By shining a precisely tuned laser through an atomic vapor, we can determine local mag- netic field strength in scalar form and in a way that is not affected by temperature changes. This technology has been used in space many times before on missions flown by NASA and ESA, such as SWARM, Øersted, and CHAMP to calibrate accompanying vector mag- netometers which are subject to offsets caused by temperature changes. The device we constructed is a small, low-cost application of this scientific principle and opens up new areas of scientific possibility for cubesats and the ability to define geomagnetic field struc- tures on a small (<10km) scale as part of the ANDESITE cubesat mission being developed at Boston University. Previously, magnetic sensors in orbit have been flown individually on a single spacecraft or in very small groups such as the International Sun-Earth Exporers (ISEE) and SWARM which each used three separate spacecraft. This method of analyzing the geomagnetic field cannot provide a spatial or time resolution smaller than that of the separation between magnetic field readings. This project has focused on producing a tabletop demonstra- tion of a compact sensor head which could enable measurements on unprecedented small scales. Toward this end we have accomplished the construction and preliminary testing of a compact sensor head which contains all necessary elements to function as a scalar atomic magnetometer.

This thesis covers considerations regarding commercially availble magnetic field sensors and the design work and assembly of a 3-axis magnetic field sensor of Hall technology that is tested for use in a cryostat at the FREIA laboratory, Uppsala university. The assembled sensor needs to withstand cryogenic temperatures and a high vacuum environment. A design for a mechanical structure that will be able to move a matrix of multiple sensors inside the cryostat is also covered. A short section discusses magnetoresistance magnetic field sensors for these purposes. The assembled sensor withstood a cryogenic test and a vacuum test separately, but it did start to show an odd behavior in a specific temperature range towards the last cycles of the cryogenic test. The printed ciruit board didn't show any damage on the board or the solder joints after operation in the vacuum environment.

This diploma thesis deals with selection, construction and realization of measuring device of magnetostatic field and description of the basic laws used in magnetism. It also describes principles and functions of particular sensors and probes curently used for measuring of magnetic fields, especially fluxgate magnetometer, which has been constructed. The result of this work is a particular realisation of measuring device with functional testing measurements.

[pt] Ensaios imunológicos em amostras biológicas são baseados em métodos que quantificam a ligação antígeno-anticorpo através de um marcador ligado ao anticorpo. Recentemente, métodos magnéticos de detecção têm sido aplicados através da utilização de marcadores contendo nanopartículas magnéticas em seu interior. Isto pode levar a um diagnóstico precoce de determinadas patologias como tumores, doenças auto-imunes, etc. Com este objetivo, construímos um magnetômetro para realizar esta caracterização. Utilizamos uma sonda Hall triaxial, um eletroímã alimentado por uma fonte de corrente bipolar e um sistema posicionador de precisão. Todos os componentes do magnetômetro foram controlados utilizando a linguagem LabView®. A interface com o usuário é extremamente versátil e é realizada através de um arquivo texto onde qualquer seqüência de campos magnéticos aplicado (de 0,2 mT à 1 T) a serem aplicados à amostra pode ser especificada. A performance do magnetômetro construído foi comparada com a de um magnetômetro comercial SQUID e um erro médio quadrático de 0.43% foi encontrado na magnetização da partículas de níquel para momentos magnéticos na ordem de 10-4 Am2. Finalmente, como exemplo de aplicação, nanopartículas de ferrita de cobalto com momento magnéticos na ordem de 10-5 Am2 foram recobertas com vários surfactantes e sua caracterização foi realizada utilizando o magnetômetro construído. / [en] Immunoassays in biological samples are based on methods that quantify the antigen-antibody link using a magnetic marker attached to the antibody. Recently, magnetic methods of detection have been applied using markers with magnetic nanoparticles in its interior. This can lead to early diagnosis of certain pathology such as tumors, autoimmune diseases etc. With this objective, built a magnetometer to perform this characterization. We use a tri-axial Hall probe, an electromagnet powered by a bipolar current source and a accurate positioner system. All components of the magnetometer were controlled using Lab View language. The interface with the user is extremely versatile and is made through a text file where any sequence of magnetic fields (from 0,2 mT to 1 T) to be applied to the sample can be specified. The performance of the built magnetometer was compared with a commercial SQUID magnetometer and an mean squared error of 0.43% was found in the magnetization of the particles of nickel for magnetic moments in the order of 10-4 Am2. Finally, as an example of application, nanoparticles of cobalt ferrite with magnetic moments in the order of 10-5 Am2 were coated with various surfactant and its characterization was performed using the built magnetometer.

M.Ing. / Vehicle attitude is the most significant of the navigational parameters in terms of its influence on accumulated dead reckoning errors. To determine the attitude of the host vehicle body, with respect to the earth, it is necessary to keep track of the orientation of the body axes with respect to the local earth navigational frame (north, east and down). The aim of this research is to investigate the feasibility and the enhancement of low cost inertial sensors (such as gyroscopes) by the addition of magnetometer and pitch and roll angle sensors. The focus of this research is on the use of low cost inertial measurement systems to determine the attitude of a vehicle body. Strapdown system principles and the estimation theory are applied to achieve this goal. Both Euler angles and Quatemions as attitude representation are implemented and compared with one another. Work is concentrated around the mathematical models for low cost sensors and the attitude system dynamics. A sensor cluster is constructed using three gyroscopes, a magnetometer and two inclinometers. These inertial sensors were integrated using a Kalman filter. The mathematics, calculations and principles used are universal for all attitude systems. Practical data was recorded after which it was filtered to illustrate the working of the Kalman filter. The addition of a magnetometer and two inclinometers are indeed feasible for enhancing the attitude obtained from the inertial sensors. The benefit associated with the gyroscopes, when the magnetometer readings are disturbed by external magnetic anomalies, where small and of little significance. This thesis fully describes the theory and approach followed to implement the Kalman filter, making this a good example of a Kalman filter implementation, especially with the MATLAB software realisation presented in the appendix.

[pt] Esta dissertação tem por objetivo o desenvolvimento de um transdutor magnético baseado no efeito da Magnetoimpedância Gigante (GMI – Giant Magnetoimpedance), destinado à medição de campos biomagnéticos. A motivação deste trabalho advém da inexistência de um sistema de baixo custo capaz de medir satisfatoriamente campos biomagnéticos, operando à temperatura ambiente e em plena conformidade com os princípios biometrológicos. Por sua vez, a metodologia experimental empregada iniciou-se pela medição e minuciosa análise das características de módulo e fase de sensores GMI em função do campo magnético, verificando-se suas dependências em relação ao comprimento das amostras e ao nível CC e frequência da corrente de excitação. Também, investigou-se a histerese e a homogeneidade das amostras GMI. Em seguida, foram idealizados circuitos eletrônicos para condicionamento e leitura das amostras GMI, destacando-se a estrutura desenvolvida que possibilita a leitura gradiométrica e algumas configurações inovadoras que permitem tanto a amplificação da sensibilidade de fase dos sensores GMI quanto a homogeneização das características de fase. Os resultados obtidos para o melhor transdutor magnético GMI desenvolvido, o qual é baseado na fase da impedância, apresentou uma elevada sensibilidade (250 mV/nT), indicando ganhos superiores a 1500 vezes quando comparado a protótipos baseados no módulo e, consequentemente, possibilitando alcançar novos patamares de resolução. Como conclusão ressaltase o grande potencial do magnetômetro GMI desenvolvido, caracterizado por seu baixo custo e elevada sensibilidade, quanto a sua aplicabilidade na medição de campos magnéticos ultra-fracos e, em especial, de campos biomagnéticos. Assim, o presente desenvolvimento contribui para a difusão das técnicas diagnósticas baseadas na medição de campos biomagnéticos, no ambiente clínico-hospitalar. / [en] This M.Sc. dissertation aims at developing a magnetic field transducer based on the Giant Magnetoimpedance (GMI) effect to be applied on the measurement of biomagnetic fields. The motivation of this work stems from the lack of a low cost system capable of adequately measuring biomagnetic fields, operating at room temperature and in full conformity with the biometrological principles. On the other hand, the experimental methodology began by measuring and carefully analyzing the impedance magnitude and phase characteristics of GMI sensors as a function of the magnetic field, verifying their dependencies on the length of the samples and on the DC level and frequency of the excitation current. It was also investigated the hysteresis and the homogeneity of GMI samples. In turn, the electronic circuits for conditioning and reading of GMI samples were developed, highlighting the developed structure that enables a gradiometric reading and some innovative configurations that allow both the enhancement of the impedance phase sensitivity of GMI sensors and the homogenization of their impedance phase characteristics. The results obtained for the best GMI magnetic transducer developed, which is based on the impedance phase, showed a high sensitivity (250 mV/nT), indicating gains of more than 1500 times when compared to magnitude-based prototypes and, consequently, reaching much better resolution levels. In conclusion it is emphasized the great potential of the developed GMI magnetometer, characterized by its low cost and high sensitivity, as to its applicability in measuring ultra-weak magnetic fields and in particular biomagnetic fields. Thus, the present development contributes to the spread of diagnostic techniques based on the measurement of biomagnetic fields, in clinical and hospital environments.

No description available.

Small satellites, and CubeSats in particular, have quickly become a hot topic in the aerospace industry. Attitude determination is currently one of the most intense areas of development for these miniaturized systems and future Cal Poly satellite missions will depend heavily on magnetometers. In order to utilize magnetometers as a viable source of attitude knowledge, precise calibration is required to ensure the greatest accuracy achievable. This paper outlines a procedure for calibrating and testing magnetometers on the next generation of Cal Poly CubeSates, utilizing a Helmholtz cage to simulate any desired orbital magnetic field that would be experienced by a spacecraft around Earth, as well as investigation of magnetic interference as a result of on-board electrical activity.

no / The Chalcolithic tell of Ghabristan in northwest Iran is now buried by alluvium and a magnetometer survey of the tell and its surroundings was undertaken to reveal any features under this cover. After the abandonment of the tell in the late third millennium BC it was used as an Iron Age cemetery by inhabitants of the neighbouring tell of Sagzabad. The magnetometer data show a related irregularly shaped channel that is also considered to be of Iron Age date.Its shallow burial depth, compared with the thick sedimentary layers underneath, indicates a considerable slowdown of alluviation rates in the second millennium BC, possibly related to environmental changes. The survey also found evidence for undisturbed buried building remains, most likely associated with copper workshops.

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