A Glimpse of National Standards for Hydrulic Pressure Measurements

263-268The use, importance and significance of accurate, precise and reliable pressure measurements are considered the fundamental need in various fields of modern science and technology by scientists, engineers and metrologists. The accurate, precise and reliable pressure measurements have several diversified applications in power plants; manufacturing and engineering of chemicals; manufacturing and development of pharmaceuticals and drugs; exploration and transportation of oils, natural gases and petro-chemicals; aviation; automation engineering and research and development of materials. The idea of pressure and pressure measurement started with the wonderful experiment of famous scientist. Toricelli, during renaissance of modern science. He was the first person, in 1644, who used mercury column to measure atmospheric pressure. So many inventions were carried out thereafter in the field of pressure measurements. Among these inventions, the use of liquid column manometer could be made possible only around atmospheric pressure. The invention of pressure balance by Galy-Gazalat in 1846 is an important development to measure pressure more than the atmospheric pressure. The modern pressure balances can be used for accurate, precise and reliable pressure measurements from atmospheric pressure to several GPa. The internationally accepted method of cross-floating of pressure balances is used to characterize pressure balances. Present paper describes the physical principle used in the pressure balances, types of pressure balances and the major precautions to be taken during use of pressure balances. Since last two decades, Pressure and Vacuum Standards Group of National Physical Laboratory, New Delhi is actively engaged in the research and developmental activities in pressure metrology, establishment, development, maintenance and upgradation of pressure standards. The present paper highlights the glimpse of the national hydraulic pressure standards established and maintained at National Physical Laboratory, New Delhi. The international, bilateral and mutual in-house laboratory traceability of these national standards is also described