The absolute resistance measurements obviously depend upon the actual length, but the ratio of resistances of live conductors and the CPC will be independent of the length.
Kind Regards, John
Ring Continuity Test
- Thread starter Jupiter01
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Kind Regards, John
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I get the impression he is looking for readings of a known length. IE real world tests.
That would obviously be the ideal, but don't forget that this whole discussion started because of the inconsistency between quotes resistances for conductors of different CSAs (both in BS 7671 and OSG, as well as elsewhere).
However, as I've said, the fact that you are invoking variability ('errors') due to manufacturing and measurement of an actual length of cable, I fear that your results will probably not be as conclusive as you might hope.
Kind Regards, John
The 'problem' being discussed, is that the figures given in BS 7671 and the OSG (both published by the same organisation) are not only both 'internally inconsistent' (i.e. implying a different resistivity has been used to produce the resistances/VDs for different CSAs) but are also different from one another.
That really makes no sense, and could be said to be unjustifiable ('unforgiveable' ?) !
Yellow shading indicates 'correct' resistances, green shading indicates 'correct to 1 decimal place.
Kind Regards, John
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How is this thread not dead yet? 
Presumably because people still think they have something useful to say/add?How is this thread not dead yet?
Although I do not remember where I first saw it, I have always considered 1.83Ωpm for a 10mm² conductorto be THE starting point for all my calculations thus negating the need to look at any other tables.
On the list I posted earlier, I have entered the OSG figures (unfortunately I had to look at it) and those calculated from my starting point.
Whilst there is not a huge difference, as we keep saying each publication should have the same ratios between values as mine in red?
On the list I posted earlier, I have entered the OSG figures (unfortunately I had to look at it) and those calculated from my starting point.
Whilst there is not a huge difference, as we keep saying each publication should have the same ratios between values as mine in red?
In addition to what John said, presumably because there doesn't seem to be an answer to the inconsistencies anywhere.How is this thread not dead yet?
Quite. As I've said, it seems particularly ridiculous that one organisation is publishing two sets of figures, both of which are internally inconsistent and which differ from each other!
The differences are, of course, so small as to be of no practical consequence, but I'm not sure that is "the point" (and certainly not 'an excuse')!
Kind Regards, John
You could try this method of obtaining the ratio of the resistances of the Brown wire and the Green wire.
The Amp meter is not essential if only the ratio is needed,
On short cables a constant current source in the better option given the low impedance of 2.5mm² cable
The Amp meter is not essential if only the ratio is needed,
On short cables a constant current source in the better option given the low impedance of 2.5mm² cable
That has been my query all along.
Fair enough but, as we have seen, the variations in 'the tables' is such that the choice of 'starting point' is essentially an arbitrary decision. You would obviously get slightly different answers if you used any other starting point (other than 1mm²).
Kind Regards, John
One could do that.
However, as I keep saying, the issue is not really in relation to the actual ratio of resistances of real-world lengths of cable (which will be subject to manufacturing and measurement tolerances/errors) but, rather to the various published tabulations, which ought to know better than to be internally inconsistent (and shouldn't really, be different from one another, either!)!
Kind Regards, John
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