IMEKO Event Proceedings

Page 9 of 748 Results 81 - 90 of 7479

Václav Matz, Pedro M. Ramos, Nuno B. Brás, A. Cruz Serra
A COMPARATIVE EVALUATION BETWEEN FREQUENCY ESTIMATION ALGORITHMS FOR POWER QUALITY ASSESSMENT IN DSP IMPLEMENTATION

Numerous frequency estimation algorithms are available for power quality assessment of frequency. In this paper, a comparative study in terms of accuracy, number of operations and memory cost is presented to select the best solution for implementation in a digital signal processor, in the context of typical power quality frequency disturbances measurements.

Jerzy Augustyn
A COMPARATIVE EVALUATION OF SOME LMS-BASED ALGORITHMS FOR CALCULATING OF IMPEDANCE COMPONENTS IN THE SAMPLING SENSOR INSTRUMENT

The properties of some algorithms based on digital signal processing for the impedance components evaluation in circuits with sampling sensor have been analysed. It is supposed that the voltage and current are sampled synchronously to the fundamental frequency of the generated sinusoidal signal. Two groups of fitting sine wave algorithms, which are based on the least mean square (LMS) technique, have been described. The first one reconstructs indirect measurement method. The second group of algorithms estimates the unknown impedance components by direct method. In all these algorithms to simplify the calculations one can use different form of input matrix. The uncertainty’s propagation by described algorithms can be analysed by means of covariance matrix. In order to verify the performance of the considered algorithms (e.g., accuracy, estimator bias and convergence) the Monte Carlo simulations are realised in MATLAB. It is shown that those algorithms provide minimisation of uncertainty for selected number of samples and phase angles. The influence of the quantization error of the AD converters and jitters of the sampling time upon the uncertainty of the processing results of described algorithms have been carried out.

Nicolae Daniel Irimia, Florin Ioan Lazar
A Comparative Study of Different BLDC Motor Construction Types Used in Automotive Industry under Specific Command Strategies

The automotive industry future focus is based on the construction of hybrid and fully electric vehicles, with the trend towards autonomous driving. Different electric drive subsystems from the structure of these electric vehicles are aiming to achieve a higher efficiency, which is why permanent magnet synchronous machines of either BLDC / PMSM type are currently being used as main actuators in their construction. These types of electrical machines are known in the literature as having sufficient power density and efficiency to meet the criteria and requirements of the automotive building industry. That's why an important area of interest is the construction and the control topology specific to these electrical machines. Based on these considerations, the paper purpose is to present a comparative study regarding different constructive types concepts of BLDC electrical machines and different control methods related to them. In order to validate the theoretical aspects of this study, two distinct ways of modelling and simulation were used in parallel: the first method is based on FEM (Finite Element Method) analysis and the second analytical method uses the MATLAB / Simulink software package.

Roman Z. Morawski, Andrzej Miekina
A COMPARATIVE STUDY OF FORTY ALGORITHMS FOR SPECTROPHOTOMETRIC ANALYSIS OF EDIBLE OIL MIXTURES

This paper is devoted to the comparison of forty least-squares-type algorithms for spectrophotometric analysis of edible oil mixtures, viz. olive oil corrupted with corn oil and nut oil. The paper is providing a specification of the compared algorithms, a description of the methodology of their comparison, selected results of comparison, and conclusions drawn from them.

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).

Seung-Hee An, Jae-Young Her
A COMPARISION OF ACCURACY ON ORIFICE METER WITH AND WITHOUT STRAIGHTENER IN THE FIELD

The objective of this study is to improve the metering facilities at metering stations of Korea Gas Corporation (KOGAS), which are being operated in unsatisfying meter run conditions. For experiments, a test facility was constructed to simulate one of the metering stations and it was set up in Jung-dong metering station. Presently, KOGAS has 60 nationwide metering stations and among them, 34 metering stations are located in metropolitan area.
Tests were performed with both diameter ratio (<i>β = <i>d / <i>D) and flow rate variations and the test range of diameter ratio of orifice flow meter was from 0.3 to 0.7. The results showed that the error was - 7.2 % (maximum flow rate=3,661 Nm³/h) and - 3.1% (maximum flow rate=11,716 Nm³/h) for <i>β = 0.3 and 0.7, respectively without straightener. Thus, the diameter ratio was inversely proportional to the error, but on the contrary, the flow rate was proportional to the error. For the case of straghtener installation, the error showed 0.4 % (maximum flow rate = 3,030 Nm³/h) and 0.8% (maximum flow rate = 9,204 Nm³/h) for <i>β = 0.3 and 0.7, respectively. The error was not sensitive to the diameter ratio, but it was decreased when the flow rate was increased.

Francesco Orsini, Andrea Rossi, Andrea Scorza, Fabio Botta, Salvatore Andrea Sciuto
A comparison between a commercial WBV platform and an experimental prototype

There are many commercial WBV platforms for clinical applications but in literature very few have been tested to verify their actual amplitude, frequency spectra and waveform shape of vibration, although some clinical studies showed that these parameters can influence significantly the muscles performance. In this study the performances of a prototype WBV1 designed by the authors are compared with a commercial platform WBV2 typically used in clinical and rehabilitation investigations. Tests performed with four accelerometers in 3 different directions show the presence of transversal accelerations that in some cases exceeded the vertical one in WBV2 while they were always lower than the 25% in WBV1. Also the waveform shape of the vibration provided by WBV1 , evaluated by means of the SINAD parameter, show a better value compared to the commercial device: indeed secondary harmonics reaches the 30% of the fundamental in WBV2 but they are always below the 25% in the prototype.

Xumo Li
A COMPARISON BETWEEN A RESISTANCE BRIDGE AND AN INTEGRATED-CIRCUIT RESISTANCE THERMOMETER READOUT USED FOR SPRT CALIBRATION

Specially designed bridges are used for standard platinum resistance thermometer (SPRT) calibration to achieve lowest uncertainty. Such bridges are expensive and their measuring speeds are slow. A new type of instrument reported a few years ago was compared against the bridge to see if it is possible to use the new instrument instead of the bridge for SPRT calibration in some cases. Four SPRTs were calibrated at the triple point of water and the freezing points of tin and zinc using a Model 6010T Bridge and the new instrument (Model 1590) simultaneously. At these calibration points the maximum differences between the two instruments were within 0.4 mK at the tin point, and within 0.7 mK at the zinc point. The maximum difference in resistance ratio W(t) at these points was within 0.9 ppm of the readings. The differences over the entire range from 0°C to 419.527°C were calculated for the four SPRTs. The maximum differences were within 0.1 mK close to 0°C, within 0.5 mK at 300°C and within 0.7 mK at 420°C. The comparison results show the new instrument can be used for SPRT calibration to achieve an expanded uncertainty (k = 2) as low as 1.5 mK.

Barry Pratt, Andy Robinson
A COMPARISON BETWEEN SUPPORTED AND UNSUPPORTED BEAMS FOR USE IN STATIC TORQUE CALIBRATIONS

In industry, calibration beams are frequently coupled directly to the measurement transducer. This paper aims to quantify the effect of using such a method in contrast to the bearing supported case for a range of commercially available transducers.

Michal Ulvr, Petr Kašpar
A COMPARISON OF DC AND AC METHODS FOR CALIBRATION OF SEARCH COILS WITH A HIGH AREA TURNS VALUE

Search coils are widely used for measuring AC magnetic fields, and in special cases for measuring DC magnetic fields with the webermeter and for comparing magnetic flux density standards and magnetic flux standards. This paper compares the measuring equipment that is used and the accuracy that can be achieved by known DC and AC methods for calibrating search coils with a high area turns value.

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