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Fortunately an analog ammeter is an amazingly cheap part, only a few dollars, and readily available.
This typically means an alignment problem. If you haven’t found our alignment resources yet, from K40 initial setup and regular maintenance: Alignment
The path that the laser takes along three mirrors and the lens needs to be precisely aligned. Here are three resources that may help you understand how to do this.
If you prefer video instruction:
Ep6: Laser Beam Alignment. The DIY CO2 Laser Cutter / Engraver Build Series
If you prefer written instruction, here are two guides:
- The “Tim the Floating Wombat” guide: K40-Alignment-Instructions.pdf
- The “smokeandmirrors” guide: laseralignment.pdf
Note that if the third mirror does not align the beam with the middle of the lens, the beam will not be focused correctly and will not be aligned with the hole in the nozzle. You may wish to use a device that helps you align using a red visible laser. One kind uses a “beam combiner” that slightly reduces beam power, and the other is a tool used only while performing alignment .
I would check on the physical side first; whether you are on m2nano or c3d being able to adjust power consistently as the tube ages and getting alignment right is the foundation.
One of your questions is based on a mistaken understanding; increasing power by distance isn’t something you want; you want to fix alignment instead. For more details I’ll defer to other forum members, but figured this might help get you started.