Current-Based High-Sensitivity Differential Detection of Light Power Using Si Photodiodes in Bridge Configuration for Chemical/Biological Optical Sensing☆

Abstract We present a new optoelectronic technique based on the differential measurement of currents for the detection of the variations of low concentrations of chemical and biological substances by measuring light power absorption through two Si-photodiodes (SiPD) in a bridge configuration. The solution exhibits high sensitivity, linear response and allows the compensation of the initial bridge unbalance without changing its elements so optimising signal amplification gain and detection resolution. The technique shows unique performances with respect to voltage amplitude measurements performed by lock-in amplifiers. Moreover, the experimental apparatus is simple and suitable for portable integrated sensor systems. Its main performances have been evaluated through a prototype PCB demonstrating the capability to detect light power variations with a settable maximum sensitivity of 30mV/nW and a resolution of 33pW

Système d'instrumentation multimodal de mesures d'activités physiologiques pour la prévention des blessures au travail

Présentement, suite à une blessure musculosqueletique, le patient doit retourner au centre de traitement pour faire des simulations de tâches dans lesquelles les intervenants font de l'observation visuelle ou prennent des mesures avec des systèmes encombrants. Ces tâches sont souvent non représentatives de la réalité et l'évaluation est subjective. L'analyse de l'activité musculaire et de la position du corps de façon précise est essentielle pour la prévention, le diagnostic et la réadaptation des blessures au travail. La solution proposée est un vêtement intelligent constitué d'une nouvelle fibre-électrode flexible intégrée à même le tissu pour un confort optimal. Les travaux abordés seront le développement d'un nouveau circuit d'instrumentation médical. Le système mesura l'activité musculaire par électromyographie de surface et la caractérisation du mouvement par une nouvelle fibre-électrode flexible. Cette nouvelle fibre-électrode a le potentiel de servir de capteur pour les deux mesures simultanément. Des circuits d'instrumentation seront explorés pour répondre à cet objectif. Ils seront basé sur un pont de Wheatstone et une méthode d'injection de courant. Les données d'électromyographie sont analysées pour monitorer la chute de la fréquence médiane du signal qui est signe précurseur de la fatigue musculaire. La mesure de position du corps avec la fibre est utilisée pour observer des changements dans la mécanique du mouvement qui engendrent un risque de blessure. Un algorithme de traitement du signal a été développé pour rehausser le signal par l'intermédiaire de la soustraction spectral. La transformation dans le domaine spectral sert aussi à requérir les informations physiologiques désirées.Currently, following a musculoskeletal injury, the patient must return to the treatment center to perform tasks simulations where a professional makes visual observation or take measurements with bulky systems. These tasks are often not representative of reality and the assessment is subjective. Analyzing muscle activity and body position accurately is essential for the prevention, diagnosis and rehabilitation of workplace injuries. The proposed solution is a smart garment made up of a new flexible fiber-electrode integrated into the fabric for an optimal comfort. The work will be to develop a new medical instrumentation circuit. The system will measure muscle activity by surface electromyography and characterization of movement by this new flexible fiber electrode. The fiber electrode has the potential to act as a sensor for both measurements simultaneously. Some instrumentation circuits will be explored to meet this objective. They will be based on a Wheatstone bridge and a current injection method. Electromyography data is analyzed to follow the drop in the median frequency of the signal which is a precursor sign of muscle fatigue. Measuring body position with the fiber is used to observe changes in the mechanics of movement that create a risk of injury. A signal processing algorithm has been developed to enhance the signal through spectral subtraction. The transformation in the spectral domain also serves to compute the request desired physiological information

Evolução metrológica de uma bancada de ensaios de ventiladores radiais

Dissertação (mestrado) - Univesidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-graduação em Engenharia MecânicaVentiladores são máquinas utilizadas para movimentar gases, com vazões altas e pressões baixas, transformando a energia mecânica do rotor em energia cinética e de pressão do fluido. Os ventiladores podem ser utilizados em diversas aplicações, desde industriais a comerciais. Diferenciam-se em primeira instância pela forma do rotor, sendo eles axiais ou centrífugos. Os ventiladores centrífugos podem ter as pás curvadas para frente, para trás ou retas. Cada tipo tem características próprias. Com a variação dos tipos de ventiladores, as suas características também mudam e o seu desempenho é alterado. Para levantar as curvas características de ventiladores industriais, utiliza-se bancadas de ensaio destinado a traçar as curvas características do ventilador ensaiado. Diante disso, esta dissertação descreve o desenvolvimento da instrumentação da bancada de ensaio utilizada como estudo de caso, bem como a análise metrológica dos resultados. A análise tem o objetivo de informar e garantir que as medições deverão estar, com certa probabilidade, dentro de uma faixa de valores. Isso torna as medições confiáveis e rastreáveis metrologicamente, tendo em vista que alterações no sistema de medição tornam-se específicas na determinação da diminuição das incertezas de medição. Para isso, foi proposta e desenvolvida a instrumentação da bancada, cujas implementações foram realizadas podendo-se medir torque, rotação, velocidade e vazão do escoamento, e as potências envolvidas. Desenvolveu-se também a programação para tratamento dos sinais provenientes dos sensores em cima da plataforma LabVIEW que realizada a análise metrológica pelo método diferente do tradicional ISO GUM, o Método de Monte Carlo, conhecido por gerar a função densidade de probabilidade. Diante dos resultados gerados, faz-se a análise do menor intervalo que contém 95% dos valores obtidosFans are machines used to move gas with high airflow rate and low pressure making the mechanical energy generated from the fans rotor into kinetics energy and the fluids pressure. These fan's can be used in many forms from industrial to commercial needs. The first way to classify them is by the type of rotor, either axial or centrifugal. Centrifugal fans may have their propellers straight, curved to front or back. Each type has its own characteristics. With many variations of these characteristics for each type of fan it is possible to achieve different performance rates. To get an accurate response curve from industrial fans it is used test bench to obtain such a curve for the fan been tested. For that these dissertation describes the development for the instrumentation of the test bench used in this studied case as well as the metrological analyses of results. The main objective of the analyses is to inform and ensure that the measurements must be with a probability certainty within a range of values. This makes the measurements trustable and traceable metrologically in a way that for any alteration in the measurement system are specific for the determination in minimizing the measurements uncertainty. To achieve these goals it is proposed and developed the instrumentation for the test bench which can perform measurements in torque, rotation, velocity and airflow rate, and the powers involved. It was developed a software to process the signals from sensors using the LabVIEW platform which performs the metrological analyses by a method different from the traditional ISO GUM, using the Monte Carlo method which is known for generating a probability density function. With the results generated it is analyzed the minimum interval which contains 95% of the obtained value