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This paper presents a method for mapping and analysis of electromagnetic background in an urban area. The uniqueness of our environment causes the inability to simulate electromagnetic fields of the real world as there is an unknown amount of sources and a near infinite amount of obstacles that could obscure the traveling wave or bounce it in a different direction altogether. The proposed method allows mapping an area of 64 hectares in less than 24 hours using only one person, antenna, software-defined radio, laptop, and optionally external drive to store data, which ensures the possibility of having multiple setups to multiply results. The general analysis of gathered data consists of three parts. The first is the compression ratio, a valuable byproduct of data compression for long-term storage. The second uses geographical locations to determine variance by distance, in a straight line and a cluster. The final tool for analysis is a Pearson's and Kendall's correlations to a baseline measurement to find potential errors and/or anomalies within a data set.

Electromagnetic compatibility is a significant problem for electronic system developers, especially cabling, which is often the weakest link of the assembly, therefore a bigger emphasis is put on its securing. Recently, a significant progress has been achieved in synthetic electromagnetically lossy materials. Therefore, new cable designs using these cable sheath materials can be soon expected both in applied research and in development. At the same time, reliable measurements of such shielding effectiveness are needed, especially in terms of the far field. While most publications about synthetic electromagnetic lossy materials deal with their measurement via coaxial transmission lines (the ASTM method), far-field measurements have not been sufficiently discussed. In this paper, several phenomena related to this topic are discussed, further, an experiment testing two different cable specimens is realized and the results are compared. The paper discusses fundamental issues of far EM field generated by power supply cables fed by radio frequency interferences.

The power frequency magnetic field immunity test is a common test applied to a large variety of devices that must be checked for electromagnetic compatibility. Implementing this test is not difficult since it involves working with frequencies at which the generated magnetic field can be considered quasi-stationary. Considering the high price level of devices intended for use in electromagnetic compatibility laboratories, it may be worth contemplating assembling the equipment for this test on one's own. This paper includes a discussion on the requirements given by the relevant standards and their implications for the design of the test signal generator. Additionally, a complete design process for such equipment is provided, along with a discussion on the possibility of further improvements. The design of the test coil is adapted to allow its excitation from a powerful low-frequency amplifier, which opens up possibilities for the use of more advanced drivers. However, the test coil can also be powered using a normal mains transformer, simplifying the design of the entire device

This paper discusses the use of the terrestrial multi-frame photogrammetry method. This method is applied to a group of plants in a natural environment of a greenhouse. Image data is captured by two sensing devices with different types of lenses. Image data is used for the realistic 3D reconstruction of objects into a 3D model. In this experiment, we work primarily with the created point cloud.

This paper describes a voltage controlled amplifier with linearized response to the controlling voltage and discusses its harmonic distortion. As a controlling element, a JFET transistor has been utilized. The design of the amplifier has been made with the aid of Maple mathematical software and National Instruments Multisim circuit simulator. During the simulations, it was found that the controlling transistor would probably introduce significant distortion into the signal path. Therefore a set of measurements on real circuit was made in order to verify that the SPICE model of the transistor provided relevant results during the simulation. Both, the simulated and the really measured parameters of the amplifier are discussed within the framework of this paper. ©2020 IEEE

The paper describes electronic vibration monitoring module (EVM) that can be used as standalone diagnostic system or as a part of a complex modular concept of engine electronic control (EEC/FADEC) with aircraft health monitoring system. We present a new generation of EVM for modern small turboprop engines and their vibration diagnostics which has been developed by Unis, a.s. in cooperation with Brno University of Technology and Tomas Bata University in Zlin. © 2020 University of West Bohemia.

The paper aims at the investigation of a liquid electrolyte effect on electromagnetic radiation. The liquid electrolyte could represent an interesting solution against electromagnetic interference for devices using transparent covers, such as security cameras. Currently, the way how to protect transparent areas is a fine metallic grid or polymer material; however, this solution could reduce the transparency through the protected part. The paper describes different types of electrolytes and compares their shielding effectiveness. The experiment includes a plastic packing, metallic electrodes, liquids, laboratory power supply, a coaxial transmission line with receiving and transmitting conductors, source of electromagnetic radiation, and test receiver. The liquid consists of weak and strong acids and bases, such as acetic acid, sulfuric acid or sodium chloride which have different conductivity. There are also various materials for electrodes affecting the conductivity and consequently, the ability of the electrolyte to eliminate the effects of electromagnetic interference. The kind of electrode affects the amount of received and delivered ions between anode and cathode. Shielding effectiveness of electrolyte depends on more unstable parameters compared to conventional metal materials. Temperature and concentration of solution affect the electrolyte conductivity; thereby, the reproducibility could be problematic. Strong electrolytes initially have a rapid increase in conductivity; however, high amounts of ions cause their interaction and decrease in conductivity. Weak electrolytes have a similar course, but the conductivity achieves many times lower values. Measurement is provided according to the ASTM D4935 methods, and it involves a discontinued inner and flanged outer conductor. Samples and the conductors are isolated from external sources of electromagnetic interference by special absorbent materials. The conclusion describes the contribution of the paper. © 2019 I

Active filters based on RC components together with operational amplifiers are quite common functional blocks to be met across different branches of electronics design. During the past, their topology has settled on several well-known and effective solutions. As an example, Sallen-Key or Multiple Feedback topology can be named. The designers can find a huge number of “cookbooks”. According to them they can find help with designing their filters. However, the theory described in these cookbooks usually fits ideal operational amplifiers in a good manner, but, unfortunately, the real parameters of the operational amplifiers may spoil the real behaviour of the design significantly. This problem occurs especially at very high frequencies that are typical for injection of electromagnetic interferences into low frequency signal lines. The authors of this paper have tested several antialiasing (low-pass) filter designs and provide results of measurement at real filters compared to the simulations. Moreover, they provide a discussion on why the results of the simulation do not fit the real behaviour of the filters and suggest improvements in the design of the low pass filters in that way so their utility value was improved. © 2019, Danube Adria Association for Automation and Manufacturing, DAAAM. All rights reserved.

Currently, shielding effectiveness represents a fundamental property of materials designed to resist electromagnetic fields effect. There are many materials suitable for shielding; however, the authors decided to use recyclable plastic materials whose surface was provided with gold or carbon nano-layer. The experiment aimed at determining the influence of conductive material nano-layers and application to commercially available security products.

In recent years, electromagnetic interference has become a severe problem for electronic and electric devices design. That has led to an increase in demand for electromagnetic protection. However, there still exists a lot of devices sensitive to electromagnetic field effect, and one of them is security camera representing a crucial factor in the security area. The paper deals with the design of electromagnetically shielding grid for security cameras lenses. The basis of the experiment is the CST Microwave Studio simulation tool used to obtain the theoretical shielding effectiveness results which are subsequently verified by practical measurements using coaxial lines. © 2018 IEEE.

Electromagnetic interference has become a severe problem for electronic and electrical devices, especially for security cameras which are significantly sensitive to electromagnetic field effects. Therefore, there was born an idea to create shielding enclosure which protects these devices against the radiated field. This task was realized by the evolutionary algorithm included in the computational process of optimizing shielding effectiveness. © 2018 IEEE.

This document provides real data obtained inside the semi anechoic room Frankonia SAC 3 plus that is certified for measurement of electromagnetic interferences and performing of electromagnetic susceptibility tests in the range from 30 MHz up to 18 GHz. The hereby presented data describe the response of the semi anechoic room to the electric field driven inside. The frequency range of the experiment was from 10 MHz to 80 MHz where the standing waves are most likely to occur. © 2018 The Authors

Radiation patterns of antennas are among their most important characteristics. A popular method to obtain these consists in measurements inside anechoic chambers. However, in common engineering practice, small laboratories are usually equipped with only one shielded chamber. Such chambers are basically semi anechoic, providing a possibility of their modification to a fully anechoic version by placing appropriate absorbers on their reflective floor. Unfortunately, the systematic placement of absorbers on the floor of the chamber and their re-extraction increases the laboratory operating costs as it is time consuming and, moreover, there is a risk of mechanical wear or damage of the absorbers. Therefore, the authors of this paper decided to explore how great the impact of absorbers placed on the floor of the semi anechoic chamber is in case of measurement of radiation patterns of antennas operating at frequencies of 1 GHz and higher. Description of the experiment and its results are provided within the framework of this paper. © Published under licence by IOP Publishing Ltd.

The article presents a brief insight into the university research of efficient methods aimed at revealing counterfeit electronic components. Methods like multichannel curve tracing, component internal structure X-raying, system on chip optical inspection with higher magnification microscopy and Scanning Electron Microscopy combined with Element Energy Dispersive Spectroscopy (EDS) are powerful means for authenticity verification. Comparative analysis results serve as an illustration of cases where various features differences can warn not to let a particular component delivery penetrate the assembly process. © 2018 Institute of Physics Publishing. All rights reserved.

Electromagnetic interference has become a major problem for the design of electronic and electric devices, especially security device, where the great emphasis is placed on the reliability. Currently, the boxes of security device are mostly produced using plastic material. However, this material is not able to protect devices against electromagnetic interference, and this leads to efforts to find new ways and materials suitable for protecting the devices. In addition to the electromagnetic immunity requirements, the weight and ductility of the material must take into account. One of the variant how to protect equipment describes this paper focusing on the combination of a commercially available product and nano-layers of gold. The commercial product consists of rubber and ferrite. The advantage of this variant is material flexibility and relatively satisfying resistance to electromagnetic interference. The combining different types of materials can increase the electromagnetic immunity; however, it can lead to an increase in the weight of the final product or a worsening of the ability to model the material as needed. The fundamental structural element of the design was a commercial material combining rubber and ferrite, the structure of which the layer of gold was applied which is expensive but electrically conductive and presents an interesting aesthetic variation. The composite material was tested in the frequency range from 10 MHz up to 2 GHz which is the range corresponding to the European standards. The purpose of the paper is to determine the effect of the composite materials regarding electromagnetic immunity. © 2018 Electromagnetics Academy. All rights reserved.

Immunity tests to radiated electromagnetic field are one of the most common tests performed within the framework of the electromagnetic compatibility. These tests are performed inside a shielded chamber provided the requirements given by the appropriate standards are kept. As the levels of the generated fields can be high and the output power of the transmitting amplifiers cannot be infinite, it is necessary to achieve a good performance of the transmitting antenna. By means of the real experiment the author of this paper shows how the height of the antenna placed above the conductive floor can affect the antenna’s voltage standing waves ratio and how this phenomenon affects the parameters of the whole measurement system. © Springer International Publishing AG 2018.

Class-D audio amplifiers seem to be a perspective way of development of electronics as they can obtain excellent power efficiency together with good performance characteristics. Moreover, they can be easily integrated on a single chip, resulting in clear, comprehensive and non-reckless construction of the audio amplifier. Because the power efficiency is considerably high, some designs even do not need any heat sink, since the heat dissipation can be fully provided by the chip package. In this paper a construction of such an amplifier, being based on the integrated circuit TPA3122, is described. This construction has been developed at Tomas Bata University in Zlin, using conventional component base. Moreover, the paper provides a comparison of the measured performance of the amplifier to the theoretical values provided by the manufacturer of the chip. © 2018, Danube Adria Association for Automation and Manufacturing, DAAAM. All rights reserved.

Perception of image perceptions is one of the most important features of every person. With the help of our eyesight, we can perceive the world around us, acquiring information about our surroundings and recognize different objects in them. Thanks to the recipes of our eye, we can capture it clear information and transferred information to the brain where this information is further processed and evaluated. Based on that, we can recognize what we see.The detection of various objects or shapes in an image is a very important element of all operations involving Image Processing. It is not only used in the processing of Medical Imagery data, (e.g. searching for structures in tomographic images); but also, in the Security field, (e.g. access control); as well as in the human sector - i.e. in cameras and cameras, (e.g. face detection, smiles, etc.). This article deals with possible detection methods of objects in images.

High-speed cameras are expanding into science laboratories in many disciplines. For example, they can be used for monitoring of the impact testing course, widely spread in evaluation of materials. Usually, they exhibit a slight delay between the trigger pulse was applied and the recording was started. For many applications, this delay may be critical. The authors of this paper have faced two problems: The need to determine the delay in total and the need to check whether it varies in time or not. Therefore, the hereby described device was designed. It allows measurement of the delay of the camera's start in the range from 1 to 999 ms with the step of 0.1 ms. © 2017 IEEE.

As the importance of wireless networks based on radio frequencies increases in time, a space for discussion on harmfulness of the electromagnetic radiation has occurred. On the one hand there are studies showing that a direct influence of non-ionizing electromagnetic waves on the human organism was not confirmed until a certain intensity has been reached. On the other hand, critical voices appear, warning that even low intensities of non-ionizing electromagnetic fields are harmful to the human body, if it is exposed to the radiation for a prolonged time. The authors of this paper have no ambition to resolve this dispute. However, they provide data on the intensity of the electromagnetic fields generated by several components of electronic security system that are operating on the basis of the wireless network. The data have been gained in a specialized workplace and will allow the reader to imagine how intensive the radio signals generated by the battery-operated devices are compared to the current hygienic and technical limits. © The Authors, published by EDP Sciences, 2017.

Voltage-Amplifier stages are the basic components of commonly used high gain amplifiers the bias and other parameters of whose are set by the external negative feedback. The typical device that uses the voltage-Amplifier stage is the operational amplifier. Similar constructions can also be created on the basis of discrete transistors. From the circuit designer's point of view, the voltage-Amplifier stage defines the crucial parameters of the whole unit-the amplification factor, dominant pole of its transfer function and the slew rate. In this paper the proposal on construction of the voltage-Amplifier stage based on discrete transistors is described. When connected between the input differential amplifier and the output stage, it allows creating of cheap amplifier for HiFi applications with considerable performance. © The Authors, published by EDP Sciences, 2017.

As they are spread across almost all applications based on electrical circuits, frequency filters form one of the most complex issues on electronic devices. There exist a great number of different design methods based on various approaches. A large group of these filters is based on active components, namely amplifiers, that are equipped with the appropriate feedback to achieve the desired transfer function. In terms of applications operating at audible frequencies it became to be a rule that one or two operational amplifiers are applied, taking into consideration that their input impedance and amplification factor are infinitely high, whilst their output impedance is infinitely low. The simulation results presented in this paper show that these considerations may not be so strict. That means the input impedance may be in tens of kiloohms and the amplification factor of 40 dB without the feedback loop can do enough. Moreover, the operational amplifiers may be replaced by a simple circuit consisting of two transistors, as it is shown in this paper. This should be considered when calculating manufacturing costs of several designs. In this paper, a detailed description of a band pass filter for a third octave equalizer is presented. However, it is obvious, that the same approach can be applied in other designs. © ECMS Zita Zoltay Paprika, Péter Horák, Kata Váradi,Péter Tamás Zwierczyk, Ágnes Vidovics-Dancs, János Péter Rádics (Editors).

Algorithms - used for the identification and verification of individuals through fingerprint recognition technology have long been extensively used in Forensic Science and in the private sector. This work is concerned with the verification of the reliability of biometric systems that use fingerprints for their activities. Further, the eFinger programme is used to study similarities between men, women's and family members' fingerprints. © ECMS Zita Zoltay Paprika, Péter Horák, Kata Váradi,Péter Tamás Zwierczyk, Ágnes Vidovics-Dancs, János Péter Rádics (Editors).

At the present there is a wide variety of step down converters on market. Due to differences in converter's prices, parameters and principles of function, it is not that easy to choose a proper one suitable for a concrete application. Moreover, really strict standards are applied in order to achieve high EMC compatibility between different devices. This article tries to show the possibilities of a really low-end DC/DC converter controller AOZ 1284. The set of measurements according to the set specifications and standard EN 61000-6-3 are presented together. Moreover, measures needed to comply to limits of the standard are shown along with it's results. © 2016 The Authors, published by EDP Sciences.

Designing of compact step down voltage converter must be provided according to the variety of standards and other requirements. Moreover, the constructed converter usually have to accomplish a set of opposite requirements defined by a target project or a target user (small size vs. high maximum level of provided current, etc.). Therefore the designing of converter could be really tricky. This paper tries to show the possibilities of a really low-end DC/DC converter based on controller AOZ 1284. Moreover, the constructed device is a subject for set of measurement. These measurements are performed in order to confirm that the device meet all requirements defined by standard EN 61000-6-3. All measurement results together with some necessary measures are presented at the end of this paper.

Most remote controllers for entrance gates operate on free frequencies 433 or 868 MHz. However, this technology limits the user comfort, as it is usually not common that bi-directional communication is established. A higher comfort of controlling the entrance gates can be achieved by employing the GSM network for transmission of commands and messages between the gate controller and the user. In this case, only a conventional GSM cellular phone is needed to control the gate. A description of such a controller based on the GSM module and Arduino controller is provided in this paper.

This paper provides a description of an immunity test against the electrostatic discharge according to the standard EN 61000-4-2 that was applied to an RFID reader. The RFID reader was primarily developed for access systems, employing the on-board recognition of the RFID tags. The results obtained by the test are described hereby as well as the discussion on the security of this solution. The results of this experiment are beneficial for the developers of RFID devices, as these devices are endangered by the electrostatic discharge brought by their users. The hereby described results also shown a security hole in a simple access system based on the RFID technology. Details can be found in the paper.

At present, the designers of voltage converters can choose from a wide variety of custom integrated drivers operating at different principles. The authors of this paper aim to show that although the two different designs of a step-down voltage converters can achieve comparable nominal values, at least from the view of the user, due to the differences in the basic principles applied in their drivers they may exhibit different behaviour in the area of the electromagnetic compatibility. This can lead to considerable problems in design of more complex circuits these voltage converters are a part of. For the purposes of the hereby presented results, two different constructions of step-down converters have been chosen. The first one is based on a low-cost and randomly operating solution based on the driver MC 34063 while the second one employs more advanced driver marketed under the label AP 1501. Both converters were constructed and tested for the purposes of application in a power backup device for Power over the Ethernet. The nominal input voltage of both converters is 24 V while their nominal output voltage is 12 V, as used in common applications. Both converters were tested in the EMC laboratory of Tomas Bata University Zlin in order to obtain not only the static parameters, but also the information on how they can interfere with other electronic devices. Within this paper, the most interesting findings are published. © 2016, North Atlantic University Union. All rights Reserved.

The software support for simulation of electrical circuits has been developed for more than sixty years. Currently, the standard tools for simulation of analogous circuits are the simulators based on the open source package Simulation Program with Integrated Circuit Emphasis generally known as SPICE (Biolek 2003). There are many different applications that provide graphical interface and extended functionalities on the basis of SPICE or, at least, using SPICE models of electronic devices. The author of this paper performed a simulation of a circuit that acts as an electronic diode in Multisim and provides a comparison of the simulation results with the results obtained from measurements on the real circuit. © ECMS Thorsten Claus, Frank Herrmann, Michael Manitz, Oliver Rose (Editors).

This article presents the possibilities offered by exploiting CHR 6-DM Orientation Sensors in Security Technologies. It also addresses hardware resources suitable for the inertial navigation of RC models used in Security Technologies. The basis of the CHR 6-DM sensor is a gyroscope that is further complemented by an accelerometer and a magnetometer. In order to use orientation sensor security technology, suitable software was developed that can be used for the autonomous implementation of autonomous RC models suitable for use in Security Technology applications. © ECMS Thorsten Claus, Frank Herrmann, Michael Manitz, Oliver Rose (Editors).

The paper presents the construction of a locator to determine locations using GSM technology. The locator’s design will be tailored especially for the mobile security of more expensive items. The theoretical part will discuss different ways of positioning - using GSM technology in detail. In the conclusion, the benefits of GSM localisation for security applications are evaluated and compared to satellite locations. © 2016, North Atlantic University Union. All rights reserved.

Anechoic and semi anechoic chambers are among the necessary equipment that is needed for testing of devices for their electromagnetic compatibility or for experiments with electromagnetic field emitters, receivers, shielding and many more devices. As they require shielding for their proper operation, undesirable reflections occurring inside them are a natural consequence that must be eliminated by suitable absorbers. Naturally, the reflections cannot be eliminated absolutely in any case, but the aim of the constructers of such chambers is always to minimize them as well as possible. As the constructions of the chambers differ, each of them shows different resonant frequencies and standing waves displacement, although it complies with the standards for electromagnetic compatibility measurement. This phenomenon increases in its importance when the chamber is intended to be used for scientific purposes. In some cases, the knowledge of its behavior is crucial for various experiments. Because the standing waves caused by the reflections inside the chamber manifest themselves as resonant peaks occurring in the frequency response measurement, one of the possibility of evaluation of the quality of the reflections’ damping is to identify the resonant peaks and calculate the Q-factor of the chamber, considering it acts as a cavity resonator. As cavity resonators usually show very high Qfactors, the lower value is obtained, the better damping by the absorbers in the chamber is ensured. One of such approaches to evaluate the real chamber that is being operated at Tomas Bata University in Zlin, using an algorithm implemented in Maple software, is described within the framework of this paper. © 2016, North Atlantic University Union. All rights reserved.

RFID technology has established itself in many sectors of human activity, including security and access systems. Just at this context, the demands on the hardware design in terms of its electromagnetic compatibility become critical. This paper provides a description of an immunity test against the electrostatic discharge according to the standard EN 61000-4-2 that was applied to an RFID reader which was primarily intended to be applied in access systems, employing the on-board recognition of the RFID tags. It was shown that such device can be endangered by the external electrostatic pulse; the findings described in this paper may be beneficial for the developers of the hardware for the RFID devices.

This work deals with the construction of a locator to determine locations using GSM technology. The locatoŕs design will be tailored especially for the mobile security of more expensive items. The theoretical part will discuss different ways of positioning-using GSM technology in detail. In the conclusion, the benefits of GSM localisation for security applications are evaluated and compared to satellite locations.

In this paper a design of a voltage controlled amplifier is described together with its practical realization and measured parameters. The amplifier is supposed to be employed in audio signal processing systems, for example volume expanders, etc. The design was created with the aid of several software supports as Maple for mathematical description of the circuit or Multisim for complex analysis of the amplifier's behaviour. The verification of the design was done by practical construction and performance measurements. The discussion on the differences between the simulated and really obtained results is also included in the framework of this paper.

The spurious aka counterfeit components represent still a serious danger for functionality, reliability and lifetime of any electronic device these components are part of its manufactured assembly. There exist a lot of methods aimed at revealing counterfeit components before they are used in electronic module production. Those methods differ in complexity and also in counterfeit component filtering yield. In short, any efficient method based on specification parameters manifestation, functionality and appearance comparison is applicable. This presentation illustrates the diagnostic abilities of some representative methods for counterfeit components preventive filtering from a production process. As a result of our research activities, the capability of popularly known Analogue Signature Analysis method is mentioned and illustrated as well as laser decapsulation method and a comparison of visual features accentuated with light exposure.

This paper describes an equipment being developed at the Department of Electronics and Measurement of the Faculty of Applied Informatics of Tomas Bata University in Zlin that is designed to process measurements of shielding efficiency of composite materials according to standards MIL-STD 285 and IEEE Std. 299-2006. This kind of measurement is demanded by aircraft industry that develops new, lightweight materials for construction of aircrafts with reduced weight and dimensions and increased number of electronic devices. Besides the fact, that it is necessary to ensure mutual electromagnetic compatibility of the equipment mounted on the aircraft's board, all the devices must also sustain interferences caused by High Intensity Radiated Field (HIRF). This is important all the more, as in the past, there were several aircraft crashes recorded as a result of interference of their equipment with terrestrial transmitters. The hereby described measuring station enables measurement of the shielding efficiency of various materials by means of a comparative method, using a steel plate as a default material.

For the purposes of development of a small and autonomously operated airship, a need to create a model of its propelling and motion has arisen. Being described within this paper, the model defines the requirements that are imposed to motors, propellers and the airship's controlling system. The model is based on a typical design of a small airship, that consists of two main propellers, being placed symetrically according to the gondola beneath the airship's bladder, and one tail propeller that is placed transversely at the airship's tail. According to this model, forces needed to move the airship in the desired direction can be estimated as well as the power consumption of the motors and angular velocity of the propellers. Although the dynamic model of the airship would exceed the framework of this paper, it is also described in broad terms and the results of two main simulations are presented hereby. The simulations describe the behavior of the airship in case of forward acceleration and braking as well as in case of yawing with such braking that ensures reaching of the desired yawing angle. © ECMS Valeri M. Mladenov, Petia Georgieva, Grisha Spasov, Galidiya Petrova (Editors).

The paper presents the design and experimental experience with the gas flow measurement instrument for the range of (5-25) ml/hr. The aimed application area is in a biochemical laboratory for the study of reaction kinetic of sediments decomposition in waste water. The time-of-flight type of sensor with one upstream and one downstream temperature sensor has been chosen for the study. We explain the basic operation principles of the tiny flow measurement and the sensor structure. In the numerical model paragraph, we are describing the basic configuration model and the modelling results. As the three-dimensional simulation would be very time consuming process, we have simplified the simulation for only two-dimensional task. The presented diagrams are derived for different gases (air, nitrogen, carbon oxide and chlorine) and sensor tube materials, namely steel, copper, and plexi-glass. We present also the experimental set-up including the design and sensor parameters. The paragraph with experimental results and discussion on them illustrates the good correspondence with expected values. The paper concludes with the employment of designed gas flowmeter in the biochemical laboratory. © ECMS Valeri M. Mladenov, Petia Georgieva, Grisha Spasov, Galidiya Petrova (Editors).

Currently, the technology of Power over Ethernet becomes rather popular, mainly for powering of terminal devices. Provided these devices are used to drive larger wireless network, it is appropriate that they were provided with a backup source in case of power failure. As the voltages used by Power over Ethernet technology are compatible with voltages of standard lead-acid batteries, the construction of the backup source can be simplified by omitting the output voltage inverter. Although the simplest way of creating a backup source is just to connect the appropriate lead-acid battery in parallel to the output of the main power source, there are more convenient solutions based on switches with MOSFET transistors. More sophisticated control of the battery connecting and charging will significantly prolong its life. One of such solutions is provided within the framework of this paper. The basic concept of the backup power source provides the output voltage of 24 V, but it can be optionally equipped with converters increased this voltage up to 48 V or decreasing it down to 12 V. The description of the converters is provided as well. © 2014 North Atlantic University Union. All rights reserved.

This paper deals with a design and construction of a dual-channel oscilloscope interface which enables concurrent measurement of voltage and current waveforms up to 30 kHz. The operation of the unit is based on a capacitive coupling through and isolation barrier inside a custom integrated circuit. The construction is cheap and easy to be bulit. Two samples of the device were bulit and tested at certain service operations. Based on the experience, several modifications have been proposed. These proposals are included in this paper as well. © 2014 North Atlantic University Union. All rights reserved.

Paper describes suggestions on the improvement of the common On-line structure of the uninterruptable power supply units used for powering of network devices. According to these suggestions a prototype circuit able to deliver the output power up to 150 W was constructed. The topology was optimized in order maximum efficiency was achieved when the output is fed by an accumulator in order the operating time was as long as possible.