Ing. Jakub Svatoš, Ph.D.

This paper analyses the efficiency of various frequency cepstral coefficients (fCC) in a non-speech application, specifically in classifying acoustic impulse events - gunshots. There are various methods for such event identification available. The majority of these methods are based on time or frequency domain algorithms. However, both of these domains have their limitations and disadvantages. In this article, an fCC, combining the advantages of both frequency and time domains, is presented and analyzed. These originally speech features showed potential not only in speech-related applications but also in other acoustic applications. The comparison of the classification efficiency based on features obtained using four different fCC, namely Mel-frequency Cepstral Coefficients (MFCC), Inverse Mel-frequency Cepstral Coefficients (IMFCC), Linear-frequency Cepstral Coefficients (LFCC), and Gammatone-frequency Cepstral Coefficients (GTCC) is presented. An optimal frame length for an fCC calculation is also explored. Various gunshots from short guns and rifle guns of different calibers and multiple acoustic impulse events, similar to the gunshots, to represent false alarms are used. More than six hundred acoustic events records have been acquired and used for training and validation of two designed classifiers, Support Vector Machine, and Neural Network. Accuracy, Recall and Matthew's correlation coefficient measure the classification success rate. The results reveal the superiority of GFCC to other analyzed methods.

The article introduces possible issue of internal CMOS SAR microcontroller's ADC input currents. It describes a nature of the ADC input current and its dependence on a sampling frequency. Methods for measurement of parameters such as input charge, residual voltage, and equivalent capacitance of sample-hold circuits are presented and used in the proposed simplified model of ADC input behavior. These parameters, which are not listed in datasheets, if not respected in data acquisition designs, can adversely affect how the ADC is used when measuring signal sources with nonnegligible internal resistance. The article also explains how to solve a voltage measurement on a source with high internal resistance even in a situation where, according to datasheets, it should already have limitations. The proposed simplified CMOS SAR ADC input behavior model in an MCU can help users in MCU-based data acquisition system design.

The contribution introduces the possible issue of internal CMOS Successive Approximation Register microcontroller's Analog-to-Digital Converters input currents. If the microcontroller also contains a multiplexer, it can lead to consequences caused by the sample-and-hold block that is part of a charge redistribution Analog-to-Digital Converter. The article presents its nature, the possibility of its measurement, and a simplified model of such an MCU analog inputs behavior. The simplified model and derived formulas can help the unacquainted user in a data acquisition system with the MCU design when measuring signal sources with non-negligible internal resistance. The introduced parameters, which cannot be found in datasheets, can be essential for users.

The paper describes the utilization of high-speed Equivalent-Time Sampling (ETS) in Software-Defined Instruments used for virtual instrumentation - typically oscilloscopes. With the increasing performance and expansion of peripherals of microcontrollers (MCU), it is possible to realize measuring instruments only with MCU itself. A solution to MCUs' Analog-to-Digital Converter (ADC) maximal sampling frequency limitations in digitizing quick transient responses is presented. The principle of ETS with all derived equations is discussed and explained, as well as the ADC input model and real properties of software-defined oscilloscope from an ETS point of view. All the ideas are practically verified on different MCUs (Raspberry PI PICO, STM32, Arduino). The use of ETS for circuit behavior analysis where an MCU with internal peripherals (generator with pulse-width modulation and ADC) is used for a test signal generation and data digitization may increase the equivalent sampling rate of the internal ADC up to tens of MSa/s.

To point out dangerous events is more and more necessary not only in military applications but also in civil areas. In hazardous situations, to detect, localize, and classify a source of danger (e.g., gunshot), an automatic acoustic measurement detection system may be preferable in favor of visual detection. This paper presents an automatic acoustic system that can detect, localize and classify acoustic impulse events, such as gunshots. The presented system is based on standalone units, which continuously monitor its surrounding. If an acoustic event is detected, an algorithm based on Mel Frequency Transformation and classification using a Support Vector Machine is performed. If the gunshot is recognized, the system calculates, using the Levenberg-Marquardt iterative solution algorithm, the exact location of the event and can estimate the caliber of the used firearm. The detection system is designed to monitor the surroundings around objects of interest, like campuses, hospitals, or public areas. The system has been tested by .22, 6.35 mm, 7,65 mm, and 9 mm short guns, and .22, 5.56 NATO, and 7.62 mm rifle guns with various subsonic and supersonic ammunition. The sets of diverse impulse acoustic events, like different slams, glass breaking, dog barking, or similar, have been used to train the classifier to avoid false alarms. The presented acoustic system can reliably detect, localize and classify hazardous acoustic events.

This paper presents the design and modeling of an eddy current speed sensor for nonmagnetic moving rods with an axisymmetric configuration. The sensor consists of two antiserially connected excitation coils and one pick up coil located between two excitation coils. A novel computational approach using the combined finite difference method and Fourier series is proposed for the modeling and simulations of the eddy current speed sensor. The effects of the outer diameters of moving nonmagnetic rods and their electrical conductivities on the performance of speed sensor are originally evaluated. The results of the modeling for the eddy current speed sensor are compared with the measurements at time varying speeds and various frequencies. The comparison between modeling and experimental results shows the appropriateness of the eddy current speed sensor for the speed measurement of nonmagnetic rods.

This article depicts how COVID-19 affected practical teaching at Czech Technical University in Prague, Faculty of Electrical Engineering, Department of Measurement. It introduces the subject of Electrical Measurement and its hands-on laboratory classes. The course applies to more than 100 undergraduate students per semester. Since COVID-19 mainly affected the teaching of the hands-on laboratory courses, the article narrates how the COVID-19 lockdown has changed classes. An experience with the rapid transformation of lectures during the lockdown focusing on the hands-on laboratory classes is discussed, and the improvements that have been done to preserve its objectives, but also to adapt them to another possible lockdown, and the need to switch to the distance teaching, is revealed. The changes have been inspired by the results of a survey carried out among more than 250 students. The outline of the laboratory tasks transformation with an emphasis on the possibility of switching the real face-to-face measurement to the distance teaching remote lectures is described. The change includes reducing the number of laboratory tasks taught while preserving most of the objectives. All 11 new laboratory tasks are described in detail, and it is discussed how the possible change from hands-on to remote classes will affect every task.

The paper describes the Equivalent-Time Sampling (ETS) in Software-Defined Instruments (SDI) - typically oscilloscopes. It introduces a possible solution of the microcontrollers drawback caused by the maximal sampling frequency and its limitations in digitizing quick transient responses. The principle of ETS used in microcontrollers is explained, and the jitter effect is taken into account. Analog-to-digital converter input model and real properties of software-defined oscilloscope from ETS point of view are introduced and explained. In the system for circuit behavior analysis as a step response, where a microcontroller with internal peripherals (pulse-width modulation and analog-to-digital converter) is used for a test signal generation and data digitization, the use of ETS may increase the equivalent sampling rate of the internal analog-to-digital converter up to tens of MSa/s.

COVID -19 pandemic and its restrictions bring new challenges to all aspects and phases of higher education. At universities, new remote formats have been developed and deployed for lectures and laboratory exercises. This article addresses challenges and introduces the new experience with lectures and laboratory classes during the pandemic time at the Department of Measurement of the Czech Technical University in Prague, Faculty of Electrical Engineering. Based on the student survey of more than 250 students describes the possibilities of how to adapt the lectures during the lockdown. The article also introduces the Home Lab, a tool developed in the department that helps in distance teaching practical electronic classes. Home Lab includes two parts with functional groups, a Laboratory Experimental Device and a System of Measurement Instruments. The article also shows the opportunity for suitable remote exercises and variants of circuits that can be easily assembled and measured using Software Defined Instrument based on various microcontrollers. A detailed description of all Software Defined Instruments is also present. During the Pandemic, the home lab model was successfully practically verified during distance learning in three subjects, with more than 150 students per semester. It has also been shown that the Home Lab can be successfully deployed for a semester project. The article also presents experience with the teaching software-oriented courses. At the end of the article, practical knowledge and an experience from distance teaching during a three-semester lockdown are shared.

This paper presents a way to calculate the shell thickness of nonmagnetic hollow cylinders for nondestructive applications. Aluminum cylinders with a solid structure and with a hollow structure are considered. The motion component of the induced eddy currents in a conductive cylinder is utilized to evaluate the shell thickness of hollow conductive cylinders at various frequencies and at variable speeds. One axisymmetric excitation coil and two axisymmetric pickup coils with antiserial connection are used. An analytical method using an axisymmetric computational model is developed for a parametric analysis of solid and hollow cylinder structures and shell thickness calculations, in which Fourier series are utilized. A 2D axisymmetric finite element method is also performed for a comparison with the results of the analytical method. The measurements at variable speeds and at various frequencies are presented with various hollow aluminum cylinders. The high linearity of the induced voltage versus the speed curve makes it possible to calculate the shell thickness of nonmagnetic hollow cylinders at different speeds.

Covid-19 related restrictions bring new challenges to all aspects and phases of higher education. At universities, new remote formats are deployed or even developed both for lectures and laboratory exercises. This article addresses new challenges and describes the experience with lessons during the pandemic time at the Department of Measurement of the Czech Technical University in Prague, Faculty of Electrical Engineering. It introduces the best practices exercised using the Home Lab, which helps in distance teaching of practical electronic classes. Home Lab includes two models with functional groups, a Laboratory Experimental Device and System of Measurement Instruments. The article also shows the possibilities of suitable remote exercises and variants of circuits that can be easily assembled and measured using Software Defined Instrument based on STM microcontrollers. During the pandemic, the home lab model was successfully practically verified during distance learning in three classes, with more than 150 students. The article also presents experience with the teaching of software-oriented courses. At first glance, their transformation can be viewed as straightforward. However, practical realization reveals few remarkable details.

The COVID-19 pandemic dramatically changed or even temporarily stopped teaching at many universities overnight. This situation was especially challenging for technical universities with a lot of practical activities and laboratory exercises, as it required the creation of a stable and full-fledged online education system. Everything that has taken place so far in the form of direct contact, from lectures, seminars, practical demonstrations, and laboratory exercises, through written tests to oral exams, had to be digitized, not to mention other legal and administrative processes for teaching. A significant advantage of FEE CTU was that the vast majority of teachers already had previous experience in providing online education and had a number of tools that could be used for this purpose. However, the rapid transition from full-time to distance learning required a reassessment of the concept of teaching organization and the provision of a number of related activities, especially in the field of communication, planning of educational activities and selection of appropriate methods.

At present, acoustic detection techniques of gunshots (gunshot detection and its classification) are increasingly being used not only for military applications but also for civilian purposes. Detection, localization, and classification of a dangerous event such as gunshots employing acoustic detection is a perspective alternative to visual detection, which is commonly used. In certain situations, to detect and localize a source of a gunshot, an automatic acoustic detection system, which can classify the caliber, may be preferable. This paper presents a system for acoustic detection, which can detect, localize and classify acoustic events such as gunshots. The system has been tested in open and closed shooting ranges and tested firearms are 9 mm short gun, 6.35 mm short gun, .22 short gun, and .22 rifle gun with various subsonic and supersonic ammunition. As “false alarms,” sets of different impulse acoustic events like door slams, breaking glass, etc. have been used. Localization and classification algorithms are also introduced. To successfully classify the tested acoustic signals, Continuous Wavelet and Mel Frequency Transformation methods have been used for the signal processing, and the fully two-layer connected neural network has been implemented. The results show that the acoustic detector can be used for reliable gunshot detection, localization, and classification.

To reduce the construction costs and to increase energy savings and the indoor environmental quality in a woodhouse, an energy consumption measuring system for diagnostics of thermal and technical properties of buildings envelope has been developed. At present, vast majority of calculations for the thermal and technical characteristics of buildings are based on simple mathematical models of building envelope behavior derived primarily from the thermal transmittance of individual materials. However, the thermal transmittance is measured in a stable laboratory environment. Therefore, the measured values may not match the real behavior of materials in continually changing climatic conditions. The Energy Consumption Measuring System has been installed to seven woodhouses in different climatic areas to diagnose the thermal and technical properties of a buildings envelope. The power consumption, temperature, and humidity of the air and of the wood, CO2 concentration, temperature of the individual layers of the envelope sandwich structure, and wind speed and direction are measured. Thanks to the sets of real measurements of the thermal and technical behavior, the actual dependence of the indoor environment quality on the outdoor climatic conditions can be obtained. The presented system can reveal imperfections in heat capacity and hygroscopicity of materials used for construction of a woodhouse. Based on this measurement, the materials can be revised to save the construction costs, energy savings, and to increase the indoor environment quality, together with environment impact reduction.

The book describes circuit devices and methods of analog signal processing from typical sensors of physical quantities and means for their digitization and reconstruction including description of selected methods of their digital processing. The book is supplemented with practical principles of construction of analog-digital systems in terms of the transmission and isolation of analog signals, the method of printed circuit design, the elimination of interfering signals, the method of power supply and grounding of circuits. It also contains examples of simulations of these circuits in time and frequency domain in MULTISIM program.

At present, acoustic detection techniques of gunshots (gunshot detection) are increasingly being used not only for military applications but also for civilian purposes. Detection, localization, and classification of gunshots employing acoustic detection is perspective alternative to visual detection, which is commonly used. In certain situations, to detect a source of a gunshot, an automatic acoustic detection system may be preferable. This paper presents a system for acoustic detection, which can detect localize and classify acoustic events such as gunshots. Tested firearms are 9 mm short gun, 6.35 mm short gun, .22 short gun, and .22 rifle gun with various subsonic and supersonic ammunition. As “false alarms,” sets of different impulse acoustic events like door slams, breaking glass, etc. have been used. To successfully classify the tested acoustic signals, Continuous Wavelet and Mel Frequency Transformation methods have been used for the signal processing, and the fully two-layer connected neural network has been implemented. The results show that the acoustic detector can be used for reliable gunshot detection, localization, and classification.

Currently, detection techniques for acoustic pulse signals (detection of gunshots) are increasingly used not only for military applications but also for civilian purposes. With increasing attacks in schools, campuses, shopping malls, or hospitals, there is a requirement for automatic gunshot detection by other methods than camera systems in conjunction with the operator. Localization and classification of gunshots using acoustic detection are, therefore, becoming important for the safety of the population.

With an increasing number of wearable devices of all shapes and forms, which are equipped with new types of sensors to count steps, measure heart rate or even detect a fall, there is a requirement for more energy. Energy harvesting is one of the possible ways to increase the energy capability of such devices. The solar cells offer a renewable green source of energy to increase the power of wearable devices. At present, there is no binding uniform methodology for Solar Cell characterization under real light conditions of everyday life. The article presents a daily generation of energy in various daily life activity such as walking, car driving or office working with indoor illuminating. The solar cell, working in Maximum Power Point Tracking, attached to the hand of the person has been used. The presented results show expected amounts of generated energy in everyday life activities, which could be used for a better characterization of solar cells in the future.

The proposed laboratory exercise is focused on the measurement of indoor environment quality (temperature, humidity, CO2 concentration) using digital measurement system based on Modbus protocol. Students acquire practical knowledge and general principles of the Modbus protocol, configuration and communication principles of smart sensors and measurement of temperature, humidity, CO2 concentration together with power consumption. The benefit for students in comparison with the old task is the improved quality of the laboratory task in the area of measurement circuits and fieldbus communication with the focus on industrial application.

To automatically detect dangerous situations in public areas, systems based on visual detection are the most commonly used. In certain situations, to detect a source of danger, an automatic acoustic detection system may be preferable. This paper presents a smart acoustic sensor system, which automatically detects acoustic pulse events, such as gunshots, in public places, and localizes the position of the acoustic source. Tested firearms are 9 mm short gun, 6.35 mm short gun, .22 short gun with various subsonic and supersonic ammunition. Various sounds like door slams, human screams, etc. represent false alarms.

With an increasing number of wearable devices of all shapes and forms, which are equipped with new types of sensors to count steps, measure heart rate or even detect a fall, there is a requirement for more energy. Energy harvesting is one of the possible ways to increase the energy capability of such devices. The solar cells offer a renewable green source of energy to increase the power of wearable devices. At present, there is no binding uniform methodology for Solar Cell characterization under real light conditions of everyday life. The article presents a daily generation of energy in various daily life activity such as walking, car driving or office working with indoor illuminating. The solar cell, working in Maximum Power Point Tracking, attached to the hand of the person has been used. The presented results show expected amounts of generated energy in everyday life activities, which could be used for a better characterization of solar cells in the future.

To reduce the construction costs and to increase energy savings and the indoor environmental quality in a woodhouse, an energy consumption measuring system for diagnostics of thermal and technical properties of buildings envelope is introduced. At present, the vast majority of calculations for the thermal and technical characteristics of buildings are based on simple mathematical models of building envelope behaviour derived primarily from the thermal conductivity of individual materials. However, the thermal conductivity is measured in a stable laboratory environment. Therefore, the measured values may not match the real behaviour of materials in continually changing climatic conditions. The Energy Consumption Measuring System has been installed to eight woodhouses in different climatic areas to diagnose the thermal and technical properties of buildings envelope. The power consumption, temperature, and humidity of the air and of the wood, CO2 concentration, temperature of the individual layers of the envelope sandwich structure and wind speed and direction are measured. Thanks to the sets of real measurements of the thermal and technical behaviour, the actual dependence of the indoor environment quality on the outdoor climatic conditions are obtained.

At present, acoustic pulse detection techniques, or gunshot detection, are used not only in military applications, but also in civilian areas such as gunshot detection in schools, campuses, shopping centers, or hospitals. Shooting detection, localization and classification is becoming increasingly important in terms of population safety.

A limited ability to discriminate between different materials is a fundamental problem with all conventional eddy current based metal detectors. This article presents the use, evaluation and classification of non-traditional excitation signals for eddy current metal detectors to improve its detection and discrimination ability. The presented multi-frequency excitation signals are the following: a step sweep sine wave, a linear frequency sweep and sin(x)/x signals. All signals are evaluated in a frequency domain. An amplitude and a phase spectra and polar graphs of a detector output signal are used for a classification and discrimination of the tested objects. Four different classifiers are presented. The comparison of classification results of polyharmonic signals with the classical single tone method is also shown. Multi-frequency signals offer more detailed information, due to response function – the frequency characteristic of a detected object, than the application of standard single tone methods. Based on the measurements and analysis, a metal object can be better distinguished than when using the single tone method.

The book describes methods of analogue signal processing and its digitization in measuring technology. Electric circuit for analogue signal processing of typical physical quantities measured by sensors as well as circuits for its digitization and reconstruction are described. The book also include a description of selected methods of digital signal processing, allowing to increase the metrological properties of the measuring chain. The book is supplemented by practical principles of the design of analogue and digital systems consideration of transmission and isolation of analogue signals, methods of linking, power supply and grounding of circuits and printed circuit design.

The paper describes application of polyharmonic sinc signals in devices for metal object detection. A basic problem of conventional eddy current metal detectors (induction devices in general) lies in its limited possibilities of discrimination or identification of detected objects. To better characterize the detected object, the excitation signal and the following signal processing in the detector should be done. Application of polyharmonic excitation signal and its processing could bring an opportunity to improve the determination ability. The article is focused to the polyharmonic sinc signal. Spheres of different diameters and from different ferrous and non-ferrous materials were used as specimens. Experimental measurements were processed in frequency domain - amplitude and phase spectra were calculated and presented. As part of the work, classifications of ferrous and non-ferrous materials were done based of measured data as well as classification of individual ferrous including non-ferrous materials and estimation of the size of the classified object. Support vector classifier was primarily used for data classification.

This paper describes the application and time domain signal processing of polyharmonic sinc function as an excitation signal for eddy current metal detectors. Limitations of all conventional eddy current metal detectors or induction devices in general reside in its limited ability to discriminate or unequivocally identify detected materials. To better identify or classify materials, the excitation signal and its following processing in the detector should be done. The paper is focused on the processing of the polyharmonic sinc signal in the time domain in order to improve the discrimination ability into ferromagnetic and non-ferromagnetic materials. Processing of polyharmonic signal in time domain bring a fast and undemanding method. Spheres of different diameters and from different ferromagnetic and nonferromagnetic materials were used as specimens. Experimental measurements were processed in time domain only – standard integral parameters of the signal were used for target identification.

This paper describes the design of a measuring chain for polyharmonic metal detectors used for education in laboratory exercises at Czech Technical University in Prague, Faculty of Electrical Engineering, Department of Measurement. The Measuring chain is composed of DDS signal generator, Digitiser and PC with software programmed in Labview. Eddy current principles or more specifically eddy current metal detectors are an important part of nondestructive testing, instrumentations and measurement. A short introduction to the background and principles of eddy current metal detectors are presented. Next part of the article deals with a brief description of the most common methods, as well as, non-traditional polyharmonic methods for eddy current metal detection. The following part contains an implementation of the proposed algorithms in LabVIEW graphical programming language. Finally, the created program for education of eddy current metal detectors and results obtained on the metal detector ATMID are discussed.

This article deals with usage of polyharmonic signals to metal detection and discrimination. A substantial problem of all conventional eddy current metal detectors (induction devices at general) is in limited possibilities of identification of detected objects. The excitation signal and signal processing in the detector should be done in a way to better characterize the detected object. Usage of polyharmonic excitation signal and processing of the signal brings an opportunity to improve the detection ability. Suitable polyharmonic excitation signal is sin(x)/x – sinc signal. Experimental measurements were processed in frequency domain using Discrete Fourier Transformation. Amplitude and phase spectra together with polar graphs are presented. As experimental targets different ferromagnetic and non-ferromagnetic materials were used.

Humanitarian demining is a matter of high interest, but metal contamination and magnetic soils reduce the sensitivity of metal detectors. The soil contamination also increases the numbers of false alarms which, in some areas, account for as much as 99.9 % of all alarms. The decrease of false alarms is therefore attractive. Our solution is capable to be adapted and utilized with current professional metal detectors. Essentially it consists of several modules with modular structure, where the master module is always necessary in all applications and the navigation module has to be connected in cases where position estimation is required. Searching part of the detector is able to work in continuous wave mode with variable excitation signal and the possibility to utilize more carrier frequencies. Furthermore, the modular structure can use different search heads available on the market as well as heads developed for special purposes. The modular metal and mine detector described is capable to detect not only unexploded ordnance and explosive remnants of wars, but also pipes and wires in walls and floors indoor which is useful property during not only buildings reconstructions.

The paper shows application of non-traditional excitation signal Sinc for metal detection and discrimination of detected objects. It also briefly describes characterization of Sinc signal. Head of the All Terrain Mine Detector is used for experiment. Various spheres from different materials and with different diameters were placed in non-magnetic platform in the open air as a test target. Signal was processed in frequency domain. Spectra graphs are presented to differentiate between the different objects. On the basis of these graphs, better identification and discrimination between these objects (i.e. Anti-Personnel mines or UXO) could be done.

This paper presents usage of an unusual signal (sinc signal) for metal detection and discrimination. Even in present days, differentiate between Anti-Personnel (AP) mine or unexploded ordnance (UXO) and metal garbage is a matter of high interest for scientists. In some areas, especially with contaminated or magnetic soil, 999 form 1000 alarms are false. Decrease of these false alarms is enticing and necessary in umanitarian demining. For the experiment Schiebel All-Terrain Mine Detector with testing spheres from different materials and different sizes were used. Signal from the detector was processed in frequency domain, especially phase spectra are shown and compared.

This paper describes three different possibilities how to detect and distinguish between different metal garbage and mine (especially Anti-Personnel mines - AP) or UXO unexploded ordnance). A comparison of three unconventional excitation polyharmonic signals for an eddy current metal detector is presented. These signals are linear frequency sweep sinusoidal, step sweep sinusoidal, and sinc signals. Thanks to this we obtained a frequency characteristic of a detected object over a wide range of frequencies and obtained more detailed view about object than with classical methods. Amplitude and phase spectra, polar graphs as well as real and imaginary parts ot detector signal output are presented. Based on the measurements and the analyses, the distinguishing between different objects can be done in terms of the electromagnetic properties (conductivity and permeability). Polar graphs could be used for an object’s interpretation and for the manual discrimination.

The usage of frequency swept signals for an eddy current metal detector is described in this paper. The main task for researchers is to minimize false alarms which account for up to 99.9 % of the total alarms. Better discrimination should be performed to distinguish between mine and scrap metals. Firstly, a short theoretical background is presented. Secondly, experimental data measured by the search head of the metal detector ATMID is presented. The detector was excited with frequency swept sine signals from 1 kHz to 45 kHz. Synchronous demodulation was used for signal processing. Various spheres from different materials and sizes placed in the open air were used as the test targets. A grenade, without explosives, was also presented for comparison. Amplitude and phase graphs or polar graphs are presented to differentiate between the different objects.

This document analyses qualities of methods for testing dynamical parameters of Digital to Analog (D/A) converters using 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 frequency domain and they are compared with standard results of Sin Wave FFT test methods.

This paper describes theoretical background of electromagnetic induction from metal objects modeling. Response function of specific case of the object`s shape - the homogenous sphere for ferromagnetic and non-ferromagnetic material is introduced. Experimental data measured by metal detector excited with Polyharmonic signal are presented. These results should lead to better identification of the buried object. As a testing target various spheres from different materials and sizes were used.

In this paper there are presented methods for testing dynamic parameters DA converters with multi-tone signals. Results of this test with discrete multi-tone signals and equivalent amplitudes, AM and FM signals compared with standard test with Single-Tone Fourier Test.

In this paper the qualities of methods for testing dynamical parameters of A/D converters with analog frequency modulated and quadrature modulated signals are analyzed. Results of test are compared with standard Single-Tone Fourier Transform Test.

In this paper theoretical background of electromagnetic induction modeling is presented. Response function of specific case of the shape - homogenous sphere for ferromagnetic and non-ferromagnetic is introduced. Some experimental data measured on metal detector excited by Polyharmonic signal are also presented.

In this paper qualities of methods for testing dynamical parameters of A/D converters with poly-harmonics signals are analyzed. As source for these signals amplitude and frequency modulation signals are used. These signals are often used in radio engineering. Results of test in time and frequency domain (Effective Number of Bits, Total Harmonic Distortion, Signal Non-harmonic Distortion, Spurious Free Dynamic Range, and Intermodulation Distortion) are compared with standard results of Sin Wave Fit and FFT test methods.

This paper is to show the methods of dynamic parameters testing of high quality audio codec with 24 bits nominal resolution. In the paper are briefly the best Sine Wave Fit Test, Spectral Purity Test and Noise Histogram Test presented. The above mentioned testing methods are then used for testing of these ADCs and obtained data are discussed.

This paper describes two methods for economical test of dynamic parameters ADCs in embedded Data Acquisition Systems. First method is Exponential Fit Test, second method is Wobbler Test. Common testing methods are mentioned as far the accuracy and time necessary for the complete test are concerned. The tests for fast evaluation of the dependence of an effective number of bits on frequency of input signal are described and the comparison of proposed method with the standard methods is given.

In this paper is presented the Sine Wave Fit Test, Spectral Purity Test and Noise Histogram Test methods for testing of dynamic parameters audio codec with 24 bits nominal resolution. In frequency range 20 Hz to 20 kHz was determine Effective Number of Bits 14,4, Signal Noise and Distortion 89 dB and Total Harmonic Distortion 110 dB.

In the paper are stated methods of education of electronic measurement circuits at Department of Measurement of FEE CTU in Prague. There are specified typically themes applied in bachelor and master grade of study. The education is supported by the set of electronic function units, universal laboratory units LABORO and simulation program MULTISIM.

This paper describes two methods for economical test of dynamic parameters ADCs. First method is Exponential Fit Test, second method is Wobbler Test. Common testing methods are mentioned as far the accuracy and time necessary for the complete test are concerned. The tests for fast evaluation of the dependence of an effective number of bits on frequency of input signal are described and the comparison of proposed method with the standard methods is given. The suitable area of proposed method application is "each-piece" factory testing requiring extremely short time testing.

In the paper are stated methods of education electronic measurement circuits at Department of Measurement of FEE CTU in Prague. There are specified typically themes applied in bachelor and master grade of study. The education is supported by the set of electronic function units, universal laboratory units LABORO and simulation program MULTISIM.