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Idea for a new tester...........

whjohnson

………….which helps work out where a buried wiring fault is? 

Having watched a youtube video

 

 where the electrician finds a short in a cable by measurement and calculation rather than stripping out the whole infrastructure I have been thinking that something like the process employed in the video could be turned into a test meter but I have no idea how to go about achieving it. 

Basically, what I had in mind was something the size of a multimeter with a display which would give a read-out in centimeters. The scale could be made seletable for whole metres too.

You program in the tabulated resistance value in miliohms for each cable size given in the OSG /  regs book onto some kind of chip. 

you make this a selectable range option with a dial on the meter, say 2.5mm/1.5mm for example. 

The range would go from 0.75mm to 10.00mm for the common cable sizes, so 1.00mm/1.00mm, 1.5 mm/1.00mm, 2.5mm/1.5mm, 4.00mm/1.5mm, 6.00mm/2.5mm, 10.00mm/6.mm. 

These are the common twin and earth sizes but an option could be included for cables with cores of the same cross sectional area such armoured or round flex e.g. 2.5mm/2.5mm etc. 

Selecting this would set the internal chip to the correct miliohms range value for that size cable. 

You then measure the ends of the cable - one measurement taken from each end (fault somewhere in the middle) and each measurement result would be displayed in centimeters. 

It would then be a simple case of getting the tape measure out and marking the wall or floor with the values given in centimeters by the test meter. 

Why make something like this? Well, it would speed up fault finding on site by not having to disturb vast amounts of building materials, floor coverings, cosmetic finishes etc. You would only need to focus upon a small area for remedial repairs and it would automate the calculation process to give a distance measurement rather than an electrical one. 

Achievable? If so, how? Being something of an old buffer who is a contacts and relays man rather than 0's & 1' I know nothing about silicon chips and programming etc. 

Going by gut instinct and not mkt research here, but if such an item were available I think I'd buy one. 

Do you think the idea has legs?

Your thoughts? 
 

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  • 0

    BT and the Teleco's already used such an instrument for finding faults in multi hundred meter long lines.

    It uses electronic pulses sent down the line and then the reflections from the fault which bounce back to the kit from the line are then analysed by the software in the kit to produce a graph.  When you look at the graph of the line's characteristics from start to finish on the screen you can then determine sort of where the fault is likely to be by the dips and bumps in the trace.  I gather does get difficult where the BT line is comprises of different types and conductor thickness along the route to determine which is the fault and which is the reflection from the discontinuity at the joins.

    I guess they are not cheap!

    I've forgotten what the kit is called - something like a Time Delay Reflectometer

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  • 0

    BT and the Teleco's already used such an instrument for finding faults in multi hundred meter long lines.

    It uses electronic pulses sent down the line and then the reflections from the fault which bounce back to the kit from the line are then analysed by the software in the kit to produce a graph.  When you look at the graph of the line's characteristics from start to finish on the screen you can then determine sort of where the fault is likely to be by the dips and bumps in the trace.  I gather does get difficult where the BT line is comprises of different types and conductor thickness along the route to determine which is the fault and which is the reflection from the discontinuity at the joins.

    I guess they are not cheap!

    I've forgotten what the kit is called - something like a Time Delay Reflectometer

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