normal
A standard is a metrological reference object , a reference material or a precise measuring device that is used to calibrate other measuring devices. Standards form a calibration hierarchy, within which the accuracy inevitably decreases downwards. At the top of the calibration hierarchy are mostly national or international standards that are also primary standards . Primary standards are those standards that meet the highest requirements. This means the fundamental realization of a unit according to the valid international definition with the lowest possible uncertainty according to the current state of the art. In legal metrology arenational or international standards legally binding bases for the corresponding physical quantity.
This structure ensures that the units of the international system of units (SI) are uniformly available worldwide and that compliance with legal requirements in commercial transactions ( calibration law ) is guaranteed.
If normals are often used in one place, they are also used here hierarchically. Working standards that are routinely used are then regularly calibrated by a reference standard . If necessary, this also takes place via intermediate stages, the normals of which are then normals of a higher (second, third) order . This measuring equipment monitoring is used for quality assurance . Reference or company standards must also be traced back to the national standards. Calibration services and the services of metrological institutes serve this purpose . Here too, working and reference standards are generally used again, which at the highest level are also secondary or primary standards.
Normal can be:
- Measuring standards , also known as etalon,
- Measuring devices ,
- Measuring systems or
- Reference material
and are intended to define, embody, preserve or reproduce the respective unit (or one or more values of magnitude).
Examples
- Gauge blocks as length standards
- Resistances as electrical resistance standards
- Output signal of a cesium atomic clock or hydrogen mason as a time standard
- Teach thread
- Mass standards as measuring standards , depending on the accuracy e.g. B. made of cast iron, brass or corrosion-resistant steel with different nominal values or made of platinum-iridium as 1 kg standards
