Measurement of the volume of weights using an acoustic volumeter and the reliability of such measurement

Abstract

For the precise measurement of the mass of a weight, buoyancy correction of air for the volume of a weight is necessary. Although hydrostatic weighing is the most accurate method currently used in determining volume, it is a relatively complicated process requiring the weight to be wetted in a reference fluid. Since more weights with high accuracy of mass are being used, a more sophisticated method of determining volume that satisfies uncertainty requirements has been demanded to improve the efficiency of calibration. In this paper, an acoustic volumeter is proposed for the measurement of the volume of weights. An acoustic volumeter can measure volume in atmosphere in a simple manner. Consequently, it is not necessary to consider the contamination and mass change due to the liquid used in the hydrostatic weighing method. In practical applications, a procedure for measuring the volume of weights ranging from 100 g to 10 kg using an acoustic volumeter is proposed. The volumes obtained using an acoustic volumeter were compared with those obtained by the hydrostatic weighing method, and the reliability of the measurement was evaluated with a relative uncertainty below the order of 1 × 10−3. From the measurement results, it was shown that the use of an acoustic volumeter is effective for the measurement of the volume of weights.

Research on volume determination of mass standards with two acoustic measuring chambers

“…However, air near the surface of the test weight or reference weight and the wall of the containers changes isothermally [3]. Thus, during the measurement, the actual displaced volume in the chamber by the test weight,Vt0 and the reference weight, Vr0 can be expressed with (4) and (5).…”

“…Thus, the volume of the test weight, Vt, can be calculated with (9). This equation is used to evaluate the nonlinearity error caused by the effect of the weight's surface [3]. …”

“…The resulting sound pressure ∆P x is measured. The ratio of the pressures Rn can be calculated as ∆P 1 /∆P 2 [3].…”

“…For the weights with nominal value ranging from 100 g to 10 kg, a relative uncertainty of 1×10 -3 (k=2) is achieved. For weights ranging from 1 g to 100 g, the measuring combined standard uncertainty is below 0.0021 cm 3 [2]- [5]. An acoustic volume measuring system has also been designed at the National Institute of Metrology China (NIM) to extend the measurement range of the nominal value of mass weights up to 20 kg [7].…”

Numerical Study of Sound Pressure Distribution in Volume Determination with Acoustic Method

“…[1][2][3][4][5][6] an acoustic volume measuring system has also been developed by National Institute of Metrology China (NIM) to extend the measurement range of mass weight up to 20 kg. [7] The solid material's volume is determined by measuring to sound pressure in two closed chamber.…”