Demonstrating Traceability to  National and International Standards
NIST Policy & Guidance on Demonstrating TraceabilityNIST Mutual Recognition Agreements (MRAs)American Association for Laboratory Accreditation (A2LA)A2LA Traceability PolicySI - NIST Policy on Use of SI UnitsReturn to Home Page

 

Last Revised: 30 September 2011

Contact us by e-mail at:  webmaster@dosimetryresources.com

© 2007 —  2011 Dosimetry Resources International, inc.

All rights reserved -

may not be reproduced without the written permission of the copyright owner

 
Text Box: The American Association for Laboratory Accreditation (A2LA) defines traceability as the property of a measurement result whereby the result can be related to a reference through a documented unbroken chain of calibrations, each contributing to the measurement uncertainty. The purpose of requiring traceability is to ensure that measurements are accurate representations of the specific quantity subject to measurement, within the uncertainty of the measurement. Traceability is characterized by six essential elements: 1. An unbroken chain of comparisons: going back to stated references acceptable to the parties, usually a national or international standard; 2. Measurement uncertainty: the uncertainty of measurement for each step in the traceability chain must be calculated or estimated according to agreed methods and must be stated so that an overall uncertainty for the whole chain may be calculated or estimated; 3. Documentation: each step in the chain must be performed according to documented and generally acknowledged procedures; and the results must be recorded; 4. Competence: the laboratories or bodies performing one or more steps in the chain must supply evidence for their technical competence (e.g. by demonstrating that they are accredited); 5. Reference to SI units: the chain of comparisons must, where possible, end at primary standards for realization of the SI units; 6. Calibration intervals: calibrations must be repeated at appropriate intervals; the length in of these intervals will depend on a number of variables (e.g. uncertainty required, frequency of use, way of use, stability of equipment). Detailed requirements for demonstrating traceability of personnel radiation dosimetry processing systems may be found in applicable accreditation standards and manuals such as ISO-17025, NVLAP Handbook 150-4, DOELAP DOE 1095-2011Standard, IEC-1066 and similar.