Simple Way to Check Wire Continuity

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Please note that this subject may interest some members only. And I am not sure if what I present here is new or not.

 

Lately, I had to check the continuity of each wire of a long 8-wire cable which connects two rooms in different floors.

It happens that I had a small signal neon bulb (connected in series with a high value resistor). It is usually used to monitor the AC mains voltage.

 

The test:

On one side, all wire ends of the cable are grounded. On the other side, one terminal of the signal neon bulb is connected to mains phase without forgetting to isolate it well to avoid any risk. As you already guessed, the bulb will turn on every time its other terminal touches a healthy wire... or a finger smiley

 

For instance, this simple technique is well known, since very long, to test the mains phase terminal by using a screwdriver which has a neon bulb and a resistor inside its transparent body.

 

Kerim

Last Edited: Wed. Feb 27, 2019 - 11:39 PM
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This is also not a very safe method of testing wires.........

 

The other option is to ground the far side as you mention, and use your ohmmeter.  Place one probe on the wire to test, the other on building ground.  Read a couple of ohms its good.

 

In both tests though, Kerim's and mine this does not tell you if the cable/wire is shorted to building ground due to being pinched somewhere along its route.

 

 

JIm

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Hi Jim,

 

Thank you for the practical remarks on which I agree with you.

 

Actually and since our mains voltage is 220Vac, I was able to connect another signal bulb in series with ground on the other side of the cable.

 

Since most members here live with 110Vac and to let the test be very simple on my first post, I simplified it concerning the other side of the cable. The breakdown voltage of the small neon bulb is about 70V so my actual test (using two in series) doesn't work with 110Vac. On the other hand, I am sure there are many other alternatives that depends on the situation.

 

After all, it was just an idea, I liked to share, though it could be useful to some people only around the world (1st line on OP). And I agree with you that it is surely not for newcomers in the world of electricity.

 

Kerim

 

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I needed to check a bunch of 8 conductor cables. I put 4 resistors between pairs. Each pair would have a known resistance. From each wire to the other 6 there would be an open circuit. I used 47, 220, 470, and 1k. I went from one room to the next, plugged in the resistor thing then back in the wiring closet I could verify 1) the correct room / cable identification 2) continuity for each conductor and 3) absence of shorts.

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Great idea!

Jim

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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bobfrench wrote:
I needed to check a bunch of 8 conductor cables. I put 4 resistors between pairs. Each pair would have a known resistance. From each wire to the other 6 there would be an open circuit. I used 47, 220, 470, and 1k. I went from one room to the next, plugged in the resistor thing then back in the wiring closet I could verify 1) the correct room / cable identification 2) continuity for each conductor and 3) absence of shorts.

 

I used to measure the length of "Belden 9184" cables that way. Had a "tester" plug with two different resistors. At the other end the blue/pink pair should be the low resistor plus some ohms per foot, and the other should be the high resistor plus some ohms per foot.

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Great alternative ideas, thank you.

 

I wonder which method is applied for under-sea cables wink

 

Kerim

 

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KerimF wrote:
I wonder which method is applied for under-sea cables

don't you apply a h/v DC to the cable and just look for the bubbles?   wink

 

Jim

 

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