Metrology

Metrology is defined by the International Bureau of Weights and Measures (BIPM) as "the science of measurement, embracing Both experiment and theoretical determinations at any level of uncertainty in any field of Science and Technology."
Metrology is a very broad field and may be divided into three subfields:
•Scientific or fundamental metrology concerns the establishment of measurement units, unit systems, the development of new measurement methods, realisation of measurement standards and the transfer of traceability from these standards to users in society.
•Applied or industrial metrology concerns the application of measurement science to manufacturing and other processes and their use in society, ensuring the suitability of measurement instruments, their calibration and quality control of measurements.
•Legal metrology concerns regulatory requirements of measurements and measuring instruments for the protection of health, public safety, the environment, enabling taxation, protection of consumers and fair trade.
A core concept in metrology is (metrological) traceability, defined as "the property of the result of a measurement or the value of a standard whereby it can be related to stated references, usually national or international standards, through an unbroken chain of comparisons, all having stated uncertainties." The level of traceability establishes the level of comparability of the measurement: whether the result of a measurement can be compared to the previous one, a measurement result a year ago, or to the result of a measurement performed anywhere else in the world.
Traceability is most often obtained by calibration, establishing the relation between the indication of a measuring instrument and the value of a measurement standard. These standards are usually coordinated by national laboratories: National Institute of Standards and Technology (USA), National Physical Laboratory, UK, etc.
An integral part of establishing traceability is evaluation of measurement uncertainty.
Industry-specific metrology standards
In addition to standards created by national and international standards organizations, many large and small industrial companies also define metrology standards and procedures to meet their particular needs for technically and economically competitive manufacturing. These standards and procedures, while drawing in part upon the national and international standards, also address the issues of what specific instrument technology will be used to measure each quantity, how often each quantity will be measured, and which definition of each quantity will be used as the basis for accomplishing the process control that their manufacturing and product specifications require. Industrial metrology standarts include dynamic control plans, also known as “dimensional control plans”, or “DCPs”, for their products.
In industrial metrology, several issues beyond accuracy constrain the usability of metrology methods. These include 1. The speed with which measurements can be accomplished on parts or surfaces in the process of manufacturing, which must match the TAKT Time of the production line. 2. The completeness with which the manufactured part can be measured such as described in High-definition metrology. 3. The ability of the measurement mechanism to operate reliably in a manufacturing plant environment considering temperature, vibration, dust, and a host of other potential hostile factors, 4. The ability of the measurement results, as they are presented, to be assimilated by the manufacturing operators or automation in time to effectively control the manufacturing process variables, and 5. The total financial cost of measuring each part.