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Have you ever had to repair a cable and you know the wire is probably broken at one of the plugs but you cant tell which end?

If you have a multimeter that measures capacitance you can really shorten your work. Measure capacitance of the bad wire to adjacent wires. If its near zero compared to the reading from the other end you're on the bad end. I was repairing some patch cables this weekend at work and discovered none of my co-workers knew this trick.

I discovered this trick back in the 70s while I was in the USAF. I had just built a linear scale capacitance meter and was playing with it measuring everything in site when I noticed a test cable had 0 capacitance center pin to shield on one end and the light bulb in my head went ON and I have been testing cables this way ever since then.

Anyway, I figured since my co-workers didnt know about this technique maybe a lot of other people didnt either so I am posting it around.

Jimmie Fender

Reply to
Jimmie D
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Maybe some of the real techs in here knew that, but I didn't. Thanks! What kind of capacitance range are we talking about? I've got a non-auto-ranging capacitance meter with quite a few ranges...

Reply to
Smitty Two

Dont feel bad, we have some REAL techs at work with 30 years experience that didnt think about doing it.

Hmmm, never really noticed. Mine is auto ranging. Suffice it to say you will notice after playing with it a little.. When I find an open there is little difference if any than when Im not touching the cable.

Jimmie

Reply to
Jimmie D

I've used this method especially with CAT5 cable meters that can actually tell you how for down the line the break is.

Reply to
Meat Plow

In message , Michael A. Terrell writes

But 'slightly' more expensive!

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Ian
Reply to
Ian Jackson

Yeah, Is that anything like the incandescent light bulb trick being used in place of a fuse while looking for that short? :)

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Reply to
Jamie

broken

Better for who?

Reply to
Meat Plow

I've never had any problems with the meter we used. Besides I never pulled wire, just verified a problem existed and called the sub who did the rest. And I'm not so sure the meter we used wasn't a TDR as I no longer work for that company. I know it was expensive, a couple grand so it may have been a TDR.

Reply to
Meat Plow

Don't forget to replace the light bulb in your head with a Compact Fluorescent Light (CFL).

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Steven L.
Email:  sdlitvin@earthlinkNOSPAM.net
Remove the NOSPAM before replying to me.
Reply to
Steven L.

I got a rather nice little tester off Ebay for a few quid which broadcasts a an RF signal down the cable which you pick up with a directional receiver. Mainly to identify concealed cable runs under floors or bunched together etc, but can also be used to find breaks. A useful tool that a few years ago would have been very expensive indeed.

--
*A hangover is the wrath of grapes.  

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.
Reply to
Dave Plowman (News)

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