ESTABLISHMENT OF THAILAND PRESSURE STANDARD FROM 1.5 kPa TO 500 Mpa

Abstract

This paper describes the method used to characterize the zero-pressure effective area (A0) and pressure distortion coefficient () of 200MPa-CCPG oil piston-cylinder unit (PCU) in order to realize the national pressure scale from 1.5 kPa to 500 MPa. The A0 was determined by cross-floating method from a set of primary gas pressure standard, while the H-W method was used for calculating . A set of three oil PCUs was maintained as a primary pressure standard and used for scaling up and down pressure to determine  for the other PCUs. The relative standard uncertainty of 200MPa-CCPG pressure standard is 3.010 -5 .

The Measurement Method of a Piston Fall Rate

“…The most commonly employed solution for sensor displacement positioning involves placing the measuring device in a manner that enables measurements along the axis of the measuring piston rotation above the primary weight [10,11]. This approach ensures that imperfections in the fabrication of the weights utilised at subsequent pressure measurement points have no impact on the measurements -wobble is minimised.…”

“…Fall rate characteristic indicates range [3] and construction of piston-cylinder assembly, and is used to verify the results obtained from calculations using analytical mathematical methods [5]. This parameter is inseparably correlated with the flow of the medium transmitting pressure in the gap between the piston and the cylinder of the measu-ring assembly [9,10]. Proper determination of piston fall rate makes cross-float calibration more precise and repeatable but is also crucial for determining effective cross-sectional area using other methods [7,8].…”