Cable Diameter measurement

[EEVaditya]

Hello,

How to determine the AWG of a wire ?

[frozenfrogz]

https://en.wikipedia.org/wiki/American_wire_gauge

[Ian.M]

Once you have an AWG table with diameters handy, you need to make the actual measurement.

For stranded cables and larger wires, vernier or digital callipers are suitable.  If the wire is insulated, cut round the insulation and pull it partially off (or cut round a second time and peel off the insulation between the cuts) to expose a ring of the bare wire to make the diameter measurement on, with the end still trapped in the insulation so the lay of the strands isn't disturbed.  Avoid twisting the exposed section as you work.

For fine wires you need a micrometer.  For fine stranded wires, count the strands and measure a few individually and take the average.    For greatest accuracy, magnet wire should be chemically stripped to remove the enamel.

You can get AWG gauge plates, which are useful for larger wires and cables when great accuracy isn't needed, but make sure you get one from a reputable supplier that is actually marked as being for AWG wire, as there are many cheap ones on EBAY and similar which are either misdescribed as AWG gauges or have incorrectly sized gauging notches.

[tooki]

But isn’t the AWG of stranded wire a function of its total cross-section, not the diameter of the bundle?!? My understanding is that different strandings of the same AWG may have different actual diameters. As such, my understanding is that only solid (not stranded) wires can have their cross-section or AWG determined correctly by measuring the diameter.

[Ian.M]

Yes, that's right, but for simple spiral laid stranded wire you can get pretty close by assuming 10% voids, and as the area is proportional to the square of the diameter, multiplying the measured diameter by 0.95 before looking it up is good enough for most purposes.   However this breaks down for low strand counts and more complex layups that leave voids between bundles of strands. and in those cases you should dissect it, count the strands and use a micrometer on a few of them then look up the total copper CSA, not the diameter.