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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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Data acquisition and processing in LabVIEW
Kroliczek, Filip ; Havránek, Zdeněk (referee) ; Šedivá, Soňa (advisor)
The thesis deals with data collecting and treating issues utilizing the help of the LabVIEW software. An overview is presented on the first pages. Following chapters are dedicated to theoretical analysis of convolution, correlation, fast Fourier transformation and harmonic distortion of signal. Theoretical analysis of the function with of signal treatment precedes an introduction to LabVIEW – a programme for measurement and treatment of signal. The subsequent chapter describes a LabVIEW created measuring function, program settings and description of a chosen part of the programme. The end comprises the evaluation of the elaborated conclusions by means of the measuring card.
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Measurement and analysis of audio-frequency differential disturbances in distribution systems
Doseděl, Tomáš ; Havránek, Zdeněk (referee) ; Drápela, Jiří (advisor)
This thesis deals with voltage disturbances in audio-frequency propagated in distribution networks. In the theoretical part, a creation and effect of these interferences are discussed as well as current methods of their measurement. In the practical part of the thesis, a measurement device based on a frequency filter was developed. This measurement device is able to measure audio-frequency disturbances up to 250kHz without suppresion of audio-frequency disturbances. The maximum frequency on the output is limited by either 125kHz or 250 kHz filter.
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Fiber-optic sensor based on multi-mode interference
Hedl, Michal ; Havránek, Zdeněk (referee) ; Šedivá, Soňa (advisor)
This diploma thesis is focused on measurement of the physical quantities by fiber optic sensors based on multimode interference. The objective is to evaluate the appropriate method of signal provided by the spectrum analyzer. Firstly, a review of optics, optical phenomena and fibers is performed. The basic theory necessary for the realization of measurements and the principal of fiber optic sensors and SMS (singlemode–multimode–singlemode) structures are discussed. Finally, the automated measuring workplace for absorption spectrum measurement is created and described. Given data are finally evaluated by an artificial neural network and a sensor concept for practical utilization is designed.
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Inductive Sensors
Šimberský, Michal ; Havránek, Zdeněk (referee) ; Bejček, Ludvík (advisor)
Bachelor thesis deals with inductive sensors. The thesis introduced the history of sensors, their advantages and disadvantages over other types of sensors. There are described different types of inductive sensors. Each type of sensor is described in terms of physical principles. In thesis there are listed examples of using different types of practice. Preparation was constructed to demonstration the characteristics and differences between eddy currents sensors and inductive oscillator sensors.
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