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

Abstract

<div>The acoustic volume measuring method is a promising non-contact method for volume determination of mass weights. To improve the measuring accuracy of volume determination with the non-contact acoustic method, an acoustic measuring system with two measuring chambers is newly designed to compensate for the non-linearity measuring errors. When reducing the remaining air in the measuring chamber, the measuring accuracy can be greatly reduced. The volumes of mass standards ranging from 100 g to 5 kg are tested to evaluate the non-linearity errors of the volume measurement. The relative uncertainties of the acoustic volume determination are below 7.0 ×10<sup>-4</sup> (<em>k</em>=2).</div>

Milligram mass metrology using an electrostatic force balance

“…Although a detailed examination of the micromass results are beyond the scope of the current work, significant reductions in uncertainty are apparent using electrostatics relative to those expected from subdivision. Extrapolation of the trend in mass uncertainty in figure 1 indicates a relative standard uncertainty of approximately 10 −3 can be expected at 50 µg, and this result is approximately consistent with current published micromass uncertainties [34][35][36]. The EFB mass value is 50.633 (14) µg, so the uncertainty of this preliminary result is about an order of magnitude lower than current methods.…”

“…Figure 6 summarizes the results of three cross-check experiments over a time period of over 2 years. Another measurement of the 20 mg mass was published ten years earlier [18], and resulted in an EFB value of 20.917 69(45) mg, as compared to a subdivision value of 20.919 05 (35) mg where parentheses denote combined standard uncertainty. Between each EFB measurement, the balance mechanism was disassembled, modified and realigned.…”

Precise Volumetric Measurements of Any Shaped Objects with a Novel Acoustic Volumeter

“…Later on, this device was named the "acoustic pycnometer" [14], which is somehow misleading, since volumes, not densities, were measured. Further development was implemented in several prototypes, such as the acoustic bridge volumeter [15,16], the acoustical capacity/volume meter (RION Co., Ltd., Japan) [17], and their varieties [18][19][20]. There is also another type of acoustic volumeter based on Helmholtz acoustic resonance.…”

“…However, the cited acoustic volumeters [15][16][17][18][19][20] have several disadvantages. Firstly, the measuring chamber is connected with a closed volume on the back side of the loudspeaker.…”

“…Depending on both frequency and opening size, turbulent flow and redistribution of pressure in the chambers may occur, reducing sensitivity and impairing reproducibility. Moreover, these volumeters were designed to operate at a narrow frequency range and were used predominantly for the measurements of objects with smooth surfaces and volumes larger than 1 mL, such as mass standards [17,20].…”