Kazunori Ide

Precise determination of the pressure distortion coefficient of new controlled-clearance piston-cylinders based on the Heydemann-Welch model.

A new controlled-clearance (CC) pressure balance has been developed with the aim of improving hydraulic pressure standards up to pressures of 1 GPa. The pressure balance is equipped with a weight-loading unit that can load/unload selected weights automatically and a CC piston-cylinder that is designed for the jacket pressure to be applied independently. In this paper, the effective area A(e) of two kinds of the CC piston-cylinders for pressures of 200 and 500 MPa was examined based on the Heydemann-Welch model. The two parameters in the model, the jacket pressure coefficient and the zero clearance jacket pressure, were precisely determined by the characterization experiments, after which the pressure dependence of A(e) and its uncertainty were estimated. The uncertainty due to the pressure dependence of A(e) for the 500 MPa CC piston-cylinder was less than 7.5x10(-8) MPa(-1). To confirm the consistency of the estimations, the results of the two CC piston-cylinders were compared through a free-deformation (FD) piston-cylinder; the two estimations were in agreement with each other. Moreover, it was shown that the extent of nonlinearity in the pressure dependence of A(e) of the FD piston-cylinder can be evaluated by calibration against the CC piston-cylinder.

Estimation of the effective area of the controlled-clearance pressure balance for pressures up to 500 MPa

We are now developing a new controlled-clearance (CC) pressure balance with the aim of improving the hydraulic pressure standard. The effective areas of the three kinds of CC piston-cylinders, whose maximum pressures are 100 MPa, 200 MPa, and 500 MPa, were estimated based on the Ileydemann-Welch model. To estimate the pressure dependence of the effective area, two characterization experiments, fall-rate and cross-float measurements, were performed. In this paper, the procedures for the characterization experiments are explained in detail. Then, results of the experiments for the 100 MPa CC piston-cylinder are presented. To verify our estimation of the effective area based on the Heydemann-Welch model, piston-cylinders were calibrated against the evaluated CC piston-cylinders and against our current pressure scale separately. Then, two results were compared in terms of the pressure distortion coefficient. For all pressure ranges, two results were in good agreement with each other. It is found that the estimation of the pressure dependence of the effective area is consistent with our current pressure scale.

Final report on supplementary comparison APMP.M.P-S8 in hydraulic gauge pressure from 100 MPa to 1000 MPa

This report describes the results of a supplementary comparison of hydraulic high-pressure standards at two national metrology institutes (NMIs) – National Metrology Institute of Japan, AIST (NMIJ/AIST) and Physikalisch-Technische Bundesanstalt (PTB), Germany – which was carried out during the period January 2007 to March 2007 within the framework of the Asia-Pacific Metrology Programme (APMP) and the European Association of National Metrology Institutes (EURAMET) in order to determine their degrees of equivalence at pressures in the range 100 MPa to 1000 MPa for gauge mode. The pilot institute was NMIJ/AIST. NMIJ/AIST used a hydraulic pressure balance and a pressure multiplier, and PTB used a controlled-clearance pressure balance as their pressure standards. High-precision pressure transducers were used as a transfer standard. The sensing element of the transducers was a foil strain gauge. To ensure the reliability of the transfer standard, two pressure transducers were used on the transfer standard unit. At the beginning and the end of this comparison, the transfer standard was calibrated at the pilot institute. From the calibration results, the behaviour of the transfer standard during the comparison period was characterized and it was found that the capability of the transfer standard for the purpose of this supplementary comparison was sufficient. The degrees of equivalence of the national measurement standards were expressed in terms of deviations from the supplementary comparison reference values and from each other, considered in combination with associated uncertainties of these deviations. The hydraulic pressure standards in the range 100 MPa to 1000 MPa for gauge mode of the two participating NMIs were found to be equivalent within their claimed uncertainties. 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 APMP, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Methods of precisely estimating the jacket pressure coefficient of controlled-clearance piston-cylinders at pressures up to 1 GPa

Deformational characteristics of a controlled-clearance piston-cylinder (CCPC) have been evaluated to precisely estimate the pressure dependence of its effective area. Among the experimentally accessible characteristics, the jacket pressure coefficient d, which denotes the relative change in the effective area due to applied jacket pressure pj, is examined in this paper. Two methods for precisely determining d at pressures up to 1 GPa are proposed. One is a comparative method that uses a set of a pressure balance and a multiplier as the tare gauge. The other is a new method that uses precise pressure transducers as monitoring devices. Both pj and weights loaded on the CCPC are changed so that the pressure generated by the CCPC remains constant, which is monitored by the transducers. d is estimated by the relative change in the weights loaded on the CCPC itself. Using the two methods, d for a 1 MPa kg−1 CCPC is measured at pressures up to 1 GPa. At each system pressure, d obtained by each method is approximated by a linear function of pj. The consistency of the fit values of d by the two methods is confirmed. The method using pressure transducers as monitoring devices is advantageous in terms of efficiency and operability especially at higher pressures.

Transfer standard for high pressure up to 1 GPa using pressure transducers

A transfer standard for high pressure up to 1 GPa using pressure transducers has been developed at NMIJ/AIST. The transfer standard consists of two pressure transducers, a measuring amplifier, a device for measuring environmental condition, connecting parts, and a laptop computer. The sensing element of the pressure transducer used is a foil strain gauge. The transfer standard can be used in an interlaboratory comparison for pressure standard. In this paper, the transfer standard developed and the measurement protocol for the comparison are described.

Development of Pressure Standard up to 1 GPa using a Precise Pressure Multiplier

The pressure standard up to 1 GPa using a precise pressure multiplier and a pressure balance has been developed. The multiplying ratio of the pressure multiplier, which is the ratio of high pressure to low pressure, is about 10. The pressure multiplier has low and high pressure ports and is capable of generating pressure of 1 GPa at the high pressure port when pressure of 100 MPa is applied to the low pressure port. The pressure for the low pressure port can be applied accurately using a pressure balance. The multiplying ratio of the multiplier was precisely measured as a function of pressure by applying known pressures to both the ports. Using the multiplying ratio measured, the pressure generated at the high pressure port was calculated up to 1 GPa. In this paper, the methods for evaluating the multiplying ratio of the multiplier and for calculating the pressure generated using the pressure multiplier up to 1 GPa with its uncertainty are described in detail. Also, the characteristics of some pressure transducers evaluated using the pressure standard developed are shown

Progress in development of controlled-clearance pressure balance in NMIJ

A new controlled-clearance pressure balance is under development with the aim of improving the hydraulic high-pressure standard up to 1 GPa. This 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 which is designed to allow the jacket pressure to be applied independently. Some adjustments were made for loading heavy weights on/off the piston safely, keeping them in balance, then generating the pressure stably. Stability of the generated pressure was checked for several piston-cylinders, and it was found that pressure fluctuation was less than a few parts per million. The jacket pressure coefficient of a 500 MPa controlled-clearance piston-cylinder was precisely evaluated as a function of both the system pressure and the jacket pressure.