Improved Measurement of the Low-Frequency Complex Permeability of Ferrite Annulus for Low-Noise Magnetic Shielding

Yang, Ke; Lu, Jixi; Ding, M. D.; Zhao, Jiheng; Ma, Danyue; Li, Yang; Xing, Bozheng; Han, Bangcheng; Fang, Jiancheng

doi:10.1109/access.2019.2935034

Cited by 20 publications

(11 citation statements)

References 25 publications

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“…The complex permeability (µ = µ − iµ ) was measured using the impedance measurement method [10], [22]- [24]. This method has been demonstrated in the research on the ferrite shield in [10] and [24]. A toroidal coil with 16 turns was wound over the lid (shown in Fig.…”

Section: B Permeability Electrical Resistivity and Shielding Factormentioning

confidence: 99%

Study of Magnetic Noise of a Multi-Annular Ferrite Shield

Yang

et al. 2020

IEEE Access

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Ferrites are promising nonmetallic materials used for the fabrication of low-noise magnetic shields because they possess high permeability and high electrical resistivity. However, large-sized ferrite components are difficult to fabricate or machine. In this study, we develop a cylindrical ferrite shield that consists of five annuli and two lids with an inner volume of φ11.2 cm × 22.5 cm. Although this structure contains gaps between different components, it eases considerably the fabrication and machining process as compared to the entire module. The magnetic noise is measured by a spin-exchange relaxation-free atomic magnetometer, and the detrimental effects of the gaps are analyzed quantificationally using the finite element method. Our research results indicate that compared with the ferrite shield without gaps, the magnetization noise increases by 34.1%. Nonetheless, the magnetic noise at the center of the ferrite shield achieves 5.5f −1/2 fT, which is much lower than that of µ-metal shields with a similar size. If the gap width can be reduced to be smaller than 0.01 mm, the increase of the magnetization noise will be less than 4.9%, which can be negligible in practical applications. Our study provides a low-cost, readily available, and low-noise ferrite shield structure.

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Section: B Permeability Electrical Resistivity and Shielding Factormentioning

confidence: 99%

Study of Magnetic Noise of a Multi-Annular Ferrite Shield

Yang

et al. 2020

IEEE Access

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“…Therefore, there is inevitable magnetic noise. The magnetic noise of the common mu-metal magnetic shield is mainly dominated by Johnson magnetic noise ： Where: is the relative magnetic conductivity; k is the Boltzmann constant; T is the temperature; σ is the conductivity; t is the thickness of the magnetic shield; r is the radius of the magnetic shield; G is a constant related to the aspect ratio of magnetic shielded shapes [17][18][26][27]. As shown in FIGURE.2, the alkali metal gas chamber is the core component of the SERF magnetometer.…”

Section: B Magnetic Noise Analysismentioning

confidence: 99%

Multilayer Spindle Shaped Magnetic Shielding Device for SERF Atomic Magnetometer Application

et al. 2020

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Most of shielding devices currently used for SERF magnetometers are multilayer cylindrical magnetic shielding barrels. This paper studies a new multilayer spindle shaped magnetic shielding barrel for the spin exchange relaxation free (SERF) magnetometer shielding system and uses finite element method (FEM) to compare the analysis results. The results show that the shielding effect of the spindle shaped magnetic shielding barrel is better than the traditional cylindrical magnetic shielding barrel, while the volume is reduced by about 1/5 and the weight is reduced by about 1/4. Therefore, we expect that a smallsized, lightweight , low-cost and more efficient magnetic shielding device can be obtained.

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“…In the impedance measurement method, an impedance analyzer (LCR-meter) is used to obtain the resistance and inductance of the coil wound around the toroidal permalloy, allowing for the calculation of its complex permeability. Based on this method, Yang et al [20] used a linear fitting method to separate the wire resistance from the measured resistance. This not only eliminated the measurement error in imaginary permeability at low frequencies but also enhanced the accuracy of the impedance measurement method.…”

Section: Introductionmentioning

confidence: 99%

High-precision voltammetry method for measuring the permeability of permalloy at ultra-low-frequency magnetic field

Lu,

Hong,

Qiu

et al. 2023

Meas. Sci. Technol.

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The permeability of permalloy at ultra-low-frequency magnetic field is a crucial and fundamental parameter for analyzing the low frequency shielding factor of magnetically shielded rooms. However, due to limitations in the accuracy of the existing magnetic flux signal measuring system, the permeability at ultra-low-frequency magnetic field is challenging to precisely determine. Therefore, a high-precision voltammetry method for measuring the permeability of permalloy at ultra-low-frequency magnetic field is proposed in this paper. First, the theory of the voltammetry method and the required level of induced voltage accuracy are derived and thoroughly analyzed. Then, the voltage acquisition module with ultra-low noise is designed by using four parallel instrumentation amplifiers, and the magnitude of the noise is quantified by establishing the noise analysis model for the voltage acquisition module. Finally, the system for measuring the permeability at ultra-low-frequency magnetic field is set up, and its feasibility is verified by comparing the measurement results of permeability at 10 Hz with the commercial soft magnetic instrument. The results show that the system is capable of measuring the permeability of permalloy at 0.01 Hz to 1 Hz, with repeatability error of less than 3%. The method can also be applied to measure the permeability of other soft magnetic materials.

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Improved Measurement of the Low-Frequency Complex Permeability of Ferrite Annulus for Low-Noise Magnetic Shielding

Cited by 20 publications

References 25 publications

Study of Magnetic Noise of a Multi-Annular Ferrite Shield

Study of Magnetic Noise of a Multi-Annular Ferrite Shield

Multilayer Spindle Shaped Magnetic Shielding Device for SERF Atomic Magnetometer Application

High-precision voltammetry method for measuring the permeability of permalloy at ultra-low-frequency magnetic field

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