I tried the milwaukee digital but couldn't get it to validate with the provided validation solution or with my 53mS solution. It was about 0.002 off, which I read is within its range of error. This is after multiple attempts with lights on, lights off, palm covering the well, etc. etc. Gave up and went back to my trusty manual ATC refractometer, which exactly validated the milwaukee validation solution, milwaukee calibration solution, and my 53 mS solution.