Can a Pressure Standard be Based on Capacitance Measurements?

Published

March 1, 1998

Author(s)

Michael R. Moldover

Abstract

We consider the feasibility of basing a pressure standard on measurements of the dielectric constant [epsilon] and the thermodynamic temperature T of helium near )[degrees]C. The pressure P of the helium would be calculated using the fundamental constants, quantum mechanics, and statistical mechanics. At present, the relative standard uncertainty of the pressure u_r(P) would exceed 20x10^-6, the relative uncertainty of the value of the molar polarizability of helium A_{[epsilon] calculated ab initio. If the relativistic corrections to A}d[epsilon] were calculated as accurately the classical value is now known, a capacitance-based pressure standard might attain u_r(P)-6 for pressures near 1 Mpa, a result of considerable interest for pressure metrology. One obtains P by eliminating the density from the virial expansions for P and [epsilon]-1. If [epsilon]-1 were measured with a very stable, 0.5 pF toroidal cross capacitor, the small capacitance and the small values of [epsilon]-1 require state-of-the-art capacitance measurements.

Citation

Journal of Research (NIST JRES) -

Volume

103 No. 2

NIST Pub Series

Journal of Research (NIST JRES)

Pub Type

NIST Pubs

Keywords

ab initio calculations, cross capacitor, dielectric constant, helium, molar polarizability, polarizability, pressure standard, toroidal cross capacitor

Citation

Moldover, M. (1998), Can a Pressure Standard be Based on Capacitance Measurements?, Journal of Research (NIST JRES), National Institute of Standards and Technology, Gaithersburg, MD (Accessed October 10, 2025)