Measurement and unit dissemination procedures as elements of a chain of metrological traceability of measurement results: comparative analysis and classification

The article addresses the ambiguity and diversity of requirements provided in regulatory documents and imposed on measurement and unit dissemination procedures comprising the chain of metrological traceability. A unified approach to the study of these procedures based on their classification is justified. Different types of procedures are analyzed: primary reference measurement procedures, reference measurement procedures, calibration procedures, verification procedures, end-user measurement procedures, and measurement procedures. Requirements for the development, study, and approval of the described procedures are considered. The article proposes a classification of procedures according to their place in the chain of metrological traceability, the type of metrological characteristics to be determined, and their application in the sphere of state control. The performed analysis of regulatory documents is summarized in a table describing the main requirements for the development and approval of measurement and unit dissemination procedures. The author considers requirements established for such conformity assessment of measurement and unit dissemination procedures as method certification, validation, and verification. The definitions and scope of application of conformity assessment procedures for measurement and unit dissemination procedures are presented. An analysis of requirements for the conformity assessment of procedures yielded a block diagram that can be used by laboratories to unambiguously select a conformity assessment procedure for approval of the required measurement or unit dissemination procedure, specifically when preparing for accreditation for compliance with ISO/IEC 17025-2017 General Requirements for the Competence of Testing and Calibration Laboratories. The proposed diagram for selecting a conformity assessment procedure for a particular procedure eliminates the ambiguity of requirements specified in regulatory documents.