Intercomparison of the effective areas of a pneumatic piston gauge determined by different techniques

Abstract

A variety of primary measurement techniques is now available for the measurement of pressure to 1 MPa and above. To ascertain the systematic uncertainty, if any, which exists in the measured pressure using the individual techniques, it is best to perform direct intercomparisons of primary instruments, However, when direct intercomparison is not possible, the next best alternative is to use a highly stable, reproducible transfer artifact such as a simple piston gauge. Such intercomparisons are described here, utilizing a piston gauge calibrated by a mercury manometer (with 0.1 MPa full-scale pressure), four large diameter 'dimensional' piston gauges from two different manufacturen (all with 1 MPa fullscale pressure), and a controlled clearance piston gauge (with 7 MPa full-scale pressure). The area ratio derived from dimensional measuremenk on two of the large diameter gauges, when compared with the ratio obtained from measuremenk traceable to a manometer, agrees within 1 part per million (ppm). For one of the large diameter piston gauges, t h e area value obtained from the manometer agrees within 3 ppm with its dimensional area, and within 10 ppm with the value obtained by its direct calibration against the controlled clearance piston gauge.

A primary dead-weight tester for pressures (0.05-1.0) MPa

“…The type B uncertainties were added together algebraically because these could be correlated. This area compares very favorably with the area obtained from dimensions measured by the NIST Precision Engineering Division in 1989, (1007.926 ± 0.011) mm 2 , @ 20 °C [ 7 , 8 ].…”

“…Jain et al derived the pressure coefficients for both piston and cylinder for this gage using elasticity theory and the thick-wall formula [ 7 ]. (In that report the gage is referred to as NIST-9.)…”

“…The Pressure and Vacuum Group at NIST has recently acquired new dimensional measurements of high quality from Physikalisch Technische Bundesanstalt (PTB) [ 5 , 6 ] that were taken from a piston gage with a history going back about 12 years [ 7 , 8 ]. The new measurements have yielded substantially reduced uncertainties for the effective area compared with the previous determinations.…”

Primary pressure standards based on dimensionally characterized piston/cylinder assemblies

“…Within this band, temperatures were measured to ±0.01˚C and were corrected to 20.00˚C using a nominal thermal expansion coefficient. The measured data were compiled by Jain et al [1] and they estimated the total relative standard (k = 1) uncertainty in effective area of about 10 × 10 −6 . About 10 years later in 1999 one of the gauges (PG 39) was sent to PTB and dimensioned by its state-of-the-art facility described briefly in section 2.2.…”

“…The Pressure and Vacuum Group at the National Institute of Standards and Technology (NIST) has acquired two piston/cylinder assemblies (known within NIST as PG 38 and PG 39) and has established a history of both of them going back 15 years [1]. The two gauges are in effect twins with relatively large diameters and can, as a result of calibrations of their effective area with a NIST ultrasonic interferometer manometer (UIM), be confidently used with relatively low uncertainties over the pressure range 0.05 MPa to 1 MPa.…”