Finding a break in a cable

Sinbad

Sinbad

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Right, probably not the right forum, but I figured there is probably a gadget to do this, so it's close enough :p

Got an 8 core cable running from my burglar alarm system to a remote panel in a cottage. Getting intermittent faults reported, so one of the wires is obviously damaged.
How... how... how... do I find this break?! :/
Any ideas greatly appreciated.
 
For any cable longer than 2 mts, the easiest will be to replace the cable.

Either Electrical, Network, Telephone, etc...
 
webtailor said:
For any cable longer than 2 mts, the easiest will be to replace the cable.

Either Electrical, Network, Telephone, etc...
Click to expand...

Yeah...easiest?
Not so much. It's about a 50m run. In and out of ceilings, conduits, between two buildings, etc... If the break is accessible, cut, splice, tape, done :p
 
Sinbad said:
Right, probably not the right forum, but I figured there is probably a gadget to do this, so it's close enough :p

Got an 8 core cable running from my burglar alarm system to a remote panel in a cottage. Getting intermittent faults reported, so one of the wires is obviously damaged.
How... how... how... do I find this break?! :/
Any ideas greatly appreciated.
Click to expand...

One of them things telkom tekkies use to trace a cable?
 
AstroTurf said:
One of them things telkom tekkies use to trace a cable?
Click to expand...

I had that thought as well. Think I can report a fault with my line, then tie the telkom techie up while I use his tone probe? :D
 
what you need to do is securely tape another 8 core cable to it at one end. then from the other end, pull the old cable. once you have then entire old cable out, you should have an entirely new cable in. If you get this far, it will be easy to find where the cable is damaged. you can then fix it and use it in another project.
 
ElecEng said:
what you need to do is securely tape another 8 core cable to it at one end. then from the other end, pull the old cable. once you have then entire old cable out, you should have an entirely new cable in. If you get this far, it will be easy to find where the cable is damaged. you can then fix it and use it in another project.
Click to expand...

Eish.

Was really hoping to avoid this :/


Oh well.
 
Replacing is the best, finding a cable break is time consuming and if you have an issue in one spot others are likely to follow.
 
Beachless said:
Replacing is the best, finding a cable break is time consuming and if you have an issue in one spot others are likely to follow.
Click to expand...

OK. Will go buy some new cable - and while I'm about it, renew another cable that I KNOW is farked.


/fun plans for the weekend


Thanks guys
 
On High Voltage cables we use a "Thumper" to locate faults, but on your cable the thumper will just cause more damadge.
Do you need to use all 8 cores?
Another solution is a multiplexer, so now you use your old cable as comms, only 2 cores required, for the multiplexers. Unfortunately this will also be more expencive than just installing a new cable.
 
wetkit said:
On High Voltage cables we use a "Thumper" to locate faults, but on your cable the thumper will just cause more damadge.
Do you need to use all 8 cores?
Another solution is a multiplexer, so now you use your old cable as comms, only 2 cores required, for the multiplexers. Unfortunately this will also be more expencive than just installing a new cable.
Click to expand...

It's an internal DSC alarm connection, so I actually have no cooking clue what the wires are actually used for. I imagine 2 cores per zone, plus power plus ground plus some kind of control? Makes 7...
 
Cables dont just break .
Some thing has to make it break , cable getting chafed or some place it has been damaged or where there is movement in the cable.
On the connections or a bad connection.
 
FNfal said:
Cables dont just break .
Some thing has to make it break , cable getting chafed or some place it has been damaged or where there is movement in the cable.
On the connections or a bad connection.
Click to expand...

I know. There's a couple of places where this could have happened, was hoping to be able to "detect" the break without stripping the cable at every wear point.
 
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.
 
Sinbad said:
I know. There's a couple of places where this could have happened, was hoping to be able to "detect" the break without stripping the cable at every wear point.
Click to expand...
If you have a spare pair in the cable swap it out with the spare pair until the fault goes away .
Or watch for the fault while some one moves the cable at the suspect points .
 
You can measure the capacitance of each pair. The problem pair will have readings that are different from the rest. The fault will be proportional. A network patch cord tester will also isolate the faulty pair. A get a TDR, it determines distance to the fault by measuring time for the reflected signal.
 
Last edited:
I think what you need is a tone and probe kit. It is less than R1000 and works on RJ11,RJ45, powa cables etc.

Not sure too lazy 2 read.
 
Sinbad said:
Right, probably not the right forum, but I figured there is probably a gadget to do this, so it's close enough :p

Got an 8 core cable running from my burglar alarm system to a remote panel in a cottage. Getting intermittent faults reported, so one of the wires is obviously damaged.
How... how... how... do I find this break?! :/
Any ideas greatly appreciated.
Click to expand...

Here you go. A snip at $1 000 000. Might be cheaper to replace the cable. Remember, your time is worthless.
 
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