21 research outputs found
Photonic Crystal Fiber Interferometer for Dew Detection
A novel method for dew detection based on photonic crystal fiber (PCF) interferometer that operates in reflection mode is presented in this paper. The fabrication of the sensor head is simple since it only involves cleaving and fusion splicing. The sensor shows good sensitivity to dew formation with a large wavelength peak shift of the interference pattern at the onset of dew formation. The device’s response to ambient humidity and temperature are also studied and reported in this paper. From our experiment it is also concluded that by attaching a thermoelectric cooler with temperature feedback, the sensor head demonstrated can be used as a miniature dew point hygrometer
Sensores em fibra óptica para aplicações biomédicas
Tese de mestrado. Engenharia Biomédica. Faculdade de Engenharia. Universidade do Porto, Faculdade de Ciências. Universidade do Porto, INESC Porto. 200
Aspects of Respiratory Heat Transfer in Asthma
During the winter some asthma suffers are incapable of exertion without provoking bronchoconstriction. The rate of respiratory heat exchange (RHER) is proposed as a stimulus of exercise induced asthma. A respiratory test was required to determine heat loss sensitivity. A pumped cold air supply was developed (-2
Generic wireless sensor network for dynamic monitoring of a new generation of building material
Existing testing methods for building materials before deployment include a series of
procedures as stipulated in British Standards, and most tests are performed in a controlled
laboratory environment. Types of equipment used for measurements, data logging, and
visualisation are commonly bulky, hard-wired, and consume a significant amount of
power. Most of the off-the-shelf sensing nodes have been designed for a few specific
applications and cannot be used for general purpose applications. This makes it difficult
to modify or extend the sensing features when needed. This thesis takes the initiative of
designing and implementing a low-powered, open-source, flexible, and small-sized
Generic wireless sensor network (GWSN) that can continuously monitor the building
materials and building environment, to address the limitations of the conventional
measurement methods and the technological gap.
The designed system is comprised of two custom-made sensor nodes and a gateway, as
well as purpose designed firmware for data collection and processing. For the proof of
concept and experimental studies, several measurement strategies were designed, to
demonstrate, evaluate, and validate the effectiveness of the system. The data was
collected from selected case study areas in the School of Energy, Geoscience,
Infrastructure and Society (EGIS) laboratories by measuring and monitoring building
structures and indoor environment quality parameters using the designed GWSN. The
measured data includes heat flux through the material, surface and air temperatures on
both sides of the material/structure, moisture variation, ambient temperature, relative
humidity, carbon dioxide, volatile organic compounds, particulate matter, and
sound/acoustic levels.
The initial results show the potential of the designed system to become the new
benchmark for tracking the variation of building materials with the environment and
investigating the impact of variation of building materials on indoor environment quality.
Based on the estimates of the thermal performance data, the sample used in the
experiment had a typical U-value between 4.8 and 5.8 W/m2K and a thermal resistance
value of 0.025m2
·K/W[1][2]. Thermal resistance values from the GWSN real-time
measurement were between 0.025 and 0.03 m2K/W, with an average of 0.025 m2K/W,
and thermal transmission values varied between 4.55 and 5.11 W/m2K. Based on the data
obtained, the results are within the range of typical values[3]. For thermal comfort measurements, the results of humidity and temperature from GWSN
were compared to values in the Kambic climatic chamber in the EGIS laboratory, and the
accuracies were 99 % and 98 % respectively. For the IAQ measurements, the values of
CO2 and TVOCs were compared to the commercial off-the-shelf measuring system, and
the accuracies were 98 %, and 97 %. Finally, the GWSN was tested for acoustic
measurements in the range of 55 dB to 106 dB. The results were compared to class one
Bruel & Kjaer SLM. The accuracy of GWSN was 97 %. The GWSN can be used for in lab and in-situ applications, to measure and analyse the thermal physical properties of
building materials/building structures (thermal transmittance, thermal conductivity, and
thermal resistance). The system can also measure indoor air quality, thermal comfort, and
airborne sound insulation of the building envelope. The key point here is to establish a
direct link between how building materials vary with the environment and how this
impacts indoor environment quality. Such a link is essential for long-term analysis of
building materials, which cannot be achieved using current methods.
Regarding increasing the power efficient of the implemented GWSN as well as its
performance and functionality, a new sensing platforms using backscatter technology
have been introduced. The theory of modulation and spread spectrum technique used in
backscattering has been explored. The trade-off between hardware complexity/power
consumption and link performance has been investigated.
Theoretical analysis and simulation validation of the new sensing technique, using
backscatter communication, has been performed. A novel multicarrier backscatter tag
compatible with Wireless Fidelity has been implemented and an IEEE 802.11g OFDM
preamble was synthesized by simulation. The tag consists of only two transistors with
current consumption no larger than 0.2 μA at voltage of less than 0.6 V.
Novel harmonic suppression approaches for frequency-shifted backscatter
communication has been proposed and demonstrated. The proposed approaches
independently manipulate mirror harmonics and higher order harmonics whereby;
specified higher order harmonics can be removed by carefully designing the real-valued
(continuous and discrete) reflection coefficients-based backscatter tags.
When successfully implemented, the backscatter system will reduce sensor node power
consumption by shifting the power-consuming radio frequency carrier synthesis functions
to carrier emitters.Engineering and Physical Sciences Research
Council (EPSRC) Funding EP/H009612/
Metrologia óptica com fibra polimérica
Doutoramento em FísicaO presente trabalho teve por objectivo global o estudo e desenvolvimento de
sensores baseados em fibra óptica polimérica. O crescimento da tecnologia
polimérica nos últimos anos permitiu a introdução deste tipo de fibras ópticas
na área das telecomunicações e no desenvolvimento de sensores. As
vantagens associadas à metrologia óptica com fibra polimérica têm vindo a
atrair as atenções da comunidade científica dado que permitem o
desenvolvimento de sistemas de baixo-custo ou custo competitivo face às
tecnologias convencionais.
Dada a actualidade do tema proposto, descreve-se, numa primeira fase, a
tecnologia em fibra óptica polimérica existente no mercado e o estado de arte
de sensores em fibra óptica polimérica. Segue-se a descrição de dois tipos de
sensores baseados em modulação de intensidade.
Projectou-se um sensor extrínseco capaz de avaliar a quantidade de luz
dispersa e absorvida por partículas suspensas num líquido. Foi efectuada a
caracterização do sensor quanto à concentração de partículas suspensas,
tamanho e reflectividade. O sensor foi testado no âmbito da monitorização
ambiental, designadamente, na análise de turbidez em amostras de
sedimentos recolhidos em áreas ardidas. O sistema desenvolvido foi
comparado com um sistema comercial.
Um sensor intrínseco, baseado no polimento lateral de fibra óptica polimérica,
foi analisado analiticamente. O modelo teórico avalia o sensor em diferentes
condições de macroencurvamento e de índice de refracção do meio
envolvente. O modelo teórico foi validado positivamente através de resultados
experimentais. Foi avaliada a sensibilidade à temperatura e os conhecimentos
adquiridos foram aplicados no desenvolvimento de um sistema capaz de
monitorizar a cura de diferentes materiais. É ainda apresentada uma técnica
para melhorar a sensibilidade do sensor de curvatura através da aplicação de
um revestimento na zona sensível.
A dependência na curvatura da potência transmitida por uma fibra óptica polida
lateralmente serviu de base ao desenvolvimento de uma joelheira e de uma
cotoveleira instrumentada, capazes de avaliar quantitativamente o movimento
articular. A necessidade de portabilidade levou ao desenvolvimento de um
sistema sem fios para aquisição e transmissão de dados. Espera-se que os
protótipos desenvolvidos venham a ter um impacto significativo em sistemas
futuros aplicados à medicina física e reabilitação.The global aim of this thesis was the study and development of optical sensors
based on plastic optical fibre. The recent advance of polymer technology
allowed the introduction of this type of optical fibre in telecommunications and
sensor design. The advantages of optical metrology with plastic fibre have
attracted attention from the scientific community because it allows the
development of low-cost or cost competitive systems compared with
conventional technologies.
Given the relevance of the topic, the current plastic optical fibre technology and
the state of the art of plastic optical fibre optic sensors are described. Two
types of intensity-based sensors are presented.
An extrinsic sensor was designed in order to measure the amount of scattered
and absorbed light by particles suspended in a liquid. The characterisation of
the sensor was accomplished with respect to the concentration of the
suspended particles, size and reflectivity. The sensor was tested in
environmental monitoring, particularly, in the analysis of turbidity in sediment
samples collected from burned areas and compared to a commercial system.
An intrinsic sensor based on side-polished plastic optical fibre was analytically
analysed. The theoretical model assesses the sensor performance in different
conditions of curvature and refractive index of the surrounding media. The
theoretical model has been positively validated by experiments. The sensitivity
of the sensor to the temperature was also evaluated and the knowledge
acquired was applied to the development of a pressure sensor and a system
capable of monitoring the cure of different materials. A technique for improving
the sensor sensitivity is also presented by the application of a coating on the
sensitive area.
The dependence of the transmitted power of a side-polished plastic optical fibre
on the curvature was used in the development of a system for monitoring knee
and elbow angle. These devices allowed the quantitative assessment of the
human motion. The need of portability led to the introduction of a wireless data
transmission system. It is expected that the developed prototypes will play an
important role in future physical medicine and rehabilitation systems.POPH; FCT; FS
Uurimus Eesti rahvusliku orelikultuuri ajaloolisest kujunemisest ja 21. sajandi orelihariduse jätkusuutlikkusest
http://tartu.ester.ee/record=b2654411~S1*es
Modern Telemetry
Telemetry is based on knowledge of various disciplines like Electronics, Measurement, Control and Communication along with their combination. This fact leads to a need of studying and understanding of these principles before the usage of Telemetry on selected problem solving. Spending time is however many times returned in form of obtained data or knowledge which telemetry system can provide. Usage of telemetry can be found in many areas from military through biomedical to real medical applications. Modern way to create a wireless sensors remotely connected to central system with artificial intelligence provide many new, sometimes unusual ways to get a knowledge about remote objects behaviour. This book is intended to present some new up to date accesses to telemetry problems solving by use of new sensors conceptions, new wireless transfer or communication techniques, data collection or processing techniques as well as several real use case scenarios describing model examples. Most of book chapters deals with many real cases of telemetry issues which can be used as a cookbooks for your own telemetry related problems