Connect a result to a reference through documented calibrations.
Key knowledge
A traceable measurement result is connected to a stated reference by an unbroken documented calibration chain, with uncertainty contributions accounted for at each step.
Conditions and scope
Traceability is a property of a measurement result, not merely an instrument label.
Traceability alone does not guarantee uncertainty small enough for the intended use.
Sources · 4
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
VIM 2.41 and NIST TN2156 policy 3.2, items 1 and 5.
2026-10-10 · Definition, result-specific chain and fitness-for-purpose limitation only; no actual result's traceability is certified here.
Foundational review
2026-10-10 · Fresh primary-source inspection of the complete compact record, including every statement, equation, quantity and material condition, followed by independent AI editorial review. This check does not certify all linked lessons or every passage of every cited publication.
Sources from other places
Agreement within this scope
A result is traceable through a documented calibration chain with uncertainty contributions.
Traceability belongs to the result and does not by itself guarantee suitable uncertainty or fitness for use.
Calibration establishes, under stated conditions, a relation between standard values with uncertainty and instrument indications with uncertainty. That relation is then used to obtain a measurement result from an indication.
Documented calibration relations are elements in a metrological traceability chain; this definition does not certify a chain.
A measurement standard realizes a specified quantity with a stated value and uncertainty for reference use. A primary standard is established by a primary procedure or convention; an organizational reference standard calibrates other standards, while a working standard routinely calibrates or verifies instruments.
Primary, secondary and working standards can form a documented calibration chain; a role name alone proves no result's traceability.
An isotope delta compares a specified sample isotope ratio with the same ratio in a stated reference. Equilibrium and kinetic fractionation can change isotope partitioning between substances; mixing also changes measured ratios. A delta is a relative ratio difference, not an absolute isotope abundance or a unique process diagnosis.
Optical transition standards on the CIPM list are secondary representations of the second; their improved instrument performance does not itself change the SI definition. As checked 10 October 2026, the BIPM roadmap describes a conditional 2030 decision and competing single-transition versus weighted-optical-frequency options, contingent on criteria and consensus.
Optical ratio and transfer measurements require a documented reference chain.
For linear observations z=Aθ+ε with known positive-definite covariance Σ and full-column-rank A, generalized least squares yields θ̂=(AᵀΣ⁻¹A)⁻¹AᵀΣ⁻¹z. Shared reference, environmental and transfer errors create off-diagonal covariance; they do not average away as independent scatter. Fix an identifiable reference/gauge and model synchronization separately.
A shared reference transfers both scale information and uncertainty.
Reference-material value assignments have distinct status. A certificate must identify the property, matrix, intended use, uncertainty, traceability, validity and handling. NIST distinguishes certified values from other information and research-grade development material; a candidate material or supplier specification cannot be substituted for a validated certified measurand.
Certified property values carry a specific reference chain.
A reference quantity value is used as a basis for comparison with values of quantities of the same kind. A conventional quantity value is attributed by agreement for a given purpose. A reference can be a conventional value or another specified value with associated uncertainty. Agreement does not make a value an exact property of nature, and finite detail in a measurand definition can allow more than one value consistent with that definition.
The two records describe related physical or metrological models or distinctions; the present claim does not require every hypothesis or result in the linked record.