A refractometer is an optical precision instrument which determines the density of a liquid by the index of refraction.
This refractometer are special model for winemakers. The refractometer of diff. types has scales to quickly measure the sugar content and potential alcohol of the juice. Accurate, yet easy to use: simply place a few drops of liquid on the prism and the density is directly readable. There is no need for temperature correction due to automatic temperature compensation (ATC).