DATA ADJUSTMENT IN DENSITY-MEASUREMENT OF SOLID BODIES BY HYDROSTATICCOMPARISON WITH SOLID DENSITY STANDARDS

High-accuracy measurements of the density of solid bodies are usually performed by the hydrostatic weighing method. In the classical approac h the reference is the density of the liquid in which the bodies are i mmersed. The problem of computing the best estimate of the measurand a nd its uncertainty is considered here. The complete system of equation s can be treated using weighted least-squares to estimate the mass and volume of the test objects, and their covariance can be found by foll owing a two-step procedure to build the covariance matrix of all input quantities. In the last twenty years solid standards have been establ ished through direct mass and volume calibrations. Hydrostatic weighin gs are still used to compare the solid standard and the bodies under t est. A different equation system is built from the experimental data a nd the evaluation of uncertainty is again obtained in the recommended way.