Luciano Brunetti, Luca Oberto, Marco Sellone
REFERENCE VALUE IN HIGH FREQUENCY POWER COMPARISONS

According to the modern trend, the reference value of a measurement comparison among laboratories is established considering the contribution of all the participants appropriately. The main problem is deciding whether the data are consistent or they have to be discarded because of the evidence that the measured value is too different from the expected one. In this paper, the problem of the data rejection is analyzed for a specific comparison concerning microwave power measurements and a decision algorithm is presented.

P. P. Borges, I. C. Fraga, A. P. Ordine, H. C. Carnaval, B. S. Rossini, J. C. Dias
POTENTIOMETRIC TITRATION OF HYDROCHLORIC ACID DILUTE SOLUTION USING A METROLOGICAL APPROACH

Primary methods of measurement are essential in the realization of the SI units. In 1995, the CCQM (Comité Consultatif pour la Quantité de Matière) identified titrimetry as a primary method of measurement. Titrimetry is a method that has wide range of applications for amount of substance measurements and can be applied at primary level and at working level depending on the uncertainty values. The aim of this work is to present the results of potentiometric titration of a dilute solution of hydrochloric acid (HCl). The potentiometric titration method was carried out with the solution addition controlled gravimetrically. The results were accurate and HCl concentration of (0.010042 ± 0.000112) mol kg^-1, k = 2 for approximately 95% confidence level was obtained. The molality determination of HCl solution is a prerequisite for the use of a Harned cell, the primary method for the realization of pH measurement. The HCl solution is used in the pH primary system at Inmetro to obtain accurate value of the silver-silver chloride electrode potential. This standard potential is very important for the correct measurement of pH to certificate pH buffer.

Roman Tabisz
COMPUTER AIDED METROLOGICAL CONFIRMATION PROCESSES - CAMCP

The need for undertaking the actions, aimed at elaborating the uniform methodology of carrying out the processes of metrological confirmation, was justified. The significance of the processes, which guarantee credible measurement results and the undertaking of appropriate decisions in the industrial quality management systems and systems of human safety management and health protection, was emphasized. Essence of adequate realization of the processes of metrological confirmation in respect to recommendations of international standards and the determination of two components of measuring system accuracy i.e. measures of precision and trueness, was described. Conception of the creation of the CAMCP computer system, supporting the realization of the processes of metrological confirmation in the present industrial conditions, was presented. This conception can be successfully used in other fields also.

Marcos F. de Campos, Jailton C. Damasceno, Rogério Machado, Carlos A. Achete
UNCERTAINTY ESTIMATION OF LATTICE PARAMETERS MEASURED BY X-RAY DIFFRACTION

Abstract: The uncertainties in lattice parameters determination, for X-Ray Diffractometers with Bragg- Brentano geometry, were estimated according GUM recommendations using the Monte Carlo simulation approach. The analyzed specimen was a Corundum NIST 1976 SRM Standard. Misalignment of instrument (zero 2theta offset and peak position) is an important error source, and should be kept (2θ) < 0.015° to be able to perform lattice parameters measurements with an accuracy = 0.0001 Angstrons. Sample displacement is in general the main source of error, and the above mentioned misalignment of instrument (0.015°) only becomes dominant as error source if the sample displacement is very small (<10 µm). The analysis showed that sample absorption (Corundum) is negligible as error source, if compared with sample displacement and equipment misalignment. Other possible sources of systematic error are discussed.

Vanderléa de Souza, Janaína Marques R. Caixeiro, Renata M. H. Borges, Paulo R. Guimarães Couto, Rafael A . L. da Silva, Leandro R. Pedro, Thiago M. Fernandes
DETERMINATION OF THE EVAPORATION FACTOR OF ETHANOL AND ITS CONTRIBUTION TO THE MEASUREMENT UNCERTAINTY IN THE DEVELOPMENT OF A CERTIFIED REFERENCE MATERIAL

This work presents the determination of the evaporation factor of ethanol and the contribution of this source of uncertainty in the process of certifying a reference material composed of solutions of ethanol in water. For this purpose, an experiment involving three technicians was carried out, where each one of them performed measurements during two days. Since the certification process is based on the gravimetric preparation of solutions by two different methodologies: individual and batch, the evaporation experiments involved measurements that complied both methodologies.