Primary pressure standards in the atmospheric pressure range are often established using mercury manometers. Less frequently, controlled-clearance dead-weight testers in which one component (normally the piston) has been dimensionally measured have also been used. Recent advances in technology on two fronts i) the fabrication of large-diameter pistons and cylinders with good geometry; and ii) the ability to measure the dimensions of these components, have allowed some dead-weight testers at NIST to approach total relative uncertainties (2ς) in dimensionally-derived effective areas near 5 ppm. This paper descibes a single piston/cylinderassembly (NIST-PG201WC/WC) that serves as both a primary gage in which both piston and cylinder are measured dimensionally and a controlled-clearance primary gage (employing the Heydemann-Welch method). Thus it allows some previous assumptions about the modeling of dead-weight testers to be checked. For the gage described in this paper the effective areas obtained from the two analyses differ by 4 to 7 ppm over the pressure range 35 kPa to 175 k)a. Some implications of these results will be discussed.
Citation: Journal of Research (NIST JRES) -
Volume: 108 No. 1
NIST Pub Series: Journal of Research (NIST JRES)
Pub Type: NIST Pubs
dead-weight tester, piston gage, piston/cylinder assembly, pressure measurement, primary pressure standards