Tube return wire gauge

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 ?

Tube is CDWG 80w (sustained).

It’s milliamperes of current. Wire gauge is not the priority as much as good practices for the tens of thousands of volts:

  • don’t use crimp connectors. Solder the crimp style connector to the wire and insulate / shrink tube all connectors on a wire

  • use well insulated wire

  • avoid any possible mechanical wear issues occurring to the wiring over time

  • use solid copper stranded wire (not Copper Clad)

If I were installing an ammeter on a laser, I wouldn’t be uncomfortable with using 14, 16, or even 18 AWG stranded at all (I would use whatever I had lying around for the return path wiring). I mean, think about the fact that 16 AWG wire is good for at least 10 amps (about 350 times more current than your laser tube wiring will demand).

Also consider that there will be a significant voltage drop post tube in the circuit. This is why you tend to observe quite a difference in the anode wiring vs cathode wiring styles.

I’m not really bothered by hot end of the tube wire, you wont see me messing with that.
I even put on silicone hose over HV line for better insulation, me being paranoid that way.

I want to understand what is happening at the “low” end of the tube.
You mentioned voltage drop - how much ? Whats on the output of the tube on that end ?

Do i use crimp connectors on the splice ? Do i solder (dont mind that)?
Should i be worried about arcing at the meter for whatever reason ?

I know i sound a bit paranoid for what might be a simple problem, but i’d rather be called paranoid and be alive :smiley:

For a 100 watt tube the current is less than 35 mA. That’s 0.035 amps.
Almost any wire that’s big enough to see is quite sufficient and the voltage drop at that current is completely insignificant unless you’re running a mile of it.

Use whatever you’ve got that’s handy.

Hank, the voltage drop mentioned isn’t in relation to the current on the conductor having any effect. We are talking about voltage drop across the laser tube / post laser tube (measured at the cathode).

On the high voltage side :slight_smile: :

On the “business end” of the laser tube, does this help to explain? I made a demo for you.

Understood. The voltage drop across the tube is essentially all of the available voltage. My point was that the voltage drop across the wire is so infinitesimally small at that current that any size wire would be sufficient.