Finding a break in a cable

markface said:
There's no way to find the section thats broken, but you can check that there is continuity in the wires at least.

I presume all the wires are colour coded and you can disconnect the two ends. Then you could set up a battery (or some sort of DC source, please make it decent, not a penlight battery, a car battery would work though) on the one end, and measure what you get on the other. On the battery side, pick a single wire as the ground or negative connection, then connect all the rest of the 7 wires to the positive battery terminal. Go to the other end and measure each individual wire for a voltage difference, between the wire and your chosen ground wire. The one that measures nothing is broken. Be aware that you will measure a voltage less than your battery.

However, if this does work and you find a problem, you'll still need to run a new cable, unless you can utilise a different wire in the 8core. However if its all good, then you probably have a fault somewhere else.
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And if the cable has failed in such a way that you short circuit your battery? Better have some current limiting circuitry before the cable unless you want to replace your car battery.
 
ElecEng said:
And if the cable has failed in such a way that you short circuit your battery? Better have some current limiting circuitry before the cable unless you want to replace your car battery.
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Haha, true that. Although I'm sure the wire would just melt away before a decent battery source like a car battery died. I've seen jumper cables melt away from people getting that wrong, so an alarm cable would be no match.
 
Just cycle the wires with 220v from the mains, if you hear a loud bang then check for a black spot on the cable. Profit!



Please do not try this at home
 
Pour electrons into each of the 8 cables until they're full. Then empty each separately, and measure the volume of electrons. The cable with the break will have the smallest volume of electrons, and the proportion of that volume compared to one of the other ones will tell you what the proportion of the distance of cable is unbroken.
 
Claymore said:
Pour electrons into each of the 8 cables until they're full. Then empty each separately, and measure the volume of electrons. The cable with the break will have the smallest volume of electrons, and the proportion of that volume compared to one of the other ones will tell you what the proportion of the distance of cable is unbroken.
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not 100% true what if there is 2 cables touching each other inside where the break is?
 
Johnatan56 said:
I think you have three zeros too many.
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Does it matter? R12 000 (or R24 000 from the local agents, no doubt) isn't really an option for a once off. Although, after reading Yotch's links, it's not exactly overpriced. TDR + oscilloscope chip + firmware + other R&D + P&G. Yeah, I see where $1100 comes from.
 
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