Calibration chain of the BNM-LNE from 10−4 Pa to 10 kPa

Abstract

Since 1992, the Bureau National de Metrologie-Laboratoire National d'Essais (BNM-LNE) has been working on the calibration of differential pressure transducers using gas-operated twin balances. Improvements in the pressure balances themselves, in environmental conditions and in measurement methods have optimized the calibration of capacitance diaphragm gauges (CDGs). A number of instruments have been compared in both differential and absolute modes to establish the pressure scale between 0.1 Pa and 10 kPa. The pressure range 0.1 mPa to 10 Pa was covered by spinning rotor gauges (SRGs) calibrated by comparison with the CDGs over the three higher decades. The linearity of the SRGs was checked by the dynamic-expansion method. Both CDGs and SRGs demonstrated a high level of repeatability. Stability over time can vary greatly between instruments, but is predictable under laboratory conditions. The input pressure is also predictable from the output signal. The paper describes calibration methods, performance and estimation of uncertainty in order to establish an effective calibration chain for both differential and absolute pressure measurements.