International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, California / Transducers have traditionally been incorporated into data systems by connecting the transducer to a signal conditioner that is then connected to a multiplexer with an Analog-to-Digital Converter (ADC). The signal conditioning, multiplexer and the ADC are usually included within the same assembly that is called a Data Acquisition Unit (DAU) or an encoder. A network centric data system allows the same architecture to be used if the interface to the encoder is changed to be a network interface. However, a network centric architecture allows other options as well. The signal conditioning and ADC can be included within the same package as the transducer and the assembly can be interfaced to the network. When this is combined with the processing capability now available, a whole new range of possibilities present themselves. The transducer can now be digitally processed to provide a linear output, it can be converted to Engineering Units, digitally filtered or have a host of other functions performed within the housing that contains the transducer. However, the network centric approach does not produce these advantages without some disadvantages. The major problem that needs to be solved is how we time stamp the data. With the encoder we could time stamp the PCM frame and be able to determine the time that a sample was taken from that information. Even in systems that convert the encoder to have a network interface, the time stamp needs to be affixed to the data in the encoder. With a network centric approach, the sample can be taken in the transducer and how to time stamp it becomes a real problem. This is a problem that must be considered at the system level. Some method of making time available at a low enough level in the system to allow transducer outputs to be time stamped is either a network issue or it requires a separate interface.

International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Current legacy acquisition systems such as the Advanced Airborne Test Instrumentation System (AATIS) are custom-built to each individual application with unique sensors and data modules. Replacing, adding, or subtracting sensors requires the system to be removed from service for days, weeks, or even months. This is a result of having to route special wires to each sensor and reprogramming the system with sensor information, calibration data, etc. AR sensor information must be contained in the main system since these systems do not have intelligence at the sensor level. If sensors were to contain information in their own IEEE 1451-compliant transducer electronic data sheet (TEDS), the main system would no longer have to be reprogrammed with this information. This information could then be obtained directly from the sensors when they are inserted into the system. A plug-n-play capability is being added to the system with the development of a standard interface to the system control unit (SCU). This interface, called a Multi-Network Capable Applications Processor (Multi-NCAP), will interface IEEE 1451-compliant smart transducer interface modules (STIMs) to the SCU in the AATIS as well as other legacy systems. With this development, maintenance and new configuration times for the AATIS and other legacy systems will be significantly reduced.

published_or_final_version / Physics / Doctoral / Doctor of Philosophy

This thesis studies the feasibility of utilizing Zigbee standard devices to create a shipboard wireless sensor network. Two primary methods were used to demonstrate feasibility. The first method demonstrated initial feasibility with a series of laboratory tests. The tests included range, reliability, and battery life tests. In the second portion, a prototype pressure sensor was created by matching a low power pressure transducer to a Zigbee modem via an integrated DAQ unit. Supporting software was generated using LabVIEW 6.0 to act as a server program and allow a remote Integrated Condition Assessment System (ICAS) workstation to log in via a TCP/IP connection and monitor sensor data. The expected contribution from the research effort would a completely wireless sensor network which would result in a net savings in man hours required to maintain and monitor. The sensor network would be reliable, relatively inexpensive, and entirely COTS available. With an extended battery life of 18 to 24 months, even the battery replacement could be fit into a standard annual or bi-annual PMS cycle, minimizing the workload to maintain. Initial feasibility testing was completed satisfactorily and the prototype sensor was successfully created and integrated to interface with the existing sensor infrastructure.

Ultrasonic technology is commonly used in the eld of Non-Destructive Testing (NDT) of metal structures such as steel, aluminium, etc. Compared to ultrasonic bulk waves that travel in infinite media with no boundary influence, Ultrasonic Guided Waves (UGWs) require a structural boundary for propagation such that they can be used to inspect and monitor long elements of a structure from a single position. The greatest challenges for any UGW system are the plethora of wave modes arising from the geometry of the structural element which propagate with a range of frequency dependent velocities and the interpretation of these combined signals reflected by discontinuities in the structural element. In this thesis, a technique is developed which facilitates the measurement of Time of Arrival (ToA) and group velocity dispersion curves of wave modes for one dimensional structures as far as wave propagation is concerned. A second technique is also presented which employs the dispersion curves to deliver enhanced range measurements in complex multimodal UGW responses. Ultimately, the aforementioned techniques are used as a part of the analysis of previously unreported signals arising from interactions of UGWs with piezoelectric transducers. The first signal processing technique is presented which used a combination of frequency-sweep measurement, sampling rate conversion and the Fourier transform. The technique is applied to synthesized and experimental data in order to identify different wave modes in complex UGW signals. It is demonstrated that the technique has the capability to derive the ToA and group velocity dispersion curve of the wave modes of interest. The second signal processing technique uses broad band excitation, dispersion compensation and cross-correlation. The technique is applied to synthesized and experimental data in order to identify different wave modes in complex UGW signals. It is demonstrated that the technique noticeably improves the Signal to Noise Ratio (SNR) of the UGW response using a priori knowledge of the dispersion curve. It is also able to derive accurate quantitative information about the ToA and the propagation distance. During the development of the aforementioned signal processing techniques, some unwanted wave-packets are identified in the UGW responses which are found to be induced by the coupling of a shear mode piezoelectric transducer at the free edge of the waveguide. Accordingly, the effect of the force on the piezoelectric transducers and the corresponding reflections and mode conversions are studied experimentally. The aforementioned signal processing techniques are also employed as a part of the study. A Finite Element Analysis (FEA) procedure is also presented which can potentially improve the theoretical predictions and converge to results found in experimental routines. The approach enhances the con dence in the FEA models compared to traditional approaches. The outcome of the research conducted in this thesis paves the way to enhance the reliability of UGW inspections by utilizing the signal processing techniques and studying the multimodal responses.

M.Ing. / Optical fibre Bragg gratings are a periodic variation of the refractive index in the core of an optical fibre andmay be formed by exposure to intense UV laser light under specific conditions. Light at a certain wavelength, called the Bragg wavelength, is reflected back when illuminating the grating with a light source. Bragg gratings can relatively easily be employed as strain and temperature sensors, but have small sensitivity for pressure. Special transducers are required to increase the sensitivity. A pressure sensor was manufactured by coating a fibre Bragg grating with a polymer. The polymer coating converts transverse pressure into longitudinal strain through the Poisson effect inside the polymer coating. This thesis investigates the sensitivity of themanufactured Bragg grating pressure sensor, by using the method of finite element analysis. An account of the experimental setup, whereby the Bragg grating is written with a frequency tripled Nd:YAG laser, is given. The process whereby the fibre is coated with the polymer is described. The sensor is characterized through experimental results and a comparison is made between theoretical and experimental results. Uses for this sensor and ways with which the sensitivity may be increased are suggested as future work.

Orientador: Fabrício Guimarães Baptista / Banca: Rogerio Andrade Flauzino / Banca: José Alfredo Covolan Ulson / Resumo: Esta dissertação de mestrado apresenta um estudo comparativo da sensibilidade de diferentes tipos de transdutores piezelétricos na detecção de dano em sistemas de SHM (Structural Health Monitoring - monitoramento de integridade estrutural) baseados na técnica da impedância eletromecânica (E/M). Foi realizada uma comparação de três transdutores piezelétricos: cerâmica de PZT (Pb-Lead Zirconate Titanate - titanato zirconato de chumbo), dispositivo MFC (Macro Fiber Composite - compósito de macro fibra) e diafragma piezelétrico, comumente conhecido como buzzer. Todos os testes foram realizados em barras de alumínio. A avaliação experimental da sensibilidade dos transdutores de PZT e MFC foi feita de uma maneira alternativa, utilizando o método PLB (Pencil Lead Break - quebra do grafite), o qual é muito simples e utilizado em sistemas de emissão acústica. Tem, como princípio, a quebra de grafite contra a estrutura a ser analisada. Os testes foram realizados em barras de alumínio de diferentes tamanhos. O dano estrutural foi induzido utilizando-se massas metálicas (porcas de aço), as quais foram fixadas, com cola a base de cianoacrilato, nas barras. A avalição dos resultados foi feita a partir da comparação dos índices de dano, obtidos das assinaturas da impedância elétrica dos transdutores de PZT e MFC, acoplados à estrutura a ser monitorada, e nos cálculos da PSD (Power Spectral Density) - densidade espectral de potência), obtida do método PLB e calculada usando o método Welch. Os resultados experimentais indicaram que os transdutores possuem sensibilidades diferentes para a detecção de dano, as quais também dependem da faixa de frequência. Em conclusão, os resultados mostraram uma boa relação entre os índices de dano e a PSD, indicando, dessa forma, que o método PLB pode ser uma boa ferramenta para estimar a sensibilidade na detecção de dano baseada na técnica da impedância E/M / Abstract: This dissertation presents a comparative study of the sensitivity of different types of piezoelectric transducers for damage detection in structural health monitoring (SHM), systems, based on the electromechanical impedance (EMI) technique. A comparison of three piezoelectric transduces was performed: PZT (Pb-Lead Zirconate Titanate) ceramic, MFC (Macro-Fiber Composite) device and piezoelectric diaphragm, also known as buzzer. The experimental evaluation of the sensitivity of the PZT and MFC transducers was performed in an alternative way using the pencil lead break (PLB) method, which is very simple and used in a acoustic emission (AE) systems. It is based on the break of a lead against the structure to be analyzed. The tests were carried out on aluminum beams of different sizes. The structural damage was induced by metallic mass (steel nts), which were fixed in the beams with cyanoacrylate glue. The evaluation of the results was made by comparing de damage indices obtained from the electrical impedance signatures of the PZT and MFC transducers coupled to the structure to be analyzed and the power spectral density (PSD) calculations obtained using the PLB and the Welch method. The experimental results indicated that the transducers have different sensitivities for the detection of damage, which also depend on the frequency range. The conclusion is that the results showed a good relationship between the damage indices and the PSD, indicating that the PLB method can be a useful tool to estimate the sensitivity in damage detection applications based on the EMI technique / Mestre

Orientador: Paulo Roberto de Aguiar / Banca: Danilo Hernane Spatti / Banca: Andre Luiz Andreoli / Resumo: A retificação é um processo de usinagem amplamente aplicado na fabricação de produtos que exigem baixa tolerância e alta precisão dimensional. Um dos danos mais comuns que ocorre durante este processo é a queima do material, que altera as propriedades mecânicas da peça usinada, comprometendo suas especificações. Sendo assim, o monitoramento da queima no processo de retificação é vital para garantir um alto nível de qualidade, produtividade e repetitividade dos processos industriais. Neste cenário, este trabalho traz uma nova abordagem não destrutiva para a identificação e localização da queima em aço SAE 1045, com o objetivo de desenvolver um sistema confiável e robusto de monitoramento da retificação como alternativa aos métodos invasivos, por meio do uso de transdutores piezelétricos de baixo custo e de técnicas de processamento digitais de sinais baseadas no critério estatístico de Hinkley. Comparado aos testes tradicionais e invasivos, como os testes de microdureza e metalografia, concluiu-se que o critério de Hinkley tem alta eficácia e potencial para localizar o início da queima da peça uma vez que o erro na localização foi menor que 4% / Abstract: Grinding is a machining process widely applied in the manufacture of products that require low tolerance and high dimensional accuracy. One of the most critical issues in this manufacturing process is the material burning phenomenon, which can lead the part to a total failure. Therefore, monitoring burning in the grinding process is vital to ensure a high level of quality, productivity and repeatability of industrial processes. In this sense, this article presents a new non-destructive approach for the onset location of burn in the SAE 1045 steel, aiming to develop a reliable and robust grinding monitoring system as an alternative to invasive methods. An experimental investigation was conducted by using low-cost piezoelectric diaphragms and feature extraction of the signals through Hinkley criterion. By comparing to the traditional and invasive tests such as microhardness measurements and metallographic analysis, it was concluded that the Hinkley criterion has a high effectiveness and potential to locate the onset of burning, once the error of the location was less than 4% / Mestre

No processo de indicação e adaptação do Aparelho de Amplificação Sonora Individual, as informações obtidas por meio dos Potenciais Evocados Auditivos de Longa Latência, geralmente pesquisado em campo livre, têm sido utilizadas para a avaliação dos benefícios e limitações dos dispositivos eletrônicos aplicados à surdez. O objetivo foi o de analisar de forma comparativa, a influência do transdutor no registro dos componentes P1, N1 e P2 eliciados por estímulo de fala, quanto à latência e amplitude, em crianças ouvintes. A casuística foi formada por 30 crianças ouvintes de quatro a 12 anos de idade de ambos os sexos. Os potenciais evocados auditivos de longa latência foram pesquisados por meio dos transdutores, fone de inserção e caixa acústica, eliciados por estímulo de fala /da/ apresentado com 526ms de intervalo interestímulos, na intensidade de 70dBNA e taxa de apresentação de 1,9 estímulos por segundo. A estimulação foi definida aleatoriamente, ora na orelha direita ora na esquerda, assim como a ordem do tipo do transdutor, iniciando ora pelo fone de inserção ora pela caixa acústica. Foram analisados os componentes P1, N1 e P2 quando presentes, quanto à latência e amplitude. Para verificar a reprodutibilidade dos registros, realizou-se uma análise de concordância entre a pesquisadora e um juiz, que mostrou um nível de concordância forte. Não houve diferença estatisticamente significante ao comparar os valores de latência e amplitude dos componentes P1, N1 e P2, para cada tipo de transdutor, considerando o sexo e orelha, assim como entre os tipos de transdutores utilizados ao comparar os valores de latências dos componentes do potencial evocado auditivo de longa latência. Entretanto, houve diferença estatisticamente significante na amplitude dos componentes P1 e N1 obtidos com os transdutores caixa acústica e fone de inserção, com maior amplitude para o transdutor caixa acústica. Os valores de latência dos componentes P1, N1 e P2 e amplitude de P2 obtidos com fone de inserção podem ser utilizados como referência para análise do registro obtido com o transdutor caixa acústica. / In the process of indication and fitting of Hearing Aids, the data obtained through Long Latency Auditory Evoked Potentials, generally researched in free field, have been utilized to assess the benefits and limitations of electronic devices applied to deafness. The goal was to analyze, in a comparative manner, the influence of the transducer on the recordings of components P1, N1 and P2, elicited through speech stimulus, as to the latency and amplitude, in hearing children. The sample was comprised of 30 hearing children aged 4-12 yrs, of both genders. The long latency auditory evoked potentials were researched by means of transducers, insertion phone and speakers, elicited through speech stimulus /da/ presented with 526ms of interstimuli interval, in the intensity of 70dBNA and presentation rate of 1.9 stimuli per second. The stimulation was randomly defined, sometimes on the right ear, sometimes on the left one, as well as the order of the type of transducer, beginning, sometimes, with the insertion phone, and sometimes, with the speaker. Whenever present, components P1, N1 and P2 were analyzed as to latency and amplitude. In order to verify the reproducibility of the recordings, an agreement analysis was carried out between the researcher and a referee, showing a strong agreement level. No statistically significant difference was seen when comparing the latency and amplitude values of components P1, N1 and P2, for each type of transducer, taking into account the gender and ear, as well as among the types of transducers utilized when comparing the latency values of the components of long latency auditory evoked potential. Nevertheless, there was a statistically significant difference in the amplitude of components P1 and N1, obtained with the speaker and insertion phone transducers, with greater amplitude for the speaker transducer. The latency values of components P1, N1 and P2 and amplitude of P2 obtained with the insertion phone may be utilized as a reference for the analysis of the recording obtained with the speaker transducer.

Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2015. / Immunosensors are analytical devices comprising antibody (Ab) molecules intimately integrated with electronic physicochemical transducers. Abs are responsible for specific recognition of an analyte so called antigen (Ag) while transducers are responsible for the conversion of chemical changes brought about by Ab-Ag interactions into measurable and processable signal. Amongst the many analytical tools, immunosensors have shown outstanding performance in applications in fields such as clinical diagnostics, agricultural purposes and environmental monitoring. They have come in place of the many conventional analytical methods which showed a number of disadvantages; high cost and longer time of operation, and requirement of highly knowledgeable personnel. On the other hand, immunosensors have shown potential to overcome these constraints. Their advantages include possibilities of portability, miniaturization, and simplified procedures. Of the possible fields of immunosensor applications, this study focussed on the environmental aspect. The safety of the environment is good for the well-being even though there are still some environmental threats that exist. Polychlorinated biphenyls (PCBs) have reportedly been found to be some of the potential substances to pose such threats due to their toxic and persistent behaviour. In this study, we have developed an electrochemical immunosensor as an analytical tool for the analysis and monitoring of PCBs. The development was based on the use of silver nanoparticles-doped polyaniline (PANI/Ag NPs) for modification of an electrode as a process for fabrication of the transducer. The PANI/Ag NPs composite was deposited on the glassy carbon (GC) and platinum (Pt) electrodes by oxidative electropolymerization of aniline in the presence of Ag NPs in 1 M HCl using cyclic voltammetry (CV) by ramping the potential from -0.1 to 1.4 V at 50 mV/s. The composite was then characterized and evaluated as a potential material for electrochemical transduction. Evaluation was on electroactivity, which is the main property of interest for materials used in the fabrication of electrochemical devices. The PANI composites were characterized using spectroscopic (FTIR), microscopic (TEM) and electrochemical CV techniques. Results confirmed the formation of PANI in its emeraldine form and the presence of Ag NPs. Characteristic functional groups and peaks of PANI were observed in FTIR and CV respectively. TEM micrograms showed one dimensional nanofibric tubes and crystalline-like structure of the composite. The incorporation of Ag NPs was indicated by the transition from the amorphous (PANI) to crystalline (PANI/Ag NPs) structure accompanied by increase in size as well as smoothness of the tubes. EDS-TEM counts increase of the chlorine (Cl) peaks is due to the closeness of these peaks to those of Ag, thus confirming incorporation of Ag NPs.