Metrological Problems Research Articles (Page 6)

To optimize the tribological performance of miniaturized systems, adequate experimental means are needed. Current microtribometers suffer from inability to ensure parallel flat-on-flat contact and often experience metrological problems related to the geometry of the force sensing element. The present work demonstrates how these limitations can be removed in either homemade or commercial microtribometers by using a self-aligning system of specimen holders and an improved force sensor based on a symmetric design principle. Preliminary tests conducted on a polyvinylsiloxane∕glass tribopair confirm the satisfactory operation of the setup and show no effect of applied load on pull-off force and friction coefficient.

Contemporary methods are presented for redefining the unit of mass standard, i.e., the kilogram prototype. The main tendencies in improving these methods in order to reduce the uncertainty of reproducing the unit of mass are discussed. It is noted that the use of precise values of a number of fundamental physical constants, primarily the Avogadro number, is important.

On the basis of quantitative chemical measurements many important decisions are made in support of legislation or in industrial processes or social aspects. For this reason it is important to improve the quality of chemical measurement results and thus make them comparable and acceptable everywhere. The measurement quality is important to enable an equivalent implementation of the European Union regulations and directives across an enlarged EU. In this context, the European Commission–Joint Research Centre–Institute for Reference Materials and Measurement (EC-JRC-IRMM) set up a programme to improve the scientific basis for metrology in chemistry (MiC) in EU candidate countries in the framework of EU enlargement. Several activities were initiated, such as training, fellowships, sponsoring of seminars, conferences and participation in interlaboratory comparisons. To disseminate measurement traceability, IRMM provides through its International Measurement Evaluation Programme (IMEP) an interlaboratory tool to enable the benchmarking of laboratory performance. IMEP emphasizes the metrological aspects of measurement results, such as traceability and measurement uncertainty. In this way it has become a publicly available European tool for MiC. The Romanian Bureau of Legal Metrology – National Institute of Metrology (BRML-INM) actively supports the participation of Romanian authorized and field laboratories in IMEP interlaboratory comparisons. This paper describes the interest of Romanian laboratories participating in this programme, the analytical and metrological problems that became relevant during these exercises and some actions for improvement. The results from Romanian laboratories participating in IMEP-12 (water), IMEP-16 (wine), IMEP-17 (human serum) and IMEP-20 (tuna fish) are presented. To conclude, the educational and training activities at national level organized jointly by the Romanian National Institute of Metrology (INM) and IRMM are also mentioned.

Fundamental problems of modern metrology are considered. It is suggested that problems arising in metrology during the construction of a system of measurement units are resolved at two levels: fundamental (theoretical) and practical. The increasing importance of developing and applying standards based directly on fundamental physical constants is noted.

Roundness and cylindricity evaluations are among the most important problems in computational metrology, and are based on sets of surface measurements (input data points). A recent approach to such evaluations is based on a linear-programming approach yielding a rapidly converging solution. Such a solution is determined by a fixed-size subset of a large input set. With the intent to simplify the main computational task, it appears desirable to cull from the input any point that cannot provably define the solution. In this note we present an analysis and an efficient solution to the problem of culling the input set. For input data points arranged in cross-sections under mild conditions of uniformity, this algorithm runs in linear time.

Problems of the metrological assurance of the manufacture of large industrial objects are considered and ways of solving them are examined.

In this paper the problem of experimentally testing the mechanical reliability of electronic components for quality control is approached. In general, many tests are performed on electronic devices (personal computers, power supply units, lamps, etc.), according to the relevant international standards (IEC), in order to verify their resistance to shock and vibrations, but these are mainly “go no‐go” experiments, performed on few samples taken from the production batches.The idea here proposed is to improve the efficiency of these tests by using electro‐optic techniques for the measurement of the vibration behaviour of the components under known excitation. This would allow the on‐line testing of a high percentage of the production and would be useful to give important feedback to the design process.Scanning laser Doppler vibrometry seems to be a valuable solution for this problem, thanks to its capabilities of measuring several spatially‐defined points on a vibrating object with reduced testing time for on‐line application, with high sensitivity and accuracy, non‐intrusivity and with any kind of excitation signal. Experimental tests are performed on a power supply: the results show the effectiveness of the proposed approach. The metrological problems connected with the on‐line implementation are also discussed.

Pollution fiows on receiving waters measurement is now compulsory in France to survey the sewer systems functionning but metrological problems still remain. Continuous pollution measurement systems (based on turbidity and ultra-violet and visible absorbances) were tested in situ (in a combined system at the upstream of a detention basin). These systems require still precautions (hydraulic feeding line, maintenances, calibrations...) Neverheless we can be optimist in regards to the results which have been obtained: the optical measurement of SS and COD is interesting to determine average or long term pollution loads.

We present a compact holographic interferometer that uses a photorefractive crystal of the sillenite family as a holographic recording medium. Its development is based on a previous prototype that showed lack of flexibility and portability. We briefly discuss the main improvements leading to a compact device. Applications of this instrument in various metrological problems are shown, among which are two that were not already considered using holography, namely measurement of a thermal expansion coefficient and detection of fingerprints.

Metrological Problems of Testing Medical Ultrasonic Equipment

Metrological Problems during Hardness Measurements of thin layers. The essential calibration problem at indentation measurements in the micro and nano range, the determination of the tip geometry of the indenter, can be solved with a modified SFM which allows coordinate measurements with traceability to the length unit. A comparison of the area functions which were determined with an SFM and a reference material showed a sufficiently good agreement. For the remaining quantities of the indentation test influencing the uncertainty of measurement practicable calibration methods are existing. New challenges to the development of calibration methods for indentation testers puts the nano range which for the assessment of mechanical properties of layers with a thickness in the nanometer range gains increasing importance.

Vibration measurements for diagnosis of structural defects on human teeth

Efficient approximation and optimization algorithms for computational metrology

Pressure standards and sensors up to 3 GPa, actual state and development trends

Pulsars are the most stable natural frequency standards. They can be applied to a number of principal problems of modern astronomy and time-keeping metrology. The full exploration of pulsar properties requires obtaining unbiased estimates of the spin and orbital parameters. These estimates depend essentially on the random noise component being revealed in the residuals of time of arrivals (TOA). In the present paper, the influence of low-frequency ("red") timing noise with spectral indices from 1 to 6 on TOA residuals, variances, and covariances of estimates of measured parameters of single and binary pulsars are studied. In order to determine their functional dependence on time, an analytic technique of processing of observational data in time domain is developed which takes into account both stationary and non-stationary components of noise. Our analysis includes a simplified timing model of a binary pulsar in a circular orbit and procedure of estimation of pulsar parameters and residuals under the influence of red noise. We reconfirm that uncorrelated white noise of errors of measurements of TOA brings on gradually decreasing residuals, variances and covariances of all parameters. On the other hand, we show that any red noise causes the residuals, variances, and covariances of certain parameters to increase with time. Hence, the low frequency noise corrupts our observations and reduces experimental possibilities for better tests of General Relativity Theory. We also treat in detail the influence of a polynomial drift of noise on the residuals and fitting parameters. Results of the analitic analysis are used for discussion of a statistic describing stabilities of kinematic and dynamic pulsar time scales.

Recent Developments in Hardness Testing and their Implications for Standardisation

An examination is made of the principles of optophysical measurements and of the structure of optoelectric conversion. The functions of the All-Union Scientific-Research Institute for Optophysical Measurements (VNI-IOFI), as the principal scientific metrological center, are described and the current and prospective fundatmental problems in the field of optophysical measurements are briefly characterized. Particular attention is devoted to photometric and radiometric standards utilizing a high-temperature black-body model, to the problems of the remote transfer of the sizes of units, and to creating a common standard for the units of power and energy for different branches of physics.

Methodological problems of metrology are discussed. Metrology is viewed as an empirical scientific discipline in which the basic notions are determined in an operational manner and ought to be verifiable. Relationship between metrology and theoretical and experimental scientific branches is established. From the aspect of the methodology proposed herein, certain notions of metrology are incorrectly defined and not verifiable.

Problems in surface metrology

New trends in metrological research on small and ultrasmall parameters of motion are considered. The main attention is devoted to the metrology of vector quantitaties, the reproduction of small and ultrasmall parameters against a background of considerably greater interference, and the use of the gravitational constant. The importance of further work directed at increasing the accuracy of determining free-fall acceleration and the gravitational constant is emphasized. The urgent directions for further research are formulated.