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.)−213−Synthesiology - English edition Vol.4 No.4 (2012) is characterized by its excellent long-term stability, the device itself is heavy and large, and for the client receiving the calibration service, transporting this bulky device to the calibration lab is troublesome. Also, the calibration at the calibration lab may take about two months at the longest, and since the standard device cannot be used during that time, extra standard device must be kept for backup, requiring significant amount of expenditure. Therefore, industry demanded some method where calibration could be done effectively at the same precision as the conventional method, without transporting the pressure balance.Recently, the property of the industrial digital pressure gauge improved significantly, and there is good prospect of maintaining stability during transportation and in environment change, as well as certain degree of long-term stability. Therefore, we attempted to incorporate and utilize the industrial digital pressure gauge into the standard system. Normally, the digital pressure gauge is transported to the user’s site after being calibrated using the standard device at the calibration lab. Therefore, if the displayed value of the digital pressure gauge after being transported is sufficiently stable, the user will be able to maintain the calibration value that is traceable to the national standard at the same precision as before, without having to transport the heavy and large pressure balance to the calibration lab. This will ensure high efficiency of the calibration work.To promote the use of digital pressure gauge in the standard system, the necessary conditions are: the stability of the calibration value is sufficiently maintained even when the industrial digital pressure gauge is transported anywhere in Japan, and sufficient stability is maintained until the next calibration is conducted. AIST embarked on the research to determine whether the industrial digital pressure gauge had such properties. 2.2 International demandWith the globalization of economy, production, and trade, there is rising interest in the conformity of the measurement results by various measuring equipment among different countries[1][2]. For example, at Narita and Haneda Airports, there is an increase in international business such as the maintenance of the aircrafts of foreign companies by the maintenance shops of the Japanese airline companies. Several aircraft accidents occurred in the US in the 1990s, and the US government revised the Federal Aviation Law to maintain the safety of the US citizens, and the requirements for maintaining the US-owned aircrafts demanded that the measuring devices such as the pressure gauges to be traceable to the national standard of the National Institute of Standards and Technology (NIST), the American national metrology institute. The inspectors of the Federal Aviation Administration (FAA) would conduct regular on-site inspection of the maintenance shops. The demand of the US government was applied not only to the American airline companies but also to the foreign maintenance companies that maintained the US-owned aircrafts. Japan Airlines and All Nippon Airways had to make almost all the measuring devices in their maintenance shops traceable to NIST. This became an international issue, since most of the measuring devices used at the maintenance shops of the Japanese airline companies were made in Japan, and were traceable to AIST (at that time, the laboratory for former Agency of Industrial Science and Technology). The Japanese government stated that the Japanese national standard was proven to be equivalent to the American standard, and the devices traceable to the Japanese national standard should be allowed. This claim was accepted as an individual case.This issue spread to the airline companies around the world. With the background of such an issue, the Mutual Recognition Arrangement (MRA) of the Comité International des Poids et Mesures (CIPM) under the Convention du Mètre was established, to mutually recognize the equivalence of the national standards owned by the national metrology institutes around the world[3]. Figure 1 shows the framework of the international mutual recognition of the metrological standards.In this framework, the technological requirement for mutual recognition was the actual comparison of the national standards among the countries (international comparison). The results of the international comparisons and the calibration and measurement capabilities recognized for participating institutes are registered in the Appendix B and C of the international MRA. This can be viewed on the Key Comparison Database (http://kcdb.bipm.fr/) of the Bureau International des Poids et Mesures (BIPM). The level of the national standard owned by each country can be known from this technological information.As the Japanese metrology institute, AIST aims to establish and provide the national standard for pressure and to organize the traceability system of pressure measurement in Japan. By participating actively in the international Fig. 1 Framework of the international mutual recognition for metrological standard Globalized worldPeople, company of foreign countryFree trade without barriersJapanese people, companyMutual Recognition Arrangements for Laboratory AccreditationMutual Recognition Arrangement, Metre ConventionUsers of society, industryUsers of society, industryCalibration lab for pressure gaugeNational metrology institutesCalibration lab for pressure gaugeAISTMetrological traceability of foreign countriesMetrological traceability of Japan

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