This article is about the science of measurement. It establishes a common understanding of units, crucial in linking human activities. France, when a length standard taken from a metrology and quality control book pdf source was proposed.
1795, establishing a set of standards for other types of measurements. The effects of metrology on trade and economy are some of the easiest-observed societal impacts. To facilitate fair trade, there must be an agreed-upon system of measurement. It establishes a common understanding of units, crucial to human activity.
Trading manufactured goods, the ability to accurately diagnose illnesses, and ensuring consumer confidence during the purchase of goods and services all depend on confidence in the measurements made during these processes. Although fundamental metrology is formally undefined, it is considered the top level of scientific metrology which strives for the highest degree of accuracy. The BIPM maintains a database of the metrological calibration and measurement capabilities of institutes around the world. These institutes, whose activities are peer-reviewed, provide the fundamental reference points for metrological traceability. Applied, technical or industrial metrology is concerned with the application of measurement to manufacturing and other processes and their use in society, ensuring the suitability of measurement instruments, their calibration and quality control. Industrial metrology is important to a country’s economic and industrial development, and the condition of a country’s industrial-metrology program can indicate its economic status.
Legal metrology “concerns activities which result from statutory requirements and concern measurement, units of measurement, measuring instruments and methods of measurement and which are performed by competent bodies”. Such statutory requirements may arise from the need for protection of health, public safety, the environment, enabling taxation, protection of consumers and fair trade. The cubit was decreed to be the length of the Pharaoh’s forearm plus the width of his hand, and replica standards were given to builders. The success of a standardised length for the building of the pyramids is indicated by the lengths of their bases differing by no more than 0. Other civilizations produced generally accepted measurement standards, with Roman and Greek architecture based on distinct systems of measurement. The collapse of the empires and the Dark Ages which followed them lost much measurement knowledge and standardisation.
Although local systems of measurement were common, comparability was difficult since many local systems were incompatible. With a political motivation to harmonise units throughout France, a length standard based on a natural source was proposed. 1795, establishing standards for other types of measurements. Although the SI base units are technically independent, some definitions depend on those of other base units. All other SI units are derived from the seven base units.
The amount of substance of a system which contains as many elementary entities as there are atoms in 0. Since the base units are the reference points for all measurements taken in SI units, if the reference value changed all prior measurements would be incorrect. By defining base SI units with respect to physical constants, they are realisable with a higher level of precision and reproducibility. Standards are the fundamental reference for a system of weights and measures by realising, preserving, or reproducing a unit against which measuring devices can be compared.
A CRM provides direct traceability to the realisation of the unit of measure, and can be used for direct comparisons of other materials or to calibrate a measuring device. There are three levels of standards in the hierarchy of metrology: primary, secondary, and working standards. Secondary standards are calibrated with reference to a primary standard. The hierarchy preserves the quality of the higher standards.