Intercomparison of National Hydraulic Pressure Standards up to 500 MPa

In order to provide inputs for improving the quality of measurements, achieving objective evidences of the technical competence and to build-up and maintain mutual confidence of national hydraulic pressure standards, an extensive in-house laboratory intercomparison is carried out in a systematic manner. The present paper describes the summary of the results thus obtained in this in-house laboratory intercomparison exercise of eight numbers of national hydraulic pressure standards, designated as NPL28MPA, NPL100MPN, NPL100MPA, NPL140MPA, NPL200MPN, NPL280MPA, NPL500MPN, NPL500MPA. The intercomparison of these pressure standards is carried out using an internationally accepted method of cross-floating of pressure balances. The uncertainty in area and pressure measurements is computed as per ISO, WECC and EAL guidelines. The compatibility, uniformity and affirmation of results is re-established by comparing the values of zero pressure effective area (A 0) and distortion coefficient (Λ) with the values obtained during bilateral and international key comparisons sponsored by BIPM, CCM, APLAC, LNE (France) and NIST (USA). The metrological characteristics thus obtained establish a very good agreement within the limits of uncertainty budgets of bilateral and international key comparisons.