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Zhang Zhimin, Zhang Yue, Guo Bin, Meng Feng, Li Tao, Ji Honglei, Dai Ming
THE DEVELOPMENT OF 100 N·m TORQUE STANDARD MACHINE AT NIM

A set of 100 N·m torque standard machine is newly developed at National Institute of Metrology (NIM). By adapting the air bearing with low friction as the arm lever fulcrum, the low expansion alloy (INVOR) as the arm lever material and the accurate machining and adjustment technology, the uncertainty of 100 N·m torque standard machine is minimized. This machine is capable of realizing torque from 1 N·m to 100 N·m both in clockwise and anticlockwise direction. The working principle and mechanical structure of the machine are introduced, the uncertainty assessment and results of performance test are described. The results show that the repeatability of 100 N·m torque machine is better than 2 × 10-5 the uncertainty is smaller than 2 × 10-5 (k = 2).

Christian Buchner
DETERMINATION OF MICRO-FORCES FROM 1 µN UP TO 10 N REALIZED WITH A FULL AUTOMATICALLY DEAD LOAD MACHINE DEVELOPED BY THE BEV

The Federal Office of Metrology and Surveying (BEV, Austria), developed in cooperation with the Vienna University of Technology an automatical Dead Load Machine to determine low force in the range from of 1 µmN up to 10 N.
This Dead Load Machine allows 10 µN steps to determine low force by weights directly and has a resolution of 1 µN realised by a balance. Due to its special construction, the measuring range is continuous from 10 N tension to 10 N compression whereby it is possible to cover the complete range in 10 µN steps by loading weights. To realise forcesteps of 1 µN a ballance with a readability of 1 µg is coupled with a specially designed hydrostatic force transducer the suspension system of the weights.

Andrzej Miekina, Roman Z. Morawski
A CALIBRATION METHOD, BASED ON RIDGE LS ESTIMATOR DESIGNED FOR DETERMINATION OF OLIVE OIL MIXTURES ON THE BASIS OF NIR SPECTRAL DATA

The spectrophotometric analysis of oil mixtures, containing olive oil, is the subject of this paper. Its objective is to propose and evaluate a new methodology for determination of a selected component of such a mixture. According to this methodology, the space of concentration values to be estimated is partitioned into subspaces and the calibration is performed separately for each subspace by means of a new piecewise ridge least-squares estimator. The estimation of concentrations is carried out, using the results of calibration, in two cycles: first, rough estimates of concentrations are found and a corresponding subspace is identified; next, the results of calibration, obtained for this subspace, are used for refining the estimates of concentrations. The performance of the proposed methodology is assessed using a criterion related to measurement uncertainty.

Guido Sassi, Alessia Demichelis, MariaPaola Sassi
A DYNAMIC TRACE VOC GENERATOR USEFUL FOR GLOBAL CLIMATE CHANGE STUDY

With the goal of the realization of a primary standard of amount-of-substance fraction of VOC (Volatile Organic Compounds) at trace level, a dynamic generator is constructed, based on the diffusion phenomena, according to ISO 6145-8. Generator will be followed by a dilution system. In the present paper, generator performances are discussed.
The analysis of ISO 6145-8 shows that temperature control gives the main contribution to uncertainty. The use of a more precise temperature and evaporated VOC mass results to be the main contribution. Weekly measurements of diffusion rate demonstrate the correct uncertainty calculation and the enhances due to the more precise temperature control. Uncertainty of diffusion rate was calculated as composed uncertainty of measured variables to be 0,4% for 20 µg/min by weekly measurements instead 0.8% calculated for the ISO 6145-8 conditions. Type A calculation of uncertainty on experimental data, corrected by pressure, confirmed theoretical uncertainty calculation.

Christian Buchner
DEVELOPMENT AND REALISATION OF A FULLY AUTOMATIC TESTING FACILITY FOR DETERMINING THE VOLUME OF E1 WEIGHTS UP TO 50 KG BASED ON HYDROSTATIC WEIGHING

The Federal Office of Metrology and Surveying (BEV, Austria) has developed and realised a new fully automatic test System for hydrostatic weighing and determining the density of solids up to 50 kg. This volume comparator allows a full automatically determination of the volume of E1 weights and plummets in the range from 1 kg up to 50 kg through direct comparison with one single volume reference (e.g. a Silicium sphere) with high accuracy. In this volume comparator, two hydrostatic weighing systems for density determination work simultaneously together so that it is possible to compare the density of a small, well-known standard sinker directly with the density of a submerged solid with masses up to 50 kg.

Ivan Frollo, Peter Andris, Jiri Pribil, Lubomir Vojtisek, Zuzana Holubekova
ELECTROMAGNETIC PHANTOM DESIGN FOR MEASUREMENT AND IMAGING QUALITY TESTING USING NMR IMAGING METHODS

Electromagnetic phantom design for measurement and imaging quality testing using NMR imaging has been performed. First attempts of electromagnetic phantom computation and testing on an experimental NMR 0.1 T imager were accomplished. The existing geometrical and chemical phantoms are generally used for testing of NMR imaging systems. They are simple cylindrical or rectangular objects with different dimensions and shapes with holes filled with specially prepared water solutions. In our experiments a homogeneous phantom (reference medium) was used - a container filled with water - as a standard. The resultant image represents the magnetic field distribution in the homogeneous phantom. For detection a standard gradient-echo imaging method, susceptible to magnetic field homogeneity, was used. An image acquired by this method is actually a projection of the sample properties onto the homogeneous phantom.
The goal of the paper is to map and image the magnetic field deformation using NMR imaging methods. In our experiments we are using a slender rectangular vessel with constant thickness filled with specially prepared water. A carefully tailored gradient-echo NMR measuring sequence was used.

Marc Fontana, Patrice Bourson, Ivana Durickovic, Julien Martin, Jean-Marie Chassot, Mario Marcherri, Rémy Claverie
RAMAN SENSORS: INTEREST AND APPLICATIONS

We demonstrate the interest of the Raman sensors in various aspects of studies in chemistry and physics. We illustrate the advantages of this technique in two applications that we have recently investigated. For the first industrial application, we related the stress of a polymer during its deformation with the Raman intensity and for the second, we managed to determine the NaCl concentration in a liquid solution. For these two applications, we develop our own signal processing to extract information from the Raman intensity.

Marek Niedostatkiewicz, Romuald Zielonko
OPTIMISATION OF ORTHOGONAL POLYNOMIAL SIGNALS FOR DIRECT IDENTIFICATION OF EQUIVALENT CIRCUIT PARAMETERS

The equivalent electrical circuits (mostly multielement two-terminals) are the common used method of modelling many technical and biological objects. The parameter identification of this kind of circuits is important in testing and diagnosis of many objects. The paper presents a time-domain identification method dedicated mainly for monitoring and diagnosis of anticorrosion coating. The method is based on applying a sequence of polynomials and measuring the object's response at the end of every signal in the sequence. Equivalent circuit parameters are calculated directly from responses using analytical equations, determined by impedance circuit topology. In the paper the optimisation of non-conventional Gegenbauer and Jacobi polynomial signals against the criteria of stationary error and uncertainty propagation is presented.

Carlo Ferrero, Adelina Leka
A COMPARATIVE VERIFICATION OF FORCE CALIBRATION MACHINES USED BY AN ACCREDITED LABORATORY

One of the most important activities of the National Accreditation Body (NAB) is the organisation of a series of comparisons (ILC), at the National level, to verify the measurements capability of the accredited laboratories.
For evaluation of the best measurement capability of AEP Transducers -an calibration accredited laboratory for Force quantity - over several years (1999-2005) are carried out measurements during accreditation and re-accreditation process of this SIT Centre, whose main results are reported in the following.
The results were evaluated using the En - normalised error - according to the SIT Doc-511.
The metrological procedures applied and the results of the accreditation of the SIT Centre, show that the best measurement capabilities and the total uncertainty, including transfer standards contribution and long term stability, can be considered as well:
± 50 ppm for the 50 kN dead weight machine (DWM);
± 250 ppm for the 200 kN Comparison machine;
± 350 ppm for the 1 MN Comparison machine (compression)
± 250 ppm for the 1 MN Comparison machine (tension).

Gopal Mahesh, Boby George, V. Jayashankar, V. Jagadeesh Kumar
CHARACTERIZING MAGNETIC MATERIALS USING VIRTUAL INSTRUMENTATION

A virtual instrumentation based scheme is developed for the characterization of magnetic materials. The principle used for measurement is derived from the comparison method of testing instrument transformers. A prototype has been developed by suitably modifying an instrument transformer test set. Characterization of magnetic materials at single frequency and multiple frequencies have been carried out. Typical test results obtained are presented in the paper. The developed instrument substantially reduces the testing time associated with magnetic characterization.

Page 750 of 977 Results 7491 - 7500 of 9762