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599 KiB

Open AccessArticle

Optical Fiber Relative Humidity Sensor Based on a FBG with a Di-Ureasil Coating

by Sandra F. H. Correia, Paulo Antunes, Edison Pecoraro, Patrícia P. Lima, Humberto Varum, Luis D. Carlos, Rute A. S. Ferreira and Paulo S. André

Sensors 2012, 12(7), 8847-8860; https://doi.org/10.3390/s120708847 - 27 Jun 2012

Cited by 109 | Viewed by 10350

Abstract

In this work we proposed a relative humidity (RH) sensor based on a Bragg grating written in an optical fiber, associated with a coating of organo-silica hybrid material prepared by the sol-gel method. The organo-silica-based coating has a strong adhesion to the optical [...] Read more.

In this work we proposed a relative humidity (RH) sensor based on a Bragg grating written in an optical fiber, associated with a coating of organo-silica hybrid material prepared by the sol-gel method. The organo-silica-based coating has a strong adhesion to the optical fiber and its expansion is reversibly affected by the change in the RH values (15.0–95.0%) of the surrounding environment, allowing an increased sensitivity (22.2 pm/%RH) and durability due to the presence of a siliceous-based inorganic component. The developed sensor was tested in a real structure health monitoring essay, in which the RH inside two concrete blocks with different porosity values was measured over 1 year. The results demonstrated the potential of the proposed optical sensor in the monitoring of civil engineering structures. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Portugal)

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1111 KiB

Open AccessArticle

An Intelligent Sensor Array Distributed System for Vibration Analysis and Acoustic Noise Characterization of a Linear Switched Reluctance Actuator

by José Salvado, António Espírito-Santo and Maria Calado

Sensors 2012, 12(6), 7614-7633; https://doi.org/10.3390/s120607614 - 07 Jun 2012

Cited by 5 | Viewed by 7818

Abstract

This paper proposes a distributed system for analysis and monitoring (DSAM) of vibrations and acoustic noise, which consists of an array of intelligent modules, sensor modules, communication bus and a host PC acting as data center. The main advantages of the DSAM are [...] Read more.

This paper proposes a distributed system for analysis and monitoring (DSAM) of vibrations and acoustic noise, which consists of an array of intelligent modules, sensor modules, communication bus and a host PC acting as data center. The main advantages of the DSAM are its modularity, scalability, and flexibility for use of different type of sensors/transducers, with analog or digital outputs, and for signals of different nature. Its final cost is also significantly lower than other available commercial solutions. The system is reconfigurable, can operate either with synchronous or asynchronous modes, with programmable sampling frequencies, 8-bit or 12-bit resolution and a memory buffer of 15 kbyte. It allows real-time data-acquisition for signals of different nature, in applications that require a large number of sensors, thus it is suited for monitoring of vibrations in Linear Switched Reluctance Actuators (LSRAs). The acquired data allows the full characterization of the LSRA in terms of its response to vibrations of structural origins, and the vibrations and acoustic noise emitted under normal operation. The DSAM can also be used for electrical machine condition monitoring, machine fault diagnosis, structural characterization and monitoring, among other applications. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Portugal)

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525 KiB

Open AccessArticle

Dynamic Structural Health Monitoring of Slender Structures Using Optical Sensors

by Paulo Antunes, Rui Travanca, Hugo Rodrigues, José Melo, José Jara, Humberto Varum and Paulo André

Sensors 2012, 12(5), 6629-6644; https://doi.org/10.3390/s120506629 - 18 May 2012

Cited by 23 | Viewed by 9158

Abstract

In this paper we summarize the research activities at the Instituto de Telecomunicações—Pólo de Aveiro and University of Aveiro, in the field of fiber Bragg grating based sensors and their applications in dynamic measurements for Structural Health Monitoring of slender structures such as [...] Read more.

In this paper we summarize the research activities at the Instituto de Telecomunicações—Pólo de Aveiro and University of Aveiro, in the field of fiber Bragg grating based sensors and their applications in dynamic measurements for Structural Health Monitoring of slender structures such as towers. In this work we describe the implementation of an optical biaxial accelerometer based on fiber Bragg gratings inscribed on optical fibers. The proof-of-concept was done with the dynamic monitoring of a reinforced concrete structure and a slender metallic telecommunication tower. Those structures were found to be suitable to demonstrate the feasibility of FBG accelerometers to obtain the structures’ natural frequencies, which are the key parameters in Structural Health Monitoring and in the calibration of numerical models used to simulate the structure behavior. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Portugal)

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812 KiB

Open AccessArticle

Sensor Integration in a Low Cost Land Mobile Mapping System

by Sergio Madeira, José A. Gonçalves and Luísa Bastos

Sensors 2012, 12(3), 2935-2953; https://doi.org/10.3390/s120302935 - 02 Mar 2012

Cited by 26 | Viewed by 8912

Abstract

Mobile mapping is a multidisciplinary technique which requires several dedicated equipment, calibration procedures that must be as rigorous as possible, time synchronization of all acquired data and software for data processing and extraction of additional information. To decrease the cost and complexity of [...] Read more.

Mobile mapping is a multidisciplinary technique which requires several dedicated equipment, calibration procedures that must be as rigorous as possible, time synchronization of all acquired data and software for data processing and extraction of additional information. To decrease the cost and complexity of Mobile Mapping Systems (MMS), the use of less expensive sensors and the simplification of procedures for calibration and data acquisition are mandatory features. This article refers to the use of MMS technology, focusing on the main aspects that need to be addressed to guarantee proper data acquisition and describing the way those aspects were handled in a terrestrial MMS developed at the University of Porto. In this case the main aim was to implement a low cost system while maintaining good quality standards of the acquired georeferenced information. The results discussed here show that this goal has been achieved. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Portugal)

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473 KiB

Open AccessArticle

LOLS Research in Technology for the Development and Application of New Fiber-Based Sensors

by João Coelho, Marta Nespereira, Catarina Silva and José Rebordão

Sensors 2012, 12(3), 2654-2666; https://doi.org/10.3390/s120302654 - 28 Feb 2012

Cited by 5 | Viewed by 7048

Abstract

This paper presents the research made at the Laboratory of Optics, Lasers and Systems (LOLS) of the Faculty of Sciences of University of Lisbon, Portugal, in the field of fiber-based sensors. Three areas are considered: sensor encapsulation for natural aqueous environments, refractive index [...] Read more.

This paper presents the research made at the Laboratory of Optics, Lasers and Systems (LOLS) of the Faculty of Sciences of University of Lisbon, Portugal, in the field of fiber-based sensors. Three areas are considered: sensor encapsulation for natural aqueous environments, refractive index modulation and laser micropatterning. We present the main conclusions on the issues and parameters to take in consideration for the encapsulation process and results of its design and application. Mid-infrared laser radiation was applied to produce long period fiber gratings and nanosecond pulses of near-infrared Q-switch laser were used for micropatterning. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Portugal)

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Review

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517 KiB

Open AccessReview

Optical Sensors Based on Plastic Fibers

by Lúcia Bilro, Nélia Alberto, João L. Pinto and Rogério Nogueira

Sensors 2012, 12(9), 12184-12207; https://doi.org/10.3390/s120912184 - 05 Sep 2012

Cited by 291 | Viewed by 15787

Abstract

The recent advances of polymer technology allowed the introduction of plastic optical fiber in sensor design. The advantages of optical metrology with plastic optical fiber have attracted the attention of the scientific community, as they allow the development of low-cost or cost competitive [...] Read more.

The recent advances of polymer technology allowed the introduction of plastic optical fiber in sensor design. The advantages of optical metrology with plastic optical fiber have attracted the attention of the scientific community, as they allow the development of low-cost or cost competitive systems compared with conventional technologies. In this paper, the current state of the art of plastic optical fiber technology will be reviewed, namely its main characteristics and sensing advantages. Several measurement techniques will be described, with a strong focus on interrogation approaches based on intensity variation in transmission and reflection. The potential applications involving structural health monitoring, medicine, environment and the biological and chemical area are also presented. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Portugal)

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430 KiB

Open AccessReview

Fiber Optic-Based Refractive Index Sensing at INESC Porto

by Pedro A. S. Jorge, Susana O. Silva, Carlos Gouveia, Paula Tafulo, Luis Coelho, Paulo Caldas, Diana Viegas, Gaspar Rego, José M. Baptista, José L. Santos and Orlando Frazão

Sensors 2012, 12(6), 8371-8389; https://doi.org/10.3390/s120608371 - 18 Jun 2012

Cited by 28 | Viewed by 9687

Abstract

A review of refractive index measurement based on different types of optical fiber sensor configurations and techniques is presented. It addresses the main developments in the area, with particular focus on results obtained at INESC Porto, Portugal. The optical fiber sensing structures studied [...] Read more.

A review of refractive index measurement based on different types of optical fiber sensor configurations and techniques is presented. It addresses the main developments in the area, with particular focus on results obtained at INESC Porto, Portugal. The optical fiber sensing structures studied include those based on Bragg and long period gratings, on micro-interferometers, on plasmonic effects in fibers and on multimode interference in a large spectrum of standard and microstructured optical fibers. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Portugal)

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1823 KiB

Open AccessReview

Optical Triangulation-Based Microtopographic Inspection of Surfaces

by Manuel F. M. Costa

Sensors 2012, 12(4), 4399-4420; https://doi.org/10.3390/s120404399 - 29 Mar 2012

Cited by 27 | Viewed by 10443

Abstract

The non-invasive inspection of surfaces is a major issue in a wide variety of industries and research laboratories. The vast and increasing range of surface types, tolerance requirements and measurement constraints demanded during the last decades represents a major research effort in the [...] Read more.

The non-invasive inspection of surfaces is a major issue in a wide variety of industries and research laboratories. The vast and increasing range of surface types, tolerance requirements and measurement constraints demanded during the last decades represents a major research effort in the development of new methods, systems and metrological strategies. The discreet dimensional evaluation the rugometric characterization and the profilometric inspection seem to be insufficient in many instances. The full microtopographic inspection has became a common requirement. Among the different systems developed, optical methods have the most important role and among those triangulation-based ones have gained a major status thanks to their flexibility, reliability and robustness. In this communication we will provide a brief historical review on the development of optical triangulation application to the dimensional inspection of objects and surfaces and on the work done at the Microtopography Laboratory of the Physics Department of the University of Minho, Portugal, in the development of methods and systems of optical triangulation-based microtopographic inspection of surfaces. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Portugal)

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