How to I measure wire thickness

[g35me]

Is there a way of measuring the diameter of a multi strand wire and converting it back to mm2?

[Shadow]

to approximate it, just measure the overall thickness of all the strands (try to make sure the part your measuring is cylindrical, not flattened out) and then halve it, square it, andfinally multiply by 3.14.

To get an accurate measurement, you need to measure the diametre of a strand and then halve it, square it, multiply it by pi (3.14159) and multiply it by the number of strands.

Area of a circle = Pi x R^2 where R = radius(half the diameter).

Area = pi x (D/2)^2

[badger]

see what size lug it fits snuggly into. or do what us sparky do n take a wild guess:P

[g35me]

thats good, thanks

[David_S]

I had this problem when choosing cables for the wiring for my efi conversion. There seems to be a lot of confusion as to how to measure cables.

I ended up using Narva cable mostly and found that

2.5mm cable has 8 (9?) strands of 0.32mm wire to give a wire area of 0.62 sq mm
3.0mm has 16 strands (1.13 sq mm)
4.00mm has 26 (1.85 sq mm)
5.0mm has 41 (2.90)
6.0mm has 65 (4.58)

You can get cable info from the Narva website. At least I did but when I checked just now the site had changed and I could not find their cable range at all!

[Shadow]

I had this problem when choosing cables for the wiring for my efi conversion. There seems to be a lot of confusion as to how to measure cables.

I ended up using Narva cable mostly and found that

2.5mm cable has 8 (9?) strands of 0.32mm wire to give a wire area of 0.62 sq mm
3.0mm has 16 strands (1.13 sq mm)
4.00mm has 26 (1.85 sq mm)
5.0mm has 41 (2.90)
6.0mm has 65 (4.58)

You can get cable info from the Narva website. At least I did but when I checked just now the site had changed and I could not find their cable range at all!

the number of strands and strand thickness can change though.

So you could have 3.00mm cable with 50 strands, or with 4 strands.

[David_S]

the number of strands and strand thickness can change though.

So you could have 3.00mm cable with 50 strands, or with 4 strands.

Yeah that's right, but most automotive cable is similar so it is a good starting point. The best way is to use the manufacturer's specification for the particular cable but that is not always easy to find especially if you don't know the manufacturer. Failing that, measuring the dia and calculating the x-sectional area of a strand and then multiplying by the no. of strands as you suggest is theoretically correct but practically the difficulty is in measuring the strand dia. accurately. A small error is magnified by the number of strands.

I only produced the table for my own use when wiring up the efi so that I could readily check the cable size by counting the strands. 2,5, 3 and 4mm can all look similar if you are not a sparky. And as I said I standardised on Narva and used the areas and current capacity given by Narva. The areas were necessary to compare with AWG specifications which was what my Megasquirt ecu instructions used.

So it really depends on what Brian needs the sq. mm for.