How To Maintain & Use The Milwaukee Digital Refractometer - BRStv How-To
The Milwaukee Digital Refractometer required either distilled or RODI water for calibration and the refractometer is calibrated to zero. After calibration you can take a sample of your aquariums water and fill the sample bowl and then hit the large read button. You should see a light turn on below your water sample and then a reading will be displayed. You can choose from multiple conversions from PPT to S.G.
After you have your reading just discard the sample and wipe the bowl with a soft dry towel. We have found that calibrations are only required about once every six months or so.