They are high precision optical instruments whose function is to determine the percentage of soluble solids in a liquid solution, using the principle of total refraction of light (arising from the type and concentration of the substances dissolved in a liquid solution, e.g. sugar), which takes place in the boundary layer between the prism and the sample. Therefore, it can be said that the Refractometer measures the density of liquids, the denser a liquid, the higher the refraction, the higher the sugar content, the higher the refractive index. Portable refractometers are simple, resistant and reliable, allowing us to make measurements in the laboratory or outside, with accurate measurements of temperature, refractive index, pH density and color with a small sample, leaving reliable results.