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Testing the Laboratories
One of the most important activities for accreditation bodies and the laboratories that they accredit is participation in Proficiency Testing (PT). International Accreditation Service (IAS)-accredited testing and calibration laboratories are required to have quality control procedures for monitoring the validity of the tests and calibrations that they conduct. There are a number of ways for laboratories to measure the quality of their results, including the use of certified reference materials, participation in inter-laboratory comparisons or PT, replication of tests or calibrations, and retesting or recalibration of retained items.
One of the most effective quality control tools used by laboratories is participation in PT, whereby a test sample (in the case of testing laboratories) or a measuring instrument (in the case of calibration laboratories) is circulated among several laboratories, tested or calibrated under a specified standard, and the results for the several laboratories compared to one another. These PT exercises are sometimes performed with the participation of a few local laboratories but, frequently, on an international scale, with dozens of laboratories from a number of economies worldwide.
Currently, IAS calibration laboratories are participating in such an international PT program on behalf of the Asia Pacific Laboratory Accreditation Cooperation (APLAC). APLAC is a regional “apex body” that oversees accreditation bodies in the Asia-Pacific region. Several APLAC-recognized accreditation bodies, including IAS, nominate laboratories that they have accredited to participate in PT programs that measure their proficiency in reproducing calibration results of several laboratories calibrating a single instrument. In this particular PT program, the instrument (often called an artifact by metrologists) being circulated is typically used for measuring DC current. The sponsoring organization is the Department of Standards Malaysia (DSM), Ministry of Science, Technology and Innovation.
Once the instrument is circulated to the laboratories and the PT results are reported by all participants, DSM will undertake a comprehensive statistical analysis of the results and compile the results into a report that will be provided to each accreditation body so that they can determine the relative performances of their nominated laboratories. Laboratories whose results fall outside the allowable standard deviations will be notified and required to determine the reasons for their unacceptable performance. Often retesting or recalibration is required to determine if a laboratory has taken effective remedial action to achieve the proper results. In extreme cases, a laboratory may have that particular type of test or calibration removed from its scope of accreditation.
In today’s global economy, it is vitally important for the purchaser, the regulator and the public to know that laboratories across the globe are competent to perform their tasks. A prerequisite for trade on equal terms is that any product, accepted in one economy, must also be free to circulate in other economies without having to undergo extensive retesting regardless of whether the product falls wholly or partly under a regulatory scheme. IAS accreditation criteria require regular participation of all of its accredited laboratories in PT programs, and IAS closely monitors the results. We also encourage laboratories to utilize other quality control tools to ensure the accuracy of their tests and calibrations.
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A Digital Multimeter (DMM) Proficiency Testing artifact currently being circulated to IAS-accredited calibration laboratories for an International Proficiency Testing Program on electrical calibration. |