Final Report on Key Comparison APMP.M.P-K7 in hydraulic gauge pressure from 10 MPa to 100 MPa

Abstract

This report describes the results of a key comparison of hydraulic high-pressure standards at 16 national metrology institutes (NMIs: NMIJ/AIST, NPLI, CSIR-NML, NIS, KRISS, SCL, SPRING, NMIA, VMI, NML-SIRIM, KIM-LIPI, NSCL, PTB, NIMT, CMS/ITRI and NIM) was carried out during the period October 2002 to July 2004 within the framework of the Asia-Pacific Metrology Programme (APMP) in order to determine their degrees of equivalence at pressures in the range 10 MPa to 100 MPa for gauge mode. The pilot institute was the National Metrology Institute of Japan (NMIJ)/AIST. All participating institutes generally used hydraulic pressure balances as their pressure standards. High-precision pressure transducers were used as transfer standards. The sensing element of the transducer was a precision quartz crystal resonator. To ensure the reliability of the transfer standard, two pressure transducers were used on a transfer standard unit. Three nominally identical transfer packages were circulated independently to reduce the time required for the measurements. During this comparison, the three transfer standards were calibrated simultaneously at the pilot institute 11 times in total. From the calibration results, the behaviours of the transfer standards during the comparison period were well characterized and it was presented that the capabilities of the transfer standards to achieve this key comparison were sufficient. The degrees of equivalence of each national measurement standard were expressed quantitatively by two terms, deviations from the key comparison reference values and pair-wise differences of their deviations. The degrees of equivalence in this comparison were also transferred to the corresponding CCM key comparison, CCM.M.P-K7. The hydraulic pressure standards in the range 10 MPa to 100 MPa for gauge mode of the 16 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 the CCM, according to the provisions of the Mutual Recognition Arrangement (MRA).

Improvement of reliability in pressure measurements and international mutual recognition

“…Using the developed transfer device, several international comparisons were actually done [19]- [23] . Multiple digital pressure gauges were used simultaneously as the transfer devices, to increase the reliability by redundancy.…”

“…Through the execution period of the international comparison that normally takes over one year, the details of the long-term property changes of the digital pressure gauge was studied and the results were used to correct the calibration value. By these corrections, the lack of long-term stability of the transfer device was compensated, and sufficient comparative precision could be maintained [19]-[22] [24] .…”

“…As an example of use of the digital pressure gauge in international comparison, we describe the international comparison conducted from 2002 to 2004 to check the international equivalence of the national standard for hydraulic gauge pressure with pressure range from 10 MPa to 100 MPa (APMP.M.P-K7 [19] ). Figure 6 shows the transfer device used in that international comparison.…”

“…However, it was found in the evaluation that the change in each pressure was the linear function of the number of lapsed days. By correcting this and by using the average value of the calibration values obtained from the two digital pressure gauges that comprised the transfer device, ultimately, 5 × 10 −6 or less for the stability of each transfer device was obtained throughout the entire measurement period [19] . We were able to obtain sufficient comparative precision that could be used in the international comparison, by understanding the details of the property of the digital pressure gauge as the transfer device and conducting appropriate corrections.…”

Standardisation of pressure measurement using pressure balance as transfer standard

“…The NPL100MPN has also participated in several key comparison exercises, APMP.M.P. K7 [21], CCM P. K7 [22] and APMP-SIM.M.P. K7 [23].…”