IMEKO Event Proceedings

Page 810 of 851 Results 8091 - 8100 of 8504

Karina Chacur Schraml, Valmir Ruiz

The purpose of this study is to estimate the uncertainty contribution due to the diverter valve in the total uncertainty, concerning the calibration of flow meters in the water laboratory of the Center for Fluid Metrology.

Liron Anavy, Boris Katz

This article deals with interpolation methods, ways to determine which method is required and ways to check the results’ fitness.

Romuald Masnicki, Janusz Mindykowski

A traditional description of the measurement result obtained with the use of a definite measurement instrument is complemented by the information about its accuracy on the basis of technical specifications given by its producer or verified in checking and legalisation procedures. The paper presents the premises resulting from currently available technical possibilities, which show that it is purposeful to complement the set of functions realised in a microprocessor instrument with additional properties enabling the instrument user to access the information about the uncertainty of the measurement result. The configuration of the measurement instrument, which enables an access, apart from the measurement result, to the information about the uncertainty as the component of the result, is presented. The conditions referring to the set and programme configuration of the instrument, indispensable for the realisation of the proposed idea, are pointed out. The main ideas of the presented paper will be also found in the authors’ work.

Barbara De Santis, Marina Patriarca, Francesca Debegnach, Marzia De Giacomo, Emanuela Gregori, Carlo Brera
Uncertainty assessment for mycotoxins in food. The example of the metrological approach

Over the last ten years, the role on measurement uncertainty has been embraced in those sectors where, traditionally, metrology has strived to assert the concept and its applications. Mycotoxins analysis constitutes an example where not many reference guidance are available, thus experts are working to assess, verify and control uncertainty budget coming from the application of their methods. Possible approaches to be used are top down (metrological) or bottom up (holistic approach from the availability of reproducibility data). Examples on how these two approaches may be used in the mycotoxin field will be scrutinized. Moreover, the critical role of the measurement uncertainty in the compliance assessment and decision making in the context of official control will be taken into consideration.

Wukchul Joung, Kee Sool Gam, Inseok Yang, Yong-Gyoo Kim

Despite the importance of resistance bridges in thermometry, an accurate assessment of their uncertainty has not been investigated much. Among various uncertainty components, nonlinearity and ratio error have been of particular interest, and a Hamon-type resistance network known to be RBC (resistance bridge calibrator) is widely used to measure those uncertainties. However, due to finite temperature coefficients of base resistors in the RBC, the evaluated uncertainty of the resistance bridges under normal operating environment is in doubt. In this work, to accurately evaluate the uncertainty of the resistance thermometry bridge, an air medium thermostatted chamber was devised, and the nonlinearity and ratio error of a resistance bridge at KRISS (ASL F900) were assessed. Along with this, repeatability and AC quadrature/frequency dependence of the resistance bridge were evaluated and total combined uncertainty of the resistance bridge at KRISS was finally assessed.

Ozer, H., Oktay, Basegmez, H. I., Whitaker, T. B., Slate, A. B.
Uncertainty associated with sampling and effect of sampling plan in aflatoxin analysis of dried figs

Aflatoxin test procedure is a multi-stage process and generally consists of three steps; sampling, sample preparation and analytical steps. Because of the uncertainty associated with each step, the true aflatoxin concentration of a bulk dried fig lot can’t be determined with 100% certainty. The sources of error in the aflatoxin test procedure should be determined so that the errors can be effectively reduced.
Studies were developed to measure the variability and distribution among replicated sample aflatoxin test results taken from the same aflatoxin- contaminated lot of dried figs so that a model could be developed to evaluate the risk of misclassifying lots of aflatoxin sampling plan designs for dried figs.

Lampi, E., Boussias, S.
Uncertainty at very low analytical levels – The probabilistic approach

Chemical metrology is a specific field where the process in order to achieve a traceable and comparable results is difficult to be standardized. Moreover, a more holistic approach is required for the evaluation of their reliability. On the other hand, a continuous increasing number of contaminants are intended to be determined in foods and for a high percentage of them e.g. the more toxic, at very low quantification levels. At these low levels, close to detection, the classical way of GUM using statistical techniques for the determination of uncertainty, as the range of values that could reasonably attributed to the measurand, becomes weak.
Probabilities have been used for the determination of type B uncertainties. The probabilistic approach is regarded appropriate in order to determine the concentration level of the analyte and to estimate its uncertainty at the detection and quantification level of the method. More specifically Monte Carlo Simulation and Bayesians can be considered as useful approaches. Bayesians are very useful in case of detection methods where the measurement is not a deterministic procedure but it is based on the capability of the method to classify or identify the analyte from an indication which could lead to false positive or false negative observation.
In the present work, Bayesians are applied in order to estimate the value of the analyte and its uncertainty in the determination of food contaminants at very low levels as well as in identification techniques.

Isabel Cristina S. Fraga, Paulo Roberto G. Couto, Paulo Paschoal Borges, Bianca de Souza R. Marques, Wiler Batista da S. Junior, Carla de M. Ribeiro, Jéssica C. Lopes, Sidney Pereira Sobral, Júlio C. Dias, Valnei S. Cun

In 2007, the Chemical Metrology Division (Dquim) from National Institute of Metrology, Standardization and Industrial Quality - Inmetro, established the primary system of electrolytic conductivity (EC) measurement. The main use of this system is to provide reliability and traceability to the EC measurements in Brazil since its measurement is very important, mainly for determining the purity of water. In order to show comparability and capability in primary EC measurement, Inmetro has participated in the key-comparison organized by Consultative Committee for Amount of Substance (CCQM) called CCQM-K36.1 to measure the EC in two solutions: one with a nominal value of 0.5 S m-1 and the other, 5 mS m-1. This work aims to present a comparison among the values of the uncertainty results from primary EC measurement in the solution of 0.5 S m-1 obtained by using the methods of ISO GUM, Kragten and Monte Carlo simulation. In addition, this work will also present an evaluation of the uncertainty related to all relevant sources in the uncertainty budget for EC measurement by using the primary EC system from Inmetro. Moreover, this study intends to show the main points which should be focused on in order to improve the process of primary EC measurement, when needed.

Davor Zvizdic, Lovorka Grgec Bermanec, Georges Bonnier, Eliane Renaot, Tomislav Veliki

This paper presents a simplified model for the evaluation of the measurement uncertainty of pressure balance effective area calibrated by method of comparison which is being applied at Laboratory for Process Measurements (LPM). The methodology is applied for oiloperated industrial pressure balances in the gauge pressure range up to 60 MPa. The scope of the procedure is illustrated by calculation example.

Eduarda Filipe

The experimental design, active statistical tool generally used for the optimization of processes, can also be considered for the evaluation of sample(s) homogeneity. This tool may be applied to Metrology for the analysis of large amount of repeated measurements permitting the "mining" of the results and include this "time-dependent sources of variability" information at the uncertainty calculation.

Page 810 of 851 Results 8091 - 8100 of 8504