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Accurate and precise measurement of physical parameters plays a vital role in improving the quality of any industrial product and to make it globally competitive. It is therefore essential for industrialists and metrologiest to keep abreast with the dynamic changes occurring in the measurement science in order to increase and maintain their profit margin and also to venture into a new business and entrepreneurship. The globalization of today’s industrial scenario and rapid development in miniaturization of components size, has led to the challenge of developing precise technical systems for accurate measurements of physical quantities like current, dimension, force, hardness, pressure etc. in nano and micro level. National Metrological Institutes are entrusted with the task and responsibility of realizing these parameters by establishing primary standards, as traceability is a key factor in measurements for universal acceptance of any product. Force is an important physical quantity to be realized more accurately to meet the growing need among the several industries such as mechanical, automobile, aviation etc. To best of our knowledge, National Physical Laboratory, India is the first NMI to design and develop a dead weight system for realizing force in the range of 1N to 10 N, as there has been a great demand in the recent past to realize small forces. The machine mainly comprises of calibrated dead weights and a loading hanger to realize the desired force steps in the 1N to 10N range. The deflection and stress distribution studies on the loading frame were carried out and found to be well within the accepted limits of deformation, confirming good mechanical stability of the loading frame. The salient feature of the machine is that it has a rigid vertical frame, which supports several horizontal plates on which the dead weights and loading frame rest under normal conditions without changing its orientations. In order to load and unload the dead weights to and from the loading hanger with a minimum vibration and oscillation, a pneumatic system has been used with an arrangement such that any weight can be loaded or unloaded from or to the weight stack irrespective of its position. The machine is automated through a window-based menu driven software enabling the operator to select a predetermined duration time between two subsequent measurements and a waiting time after the full load and at unloaded position before the starting of next cycle. The software has a built in facility to incorporate the environmental conditions and to evaluate the uncertainty of measurement as per the GUM document and to carry out the classification as per the written international standards ISO 376-2004. The metrological characterization of the as developed dead weight machine was carried out using load cells of capacities 2N, 5N and 10N having a 0.5 class accuracy to their maximum capacities. It is observed form the measurement results that the repeatability and reproducibility of the machine is better than 40 ppm and 60 ppm respectively. |
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