diameter of strand from coaxial cable

Thread Starter

magy357

Joined Apr 6, 2019
7
Hi People.
I just trying to figured of correct numbers. As I do not have micrometer neither microscope or other precision tools, I just trying more "diy" methods.
I have plenty of coaxial cable RG 59 B/U with copper braided shield. The shield are from 16groups of 7 strands, 112 wires total. Copper wire, not CCA.
I just couldn't find what is exact diameter of that tiny wire. Lack of micrometer, I just take one wire and wound spirally on screwdriver. 30 spins measure cca 4mm, which giving result something between 0.125-0.14 mm of diameter single wire.
Do somebody have more precise diameter of that wire?

The point is to strip off that braided shield from cable as I do not have other use for it and use that braided part as flexible power conductor. And depend of diameter calculate ampacity of such conductor.

Sorry if that sounds silly, but I have good reason to use it in this way.

Thanks for any help.
Magy
 

AlbertHall

Joined Jun 4, 2014
8,381
What length of this wire do you have in one piece?
If you have lots then you might be able to get the result you want by measuring the resistance of the total length of the shield.
 

Thread Starter

magy357

Joined Apr 6, 2019
7
What length of this wire do you have in one piece?
If you have lots then you might be able to get the result you want by measuring the resistance of the total length of the shield.
Around 130m total length, but I need to cut it down and made shorter flexible flat cables, each around 0.5-1m max.
 

AlbertHall

Joined Jun 4, 2014
8,381
Around 130m total length, but I need to cut it down and made shorter flexible flat cables, each around 0.5-1m max.
Yes, but you can measure the resistance of 130m of the shield then look up wire tables to get the equivalent wire diameter.
Do you have a decent multimeter?
 

BR-549

Joined Sep 22, 2013
4,936
If the shielding is copper.........and if you have various sizes of solid copper wire......couldn't one weigh and compare it?

Take a length of shielding. Weigh it. Take the same lengths, of various diameter copper wires, and weigh them.

The shielding should be able to carry the matching wire's current..........and some more for safety.

If you understand this principle, not many wire sizes are needed to get a close ampacity.(wires can be folded and cut)

Think of it as a length and mass and resistance ratio. Should have added temperature.

I'll bet one could get quite precise with it, if wanted.
 

Thread Starter

magy357

Joined Apr 6, 2019
7
If the shielding is copper.........and if you have various sizes of solid copper wire......couldn't one weigh and compare it?

Take a length of shielding. Weigh it. Take the same lengths, of various diameter copper wires, and weigh them.

The shielding should be able to carry the matching wire's current..........and some more for safety.

If you understand this principle, not many wire sizes are needed to get a close ampacity.(wires can be folded and cut)

Think of it as a length and mass and resistance ratio. Should have added temperature.

I'll bet one could get quite precise with it, if wanted.
As the 132m cable is still on original wooden spool it would not be very handy, to strip it off and weight whole shielding and only then start working on flat cables. That would make mess in house and not very comfortable way working with.
Besides, I do not have various 132m cables to compare weights... sorry :)

So here is my calculations:
If the measured 2.1ohm/132m mean around 16ohm/km, it looks to me like 17AWG and around 20A for safe carrying for short distance (0.5-2m).
If I count 4mm per 30 spins, it take 0.125mm diameter wire (counted lower number for sure), 0.0122718463 mm2 each strand multiply by 112=1.37 mm2 copper area, which is close to 16AWG.
https://www.powerstream.com/Wire_Size.htm
So by those two measures I am getting more or less very similar results and should be safe with 20A. I guess that make sense to me, but I would be happy to check it for sure from somebody else to not make mistake.
 
Just use a camera and a ruler.

Take a pic of the wire magnified along with a known dimension like a ruler or small drill bit along it's diameter.
You could have it poke through a piece of paper bent if you want. Just put the ruler along the dimension you want to measure.

if you can't figure out how to do it, just post the pic here.
 

BR-549

Joined Sep 22, 2013
4,936
Cut off 12" section of shield. You may wad it up after cut. Weigh it. Write weight down.

Cut off a 12" piece of hook up wire and weight it. Keep adding 12" sections of hook up wire until it weighs the same as the shield.

You may look up ampacity of each wire online.

You will be simulating a unknown multi-strand........with a several known strand conductor......by weight.
 

panic mode

Joined Oct 10, 2011
1,788
digital caliper is $15-20
decent multimeter is also not exactly costing a fortune

btw why do you care about diameter of the shield strand?
 

AlbertHall

Joined Jun 4, 2014
8,381
So here is my calculations:
If the measured 2.1ohm/132m mean around 16ohm/km, it looks to me like 17AWG and around 20A for safe carrying for short distance (0.5-2m).
If I count 4mm per 30 spins, it take 0.125mm diameter wire (counted lower number for sure), 0.0122718463 mm2 each strand multiply by 112=1.37 mm2 copper area, which is close to 16AWG.
Yes, agree on the calculations. They are close enough to give confidence in the result.
 

sagor

Joined Mar 10, 2019
110
Several electrical specializations for RG59 give the shield resistance as 2.6 ohms/1000ft (8.53/km). (look up Belden RG59)
That resistance comes very close to standard American 14 gauge wire. That is rated at 15A at 60C, 20A at 75C (will run hotter at 20A) according to some "standards" that assume insulation over the wire.
In open air, it can handle 20A ok.
 

Thread Starter

magy357

Joined Apr 6, 2019
7
digital caliper is $15-20
decent multimeter is also not exactly costing a fortune

btw why do you care about diameter of the shield strand?
It is hard to get precise diameter in such tiny wire, with digital caliper or standard.

As my intention is to turn that braided copper sleeve to flat braided conductor, exact diameter of each wire tell me cross section area and therefore the best source for computing ampacity for that conductor.

For now I do not possess high quality multimeter or caliper (maybe later), that's why I come here to ask help.

Anyway... after multiple approach, I become to result "20A is safe", so it looks ok for me.
 
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