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

Since 1992, the Bureau National de Metrologie-Laboratoire National d'Essais (BNM-LNE) has been working on the calibration of differential pressure tra nsducers using gas-operated twin balances. Improvements in the pressure bal ances themselves, in environmental conditions and in measurement methods ha ve optimized the calibration of capacitance diaphragm gauges (CDGs). A numb er of instruments have been compared in both differential and absolute mode s 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 (S RGs) 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 t ime can vary greatly between instruments, but is predictable under laborato ry conditions. The input pressure is also predictable from the output signa l. The paper describes calibration methods, performance and estimation of unce rtainty in order to establish an effective calibration chain for both diffe rential and absolute pressure measurements.