International relations

Reducing technical barriers to trade

With international trade agreements now demanding demonstrated equivalence between the measurement standards and accreditation systems of buyer and seller nations, metrology has become vital to the regulation of trade and in the resolution of trade disputes. This has led to the creation of metrology-related cooperations supporting regional and international trade agreements, including:

MSS is a Member of SIM and an Associate Member of APMP. It also plays an essential role in the Standards Council of Canada's membership in APLAC and ILAC.

MSS is active in these organizations and in approximately 150 international committees under the auspices of global bodies such as the Comité International des Poids et Mesures (CIPM). A key element in these activities is the international comparison of measurement standards and calibration services.

MSS is also a partner in MetroTrade. This is a project, partly funded by the European Commission, that is studying ways to remove existing and future impediments to international trade caused by lack of knowledge of the degree of equivalence of national measurement capability, absence of a framework for the mutual acceptance of calibration certificates, and de facto requirements to repeat traceable calibrations.

International comparisons

The reliability of the international measurement system depends on continued effort by each National Metrology Institute (NMI) to base its measurements and measurement uncertainties on universally accepted units, usually those of the SI, and to compare its measurements with those of other NMIs to establish their mutual equivalence. MSS, as Canada's NMI, participates regularly in measurement comparisons with other NMIs. In many cases these are multilateral comparisons coordinated by the Bureau International des Poids et Mesures (BIPM) and other bodies such as SIM or NORAMET, but bilateral comparisons are also undertaken.

The purpose of these comparisons is to ensure that realizations of the SI units by participating NMIs are equivalent within known uncertainties, thus creating a uniform global metrology system. The participation of MSS enables increased competitiveness of Canadian industry within the global market.

In order to extend and fully document the practice of comparisons and declarations of equivalence, NMIs throughout the world have signed a Mutual Recognition Arrangement (MRA) under the auspices of the CIPM. The MRA provides for formal mutual recognition of national measurement standards and calibration capabilities including measurement capabilities related to certified reference materials. It is expected to become the basis for wider agreements relating to trade and commerce signed by the competent authorities in each country or region. The MRA was signed in October 1999 by the Director General of MSS alongside the directors of NMIs in 37 other countries. It now has a total of 51 signatories (49 NMIs and two international organizations).

Under the MRA, MSS scientists participate in an increased number of measurement comparisons with other NMIs. Each inter-NMI comparison requires several years to plan, implement, document and establish equivalence. MSS participated in the planning or implementation of some 35 such comparisons in pursuit of the MRA aims during 2001-2002. Full details are in Appendix B the BIPM key comparison database (KCDB). In addition, MSS was involved in the planning or implementation of some 8 comparisons under the auspices of SIM. MSS is also involved in the extensive and on-going international review process that takes place following the completion of the comparisons to determine which calibration and measurement capabilities can be recognized for inclusion in Appendix C of the KCDB and the parallel SIM database, known as the ICDB. The review process looks at the results of the comparisons, at quality systems, and at other appropriate evidence.

In addition to participation in comparisons and analysis of capabilities, MSS provides the NORAMET representative on the SIM Technical Committee and participates in all relevant consultative committees of the CIPM. These activities have enabled us to protect and enhance Canada's interests by direct involvement at the highest level. This affects virtually all of Canadian industry involved in the export of products to countries with which agreements have been reached, as well as customers of products imported from these countries.

Accreditation systems

In addition to the CIPM MRA, Canada is signatory to two important international MRAs related to laboratory accreditation, those of APLAC (Asia-Pacific Laboratory Accreditation Cooperation) and ILAC (International Laboratory Accreditation Cooperation). As a result of these Arrangements, all signatory countries now recognize calibration certificates issued by CLAS-assessed, SCC-accredited laboratories. Likewise, CLAS and SCC recognize laboratories accredited by the other MRA countries. Canadian participation in these international and regional arrangements provides the infrastructure needed for Canadian industries to have their goods and services accepted in a client country without the need for re-calibration.


The concept of traceability to a National Metrology Institute (NMI) is fundamental to a unified system of metrology. Traceability is defined as the property of the result of a measurement or the value of a standard whereby it can be related to stated references, usually national or international standards, through an unbroken chain of comparisons all having stated uncertainties. In most cases, the ultimate reference for a measurement result is the definition of the appropriate unit in the International System of Units (SI). However, the stated reference is usually an NMI, such as NRC or NIST, or, more precisely, a national standard maintained by an NMI. This is an appropriate and practical way of stating traceability and reflects the usual chain of measurement comparisons (calibrations) that exist in a country. For more details on traceability please see the BIPM website.

Thus, "traceable to NRC" or "traceable to NIST" are phrases that are often used in regulatory requirements, in contracts, or even in advertising. These phrases indicate that a measurement is related to a particular primary realization of an SI definition. However, the purpose of the SI is to provide a practical system of units that can be adopted by all countries. It is intended to be reliable and consistent over the long term and to lead to measurements that are comparable throughout the world. Thus the idea of traceability to an NMI is really a shorthand notation for traceability to the SI through an NMI. Although many NMIs have independent realizations of the SI units, the intent is always the same - to realize the SI definition (or, in some cases, an agreed representation such as the Josephson volt). The uncertainty with which the definition is realized is a component of the uncertainty of an NMI calibration and, thus, measurements in different NMIs should all agree with each other within their quoted uncertainties. With the increasing globalization of trade, this concept is becoming more and more important and is superseding the idea that each country's primary standards should be thought of as separate independent sources of traceability. Thus, MSS documents and calibration reports now refer to "traceability to the SI through NRC" rather than "traceability to NRC".

MSS participates in a large number of international comparisons. The purpose of these comparisons is to demonstrate that realizations of the SI units by MSS are equivalent within known uncertainties to those of other NMIs, thus ensuring that traceability to the SI through MSS is equivalent to traceability through other NMIs.

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