Tube return wire gauge (amp meter)

[Ignas Kaz]

Installing amp meter today.

People posting how-to's but i dont remember ever mentioned what wire gauge to use.
Mostly i get "use whats already there", which is fair enough, but in case of chinese lasers there is no way to know as wire is not printed.
And what size SHOULD be used (i'm distrustful of chinese engineering here).

What are functional or safety considerations oversizing/undersizing ?

[sebastien laforet]

2 ways to find..

first. you have a 60W tube, for example. so, you target the same gauge you would use for a 60W light bulb. same power, more or less. take a security factor.

more scientific.

you have 20kV, and about 25mA, so the power is 500W (P=UI). in fact, less than that, because the signal is AC, not DC.

both those methods give you a point : a rather "standard" gauge that you would use for domestic electricity will do. (in europa, we would use 2,5mm2 wire, no idea how you count that in US units)

BUT!!!

be sure that the wire is well protected/insulated. because at 20kV, you really really do NOT want an electric arc from a bare section of metal to jump to the frame, or to your body!

also, related, but the highest the voltage, the less loss in the wire (and internal heating), that's why we use high-voltage AC current for power lines. suppose you have a 12V-40A-DC current (like in a car battery), you would need a far heavier wire than with your laser power supply.

[Pete Cyr]

2.5mm wire = 14 awg
14agw-16agw will work for your amp meter