| Popis: |
The International System of Units (SI) of physical quantities is very important and necessary toolkit for any scientific development. The existing system adopted in 1960 by CGPM, France, is the globally well accepted, up-to-date, modern, coherent, having official status and even contemporary arrangement or form of the metric system starting with seven base units. It is almost dominant and globally accepted modern metric system of measurements used in science, engineering, technology, international trade and commerce. The system also embodied and agrees with limitless additional units, called derived units and special units, identified by special names and symbols which are always epitomized through seven base units. The SI is always envisioned to be an evolving system, wherein units, prefixes and definitions are created, modified and adapted as a result of international agreement arrived on the basis of advancement of measurement technologies and improvement in precision in measurements. As science evolves, advance technologies are developed which demand even more precise and accurate measurements. Due to advent of new technologies, the improvement in the accuracy of the products is carried out through development of new and improved measurement techniques, measurement standards and their definitions. Daily a number of precision measurements are performed which make our lives easier, comfortable, healthy and safer. In this chapter, authors have attempted to explain the historical aspects of metrology; international system of measurements, various international metrological organizations, for example, BIPM, NMIs, Metre Convention, MRA, etc. A brief overview of the importance and significance of the SI units; fundamental constants of nature (FCN) and their relevance in SI, historical aspects and evolution of SI units; redefinition of SI units in terms of FCN and current status and implication of redefined SI units, derived and other non-metric units, has also been presented. The whole contents are presented in a unique way to include scientific and analyzed data in tables, graphs, diagrams and flow charts to make the reading interesting for the readers. |
