Voltage

[rm]

Hopefully someone has seen this issue before and can help me understand what is going on here. We're working on a renovation project and some of the receptacles still show voltages of between 18V to 30V eventhough the breaker has been turned to off on that particular branch circuit. When the main circuit breker of the panel is turned off the voltage disappears. Has anyone seen this before? Thanks.

 

[iwire]

Re: Voltage

STOP USING DIGITAL METERS !

Sorry for 'yelling' but this is a frequent occurrence.

There is no need to use a digital meter to find out of the power is on or off use a basic Wiggy or some other solenoid tester. When you use a sensitive meter things like this happen, it is called phantom voltage by some.

From NEMA

Due to the high impedance of measuring instruments, a voltage reading may be detected on open conductors where there is no hard electrical connection to a voltage source. Conductors that are installed in close proximity to one another, and are capacitively coupled to each other, can cause this a.c. voltage reading. Such a reading could be 2 or 3 volts, or it may be as high as the voltage on the adjacent conductors. This is what is referred to as a "phantom" voltage.

You can see the entire text at this link.
NEMA BULLETIN 88

 

[physis]

Re: Voltage

Somebody once mentioned that if you put a resister between the leads that will shunt the teeny tiny current responsible for those ignorable voltages. Between 100 k and 1 m should work fine.

 

[rattus]

Re: Voltage

It is a real voltage alright, but it will disappear like a phantom when you use a meter with less sensitivity like my 50 year old Heathkit VOM--5Kohms/volt.

 

[charlie]

Re: Voltage

Heathkit? If you built it, you are as old as dirt.

 

[iwire]

Re: Voltage

Originally posted by charlie:
Heathkit? If you built it, you are as old as dirt.

Here you go guys, sorry I could not find the Tachometer.

Heathkit Virtual Museum

 

[physis]

Re: Voltage

You don't have to be that old Charlie. Like me, I'm 32 and I used to go through the Heathkit catalog all the time.

 

[electricman2]

Re: Voltage

I used to build Heathkits too so I must be older than dirt. I dont know how to post pics but Here is a link to a picture of a Heathkit indoor-outdoor thermometer sitting across the room from my computer. Built in 1979, still works.

Edited to add smaller picture. Charlie

[ December 05, 2004, 09:32 AM: Message edited by: charlie ]

 

[physis]

Re: Voltage

It's amazing that not long ago that stuff was state of the art. Those big ol' 7 segments and their 7 500 ohm resisters because they didn't have arrays yet.

 

[don_resqcapt19]

Re: Voltage

electricman2,
I built that temperature display and the matching clock in about 73. The temperature unit no longer works, but I am still using the alarm clock.
Don

 

[rm]

Re: Voltage

Thanks guys for all the replies. I think I'll use a resistor to determine if in fact it was the 'Phantom Voltage' issue. Thanks again

 

[rbalex]

Re: Voltage

I guess I antedate dirt. I still have a working Heathkit oscilloscope and VOM, that I first assembled in '68.

 

[tom baker]

Re: Voltage

We still use some heathkit power supplies at work. The digitial meter has spoiled us. take the heathkit meter, put it on Ohms and test voltage at a receptacle. You will then have a non working meter. Most of the digitals will be ok with this misuse. Simpson used to make the 260 analog meter, very popular, and then came out with the DVM style but in the same case!

 

[physis]

Re: Voltage

Tom, I've been finding in the last five years that a lot of digitals don't withstand that kind of use any more. I started out eons ago with beckman, this thing was nearly indestructable. In the last couple of years I've played taps for at least a few digitals attempting to measure resistance in the presence of 120vac in the same way I always have since the beckman. I'm now considering building a filter so I can do what I used to be able to do without having to be concerned. I don't use Fluke. My guess is those can handle it.

 

[hurk27]

Re: Voltage

By Bob: quote:
--------------------------------------------------------------------------------
Originally posted by Charlie:
Heathkit? If you built it, you are as old as dirt. I built a Heathkit electronic ignition and tachometer for my '55 Chevy.
--------------------------------------------------------------------------------

Here you go guys, sorry I could not find the Tachometer.

Heathkit Virtual Museum

In a Museum?
Every thing from a color dot generator, cross hatch generator, vacuum tube VOM, signal generator, sevral power supplys, and even a HF band transceiver.

 

[charlie]

Re: Voltage

Wayne, you are not that old, I have put an eyeball on you and broken bread with you.

 

[hurk27]

Re: Voltage

And allied went out when? 1970, 1972? I think. Heath was around a few more years. I even had a field trip from school to the Heath plant up there in Benton Harbor, Mi. I was like a kid in a candy store

[ December 06, 2004, 11:34 PM: Message edited by: hurk27 ]

 

[hurk27]

Re: Voltage

P.S. I'll most likely see ya again in February in Lafayette.

 

[charlie]

Re: Voltage

Yep, they got me on the program.

 

[physis]

Re: Voltage

Ya gonna be a speaker or somethin like that Charlie?