your assertion that the meter is "mis-connected:" The meter has two
probes. There are two wires. There are two and only two possible ways to
connect the meter and the wires. Which of the two, according to you, is the
correct way to connect all this stuff? If both of the two possibilities
yield the same result, where is the "mis-connection"?


The OP was measuring across an open switch with no load (no bulb). One
might expect zero volts. What was measured was a "phantom" voltage, as
Hey says, caused by capacitance between switched and neutral wires to
the light and the high impedance of the meter as Ralph said. It is a
rather well know quirk (inaccuracy) of digital meters.

The measurement across the switch would be meaningful with an
incandescent bulb installed. Or a low impedance meter would measure zero
volts (which would tell the OP nothing).

--
bud--

I started with the assumption the switch was bad, did the checking
mostly out of curiosity (and of course, when trying to figure out
which breaker controls the circuit and the light is NOT working, it's
handy to have a way to know).

And yes I've had trouble with digital meters and phantom results on no
load circuits, that's why I asked (and why I have a Simpson on the
shelf, but unwinding all those probe wires is a pain, not as bad as
winding them up to get them back in the case though).

But on 120 V circuits normally that meter reads okay or floats a bit.

I left out a couple of things. The fixture had no lamp in it, so that
circuit should be open. The kitchen lights are on the same circuit,
they went out when I got the right breaker (if I'd known that ahead of
time I wouldn't need a meter, technically).

The 80V terminal to terminal on the switch was with the switch off AND
no lamp in the fixture. With switch on, it went to 0 as I'd expect.
It was consistent with several measurements and was the same as wire
to wire with the switch removed (and still no lamp in the fixture).
That surprised me. And then when I went outside and put the same
meter on the fixture and got 120 V I was suprised again.

After work tonight I'll put the analog on it and see.

On May 16, 7:48*am, "HeyBub" wrote:
wrote:

It is often normal to get strange readings with a digital meter, as
someone said, too much to go into here. *Short answer is the wiring
is acting like a capacitor or transformer and the high impedance of
the meter is picking up voltage with a very small current. *Almost
any load and the voltage will dissapear.. *If the bulb was still in
the circuit, it may be a small ammount of feed through in the CFL.

Short answer is the voltmeter was not being used properly, and the
longer answer is nobody else here caught it.
Nothing to do with inacuracies of digital meters - totally a case of
not knowing how to use a meter to troubleshoot - *or knowing how to
interpret the readings when the meter is mis-connected.

The readings are accurate

The readings are NOT accurate. The indicated voltage is a phantom.

Consider your assertion that the meter is "mis-connected:" The meter has two
probes. There are two wires. There are two and only two possible ways to
connect the meter and the wires. Which of the two, according to you, is the
correct way to connect all this stuff? If both of the two possibilities
yield the same result, where is the "mis-connection"?- Hide quoted text -

- Show quoted text -

I would have tested for 120V using one test lead
on the light side of the switch and the other held
to ground. I'd use ground because that's usually
there and available without taking anything apart.
Or he could have tested from the light side of
the switch to neutral.

"TimR" wrote in message
...

The 80V terminal to terminal on the switch was with the switch off AND
no lamp in the fixture. With switch on, it went to 0 as I'd expect.
It was consistent with several measurements and was the same as wire
to wire with the switch removed (and still no lamp in the fixture).
That surprised me. And then when I went outside and put the same
meter on the fixture and got 120 V I was suprised again.

After work tonight I'll put the analog on it and see.

One thing that you can also try with the analog is to set it to the highest
voltage scale. If you show anything that is less than the next scale down,
switch to that scale, the meter will stay almost the same physical place if
a 'phantom voltage', you can then go to the next lower scale and the meter
will not move much from the same physical point.
The actual voltage the meter reads will be differant, but the physical
point will not move much.


This digital vers analog comes up almost as much as the WD-40 being oil or
not.

wrote in message
...
I would have tested for 120V using one test lead
on the light side of the switch and the other held
to ground. I'd use ground because that's usually
there and available without taking anything apart.
Or he could have tested from the light side of
the switch to neutral.

Many times there is no neutral at the light switch or if it is, it is not
broken and easy to get a meter lead on.

I also try not to test to ground as sometimes the ground wire is left out.

On May 16, 11:57*am, "Ralph Mowery"
wrote:
wrote in message

...

I would have tested for 120V using one test lead
on the light side of the switch and the other held
to ground. *I'd use ground because that's usually
there and available without taking anything apart.
Or he could have tested from the light side of
the switch to neutral.

Many times there is no neutral at the light switch or if it is, it is not
broken and easy to get a meter lead on.

I also try not to test to ground as sometimes the ground wire is left out..

Well if you don't like using ground and a neutral is no
good because you have to take off a wire nut, how
would you propose to do the test?

On Wed, 16 May 2012 08:19:29 -0700 (PDT), TimR
wrote:

I started with the assumption the switch was bad, did the checking
mostly out of curiosity (and of course, when trying to figure out
which breaker controls the circuit and the light is NOT working, it's
handy to have a way to know).

Test the bad switch with an ohm meter

And yes I've had trouble with digital meters and phantom results on no
load circuits, that's why I asked (and why I have a Simpson on the
shelf, but unwinding all those probe wires is a pain, not as bad as
winding them up to get them back in the case though).

But on 120 V circuits normally that meter reads okay or floats a bit.

I left out a couple of things. The fixture had no lamp in it, so that
circuit should be open. The kitchen lights are on the same circuit,
they went out when I got the right breaker (if I'd known that ahead of
time I wouldn't need a meter, technically).

The 80V terminal to terminal on the switch was with the switch off AND
no lamp in the fixture. With switch on, it went to 0 as I'd expect.
It was consistent with several measurements and was the same as wire
to wire with the switch removed (and still no lamp in the fixture).
That surprised me. And then when I went outside and put the same
meter on the fixture and got 120 V I was suprised again.

After work tonight I'll put the analog on it and see.

wrote in message
...
Many times there is no neutral at the light switch or if it is, it is not
broken and easy to get a meter lead on.

I also try not to test to ground as sometimes the ground wire is left
out.

Well if you don't like using ground and a neutral is no
good because you have to take off a wire nut, how
would you propose to do the test?

Often in a light switch there is no neutral to have a wire nut to take off.

If there is no neutral or I suspect the ground is not connected, I use what
some may call a 'hot stick'. It is a device about the size of a cigar that
lights up and/or beebs when held next to a wire that has voltage on it.
Cutting the breaker off and on while using the hot stick usually confirms
there is power or no power at the switch. Then with the power off, I check
the switch using the ohms fuction.

I often use a Simpson 260 because I do not like the digital meters for
general testing due to the 'phantom' voltages. Another favorite is a Fluke
T2. I think that is the number. It has about 10 LEDs in it. It will check
from about 6 volts to 600 volts AC/DC and also low resistances. Just hook
up the test leads and it will show if you have power or a short.

I do admitt that I have several differant testers that most home owners do
not normally have or really need.
I also have a Fluke 87 digital meter, but seldom use it for electrical test
due to the 'phantom ' voltages. I work in industry where I have to deal
with anything from low voltage control and instruments to 480 volt 3 phase
circuits. That is the reason for having those plus several other testing
devices.

On May 16, 1:00*pm, "Ralph Mowery" wrote:
wrote in message

...

Many times there is no neutral at the light switch or if it is, it is not
broken and easy to get a meter lead on.

I also try not to test to ground as sometimes the ground wire is left
out.
Well if you don't like using ground and a neutral is no
good because you have to take off a wire nut, how
would you propose to do the test?

Often in a light switch there is no neutral to have a wire nut to take off.

Round these parts, the vast majority of them do
have neutrals. Usually the power feeds from the
panel to the switch via a romex that has both
conductors. Current NEC code now requires that
they have neutrals.

But that is why I said to just test it by holding one
lead to ground. And again, around here the vast
majority have grounds.




If there is no neutral or I suspect the ground is not connected, I use what
some may call a 'hot stick'. *It is a device about the size of a cigar that
lights up and/or beebs when held next to a wire that has voltage on it.

Yes, he could use one of those if he happened to
have it.




Cutting the breaker off and on while using the hot stick usually confirms
there is power or no power at the switch. *Then with the power off, I check
the switch using the ohms fuction.

Agree, he could do that too.




I often use a Simpson 260 because I do not like the digital meters for
general testing due to the 'phantom' voltages. *Another favorite is a Fluke
T2. *I think that is the number. *It has about 10 LEDs in it. *It will check
from about 6 volts to 600 volts AC/DC and also low resistances. *Just hook
up the test leads and it will show if you have power or a short.

I do admitt that I have several differant testers that most home owners do
not normally have or really need.
I also have a Fluke 87 digital meter, but seldom use it for electrical test
due to the 'phantom ' voltages. *I work in industry where I have to deal
with anything from low voltage control and instruments to 480 volt 3 phase
circuits. *That is the reason for having those plus several other testing
devices.

The phantom voltage issue is more of a problem
of people having a lack of understanding of circuit
fundamentals. The OP's test procedure being an
example. I don't think either of us would have
tested it the way he did. If you understand how circuits
work, it may cause you to do a second test, etc, but it's
not really confusing.

On May 16, 11:19*am, TimR wrote:
I started with the assumption the switch was bad, did the checking
mostly out of curiosity (and of course, when trying to figure out
which breaker controls the circuit and the light is NOT working, it's
handy to have a way to know).

And yes I've had trouble with digital meters and phantom results on no
load circuits, that's why I asked (and why I have a Simpson on the
shelf, but unwinding all those probe wires is a pain, not as bad as
winding them up to get them back in the case though).

But on 120 V circuits normally that meter reads okay or floats a bit.

I left out a couple of things. *The fixture had no lamp in it, so that
circuit should be open. *The kitchen lights are on the same circuit,
they went out when I got the right breaker (if I'd known that ahead of
time I wouldn't need a meter, technically).

The 80V terminal to terminal on the switch was with the switch off AND
no lamp in the fixture. *With switch on, it went to 0 as I'd expect.
It was consistent with several measurements and was the same as wire
to wire with the switch removed (and still no lamp in the fixture).
That surprised me. *And then when I went outside and put the same
meter on the fixture and got 120 V I was suprised again.

After work tonight I'll put the analog on it and see.

Well if the fixture had no lamp in it you should have read 0V no
matter the position of the switch. The 80V you read was some kind of
phantom voltage.

nate

"bud--" wrote in message
...

I am a lot more paranoid about possible failures and arc flash after
seeing some videos. Measuring on high capacity circuits, the meters should
be "category" rated. OSHA is likely to take a dim view of using not-cat
rated meters on high capacity circuits, particularly if there is an
injury. Fluke is likely to be cat rated. Not sure any Simpson 260s are.
Digital is also nice because it is more compact. (I coveted a 260 when I
was about jr high school and finally got one at a garage sale recently.)


I do not know what year the cat ratings came out. The Simpsons I have are
way too old for that. Where I work the meters are furnished by the company
and the Flukes are rated for cat 3 and 4 if you have the fuses in them Fluke
recommends for replacement if blown. I have seen a few films on arc flash.
We even have a long coat and face shield to use while working on some
circuits. There are differant levels of protection ranging from long sleeve
natural fiber shirts to heavy coats and face protection.

While I would use one around the house, I am not sure what the ratings if
any are on the meters that I have seen sell for around $ 5 to $ 15.
I just would not use one on the stuff where I work that has very high
current capacity. I do feel safe with the old Simpsons and the newer ones
do have a cat rating.

If you want to see something scarry, I have a few pix of the after math of a
460 volt 3 phase motor starter panel that blew up when a 15 amp breaker was
turned on. It was fed with a main breaker of about 600 amps.
I did not turn it on or see it hapen,but it was where I work.

On 5/16/2012 11:33 AM, wrote:
On May 16, 1:00 pm, "Ralph wrote:
wrote in message

I often use a Simpson 260 because I do not like the digital meters for
general testing due to the 'phantom' voltages. Another favorite is a Fluke
T2. I think that is the number. It has about 10 LEDs in it. It will check
from about 6 volts to 600 volts AC/DC and also low resistances. Just hook
up the test leads and it will show if you have power or a short.

I do admitt that I have several differant testers that most home owners do
not normally have or really need.
I also have a Fluke 87 digital meter, but seldom use it for electrical test
due to the 'phantom ' voltages. I work in industry where I have to deal
with anything from low voltage control and instruments to 480 volt 3 phase
circuits. That is the reason for having those plus several other testing
devices.

I thought having many test devices was about having the most toys when
you die...

I am a lot more paranoid about possible failures and arc flash after
seeing some videos. Measuring on high capacity circuits, the meters
should be "category" rated. OSHA is likely to take a dim view of using
not-cat rated meters on high capacity circuits, particularly if there is
an injury. Fluke is likely to be cat rated. Not sure any Simpson 260s
are. Digital is also nice because it is more compact. (I coveted a 260
when I was about jr high school and finally got one at a garage sale
recently.)

If using a Fluke, or similar, you can substantially eliminate phantom
voltage with an accessory:
http://www.fluke.com/Fluke/usen/Acce....htm?PID=56696


The phantom voltage issue is more of a problem
of people having a lack of understanding of circuit
fundamentals. The OP's test procedure being an
example. I don't think either of us would have
tested it the way he did. If you understand how circuits
work, it may cause you to do a second test, etc, but it's
not really confusing.

On the other hand, the test would have been fine if there was an
incandescent light bulb in the socket.

I agree about circuit fundamentals, and part of that is understanding
the limitations of measuring tools (like phantom voltage).

I remember the first time I saw the effect described by Ralph where the
voltage reads about the same point on the scale on different analog
ranges. I figured it out pretty fast, but it is weird.

--
bud--

Well, I tried again.

I actually do know how wiring normally works, but that doesn't prevent
me from having a brain fart in the middle of a project.

So, bulb (CFL) in, take some measurements off the two terminals of the
switch. (note, neither switch nor box appears to be grounded; with
switch off I can't pull any voltage from either terminal to box or
ground screw on switch, and only two wires enter the box, both look to
be #12 solid, one black and one white)

Switch on. Both terminals should be at same potential, meters should
read zero. Simpson 270 reads 0, R/S digital reads roughly 10 - 14,
floats a bit.

Switch off. One terminal should be hot, one terminal should be
grounded through the lamp. Simpson reads 124, digital reads 121.

Okay, now unscrew the bulb and repeat.

Switch on, meters should read 0. Yup, both do.

Switch off. What should they read? One is hot with respect to
ground, but there is no ground in the box. The other is nothing, it
is theoretically not grounded through the lamp but just a piece of
metal in thin air. No current could flow, so intuitively the voltage
difference should be zero, but I guess since we really don't know what
potential that wire is sitting on it could be anything.

R/S digital reads 84 V. Simpson reads 25 V.

Which, if either, is real? The R/S will sometimes give me 10 V on
just one probe, if the other is capacitatively coupled, but I've never
seen phantom voltages off the analog.

I guess the test would be to put a load on and see if I could draw a
current, but I've spent enough time on this and there are other
honeydoes to get to.

On Wed, 16 May 2012 06:48:49 -0500, "HeyBub"
wrote:

wrote:

It is often normal to get strange readings with a digital meter, as
someone said, too much to go into here. Short answer is the wiring
is acting like a capacitor or transformer and the high impedance of
the meter is picking up voltage with a very small current. Almost
any load and the voltage will dissapear.. If the bulb was still in
the circuit, it may be a small ammount of feed through in the CFL.

Short answer is the voltmeter was not being used properly, and the
longer answer is nobody else here caught it.
Nothing to do with inacuracies of digital meters - totally a case of
not knowing how to use a meter to troubleshoot - or knowing how to
interpret the readings when the meter is mis-connected.

The readings are accurate

The readings are NOT accurate. The indicated voltage is a phantom.

Consider your assertion that the meter is "mis-connected:" The meter has two
probes. There are two wires. There are two and only two possible ways to
connect the meter and the wires. Which of the two, according to you, is the
correct way to connect all this stuff? If both of the two possibilities
yield the same result, where is the "mis-connection"?

OK Bub - I'm make it REAL simple. And I'll type slowly so you can
understand. A switch is in series with the load. The switch has 2
contacts. Both contacts are on the "live" wire, because the neutral is
not switched. The OP measured the voltage from one terminal of the
switch to the other. IF the bulb was not in the socket, the voltage
would be ZERO, with the switch on or off. If there was an incandescent
bulb in the socket, the voltage would be line voltage - roughly 120
volts, with the switch OFF, and ZERO with the switch on. - if the
switch was any good.

However, the OP had a CFL in the socket, so thecapacitance etc. of the
electronic ballast was dropping about 40 volts across it with the
extremely low current flowing through the meter - and because the
switch was shot, the reading was the same both ways. If the switch had
been good, he would have found 80 volts across the open switch, and
ZERO across the closed switch, with the CFL lit.

The CORRECT way to test the line voltage is line to neutral, or line
to ground. If there is any ground at all the digital meter will read
the same either way, within a tenth of a volt,

I happen to have made my living using test meters for quite a few
years, so I knowwhat the OP did, what he should have done, and exactly
what the meter readings he gor mean.

You obviously do not.

On Wed, 16 May 2012 06:52:30 -0500, "HeyBub"
wrote:

wrote:
80 volts terminal to terminal on the switch means 80 volt drop across
the bulb. Same with switch o or off means the switch was no good. Feed
to ground would read approxemately 120 volts. With bad switch load to
ground would read zero. Good switch, load to ground 120.

Huh?

By definition, with a functioning switch energized, both sides MUST read the
same and that "same" must be zero. With the switch in the OFF position, and
using a digital voltmeter, you can get any reading from zero to 120.


You don't read to good, Bub. I said from one terminal of the switch to
GROUND or neutral. Live side th ground will always be aprox 120.
Switched side to ground will be zero with the switch off, and 120 with
the switch on, with a functioning switch, reguardless of load.
Terminal to terminal on the switch will read zero with the switch
turned on, and non-zero with it turned off - the non-zero value
depending on the combination of load impedence and meter
impedence(sensitivity) - regardless if it is a digital or analog
meter, and if the nanalog is a symple d.arsenval movement or a VTVM.
The reeding from LINE to NEUTRAL or GROUND will NOT show your phantom
voltage, and the reading across the open switch is NOT phantom.

As for meter connections, you NEVER connect a voltmeter in series with
a load. You ALWAYS connect it ACROSS the load. The OP conected
his/her meter IN SERIES with the load, so it was acting as an ameter
but reading in volts, which didn't really mean anything (without
knowing the exact sharacteristics of the meter in question)

On Wed, 16 May 2012 08:08:54 -0600, bud--
wrote:

On 5/16/2012 5:48 AM, HeyBub wrote:
wrote:

It is often normal to get strange readings with a digital meter, as
someone said, too much to go into here. Short answer is the wiring
is acting like a capacitor or transformer and the high impedance of
the meter is picking up voltage with a very small current. Almost
any load and the voltage will dissapear.. If the bulb was still in
the circuit, it may be a small ammount of feed through in the CFL.

Short answer is the voltmeter was not being used properly, and the
longer answer is nobody else here caught it.
Nothing to do with inacuracies of digital meters - totally a case of
not knowing how to use a meter to troubleshoot - or knowing how to
interpret the readings when the meter is mis-connected.

The readings are accurate

The readings are NOT accurate. The indicated voltage is a phantom.

Consider your assertion that the meter is "mis-connected:" The meter has two
probes. There are two wires. There are two and only two possible ways to
connect the meter and the wires. Which of the two, according to you, is the
correct way to connect all this stuff? If both of the two possibilities
yield the same result, where is the "mis-connection"?


The OP was measuring across an open switch with no load (no bulb). One
might expect zero volts. What was measured was a "phantom" voltage, as
Hey says, caused by capacitance between switched and neutral wires to
the light and the high impedance of the meter as Ralph said. It is a
rather well know quirk (inaccuracy) of digital meters.


Except the OP had a CFL in the socket when they tested the voltage
across the switch.

The measurement across the switch would be meaningful with an
incandescent bulb installed. Or a low impedance meter would measure zero
volts (which would tell the OP nothing).
Because the meter was, as I said, misconnected for the rquired test.

On Wed, 16 May 2012 08:19:29 -0700 (PDT), TimR
wrote:

I started with the assumption the switch was bad, did the checking
mostly out of curiosity (and of course, when trying to figure out
which breaker controls the circuit and the light is NOT working, it's
handy to have a way to know).

And yes I've had trouble with digital meters and phantom results on no
load circuits, that's why I asked (and why I have a Simpson on the
shelf, but unwinding all those probe wires is a pain, not as bad as
winding them up to get them back in the case though).

But on 120 V circuits normally that meter reads okay or floats a bit.

I left out a couple of things. The fixture had no lamp in it, so that
circuit should be open. The kitchen lights are on the same circuit,
they went out when I got the right breaker (if I'd known that ahead of
time I wouldn't need a meter, technically).

The 80V terminal to terminal on the switch was with the switch off AND
no lamp in the fixture. With switch on, it went to 0 as I'd expect.
It was consistent with several measurements and was the same as wire
to wire with the switch removed (and still no lamp in the fixture).
That surprised me. And then when I went outside and put the same
meter on the fixture and got 120 V I was suprised again.

After work tonight I'll put the analog on it and see.
OK - I read it that you checked the voltage at the socket and found
zero, replaced the bulb and checked the voltage across the switch,
which read 80 with the switch on and off - then you replaced the
switch and got 80 and zero, and the light worked.

If, as you state now, the 80 volts was with the bulb removed,
capacitive coupling was giving you the 80 volts. (which happens not
only with digital meters, but with "sensitive" analogs as well.

You DO understand that you were not using the meter correctly? The
CORRECT measurement is line to neutral - or in absense of an available
neutral connection, line to ground. With a high impedence meter (like
most digitals) you can substitute your damp finger for ground and
usually end up within a couple of volts of accurate due to the high
capacitance of your body coupling to ground (and NO danger of a
shock).

A good switch will read line votage on the line side, both on and
off, and zero volts (or extremely close) on the load side with switch
off and load connected, and line voltage with switch on - load or no
load. I specify load connected on the OFF position because you can
get those "phantom" voltages on a "disconnected" lead - which will
dissapear if the wire is grounded through the load.

On Wed, 16 May 2012 08:31:57 -0700 (PDT), "
wrote:

On May 16, 7:48Â*am, "HeyBub" wrote:
wrote:

It is often normal to get strange readings with a digital meter, as
someone said, too much to go into here. Â*Short answer is the wiring
is acting like a capacitor or transformer and the high impedance of
the meter is picking up voltage with a very small current. Â*Almost
any load and the voltage will dissapear.. Â*If the bulb was still in
the circuit, it may be a small ammount of feed through in the CFL.

Short answer is the voltmeter was not being used properly, and the
longer answer is nobody else here caught it.
Nothing to do with inacuracies of digital meters - totally a case of
not knowing how to use a meter to troubleshoot - Â*or knowing how to
interpret the readings when the meter is mis-connected.

The readings are accurate

The readings are NOT accurate. The indicated voltage is a phantom.

Consider your assertion that the meter is "mis-connected:" The meter has two
probes. There are two wires. There are two and only two possible ways to
connect the meter and the wires. Which of the two, according to you, is the
correct way to connect all this stuff? If both of the two possibilities
yield the same result, where is the "mis-connection"?- Hide quoted text -

- Show quoted text -

I would have tested for 120V using one test lead
on the light side of the switch and the other held
to ground. I'd use ground because that's usually
there and available without taking anything apart.
Or he could have tested from the light side of
the switch to neutral.
Correct.

On Wed, 16 May 2012 11:57:44 -0400, "Ralph Mowery"
wrote:


wrote in message
...
I would have tested for 120V using one test lead
on the light side of the switch and the other held
to ground. I'd use ground because that's usually
there and available without taking anything apart.
Or he could have tested from the light side of
the switch to neutral.

Many times there is no neutral at the light switch or if it is, it is not
broken and easy to get a meter lead on.

I also try not to test to ground as sometimes the ground wire is left out.

In which case you will still have a "capacitive ground" which will
give an (inaccurate but more or less consistent) reading. The test
will still tell you if the switch is working or not. A simple neon
tester will do the same, using your pinkie as ground.

On Wed, 16 May 2012 12:35:14 -0400, Metspitzer
wrote:

On Wed, 16 May 2012 08:19:29 -0700 (PDT), TimR
wrote:

I started with the assumption the switch was bad, did the checking
mostly out of curiosity (and of course, when trying to figure out
which breaker controls the circuit and the light is NOT working, it's
handy to have a way to know).

Test the bad switch with an ohm meter


That works - but you need to turn the power off for that test. The
voltmeter test requires removing the switch plate - and that is all
-unless you can't get your test lead to the terminals without
loosening the switch from the box - but the troubleshooting can all be
done live.

On Wed, 16 May 2012 13:00:35 -0400, "Ralph Mowery"
wrote:


wrote in message
...
Many times there is no neutral at the light switch or if it is, it is not
broken and easy to get a meter lead on.

I also try not to test to ground as sometimes the ground wire is left
out.

Well if you don't like using ground and a neutral is no
good because you have to take off a wire nut, how
would you propose to do the test?

Often in a light switch there is no neutral to have a wire nut to take off.

If there is no neutral or I suspect the ground is not connected, I use what
some may call a 'hot stick'. It is a device about the size of a cigar that
lights up and/or beebs when held next to a wire that has voltage on it.
Cutting the breaker off and on while using the hot stick usually confirms
there is power or no power at the switch. Then with the power off, I check
the switch using the ohms fuction.

I often use a Simpson 260 because I do not like the digital meters for
general testing due to the 'phantom' voltages. Another favorite is a Fluke
T2. I think that is the number. It has about 10 LEDs in it. It will check
from about 6 volts to 600 volts AC/DC and also low resistances. Just hook
up the test leads and it will show if you have power or a short.

I do admitt that I have several differant testers that most home owners do
not normally have or really need.
I also have a Fluke 87 digital meter, but seldom use it for electrical test
due to the 'phantom ' voltages. I work in industry where I have to deal
with anything from low voltage control and instruments to 480 volt 3 phase
circuits. That is the reason for having those plus several other testing
devices.

The simple old neon tester is still the simplest troubleshooter for
domestic wiring - the old solenoid tester to determine what line
voltage you are working with (usually 24 to 600)

On Tue, 15 May 2012 16:21:14 -0700 (PDT), TimR
wrote:

The back porch light stopped working, a new bulb didn't help.

So. I put a meter on the socket. 0 V.

I pulled the switch plate off (just a normal single pole). 80 V
terminal to terminal. Hmmm?

Killed the power, put an ohmeter terminal to terminal, infinite
resistance at both switch positions. Diagnosis bad switch, supported
by the fact that before it died completely, flipping the switch
several times made it work. Besides I've always had a CFL in that one
and I suspect the capacitor shortens the switch life due to arcing.

Okay, a new switch is $1.29, no big loss if wrong. Took the old
switch off, turned the power back on and checked wire to wire just for
grins, still 80 V. Uh oh.

Put the new switch in. Turned power on, checked the socket, 120 V.
Put bulb in, (CFL), lights up fine.

Well, I have a working porch light again, but I'm left with the 80 V
mystery. I don't know any way to get 80 V on a normal residential
power setup. The meter was a digital Radio Shack multimeter. If I'd
had time I'd have checked again with the Simpson analog, digitals
sometimes give funny readings, but I've never seen 80 V. What am I
missing?
I didn't read all of the posts thoroughly, but I didn't see anyone
mention the possibility that he measured 80 *milli*volts rather than
80 volts. If the meter is auto-ranging, that is a distinct
possibility and often missed by those dambling in electrical work. The
display says 80.0 and a tiny little mv is displayed on the side
instead of V.

Pat

wrote:
On Wed, 16 May 2012 08:08:54 -0600, bud--
wrote:

On 5/16/2012 5:48 AM, HeyBub wrote:
wrote:

It is often normal to get strange readings with a digital meter,
as someone said, too much to go into here. Short answer is the
wiring is acting like a capacitor or transformer and the high
impedance of the meter is picking up voltage with a very small
current. Almost any load and the voltage will dissapear.. If
the bulb was still in the circuit, it may be a small ammount of
feed through in the CFL.

Short answer is the voltmeter was not being used properly, and the
longer answer is nobody else here caught it.
Nothing to do with inacuracies of digital meters - totally a case
of not knowing how to use a meter to troubleshoot - or knowing
how to interpret the readings when the meter is mis-connected.

The readings are accurate

The readings are NOT accurate. The indicated voltage is a phantom.

Consider your assertion that the meter is "mis-connected:" The
meter has two probes. There are two wires. There are two and only
two possible ways to connect the meter and the wires. Which of the
two, according to you, is the correct way to connect all this
stuff? If both of the two possibilities yield the same result,
where is the "mis-connection"?


The OP was measuring across an open switch with no load (no bulb).
One might expect zero volts. What was measured was a "phantom"
voltage, as Hey says, caused by capacitance between switched and
neutral wires to the light and the high impedance of the meter as
Ralph said. It is a rather well know quirk (inaccuracy) of digital
meters.


Except the OP had a CFL in the socket when they tested the voltage
across the switch.

The measurement across the switch would be meaningful with an
incandescent bulb installed. Or a low impedance meter would measure
zero volts (which would tell the OP nothing).

Because the meter was, as I said, misconnected for the rquired test.

Again I ask, in a slightly different form, what, in your expert opinion, is
the proper way to connect two probes to two wires?