Identifying cables

[audi321]

I guess it's electronics, so posting under 'stuff' but I have 2 wires (identical) running about 30 meters and I want to be able to identify which one is which from the other end. If they were short, I would simply use my multimeter in continuity mode and touch both ends to see which one beeps.

But given they're so far apart, this isn't an option. So any ideas?

[megaphone]

Short out one end of one cable then use your meter on the other end to ID.

[audi321]

megaphone said:

Short out one end of one cable then use your meter on the other end to ID.

Sorry to be thick, but how do I 'short out a cable'?

[2172cc]

I was a BT engineer for many years and we would do this routinely everyday. We used an ocilator to send a tone down the cable and an amplifier to pick it up at the other end. I'm retired now but still have my kit. You can borrow it if your local to me in Hertfordshire

[2172cc]

audi321 said:

megaphone said:

Short out one end of one cable then use your meter on the other end to ID.

Sorry to be thick, but how do I 'short out a cable'?

Twist to the two bare ends together

[audi321]

Unfortunately not..........I thought this would be easy but if I need things like an oscilloscope then I've not got a hope lol

[megaphone]

2172cc said:

audi321 said:

megaphone said:

Short out one end of one cable then use your meter on the other end to ID.

Sorry to be thick, but how do I 'short out a cable'?

Twist to the two bare ends together

This. Or are these single core wires?

[megaphone]

audi321 said:

Unfortunately not..........I thought this would be easy but if I need things like an oscilloscope then I've not got a hope lol

He is referring top a cable 'toner'. Sends a tone down a cable to ID it.

[audi321]

2172cc said:

audi321 said:

megaphone said:

Short out one end of one cable then use your meter on the other end to ID.

Sorry to be thick, but how do I 'short out a cable'?

Twist to the two bare ends together

Huh? Maybe I've not explained myself properly. I have 2 separate cables running next to each other for 30m. I have bare ends on each. I want to be able to identify which is cable A and which is cable B. They are identical in every way (looks, number of copper strands, etc etc).

How is twisting two ends together at one end going to help me identify which is which when 30m away?

[2172cc]

audi321 said:

Unfortunately not..........I thought this would be easy but if I need things like an oscilloscope then I've not got a hope lol

Not an oscilloscope it's just a signal generator

[shtu]

Two single-core cables, with nothing else connected?

Attach a 9v battery to both at one end, and use your meter at the other end to check the polarity.

[megaphone]

audi321 said:

2172cc said:

audi321 said:

megaphone said:

Short out one end of one cable then use your meter on the other end to ID.

Sorry to be thick, but how do I 'short out a cable'?

Twist to the two bare ends together

Huh? Maybe I've not explained myself properly. I have 2 separate cables running next to each other for 30m. I have bare ends on each. I want to be able to identify which is cable A and which is cable B. They are identical in every way (looks, number of copper strands, etc etc).

How is twisting two ends together at one end going to help me identify which is which when 30m away?

You haven't explained yourself . Are these single core cables? Or two core etc? What type of cable? What's it for?

[audi321]

megaphone said:

You haven't explained yourself . Are these single core cables? Or two core etc? What type of cable? What's it for?

I don't know how to describe them, but they're each a black cable with multiple strands of copper wire inside them. They're not very thick, maybe 5mm in diameter.

[audi321]

shtu said:

Two single-core cables, with nothing else connected?

Attach a 9v battery to both at one end, and use your meter at the other end to check the polarity.

Perfect, I think that's the answer. The multimeter will give me a negative result one way round! I just need to test a short piece of cable to work out which way is which result. Thank you

[megaphone]

audi321 said:

megaphone said:

You haven't explained yourself . Are these single core cables? Or two core etc? What type of cable? What's it for?

I don't know how to describe them, but they're each a black cable with multiple strands of copper wire inside them. They're not very thick, maybe 5mm in diameter.

Maybe post a picture, otherwise we will get nowhere. Did you do home economics by mistake at school?

[maccboy]

shtu said:

Two single-core cables, with nothing else connected?

Attach a 9v battery to both at one end, and use your meter at the other end to check the polarity.

Surely this?

[audi321]

megaphone said:

audi321 said:

megaphone said:

You haven't explained yourself . Are these single core cables? Or two core etc? What type of cable? What's it for?

I don't know how to describe them, but they're each a black cable with multiple strands of copper wire inside them. They're not very thick, maybe 5mm in diameter.

Maybe post a picture, otherwise we will get nowhere. Did you do home economics by mistake at school?

Maybe you did if you need pictures each time. I don't think I was unclear with what I asked. At least 2 other people gave me a reasonable answer.

[shtu]

If only there was some way of creating a visual description.

As above, if they are two single core (incl. multi-strand) cables, use a battery and meter. It's not as spiffy as a tone generator, but it will work.

If you've got mutli-core cables like CAT5, you can do something similar using two cores of each.

[OldGermanHeaps]

If one of them is open circuit that test wont work, but you can use the houses earth as a return path for testing individual cores, connect one to a pattress screw then at the other end test for continuity between a pattress screw in that room and the cable.

[audi321]

OldGermanHeaps said:

If one of them is open circuit that test wont work, but you can use the houses earth as a return path for testing individual cores, connect one to a pattress screw then at the other end test for continuity between a pattress screw in that room and the cable.

Cheers, but they're literally 2 long cables, no open circuits or any connections. The 9v battery is the perfect answer I think.