Metrology

thumb|upright|Four measuring devices having metric calibrations Measurement is the quantification of attributes of an object or event, which can be used to compare with other objects or events. In other words, measurement is a process of determining how large or small a physical quantity is as compared to a basic reference quantity of the same kind. The scope and application of measurement are dependent on the context and discipline. In natural sciences and engineering, measurements do not apply to nominal properties of objects or events, which is consistent with the guidelines of the Internat

unit of mass defined as ¹⁄₁₂ of the mass of a carbon-12 atom

thumb|The National Institute of Standards and Technology|NIST-4 [[Kibble balance, which is used to measure weight via electric current and voltage. With this instrument, the measurement of mass is no longer dependent on a defined mass standard and is instead dependent on natural physical constants.]] Metrology is the scientific study of measurement. It establishes a common understanding of units, crucial in linking human activities. Modern metrology has its roots in the French Revolution's political motivation to standardise units in France when a length standard taken from a natural source wa

coherent system of units using centimeter gram and second as base units

measures of observational error

1875 international treaty

In measurement technology and metrology, calibration is the comparison of measurement values delivered by a device under test with those of a calibration standard of known accuracy. Such a standard could be another measurement device of known accuracy, a device generating the quantity to be measured such as a voltage, a sound tone, or a physical artifact, such as a meter ruler.

permissible limit(s) of variation in an engineered component or system

realization of the definition of a given quantity used as reference

physical units of measurement based only on universal physical constants

thumb|upright=0.65|The hourglass is often used as a symbol representing the passage of time. thumb|Clocks; a watch-maker seated at his workbench Chronometry or horology () is the science studying the measurement of time and timekeeping. Chronometry enables the establishment of standard measurements of time, which have applications in a broad range of social and scientific areas. Horology usually refers specifically to the study of mechanical timekeeping devices, while chronometry is broader in scope, also including biological behaviours with respect to time (biochronometry), as well as the dat

meridian line running through the Paris Observatory in Paris, France

nuclides predating the Earth's formation (found on Earth)

method to measure temperature quantitatively

Repeatability or test–retest reliability is the closeness of the agreement between the results of successive measurements of the same measure, when carried out under the same conditions of measurement. In other words, the measurements are taken by a single person or instrument on the same item, under the same conditions, and in a short period of time. A less-than-perfect test–retest reliability causes test–retest variability. Such variability can be caused by, for example, intra-individual variability and inter-observer variability. A measurement may be said to be repeatable when this variatio

device for measuring the physical geometrical characteristics of an object

physical quantity of interest in chemistry and electrodynamics

one of the 22 chemical elements that is found naturally on Earth essentially as a single nuclide (which may, or may not, be a stable nuclide)

method for a test in science or engineering; definitive procedure that produces a test result; technical operation or procedure that consists of determination of characteristics of a given product,process or service according to a specified procedure

A scatterometer or diffusionmeter is a scientific instrument to measure the return of a beam of light or radar waves scattered by diffusion in a medium such as air. Diffusionmeters using visible light are found in airports or along roads to measure horizontal visibility. Radar scatterometers use radio or microwaves to determine the normalized radar cross section (σ0, "sigma zero" or "sigma naught") of a surface. They are often mounted on weather satellites to find wind speed and direction, and are used in industries to analyze the roughness of surfaces.

thumb|Micrometer by Mitutoyo is a Japanese multinational corporation specializing in measuring instruments and metrological technology, headquartered at Takatsu-ku, Kawasaki, Kanagawa.

quantized unit of magnetic flux threading a loop in a bulk superconductor

thumb|NIST Next-Generation Nanometrology research. Nanometrology is a subfield of metrology, concerned with the science of measurement at the nanoscale level. Nanometrology has a crucial role in order to produce nanomaterials and devices with a high degree of accuracy and reliability in nanomanufacturing.

one of 26 chemical elements which have only a single stable isotope (nuclide)

study of measurement systems

physical artifact that formerly defined the kilogram unit of mass

techniques for measuring distance

thumb|300px|Schematic representation of difference in grain shape. Two parameters are shown: sphericity (vertical) and Roundness (geology)|rounding (horizontal).

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component of measurement error that is caused by imperfection in the measuring instrument being used

instruments that accurately measure large objects

bya or b.y.a. is an abbreviation for "billion years ago". It is commonly used as a unit of time to denote length of time before the present in 109 years. This initialism is often used in the sciences of astronomy, geology, and paleontology.

Roundness is the measure of how closely the shape of an object approaches that of a mathematically perfect circle. Roundness applies in two dimensions, such as the cross sectional circles along a cylindrical object such as a shaft or a cylindrical roller for a bearing. In geometric dimensioning and tolerancing, control of a cylinder can also include its fidelity to the longitudinal axis, yielding cylindricity. The analogue of roundness in three dimensions (that is, for spheres) is sphericity.

a precision measurement tool that projects a magnified silhouette of a part onto a screen, allowing for accurate inspection of dimensions and shapes

system of codes for unambiguously representing measurement units

Qualimetry is a scientific discipline which concerns itself with the methods and problems of quantification of the quality of any object: things or processes, whether natural or man-made, products of labour or nature, whether living or inanimate, etc.

Metrologia is a bimonthly journal dealing with the scientific aspects of metrology. It has been running since 1965 and has been published by the International Bureau of Weights and Measures since 1991. Since 2003 the journal has been published by IOP Publishing on behalf of the bureau. The journal covers the fundamentals of measurements, in particular those dealing with the seven base units of the International System of Units (metre, kilogram, second, ampere, kelvin, candela, mole) or proposals to replace them.