Why not? You've got the floating wire lying right next to a 120v line for 50
feet or whatever the distance to the panel is. The voltage will be some large
percentage of 120v. The current will be tiny (which is why DMM's show the
voltage and analog meters don't). -- Doug
Because it is the CORRECT "low impedance" multimeter that can
accurately measure line voltage circuits...
The cost is irrelevant, as long as the multimeter is the correct type,
you will be able to properly measure for the actual presence or
absence of hazardous line voltages...
Not only is cost irrelevant, but it's also a function of the person
using the meter understanding some basic electricity and knowing how
to interpret the readings. I've exclusively used digital VOMs for
decades and never had any confusion. You could also make up an extra
set of test leads with a 50K ohm resistor across them to reduce the
On Sat, 03 Apr 2010 00:17:08 -0800, David Nebenzahl
If the "long runs" were live, there is no reason the readings
would not be accurate. However, a long run with a "dead" circuit
paralleling a live one MAY read a voltage that would lead you
to believe the circuit was connected and had a problem.
If, in the OP's situation, for instance, the ground conductor
actually DID exist, but was not connected to the panel ground,
it is possible a "sensitive" or high impedence digital (or even
VTVM) meter could indicate a voltage between the ground and either
On Fri, 02 Apr 2010 15:37:24 -0800, David Nebenzahl
Depends a lot on the meter.
With a Fluke or Amprobe meter, not very likely to have a problem, but
with a $9.99 (on sale for $4.99) Harbour Fright special and many other
cheap chinese DMMs it's almost a given.
There have been several (correct) attempts at an explanation. As I read your
experiment, you tried on a correctly wired circuit and got correct readings.
Just what you would expect.
Now, go unhook your ground wire at the panel. The hot line will induce a
voltage in that wire that can be read by a high impedance meter as difference in
voltage between ground and neutral. Is that plausible?
It is just as easy (maybe more so) for the Fluke or other high dollar meter
to read the 'induced' voltage. I use the Fluke meters almost every day at
work and have one at home. Most of the time if I want to get serious with
the power wiring I will get my trusty Simpson 260. When dealing with some
480 volt 3 phase circuits running in conduit, you can pick up lots of odd
voltages that are not really there. For example one circuit would read
around 100 volts on the Fluke , light up a neon bulb tester, shock the fool
out of you, and read about 30 volts on the Simpson. This is with the wires
disconnected at the breaker.
It is not so much the meter, but the person that is using it. YOu have to
know when the meter is 'lying' to you.
Many people can not do that. Especially the people that seldom use a meter.
Sometimes they are. I have never used the Klein tester but can see where
it may be a much beter circuit tester than some meters. Only problem is
that it is a $ 50 or so tool where the meters can be bought for $ 5 to $ 20
and be used for more things. A good old low power light bulb is very useful
to run some checks with around the house.
For quick checks where I work I have a Fluke tester that is sort of like
that. You just hook it up with the two test leads. If it is AC then
anything from 24 to about 600 volts will light up some leds. It is DC then
other lights will glow from about 12 volts up. And if there is a very low
value resistance, another light will glow. Comes in handy for quick test
when I may be working on some of the computer controlled equipment and may
need to know if I have a relay contacts closed, or 24 volts , 120 volts or
480 volts active.
One thing I did not mention is that on a Simpson 260 and probably others
like it is that if you suspect a phantom voltage you can move from one range
to another and the meter will stay in about the same place on the scale. If
the voltage is a solid voltage then the meter will go up or down a good bit
to match the voltage with the scale on the meter.
One advantage is a Wiggy is pretty indestructible, as from drops,
compared to a meter. I tend to use a neon test light for things like
receptacles, partly because you can tell what wire is hot and it takes
no space in my pocket.
Particularly after reading about arc-flash and 'sudden reconfiguration
of the physical parts of a meter syndrome' I am more careful what I use.
Measuring at a receptacle is not so bad, but I want something good if I
am in a service panel, and something real good at high energy locations
- 480V or high amps. There is a category rating for meters - Fluke (and
others) use it.
Yea - simple but effective.
Ran across that once and it was one of more bizarre measurements I have
Get an analog meter to make a real reading. If you know the breaker
which controls the outlet turn the power off and measure between ground
and each lead. I bet neither one shows continuity meaning there is
broken ground wire. Another way to look at is to connect a light bulb
between either lead and ground. If the voltage is not phantom bulb will
glow at half brightness or so.
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