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

………….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? 
 

Parents
  • I can vouch for the basic technique of using resistance measurements to locate a short - I did just that once many years ago to trace a problem with a friend's kitchen socket which appeared to be unearthed yet showed continuity between its two c.p.c.s … turned out some muppet had tried to extend the ring using a single 4-terminal joint box and jointed the c.p.c.s outside .. but had picked the wrong pairs of c.p.c.s. to join. ?

    I've only needed to use that technique on a very few occasions however, so would doubt the value of having a dedicated meter to do it. I could be built into something like an MFT I suppose, but selecting the right cable size (of out of very many) would be tedious using the simple button human interfaces they usually use. A windows like drop-list would be easier.  So I guess stick with an ordinary Ohm meter (there's not much need for 4-wire probes if you can zero out the normal leads) and perhaps an App for a phone or a simple bit of calculation built into a web page somewhere.

       - Andy. 

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  • I can vouch for the basic technique of using resistance measurements to locate a short - I did just that once many years ago to trace a problem with a friend's kitchen socket which appeared to be unearthed yet showed continuity between its two c.p.c.s … turned out some muppet had tried to extend the ring using a single 4-terminal joint box and jointed the c.p.c.s outside .. but had picked the wrong pairs of c.p.c.s. to join. ?

    I've only needed to use that technique on a very few occasions however, so would doubt the value of having a dedicated meter to do it. I could be built into something like an MFT I suppose, but selecting the right cable size (of out of very many) would be tedious using the simple button human interfaces they usually use. A windows like drop-list would be easier.  So I guess stick with an ordinary Ohm meter (there's not much need for 4-wire probes if you can zero out the normal leads) and perhaps an App for a phone or a simple bit of calculation built into a web page somewhere.

       - Andy. 

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