Define the quantity, its dispersion and its reference chain
- Measurand
Specify exactly which quantity is being measured on which object and under which conditions. An instrument reading alone is not a complete measurand definition.
- Measurement uncertainty
Uncertainty characterizes the dispersion attributed to the measurand. State its evaluation and coverage rather than calling it a guaranteed error bound.
- Repeatability / reproducibility
Repeatability uses closely matched conditions; reproducibility uses specified changed conditions. Report what remained fixed and what changed.
- CalibrationThis term
Calibration establishes a relationship under specified conditions with associated uncertainties. It is different from adjustment or an automatic pass decision.
- Metrological traceability
The result is linked to a stated reference through documented calibrations. Each stage contributes uncertainty to the complete chain.
A measurement starts with a defined measurand. Uncertainty, repeated observations and calibration relationships describe the result, while traceability follows a documented reference chain.
Conceptual measurement relationships without numerical uncertainty or a calibration claim. The necessary conditions, method and evaluation depend on the measurement task.