Intercomparison of vacuum standards of countries within the European community in the range 8×10−5 to 8×10−2 Pa.

Abstract
A comparison of the vacuum standard maintained by four laboratories within the European Community (Istituto di Metrologia ’’G Colonetti’’ Turin, Italy; Laboratoire de Metrologie, Leybold–Heraeus–Sogev, Valence, France; National Physical Labortory, Teddington, Great Britain and Physikalisch–Technische Bundesanstalt, Berlin, Federal Republic of Germany) has been made in the pressure range 8×10−5Pa to 8×10−2Pa using a JHP high pressure ionization gauge. Three gauges were circulated around the participating labortories, each laboratory carefully following a detailed procedure for the preparation and operation of the gauge so as to minimize random variations in the sensitivity coefficient of the gauge. The gauges were calibrated up to nine times at each pressure by all the laboratories, the measurements in each laboratory taking place over a period of three days. A statistical analysis has been performed which shows that the standard of each of the labortories does not differ from the weighted mean of all the standards by more than ±2%. The results also show that when the three JHP gauges were used in the carefully controlled manner described in this paper, the ionization gauge coefficient did not change from its initial value by more than ±1.7% over an 18 month period.

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