Vol.4 No.4 2012

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Research paper : Improvement of reliability in pressure measurements and international mutual recognition (T. Kobata et al.)−222−Synthesiology - English edition Vol.4 No.4 (2012) System (JCSS) based on the Measurement Laws. Figure 11 shows the outline of this system. The values of the national standard are provided in the major pressure ranges for gas and hydraulic pressures, by AIST calibrating the pressure balances of the JCSS calibration lab. The JCSS calibration labs owns the standard device traceable to the AIST’s national standard, builds the quality system through common requirements and application guideline, and are assessed by the accreditation organization. The JCSS calibration lab calibrates the various industrial pressure gauges under the JCSS using their own standard devices. AIST engages in the creation of the technical standard for pressure for JCSS, and also supports and cooperates in the accreditation assessment from the technical standpoint.Currently, the list of accredited calibration labs and their best measurement capability can be seen under JCSS, Conformity Assessment in the website of the National Institute of Technology and Evaluation (NITE) (http://www.nite.go.jp/). As of September 2011, there are 13 calibration labs accredited in the “Pressure” section of JCSS. The number of JCSS certificates issued by the calibration labs has increased in the past three years, and about 2,300 certificates were issued in FY 2010. The number of certificates issued is expected to increase further in the future. The importance of the pressure measurement traceable to the national standard is increasing in the Japanese society and industry. The types of pressure gauge most calibrated are the digital pressure gauge and the mechanical pressure gauge. As mentioned earlier, the measured values of such pressure gauges are not directly affected by the acceleration of gravity, hence they do not have to be corrected and the traceability can be maintained easily. Also, the pressure balance that is normally used as the standard device in the high-pressure range tends to be large, and this may be a major burden on the calibration lab and the user for its installation and maintenance. However, the burden can be reduced by using the digital pressure gauge as the standard device.While it is not discussed in this paper in detail, the organization of the differential pressure standard has progressed recently. There is a system where the JCSS calibration labs can set the differential pressure standard themselves using two JCSS calibrated pressure balances[8][15]. While the method using the two pressure balances ensures high precision, it is not a simple method that can be use in daily calibration work. Therefore, we developed the standard provision system using the digital differential pressure gauge to widely and efficiently disseminate the differential pressure standard. The calibration of the digital differential pressure gauge by the JCSS calibration labs has been available since 2008, and it has become possible to efficiently provide the differential pressure standard.AIST has cooperated as the technical experts to organize various industrial standards[11]-[13] and technical standards, to enable the users of the pressure gauge and industry to utilize the technologies and findings pertaining to the property evaluation of the digital pressure gauge and the calibration method obtained by R&D. Particularly, procedures of characterization and calibration for digital pressure gauges were set in JIS B 7547[12].The calibration method and the technology using the digital pressure gauge are improving the reliability of the pressure measurement at industrial sites through the AIST’s calibration service, Japanese standard system, and various measurement and technical standards. In the development described in this paper, the main focus was on the use of relatively high precision digital pressure gauge. In the future, to maintain the reliability of pressure measurement efficiently and at low cost, it is necessary to apply the developed property evaluation and the calibration method to general industrial digital pressure gauge, and to incorporate them into the standard system.The remote calibration is a technical development to reduce the burden on the client and to conduct the standard provision quickly, at low cost, and accurately. In this R&D, the basic technology necessary for remote calibration for pressure, or the technology to conduct calibration in a short time while maintaining reliability at the industrial site was developed. However, since the manufacturing cost of the transfer device for remote calibration is not kept low, currently the calibration cost is not lower than the carry-in calibration, and this is one factor that inhibits its wide use. Also, the framework for accrediting the calibration lab that conducts remote calibration is an issue. In the future, we would like to promote the use of Fig. 11 Japanese standard provision system for pressureNMIJ, AIST calibrationJCSS calibrationJCSS calibrationJCSS calibrationjcssNote 2) calibrationPressure balance, liquid column manometer, digital pressure gauge, mechanical pressure gaugeGeneral pressure measuring device on siteUserPressure balance, liquid column manometer, digital pressure gauge, mechanical pressure gaugeJCSS-calibrated pressure standard device JCSS calibration labPressure balancePressure standard device calibrated by national standard JCSS calibration labPrimary interferometric standard manometer (liquid column manometer)Primary pressure standard device group (pressure balance)National standard for pressure AIST

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