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Improvement of the Calibration Process for Class E1 Weights Using an Adaptive Subdivision Method

Authors:
Adriana Valcu

Keywords: Subdivision method; automatic comparator; efficiency of design.

Abstract:
Taking into account the amount and variety of measurements involved in scientific, industrial and legal activities that need traceability to the national mass standards of each country, it can be considered that mass standards calibration is one of the most important activities of the National Metrology Institutes (NMIs). For the determination of the conventional mass, in the calibration of weights of the highest accuracy classes, the subdivision method and its variants are widely used. For the NMIs, it is very important to demonstrate and maintain their capability of applying with good results such methods. In this respect, a calibration procedure for the determination of conventional mass, called “adaptive subdivision method” was developed in the Mass Laboratory of the Romanian National Institute of Metrology, which can lead to an improvement of CMCs (Calibration and Measurement Capabilities, approved and published in the BIPM database). According to the International Recommendation OIML R 111, the weights of nominal values greater than 1 g may have a cylindrical shape with a lifting knob. Considering this kind of shape and the use of an automatic comparator, with the maximum capacity of 1 kg, the diameter of the weighing pan is too small for placing a group of weights in the range of (500…100) g; therefore, the usual subdivision method can not be applied for the calibration of weights. The “adaptive subdivision method”, presented in this paper, allows the cylindrical weights with a lifting knob, having nominal values of (500…100) g, to be calibrated using an automatic comparator (which is not equipped with weight support plates). The method can be used for class E1 weights, where the highest accuracy is required. In this case, the resulting calibration uncertainty for the unknown weights is better than that usually obtained for E1 masses, being at the level of reference standards.

Pages: 51 to 56

Copyright: Copyright (c) IARIA, 2012

Publication date: July 22, 2012

Published in: conference

ISSN: 2308-4146

ISBN: 978-1-61208-219-6

Location: Nice, France

Dates: from July 22, 2012 to July 27, 2012