M&MS - volume XVIII - number 2/2011

POLISH ACADEMY OF SCIENCES

Division IV: Engineering Sciences

Committee on Metrology
and Scientific Instrumentation

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VOLUME XVIII - NUMBER 2/2011

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CONTENTS

1. Sedlacek, M., Stoudek Z. - Active power measurements - an overview and comparison of DSP algorithms by noncoherent sampling	173
2. Santos, J., Ramos, P.M. - DSPIC - Based impedance measuring instrument	185
3. Poniatowska, M. - Parameters for CMM contact measurements of free-form surfaces	199
4. Rajamohan, G., Shunmugam, M.S., Samuel, G.L. - Practical measurement strategies for verification of freeform surfaces using coordinate measuring machines	209
5. Petrík, J., Palfy, P. - The influence of the load on the hardness	223
6. Elcio Cruz de Oliveira - Critical metrological evaluation of fuel analyses by measurement uncertainty	235
7. Sroka, R. - Application of sensitivity analysis to the correction of static characteristics of a phase angle modulator	249
8. Chudzik, S., Minkina, W. - An idea of a measurement system for determining thermal parameters of heat insulation materials	261
9. Lidong Liu, Jifeng Hu, Yishu He, Chunlin Han, Huiyong Li, Jun Li - A velocity measurement method based on scaling parameter estimation of chaotic system	275
10. Fexa, P., Verdal, J., Svatoš, J. - DAC testing using modulated signals	283
11. Urbanek, J., Barszcz, T., Sawalhi, N., Randall, R.B. - Comparison of amplitude-based and phase-based method for speed tracking in application to wind turbines.	295
12. Skalski, A., Turcza, P. - Heart segmentation in echo images	305
13. Yue Tong, Hongbin Li - Highly accurate calibration system for electronic instrument transformers	315
14. Lewandowski, J. - Inductive sensors for weighing of mass	323
15. Kowalczyk, A., Hanus, R., Szlachta, A. - Investigation of the statistical method of time delay estimation based on conditional averaging of delayed signal	335

ABSTRACTS & FULL PAPERS

173

contents

ACTIVE POWER MEASUREMENTS - AN OVERVIEW AND A COMPARISON OF DSP ALGORITHMS BY NONCOHERENT SAMPLING

Milos Sedlacek, Zdenek Stoudek

Czech Technical University in Prague, Faculty of Electrical Engineering, Technicka 2, Prague 6, Czech Republic (sedlacem@fel.cvut.cz, +420 2 2435 2177, Zdenek.Stoudek@seznam.cz)

Abstract
This paper presents an overview of algorithms for one-phase active power estimation using digital signal processing in the time domain and in the frequency domain, and compares the properties of these algorithms for a sinusoidal test signal. The comparison involves not only algorithms that have already been published, but also a new algorithm. Additional information concerning some known algorithms is also included. We present the results of computer simulations in MATLAB and measurement results gained by means of computer plug-in boards, both multiplexed and using simultaneous signal sampling. The use of new cosine windows with a recently published iterative algorithm is also included, and the influence of additive noise in the test signal is evaluated.

Keywords: power estimation, digital signal processing, non-coherent sampling

Full paper (PDF, 1378kB)

185

contents

DSPIC-BASED IMPEDANCE MEASURING INSTRUMENT

José Santos¹⁾, Pedro M. Ramos²⁾

1) Instituto de Telecomunicaçőes, IST, UTL, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal (jose.dos.santos@ist.utl.pt, +351 218 418 485)
2) Instituto de Telecomunicaçőes, DEEC, IST, UTL, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal (pedro.ramos@lx.it.pt)

Abstract
An implemented impedance measuring instrument is described in this paper. The device uses a dsPIC (Digital Signal Peripheral Interface Controller) as a processing unit, and a DDS (Direct Digital Synthesizer) to stimulate the measurement circuit composed by the reference impedance and the unknown impedance. The voltages across the impedances are amplified by programmable gain instrumentation amplifiers and then digitized by analog to digital converters. The impedance is measured by applying a seven-parameter sine-fitting algorithm to estimate the sine signal parameters. The dsPIC communicates through RS-232 or USB with a computer, where the measurement results can be analyzed. The device also has an LCD to display the measurement results.

Keywords: impedance measurement, dsPIC, ADC, sine-fitting

Full paper (PDF, 1461kB)

199

contents

PARAMETERS FOR CMM CONTACT MEASUREMENTS OF FREE-FORM SURFACES

Małgorzata Poniatowska

Bialystok University of Technology, Division of Production Engineering, Wiejska 45C, 15-351 Bialystok, Poland (mponiat@pb.edu.pl, +48 85 746 9261)

Abstract
Obtaining discrete data is inseparably connected with losing information on surface properties. In contact measurements, the ball tip functions as a mechanical-geometrical filter. In coordinate measurements the coordinates of the measurement points of a discrete distribution on the measured surface are obtained. Surface geometric deviations are represented by a set of local deviations, i.e. deviations of measurement points from the nominal surface (the CAD model), determined in a direction normal to this surface. The results of measurements depend both on the ball tip diameter and the grid size of measurement points. This article presents findings on the influence of the ball tip diameter and the grid size on coordinate measurement results along with the experimental results of measurement of a free-form milled surface, in order to determine its local geometric deviations. One section of the surface under research was measured using different measurement parameters. The whole surface was also scanned with different parameters, observing the rule of selecting the tip diameter d and the sampling interval T in the ratio of 2:1.

Keywords: coordinate measurements, free-form surface, geometric deviations, measurement parameters

Full paper (PDF, 782kB)

209

contents

PRACTICAL MEASUREMENT STRATEGIES FOR VERIFICATION OF FREEFORM SURFACES USING COORDINATE MEASURING MACHINES

G. Rajamohan, M. S. Shunmugam, G. L. Samuel

Indian Institute of Technology Madras, Department of Mechanical Engineering, , Chennai - 600 036, India (g.rajamohan@yahoo.co.in, shun@iitm.ac.in, +91 44 2257 4677, samuelgl@iitm.ac.in)

Abstract
Freeform surfaces have wider engineering applications. Designers use B-splines, Non-Uniform Rational Bsplines, etc. to represent the freeform surfaces in CAD, while the manufacturers employ machines with controllers based on approximating functions or splines. Different errors also creep in during machining operations. Therefore the manufactured freeform surfaces have to be verified for conformance to design specification. Different points on the surface are probed using a coordinate measuring machine and substitute geometry of surface established from the measured points is compared with the design surface. The sampling points are distributed according to different strategies. In the present work, two new strategies of distributing the points on the basis of uniform surface area and dominant points are proposed, considering the geometrical nature of the surfaces. Metrological aspects such as probe contact and margins to be provided along the sides have also been included. The results are discussed in terms of deviation between measured points and substitute surface as well as between design and substitute surfaces, and compared with those obtained with the methods reported in the literature.

Keywords: freeform surface, coordinate measuring machine, machining errors, probe size, sampling strategies, substitute geometry

Full paper (PDF, 549kB)

223

contents

THE INFLUENCE OF THE LOAD ON THE HARDNESS

Jozef Petrík, Pavol Palfy

Technical University of Košice, Faculty of Metallurgy, Dept. of Integrated Management, Letná 9, 04 001 Košice, Slovakia (jozef.petrik@tuke.sk)

Abstract
The objective of the submitted paper is to analyze the influence of the load on the calibration of micro-hardness and hardness testers. The results were validated by Measurement Systems Analysis (MSA), Analysis of Variance (ANOVA) and Z-score. The relationship between the load and micro-hardness in calibration of micro-hardness testers cannot be explained by Kick's Law (Meyer's index "n" is different from 2). The conditions of Kick's Law are satisfied at macro-hardness calibration, the values of "n" are close to 2, regardless of the applied load. The apparent micro-hardness increases with the increase of the load up to 30 g; the reverse indentation size effect (ISE) behavior is typical for this interval of the loads. The influence of the load on the measured microhardness is statistically significant for majority of calibrations.

Keywords: hardness, load, calibration, uncertainty, MSA

Full paper (PDF, 234kB)

235

contents

CRITICAL METROLOGICAL EVALUATION OF FUEL ANALYSES BY MEASUREMENT UNCERTAINTY

Elcio Cruz de Oliveira

PETROBRAS TRANSPORTE S.A., Engineering Management, Av. Presidente Vargas, 328, 20091-060 Rio de Janeiro - RJ, Brazil (elciooliveira@petrobras.com.br, +55 21 3211 9223)

Abstract
It is now widely recognized that the evaluation of the uncertainty associated with a result is an essential part of any quantitative analysis. One way to use the estimation of measurement uncertainty as a metrological critical evaluation tool is the identification of sources of uncertainty on the analytical result, knowing the weak steps, in order to improve the method, when it is necessary. In this work, this methodology is applied to fuel analyses and the results show that the relevant sources of uncertainty are: beyond the repeatability, the resolution of the volumetric glassware and the blank in the analytical curve that are little studied.

Keywords: measurement uncertainty, critical metrological evaluation, resolution of the volumetric glassware, blank analytical, fuel analyses

Full paper (PDF, 195kB)

249

contents

APPLICATION OF SENSITIVITY ANALYSIS TO THE CORRECTION OF STATIC CHARACTERISTICS OF A PHASE ANGLE MODULATOR

Ryszard Sroka

AGH University of Science and Technology, Department of Measurement and Instrumentation, Al. Mickiewicza 30, 30-059 Cracow, Poland (rysieks@agh.edu.pl, +48 12 617 39 72)

Abstract
The paper presents definitions and relative measures of the system sensitivity and sensitivity of its errors. The model of a real system and model of an ideal measuring system were introduced. It allows to determine the errors of the system. The paper presents also how to use the error sensitivity analysis carried out on the models of the measuring system to the correction of the nonlinearity error of its static characteristic. The corrective function is determined as a relation between the input variable of the tested system and its chosen parameter. The use of the proposed method has been presented on the example of a phase angle modulator. The obtained results have been compared with the results of analytic calculations. The idea of a phase angle modulator is also presented.

Keywords: phase modulator, sensitivity analysis, static characteristics, methods of correction

Full paper (PDF, 463kB)

261

contents

AN IDEA OF A MEASUREMENT SYSTEM FOR DETERMINING THERMAL PARAMETERS OF HEAT INSULATION MATERIALS

Stanisław Chudzik, Waldemar Minkina

Częstochowa University of Technology, Institute of Electronics and Control Systems, Armii Krajowej 17, 42-200 Częstochowa, Poland (chudzik@el.pcz.czest.pl, minkina@el.pcz.czest.pl +48 34 325 0819)

Abstract
The article presents the prototype of a measurement system with a hot probe, designed for testing thermal parameters of heat insulation materials. The idea is to determine parameters of thermal insulation materials using a hot probe with an auxiliary thermometer and a trained artificial neural network. The network is trained on data extracted from a nonstationary two-dimensional model of heat conduction inside a sample of material with the hot probe and the auxiliary thermometer. The significant heat capacity of the probe handle is taken into account in the model. The finite element method (FEM) is applied to solve the system of partial differential equations describing the model. An artificial neural network (ANN) is used to estimate coefficients of the inverse heat conduction problem for a solid. The network determines values of the effective thermal conductivity and effective thermal diffusivity on the basis of temperature responses of the hot probe and the auxiliary thermometer. All calculations, like FEM, training and testing processes, were conducted in the MATLAB environment. Experimental results are also presented. The proposed measurement system for parameter testing is suitable for temporary measurements in a building site or factory.

Keywords: thermal conductivity, artificial neural networks, inverse heat conduction problem

Full paper (PDF, 1761kB)

275

contents

A VELOCITY MEASUREMENT METHOD BASED ON SCALING PARAMETER ESTIMATION OF A CHAOTIC SYSTEM

Lidong Liu, Jifeng Hu, Zishu He, Chunlin Han, Huiyong Li, Jun Li

School of Electronic Engineering, University of Electronic Science and Technology of China, Chengdu, 611731, China, (liulidong_1982@126.com, +86 02861852218, hujinfeng06@tsinghua.org.cn, zshe@uestc.edu.cn)

Abstract
In this paper, we propose a new method of measuring the target velocity by estimating the scaling parameter of a chaos-generating system. First, we derive the relation between the target velocity and the scaling parameter of the chaos-generating system. Then a new method for scaling parameter estimation of the chaotic system is proposed by exploiting the chaotic synchronization property. Finally, numerical simulations show the effectiveness of the proposed method in target velocity measurement.

Keywords: signal processing, parameter estimation, chaos, synchronization

Full paper (PDF, 223kB)

283

contents

DAC TESTING USING MODULATED SIGNALS

Pavel Fexa, Josef Vedral, Jakub Svatoš

CTU Prague, Faculty of Electrical Engineering Department of Measurement, Technicka 2, 16627, Prague 6, Czech Republic (fexap1@fel.cvut.cz, +420 22 435 2201, vedral@fel.cvut.cz, +420 22 435 2182, svatoja1@fel.cvut.cz, +420 22 435 2201)

Abstract
This document analyses qualities of methods used for testing dynamical parameters of Digital-to-Analog Converters (DAC) using a multi-frequency signal. As the source for these signals, Amplitude Modulated (AM) and Frequency Modulated (FM) signals are used. These signals are often used in radio engineering. Results of the tests, like Effective Number of Bits (ENOB), Signal-to-Noise and Distortion (SINAD), are evaluated in the frequency domain and they are compared with standard results of Sine Wave FFT test methods. The aim of this research is firstly to test whether it is possible to test a DAC using modulated signals, secondly to reduce testing time, while estimating band performance of DAC.

Keywords: Digital-to-analog converter, ENOB, Signal-to-noise and distortion - SINAD, FFT analysis, Crest Factor (CF).

Full paper (PDF, 1280kB)

295

contents

COMPARISON OF AMPLITUDE-BASED AND PHASE-BASED METHODS FOR SPEED TRACKING IN APPLICATION TO WIND TURBINES

Jacek Urbanek¹⁾, Tomasz Barszcz¹⁾, Nader Sawalhi²⁾, Robert B. Randall²⁾

1) AGH University of Science and Technology, 30-059 Kraków, Poland (tbarszcz@agh.edu.pl, +48 12 617 3116)
2) University of New South Wales, Sydney 2052, Australia

Abstract
Focus of the vibration expert community shifts more and more towards diagnosing machines subjected to varying rotational speeds and loads. Such machines require order analysis for proper fault detection and identification. In many cases phase markers (tachometers, encoders, etc) are used to help performing the resampling of the vibration signals to remove the speed fluctuations and smearing from the spectrum (order tracking). However, not all machines have the facility to install speed tracking sensors, due to design or cost reasons, and the signal itself has to then be used to extract this information. This paper is focused on the problem of speed tracking in wind turbines, which represent typical situations for speed and load variation. The basic design of a wind turbine is presented. Two main types of speed control i.e. stall and pitch control are presented. The authors have investigated two methods of speed tracking, using information from the signal (without relying on a speed signal). One method is based on extracting a reference signal to use as a tachometer, while the other is phase-based (phase demodulation).Both methods are presented and applied to the vibration data from real wind turbines. The results are compared with each other and with the actual speed data.

Keywords: speed tracking, speed estimation, instantaneous frequency, wind turbines.

Full paper (PDF, 294kB)

305

contents

HEART SEGMENTATION IN ECHO IMAGES

Andrzej Skalski, Paweł Turcza

AGH University of Science and Technology, Faculty of Electrical Engineering, Automatics, Computer Science and Electronics, Department of Measurement and Instrumentation, al. Mickiewicza 30, 30-059 Cracow, Poland. (skalski@agh.edu.pl, turcza@agh.edu.pl, +48 12 617 2828)

Abstract
Cardiovascular system diseases are the major causes of mortality in the world. The most important and widely used tool for assessing the heart state is echocardiography (also abbreviated as ECHO). ECHO images are used e.g. for location of any damage of heart tissues, in calculation of cardiac tissue displacement at any arbitrary point and to derive useful heart parameters like size and shape, cardiac output, ejection fraction, pumping capacity. In this paper, a robust algorithm for heart shape estimation (segmentation) in ECHO images is proposed. It is based on the recently introduced variant of the level set method called level set without edges. This variant takes advantage of the intensity value of area information instead of module of gradient which is typically used. Such approach guarantees stability and correctness of algorithm working on the border between object and background with small absolute value of image gradient. To reassure meaningful results, the image segmentation is proceeded with automatic Region of Interest (ROI) calculation. The main idea of ROI calculations is to receive a triangle-like part of the acquired ECHO image, using linear Hough transform, thresholding and simple mathematics. Additionally, in order to improve the images quality, an anisotropic diffusion filter, before ROI calculation, was used. The proposed method has been tested on real echocardiographic image sequences. Derived results confirm the effectiveness of the presented method.

Keywords: echocardiography, image segmentation, level set method, Hough transform, shape estimation.

Full paper (PDF, 1095kB)

315

contents

HIGHLY ACCURATE CALIBRATION SYSTEM FOR ELECTRONIC INSTRUMENT TRANSFORMERS

Yue Tong¹⁾, Guoxiong Ye¹⁾, Keqin Guo¹⁾, Hongbin Li^1,2)

1) State Grid Electronic Power Research Institut
2) Huazhong University of Science& Technology, Institute of Electrical & Electronic Engineering.Chian (cherry8386@126.com)

Abstract
A high accurate electronic instrument transformer calibration system is introduced in this paper. The system uses the fourth-order convolution window algorithm for the error calculation method. Compared with Fast Fourier Transform, which is recommended by standard IEC-60044-8 (Electronic current transformers), it has higher accuracy. The relative measuring errors caused by asynchronous sampling could be reduced effectively without any special hardware technique adopted. The results show that the ratio error caused by asynchronous sampling can be reduced to 10-4, and the phase error can be reduced to 10-3 degrees when the deviation of frequency is within ±0.5 Hz. The present method of measurement processing is achieved by a high-accuracy USB multifunction data acquisition (DAQ) card and virtual measurement devices, with low cost, short exploitation period and high stability.

Keywords: Electronic instrument transformers, Digital output, Calibration system, Virtual instrument, Fourthorder Convolution Window

Full paper (PDF, 209kB)

323

contents

INDUCTIVE SENSOR FOR WEIGHING OF MASS

Janusz Lewandowski

MENSOR, Węglarska 50, 04-689 Warsaw (mensor@mensor.pl, +48 22 424 33 23)

Abstract
A new method measuring of mass in electronic system of scales has been described. The main element of this system is inductive measuring load cell, which was compared with strain gauge load cell. The aim of the paper is described advantages of the inductive measuring system of mass and explain some main problems of this system. Digital correction of the mechanical errors of the beam like: hysteresis, creep material of the beam under constant load, influence of ambient temperature was described.

Keywords: inductive load cell, electronic scales, measuring system of mass

Full paper (PDF, 676kB)

335

contents

INVESTIGATION OF THE STATISTICAL METHOD OF TIME DELAY ESTIMATION BASED ON CONDITIONAL AVERAGING OF DELAYED SIGNAL

Adam Kowalczyk, Robert Hanus, Anna Szlachta

Rzeszow University of Technology, Dept. of Metrology and Diagnostic Systems, W. Pola 2B, 35-959 Rzeszow, Poland (kowadam@prz.edu.pl, rohan@prz.edu.pl, annasz@prz.edu.pl)

Abstract
This paper presents the results of the theoretical and practical analysis of selected features of the function of conditional average value of the absolute value of delayed signal (CAAV). The results obtained with the CAAV method have been compared with the results obtained by method of cross correlation (CCF), which is often used at the measurements of random signal time delay. The paper is divided into five sections. The first is devoted to a short introduction to the subject of the paper. The model of measured stochastic signals is described in Section 2. The fundamentals of time delay estimation using CCF and CAAV are presented in Section 3. The standard deviations of both functions in their extreme points are evaluated and compared. The results of experimental investigations are discussed in Section 4. Computer simulations were used to evaluate the performance of the CAAV and CCF methods. The signal and the noise were Gaussian random variables, produced by a pseudorandom noise generator. The experimental standard deviations of both functions for the chosen signal to noise ratio (SNR) were obtained and compared. All simulation results were averaged for 1000 independent runs. It should be noted that the experimental results were close to the theoretical values. The conclusions and final remarks were included in Section 5. The authors conclude that the CAAV method described in this paper has less standard deviation in the extreme point than CCF and can be applied to time delay measurement of random signals.

Keywords: time delay estimation, random signals, conditional averaging, cross-correlation

Full paper (PDF, 222kB)