An Intercomparison Between NPL (India) and NIST (USA) Pressure Standards in the Hydraulic Pressure Region up to 26 MPa

National Institute of Standards and Technology, Gaithersburg, MD 20899-0001 Results are presented of an intercomparison of pressure measurements between the National Physical Laboratory (NPL), India, and the National Institute of Standards and Technology (NIST), USA, using piston gauge pressure standards over the range 6 MPa to 26 MPa. The intercomparison, using the NPL piston gauge pressure standard, with a nominal effective area of 8.4X 10"' m^ and the NIST piston gauge pressure standard, with a nominal effective area of 2.0X 10"' m^ was carried out at the NPL. The intercomparison data obtained show a relative difference of 1 X 10"'' in the zeropressure effective area (Ao) of the NPL standard as obtained by the NIST standard. At 6 MPa the relative difference in effective areas is 3.5 XIO"'; at the full scale pressure of 26 MPa, the relative difference is 12X10"*. These differences are in excellent agreement with the statements of uncertainty of the respective standards as obtained from the primary standards of these two laboratories.