cable

[JohnW2]

4mm is electrical industry shorthand for the csa (cross sectional area) of a cable and its measured in square millimeters.

I think to call it 'industry shorthand' gives it too much legitimacy. It's sloppy language used by some of those who work in the electrical industry - on a par with those builders who talk of a 'yard' or a 'metre' of sand, ballast etc.

Kind Regards, John.

 

[holmslaw]

..

 

[JohnW2]

Your inexperience and lack of common sense is showing.

As you imply, our experiences are different. Many of the fields in which I've worked are ones in which sloppiness over units can, and has, cost lives.

I'd be very surprised if you could find any professional body in the industry which would give its blessing to the 'electrical industry shorthand' you mentioned.

Kind Regards, John.

 

[EFLImpudence]

I suppose, to be pedantic, it ought to be written 4(mm²) but I think 4mm² is accepted as meaning this rather then 16 square mm.

This subject arose because happyhippydad asked what the measurement actually was and was confronted by abbreviations, shorthand and actual fundamental inaccuracies which were of no help.

 

[JohnW2]

I suppose, to be pedantic, it ought to be written 4(mm²) but I think 4mm² is accepted as meaning this rather then 16 square mm.

If you want to remain off-topic, I don't think even the pedantic would say that, since "mm²" is a recognised unit, not a mathemical expression. However, if you wish to pursue the pedantic line of thinking, I would say that 4(mm²) is also ambiguous - and that it ought to be 4((mm)²). The problem for the pedants is that, if they looked on it as a matrhematical expression, 4(mm²) could be taken to mean 4(m(m²)) - in other words, four one thousandths of 1 m², aka 4000 millimetres squared!

This subject arose because happyhippydad asked what the measurement actually was and was confronted by abbreviations, shorthand and actual fundamental inaccuracies which were of no help.

Indeed - and I only got involved when I saw a 'actual fumndamental inaccuracy' which I thought ought to be corrected.

Kind Regards, John

 

[EFLImpudence]

I suppose, to be pedantic, it ought to be written 4(mm²) but I think 4mm² is accepted as meaning this rather then 16 square mm.

If you want to remain off-topic, I don't think even the pedantic would say that, since "mm²" is a recognised unit, not a mathemical expression. However, if you wish to pursue the pedantic line of thinking, I would say that 4(mm²) is also ambiguous - and that it ought to be 4((mm)²). The problem for the pedants is that, if they looked on it as a matrhematical expression, 4(mm²) could be taken to mean 4(m(m²)) - in other words, four one thousandths of 1 m², aka 4000 millimetres squared!

Oooooh! that's logical.

Presumably we should write 4sq.mm.

 

[Taylortwocities]

If you say the floor area of a room is 2m² then that is a proper measure. That is 2 metres squared. eg a space 2 metres by 2 metres, or variations of....

Would you perhaps like to revisit that arithmetic?

Kind Regards, John.

Ahh apologies. have revised the post to read 4. That's Sunday mornings for you.

 

[JohnW2]

Ahh apologies. have revised the post to read 4. That's Sunday mornings for you.

It was obviously a good Saturday night - that 'Sunday morning' was actually 4.18pm

Kind Regards, John.

 

[Taylortwocities]

Sunday Xmas lunch drinks party. Where does the time go to, or from, I forget...

 

[happyhippydad]

Wow

What a response to an old thread from years ago!

Thankyou verymuch to you all for giving me a thorough explanation.

At last I now understand..

When a cable is 4mm this is the area of the cross section.

I cant believe I'm going to get involved with the discussion but it has made me smile

Cant remember who said it but it does worry me abit when people say 4mm2 (4mmsquared) when really the cross sectional area is 4square mm or 4 (mm2). 4mm2 and 4square mm are completely different.

I guess thats why I thought the 4mm must refer to the diameter because its just a figure denoting length not area.

Thankyou all again verymuch, you may now continue your debate.

happyhippydad

 

[JohnW2]

Cant remember who said it but it does worry me abit when people say 4mm2 (4mmsquared) when really the cross sectional area is 4square mm or 4 (mm2). 4mm2 and 4square mm are completely different.

To be fair, 4mm² is universally and globally accepted to mean 4 square mm, so they aren't actually different. What is different (and what I presume you are thinking of) is 'a 4 mm square" (whose area is 16mm²).

I guess thats why I thought the 4mm must refer to the diameter because its just a figure denoting length not area.

No-one could possibly blame you for that (logical) assumption - which is why I said that sloppiness over units can be dangerous.

Kind Regards, John.

 

[ericmark]

As I said with the correction there are conventions as to how it should be written.
1 mm² (square millimetre) = (1 mm)² = (0.001 m)² = 0.000 001 m²
Please note gap between 1 and mm this is required.

The problem is code 00B2 or 0178 should produce a ² but it does not work. In the main cutting and pasting will produce a 2 where the superscript is stripped out so it becomes hard to write ² the only way I know is to cut and paste from word.

So one has to use some common sense so either sq mm or mm sq is the easy way. Either will do really. But if one considers people who want to buy cable will need to look up what the installation method is and the material used for insulation it is very unlikely after doing this that they don't realise cable sizes are given in cross sectional area. So 7/0.35 should not really need an explanation that it refers to 7 cores of 0.35 mm² it should be self evident. As a lad I would often refer to 14/0.012 cable and now without looking up not a clue if the 0.012 was in mm² or inches² got a feeling the latter. I knew it was good for around 10A and that was all that mattered.

The whole reason for giving area and not diameter is because not all strands are round. Triangle shaped strands are quite common. Unless they are other than round then the total diameter of all strands will be more than the simple calculation as there will be an air space. So the total will be between 0.196 an 0.216 for a 2.5 mm² depending if measured in trough or peak of cable which will be a problem with a twisted cable knowing which is being measured. because of skin effect stranded cable will take a little more power than solid core but it means knowing the diameter of whole seven cores is not that helpful.

So in real terms either we find it written on the cable or we test by trying to fit a terminal designed for cable and find best fit.
Now if a 10mm² terminal fits the cable snug it's 10mm² and in real terms there is no need to know it's diameter. We just use terminals as go/no go gauges.

So get some 28/0.012 cable and some 4 mm² cable and tell me which is which? I have roles of cable in my garage from days when I worked on wagons and once off the role telling which is auto cable and which is mains is not easy. Even colours don't help at brown was unfused live. Both will not fit a blue crimp but will fit a yellow crimp.

Just can't understand why so much talk about how to name it and so little on how to identify it.

 

[JohnW2]

So 7/0.35 should not really need an explanation that it refers to 7 cores of 0.35 mm² it should be self evident. As a lad I would often refer to 14/0.012 cable and now without looking up not a clue if the 0.012 was in mm² or inches² got a feeling the latter.

Eric, with respect I think you are at risk of totally confusing people. The second part of the 14/0.012 you referred to as a lad was not in either mm² or inches² , because it was the diameter of the strands - and, to this day, the 'd' of the S/d format of specifiying a stranded cable refers to diameter, not CSA.

Kind Regards, John.

 

[RF Lighting]

I think you're both in danger of boring everyone to death.

 

[JohnW2]

I think you're both in danger of boring everyone to death.

You're probably right, but I find it difficult to sit back and see confusing misinformation being left uncorrected on a public forum. The discussion was initially essentially pedantic and 'semantic', but we now have overtly incorrect statements appearing. It has just been suggested that, for example, "24/0.2" flexible cable would have a total CSA of 4.8 mm² - whereas, as we know (or should know!), the truth is that the total CSA of such a cable is 0.75 mm² - there are some serious potential errors to be made there!

Kind Regards, John.