Hydrostatic Scale: What Connects Archimedes with Anton Paar?

More than 2,000 years ago, a physicist called Archimedes made a discovery: The buoyancy of an object in a liquid equals the mass of the displaced liquid. This principle is the basis for the calculation of other parameters, e.g., the density of the liquid. Thus, it also describes the basic function of a so-called hydrostatic scale. Such a scale was developed by Anton Paar and has been used for the production of density standards since the beginning of 2022.

Precise – more precise – hydrostatic scale
With the hydrostatic scale a silicon ball is dipped into the liquid that is to be measured; from its mass, its volume and the displacement of liquid, the density of the liquid can be determined. The scale is much more precise than most other measuring variants – its measurement uncertainty is only 0.003 to 0.004 kg/m3. This makes it the most precise technology for the density characterization of liquids according to the most recent status.

Its precision correlates with many influencing factors, for example, discrepancies of temperature and the pressure of the liquid. These are continuously measured during the weighing – which takes between 24 and 72 hours – and the calculations are corrected accordingly. Furthermore, the scale is continuously adjusted with calibration weights in order to negate external effects and enable a precise measurement. Factors like time of the day, moon phase and installation position have an impact on density measurement.

Production of density standards
Using the hydrostatic scale at the headquarters, Anton Paar is able to certify various liquids as verified density standards. Packed in small glass ampules, calibration technicians and customers can use these standards, e.g., for the calibration of density meters.

The hydrostatic scale puts Anton Paar in the top tier of density measurement: precise digital density meters and even more precise density standards from one provider.