F. Corrêa Alegria

Automatic calibration of analog and digital measuring instruments using computer vision

This paper presents an automatic calibration system capable of calibrating measuring instruments that do not have a digital interface. Image analysis algorithms are used to automatically determine the instrument reading. It can be used with analog and with digital displays. The maximum uncertainty in the detection of the pointers position in analog instruments is less than the human eye can discriminate.

Using the skin effect to estimate cracks depths in mettalic structures

This paper is concerned with the characterization of depth profiles defects in metallic structures. Experimental work using giant magnetoresistors (GMR) scanning automatically a metallic plate with eddy currents induced by an excitation coil has been carried out and is described. The results are analyzed in comparison with the simulation results obtained with a commercial finite element model for some test cases.

GMR based eddy current sensing probe for weld zone testing

The detection of flaws in the weld zone of conductive plates is an important issue and, in this field, different solutions using eddy current probes are mentioned in the literature. However, when eddy current pancake probes are used, it is difficult to detect the flaws or the welding non-uniformities due to the lift-off effects. Thus, in the present work we present a novel uniform eddy current probe architecture based on a tangential excitation coil with a rectangular geometry and highly sensitive giant magnetoresistances (GMR). The induced magnetic field is measured using a GMR sensor fixed on the axis midpoint inside the coil. The sensor sensitive axis is perpendicular to the excitation coil axis in order to measure only the induced magnetic fields caused by the presence of flaws. We developed an automatic testing system to characterize the sensor and to perform tests on aluminum plate specimens with flaws included in the weld zone.

City-wide mobile air quality measurement system

In this paper we present an air quality measurement system that can be used to generate a map of the air quality in a city. The system is made of stations that can be attached to buses and taxis and gather data about air quality along the day as they travel in the city. Each station has sensors to measure the concentration of different gases, a position sensor (GPS) and a GSM/GPRS communication module to transmit the data to a central server. Each station is self-sufficient in terms of energy through the use of a battery and solar panels. The data server can be accessed through the internet using a browser and presents the results in real time overlapped onto a Google map of the city indicating, with different colors, the concentration of each measured gas (CO, NO2, O3, SO2, and CO2).

Comparison between two digital methods for active power measurement

Active power can be estimated by digitizing the voltage and current waveforms during an integer number of periods and digitally processing the samples obtained. There are two methods that can be used: Discrete Integration and Spectral Analysis. In the first one the average of the sample-by-sample product of the two waveforms is computed. In the second one, sine fitting algorithms are used to estimate the amplitude and initial phase of each waveform. The values obtained are then used to compute the active power. Here we derive analytical expressions for the precision of both estimators as a function of the number of samples acquired and the amount of additive random noise present. These are useful to determine the confidence interval for the measurements made. We also compare the two estimators and conclude that the second one, using sine fitting, is sometimes better.

2D magnetic field mobile sensing system for eddy current testing

In this paper, a mobile probe for eddy current testing using inductive sensors and two optical computer mice for position determination is presented. It is a first step in developing an autonomous system that is able to detect flaws in the metallic structure of an aircraft. We present the system implemented and show results of its use to detect a rectangular flaw in a flat aluminum plate.

Optimization Of A Mass Spectrometry Process

In this paper we present and discuss a system developed in order to optimize the mass spectrometry process of an ion implanter. The system uses a PC to control and display the mass spectrum. The operator interacts with the I/O board, that interfaces with the computer and the ion implanter by a LabVIEW code. Experimental results are shown and the capabilities of the system are discussed.