I bought 3 of these digital gems (should have bought more for future projects) and of course tested each one : in parallel with my Fluke 77 on a lambda-regulated power supply at different voltages, all three read the thickness of a hair on a mosquito's ass. There is no adjustment potentiometer. you don't need it Also, the displays are NOT too bright - they're perfect - the company must have improved them. These gauges are probably more accurate than my Fluke. I am impressed. Stephen H. - Centrifugal Dynamics Co.