IMEKO Event Proceedings

Page 790 of 855 Results 7891 - 7900 of 8545

Beata Pałczyńska
TIME – FREQUENCY ANALYSIS OF NON-STATIONARY MAGNETIC FIELDS

The paper considers applying the quadratic joint time – frequency transform for the spectral analysis of the non-stationary magnetic fields. The general properties, advantages and disadvantages of the quadratic algorithms from Cohen’s class like the short – time Fourier transform (STFT) spectrogram and the pseudo Wigner – Ville (PWV) distribution as well as the adaptive spectrogram are discussed. The selected results of the off-line time-frequency analysis of the recorded signals of magnetic field of ship bow thrusters drive with frequency converter are presented. Performed time-frequency analysis enabled the signal identification in time periods. If the frequency contents of the analyzed signal don’t change rapidly, then the STFT spectrogram can be applied with relatively wide window function, to obtain a good frequency resolution. The PWV distribution is useful for analyzing signals that have widely separated components for which a fine time-frequency resolution is required. The adaptive algorithm is characterized by the most accurate detection of investigated nonstationary components, but it requires more computation time, which is suitable only for off-line analysis.

Domenico Luca Carnì, Domenico Grimaldi, Leonardo Serratore
Time and Frequency Domain Tests for ΣΔ Modulators

The paper deals with the classification method of some architectures of ΣΔ modulators. The classification is based on the analysis of the different trends of the output signals characterizing some ΣΔ modulator architectures. The method operates (i) by feeding the ΣΔ modulator with sinusoidal signal, and (ii) by analysing the output signals in the time or in the frequency domain. The classification consists in (i) distinguishing between low pass and band pass ΣΔ modulator, (ii) identifying both the Single Quantizer Loop (SQL) and the Multistage Noise Shapers (MASH) architecture, (iii) evaluating the levels of the quantizer block inside the SQL architecture, and (iv) detecting the number of cascaded stage inside the MASH architecture. In order to validate the proposed method, numerical tests are performed by referring to the noumerous architectures of ΣΔ modulators proposed in the relevant literature.

A. Saglam, P. M. A. van der Kam, G. J. van Essen, D. H. Hebels
TIME DEPENDENT PERFORMANCE OF TURBINE GAS METERS

Gastransport Services in the Netherlands, uses turbine gas meters to measure the gas flow to local gas distribution companies, large industrial customers and power plants GTS operates approximately 1100 city gate stations, at a delivery pressure of usually 8 bar.
In the Netherlands, the procedures for determining the operational performance of the turbine meters are agreed upon between Gastransport Services and its customers. As a result of this agreement, Gastransport Services inspects the total population of turbine meters by means of the well-known variables-acceptance-sampling. Each year, 60 turbine meters are selected randomly from the total population. Subsequently, the selected turbine meters are calibrated traceable to international standards by Netherlands Measurment Institute (NMi). The information from these recalibrations is used to study the stability of the turbine meters.
Because, through the years a lot of information has been gathered on the turbine meters performance, the presence of statistically significant relationships (correlation) between the performance in time of the meters on the one hand and properties like the construction year, the pressure class, the size, the maximum allowable flow rate and/or the recalibration period of the meter on the other hand, can be investigated. In this presentation, analysis-of-variance and the quadrant-correlation-test are used to test for the presence of such correlations.
The aforementioned five properties were analysed for the presence of correlation at two different calibration pressures and with different definitions of drift to express the performance in time of gas turbine meters. For a specific calibration pressure and a specific type of drift, the performance in time dependents on the recalibration period and the size of the turbine meter. Furthermore, the correlation analysis, showed that a turbine gas meter seems to reach a steady state in time, expressed in terms of shift of the weighted mean error.

Romuald Zielonko, Marek Niedostatkiewicz
TIME DOMAIN DIAGNOSIS OF ANTICORROSION COATINGS VIA SHAPE DESIGNED MEASUREMENT SIGNALS

The paper presents time domain diagnostic method of anticorrosion coating on the level of equivalent circuit parameter identification. The method is based on applying non-conventional, shape-designed stimuli signals and measuring the object responses (so-called observables) at a given time T. Equivalent circuit parameters are calculated directly from observables using analytical equations, determinated by modelling circuit topology. In the paper the theoretical basis of the method is presented, together with measurement methodology and simulation results for 4 elements anticorrosion coating equivalent circuit.

Massimo Aiello, Antonio Cataliotti, Valentina Cosentino, Salvatore Nuccio
TIME DOMAIN METHOD TO DETECT HARMONIC SOURCES IN UNBALANCED POWER SYSTEMS

In recent years the problem of harmonic pollution has become more urgent, because of the development in distribution systems of non linear loads that draw non-sinusoidal currents. This paper presents a time domain method for harmonics sources detection in power systems, which can be usefully applied also in presence of unbalance or asymmetry. Harmonic power flows are calculated in real time and no spectral analysis is required for the evaluation of currents amplitudes and phase angles. The development of a new instrument is described, which is able to measure several network power quality parameters; measurement accuracy is estimated and experimental results are reported.

Marek Niedostatkiewicz, Romuald Zielonko
TIME DOMAIN PARAMETER IDENTIFICATION OF ANTICORROSION COATING VIA SOME TYPES OF POLYNOMIAL SIGNALS

The paper presents a time domain method of anticorrosion coating diagnosis on the level of equivalent circuit parameter identification, based on applying a set of shape-designed polynomials and measuring the object’s responses (so-called observables) at a given time T. Equivalent circuit parameters are calculated directly from observables using analytical equations, determined by modelling circuit topology. In the paper the comparison of different polynomial signals (Chebyshev, Legendre, Optimal) against the criteria of stationary error propagation is presented, on the base of analytical and simulation results.

Luís Rosado, Pedro Ramos, Moisés Piedade
Time Domain Processing of Pulsed Differential Eddy Currents Testing Signals

The use of pulsed stimulus on Eddy Currents Testing is currently applied on multiple applications from conductivity measurements to defects detection on metallic parts. This type of stimulus is frequency rich since it is composed by multiple harmonics and this allows testing with different depth concentration of the eddy currents as they are subject to the skin effect. In this paper, pulsed stimuli are used while testing with a custom probe. The probe output signals are acquired and processed digitally in the time domain using a simple feature, its RMS value. Two-dimensional scans were performed allowing the imaging of a tested metallic part with different defects.

Valli, E., Palagano, R., Berardinelli, A., Ragni, L., Moreda, W., Pérez, Camino M., Bendini, A., Gallina Toschi, T.
Time Domain Reflectometry as a promising analytical approach for the determination of fatty acid ethyl esters in extra virgin olive oils

Fatty acid ethyl esters (FAEEs) are important quality and genuineness parameters for extra virgin olive oils (EVOOs), since they are considered i) direct markers strongly related to the quality of the olives and ii) possible indirect markers of an illegal soft-deodorization treatment. The EU Reg. 2095/2016 fixes the actual limit for FAEEs at 35 mg/kg for the commercial category of EVOO; the official EU analytical method for their determination in olive oil is particularly time consuming, so robust, rapid, and environmental friendly approaches for a preliminary screening of samples could be highly desirable. In this context, a set of extra virgin, virgin and lampante olive oils was considered. Firstly the content in FAEEs has been determined by following the EU official method. In parallel, all the samples were also analyzed by Time Domain Reflectometry (TDR) and waveforms were elaborated by Partial Least Squares multivariate regression (PLS). Test set validations procedures were considered. The aim was to build up-loadable models for the prediction of FAEEs, employing the data coming from conventional techniques for the calibration. Discriminant multivariate data analysis was also explored to classify samples. This approach is devoted to develop a prototype for validating the screening procedure. This work was developed in the context of the project OLEUM “Advanced solutions for assuring authenticity and quality of olive oil at global scale“ funded by the European Commission within the Horizon 2020 Programme (2014–2020, grant agreement no. 635690).

N.Hlupic, D.Petrinovic, J.Butorac
TIME DOMAIN SPECTRAL ANALYSIS, NEW APPROACH FOR HIGH ACCURACY

Time Domain Spectral Analysis is presented in this paper as a new, original approach to the analysis of signal spectrum (having samples of the measured signal). The uniqueness of this method is in avoiding of any kind of Fourier transform, which showed to be of limited accuracy when the samples' errors (measurement imperfections) are taken into account, even applying windows and various approximations. The majority of calculations are based on our previously developed method for high accuracy measurement of a single sine wave. The basic idea of this method is to extract all time domain samples of a particular wave from samples of the whole signal, and then to calculate parameters of that component by applying the method for measurement of a single sine wave. This approach has been tested with extended and rigorous computer simulations (explained further in the text) and partially in real laboratory measurements. It is demonstrated that estimated accuracy of parameters of the fundamental wave is about 4 ppm, even though the samples' errors are of the order of 20 ppm. The estimated accuracy of the higher harmonics is better than 500 ppm (regardless of their number, and the same for amplitude and phase).

S. Shariat-Panahi, F. Corrêa Alegria, Antoni Mànuel, Joaquín del Río
TIME DRIFT OF OCEAN BOTTOM SEISMOMETERS (OBS)

During the past decades, Ocean Bottom Seismometers (OBS) have played a key role in permanent seismic activity monitoring at sea as well as allowing a better understating of the earth interior. Data collected by the instrument can provide information on the ocean bottom sub-layers down to a depth of 40 km beneath the ocean floor. The accuracy of the results directly depends on the time drift of the equipment due to change of environmental conditions. Time base of the OBS is given by a unique stable crystal oscillator.
This paper presents the time drift study of an Ocean Bottom Seismometer in real environmental conditions. By means of a climate chamber, temperature and humidity tests of a general purpose time base generator were carried out and crystal temperature stability and time drift were calculated. Furthermore, the behaviour of the time drift of the instrument has been evaluated in order to correct the data in the data processing stage.

Page 790 of 855 Results 7891 - 7900 of 8545