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Abstract and Manuscript Management System - Abstract Detail |
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| Speaker: | Wu Jian |
| Title: | A New Primary Vacuum Standard based on Continuous Expansion Method |
| Topic Group: | Pressure II |
| E-mail: | wu_jian@nmc.a-star.edu.sg |
| Co-Authors: | Chua Hock Ann (chua_hock_ann@nmc.a-star.edu.sg) |
| Abstract: |
Abstract:A primary vacuum standard based on the method of continuous expansion has been developed at the National Metrology Centre of Singapore. The standard, which is capable of defining vacuum levels between 1E-8 Pa and 1E-1 Pa, consists of two cylindrical ultra-high vacuum chambers, each having a volume of 23.8 l. The chambers are separated by a circular disc with a circular orifice nozzle in the center. To determine the effective conductance of this circular orifice under molecular flow, two methods: one based on analytical consideration and the other on Monte Carlo evaluation, were applied to determine the correction factors. A fully automatic flow meter operating in the range of 1.88 E-11 mol/s to 2.678E-6 mol/s was developed to generate gas flow with known flow rates into the vacuum chamber. A measurement comparison with the National Physical Laboratory, UK, was carried out to evaluate the performance of the system in the range of 9E-5 Pa to 9 E-3 Pa. Measured results of the two laboratories agreed to within 1.5% of the readings. Measurement principle, design, and evaluation of measurement uncertainties will be discussed in more details in the paper. Keywords: Vacuum, Primary Standard, Measurement Uncertainty. |
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