In article , "N_Cook"
wrote:

All online and my tables stop at 50 SWG. I don't know if the standard copper
resistivity formula breaks down over/less than 50 SWG. Wire in question ,
measured optically to about 0.05 mm diameter as too fine to mike up. About
19.7 ohm per metre but what is that in AWG or SWG ?

www.mwswire.com has tables down to 55 AWG. By my math, your resistance
figure translates to about 6000 ohms per 1000 ft., which would put it in
the 48 AWG category.

Diameter is going to vary significantly based on insulation.

..05 mm is about .002". If your micrometer can't measure that, you need a
better micrometer.