Nagoya-shi, Japan
Nagoya-shi, Japan

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Muramatsu K.,Saga University | Gao Y.,Saga University | Yoneyama Y.,Giken Kogyo Co. | Sakai A.,Giken Kogyo Co. | And 5 more authors.
2015 IEEE International Magnetics Conference, INTERMAG 2015 | Year: 2015

To shield magnetic noise, magnetically shielded rooms (MSR) are used for biomagnetic measurements, etc. To evaluate the shielding factor SF (SF=Bn / Bs, Bn and Bs are the flux densities at the center of the room without and with MSR, respectively), the magnetic noise is applied by coils. However, SF depends on the size and position of the coils, so the standard of JEITA (Japan Electronics and Information Technology Industries Association) EM-4502, in which the shielding factor (SFo) of MSR for the uniform magnetic field in the extremely low-frequency region of less than 1 Hz without eddy current effect is estimated using coils within 10% error [1-2], has been already published [3]. Currently, a standard method for the low-frequency region, e.g. 50 Hz, with eddy current effect is being discussed. In a previous work [4], it was shown that the coil should be placed in front of the door of MSR and a much larger estimation error than 10% should be permitted for practical use in the standard to estimate SFo for the low-frequency region. © 2015 IEEE.


Muramatsu K.,Saga University | Gao Y.,Saga University | Yoneyama Y.,Giken Kogyo Corporation | Sakai A.,Giken Kogyo Corporation | And 6 more authors.
IEEE Transactions on Magnetics | Year: 2014

The standard of Japan Electronics and Information Technology Industries Association EM-4502, in which the shielding factor (SFo) of magnetically shielded rooms (MSRs) for the uniform magnetic field can be estimated using coils within 10% error for the extremely low-frequency region of <1 Hz without eddy current effects, has been already published. In this paper, to establish standard methods for evaluating SF for low-frequency region using coils, the effects of the setting method, size, and distance from MSR of the coils on SF are investigated by a linear eddy current analysis of an actual MSR made of copper and permalloy plates. It is shown that the coil should be placed in front of the door, and a much larger estimation error than 10% should be permitted for practical use in a standardization to estimate SFo) for low frequency. Moreover, a method of estimating not only SFo) but SFs as well when the noise source is close to MSR should be added in a standardization. © 1965-2012 IEEE.


Yamazaki K.,Takenaka Corporation | Yoneyama Y.,Giken kogyo Corporation | Sakai A.,Giken kogyo Corporation | Yuuki S.,Yokogawa Electric Corporation | And 4 more authors.
Transactions of Japanese Society for Medical and Biological Engineering | Year: 2014

To shield magnetic noises, magnetically shielded rooms (MSRs) are used for biomagnetic measurements, etc. To evaluate the shielding factor SF, the magnetic noise is applied by coils. However, SFs depend on the size and position of the coils, so standard of JEITA EM-4502 evaluating SF for extremely low frequency region of less than 1 Hz without eddy current effects, in which the shielding factor SFo for the uniform magnetic field can be estimated by using coils within 10 % error, has been already published. Then, a standardization for low frequency region of higher than 1 Hz, e.g. 50 Hz, taking account of eddy current effects, is discussed at present. In this paper, to establish standard methods for evaluating SF for low frequency region using coils, the effects of the eddy currents on SFs are investigated by measurement and analysis. © 2014, Japan Soc. of Med. Electronics and Biol. Engineering. All rights reserved.


Odawara S.,Saga University | Muramatsu K.,Saga University | Komori S.,Saga University | Kamata K.,KNCT | And 7 more authors.
IEEE Transactions on Magnetics | Year: 2010

To shield the environmental magnetic noises, magnetically shielded rooms (MSRs) are used for biomagnetic measurements, etc. The sources of environmental noises are placed far away from the MSR, in such way that almost uniform magnetic fluxes are applied to the MSR. Therefore, to specify the shielding performance of MSR, the shielding factor SFo for the uniform magnetic flux density should be evaluated. To evaluate SFo, in a construction site, the magnetic noise is applied by coils. However, SF's depend on the size and position of the coil. Therefore, to accomplish a standardization of the method for evaluating SFo, accurately, by coils, the method for estimating SFo's by smaller coil placed near MSR is being investigated in JEITA (Japan Electronics and Information Technology Industries Association). In JEITA, we have already proposed the method of estimating SFo's by the extrapolation using simple numerical expressions representing the relations between the SF and the size, position of coil. The proposed method was verified by the actual single-layered MSR using coils placed on double sides. In this paper, the method of estimating SFo of the double-layered MSR, using coils placed only on one side of MSR and taking account of door effect, is investigated using 3D nonlinear magnetic field analysis and measurements. By using the analysis, it is shown that the single coil should be set in front of the door. Moreover, SFo's estimated by using the measured data with the optimal coil setting can almost represent the tendencies of the true SFo. © 2006 IEEE.


Odawara S.,Saga University | Muramatsu K.,Saga University | Gao Y.,Saga University | Komori S.,Saga University | And 5 more authors.
IEEE Transactions on Magnetics | Year: 2011

To shield the environmental magnetic noises, magnetically shielded rooms (MSRs) are used for biomagnetic measurements, etc. The sources of environmental noises are far away from the MSR, in such a way that almost uniform magnetic field is applied to the MSR. To evaluate the shielding factor SFo for the uniform magnetic field in a construction site, the magnetic noises are applied by coils. However, SFs depend on the size and position of the coils, so a standardization of the method for accurately evaluating SFo using coils is being discussed in the Japan Electronics and Information Technology Industries Association (JEITA). In JEITA, we have already proposed and verified the method of estimating SFo's by smaller coils placed near MSRs in the low frequency region without eddy current effect. In this paper, the suitable size and position of coils, such that the errors of the SF o's estimated and directly evaluated are within 10%, on various shapes of MSRs are obtained using 3-D linear magnetostatic field analysis. Moreover, to correct SFs when the magnetic noises are applied to MSRs through a reinforced concrete wall, etc., the effect of wall on the applied magnetic field is also obtained from the experiment. Finally, the suitable coil conditions and the correction method are verified by the experiment using an actual double-layered MSR. © 2011 IEEE.

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