Digital Seawater Refractometers are the most accurate way to check salt levels in fresh or saltwater systems. No serious reef keeper or aquarium store is without one. These are geat for calibrating hydrometers. The new digital refractometers are precision optical instruments used for measuring concentrations of substances in aqueous solutions. They work using the principle of light refraction through liquids. When passing light through a liquid, the test result will be calculated by the computer and shown in the digital display.
Milwaukee refractometers are very simple to use: simply place one drop of your sample in the prism well, and read the results immediately!