25 Years of Interlaboratory Comparisons among Accredited Calibration Laboratories in Europe - The Experience of PTB and DKD

摘要

Establishing and maintaining confidence in the correctness of measurement results of accredited calibration laboratories is an important matter for the transborder mutual acceptance of issued certificates. The organisation of interlaboratory comparisons is a powerful means for developing such confidence under two different aspects. Firstly, the measurement results of the participating laboratories, chosen as a representative sample of all accredited laboratories of the national calibration services involved, shall demonstrate their technical calibration capabilities. Secondly, the involved calibration services are challenged to demonstrate their organisational capabilities for keeping the calibration service system under control. Their response on having found improper results as well as their information to the other calibration services in the region are important actions. Apart from being used as a tool for the surveillance of accredited laboratories, interlaboratory comparisons were performed successfully on a national level to demonstrate the stability and reproducibility of newly developed measuring devices to be used as transfer standards and to intensify the technical cooperation between industrial calibration laboratories and the National Metrology Institute. For almost 25 years of its existence, the DKD (German Calibration Service) has been participating in many interlaboratory comparisons within the European co-operation of Accreditation (EA). The experience gained over the years is reported on in the following. In most cases all actions and reactions could be qualified to be adequate and promoting the mutual confidence in the laboratories and in the calibration systems. In a few cases some complaints arose which gave reason for further discussions.