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A. Mary Ness I. Salazar
EVALUATION OF INTERLABORATORY COMPARISONS ON PRESSURE MEASUREMENT IN THE PHILIPPINES OF 6 YEARS INTERVAL

This paper presents the evaluation of two intercomparisons on pressure measurement, six years apart using the same artefact. These intercomparisons aimed to provide local laboratories access to proficiency testing for their compliance with the ISO/IEC 17025 requirements. Improved awareness and commitment to quality of the participants and the enhanced competence of the pilot laboratory are a few of the enumerated factors instigating the increase in the number of participants as well as those obtaining satisfactory results. The PT schemes offered aim to sustain and continuously develop this service to support further progress in the calibration and measurement capabilities of local laboratories.

Louis-Jean Hollebecq
Β-RISK IN PROFICIENCY TESTING IN RELATION TO THE NUMBER OF PARTICIPANTS

The Monte Carlo method was applied to PT schemes to investigate their efficiency. Probabilities that the computed z values are over 3 while the true value is less than 2 and that the computed z values are less than 2 while the true values are over 3 are computed for a series of situations: number of participants from 5 to 30, various ratios of repeatability over reproducibility and number of test results per participant, introduction or not of outliers with k from 3 to 10. For each situation, the probabilities of detecting true outliers and to trigger false alerts are discussed.

I. Ljevaković-Musladin
UNCERTAINTY FROM SAMPLING IN FOOD MICROBIOLOGY

The aim of this study was to estimate uncertainty arising from the sampling of food for microbiological analysis. A balanced experimental design using the duplicate method was a method of choice for empirical estimation of uncertainty. Duplicate test portions were drawn from both test samples and analyzed in duplicate. This approach allowed the estimation of overall measurement uncertainty and its components; analytical uncertainty and sampling uncertainty. Classical ANOVA and Robust ANOVA were used for the calculation. Based on 12 sampling targets of minced meat, uncertainty from sampling was estimated as 0.10-0.11 log10 cfu/g for microbiological parameter aerobic colony count, while analytical uncertainty was 0.04 log10 cfu/g. Estimated uncertainties proved to be fit-for-purpose. Results showed that uncertainty from sampling is the major contributor to overall measurement uncertainty.

Bodan Velkovski, Marija Markovska, Zivko Kokolanski, Vladimir Dimchev, Dimitar Taskovski
EVALUATING THE UNCERTAINTY OF A VIRTUAL POWER QUALITY DISTURBANCE GENERATOR

This paper presents the metrological evaluation of a proposed virtual power quality (PQ) disturbance generator. The calibration and measurement uncertainty estimation procedures for the RMS voltage and frequency of the generator are explained in detail and the obtained results are presented and discussed. The results show that the measurement uncertainty of the PQ disturbance generator for all reference points is satisfactory, making it suitable for generation of PQ signals for research purposes, especially in the development, testing and improvement of PQ event classifiers.

Kiril Demerdziev, Vladimir Dimchev
ACTIVE POWER MEASUREMENT UNCERTAINTY BUDGET MODELLING IN CASE OF HARMONICALLY DISTORTED VOLTAGES AND CURRENTS

Harmonic distortion of electrical waveforms results in a need for instrumentation performance evaluation in non-sinusoidal conditions. This is especially challenging in case of power and/or energy measuring devices, because of their place in the regulated trade of electrical energy. The measurement uncertainty evaluation procedure commences with determination of influence factors, which are correlated to harmonic components’ magnitude and phase shift recording. For overall uncertainty budget modelling, a GUM based approach is implemented. The model validation and the uncertainty propagation, due to alteration of different signals’ parameters, is illustrated via real time measurements, conducted with high accuracy class measuring equipment.

C. Simões, A. S. Ribeiro, M. C. Almeida, D. Covas
UNCERTAINTY ANALYSIS OF AVERAGE FLOW DURATION CURVES USED IN HYDRPOWER PLANTS FEASABILITY STUDIES

This study applies a Monte Carlo method (MCM) to estimate the uncertainty related to the determination of the annual flow duration curve determined at a river weir, considering the dynamic behaviour of processes and the intrinsic uncertainty contributions to the raw data. The computation of the curve uses a time series of average daily flow data collected at a hydrometric station at an upstream river section. This curve was used for a hydropower plant feasibility study. Results show how model uncertainty can be estimated from the measurement uncertainty of raw data and mathematical formulation applied.

M. Aleksic, M. Bjelic, M. Dolinic
A COMPARATIVE ANALYSIS OF DIFFERENT METHODS OF SURFACE PLATES FLATNESS CALIBRATION

This paper describes a comparative overview of different methods of surface plates flatness calibration in the accredited Calibration Laboratory MAGAT Tech. A parallel analysis of methods, together with calculation of the measurement uncertainty, will be presented in detail in this paper. The conclusion of the paper refers to the authors position for the application of the most suitable calibration method of surface plates used in industry, taking into account the measurement uncertainty of calibration and the statement of conformity, in accordance with the level of risk and the requirements of the customer.

Omar-Jair Purata-Sifuentes, Luis-Eduardo Hernández-Balandrán, Mirna-Guadalupe Tornero-Navarro
ROLE OF THE MEASUREMENT UNCERTAINTY IN CONE PENETRATION TEST RESULTS OF LUBRICATING GREASE

The guard banding approach is tested to meet the NLGI grade of lubricating grease specifications. Different guard band formulae were tried to compare the customer and manufacturer risks during production release testing. The results show that the called risk management approach for guard banding offers the best results for the trade-off between the producer risk without compromising the targeted level of consumer risk for the particular case of symmetrical but high-preferred specifications limits.

Elvia-Andrea Purata-Funes, Omar-Jair Purata-Sifuentes, Luis-Armando Torres-Pérez, Ramón Navarrete-Reynoso
GUARD BANDING APPLIED IN THE LEGAL METROLOGY REQUIREMENTS OF WEIGHING INSTRUMENTS

The guard banding approach is tested to meet the legal requirements for NAWIs. Different guard band multipliers were tried to compare the customer and manufacturer risks when initial and subsequent verification or service inspection were done. The results show that the producer’s risk is always greater than the customer’s risk, no matter if the metrological control is for initial and subsequent verification or service inspection.

Haris Memić, Zijad Džemić, Jasmin Kevrić, Dejan Jokić
PREDICTION OF LIFE CYCLE OF NON-AUTOMATIC WEIGHING INSTRUMENT IN LEGAL METROLOGY

In this paper, the possibilities and important factors that can influence the prediction of the life time (life cycle) of a measuring instrument used in the field of legal metrology, which is found in everyday work and in different working conditions, are considered. Based on the measurement history and a large number of measurement results data, significant factors (history of measurements, different provider of services, measurement uncertainty and environmental conditions) that can influence the judgment of the life cycle of the measuring instrument were analysed. The presented results indicate the further research for development of a more efficient, faster and better system meant for consumer protection from inaccurate measurements.

Page 4 of 891 Results 31 - 40 of 8905