ČSN EN ISO/IEC 17043 - Posuzování shody – Všeobecné požadavky na zkoušení způsobilosti

3.15 metrological traceability

property of ameasurement result whereby the result can be related to areference through adocumented unbroken chain of calibrations, each contributing to the measurement uncertainty

NOTE 1 For this definition, a“reference” can be adefinition of ameasurement unit through its practical realization, or ameasurement procedure including the measurement unit for anon-ordinal quantity, or ameasurement standard.

NOTE 2 Metrological traceability requires an established calibration hierarchy.

NOTE 3 Specification of the reference must include the time at which this reference was used in establishing the calibration hierarchy, along with any other relevant metrological information about the reference, such as when the first calibration in the calibration hierarchy was performed.

NOTE 4 For measurements with more than one input quantity in the measurement model, each of the input quantity values should itself be metrologically traceable and the calibration hierarchy involved may form abranched structure or anetwork. The effort involved in establishing metrological traceability for each input quantity value should be commensurate with its relative contribution to the measurement result.

NOTE 5 Metrological traceability of ameasurement result does not ensure that the measurement uncertainty is adequate for agiven purpose or that there is an absence of mistakes.

NOTE 6 A comparison between two measurement standards may be viewed as acalibration if the comparison is used to check and, if necessary, correct the quantity value and measurement uncertainty attributed to one of the measurement standards.

NOTE 7 The ILAC1) considers the elements for confirming metrological traceability to be an unbroken metrological traceability chain to an international measurement standard or anational measurement standard, adocumented measurement uncertainty, adocumented measurement procedure, accredited technical competence, metrological traceability to the SI, and calibration intervals (see ILAC P-10:2002).

NOTE 8 The abbreviated term “traceability” is sometimes used to mean “metrological traceability” as well as other concepts, such as “sample traceability” or “document traceability” or “instrument traceability” or “material traceability”, where the history (“trace”) of an item is meant. Therefore, the full term of “metrological traceability” is preferred if there is any risk of confusion.

[ISO/IEC Guide 99:2007, definition 2.41]

3.16 measurement uncertainty uncertainty of measurement uncertainty

non-negative parameter characterizing the dispersion of the quantity values being attributed to ameasurand, based on the information used

NOTE 1 Measurement uncertainty includes components arising from systematic effects, such as components associated with corrections and the assigned quantity values of measurement standards, as well as the definitional uncertainty. Sometimes estimated systematic effects are not corrected for but, instead, associated measurement uncertainty components are incorporated.

NOTE 2 The parameter may be, for example, astandard deviation called standard measurement uncertainty (or aspecified multiple of it), or the half-width of an interval, having astated coverage probability.

NOTE 3 Measurement uncertainty comprises, in general, many components. Some of these may be evaluated by Type A evaluation of measurement uncertainty from the statistical distribution of the quantity values from series of measurements and can be characterized by standard deviations. The other components, which may be evaluated by Type Bevaluation of measurement uncertainty, can also be characterized by standard deviations, evaluated from probability density functions based on experience or other information.