The METAS static expansion system was built in 2004 and has been extensively characterised during the last two years. The system consists of four expansion stages allowing the generation of calculable pressures ranging from 5·10-6 Pa up to 2000 Pa. Uncertainty calculation yields a relative uncertainty of 0.001 (k=2) for the volumetric ratio of the expansion stage. The relative uncertainty on the pressure obtained after expansion is 0.003 above 10 Pa, it is still 0.01 at 2·10-4 Pa. Measurement of the accommodation coefficient of two SRG from 10-5 Pa up to 0.1 Pa has shown no significant deviation of the accommodation coefficient over the full range of measurement and over a period of time of 18 months.
3rd Conference on Pressure Measurement (together with 20th TC3 Conference on Measurement of Force, Mass and Torque & 1st TC22 Conference on Vibration Measurement)
