A regular multimeter will not read the PWM signal the Vmax or other 33Hz devices run at, neither will the one linked at madvapes. You will need an oscilloscope, or a meter which will read RMS.
To get an idea of where you are running, here is a review. There is a language selection on the left, but you can see the charts:
Vmax-Clone UniQ UMAX V1 aka ProMaxV Prototyp » Mountain Prophet
For example, it shows the VMax set at 3.0v with 2.6 ohms actually putting out 4.65v...
lol oh thats right. i forgot PWM was still a thing.
 
				
		 
 
		 
 
		 
 
		 
 
		 
 
		
 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		