Metrology

Metrology is the science of measurement, including the realization and dissemination of units, the comparison of standards, and the evaluation of measurement uncertainty.

International System of Units: The internationally agreed system of measurement units, built around seven base units and defined constants. Metrology uses the SI to make measurements and standards internationally comparable.
Josephson effect: A quantum phenomenon in which a current flows between two superconductors separated by a thin barrier. Josephson voltage standards realize electrical voltage through a relation to fundamental constants.
Dimensional metrology: The measurement of geometric dimensions, form, and position of physical objects. It applies traceable length standards to manufacturing tolerances and precision engineering.
Metric system: A decimal system of measurement units that developed in France during the late eighteenth century. The metric system established the foundation from which the modern SI developed.
Quantum metrology: The use of quantum phenomena and resources to improve measurement precision or establish measurement standards. It may enable new standards and measurement capabilities, while practical gains depend on noise and implementation.
Measurement uncertainty: A parameter describing the dispersion of values reasonably attributable to a measured quantity. Metrology reports uncertainty to show the limits of confidence in measurement results.
Quantum Hall effect: A quantized Hall resistance observed in two-dimensional electron systems at low temperatures and strong magnetic fields. Its quantized resistance supplies a reproducible electrical reference for metrology.
Chemical metrology: The science of measurement in chemistry, including traceable measurements of composition and concentration. It enables reliable comparisons of chemical measurements across laboratories and jurisdictions.
Metre Convention: A 1875 international treaty establishing cooperation on measurement standards and the institutions that maintain them. It created the framework for coordinating national metrology across borders.
Quantum sensor: A sensor that uses quantum states or effects to detect physical quantities. Quantum sensors raise questions about calibration, robustness, and uncertainty outside controlled laboratories.

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