Comparing Measured Wire Diameter to Cross-Section: Copper Wires, Caliper Accuracy

I look at copper wires from well-known manufacturers, such as are used in residential installation.
I take a caliper (accuracy 0.05 mm) and measure it and I have:
a) the wire marked 1.5 mm2 has a diameter of 1.1 mm
b) the wire marked with 2.5 mm2 has a diameter of 1.45 mm
c) the wire marked with 4.0 mm2 has a diameter of 2.05 mm

Meanwhile, from the formula for the cross section pi xrxr the result is as follows:
a) 0.95 mm2
b) 1.65 mm2
c) 3.30 mm2

Can someone explain this to me?
For those in doubt, I would like to add again that the cables are from well-known manufacturers.

Best regards.

And did you take into account that there is such a thing as insulation on the strands and on the wires, and in the case of non-wire strands, and the strings do not have 100% fill in the cross-section? There will always be some free spaces, which are sometimes filled up or not - there are quite a lot of wires and cables due to their design and parameters. Looking at the construction of cables, flat cables with wires in the form of a wire, not a string, fit in your reasoning. And even more aptly, cables in the form of flat bars, e.g. main ones, from the common ones like a hoop (5mmx20mm).

I should add that the cross-sections of the lines I am writing about are circular.
Hence the use of the formula for the area of the circle.
My question was that the cross-sectional areas calculated experimentally, i.e. from reality, are different than those provided by their manufacturer.
I asked for an explanation of this fact if there is any rational basis.
Best regards.

In short - why is the diameter of the cable core larger than it would be calculated from the calculations? I answered that in the second part of the first sentence. If you mean a conductor with insulation - what you call a wire, then there is a layer of insulation with probably obvious purpose.

Well, I understand that too now. Perhaps surveying is bowing. See if the manufacturer provides tabulated data for his products.

The conductor has a cross section with a certain tolerance.
From what I remember, this tolerance does not amount to several dozen percent.
I propose to check if the wires do not meet the conditions for one thinner in the row.
Maybe there was a mistake?

You may not be able to control a few% of the cross-section very easily, but I think I mentioned measurement - maybe you do not know, but the mass of people cannot use a caliper and I do not mention the micrometer screw. In addition, there will always be an error both in terms of the condition of the tool, its operation - crushing the wires will give this effect - and the shape of the wire - as it was bent before, it is difficult to get a circular cross-section, probably the caliper is already slightly worn and fell into a hole, which it likes with the rest to do in such things.

Out of curiosity, I have just measured the diameters and so, for example, for 1.5mm2, the diameter was 1.4mm, so when calculating the cross-sectional area, we get 1.53mm2, so it's okay. Maybe buddy you have some "left" wires, or you measure it wrong.

technics6 wrote:

According to to me it's just a fraud of the producers. For me and for 99% of people who deal with cables, it would never have occurred to me that a 2.5mmkw cable could have less ...

And this is the only correct explanation for this matter !!!

How do you know? Are you spying industrially or what? Do you even know the technological sequence or people related to the subject?

For several years I have not come across installation cables that have the same cross-section as provided by the manufacturer, usually 10 - 15% less. They can be even more understated in cables from supermarkets. Micrometer measurement so it's accurate. On an industrial scale, this means huge savings.

Andrzej, measure it again.

fuutro wrote:

You may not be able to control a few% of the cross-section very easily, but I think I mentioned measurement - maybe you do not know, but the mass of people cannot use a caliper and I do not mention the micrometer screw. In addition, there will always be an error both in terms of the condition of the tool, its operation - crushing the wires will give this effect - and the shape of the wire - as it was bent before, it is difficult to get a circular cross-section, probably the caliper is already slightly worn and fell into a hole, which it likes with the rest to do in such things.

I think that my friend probably offended me.
There is no mistake. The measurement was done many times, needless to say, in many DIFFERENT places, etc. - then the average was drawn. The caliper is also not just any kind.

I would like to add that if a colleague reads my post CAREFULLY, he would notice that I even gave the accuracy of the device reading and precisely calculated the cross-sectional areas, which may indicate diligence. I wrote in point c) not 3.3 mm2 but 3.30 mm2 because such a record proves that the calculation is between 3.295 and 3.305 (> = and

1.5 mm2 is approx. 1.38mm dia.

Bronek22 wrote:

technics6 wrote:

According to to me it's just a fraud of the producers. For me and for 99% of people who deal with cables, it would never have occurred to me that a 2.5mmkw cable could have less ...

The resistance of 1m or 2m of cable is measured using the technical method (not with an ohmmeter).
Then it comes out immediately as it really looks.
Because we are really interested in this resistance as an electrical parameter. And not the section itself. I did it and it turned out that it is not always like the producer writes.
You need a reference for this, e.g. a decade and a 4 digit digital voltmeter.
The power goes to 12V DC or less.

Producers take advantage of the fact that hardly anyone can do it and he still wants to.
5-10% of the deviation is irrelevant.
Bronek

As I understand what my colleague writes here, the parameter "conductor cross-sectional area" is determined by the method of comparing the resistance with a certain reference material.
Are there any standards for how this is done?
What material was adopted as the model?
The fact that the metric reading is smaller means that the material standard has a higher specific resistance (lower conductance) than the material actually used.
I would like some references to literature.
Best regards.

Added after 2 [minutes]:

slawekx wrote:

Andrzej, measure it again.

I measured it and it comes out the same.
See also my other posts commenting on the statements of "doubters".

Best regards.

AndrzejMS wrote:

Meanwhile, from the formula for the cross section pi xrxr the result is as follows:
a) 0.95 mm2
b) 1.65 mm2
c) 3.30 mm2

Can someone explain this to me?


Best regards.

Please explain where this result comes from.

krzysiek7 wrote:

For several years I have not come across installation cables that have the same cross-section as provided by the manufacturer, usually 10 - 15% less. They can be even more understated in cables from supermarkets. Micrometer measurement so it's accurate. On an industrial scale, this means huge savings.

So you have the same reflection as me. But if this is the case, then various industry institutions should react sharply to it.
We now have an instrument such as a class action.

For example, the Association of Polish Electrical Engineers would have historic merits for the country if it would end such practices. Unless they are on the belt of the same manufacturers.
If no one reacts to something like that, we will get to the point that we are only 1/2 meter 1 m long.
I understand competition and the need to lower prices, but giving wrong product parameters is probably a crime.

I am not from the electrical industry, although by building for myself I must have become an expert in this field - seeing how "professional electricians" screw up the job and in fact they do not know much.
They bought some material for me, gave me a cable and showed that it is 2.5 mm2 (it says this on the outer cover) and I can see that something is wrong. I took the caliper and began to inquire.
And that's all the rest.

Best regards.

Quote:

Quote:

Meanwhile, from the formula for the cross section pi xrxr the result is as follows:
a) 0.95 mm2
b) 1.65 mm2
c) 3.30 mm2

Can someone explain this to me?


Best regards.

Please explain where this result comes from.

Quote:

a) the wire marked 1.5 mm2 has a diameter of 1.1 mm

0.55 * 0.55 * 3.14?0.95

Quote:

b) the wire marked with 2.5 mm2 has a diameter of 1.45 mm

0.725 * 0.725 * 3.14?1.65

Quote:

c) the wire marked with 4.0 mm2 has a diameter of 2.05 mm

1.025 * 1.025 * 3.14?3.3


I just recount, I didn't measure anything myself.

slawekx wrote:

AndrzejMS wrote:

Meanwhile, from the formula for the cross section pi xrxr the result is as follows:
a) 0.95 mm2
b) 1.65 mm2
c) 3.30 mm2

Can someone explain this to me?


Best regards.

Please explain where this result comes from.

The area of the circle = pi * r ^ 2 = pi / 4 * d ^ 2 where d = 2 * r
r - radius
d - diameter
For a) this means:
3.1416 / 4 * 1.1 * 1.1 = 3.1416 / 4 * 1.21 = 0.7854 * 1.21 = 0.950 ...
In the above line, of course, we have roundings.
Similarly for b) and c).
Best regards.

AndrzejMS wrote:

As I understand what my colleague writes here, the parameter "conductor cross-sectional area" is determined by the method of comparing the resistance with a certain reference material.
Are there any standards for how this is done?
What material was adopted as the model?
The fact that the metric reading is smaller means that the material standard has a higher specific resistance (lower conductance) than the material actually used.
I would like some references to literature.
Best regards.

Best regards.

My colleague Bronek is probably saying that by measuring the resistance of, for example, a meter-long cable, we can calculate the cross-section of the cable using the formula:

? - resistivity,
R - resistance (resistance),
S - element cross-sectional area,
l - element length.


Where the resistivity is read from the table. For copper it is (at 20 degrees):
1.7 ? 10 ^ -8

Because in practice, it is important for an electrician whether the resistance of the cable corresponds to the reference resistance for a cable with a given cross-section, and not to the actual cross-section of the cable.

I understand it, but my question was what material is used as a "pattern".
In order for the actual diameter of the actual conductor to be smaller than the diameter of the reference conductor for the same resistance of the conductor section, the actual material must have a specific resistance lower than the reference conductor. If the reference is pure (crystalline?) Copper, the actual wire must probably have a large addition of silver to improve its conductance. Which of course I doubt. Unless contemporary material engineering achievements can do such miracles.