Research regarding the double-weighing in air volume determination method

This study utilised a combination of error correction models and an influence mechanism function analysis to study the influence mechanism of air density on volume determination by the double-weighing in air method. The results revealed the law of the combined error of air density and surface desorption with atmospheric pressure. For the perspective of a single fluid, the principle of volume determination by the double-weighing in air method within a small density variation range was clarified. An error correction model for volume determination by the double-weighing in air method was also built; this model was based on the physical properties of thermal expansion. Based on the mathematical model and the working principle of the measuring device, three primary factors that affected the results were identified and analysed: the atmospheric pressure range, the weight surface desorption effect, and the mass comparator properties. Taking 20 g, 500 g, and 1 kg OIML stainless-steel weights as examples, the volumes determined by this method were compared with those determined by the hydrostatic method. The normalised error was less than one, which proves that the results of this method were consistent with those of the hydrostatic method.