How can a trace a terminated, hidden wire? 2

[tonylazyz]

Is there any sort of fox-and-hound type wire tracing device I can use to find the other end of a 2-core, terminated, potential-free cable?

I have a series of sensors that join at a junction box somewhere (this is on a small ship) but I don't know where the junction box is and I need to find it.

Can anyone recommend a reliable, high quality product?

Thanks
Tony

 

[waross]

A tone tracer from the telecommunication industry may help. We had an open end of a cable somewhere in an industrial plant. A four man crew searched for about three shifts. Then one man found the cable end in 20 minutes with a tone tester.
Tip. You can follow an unshielded cable. If you can isolate the shield from ground, you can put the signal on the shield and follow the cable. Otherwise you must get close to the open end to get a tone.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[itsmoked]

I'm surprised you can't puzzle out which way the sensor cables are going, make some educated guesses, open some boxes and find them. It's a ship after all, not a bunch of sheet-rocked catacombs. Isn't everything in conduit tacked to the walls or just clipped directly to the walls?


I had to hunt down a broken PA system cable for a huge tannery once. I finally found the cable guitar-string-tight descending at a 45 degree angle into the bottom of a 30 foot high pile of leather scraps in 32 gallon plastic garbage bags. The cable symmetrically ascended out the other side of the pile. It was pulled in two at the center.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[catserveng]

I use a Fluke Networks Pro3000 pretty regularly for that kind of work, in it's price range I have the best results with it, and it's pretty readily available, like Home Depot, Graingers, and sometimes at Lowe's, about $100 USD, also come up on ebay pretty often.

Of course if you don't so it much and don't have the tooling, depending on where you are it may just be better to have a contractor who does a lot of network wiring spend an hour and do it for you, then you can see what he uses and how he did it.

Hope that helps, Mike L.

 

[Comcokid]

Another instrument is a TDR (time domain reflectometer) These are frequently used to check telephone lines and even to locate problems in wires in large aircraft. Also commonly used by security agencies to check if telephone wires have been tapped with a bug.

I had a friend who bought a used RV that had an AC circuit that was shorted. Not having access to a TDR, he adapted a TDR type fluid-level sensor to get the distance to the short and locate a nail used to hang a cabinet when the RV was made that was driven into the AC cable.

Actually, some large ships use TDR fluid-level sensors to check the level of bunker fuel and water in tanks.

 

[tonylazyz]

Thanks for the answers everyone.

itsmoked - this small ship (200') is a private yacht so all the cable runs are in deckheads and behind walls that are very high quality woodwork, marble, etc. Stuff that isn't designed to be taken apart easily.

catserveng - the fluke sounds like a useful device to have on board since we have this problem often on yachts.

 

[itsmoked]

I was picturing a tramp freighter or a tin can.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[MacGyverS2000]

Mike,

Here ya go... Fluke Networks Pro3000

http://www.buy.com/prod/fluke-netwo...nerator-network-testing-device/202279383.html

A mere $38.24 w/free shipping

Dan - Owner

http://www.Hi-TecDesigns.com

 

[MacGyverS2000]

Sorry, that was just the tone generator... here's the generator and probe for $67.24 w/ free shipping:

http://www.buy.com/prod/fluke-networks-pro3000-series-26000900-analog-tone-and-probe/203264358.html

Dan - Owner

http://www.Hi-TecDesigns.com

 

[Skogsgurra]

If you need to find a break in a wire, you can use a very simple TDR that was described a long time ago here:

http://www.gke.org/pub/files/Cable Radar Electronic Design.pdf

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[tonylazyz]

Actually, I don't need to find an open. The wire is terminated, but I don't know where. That is what I need to find. I have a cheap tone generator on board, but I can only get it to work on an open circuit. Am I missing something really simple?

 

[BrianG]

Are you still trying to find where the route of the wire behind the panelling or just where it is terminated (unexpectedly)? Terminated presumably means with a load of some sort, not a short circuit? You could still use the TDR technique suggested by Skogs. If you use a different source impedance to that of the cable and its termination you will get a (small) reflection with a time delay: this should allow you to estimate the position.

 

[Skogsgurra]

Yes, as BrianG says.

If you look at picture 2 in my link above, you will see a negative-going echo at 280 ns. That is caused by a shunt termination and can be readily seen. The cable's end is not terminated and causes the big echo at 1100 ns.

A tone generator will not work well if you do not have a sensitive search coil plus amplifier to pick the field up.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[MikeHalloran]

If the wires are in anything resembling a conduit, even a jacketed cable having a lumen, you could pump cigar smoke into the accessible end and observe where the smoke/smell comes out.

Or, you could overdrive the loop until the terminator or the wire overheats, seek the smoke/smell, and then repair the collateral damage. Yeah, I hate that one too.

Or, you could open everything that opens, and if you still don't find the j/b, call the yachtbuilder and ask to speak with someone who installed that system on that boat.

Yacht plans usually don't go into the level of detail that you need, even for the few that are really mass produced. But you might be able to deduce some clues from this observation: Whichever crew gets to the boat first, gets to put their stuff where they want it. Subsequent crews have to work around whatever was already done when they arrived. So many of the junction boxes will be where the electricians thought the carpenters would put the access panels, before any of the panels or substrate were installed.





Mike Halloran
Pembroke Pines, FL, USA

 

[tonylazyz]

Mike - no truer words have ever been spoken! I like the cook-it-till-it-smokes procedure, haven't tried that one yet. We just spent 3 guys X 3 hours looking for an amp in a cabin deckhead only to find the cables run down inside a wall and the amp was on the floor of the bathroom, under the sink and behind a loose marble tile!!! And this is on an Amels! You'd think the Dutch would do better than that.

 

[WoodrowJWeen]

Have you considered using a cheap AM "transistor" radio as a detector and a small chattering relay (wire the coil through the NC contact to a 9V battery) as an RF generator. I've done this several times with good results. Connect the "transmitter" to the wire in question, tune the radio to an unused part of the band, move it around and listen for the noise. Not real elegant but works in a pinch.

 

[DuncanM]

Whichever crew gets to the boat first, gets to put their stuff where they want it. Subsequent crews have to work around whatever was already done when they arrived.

The good old shipyard olympics. Bane of many ship's engineers life!



Tony - I've had luck trawling through old build/refit photos to locate things before.
Lighting transformers/controllers were always an issue on one of the yachts I was on, found them in the weirdest of places.