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Page 613 of 977 Results 6121 - 6130 of 9762

F. Adunka, A. Witt
MEASUREMENT UNCERTAINTY OF A TEST RIG FOR WATER METERS

The accuracy of test rigs for water and flow sensors of heat meters depends on several parameters of the device and the performance of the calibration. Therefore the expanded uncertainty of a new test rig of the BEV, the Austrian Metrological Service, was determined by investigating the relevant influences. This measuring device allows to control the flow rate in a very wide range from 6 l/h up to 170.000 l/h as well as the temperature from 8 °C up to 90 °C, in the pressurized case up to 130 °C, and the pressure up to 6 bar.
At first a theoretical analysis of uncertainty was performed in line with the „Guide to the expression of Uncertainty in Measurement” (ISO Guide) followed by experimental tests.The following contribution presents the basic ideas and the results of the investigations.

V. Zelený, V. Stejskal
THE MOST RECENT WAYS OF CMM CALIBRATION

The aim of modern calibration methods is to determine the total position uncertainty of a coordinate measuring machine (CMM) in the whole working range, but also to identify all 21 partial errors. These errors can be entered as correction factors in modern CMMs, thus reducing the total position uncertainty of the machine. New calibration artefacts are being developed and suitable positions are being looked for with the aim, among others, to shorten the calibration time.

K. M. Yu, J. C. Ryu, Y. P. Semenov, B. Litvinov, S. Haiming
HIGH RESISTANCE COMPARISON AMONG KRISS, VNIIM AND NIM

In a high resistance comparison among KRISS, VNIIM and NIM, the relative resistance values of measurement results agreed well within 2 ppm in 10 megohm and 5 ppm in 1 gigohm. Also, relative combined standard uncertainties of the three institutes for the values is not beyond 4 ppm in 10 megohm and 8 ppm in 1 gigohm.

A. J. Wallard
BRINGING PRECISE MEASUREMENT TO THE WORKPLACE

For many years the traditional way of calibrating standards at the highest level was for companies to bring their standards to a National Metrology Institute (NMI). ‘New’ technologies such as the Internet are now changing these long standing techniques as is the existence of commercial ‘quantum based’ standards of high quality. This places new obligations on NMIs to work in new ways and to develop new partnerships to transfer expertise to industrial users.

A. C. Vidal, I. Caminha, R. R. Machado
THE MANUFACTURE OF ROCKWELL HARDNESS STANDARD BLOCKS IN BRAZIL

In the present work, the heat treatments used during production of national Rockwell hardness standard blocks, in the ranges of 60-80 HRB, 85-100 HRB, 20-30 HRC, 35-55 HRC and 60-70 HRC as well as their resulting microstructures are presented. Two kinds of steels with different contents of carbon and a very low level of impurities were used in the manufacturing process of the blocks. The microstructural changes were studied by means of optical microscopy analyses. The hardness measurements were carried out in hardness tester machines belonging to the Brazilians institutions involved in the present study. Preliminary results suggest that the heat treatment parameters influence directly on the microstructural homogeneity and stability and consequently on the uniformity of hardness values.

A. Sostar, B. Acko
TRACEABILITY OF THREAD RING CALIBRATION ON A CO-ORDINATE MEASURING MACHINE

Thread rings are widely used for screw thread gauging. They can be calibrated on 1D measurement machines with ball probes, by using control thread plug gauges, or on three co-ordinate measurement machines (CMMs) by using special probes and software. The last method is used in our laboratory for calibrating rings from 5 to 300 mm. The calibration procedure based on this method was accredited by RvA which is EAL member and signatory or MRA. The basic problem by creating the procedure was traceability of the CMM measurement. Since the CMM is used as a calibration device in this case, simple periodical performance tests are not sufficient for assuring traceability at a certain level of uncertainty. Therefore, a special substitution method was involved. Reference standards in the substitution procedure are gauge rings, which are calibrated on 1D measurement instrument by using laser interferometer as the linear measurement system. Reference values are set by combination of gauge blocks. Basic approaches are presented in the paper.

I. Pušnik, J. Bojkovski, J. Drnovšek
CALIBRATION OF NON-CONTACT THERMOMETERS

In the paper a development of an accredited temperature calibration laboratory in the field of non-contact thermometry is presented. The laboratory was first accredited for calibration by comparison of contact thermometers and calibration baths and furnaces in the range from -55 °C to 1250 °C. It also became a holder of national standards for thermodynamic temperature thus providing the traceability of temperature in Slovenia. After a strong demand for calibration of non-contact thermometers was expressed by mostly export oriented industry in Slovenia, the laboratory has started a set of activities with an objective to establish a facility for calibration by comparison of radiance thermometers. These activities included besides a purchase of the equipment also an extensive training of experts, which have developed, written and implemented the procedures for evaluation and calibration of blackbody sources, and determined the best measurement capabilities with the existing equipment.

V. Mudronja, B. Runje, Z. Barsic
REPRODUCIBILITY OF MEASUREMENT RESULTS OF GAUGE BLOCKS OVER A PERIOD OF 15 YEARS

The paper gives a presentation of monitoring the results of measuring the gauge blocks length over a time period of fifteen years. The analysis has been performed on five gauge blocks of the highest accuracy class, of nominal lengths of up to 100 mm. Five different laboratories carried out the measurements, using three times interferometric and three times comparative methods. The measurement results analysis indicates constant need for checking the measuring procedure at the metrology laboratories.

G. Iuculano, A. Zanobini, G. Pellegrini
A COMPUTATIONAL METHOD IN THE CONSTRUCTION OF A PROBABILITY REGION OF CONFIDENCE

The construction of a region of confidence or "confidence belt", that is the expression of an expanded uncertainty with a given coverage probability, for measurements performed on the same measurand by different processes, is a critical task in the perspective to establish a measurement traceability on a global basis. An alternative procedure to the analytical one suggested in the Guide to the Expression of Uncertainty in Measurement, strictly related to the validity of the Central Limit Theorem, is desirable, in order to cover a larger range of situations not included in the normal distribution cases. In this work statistical approach is proposed based on the use of Monte Carlo approximation technique and on the bootstrap resampling iteration. An experimental model is examined to check the validity of the proposed method.

M.T. Lopez Esteban, T.E. Fernandez Vicente
TRACEABILITY IN GAS MIXTURE

The 20th Conférence Générale des Poids et Mesures (1995), invited National Metrology Laboratories and other organizations (national and international), to collaborate wich the Comité International and the new Comité Consultatif in establising world-wide traceability at the highest level for measurement in chemistry.
In 1998 the Spanish Center of Metrology began a new project with the objective, inside its performance field related to the obtainment, development and difussion of the national measurement standards, of beginning the necessary works to develop an aspect never contemplated before in the chemical field, and inside it especifically the primary standard mixtures certification in order to assure traceability in gas mixture.

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