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Measurement system with preamplifier for calibration of vibration sensors
Kaštovský, Jan ; Doseděl, Martin (referee) ; Havránek, Zdeněk (advisor)
This thesis deals with the design and implementation of a preamplifier for vibration sensors with IEPE interface and also for vibration sensors with charge output. The thesis also deals with a modification of a computer application for a measuring system in LabVIEW. The thesis builds on the already implemented measuring system for secondary calibration of vibration sensors. The results of the secondary calibration of this system with the added preamplifier are compared with the results of a primary calibration.
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Bandlimited signals, their properties and extrapolation capabilities
Mihálik, Ondrej ; Havránek, Zdeněk (referee) ; Jura, Pavel (advisor)
The work is concerned with the band-limited signal extrapolation using truncated series of prolate spheroidal wave function. Our aim is to investigate the extent to which it is possible to extrapolate signal from its samples taken in a finite interval. It is often believed that this extrapolation method depends on computing definite integrals. We show an alternative approach by using the least squares method and we compare it with the methods of numerical integration. We also consider their performance in the presence of noise and the possibility of using these algorithms for real-time data processing. Finally all proposed algorithms are tested using real data from a microphone array, so that their performance can be compared.
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Angular velocity sensor with Sagnac interferometer
Skalský, Michal ; Beneš, Petr (referee) ; Havránek, Zdeněk (advisor)
This thesis deals with theoretical description of fiber-optic angular velocity sensors, or gyroscopes, and further with design and construction of own sensor of this type. The theoretical part describes problematics of interferometric and resonant fiber-optic gyroscopes. Basic principles and physical limits are described for both types. The main focus is then put on analysis of possible conceptions of these sensors. Solutions using different optical configurations as well as various modulation and signal processing schemes are discussed. The practical part deals with design and construction of own interferometric fiber-optic gyroscope in closed-loop configuration. The gyroscope utilizes all-fiber components including piezoelectric phase modulator and unexpensive single-mode fiber, which are commonly used only for open-loop configurations. To realize closed-loop operation, special modulation scheme based on fully harmonic signal was develeped, which yields linear output within wide dynamic range. This type of modulation requires high level of synchronization achieved by using a field-programmable gate array module. The gyroscope utilizes powerful broadband fiber source, polarizer and Lyot depolarizer which ensure good reciprocity of whole architecture. The parameters of the sensor, obtained by measurement, are even comparable to some sensors using PM fiber, which is much more expensive.
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Analysis of liquid electrolyte electrical parameters using impedance spectroscopy
Brabenec, Josef ; Pikula, Stanislav (referee) ; Havránek, Zdeněk (advisor)
The bachelor thesis deals with impedance spectroscopy of electrochemical systems, especially liquid electrolytes. The method of impedance spectroscopy is widely used to describe electrochemical cells, batteries and electrolytes for diagnostic purposes over a wide range of frequencies. This thesis presents the main types of impedance imaging in the complex and frequency domain, as well as basic information on the measurement methods used and the methods for impedance analysis. The main part of the thesis was the development of software for automated impedance measurements and estimation of equivalent circuit parameters using basic and specialized circuit elements. A workplace with fabricated electrodes for liquid electrolyte measurements was prepared for the application. The functionality of the application was verified by real measurements of different concentrations of water and salt solutions. The validity of the estimated equivalent circuit parameters was verified on measured simple circuits connected from basic circuit elements and was also verified using the commercially used ZView software.
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Utilization of artificially created weak magnetic field for navigation in 3D space
Váňa, Dominik ; Beneš, Petr (referee) ; Havránek, Zdeněk (advisor)
This master's thesis focuses on the utilization of an artificially created weak magnetic field for navigation in 3D space. The theoretical part of this work deals with the general properties of the magnetic field and with its description. The next section of the theoretical part contains an overview of measuring principles for magnetic field measurements. Based on various types of measuring principles, the thesis elaborates on commercially available miniature sensors for magnetic field measurement with a measuring range up to 10 mT. The work focuses mainly on the magnetoresistive principle and fluxgate sensors. Furthermore, the theoretical part contains descriptions of methods for modeling the magnetic field of simple permanent magnets and various magnet assemblies. Lastly, the theoretical part involves a patent search of devices used for locating magnets that are installed in an intramedullary nail, which is used in intramedullary stabilization used on fractures of human bones. By locating the magnet in the nail, it is possible to precisely determine the position of the mounting holes. The practical part of the thesis deals with the analysis of magnetic field behavior in the vicinity of various magnetic assemblies, which were modeled in COMSOL Multiphysics using the finite element method. The models were created with the aim of analysing the behaviour of the magnetic field in the vicinity of the magnets and at the same time to find possible analytical functions that could be used to determine the position of the magnet in space relative to the probe. The result of this work is an analysis of various assemblies, which contains graphs of different dependencies and prescription of polynomial functions that approximate these dependencies. Another part of the thesis is the design of a probe that serves to locate the magnetic target. The work describes two possible methods of localization. For the differential method, a user interface in LabVIEW was created. The probe based on this method is fully capable of locating the magnet in the 2D plane. The state space search method is described only in theory.
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Automation Measurement System
Žampach, Aleš ; Havránek, Zdeněk (referee) ; Štohl, Radek (advisor)
Bachelor’s thesis is bent on creation control software for multimeter and function generator. The first part of the thesis is focused on theoretical problems of individual parts of the whole measuring system and his parts. It show communication control unit with measuring instruments over the GPIB interface. Second part serves to presentation to problems graphical programming method and either as manual to control software for automated measuring system. At last third part are introduced examples of validation measure for check functionality software.
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Near-field acoustical holography methods in LabVIEW environment
Majvald, František ; Hnidka,, Jakub (referee) ; Havránek, Zdeněk (advisor)
Near-field acoustical holography is a standard method for sound source visualization and localization. In this thesis, commonly used and newly published near-field acoustic holography methods are introduced and analysed. In addition, regularization methods are presented together with finding options of optimal regularization parameter. Based on theory, a LabVIEW library is built containing four implemented near-field acoustical holography algorithms and two regularization methods. To verify the correctness of implementations, a testing application has been made. This application allows testing of implemented algorithms with simulated or experimentally measured data. The correctness of implementation is verified, and algorithms are compared to each other with respect to accuracy and speed of calculation.
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Acoustic fields visualization using laser interference
Raffay, Tobiáš ; Havránek, Zdeněk (referee) ; Skalský, Michal (advisor)
This bachelor thesis is focused on solving the visualization of acoustic waves using laser interference. The necessary theoretical knowledge to understand the used method of schlieren photography are summarized in the theoretical part. The practical part describes the implementation and results of the assembled systems, shows the differences, and solves the problems that occurred during testing. Apart from visualization of acoustic waves, we can also observe the flow of gases and air with small changes of refractive index.
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Angular velocity measurement with fiber optic interferometer
Skalský, Michal ; Šedivá, Soňa (referee) ; Havránek, Zdeněk (advisor)
This thesis deals with general theoretical description, design and construction of sensor of angular velocity based on Sagnac interferometer, or interferometric fiber-optic gyroscope. The theoretical part is focused firstly on explanation of basic principles and finding important formulas. Secondly, some state-of-the-art configurations of the fiber-optic gyroscope and their differences are analysed. Limiting factors and parasitic effects are also described. Attention is also paid to properties and suitability of particular optical components. The practical part especially deals with an utilization of common low-birefringent optical fiber in an fiber-optic gyroscope. Firstly, some basic properties of components and the simplest configurations of gyroscope were tested. They provided an important knowledge for design of final solution working in an open loop configuration with phase modulation. Further, specific components used in this demonstration sensor and its construction are described in more detail. Designed gyroscope utilizes all-fiber components made of common low-birefringent fiber so this solution is unexpensive. It uses an unpolarized light and depolarizer to ensure stability. Another specificity is a light source using spontaneous emission of erbium-doped fiber. Finally, some basic parameters of designed gyroscope acquired by measurement as well as record of calibration are stated.
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Measurement of weak magnetic field in 3D space
Bár, Martin ; Klusáček, Stanislav (referee) ; Havránek, Zdeněk (advisor)
The aim of this thesis is to theoretically examine the magnetic field of miniature cylindrical NdFeB magnets, compare the simulation results to real-world measurements, and design a magnetic field probe using suitable sensors. A FEM simulation was conducted using Ansys AIM and FEMM 4.2. The simulation shows that the magnetic induction on the surface of the magnet depends on the diameter/height ratio. The simulation results also show that 21 µm thick protective layer of Ni-Cu-Ni metal on the surface of NdFeB magnets lowers flux density of the smallest magnet sample (1x1 mm) by up to 14 %. It was also concluded that a larger magnet edge radius results in a higher flux density on the surface of the magnet. The biggest differences between simulation data and data measured by the F.W. BELL gaussmeter occurred in the smallest magnet sample. Using the FEMM 4.2 simulation software, a three-axis magnetic field probe was designed. Potential problems with this probe design have been identified. A simple procedure for probe calibration was proposed.
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