meter gone crazy

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Kingpen

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I have got a Fluke 87 III multimeter. Hunting for grounds in a lighting circuit when the lights have ballast. When I check between the power wire going to the light and a good ground, for continuity my meter goes crazy. It bounces from 10 to 80 ohms with a negative sign in front of it. Can any one tell me what my meter is telling me.
 
Your meter is probably seeing some small voltage that's interfering with its resistance readings. Does the minus sign go away if you reverse the test leads?
 
Is this part of a multiwire branch circuit? The reason I ask is because if you have some other circuit "sharing" that neutral to the ballast, and you connect your meter from the ballast black wire to ground, you have completed a circuit. Comes "in" the ballast neutral from other circuit sharing that neutral, through ballast, though the meter, and to ground. A parallel neutral path. Just a guess.

When I get these wacky readings, I generally switch to volts to figure out if I'm really trying to ohm out in the presence of voltage. I should add that a couple of the meggers that I use for this purpose will automatically display the measured voltage on the screen if I'm accidentally trying to megger an energized circuit.
 
meter gone crazy

Put a scope on it. Digital meters make a lot of assumptions about how to interpret what they're looking at.

I hope you didn't fry your meter.
 
langjahr@comcast.net said:
Put a scope on it. Digital meters make a lot of assumptions about how to interpret what they're looking at.

I hope you didn't fry your meter.
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:grin: :grin:

Sure, every guy troubleshooting some lighting has a scope handy. A modern Fluke is pretty hard to burn up if you used it within its voltage range. They just holler at you if you're doing something it doesn't like.
 
meter gone crazy

Regarding carrying a scope around, I think on this job "the box containing inconvenience" has already been opened.

I may be able to remember Teresa Brewer, but when I get weird readings on stuff that contains microprocessors, I try to go back to having as little machinery (and software) as possible between me and the electrons. Except for scopes; nothing can hide from them.

Of course, if this gentleman could find some HandyGeezer who was educated way beyond his intelligence, and who enjoys solving knotty problems, and to whom he could e-mail a schematic, he might be in luck. . .but right at the moment I can't think of anyone!
:)
 
Ouch

Ouch

ONLY meters I have seen that say OUCH is crap-on blue point when measuring resistance of open circuit :rolleyes:


e57 said:
It's saying "OUCH - OUCH - STOPPIT DUDE - STOP!"

OTHERWISE ALL OF THE ABOVE....
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meter gone crazy

I'm sorry to report that my last post on this subject was mostly nonsense-please disregard!
 
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