Knowledge
Metrology Dictionary
The complete VIM vocabulary — all numbered concepts of JCGM 200:2012 as faithful paraphrases with clause citations — plus clearly labeled practice terms from the GUM, ILAC, ISO and NIST guidance.
Primary measurement standard
A standard established using a primary reference measurement procedure, or created as an artifact chosen by convention — not calibrated against another standard for the same quantity.
VIM (JCGM 200:2012) 5.4 · Standards & Units