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.)−221−Synthesiology - English edition Vol.4 No.4 (2012) measuring device into one body to enable the fully automatic pressure generation and measurement. To increase the reliability of the transfer device, multiple high-precision digital pressure gauges were installed in each transfer device. For the gas differential transfer device, the pressure gauge with silicon resonant sensor as the pressure sensor was used, and for the hydraulic pressure transfer device, the digital pressure gauge with crystal oscillator as the pressure sensor was employed. To compensate for the lack of long-term stability of the installed digital pressures gauges, the detailed preliminary studies were done for the properties such as the stability in environment change and during transportation as well as the short- and long-term stability.For Item (2), the program for conducting automatic calibration was created. Also, the remote calibration manuals for the personnel at the calibration lab and the supporting personnel at the client company were drafted.For Item (3), numerous demonstration experiments for remote calibration were done in Japan and abroad using the developed transfer device. Figure 10 shows an example of the demonstration experiment for the gas differential pressure. As shown in Fig. 10(a), the remote calibration experiment was done by sending the transfer device twice to Kofu, Yamanashi Prefecture and once to Chongqing, China, with AIST as the calibration lab. Figure 10(b) shows the results of calibration of the digital pressure gauge with full scale of 10 kPa and resolution of 10 mPa, and they are shown as the deviation from the calibration value obtained in ordinary carry-in calibration. The maximum value of the deviation of each measured pressure was within 20 mPa, and this was sufficiently small at relative 2 × 10−6 or less of the full scale of calibrated pressure gauge. From this result, it was shown that the result equivalent to the carry-in calibration could be obtained by remote calibration, and that sufficient stability including the stability in environment change and during transportation could be obtained for the transfer device and calibrated digital pressure gauge.The newly developed remote calibration technology was confirmed to be reliable from the results of the demonstration experiment, and it is currently established as the calibration service at AIST. The current uncertainties (confidence level of about 95 %) for the remote calibration service are 100 mPa or 0.01 % or less for gas differential pressure in the range from 10 Pa to 10 kPa, and 0.01 % or less for hydraulic pressure in the range from 10 MPa to 100 MPa.7 Ripple effect to society and industry, and future issues7.1 Increasing the reliability of pressure measurement at industrial sitesCurrently, AIST establishes the national standards for the nine-digit pressure range from 1 Pa to 1 GPa, and responds to the various calibration requests from society and industry. For the maintenance and advancement of the group of pressure standard devices that comprise the national standard for pressure, the use of digital pressure gauge is promoted, as described in subchapter 6.1. Currently, we are developing the full automatic calibration technology for multiple pressure balances using the digital pressure gauge. This is expected to enhance the advancement and efficiency of the group-managed national standard devices.For the main part of the calibration service currently conducted by AIST, the conformity assessment has been completed for ISO/IEC17025, which is the international standard that is the general requirement for the testing and calibration labs, as well as the technical assessment by the assessment personnel who are specialists invited from major overseas national metrology institutes. AIST’s ability for calibration and measurement are recognized by the rest of the world.The pressure standard provision to the industrial measuring sites and Japanese users is done mainly by the calibration labs for pressure accredited by the Japan Calibration Service Fig. 10 (a) Circulation route of the transfer device in the demonstration experiment for the remote calibration of gas differential pressure and (b) the results (the calibration value of the remote calibration was expressed as the deviation from the calibration value of carry-in calibration) (b)(a)Measurement dataDevice under calibrationTransfer deviceTransfer deviceKofuCalibration lab (AIST)ClientTsukubaChongqing-30-20-100102030100001000100101Pressure/PaDeviation from calibration value of carry-in calibration/mPaAIST, carry-in calibration, Feb 2007Kofu, remote calibration, Jul 2007Chongqing, China, remote calibration, Sep 2007Kofu, remote calibration, Nov 2007

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