Configurações alternativas para magnetômetros ''fluxgate'' com núcleo amorfo

Kabata, Wanderli; Vitorello, Ícaro

doi:10.1590/s0102-261x2007000200005

Cited by 3 publications

(4 citation statements)

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“…A three-axis fluxgate magnetometer, constructed at INPE to collect data of the terrestrial magnetic field for geophysical studies (Kabata et al, 2004), is also used for the tests. This magnetometer is a second harmonic sensor with a ring core made of high permeability material, 6-81 molybdenum permalloy, similar to the MAGSAT magnetometer.…”

Section: Tests With a Real Fluxgate Magnetometermentioning

confidence: 99%

“…Research on ground-based fluxgate magnetometer has been conducted at INPE for several years to provide vector measurements of the magnetic field for regional studies of crustal magnetization (Kabata et al, 2004), and electrical currents flowing in the lithosphere and geospace (Vitorello et al, 2007), as well as in technological systems such as electrical power transmission lines (Trivedi et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

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Technical procedures to select basic parameters of a fluxgate magnetometer

Kabata¹,

Vitorello²

2011

Rev. Bras. Geof.

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ABSTRACT. In fluxgate magnetometers, the external magnetic field is generally measured from the second harmonic induced voltage in the pick-up coil. Thus, to improve the performance of a fluxgate magnetometer design, careful considerations should focus on some operational parameters and how to calibrate them to attain an optimal performance with a minimum intrinsic noise at the output. Basically, two main factors are considered: i) the output dependence on variations of the even harmonics amplitudes with the excitation current; and ii) adjustments for a perfect timely match between the core saturation and the time-width of the sampling. The best sensitivity of the magnetometer is obtained in a portion of the hysteresis curve where the 2 nd harmonic component predominates. Since this region depends on the amplitude of the excitation, it becomes necessary to calibrate the excitation amplitude in order to get the highest 2 nd harmonic amplitude in the pick-up coil. When the amplitude of the excitation current is modified, the amplitude of the even harmonics also changes, and consequently the magnetometer will operate below its optimal sensitivity, depending on how much the current has changed. Similar result is observed when the core is built with a different inductance (different number of wraps) which requires operational tests to be carried out to verify the level of the core saturation by adjusting the amplitude and the frequency to get the best performance from the magnetometer. Changes in the amplitudes of the excitation current generally occur with changes in the excitation current waveform, affecting the timing of the core saturation. To avoid bad synchronization between the excitation current and the sampling, the phase shift circuit is locked with the excitation current circuit in order to work together and variations on the excitation current phase is automatically corrected in the sampling circuit. In summary, finding the moment when the 2 nd harmonic has its greatest value, adjusting the time-width of the synchronous detector and avoiding phase's shifts between excitation and detection circuits can produce a magnetometer performing at its lowest noise output.Keywords: magnetometer, fluxgate, magnetic noise, vitrovac, computer simulations. RESUMO.Nos magnetômetros tipo fluxgate, o campo magnético externoé geralmente medido utilizando-se da tensão do segundo harmônico induzido na bobina de detecção. Assim, para melhorar o desempenho de um magnetômetro fluxgate, deve-se observar com cuidado alguns parâmetros operacionais e o modo de calibrá-los, com o objetivo de colocá-los num pontoótimo de operação. Basicamente dois fatores são considerados: i) a dependência das variações do segundo harmônico com a corrente de excitação; e ii) o ajuste perfeito entre a saturação do núcleo e a janela de amostragem. A melhor sensibilidadeé obtida em uma porção da curva de histerese onde o segundo harmônicoé predominante. Visto que essa região depende da amplitude da corrente de excitação, torna-se necessário calibrar esta...

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Section: Tests With a Real Fluxgate Magnetometermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Technical procedures to select basic parameters of a fluxgate magnetometer

Kabata¹,

Vitorello²

2011

Rev. Bras. Geof.

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“…Em um núcleo com alta permeabilidade, o fluxo que atravessa a Bobina de medição será muito grande, devido à concentração das linhas de compõem seu interior. Para a medição de um campo externo de interesse, é necessária a diminuição repentina da permeabilidade do meio, a qual implica em uma redução do fluxo magnético na Bobina de medição e permite a obtenção de uma tensão de saída proporcional ao campo externo [11][12].…”

Section: Sensores Magnéticosunclassified

“…Entretanto, apesar de, de fato, apresentarem resoluções significativamente melhores do que as exibidas pelas demais famílias de sensores magnéticos, na prática, as resoluções experimentalmente dos SQUIDs são piores do que este limite critico ideal, devido à interferência introduzida pela eletrônica de condicionamento e leitura, além de outras fontes de ruído [12].…”

Section: Sensores Magnéticosunclassified