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By precisely weighing the volume of a solution (wort or beer) against the same volume of a reference solution (water) at 20 °C, the relationship of the submerged weights (specific gravity), which are dependent on their buoyancy, is calculated through division and is expressed as SG_A20/20 [1]. 

Determining the density by using the buoyancy of a hollow body of constant volume requires an aræometer (hydrometer) with a suitable measurement range. The buoyancy corresponds to the weight of the water displaced by the submerged hollow body and is directly proportional to the density of the displaced fluid.

After distillation of the sample, the original gravity, alcohol and real extract content of the beer in beer-based beverages or other beverages can be determined from the densities of the distillate and residue.

Rather than utilizing the classic method for analyzing beer by means of density measurement and/or alcohol determination, this device employs thermoanalytical analysis techniques. With two thermoanalytical measuring cells, the beer sample is heated to 40 °C and 65 °C, and the specific heat capacity is determined. Algorithms are used to assign the results to the concentration of the various ingredients. In this way, alcohol content, apparent and real extract, and original gravity are calculated.

The refraction of a light beam as it passes from an optically less dense (sample liquid) to an optically denser medium (prism) is a function of concentration (alcohol/extract), temperature and wavelength. The density of the test liquid is a function of the concentrations of alcohol and extract content. Therefore, from the refractive index (or alternatively the refractive index n_D20 and the density or the SG_A20/20, the real extract), the alcohol and original gravity can be determined from nomograms or using regression equations.