Vukan Ogrizović

Participation of Accredited Laboratories in Proficiency Testing Schemes and Interlaboratory Comparisons

This paper presents the elements of metrology laboratory accreditation for calibration in the scope of calibration E-05 Dimensions, and calibration for the subject: the distance and angle measures. During the accreditation, but also in its maintenance, calibration laboratories must prove their competence. Each laboratory must have the quality management procedures for monitoring the validity of the calibrations performed. This monitoring shall be planned and reviewed through: internal quality control, participation in the interlaboratory comparisons or proficiency testing schemes, repeated calibrations using the same or different methods, re-calibration of the saved samples and correlation of results for different characteristics of the sample. According to the ISO/IEC 17025:2005 standard, competence is proved by participating in interlaboratory comparisons or participation in Proficiency testing (PT) schemes. This paper aims to stimulate discussion and debate about ways of proving competence of calibration laboratories. We believe that, in the interpretation of ISO/IEC 17025, the laboratory can demonstrate competence by participating in any activity, PT schemes or interlaboratory comparisons, and they are equal to this need. The procedure and the results of the interlaboratory comparisons between two accredited laboratories will be described.

Effects of Low Temperatures in the Line of Sight of Digital Levels

AbstractDigital levels are high-precision instruments that use bar-code rods and sensitive charged-coupled device (CCD) linear sensors. To determine the height difference, it is necessary to bring the line of sight to the horizontal position. Horizontality of the line of sight is achieved by the compensator. Technical characteristics of the level are checked within the calibration. Level calibration was performed in an accredited laboratory of the University of Belgrade, Faculty of Civil Engineering. However, between two calibrations, the level was used in a variety of conditions and was exposed to different environmental conditions. To check the performance of the entire system (i.e., level, tripod, and rods), an experiment was conducted to calculate calibration curves of the line of sight of three sets of equipment that include three digital levels. The experiment was carried out in cold storage with the temperature ranging from +10°C to –15°C. The results of the conducted experiment are part of this pa...