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Cable fault locator for underground PSTN cables

Discussion in 'General Electronics Discussion' started by efarook, Jun 16, 2010.

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  1. efarook

    efarook

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    Jun 16, 2010
    Hello everybody,

    I want to build a cable fault locator for my own use. I know there are some ready made stuffs out there in the market, but I want to build my own version.

    This fault locator will be able to monitor and detect open and short cable faults. This is simple, I will be able to design a circuit for this.

    But what I could not get after a long search on the net is that how to locate the fault. I read about TDR (Time Domain Reflectometry) but this is not so handy for my field use.

    Are there any other simpler techniques to find the location of the fault?

    Thanks in advance.
     
  2. davenn

    davenn Moderator

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    Sep 5, 2009

    In a former life I worked for a major telecom company. In the days before TDR's we used to use bridge meggers. they incorporated a wheatstone bridge where the telephone cable pair formed one part of the bridge. With that we could determine, with a small amount of maths, distance to the various types of faults, earth, open cct, short cct

    try googling wheatstone bridge meggers.
    gosh it was only a few months ago I saw one for sale at an amateur radio convention.
    I almost bought it for old time sake :)

    cheers
    Dave
    VK2TDN
     
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    The other method I've seen is where a signal is sent down the cable and the reflections are monitored. It gives you an indication of where joins and breaks (well, the first break) is.
     
  4. davenn

    davenn Moderator

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    Sep 5, 2009
    yes thats the TDR (Time Domain Reflectometer system, Steve :) They were just coming into use in the last couple of years that I was with Telecom. It is very effective and was a lot quicker in giving the distance result than the older bridge method.
    TDR's for fault finding really took off with the advent of optical fibre cables that I only just got a start in playing with before the mass redundancies struck :(

    cheers
    Dave
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Like I said, I've only *seen* it :)

    ...and now I know what it's called :D
     
  6. davenn

    davenn Moderator

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    Sep 5, 2009
    if you ever get a chance to play with one go for it. doesnt have to be underground cables

    long length speaker lines, coax cable feeds etc etc

    are U back from the USA yet ? hopefully all went well :)

    Dave
     
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