O presente trabalho enfoca o estudo de transdutores indutivos de deslocamento linear. Dentre os diversos dispositivos dessa natureza, procurou-se desenvolver um estudo mais aprofundado do transdutor indutivo diferencial com núcleo de esferas. O desenvolvimento experimental, com a construção de quatro protótipos, levou ao projeto de um transdutor com características adequadas ao uso industrial. / The present work focuses on the study of inductive transducers of linear displacement. Among the several devices of that nature, a more detailed study of the inductive differential transducer was attempted with core of spherical balls. The experimental development of four prototypes resulted in a transducer with characteristics adequate for industrial use to be designed.

O presente trabalho enfoca o estudo de transdutores indutivos de deslocamento linear. Dentre os diversos dispositivos dessa natureza, procurou-se desenvolver um estudo mais aprofundado do transdutor indutivo diferencial com núcleo de esferas. O desenvolvimento experimental, com a construção de quatro protótipos, levou ao projeto de um transdutor com características adequadas ao uso industrial. / The present work focuses on the study of inductive transducers of linear displacement. Among the several devices of that nature, a more detailed study of the inductive differential transducer was attempted with core of spherical balls. The experimental development of four prototypes resulted in a transducer with characteristics adequate for industrial use to be designed.

O presente trabalho enfoca o estudo de transdutores indutivos de deslocamento linear. Dentre os diversos dispositivos dessa natureza, procurou-se desenvolver um estudo mais aprofundado do transdutor indutivo diferencial com núcleo de esferas. O desenvolvimento experimental, com a construção de quatro protótipos, levou ao projeto de um transdutor com características adequadas ao uso industrial. / The present work focuses on the study of inductive transducers of linear displacement. Among the several devices of that nature, a more detailed study of the inductive differential transducer was attempted with core of spherical balls. The experimental development of four prototypes resulted in a transducer with characteristics adequate for industrial use to be designed.

Background: Registering a true maximum bite force on the most commonly-used force transducers is problematic. It is often believed that this is related mainly to discomfort and the fear of breaking teeth. Objectives: The aim of the project was to compare the suitability of different bite force measuring transducers including ones which were designed to improve subject comfort. The transducers used were a traditional strain-gauge transducer with and without covering with ethylene vinyl acetate (EVA) sheets, and a newly-developed pressure transducer. Methods: Five separate studies were performed in this project. The experiments were carried out on human volunteer subjects (aged 24 to 41 years). They were all dentate with no missing anterior teeth and with no crowns on these teeth. The following procedures were used in some or all of the studies: measurement of MVBF, electrical stimulation of the masseter muscle, and EMG recording from two pairs of jaw closing muscles. Results: The highest MVBF values were recorded on the pressure transducer, mean (± S.D.) 464 N ± 224 N; followed by the strain-gauge transducer with EVA sheets, 243 ± 80 N; and last of all the strain-gauge transducer with silicone indices, 165 ± 35 N; or acrylic indices, 163 ± 82 N. Significantly higher maximum potential bite forces were predicted by twitch interpolation for the pressure transducer (730 ± 199 N) than for the strain-gauge transducer with EVA sheets, 354 ± 67 N (Paired t test, P < 0.05). Significantly higher EMGs of the masseter and anterior temporalis muscles were found to be associated with MVBFs on the pressure transducer than with MVBFs on the strain-gauge transducer with EVA sheets (Paired t test, P < 0.05). Conclusions: It is concluded that: a) the pressure transducer system and to a lesser extent the strain-gauge transducer covered with EVA sheets seemed to overcome the fear associated with biting on the hard surfaces of the strain-gauge transducer alone; b) the pressure transducer may have some multi-directional capabilities which allow for total bite forces, or at least larger parts of them, to be recorded than on a uni-directional strain-gauge transducer.

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ITC/USA 2005 Conference Proceedings / The Forty-First Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2005 / Riviera Hotel & Convention Center, Las Vegas, Nevada / There are increasing demands, particularly from government agencies, to perform uncertainty analysis in order to assign accuracy bounds to telemetered data from environmental measuring transducers (pressure, acceleration, force, strain, temperature, etc.). Several requirements must be fulfilled before measurement uncertainty analysis is justified. These requirements include good measurement system design practices such as adequate low- and high-frequency response and data-sampling rates, appropriate anti-aliasing filter selection^(1), proper grounding and shielding, and many more. In addition, there are applications (e.g., flight test) in which the environment of the transducer varies with time and/or location. In these applications, it is a requisite that data-validation be performed to establish that an individual transducer responds only to the environmental stimulus that it is intended to measure. Without this validation component designed into the telemetry system, assigned accuracy bounds can be totally meaningless. This paper presents examples and describes techniques for data validation of signals from environmental measuring transducers.

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Approved for public release; distribution is unlimited / The MiniCan hydrophone is a small, easy to build, preamplified hydrophone with similar characteristics in sensitivity and self noise to larger and more expensive commercial devices. Previous work on the design showed a very promising performance, though it proved to have a flat sensitivity response of only up to 14 kHz. Unknown were also the effects that the aluminum housing parts produced on the overall response and whether the cable of the hydrophone had some influence on the sensitivity. A new design was built and tested changing the dimensions of the aluminum housing for the hydrophone, resulting in an increase in the region of flat sensitivity response up to 20 kHz and acceptable response up to 30 kHz, due to an increase of the lowest mechanical resonance of the hydrophone. A resonance testing device was built to investigate the mechanical characteristic of the components of the design, discovering that the first resonance of the aluminum base of 34.6 kHz caused the first overall resonance of the assembled device. Measurements of the influence of the cable showed an acoustic variation of about 1 dB in relative response in the range of interest, which is up to 30 kHz. The measurements proved that better performance can be achieved on the basic MiniCan design by increasing the resonant frequency of the aluminum body housing component. / Lieutenant, Chilean Navy

Orientador: Nobuo Oki / Banca: Aparecido Augusto de Carvalho / Banca: Tony Inácio da Silva / Resumo: Este trabalho descreve um sistema de extração de potência de power harvesting utilizando transdutores piezelétricos. Com o objetivo de extrair a máxima potência e assim ter um maior rendimento do sistema, foram projetados e testados alguns circuitos eletrônicos. Um circuito de controle com componentes discretos e de baixo consumo foi projetado para controle da chave do retificador chaveado e bias-flip. A energia extraída será utilizada para alimentar um sistema de aquisição de dados e um sensor de temperatura associado a este sistema. O sistema de power harvesting é constituído por uma estrutura mecânica, transdutor piezelétrico, circuito retificador e um conversor CC-CC. Na estrutura mecânica está localizado o transdutor piezelétrico e este transdutor proporciona a conversão de energia mecânica em energia elétrica. Para efeito deste estudo considera-se que o transdutor piezelétrico comporta-se como uma fonte de tensão alternada, que será retificada e armazenada em um supercapacitor, para depois ser utilizada na alimentação do sistema de aquisição de dados. Os conversores CC-CC são utilizados para maximizar a quantidade de energia obtida do transdutor piezelétrico e fornecer tensão ao supercapacitor. No entanto, uma das limitações desses sistemas é a baixa quantidade de energia gerada por esses dispositivos. Assim, para que haja uma minimização das perdas dos circuitos eletrônicos e possa se extrair a máxima potência possível do piezelétrico obtendo um melhor rendimento do sistema, este trabalho investigará a utilização dos circuitos retificadores em ponte, retificador em ponte chaveado, retificador bias-flip e o conversor buck-boost, além de utilizar a energia armazenada para alimentar um sistema de aquisição de dados associados a um sensor de temperatura... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This work describes several circuits for power extracting of power harvesting systems using piezoelectric transducers. In order to extract the maximum power and to achieve the maximum performance of these systems some electronic circuits were projected and tested. A control circuit with discrete components and low power consumption is designed to control switch of the switch-only and bias-flip rectifier. The goal is that the energy extracted is used to supply power electronic devices. That will be, in this work, a temperature sensor that is placed in a difficult access area. The power harvesting system is composed by a mechanical structure, a piezoelectric transducers, a rectifier and a DC-DC converter. The piezoelectric transducers were placed in the mechanical structure, these transducers are responsible to convert mechanical energy into electrical energy. In this work the piezoelectric transducer was considered an AC voltage source. This voltage will be rectified and then stored in supercapacitor, to be used in electronic circuits. The DC-DC converters were used to achieve maximum power from piezoelectric transducer and to supply voltage to the supercapacitor. However, one of the limitations of these systems is the low amount of power generated by the transducer. This way, it is mandatory to reduce the losses at the electronic components and extract the maximum power possible from the piezoelectric to improve the performance. This work investigates the full-bridge rectifier, switch-only rectifier, bias-flip rectifier and buck- boost converter, besides it aims to use the stored energy to supply a temperature sensor. Using the flip-bias rectifier improves the power up to 200%, and the switch-only rectifier by 150% in relation to full-bridge rectifier. And the efficiency changed from 35% (full-bridge)... (Complete abstract click electronic access below) / Mestre