Bilateral key comparison CCM.P-K3.1 for absolute pressure measurements from 3 × 10⁻⁶ Pa to 9 × 10⁻⁴ Pa

Abstract

This report describes the bilateral key-comparison CCM.P-K3.1 between the National Institute of Standards and Technology (NIST) and Physikalisch-Technische Bundesanstalt (PTB) for absolute pressure in the range of 3 × 10-6 Pa to 9 × 10-4 Pa. This comparison was a follower to the CCM.P-K3 comparison. Two ionization gauges and two spinning rotor gauges (SRGs) were used as the transfer standards for the comparison. The SRGs were used to compare the standards at a pressure of 9 × 10-4 Pa and to normalize the ionization gauge readings. The two ionization gauges were used to compare the standards in the pressure range of 3 × 10-6 Pa to 3 × 10-4 Pa. Both laboratories used dynamic expansion chambers as standards in the comparison. The two labs showed excellent agreement to each other and to the CCM.P-K3 key comparison reference value (KCRV) over the entire range.

Review Article: Recommended practice for calibrating vacuum gauges of the ionization type

“…Break-out boxes are often used in calibrations by National Metrology Institutes (NMIs), and have been used in international intercomparisons among NMIs. 52,53 During intercomparisons, calibration factors for the same gauge determined by various NMIs are compared, and so the electrode potentials and emission current help to assess whether the gauge was in the same condition at each NMI. However, we do not generally recommend the use of break-out boxes because these must be custom constructed, the user may be exposed to high voltages, and the information obtained may not be that useful to many users.…”