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Unformatted text preview: ty of the expansion coefficient (u(α)). The contribution uT, due to the uncertain knowledge of the temperature and the coefficient of linear thermal expansion, can be calculated by (5) The extended uncertainty Uy of each measured feature is calculated from these standard uncertainties as
2 2 U y = k p ⋅ u kal + u 2 + u ws + b prz (6) Mostly a significant systematic deviation b between the indicated values pi of the CMM and the calibrated value xkal of the working standard can be observed. If this systematic deviation b cannot be corrected, it must be added to the combined standard uncertainty. b = p − x kal (7) 130 A. Weckenmann, S. Beetz and J. Lorz This extended uncertainty Uy is calculated by the multiplication of the associated combined standard uncertainties with an extension factor. The extension factor is selected concerning to the distribution of the values (probability density distribution), which is assigned to the result y that the interval
I y = [ y −U y ; y +U y ] (8) covers a probability of P ≥ 95 %. The extended uncertainty is defined as half of the interval. 3.3. Characteristic for a successful interim check Periodical interim checks build th...
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- Spring '10
- The Land