Metrology

A measuring instrument is a device for measuring a physical quantity.

Observational error (or measurement error) is the difference between a measured value of quantity and its true value.

A transducer is a device that converts one form of energy to another.

A spirometer is an apparatus for measuring the volume of air inspired and expired by the lungs.

The International System of Units (French: Système international d'unités, SI) is the modern form of the metric system, and is the most widely used system of measurement.

The kilogram or kilogramme (SI unit symbol: kg) is the base unit of mass in the International System of Units (SI) (the Metric system) and is defined as being equal to the mass of the International Prototype of the Kilogram (IPK, also known as "Le Grand K" or "Big K").

Level of measurement or scale of measure is a classification that describes the nature of information within the numbers assigned to variables.

Reproducibility is the ability of an entire experiment or study to be duplicated, either by the same researcher or by someone else working independently.

Engineering tolerance is the permissible limit or limits of variation in: 1.

Measurement is the assignment of a number to a characteristic of an object or event, which can be compared with other objects or events.

(For a more accessible and less technical introduction to this topic, see Introduction to the metric system.) The metric system is an internationally agreed decimal system of measurement.

Calibration in measurement technology and metrology is the comparison of measurement values delivered by a device under test with those of a calibration standard of known accuracy.

Many techniques have been developed for the measurement of pressure and vacuum.

The International Committee for Weights and Measures (abbreviated CIPM from the French Comité international des poids et mesures) consists of eighteen persons from Member States of the Metre Convention (Convention du Mètre) appointed by the General Conference on Weights and Measures (CGPM) whose principal task is to ensure world-wide uniformity in units of measurement by direct action or by submitting proposals to the CGPM.

Surface metrology is the measurement of small-scale features on surfaces, and is a branch of metrology.

Sphericity is a measure of how spherical (round) an object is.

A monoisotopic element is one of 26 chemical elements which have only a single stable isotope (nuclide).

A mononuclidic element is 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).

A conventional electrical unit (or conventional unit where there is no risk of ambiguity) is a unit of measurement in the field of electricity which is based on the so-called "conventional values" of the Josephson constant and the von Klitzing constant agreed by the International Committee for Weights and Measures (CIPM) in 1988.