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Artur L. Ribeiro

Bio: Artur L. Ribeiro is an academic researcher from Technical University of Lisbon. The author has contributed to research in topics: Eddy current & Eddy-current testing. The author has an hindex of 5, co-authored 12 publications receiving 161 citations.

Papers
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Journal ArticleDOI
TL;DR: The main advantages of the proposed conductivity sensor include a wide measurement range, an intrinsic capability to minimize errors caused by fouling and polarization effects, and an automatic compensation of conductivity measurements caused by temperature variations.
Abstract: In this paper, a new four-electrode sensor for water conductivity measurements is presented. In addition to the sensor itself, all signal conditioning is implemented together with signal processing of the sensor outputs to determine the water conductivity. The sensor is designed for conductivity measurements in the range from 50 mS/m up to 5 S/m through the correct placement of the four electrodes inside the tube where the water flows. The implemented prototype is capable of supplying the sensor with the necessary current at the measurement frequency, acquiring the sine signals across the voltage electrodes of the sensor and across a sampling impedance to determine the current. A temperature sensor is also included in the system to measure the water temperature and, thus, compensate the water-conductivity temperature dependence. The main advantages of the proposed conductivity sensor include a wide measurement range, an intrinsic capability to minimize errors caused by fouling and polarization effects, and an automatic compensation of conductivity measurements caused by temperature variations.

83 citations

Journal ArticleDOI
TL;DR: In this article, an optimized uniform eddy current probe architecture including two planar excitation coils, a rectangular magnetic field biasing coil and a GMR magnetometer sensor array is presented.
Abstract: The usage of eddy current probes (ECP) with a single magnetic field sensor represents a common solution for defect detection in conductive specimens but it is a time consuming procedure that requires huge amount of scanning steps when large surface specimens are to be inspected. In order to speed-up the nondestructive testing procedure, eddy current probes including a single excitation coil and an array of sensing coils present a good solution. The solution investigated in this paper replaces the sensing coils for giant magneto-resistors (GMRs), due to their high sensitivity and frequency broadband response. Thus, the ECP excitation coil can be driven at lower frequencies than the traditional ones allowing defects to be detected in thicker structures. In this work an optimized uniform eddy current probe architecture including two planar excitation coils, a rectangular magnetic field biasing coil and a GMR magnetometer sensor array is presented. An ac current is applied to the planar spiral rectangular coil of the probe, while a set of GMR magnetometer sensors detects the induced magnetic field in the specimens under test. The rectangular coil provides the DC uniform magnetic field, assuring appropriate biasing of the GMR magnetometers of the probe, setting-up the functioning point on the linear region and at the same branch of the GMR static characteristics. The differences on the images obtained for the same specimen for each GMR are reduced if all sensors are biased on the same working point. Elements of the automated measurement system used to inspect the plate under test using the proposed eddy current probe, including a validation procedure based on a 2D template matching algorithm and the corresponding experimental results are included in the paper.

54 citations

Journal ArticleDOI
TL;DR: In this paper, a machine learning algorithm (support vector machine) is used to determine accurately the thickness of metallic plates, based on ECT measurements on real specimens, and an experimental validation procedure is presented with sets of samples with thickness up to 7.5mm.
Abstract: Eddy current testing (ECT) is a non-destructive technique that can be used in the measurement of conductive material thickness. In this work ECT and a machine learning algorithm (support vector machine – SVM) are used to determine accurately the thickness of metallic plates. The study has been made with ECT measurements on real specimens. At a first stage, a few number of plates is considered and SVM is used for a multi-class classification of the conductive plate thicknesses within a finite number of categories. Several figures of merit were tested to investigate the features that lead to “good” separating hyperplanes. Then, based on a SVM regressor, a reliable estimation of the thickness of a large quantity of plates is tested. Eddy currents are induced by imposing a voltage step in an excitation coil (transient eddy currents – TEC), while a giant magnetoresistance (GMR) is the magnetic sensor that measures the transient magnetic field intensity in the sample vicinity. An experimental validation procedure, including machine training with linear and exponential kernels and classification errors, is presented with sets of samples with thicknesses up to 7.5 mm.

28 citations

Proceedings ArticleDOI
23 May 2016
TL;DR: This paper presents the characterization of cracks in a metallic material using an eddy current testing technique called alternating current field measurement (ACFM), which is limited in the ability to detect cracks when induced currents flow parallel to it.
Abstract: This paper presents the characterization of cracks in a metallic material using an eddy current testing technique called alternating current field measurement (ACFM). This technique has already shown good results in the field of defect detection because, the current is forced to flow in a uniform direction, making it more predictable and easy to interpret the behavior of the induced current when a crack is present in the metal. However, this technique is limited in the ability to detect cracks when induced currents flow parallel to it. In this paper, a planar probe was built to remove this difficulty. The probe includes two planar coils that induce current in the conductor in different directions and two giant magnetoresistive (GMR) sensors positioned perpendicularly to each other to measure the two perpendicular components of the magnetic field. The Inverse problem technique was applied to get the current density maps from the magnetic field maps. 2D eddy current density images were obtained to visualize the crack geometry.

9 citations

Proceedings ArticleDOI
18 Feb 2014
TL;DR: In this article, a study concerning the disturbances in the magnetic field and in the lines of current due to a machined linear defect having different depths in order to extract relevant information that allows the determination of the defect characteristics is presented.
Abstract: One of the still open problems in the inspection research concerns the determination of the maximum depth to which a surface defect goes. Eddy current testing being one of the most sensitive well established inspection methods, able to detect and characterize different type of defects in conductive materials, is an adequate technique to solve this problem. This paper reports a study concerning the disturbances in the magnetic field and in the lines of current due to a machined linear defect having different depths in order to extract relevant information that allows the determination of the defect characteristics. The image of the eddy currents (EC) is paramount to understand the physical phenomena involved. The EC images for this study are generated using a commercial finite element model (FLUX). The excitation used produces a uniform magnetic field on the plate under test in the absence of defects and the disturbances due to the defects are compared with those obtained from experimental measurements. In order to increase the limited penetration depth of the method giant magnetoresistors (GMR) are used to lower the working frequency. The geometry of the excitation planar coil produces a uniform magnetic field on an area of around the GMR sensor, inducing a uniform eddy current distribution on the plate. In the presence of defects in the material surface, the lines of currents inside the material are deviated from their uniform direction and the magnetic field produced by these currents is sensed by the GMR sensor. Besides the theoretical study of the electromagnetic system, the paper describes the experiments that have been carried out to support the theory and conclusions are drawn for cracks having different depths.

6 citations


Cited by
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Reference EntryDOI
31 Oct 2001
TL;DR: The American Society for Testing and Materials (ASTM) as mentioned in this paper is an independent organization devoted to the development of standards for testing and materials, and is a member of IEEE 802.11.
Abstract: The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

3,792 citations

Journal ArticleDOI
TL;DR: The main requirements and the key ideas for each ports, sensing solution and also the challenges related to the calibration and testing of distributed sensing systems associated with the main equipment that compose the world largest ports, such as quayside cranes, automated guided vehicles for container handling and yard crane.
Abstract: Nowadays, the Internet of Things (IoT) can be considered an important technological revolution related to smart cities, smart homes, smart factories and smart ports implementations As the presence of smart sensing systems in ports becomes a reality, different operation areas are working today in automatic mode Examples of challenging projects related to smart ports in the IoT era can be found from Europe to Asia, to Australia, and to North America; in all of these new architecture implementations, sensing technologies play a key role This paper highlights the main requirements and the key ideas for each ports, sensing solution and also the challenges related to the calibration and testing of distributed sensing systems associated with the main equipment that compose the world largest ports, such as quayside cranes, automated guided vehicles for container handling and yard cranes Details of the architecture and operations and sensing systems for smart ports are described Communication standards for smart ports are discussed, and smart ports implementation examples regarding structural health monitoring are considered Conclusions and future research opportunities in the IoT era are addressed in the final section of the paper

162 citations

Journal ArticleDOI
TL;DR: In this paper, the authors provide a thorough review of the advances in sensor technology for measurement of common water quality parameters (pH, turbidity, free chlorine, dissolved oxygen, and conductivity) in drinking water distribution systems.
Abstract: Online drinking water quality monitoring technologies have made significant progress for source water surveillance and water treatment plant operation. The use of these technologies in the distribution system has not been favorable due to the high costs associated with installation, maintenance, and calibration of a large distributed array of monitoring sensors. This has led to a search for newer technologies that can be economically deployed on a large scale. This paper includes a brief description of important parameters for drinking water and current available technologies used in the field. The paper also provides a thorough review of the advances in sensor technology for measurement of common water quality parameters (pH, turbidity, free chlorine, dissolved oxygen, and conductivity) in drinking water distribution systems.

104 citations

Journal ArticleDOI
TL;DR: In this paper, a modified index, termed as the compensated zero-crossing frequency, can be obtained from the measured multifrequency inductance spectral data using the algorithm developed in this paper.
Abstract: Lift-off variation causes errors in eddy current measurement of nonmagnetic plates as well as magnetic plates For nonmagnetic plates, previous work has been carried out to address the issue In this paper, we follow a similar strategy, but try to reduce the lift-off effect on another index—zero-crossing frequency for magnetic plates This modified index, termed as the compensated zero-crossing frequency, can be obtained from the measured multifrequency inductance spectral data using the algorithm we developed in this paper Since the zero-crossing frequency can be compensated, the permeability of magnetic plates can finally be predicted by deriving the relation between the permeability and zero-crossing frequency from Dodd and Deeds method We have derived the method through mathematical manipulation and verified it by both simulation and experimental data The permeability error caused by liftoff can be reduced within 75%

82 citations

Journal ArticleDOI
TL;DR: Eddy current testing plays an important role in numerous industries, particularly in material coating, nuclear and oil and gas as mentioned in this paper. However, the eddy current testing technique still needs to focus on t...
Abstract: Eddy current testing plays an important role in numerous industries, particularly in material coating, nuclear and oil and gas. However, the eddy current testing technique still needs to focus on t...

78 citations