Hi I am looking for twin wire, red and white. I am told it is fig 8 and .22 gauge. However If I seperate the red and white, and pass one piece through my drill gauge it measures 1.5mm including the plastic. The wire i for bridging two computer mother boards. About 5 volts.
This refers to the structure of the cable. If you look at it end on you will see it resembles a “figure 8” or 2 circular wires side by side.
This is the sizing of the copper conductors without the insulation. This could be solid or 1 core or stranded, different standings are used which will affect the actual diameter of the cable. There are charts which relate the cross section area to gauge (gage in USA) size. By the way this will be 22 gauge NOT .22 gauge, no decimal. The standings can be broken down to X number of strands of Y gauge. For instance your 22 gauge wire could have i strand of 22 Gauge, 7 strands of 30Gauge, 16 (or 19) strands 0f 34 gauge right up to 168 strands of 44 gauge (very flexible). This applies to AWG (American Wire Gauge) which seems to be the most common. There are others, SWG (Standard Wire Gauge) being one and they are all slightly different.
Other methods of describing wire sizes are simply the copper cross section area in square millimetres or the actual stranding like 16/020 which means 16 strands of 0.2mm diameter wire. This is the one I sort of grew up with and I still prefer as it is more descriptive of the actual wire structure.
All this is very confusing I know but don’t worry too much if you don’t quite get it completely. I have been associated with this since I left school 70 years ago and I am still confused.
The voltage capability is more to do with insulation type and thickness. Just about any insulated wire available will handle 5V. The copper cross sectional area (gauge???) will dictate the maximum current capacity (amps or fractions of). All up I think your 22 gauge (0.32 - 0.35 sq mm) should handle just about anything a computer can throw at it except maybe the main 5V supply. You may need to go to 20 or 18 gauge for that. Depends how much current you have and what sort of voltage drop you can tolerate. If the connection is very short the voltage drop may not be a problem.
PS. The chart I mostly used is produced by Calmont Wire and Cable of California. Google Calmont and you should get a result.