Traceability will always refer to a calibration chain provided by NIST or, if applicable, by the customer. The description of a chain refers to the points of interconnection or relationship between them. The chain may have characters, links, and nodes along with other labels. For example, a lab may have a chain of reference measurements, sources, and transfer of materials, or model interconnections between parts of the system. In this example, each characterization of the chain is an uncertain event which could be either an alpha or a beta quality milestone.
Uncertainty is the least documented and supported source of data variability in scientific applications. Traceability of measurement results is the preferred method of evaluating a data service for quality assurance. NIST provides traceability to the national standard realization of the International System of Units (SI) of measurement units. Traceability is an ordered chain of calibrations, in which each calibration link is documented, maintained, and evaluated. Each link in the traceability chain is characterized by an uncertainty and quality assessment.
For maximum traceability, the order of the chain is important. The realizations of the measurement units of the International System of Units (SI) of measurement units form the sequence of the traceability chain. This sequence is given in Table 5-23 of the reference standard of measurement realization of SI. Where appropriate, NIST recommends the related national standard realization of the International System of Units (SI) of measurement units. Where longer detail is needed, NIST can provide an advisoryon selecting a representative reference realization of the measurement units of the International System of Units (SI) of measurement units.
In order to evaluate a data service for quality assurance, NIST strongly recommends that the customer provide traceability to the NIST measurement system. If no link in the traceability chain is more precisely specified than the national standard realization of the International System of Units (SI), NIST will measure the interconnection with the link specified by the customer. 7211a4ac4a