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Explore the process of calibrating weights using weighing designs and orthogonal methods, ensuring traceability and high accuracy. Learn how to maintain and disseminate the value of kilograms effectively.
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Dissemination of Mass Standards from the National PrototypebyThomas Mautjana
Presentation overview • Introduction • Method description • Traceability • Conclusion
Introduction • Kg is the only SI unit that is still an artefact • Our mandate is to maintain and disseminate the value of the kilogram
How do we disseminate the value of kg? • Weighing design is used to calibrate a set of weights using one reference standard • Subdivision and multiplication method • Calibrate in decades :D1 500, 200, 200*,100 • D2 50, 20, 20*,10 • D3 5, 2, 2*, 1 • etc D 6
Method description • To determine the values of all the unknown weights the normal equations would have to be orthogonal (i.e.withoutvariances) • To ensure orthogonality some of the equations may be omitted and some used more than once • Reference standard should be the defining (Head) weight
What about weights > 1kg • Define:(10) = M =10 u • u = (1) • thus (10) = 10(1)
Method: Advantages and Disadvantages • Advantages: • Less use of reference weights • Use check weights • Produces no variances or co-variances • Lead to higher accuracies • Disadvantage: • Placing several weights on a pan
Traceability Copy 56 E1 set of Transfer Standards E1 Working Standards 1kgTransfer Standards Customer Standards E2 Working Standards
Conclusion • Orthogonal system produces no variances or co- variances • The most accurate method with self check • Customer standards are compared against the working standards and never and never will be compared against the national standard.
