I have a Mini Gerbil running my K40 so the amp meter doesn’t function. Like to know if anyone here has
installed a mA meter at the negative end of the tube and observed the actual mA with different Power% settings in Lightburn?
Your statement is a bit vague. An ammeter is always mounted in the cathode (-) side of a CO2 laser machine. Never “play” at the high voltage side (anode + HF).
The Mini-Gerbil controller has no influence on your ammeter but sets aside the original potentiometer for power regulation. This function will, if you have installed your Mini-Gerbil board correctly, be taken over by the new controller.
The percentage settings from LightBurn do not match the linear values of an ammeter but represent a certain value. Approx. 55% in LightBurn corresponds to 16mA of a tube which is reasonably new and in good condition.
16mA is a reasonable value for a 40Watt tube if it is to last for a little longer.
You need to “translate” the% settings yourself so that they match a curve to work with, best by doing some power tests.
@jkwilborn added a physical mA meter and has encouraged others to add them.
I’m sure he’ll be here shortly.
… was not a voltmeter that he has installed in the HF circuit?
I am fairly certain he did both. kV and mA.
The kV meter was a second mA meter with a huge resistor and a new gauge face.
I’m not sure of the question… and I have a Ruida. Never had possession of a K40…
Seems like they are not asking about anything but mA readings related to Lightburn…
I set up maximum current first.
My tubes maximum current is 21mA. Using the Ruida panel, I set my percent power to 50. While I’m lasing at 50% I set the lps for 1/2 of my target current or 10.5mA.
When I run 50% power on a Lightburn layer or via the control panel I get the 10.5mA and 80% gives me almost 17mA. Very consistent.
I do have a high voltage meter to watch the lps. Currently working on a ‘tap’ for my oscilloscope, I’d like to see what it’s doing… It would also give me a ‘measured’ response time for my lps that can be applied to ‘laying down dots’…
If you want to see how I built it…
Make sense?
Yes it was you, nice I remembered right 
You’re right, the original question itself is about the relation LightBurn% and the reading of mA on the ammeter.
I just got a little nervous when @PolloLoco62 asks about the correct placement of ammeter …
I should perhaps have pointed out that on a standard K40 psu it is not possible to adjust the output power with a small potentiometer on the circuit itself.
Hope I answered the question…
Ditto… 
Live and learn…
Don’t have a K40, how do you set maximum mA?
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