Akira Ooiwa

Method of evaluating frequency characteristics of pressure transducers using newly developed dynamic pressure generator

A dynamic pressure generator using a rotating valve has been developed to evaluate the dynamic characteristics and performance of pressure transducers. The waveform of the generated dynamic pressure is square, and the amplitude and fundamental frequency can be varied. In this paper, the generator using a novel rotating valve and the method of evaluating the frequency characteristics of pressure transducers using the generator are described. With the amplitude of the dynamic pressure of 10 kPa and varying the fundamental frequency in 1-Hz increments between 10 and 50 Hz, we measured the generated dynamic pressure using two different pressure transducers, and to obtain the amplitude spectrum of the measured waveform using frequency analysis. Then, the magnitude of the harmonic components in the spectrum are shown as a function of frequency. From the simultaneous outputs of two transducers, the frequency characteristics of one transducer was compared with that of the other.

New Mercury Interferometric Baromanometer as the Primary Pressure Standard of Japan

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.

Novel Nonrotational Piston Gauge with Weight Balance Mechanism for the Measurement of Small Differential Pressures

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 0,1 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.

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

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.

Report on CIPM key comparison of the second phase of multiples and submultiples of the kilogram (CCM.M-K5)

In order to show equivalence of mass standard determination among NMIs of CIPM member countries, key comparisons of mass standards have been carried out under the auspices of the CCM. At each NMI, mass standards are derived from one kilogram by means of the multiples and submultiples methods. The pilot laboratory, NMIJ, prepared five sets of transfer standards. Any set of transfer standard consists of five pairs of mass standards with nominal values of 200 mg, 1 g, 50 g, 200 g and 2 kg. The nominated twenty participants have been divided into four groups and the corresponding four sets of transfer standards have been circulated within the groups simultaneously while the remaining set has been kept at the pilot laboratory for the stability evaluation. The pilot laboratory measured the volumes, the centres of gravity and the magnetic properties, susceptibilities or magnetism, of the standards before the circulation and has reported these values to the participants. The pilot laboratory has also verified the stability of all travelling standards in advance. Nineteen laboratories have reported final results to the pilot. Nine participants belong to EURAMET, three belong to COOMET but two of them also belong to EURAMET, four belong to SIM, and five belong to APMP. Table 2 shows all the results associated with their uncertainties reported by the participants. As shown in table 3 the majority of the instabilities of the transfer standards during their circulation were less than the claimed uncertainties of the participants except for few standards of small mass, 1 g and 200 mg. These instabilities are considered for uncertainty evaluation within the group. All reported results among different groups have been linked based on the average values of transfer standards before and after the circulation. Figures 3 to 7 show the comparison results of all the participants for five nominal mass values respectively. The plotted results are expressed in relation to the median as reference values. Tables 10 to 19 show the differences and associated expanded uncertainties referred to a confidence level of 95% between any combination of the laboratories in the form of matrices. They show a few outliers, one at 2 kg and 200 g, three at 50 g, and two at 200 mg. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Determination of the amount of physical adsorption of water vapour on platinum–iridium surfaces

This paper presents the measurement of the physical adsorption of water vapour on platinum–iridium surfaces using a vacuum mass comparator. This value is of importance for redefining the kilogram, which will be realized under vacuum in the near future. Mirror-polished artefacts, consisting of a reference artefact and a test artefact, were manufactured for this experiment. The surface area difference between the reference and test artefacts was 226.2 cm2. This surface area difference was approximately 3.2 times the geometric surface area of the prototype of the kilogram made of platinum–iridium (71.7 cm2). The measurement results indicate that the amount of physical adsorption at a relative humidity of 50% is 0.0129 μg cm, with a standard uncertainty of 0.0016 μg cm. This value is 0.03 to 0.16 times that observed in other studies.

Magnetic properties comparison of mass standards among seventeen national metrology institutes

The ubiquitous technology of magnetic force compensation of gravitational forces acting on artifacts on the pans of modern balances and comparators has brought with it the problem of magnetic leakage from the compensation coils. Leaking magnetic fields, as well as those due to the surroundings of the balance, can interact with the artifact whose mass is to be determined, causing erroneous values to be observed. For this reason, and to comply with normative standards, it has become important for mass metrologists to evaluate the magnetic susceptibility and any remanent magnetization that mass standards may possess. This paper describes a comparison of measurements of these parameters among seventeen national metrology institutes. The measurements are made on three transfer standards whose magnetic parameters span the range that might be encountered in stainless steel mass standards.

A Heterodyne Laser Interferometric Oil Manometer

This paper describes the principle and performance of a novel manometer developed for the measurement of pressures in the range of up 1 kPa. A heterodyne interferometer using a Zeeman stabilized He-Ne laser was used to detect the displacement of oil surfaces which reflect the laser beam directly. A system of double U-tube and double interferometer was used to compensate errors caused by thermal and vibrational disturbances. The total uncertainty of the measured pressure P is estimated to be ± (2,1 + 0,032 P/Pa)mPa for gauge-mode pressures. The operation of the manometer has been confirmed by the calibration of three capacitance diaphragm gauges at gauge-mode pressures of up to 876 Pa.

Development of a new controlled-clearance pressure balance for hydraulic high-pressure standard

We are developing a new controlled-clearance pressure balance aiming to upgrade the hydraulic high-pressure standard up to 1 GPa. This new pressure balance consists of three parts: (i) a pressure generation device up to 1 GPa, (ii) a weight-loading unit which can load/unload weights automatically and independently, (iii) a controlled-clearance piston-cylinder assembly which is designed to allow the jacket pressure to be applied up to 50 % of the system pressure. In this study, the procedures for in situ mass calibration were developed and the mass of weights was calibrated. The results of the calibration were compared with those performed in 2003. The uncertainty of the mass was reduced compared with that in 2003 because the waiting time before data acquisition was set appropriately. The relative change in the mass was less than 2 ppm (parts per million) and the absolute value of the normalized error, En, was less than unity. Thus, it is confirmed that the weight-set is kept in a suitable condition and the mass of them is sufficiently stable.