The National Bureau of Standards primary high-vacuum standard

Abstract

The theory, design, operating procedures, and estimated errors are discussed for an orifice-flow-type pressure standard currently in use at the National Bureau of Standards. This standard is used to define pressures between 10−7 and 10−1 Pa. Including the uncertainty of the flowmeter, the estimated total uncertainty varies from 2.6% at the highest pressures, to 1.4% at midrange, and 8.2% at the lowest pressures. Representative calibration results are presented for four different types of hot-cathode ionization gauges.