Establishing a Continuous Chain of Traceability for Pressure Measurements up to 40 MPa

Abstract:An Ultrasonic Interferometer Manometer (UIM) has been in use as the primary pressure standard at the National Physical Laboratory in India (NPLI) for absolute and gauge modes up to 130 kPa since 1982. However, the primary pneumatic pressure standard in gauge mode up to 6 MPa was based on the performance of controlled clearance Piston Gauges (CCPG). The uncertainty of measurements in UIM and CCPG were of great concern in establishing the primary pneumatic pressure scale of NPLI. To bridge the gap between the high vacuum, both in absolute and gauge modes, pneumatic pressure and hydraulic pressure up to 1 GPa, a conscientious attempt has been made to establish a uniform scale in the entire pressure range from 1 × 10−4 to 1 × 109 Pa that utilizes the UIM as the primary pressure standard. This paper presents the results of this entire systematic exercise up to a pressure of 40 MPa, in terms of the characterization of the piston gauges by the method of cross floating in the overlapping pressure ranges,...