The ladder of standards and calibrations that ties a result to its reference, for example a shop micrometer checked with gauge blocks, which were compared with master blocks, which were measured by interferometry at a national lab against the SI metre. Each link adds uncertainty, so uncertainty only grows moving down the chain. One undocumented or lapsed link breaks traceability for every result below it.
Map out the traceability chain for the humidity probe, I want every cert from the NMI down to the floor.
Also heard as
- calibration chain
- chain
Related terms
Traceability
Proof that a result ties back to the SI or another stated reference, with every calibration in between on record.
Calibration hierarchy
The ranked levels of standards, from primary realizations down to working instruments, through which values flow.
Imported uncertainty
The uncertainty carried into a measurement from the calibration certificate of the reference standard used.
Primary standard
A standard that gets its value straight from the unit definition, not from calibration against another standard.
Working standard
A standard used routinely to calibrate instruments, itself checked against the lab's reference standard.