Good info about multimeters and safety

[Barry Adair]

for those of us who use multimeters (we all should) ...
I've been reading a multi-page article in my IAEI News about multimeter accidents, injuries, and deaths from multimeter misuse (or using the wrong multimeter in the wrong location).

This is the gist of the warnings: If the multimeter you are holding fails for any reason (could be operator caused, could be age, deterioration, moisture, etc.) there is a good probability that the multimeter failure acts as a short across whatever you were measuring - with one lead connected to one side, the other lead connected to the other side, the meter fail and shorts out ... you might as well be holding a piece of copper wire between the two things you were measuring.

That short can lead to an arc or arc flash, burning your hands, clothes, etc., not trying to be scary of anything, but there have been many, many, many cases of such happening.

The meter you use needs to have the correct CAT I, CAT II, CAT III, or CAT IV rating for the area (not just what you are measuring, but what is around that area and what is supplying that area).

Here is some good information, descriptive drawings, and examples of the different CAT areas in which different CAT rating meters should be used.

http://www-group.slac.stanford.edu/e...ter_Safety.pdf

and

Anatomy of a high quality meter

Most of what we would normally check would be CAT II or CAT III, however, many of us stray into CAT IV (basically when you use your meter outdoors to measure the things we might measure)
__________________
Jerry Peck
Construction / Litigation Consultant www.ConstructionLitigationConsultants.com
Ormond Beach, Florida

[Michael Larson]

I disagree with Jerry's comment that we all should and can't imagine why he said that.

The info is very good but the vast majority of HIs would have little use for a multimeter.

Let's hear it if you feel differently.

[Stephen W. Stanczyk]

About the only time I take mine out is to check the dryer or oven receptacle in a vacant house.

[Michael Larson]

Originally Posted by sstanczyk

About the only time I take mine out is to check the dryer or oven receptacle in a vacant house.

And even then a Wiggy style device is a much better choice.

[George P. Wells]

Originally Posted by mlarson

And even then a Wiggy style device is a much better choice.

I know, I sound like a broken record but the Wiggy is the best choice for just about everything a home inspector does.

The problem with most modern multimeters is the high input impedance. Once meters exceed 100KΩ/V, the trouble starts. Those of you who have participated in the free electrical course that we (InterNACHI, CMI, BestInspectors.Net) do know that I feel very strongly about this. Proper use of an ultra-high impedance meter requires a very good understanding of the behavior of electricity.

A Wiggy has a very low imput impedance which makes it ideal for a wide variety of uses by people. It is an especially good choice for people who have only a basic understanding of electricity.

[Michael Larson]

George, I've had a Wiggy for over 30 years.

I have seen far to many guys(even ones that should know better) get confused by what a digital meter or a neon tester is apparently telling them.

Same problem with trouble shooting automotive or trailer wiring.
Use a test lamp. It won't fool you.

[Paul W. Abernathy]

well...let me just say this....I am not trading my FLUKE in anytime soon....

[gmortensen]

Originally Posted by pabernathy

well...let me just say this....I am not trading my FLUKE in anytime soon....

When I was an apprentice I used an RCC, because it was cheap. Then it blew up in my face. I've used fluke ever since. Though not just anyone should be sticking the leads anyplace they feel like it.

[Ralph Brady]

I hate it when I test my car battery voltage on the current setting!

The lead just falls off the probe. Most lead wires are such low guage, they act as a fuse.