Дисертації з теми "Measuring transducers"

This thesis is concerned with the design and development of measuring devices for the characterisation of acoustic transients with high temporal and spatial resolution. Three new techniques are demonstrated characterising acoustic transients generated by Nd-YAG laser (1060nm, 30ns, 55mJ) assisted breakdown of water and air. The first technique demonstrates the use of a high power semiconductor laser in a high speed multiple exposure imaging system. This system developed is capable of illuminating an event with up to 10 pulses of light at a maximum repetition rate of 5MHz, with a timing accuracy of ≈5ns. Each semiconductor laser light pulse has a FWHM duration of 50ns, peak power of 30W, and a wavelength of 860nm. Images of individual acoustic transients are displayed on the same CCD camera frame, and it was found that this is best achieved using a dark field imaging technique such as Schlieren imaging.

The methods for the experimental determination of the time constant of measuring transducers are described. The method is based on determining the parameters of the steady-state response of the measuring transducer using a periodic sequence of rectangular pulses of known time pulse and repetition period as an input signal. Expressions for determining the time constant for various response parameters: maximum, minimum, average, and average rectified values are given. The evaluation of the measurement uncertainty for each of the obtained expressions is made. The proposed method has high accuracy and low labour intensity in comparison with the known graph-analytical methods.

Currently, there are a number of ways ISE calibrations, each of which depends on several factors: the amount and nature of the sample, frequency analysis, metrological characteristics and electrode-active properties of the material of the electrodes themselves. However, these calibration methods have limitations when used in the flow-injection analysis method (FIA).

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Level measurement plays a crucial role in a wide range of scientific and industrial applications, such as agriculture, hydrology, soil science, oil, pharmaceutical and food industries, among others. Due to the need of measuring level in different environments and for different liquids, granulated solids or powder, several sensors have been proposed to this end, for example, capacitive, infrared, hydrostatic, ultrasonic, radar, laser, optical, displacer, among others, each having its pros and cons. In particular, displacer-type level sensors are highly linear, precise and exact for a given working condition, in addition to having low cost and being easily installed. However, these sensors estimate liquid level indirectly by measuring the buoyancy forces on a displacer connected to a strain gauge, which makes it highly sensitive to variations in liquid density. As a consequence, it is also sensitive to variations in the liquid temperature, since the density is sensitive to temperature. This makes displacer level sensors unfeasible in industrial applications that do not keep such quantities in a range tight enough to ensure low measurement errors (e.g., oil, food and pharmaceutical industries). As a way to allow for the use of displacer-type level sensors in industrial applications, it is proposed in this work and it was also built a new displacer-type liquid level sensor self-compensating for liquid density. The proposed method uses the ratio between the buoyancy forces measured by two displacers and two load cells to make it density independent and, as a consequence, temperature invariant. Such characteristic is observed in the simulations results. The prototype experimental results show that the system has high linearity, it is able to mitigate the sensitivity to the density of the measurand, and it has potential to make precise measurements.
A medição de nível desempenha um papel crucial em várias aplicações industriais e científicas, tais como produção e refino do petróleo, agricultura, hidrologia, ciências do solo, indústrias alimentícias, indústrias farmacêuticas, dentre outras. Devido à necessidade de mensurar nível em ambientes distintos e para diferentes líquidos, sólidos granulados ou pó, vários sensores de nível têm sido desenvolvidos, por exemplo, o sensor capacitivo, infravermelho, hidrostático, ultrassônico, radar, laser, óptico, deslocador, dentre outros. Cada um com suas vantagens e desvantagens. Em particular, o sensor de nível tipo deslocador tem alta linearidade, precisão e exatidão, além de ser uma tecnologia de baixo custo e instalação simples. Entretanto, esse tipo de sensor estima o nível indiretamente medindo a força empuxo em um deslocador conectado a uma célula de carga, o que o torna muito sensível a variações na densidade do líquido. Como consequência, o mesmo também é sensível a variações na temperatura do líquido, pois a densidade é sensível à temperatura. Isso inviabiliza a aplicação dessa tecnologia em atividades que a densidade ou a temperatura do líquido não é mantida em uma faixa pequena de variação, como nas indústrias farmacêuticas, alimentícias e petrolíferas. Para viabilizar a aplicação do sensor de nível tipo deslocador em tais atividades, neste trabalho é proposto e construído um sensor de nível tipo deslocador com autocompensação da densidade do líquido. O método proposto usa a relação entre as forças de empuxo medidas por dois deslocadores e duas células de carga para tornar o sensor idealmente insensível às variações na densidade do líquido e, como consequência, insensível a variações na temperatura do líquido. Tal característica é observada nos resultados por simulação. Os resultados dos experimentos realizados com o protótipo mostram que o sistema tem alta linearidade, é capaz de mitigar a sensibilidade à densidade do líquido e tem potencial para fazer medições precisas.
São Cristóvão, SE

Optical current sensors (OCSs) are initially developed to measure relatively large current over a wide range of frequency band. They are also used as protective devices in the event a fault occurs due to a short circuit, in the power generation and distribution industries. The basic principal used in OCS is the Faraday effect. When a light guiding faraday medium is placed in a magnetic field which is produced by the current flowing in the conductor around the magnetic core, the plane of polarization of the linearly polarized light is rotated. The angle of rotation is proportional to the magnetic field strength, proportionality constant and the interaction length. The proportionality constant is the Verdet constant V (λ, T), which is dependent on both temperature and wavelength of the light. Opto electrical methods are used to measure the angle of rotation of the polarization plane. By measuring the angle the current flowing in the current carrying conductor can be calculated. But the accuracy of the OCS is lost of the angle of rotation of the polarization plane is dependent on the Verdet constant, apart from the magnetic field strength. As temperature increases the Verdet constant decreases, so the angle of rotation decreases. To compensate the effect of temperature on the OCS, a new method has been proposed. The current and temperature are measured with the help of a duel frequency method. To detect the line current in the conductor or coil, a small signal from the line current is fed to the reference of the lock in. To detect the temperature, the coil is excited with an electrical signal of a frequency different from the line frequency, and a small sample of this frequency signal is applied to the reference of the lock in. The temperature and current readings obtained are look up at the database value to give the actual output. Controlled environment is maintained to record the values in the database that maps the current and temperature magnitude values at the DSP lock in amplifier, to the actual temperature and current. By this method we can achieve better compensation to the temperature changes, with a large dynamic range and better sensitivity and accuracy.

The vestibular system is one of our main organs responsible for the sense of balance. This system is located within the inner ear and contains cells with ciliary bundles. These hair cells are transducers that convert a mechanical movement, detected by the bundle of cilia extending from their top surface, into an electrochemical signal to be sent to the brain. The bundles vary structurally within the organs of the inner ear, and this structural difference may play a role in the mechanical properties of each bundle. Analyzing the mechanical properties of the cells will provide information necessary for understanding the transduction process. In an effort to evaluate one of these properties, cell bundle stiffness, a system was designed to mechanically stimulate the bundles within their physiological range and then measure the resulting displacement. The mechanical stimulation was the result of a force applied to the tip of a bundle with the end of a glass whisker. The distance the base of the whisker moves is measured by an extrinsic Fabry-Perot interferometer (EFPI). The magnitude of this movement is compared with the amount the bundle is deflected, detected by a photoelectronic motion transducer (PMT). Knowing these displacements and the stiffness of the glass whisker, simple kinematics is used to determine the bundle stiffness. System tests were conducted on imitation bundles (whiskers of known stiffness) and the experimental stiffness differed from the known value by less than 4.5% for every test. These results lead us to conclude the system was in good working order and could be used to conduct tests on cell bundles. For tissue tests, this work focused on the hair cells located within the utricle, which senses linear accelerations of the head. Within the utricle, we examined two types of hair cells: non-striolar (medial type II) and striolar. Tests on twelve medial type II cells found bundles ranging in stiffness from 0.26 to 2.62 x 10-5 N/m. Results with striolar bundles provided a range from 2.83 to 27.10 x 10-5 N/m. The results of the preliminary tissue tests lead us to conclude that the average stiffness of the striolar and non-striolar bundles seems to vary by an order of magnitude. This is consistent with the relative relationship produced through a computer model. However, the model predicted larger stiffness values for both types of cells.
Master of Science

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O monitoramento de integridade estrutural (SHM) baseado na técnica da impedância eletromecânica (EMI) tem sido desenvolvido como uma ferramenta promissora para identificação de falhas estruturais. As aplicações típicas de SHM baseadas em EMI geralmente utilizam um analisador de impedância comercial de alto custo ou sistemas de medição baseados na função de resposta em frequência (FRF). Além do custo elevado, as exigências de capacidade de armazenamento e/ou processamento de dados desses instrumentos são características proibitivas para muitas aplicações. Trabalhos recentes mostram que não é preciso conhecer o valor exato da impedância eletromecânica da estrutura para monitorar sua integridade. Assim, neste trabalho é apresentado um sistema de SHM que permite detectar falhas em estruturas monitorando apenas as variações da tensão elétrica do transdutor. O sistema proposto é portátil, autônomo, rápido, versátil, de baixo custo e substitui com eficiência os instrumentos comerciais na fase de detecção de falhas. A identificação do dano é feita comparando-se as variações da tensão rms da resposta no tempo que um transdutor piezelétrico de PZT, colado na estrutura, fornece para cada frequência do sinal de excitação. Portanto, o sistema proposto não é limitado pela frequência de amostragem, dispensa algoritmos da transformada de Fourier e não exige um computador para processamento, operando de forma autônoma. Um protótipo de baixo custo usando circuitos integrados, um sintetizador digital e um microcontrolador foi construído e testado através de experimentos em estruturas de alumínio para a faixa de frequências a partir de 3 kHz até 50 kHz com boa precisão e estabilidade
Structural health monitoring (SHM) based on electromechanical impedance (EMI) technique has been developed as a promising tool for identifying structural damage. Typical applications in SHM based on EMI generally use high-cost commercial impedance analyzers or measurement systems based on frequency response function (FRF). Besides the high cost, the requirements for storage and/or data processing of these instruments are prohibitive features for many applications. Recent studies show that the exact value of the electromechanical impedance is not required for damage detection. Thus, this work presents a SHM system that can detect damage in structures only monitoring the changes in the voltage of the transducer. The proposed system is portable, autonomous, fast, versatile, low-cost and replaces efficiently commercial instruments in the damage detection stage. The identification of damage is done by comparing the variations in the rms voltage of time response signals from a piezoelectric transducer, such as PZT, bonded to the structure. Different time response signals are obtained for each frequency of the excitation signal. Therefore, the proposed system is not limited by the sampling frequency, dispenses Fourier transform algorithms and does not require a computer for processing, operating autonomously. A low-cost prototype using integrated circuits, a microcontroller and a digital synthesizer was built and tested through experiments with aluminum structures for frequencies ranging from 3 kHz to 50 kHz with good accuracy and stability

Orientador: Jozué Vieira Filho
Coorientador: Fabricio Guimarães Baptista
Banca: Suely Cunha Amaro Mantovani
Banca: Fabiano Fruett
Resumo: O monitoramento de integridade estrutural (SHM) baseado na técnica da impedância eletromecânica (EMI) tem sido desenvolvido como uma ferramenta promissora para identificação de falhas estruturais. As aplicações típicas de SHM baseadas em EMI geralmente utilizam um analisador de impedância comercial de alto custo ou sistemas de medição baseados na função de resposta em frequência (FRF). Além do custo elevado, as exigências de capacidade de armazenamento e/ou processamento de dados desses instrumentos são características proibitivas para muitas aplicações. Trabalhos recentes mostram que não é preciso conhecer o valor exato da impedância eletromecânica da estrutura para monitorar sua integridade. Assim, neste trabalho é apresentado um sistema de SHM que permite detectar falhas em estruturas monitorando apenas as variações da tensão elétrica do transdutor. O sistema proposto é portátil, autônomo, rápido, versátil, de baixo custo e substitui com eficiência os instrumentos comerciais na fase de detecção de falhas. A identificação do dano é feita comparando-se as variações da tensão rms da resposta no tempo que um transdutor piezelétrico de PZT, colado na estrutura, fornece para cada frequência do sinal de excitação. Portanto, o sistema proposto não é limitado pela frequência de amostragem, dispensa algoritmos da transformada de Fourier e não exige um computador para processamento, operando de forma autônoma. Um protótipo de baixo custo usando circuitos integrados, um sintetizador digital e um microcontrolador foi construído e testado através de experimentos em estruturas de alumínio para a faixa de frequências a partir de 3 kHz até 50 kHz com boa precisão e estabilidade
Abstract: Structural health monitoring (SHM) based on electromechanical impedance (EMI) technique has been developed as a promising tool for identifying structural damage. Typical applications in SHM based on EMI generally use high-cost commercial impedance analyzers or measurement systems based on frequency response function (FRF). Besides the high cost, the requirements for storage and/or data processing of these instruments are prohibitive features for many applications. Recent studies show that the exact value of the electromechanical impedance is not required for damage detection. Thus, this work presents a SHM system that can detect damage in structures only monitoring the changes in the voltage of the transducer. The proposed system is portable, autonomous, fast, versatile, low-cost and replaces efficiently commercial instruments in the damage detection stage. The identification of damage is done by comparing the variations in the rms voltage of time response signals from a piezoelectric transducer, such as PZT, bonded to the structure. Different time response signals are obtained for each frequency of the excitation signal. Therefore, the proposed system is not limited by the sampling frequency, dispenses Fourier transform algorithms and does not require a computer for processing, operating autonomously. A low-cost prototype using integrated circuits, a microcontroller and a digital synthesizer was built and tested through experiments with aluminum structures for frequencies ranging from 3 kHz to 50 kHz with good accuracy and stability
Mestre

We present hereafter the development of the Liebherr Intelligent Hydraulic Cylinder, in which the hydraulic component is used as smart sensing element providing useful information for the system in which the cylinder is operated. The piston position and velocity are the most important signals derived from this new measuring approach. The performance under various load and temperature conditions (measured both on dedicated test facilities and in field in a real machine) will be presented. An integrated control electronics, which is performing the cylinder state processing, additionally allows the synchronized acquisition of external sensors. Providing comprehensive state information, such as temperature and system pressure, advanced control techniques or monitoring functions can be realized with a monolithic device. Further developments, trends and benefits for the system architecture will be briefly analyzed and discussed.

Certaines pathologies fonctionnelles requièrent une rééducation articulaire spécifique. Pour ce faire, il est nécessaire de quantifier la cinématique angulaire des mouvements imposes au patient; celle-ci a deux buts principaux: permettre une rééducation la plus adaptée possible et un suivi clinique. La recherche dans ce domaine est motivée par l'absence sur le marché de dispositifs conviviaux, polyvalents et peu couteux. Une étude est donc menée sur la réalisation d'un capteur polyvalent de mesure angulaire à fibres optiques: l'originalité de cette étude fait appel à différents concepts de techniques évoluées. Après une importante recherche bibliographique, une approche géométrique est adoptée pour analyser l'atténuation lumineuse provoquée par la courbure dans une fibre. Un banc de tests automatisé est conçu pour étudier le comportement de l'onde lumineuse en fonction du rayon et de l'angle dans une fibre optique courbée. A la suite d'un traitement électronique du signal détecté, une mesure indirecte de l'angle de courbure est déduite. Enfin, l'évaluation des performances du capteur est discutée à partir des résultats obtenus

Die vorliegende Arbeit untersucht, wie die genaue Kenntnis der Sende- und Empfangsschallfelder eines Ultraschallwandlers zur Entwicklung neuer Meßverfahren genutzt werden kann. Insbesondere werden dargestellt: - ein neuartiges, nichtscannendes Verfahren zur Bestimmung der Krümmung eines Reflektors, basierend auf der Analyse der Wellenfrontkrümmung reflektierter Schallfelder - ein neuartiges, nichtinvasives Verfahren zur Bestimmung der Schallgeschwindigkeit in einer Flüssigkeit durch Auswertung der Echosignale von im Ausbreitungsmedium vorhandenen Streupartikeln und - ein Verfahren zur Wandlercharakterisierung durch Messungen in Fluiden mit Streupartikeln, sowie verschiedene Zuordnungen von Schallfeldmerkmalen zu spezifischen Eigenschaften eines Ultraschallwandlers. Im Zusammenspiel von Simulation und Experiment konnten die Funktionstüchtigkeit aller Meßverfahren nachgewiesen und vielversprechende innovative Ansätze für zukünftige Entwicklungen angeregt werden: 1. Das nichtscannende Verfahren zur Krümmungsmessung erlaubt bei guter Justage eine Krümmungsbestimmung von Reflektoren mit Radien zwischen 6 und 11 mm mit einer Unsicherheit von ungefähr 0,5 mm. In Kombination mit herkömmlichen scannenden Verfahren bietet es Ansätze zur präzisen Größenbestimmung von Fehlern in der zerstörungsfreien Prüfung. 2. Das Verfahren zur nichtinvasiven Schallgeschwindigkeitsmessung erlaubt eine Bestimmung von Schallgeschwindigkeiten mit einer statistischen Meßunsicherheit von 0,1 %. Mögliche Weiterentwicklungen zur Messung der Schallgeschwindigkeit mit örtlicher Auflösung und zur Gewinnung neuer Diagnosemöglichkeiten in Metallurgie (nichtinvasive Charakterisierung von Mischungsvorgängen) und Biomedizintechnik (nichtinvasive Temperaturmessung in Körpergewebe zur Überwachung der Hyperthermiebehandlung, Gewebecharakterisierung) werden erläutert. Aus verschiedenen bekannten sowie einem neuartigen, leicht anwendbaren Meßverfahren werden neue Schlüsse gezogen a) zur Bestimmung der akustisch effektiven Elementgröße von Wandlerelementen mittels Schallfeldmessungen, b) zur Qualitätssicherung im Hinblick auf Schallkopfasymmetrien und c) zur Verbesserung von Schallfeldsimulationen
The current thesis explores how the precise knowledge of the sending and receiving sound fields of an ultrasonic transducer can contribute to the development of novel measuring techniques. Emphasis is placed on: - a novel, non-scanning method for the determination of the curvature radius of a spherical reflector, based on the analysis of the wave front curvature of the reflected sound field, - a novel non-invasive method for sound velocity measurements in fluids using the echo signals from scattering particles, and - novel conclusions on how to use well-known sound field measurement methods for transducer characterisation, as well as an introduction to a novel easy-to-use method for transducer characterisation exploiting the echo signals from scattering particles. Proof of concept is shown for all methods by simulation and measurement, and different promising improvements for further techniques are suggested: - The non-scanning method for curvature measurements makes it possible to determine reflector radii between 6 and 11 mm with an uncertainty of about 0.5 mm, provided that there is a good reflector alignment. In combination with conventional methods, a novel approach for the determination of the size of discontinuities in non-destructive testing is outlined. - The method for non-invasive sound velocity measurements allows the determination of sound velocity in homogeneous fluids with a statistical uncertainty of 0.1 %. Future improvements are suggested to allow sound velocity measurements with local resolution, which enables novel approaches for metallurgy (non-invasive characterisation of mixing processes) and biomedical engineering (non-invasive temperature control for hyperthermia treatment, tissue characterisation). - New conclusions are drawn based on well-established and a novel easy-to-implement measurement method regarding a) the determination of the acoustically effective element size of transducer elements, b) transducer asymmetries, thereby improving quality control, and c) the improvement of sound field simulations

Дисертація на здобуття наукового ступеня кандидата технічних наук (доктора філософії) за спеціальністю 05.11.13 "Прилади і методи контролю та визначення складу речовин" (15 – Автоматизація та приладобудування) – Національний технічний університет "Харківський політехнічний інститут". Мета роботи: удосконалення резонансного діелькометричного методу контролю та визначення вологості рідких неполярних діелектриків задля підвищення його чутливості до рівня 10⁻⁵ з одночасною мінімізацією впливу "сортової невизначеності". Запропоновані та досліджені: спрощена математична модель емульсії на основі моделі штучного діелектрика Кока; нові багаточастотні різновиди резонансного діелькометричного методу; новий тип розподіленого вимірювального перетворювача. Розроблено, теоретично та експериментально досліджено вологоміри середньочастотного та дуже високочастотного діапазонів. Експериментальним шляхом підтверджено досягнення мети роботи.
Thesis for a candidate degree (PhD) in specialty 05.11.13 "Instruments and methods of control and determination of substances" (15 – Automation and Instrumentation) − National Technical University "Kharkiv Polytechnic Institute". The thesis is devoted to the improvement of the resonant dielectric method of monitoring and determining the humidity of emulsions such as liquid non-polar dielectric - water in order to increase its sensitivity to level 10⁻⁵ while simultaneously minimizing the type and grade of non-polar dielectric ("varietal uncertainty") on the measurement results. An analytical review and analysis of the existing methods and means of implementation of the dielectric method in general and its resonant variety has been carried out. The main research areas have been identified: development of a simplified emulsion model; development of new varieties of the resonant dielectric method with minimization of the effect of "varietal uncertainty" for measuring humidity at a level of 10⁻⁵; development of a new type of distributed transducer. A simplified emulsion model was chosen based on the Kok artificial dielectric model, its applications were determined by frequency, humidity, and the values of its systematic errors were determined. New multifrequency varieties of the resonant dielectric method have been developed based on the proposed mathematical model of the emulsion, taking into account the parasitic capacitances of the measuring generator and the measuring converter. Metrological characteristics of the generalized four-frequency method and its simplified three-and two-frequency varieties are obtained. The areas of applicability of multifrequency methods are analyzed and their systematic errors are determined. The most sensitive method, the two-frequency method, was determined, the effect of dielectric losses in water was analyzed for it, and the generation frequency of the measuring generator, which corresponds to its maximum sensitivity, 100 MHz, was determined. A new type of distributed-type measuring transducer is proposed for the practical implementation of the two-frequency method — a stepwise heterogeneous coaxial resonator; its theoretical and experimental studies are carried out; its advantages in relation to the known transducers are determined. A hygrometer of the mid-frequency range based on a concentrated-type capacitive transducer and a hydrometer of a very high-frequency range based on a stepped heterogeneous coaxial resonator have been developed. The circuit solutions of the measuring transducer and the measuring generator of the hygrometer of the midfrequency range, which provided the minimum values of their parasitic capacitances, were developed and implemented. The circuit solutions of the measuring transducer and the measuring generator of a hygrometer of a very high frequency range have been developed and implemented, which provided almost zero effect of their parasitic capacitances. A methodology has been developed for conducting experimental research on the implementation of four- and three-frequency methods using a mid-range moisture meter and implementing a two-frequency method and a simplified version of it using a very high-frequency moisture meter. Experimental studies on manufactured test emulsions, as well as analysis and processing of their results, were carried out. For all developed multi-frequency methods and moisture values of test emulsions in the range of 10⁻⁴ – 10⁻², the value of the relative extended uncertainty of moisture measurement did not exceed 5.28 %. For the humidity of the test emulsion 10⁻⁵, the value of this uncertainty did not exceed 10.39 % (due to the lack of stability of the frequency of the reference generator frequency Ch 3 - 34, which was used in the research). The developed improved multi-frequency resonance dielectric methods for determining humidity have increased the sensitivity to a level of 10⁻⁵ while minimizing "varietal uncertainty".

Дисертація на здобуття наукового ступеня кандидата технічних наук (доктора філософії) за спеціальністю 05.11.13 "Прилади і методи контролю та визначення складу речовин" (15 – Автоматизація та приладобудування) – Національний технічний університет "Харківський політехнічний інститут". Мета роботи: удосконалення резонансного діелькометричного методу контролю та визначення вологості рідких неполярних діелектриків задля підвищення його чутливості до рівня 10⁻⁵ з одночасною мінімізацією впливу "сортової невизначеності". Запропоновані та досліджені: спрощена математична модель емульсії на основі моделі штучного діелектрика Кока; нові багаточастотні різновиди резонансного діелькометричного методу; новий тип розподіленого вимірювального перетворювача. Розроблено, теоретично та експериментально досліджено вологоміри середньочастотного та дуже високочастотного діапазонів. Експериментальним шляхом підтверджено досягнення мети роботи.
Thesis for a candidate degree (PhD) in specialty 05.11.13 "Instruments and methods of control and determination of substances" (15 – Automation and Instrumentation) − National Technical University "Kharkiv Polytechnic Institute". The thesis is devoted to the improvement of the resonant dielectric method of monitoring and determining the humidity of emulsions such as liquid non-polar dielectric - water in order to increase its sensitivity to level 10⁻⁵ while simultaneously minimizing the type and grade of non-polar dielectric ("varietal uncertainty") on the measurement results. An analytical review and analysis of the existing methods and means of implementation of the dielectric method in general and its resonant variety has been carried out. The main research areas have been identified: development of a simplified emulsion model; development of new varieties of the resonant dielectric method with minimization of the effect of "varietal uncertainty" for measuring humidity at a level of 10⁻⁵; development of a new type of distributed transducer. A simplified emulsion model was chosen based on the Kok artificial dielectric model, its applications were determined by frequency, humidity, and the values of its systematic errors were determined. New multifrequency varieties of the resonant dielectric method have been developed based on the proposed mathematical model of the emulsion, taking into account the parasitic capacitances of the measuring generator and the measuring converter. Metrological characteristics of the generalized four-frequency method and its simplified three-and two-frequency varieties are obtained. The areas of applicability of multifrequency methods are analyzed and their systematic errors are determined. The most sensitive method, the two-frequency method, was determined, the effect of dielectric losses in water was analyzed for it, and the generation frequency of the measuring generator, which corresponds to its maximum sensitivity, 100 MHz, was determined. A new type of distributed-type measuring transducer is proposed for the practical implementation of the two-frequency method — a stepwise heterogeneous coaxial resonator; its theoretical and experimental studies are carried out; its advantages in relation to the known transducers are determined. A hygrometer of the mid-frequency range based on a concentrated-type capacitive transducer and a hydrometer of a very high-frequency range based on a stepped heterogeneous coaxial resonator have been developed. The circuit solutions of the measuring transducer and the measuring generator of the hygrometer of the midfrequency range, which provided the minimum values of their parasitic capacitances, were developed and implemented. The circuit solutions of the measuring transducer and the measuring generator of a hygrometer of a very high frequency range have been developed and implemented, which provided almost zero effect of their parasitic capacitances. A methodology has been developed for conducting experimental research on the implementation of four- and three-frequency methods using a mid-range moisture meter and implementing a two-frequency method and a simplified version of it using a very high-frequency moisture meter. Experimental studies on manufactured test emulsions, as well as analysis and processing of their results, were carried out. For all developed multi-frequency methods and moisture values of test emulsions in the range of 10⁻⁴ – 10⁻², the value of the relative extended uncertainty of moisture measurement did not exceed 5.28 %. For the humidity of the test emulsion 10⁻⁵, the value of this uncertainty did not exceed 10.39 % (due to the lack of stability of the frequency of the reference generator frequency Ch 3 - 34, which was used in the research). The developed improved multi-frequency resonance dielectric methods for determining humidity have increased the sensitivity to a level of 10⁻⁵ while minimizing "varietal uncertainty".

Дисертація присвячена розробленню теоретичних і практичних засад побудови функціональних схем волоконно-оптичних вимірювальних перетворювачів механічних величин на базі інтерферометра на полімерному оптичному волокні. Проведено теоретичне узагальнення основних фізичних властивостей спекл-структур, які формуються на виході багатомодових полімерних оптичних волокон внаслідок міжмодової інтерференції, з точки зору їх можливого використання в якості інформативного параметру для метрологічних застосувань. На основі результатів досліджень запропоновано новий підхід до розроблення волоконно-оптичних сенсорів та вимірювальних перетворювачів механічних величин на базі багатомодових полімерних оптичних волокон. Розроблений метод опрацювання сигналів інтерферометра на полімерному оптичному волокні, який базується на прямому кореляційному порівнянні розподілів інтенсивності опорного та поточного спекл-зображень, дозволяє проводити автоматизований контроль параметрів деформації технічних об’єктів. В результаті досліджень механізму модуляції інтенсивності випромінювання в багатомодових полімерних волокнах при селективному збудженні мод запропоновано метод для вимірювання частоти механічних коливань та вібрації, який дозволяє підвищити ефективність перетворення модуляції фази в модуляцію інтенсивності випромінювання на виході волокна. Проведені в роботі дослідження щодо опрацювання та інтерпретації сигналів вимірювальних перетворювачів на багатомодових полімерних волокнах можуть слугувати основою для створення контрольно-вимірювальних приладів, призначених для дослідження різних фізичних полів, а також контролю та діагностики напружено-деформованого стану технічних об’єктів. Враховуючи механічні властивості чутливих елементів вимірювальних перетворювачів на основі полімерних оптичних волокон, їх здатність до мультиплексування та створення протяжних каналів для передачі інформативного сигналу, можуть бути реалізовані розподілені волоконно-оптичні вимірювальні системи. Диссертация посвящена разработке теоретических и практических основ построения функциональных схем волоконно-оптических измерительных преобразователей механических величин на базе интерферометра на полимерном оптическом волокне. Проведено теоретическое обобщение основных физических свойств спекл-структур, которые формируются на выходе многомодовых полимерных оптических волокон в результате межмодовой интерференции, с точки зрения их возможного использования в качестве информативного параметра для метрологических приложений. На основе результатов исследований предложен новый подход к разработке волоконно-оптических сенсоров и измерительных преобразователей механических величин на базе многомодовых полимерных оптических волокон. Разработанный метод обработки сигналов интерферометра на полимерном оптическом волокне, основанный на прямом корреляционном сравнению распределений интенсивности опорного и текущего спекл-изображений, позволяет проводить автоматизированный контроль параметров деформации технических объектов. В результате исследований механизма модуляции интенсивности излучения в многомодовых полимерных волокнах при селективном возбуждении мод предложен метод для измерения частоты механических колебаний и вибрации, который позволяет повысить эффективность преобразования модуляции фазы в модуляцию интенсивности излучения на выходе волокна. Проведенные в работе исследования по разработке и интерпретации сигналов измерительных преобразователей на многомодовых полимерных волокнах могут служить основой для создания контрольно измерительных приборов, предназначенных для исследования различных физических полей, а также контроля и диагностики напряженно-деформированного состояния технических объектов. Учитывая механические свойства чувствительных элементов измерительных преобразователей на основе полимерных оптических волокон, их способность к мультиплексирования и создания протяженных каналов для передачи информативного сигнала, могут быть реализованы распределенные волоконнооптические измерительные системы. The thesis is devoted to the development of theoretical and practical principles of construction functional schemes of fiber optic measuring transducers of mechanical values based on polymer optical fiber interferometer. Theoretical generalization of the main physical properties of speckle structures formed at the output of multimode polymer optical fibers due to intermodal interference for their possible use as an informative parameter for metrological applications was conducted. Based on the research results, a new approach to the development of fiber-optic sensors and measuring transducers of mechanical values based on multimode polymer optical fibers is proposed. The developed method for processing signals of polymer optical fiber interferometer which is based on a direct correlation comparison of the intensity distributions between the reference and current speckle images allows to carry out automated control of the deformation parameters of technical objects. As a result of studies of the mechanism of radiation intensity modulation in multimode polymer fibers with selective excitation of modes, a method for measuring the frequency of mechanical oscillations and vibrations is proposed, which allows increasing the efficiency of phase modulation conversion into the modulation of radiation intensity. Researches in the processing and interpretation of measuring transducers on multimode polymer fibers can be used as a basis for the creation of control and measuring devices designed to study different physical fields, as well as for control and diagnosis of stress-strain state of technical objects. Given the mechanical properties of the sensitive elements of measuring transducers based on polymer optical fibers as well as their ability for multiplexing and creating long channels for information signal transmission, distributed fiber-optic measuring systems can be implemented.

Aim of this thesis is a verification of possibility to measure displacement in small range using sensor based on the principle of strain gauge. For testing purspose, an evaluating unit was designed, made and assembled. This unit contains analog/digital converter, LCD and it has an abbility to move measuring plane using stepper motor. Next part of this thesis is about testing new prototype of strain gauge sensor, including evaluation of results of measuring. The performed measurements were measuring linearity, time stability and repeatability. Based on the results of the measurements, the possibility of using this type of length measuring device was confirmed for further development.

Dissertation submitted in compliance with the requirements for the Master's Diploma in Technology: Electrical Engineering (Light Current), Technikon Natal, 1987.
In the gold mining industry, one of the significant physical properties of the mineral slurry is its density and it is important to be able to measure this parameter in most processes. There are many techniques for determining the density of fluids, but because of the hostile, abrasive nature of mineral slurry, very few of these are suitable, This dissertation describes the deveiopment, construction and testing of a portable, ultrasonic, density measuring instrument. The instrument uses an ultrasonic transducer as the primary measuring element, and system operation is based on the fact that the driving impedance of the transducer varies with changes in the physical properties, and hence the characteristic impedance, of the surrounding medium into which the ultrasonic energy is being transferred. The technique may a-Lao be used to measure the relative concentrations of two liquids in a mixture or emulsion, provided that the characteristic impedances of the liquids are sufficiently dissimilar. The electronic circuitry is fairly straightforward, consisting essentially of an oscillator, driving circuit for the transducer and a voltage monitor to provide a d.c. voltage proportional to the impedance of the transducer, and hence to the density of the surrounding medium. Most of the research has been concentrated on the probe design, as the type of transducer, the type and thickness of facing material and the method of construction all contribute to the sensitivity of the instrument. A design of probe assembly has been developed that may be used for both slurry density measurement and the measurement of the ratio of aqueous to organic liquids in emulsion.
M

This thesis examines the dynamics of the formation of tethers, which are tubes of lipids 20 - 200 nm in diameter. In particular, this work investigates how the loading rate affects the observed threshold force at which a tether forms from a vesicle membrane. Tether dynamics are important to a myriad of biological processes such as signaling when white blood cells adhere to the walls of healthy and diseased blood vessels, or in the transport of intracellular material between neighboring cells. To understand the dynamics of tether formation in such systems more fully, the studies presented in this thesis focus on the dependence of the force needed to create a tether on the rate of force change. To conduct these experiments, I combined, for the first time, a microfabricated magnetic force transducer, or a microscale device that generates well-controlled and localized magnetic fields, and microaspiration, a technique to apply known tension to a lipid membrane. Using the combined global and local mechanical control of the joint system, I discovered a strong correlation between the threshold force of tether formation and the applied force ramp. An energy model, based upon that used to describe membrane rupture, characterized the observed dependencies and provided a mechanism to examine physically relevant quantities within the system. The usefulness of this combined approach was further substantiated by determining the influence of membrane modulators, including cholesterol, tension, adhesion site concentration, and phosphatidylserine, on the dependence seen between force threshold and force rates. Additionally, application of the experimental technique developed in this thesis led to the calculation of the inter-layer drag coefficient between membrane leaflets and to the first measurements of the thermal expansivity in aspirated 1-stearoy1-2-oleoyl- sn -glycero-3-phosphatidylcholine vesicles. This new tool for dynamic studies of membrane mechanics may further be extended to study how tethers form off of flowing cells or how phase regimes, induced by the presence of cholesterol, influence membrane dynamics.

The present work focused on the implementation and validation of an in-flight thrust measuring system using onboard instrumentation. This system was integrated and tested onboard the 01¬harapo UAV, from the Aerospace Sciences Department of University of Beira Interior, resulting from the need to have a fully equipped and instrumented flying test bed to assess and validate variable span wings prototypes using morphing technologies. This system comprises a force transducer (load cell) and a compatible signal conditioner which filters and amplifies the load cell signal. An infra-red temperature sensor was also added to the system in order to correct the thrust readings for temperature effects. The load cell signal conditioner and temperature sen¬sor communicate with the UAV flight management unit which works as data acquisition system. The in-flight parameters regarding propeller thrust and load cell temperature can be real-time monitored. The load cell was completely characterised in terms of its calibration curves both within and without the compensated range. Then, an assessment was conducted to quantify the UAV transmission shaft friction magnitude. Thereafter, with both the load cell calibration curves and with the friction compensation equation, the final in-flight thrust equations were found and implemented into the UAV flight management unit. At this stage, the entire in-flight thrust measuring system was characterized in terms of its performance, that is, in terms of its non-repeatability, non-linearity, hysteresis and creep. Regarding the system validation process, in-flight and wind tunnel tests were performed. These tests were conducted for different air¬speeds and different throttle settings in order to obtain thrust values for different propeller advance ratios. An uncertainty analysis was also carried out with the aim of attaining the accu¬racy and precision level of the various results obtained. ln general, for lower throttle settings (below 35% of the full throttle), the system seems to have low sensitive to measure low thrust magnitudes. Nevertheless, and despite all the factors that had a negative effect on the mea¬suring system accuracy, for throttle settings above 35% the in-flight thrust values showed a satisfactory agreement with the corresponding wind tunnel ones. For future system iterations, a few enhancements were proposed as well.
O presente trabalho focou-se na implementação e validação de um sistema de medição de tração em voo usando instrumentação a bordo. O sistema foi integrado e testado a bordo da aeronave não tripulada "Olharapo", pertencente ao Departamento de Ciências Aeroespaciais da Universidade da Beira Interior, como necessidade de se ter uma plataforma aérea totalmente equipada e instrumentada a fim de se avaliarem e validarem protótipos de asas de envergadura variável recorrendo a tecnologias morphing. Este sistema é composto por um transdutor de força (célula de carga) e por um condicionador de sinal compatível, o qual filtra e amplifica o sinal da célula de carga. Um sensor de temperatura de infravermelhos foi também adicionado ao sistema com o intuito de corrigir as leituras de tração para efeitos de temperatura. O condicionador da célula de carga bem como o sensor de temperatura comunicam com a unidade de gestão de voo da aeronave não-tripulada, a qual funciona como sistema de aquisição de dados. Os parâmetros de voo relativos à tração da hélice e à temperatura da célula de carga são monitorizados em tempo real. A célula de carga foi completamente caracterizada em termos das suas curvas de calibração, tanto dentro como fora do seu compensated range. De seguida, foi conduzida uma avaliação para quantificar a magnitude do atrito do veio de transmissão da aeronave. Após, com ambas as curvas de calibração da célula de carga bem como com a equação de compensação do atrito, as equações finais para a tração foram encontradas e implementadas na unidade de gestão de voo da aeronave. Nesta fase, todo o sistema de medição de tração em voo foi caracterizado em termos do seu desempenho, isto é, em termos da sua não-repetibilidade, não linearidade, histerese e fluência. No que respeita ao processo de validação do sistema, foram conduzidos testes em voo e em túnel de vento. Estes testes foram realizados para diferentes velocidades de escoamento e para diferentes frações de acelerador de forma a obter valores de tração para diferentes razões de avanço da hélice. Um estudo de análise de incertezas foi também realizado a fim de se perceberem quais os níveis de precisão e exatidão dos diferentes resultados obtidos. No geral, para frações de acelerador reduzidas (abaixo dos 35%), o sistema parece ter pouca sensibilidade para medir baixas magnitudes de tração. No entanto, e apesar de todos os fatores que exerceram um efeito negativo na precisão do sistema, para frações de acelerador acima dos 35%, os resultados de voo exibem uma concordância satisfatória com os seus correspondentes obtidos em túnel de vento. Para futuras iterações do sistema, alguns melhoramentos são também propostos.

博士
國立成功大學
機械工程學系
102
Lens-less line-focused PVDF transducers and defocusing measurement method are applied to determine the dispersion curves of cylindrically guided waves, including Rayleigh-like cylindrical surface waves propagating along the circumferential direction of solid cylinders and layer-coated cylinders, as well as cylindrical Lamb waves on circular annuli. Conventional V(f,z) waveform processing method has been modified to cope with the non-linear relationship between the phase angle of wave interference and the defocusing distance. A cross correlation method is proposed to accurately extract the cylindrically guided wave velocity from measured data. Experiments have been carried out on: (1) stainless steel and glass cylinders, (2) Ni-coated stainless steel cylinders, and (3) cylindrically curved stainless steel sheets. The experimentally obtained dispersion curves are in very good agreement with their theoretical counterparts. Variation of cylindrically guided wave velocity due to the cylindrical curvature is quantitatively verified using this method. Line-focused PVDF transducers and its V(f,z) defocusing measurement system are also applied to determine the acoustoelastic and acoustoplastic effects of deformed polymethylmeth-acrylate (PMMA) samples, as well as silicon steel samples with permanent deformation. Different levels of strain or permanent deformation are formed in PMMA and silicon steel samples. Large plastic deformation ranging from 5% to 30% is created in the silicon steel samples using uni-axial tensile loading. The velocity changes of surface acoustic waves under different strain or plastic deformation are measured along various directions relative to the loading direction. The acoustoelastic coefficients of PMMA are successfully determined from measurement results. The acoustoplastic effects of PMMA and silicon steel samples are also measured and determined. The investigation on the acoustoelastic and acoustoplastic effects demonstrates an effective way for estimating applied and/or residual stresses in solid materials nondestructively using the line-focused PVDF transducer and its measurement method.

Die vorliegende Arbeit untersucht, wie die genaue Kenntnis der Sende- und Empfangsschallfelder eines Ultraschallwandlers zur Entwicklung neuer Meßverfahren genutzt werden kann. Insbesondere werden dargestellt: - ein neuartiges, nichtscannendes Verfahren zur Bestimmung der Krümmung eines Reflektors, basierend auf der Analyse der Wellenfrontkrümmung reflektierter Schallfelder - ein neuartiges, nichtinvasives Verfahren zur Bestimmung der Schallgeschwindigkeit in einer Flüssigkeit durch Auswertung der Echosignale von im Ausbreitungsmedium vorhandenen Streupartikeln und - ein Verfahren zur Wandlercharakterisierung durch Messungen in Fluiden mit Streupartikeln, sowie verschiedene Zuordnungen von Schallfeldmerkmalen zu spezifischen Eigenschaften eines Ultraschallwandlers. Im Zusammenspiel von Simulation und Experiment konnten die Funktionstüchtigkeit aller Meßverfahren nachgewiesen und vielversprechende innovative Ansätze für zukünftige Entwicklungen angeregt werden: 1. Das nichtscannende Verfahren zur Krümmungsmessung erlaubt bei guter Justage eine Krümmungsbestimmung von Reflektoren mit Radien zwischen 6 und 11 mm mit einer Unsicherheit von ungefähr 0,5 mm. In Kombination mit herkömmlichen scannenden Verfahren bietet es Ansätze zur präzisen Größenbestimmung von Fehlern in der zerstörungsfreien Prüfung. 2. Das Verfahren zur nichtinvasiven Schallgeschwindigkeitsmessung erlaubt eine Bestimmung von Schallgeschwindigkeiten mit einer statistischen Meßunsicherheit von 0,1 %. Mögliche Weiterentwicklungen zur Messung der Schallgeschwindigkeit mit örtlicher Auflösung und zur Gewinnung neuer Diagnosemöglichkeiten in Metallurgie (nichtinvasive Charakterisierung von Mischungsvorgängen) und Biomedizintechnik (nichtinvasive Temperaturmessung in Körpergewebe zur Überwachung der Hyperthermiebehandlung, Gewebecharakterisierung) werden erläutert. Aus verschiedenen bekannten sowie einem neuartigen, leicht anwendbaren Meßverfahren werden neue Schlüsse gezogen a) zur Bestimmung der akustisch effektiven Elementgröße von Wandlerelementen mittels Schallfeldmessungen, b) zur Qualitätssicherung im Hinblick auf Schallkopfasymmetrien und c) zur Verbesserung von Schallfeldsimulationen.
The current thesis explores how the precise knowledge of the sending and receiving sound fields of an ultrasonic transducer can contribute to the development of novel measuring techniques. Emphasis is placed on: - a novel, non-scanning method for the determination of the curvature radius of a spherical reflector, based on the analysis of the wave front curvature of the reflected sound field, - a novel non-invasive method for sound velocity measurements in fluids using the echo signals from scattering particles, and - novel conclusions on how to use well-known sound field measurement methods for transducer characterisation, as well as an introduction to a novel easy-to-use method for transducer characterisation exploiting the echo signals from scattering particles. Proof of concept is shown for all methods by simulation and measurement, and different promising improvements for further techniques are suggested: - The non-scanning method for curvature measurements makes it possible to determine reflector radii between 6 and 11 mm with an uncertainty of about 0.5 mm, provided that there is a good reflector alignment. In combination with conventional methods, a novel approach for the determination of the size of discontinuities in non-destructive testing is outlined. - The method for non-invasive sound velocity measurements allows the determination of sound velocity in homogeneous fluids with a statistical uncertainty of 0.1 %. Future improvements are suggested to allow sound velocity measurements with local resolution, which enables novel approaches for metallurgy (non-invasive characterisation of mixing processes) and biomedical engineering (non-invasive temperature control for hyperthermia treatment, tissue characterisation). - New conclusions are drawn based on well-established and a novel easy-to-implement measurement method regarding a) the determination of the acoustically effective element size of transducer elements, b) transducer asymmetries, thereby improving quality control, and c) the improvement of sound field simulations.