My MIL has just moved house and it has a number of outside lights. Some are 12v and some are 240v.
A couple of circuits aren't working and the cables are buried underground. Does anyone know of a way of finding the route and/or checking where a cable break might be, - without digging up the entire lawn! ??
Find yourself someone who does groundworks / pavement repairs and has a C.A.T. (Cable Avoiding Tool) - a cable detector on steroids - and ask him to wander over your lawn. You can hire them from about £6 a day[1]. That will get you the cable route.
Get a capacitance meter and measure the capacitance across each end of the cable. The ratio of the two figures will show about how far along the cable the break is. That will get you where to start digging.
Ask previous owners where they buried the figging stuff.
Time domain reflectometer, I think. AIUI it has to be calibrated by cable type.
Even better, if you have the distances from two points, draw the arcs of the circles and where those arcs intersect is the point of break. Assuming the cable runs in reasonably straight lines of course.
BT use an instrument which is basically an oscilloscope and a pulse generator. The pulse goes down the cable and bounces back from where the break is. The initial pulse followed by the 'echo' are displayed on the 'scope, from which can be determined the time between the two and thus the distance to the fault.
Probably does not help with where the cable is located - though you could do the same for both ends, add the two lengths together and it would give the limits of where it could be.
I used to run about 3km of thick and thin Ethernet in ceiling voids, and there was never a TDR on the market cheap enough for `them' to let me get one.
I wrote an ethernet driver for the first ethernet chipset, the AMD LANCE
7990. That has a built-in TDR, and when the cable broke, our systems (GEC 4000 minicomputers) output on the console the TDR values, which is the number of 10MHz clock cycles which pass between transmitting the preamble and seeing its reflection from a cable break. Customers found this incredibly useful, and many picked a quiet time and went round their networks breaking the ethernet every 10 metres or so to record the TDR values the GEC 4000's generated, so when it broke for real, they could instantly home in on the 10m region of suspect cable. To this day, I remain amazed that no one else ever seems to have put this feature into an ethernet driver (although with switched twisted pair networks, it's now become redundant). OK, it's not as fine grained as a separate TDR instrument, but it was damn useful on networks of 10base5 and 10base2 that were around for many years.
Wouldn't that depend on the quality of the metal detector and the size of the cable? Of course you wouldn't know whether your detector/cable combination was working if you didn't find the cable! You could experiment I suppose, if you knew what sort of cable you were looking for, but that would involve a bit of digging up the lawn too :-) I'm sure there would be someone knowledgeable on uk.rec.metal-detecting. Also a little Time Team style trench at a right angle to your suspected cable run might be helpful, you should find some marker mesh/tape above the cable. None of that would help you find the damaged area of the cable though, if that is what causing your problem.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.