Method for Selective Detection of Magnetic Flux Sources, Using a System of Superconductors, a Ferromagnetic Substance, and a Magnetic Sensor.

Pengukuran tanpa musnah bahan feromagnet dan gangguan medan magnet frekuensi rendah memerlukan penderia medan magnet yang mempunyai kepekaan yang tinggi dan stabil. Magnetometer yang berasaskan prinsip fluxgate dan memenuhi ciri-ciri yang diperlukan telah dibina dengan menggunakan teras gelang ferit. Teras gelang ferit ini dipacukan dengan sumber arus untuk mencapai keadan histerisis. Gelung pengesan yang dililit merentasi gelang ferit akan mengesan perubahan medan magnet yang berlaku pada gelang ferit tersebut. Teknik pengesanan yang digunakan adalah berasaskan pengesanan harmonik kedua oleh suatu pengesan fasa. Penderia fluxgate yang dibina adalah murah mudah dibina, mampu mengesan arah medan magnet dan tahan lasak. Kata kunci: Fluxgate; penderia medan magnet; histerisis; feromagnet Non–Destructive measurements of ferromagnetic material and low frequency magnetic flux distrubance require a highly sensitive and stable magnetic sensor with directional capabilities. A magnetometer based on fluxgate principle that meets the requirement had been developed using a ferrite ring core. The ferrite ring core is excited by an excitation current source to achieve hysteresis condition. The pick up coil that is wound across the ring core will pick up the magnetic flux generated in the ring core. This sensing method is based on the conventional type of fluxgate magnetometer with detection of second harmonics by a phase sensitive detector. Major advantages of the fluxgate magnetometer are low cost, directional, easy to construct, reliable and rugged. Key words: Fluxgate; magnetic sensor; hysteresis; ferromagnetic

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Non-Destructive Testing with Magnetic Sensor Using Rotational Magnetic Flux

IEEE Translation Journal on Magnetics in Japan ◽

10.1109/tjmj.1992.4565368 ◽

1992 ◽

Vol 7 (3) ◽

pp. 241-249

Author(s):

M. Enokizono ◽

S. Nagata

Keyword(s):

Magnetic Flux ◽

Magnetic Sensor ◽

Non Destructive Testing ◽

Destructive Testing ◽

Non Destructive

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Amplitude Control Method of Magnetic Flux Vertical Modulation Structure for TMR Magnetic Sensor Based on Harmonic Component of Modulated Signal

Micromachines ◽

10.3390/mi12060722 ◽

2021 ◽

Vol 12 (6) ◽

pp. 722

Author(s):

Junsheng Zhang ◽

Mengchun Pan ◽

Qingfa Du ◽

Jiafei Hu ◽

Kun Sun ◽

...

Keyword(s):

Magnetic Flux ◽

Control Method ◽

Amplitude Ratio ◽

Second Harmonic ◽

Harmonic Component ◽

Low Frequency ◽

Magnetic Sensor ◽

Modulation Method ◽

Temperature Drift ◽

Amplitude Control

Magnetic flux vertical modulation method based on piezoelectric resonance can reduce the 1/f noise of tunnel magnetoresistance (TMR) magnetic sensor and significantly improves the low-frequency magnetic field detectivity. However, the amplitude variation of the modulation structure will lead to the instability of the sensor output. In order to improve the amplitude stability of the modulation structure, an amplitude control method based on the amplitude ratio of the first and second harmonic components of the modulated signal was proposed. Compared with the piezoelectric or capacitive feedback method, this method does not require an independent amplitude conversion circuit, and has the advantages of simple structure, high control efficiency and strong anti-interference ability. The experimental results showed that the amplitude and temperature drift of the modulated structure was significantly suppressed, which is of great significance for enhancing the adaptability of the TMR magnetic sensor to the application environments.

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