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.

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The mercury U-tube manometer is a traditional pressure-measuring instrument and has played an important role as the primary standard in the atmospheric pressure range. It has also been used as the basis of standards for other pressure ranges. About thirty-five years ago, the National Research Laboratory of Metrology developed the precise mercury manometer using a white-light Michelson interferometer to detect the mercury menisci. We now introduce a new mercury U-tube manometer, developed as a national primary standard, to which some improvements and refinements have been added. Though the central principle is the same, the optical path of the reference arm of the interferometer has been redesigned to reduce the index-of-refraction corrections and some improvements have been incorporated to achieve more precise measurements on the U-tube conditions. The pressure range of the new manometer is 116 kPa and the uncertainty at 100 kPa is estimated to be about 0,4 Pa, in both absolute and gauge modes.

This report summarizes the results of a regional key comparison (APMP-IC-2-97) under the aegis of the Asia Pacific Metrology Program (APMP) for pressure measurements in gas media and in gauge mode from 0.4 MPa to 4.0 MPa. The transfer standard was a pressure-balance with a piston-cylinder assembly with nominal effective area 8.4 mm2 (V-407) and was supplied by the National Metrology Institute of Japan [NMIJ]. Ten standard laboratories from the APMP region with one specially invited laboratory from the EUROMET region, namely Physikalisch-Technische Bundesanstalt (PTB), Germany, participated in this comparison. The comparison started in October 1998 and was completed in May 2001. The pilot laboratory prepared the calibration procedure [1] as per the guidelines of APMP and the International Bureau of Weights and Measures (BIPM) [2–4]. Detailed instructions for performing this key comparison were provided in the calibration protocol [1] and the required data were described in: (1) Annex 3 – characteristics of the laboratory standards, (2) Annex 4 – the effective area (A′p′/mm2) (the prime indicates values based on measured quantities) at 23°C of the travelling standard as a function of nominal pressure (p′/MPa) (five cycles both increasing and decreasing pressures at ten pre-determined pressure points) and (3) Annex 5 – the average effective area at 23°C (A′p′/mm2) obtained for each pressure p′/MPa with all uncertainty statements. The pilot laboratory processed the information and the data provided by the participants for these three annexes, starting with the information about the standards as provided in Annex 3. Based on this information, the participating laboratories are classified into two categories: (I) laboratories that are maintaining primary standards, and (II) laboratories that are maintaining standards loosely classified as secondary standards with a clear traceability as per norm of the BIPM. It is observed that out of these eleven laboratories, six laboratories have primary standards [Category (I)], the remaining five laboratories are placed in Category (II).The obtained data were compiled and processed under the same program as per the Consultative Committee for Mass and Related Quantities (CCM)/BIPM guidelines. From the data of Category (I), we evaluated the APMP reference value as a function of p′/MPa. Then, we estimated the relative difference of the A′p′ values with reference to the APMP reference value for all participating laboratories and we observed that they agree well within their expanded uncertainties. We further estimated the effective area at null pressure and at 23°C (A′0/mm2) and the pressure distortion coefficient (λ′/MPa-1) of the transfer standard for all the participating laboratories. We then estimated the relative deviation of the A′0/mm2 from the reference value for all eleven laboratories and compared this with their estimated expanded uncertainties. The result is once again extremely encouraging and all these eleven laboratories ar...

Piston gauges are well-known standard instruments in the field of pressure metrology. But it is difficult to use them for small differential pressure measurements, because the pressure must be balanced against at least the weight of the piston, which generally corresponds to a pressure of several kilopascals. It is also difficult to reduce the pressure fluctuations caused by the rotation of the piston or the cylinder to lower than 0,l Pa. A novel type of piston gauge has been developed in order to solve these problems and to measure small differential gas pressures in the range 1 Pa to 10 kPa with a sensitivity of about 5 mPa. This piston gauge uses two special features, of which one compensates for the weight of the piston and the other centralizes the piston in the cylinder without rotation. These mechanisms enable an electronic balance to measure the force produced on the piston by a small differential pressure. WeighingReferences The balances are calibrated using standard weights with uncertainties less than 10 ppm.