講演抄録/キーワード |
講演名 |
2009-10-22 10:10
[特別講演]生体磁気計測とEMI ~ 冷凍機駆動雑音と環境磁気雑音の低減を中心にして ~ ○笹田一郎(九大) エレソ技報アーカイブへのリンク:MW2009-93 |
抄録 |
(和) |
脳や心臓等から発せられるpTレベルの微弱な生体磁気計測において低周波環境磁界は信号のスペクトル領域と重なっており,桁違いに大きな雑音となる.本報告では筆者らが開発している能動補償の原理に基づく新しいタイプの磁気シールドについて,その構造と動作,基本性能について述べる.また,生体磁気計測に必須のSQUIDセンサを冷凍機によって4 Kまで冷却することができるが,インバータ駆動部を持つ冷凍機から超高感度であるSQUIDへのEMIが常に問題になる.インバータのスイッチングに起因して引き起こされる高周波雑音電流を電流パスの数カ所で同時観測し,原因を特定し対策を施した.これによって高周波雑音電流を1/5に低減することに成功した. |
(英) |
Abstract Magnetic fields from a human heart and a human brain are very small. They are on the order of several tens of pT for the former and sub-pT for the latter. They are time-varying signals having main frequency spectra less than 30 Hz in which range there are relatively strong low-frequency environment magnetic noises as interferences. Magnetic shielding rooms are widely used for their measurements. However, not only they are heavy and expensive, but also there is a hight barrier at the door way of such rooms. In this report, active magnetic shielding methods are presented in which unlike a conventional active magnetic shielding highly permeable shells are combined with it in order to obtain a wide shielded volume with high shielding efficiency and holding an easy access way to the shielded space. Another topic in this report is conducted EMI problem encountered in operating a SQUID sensor used to measure biomagnetic fields with a cryocooler for cooling. The cold head of a cryocooler where a SQUID is located is linked to an inverter-driven valve motor with conducting horses, and the valve motor is further linked to an electrically noisy compressor housing with conducting horse and with a power line. We have analyzed conducting passes of noise currents by observing their waveforms simultaneously at several points using current transformers we made. Through the simultaneous observation of noises, we could easily locate the cause of conducted EMI and succeed to operate a SQUID after reduction of the influence of the EMI. |
キーワード |
(和) |
能動磁気シールド / 生体磁気計測 / SQUID / 冷凍機 / 伝導性EMI / カレントトランス / / |
(英) |
Active magnetic shielding / Biomagnetic fields / SQUID / Cryocooler / conducted EMI / Current transformer / / |
文献情報 |
信学技報, vol. 109, pp. 1-6, 2009年10月. |
資料番号 |
|
発行日 |
2009-10-15 (EMCJ, MW) |
ISSN |
Print edition: ISSN 0913-5685 Online edition: ISSN 2432-6380 |
著作権に ついて |
技術研究報告に掲載された論文の著作権は電子情報通信学会に帰属します.(許諾番号:10GA0019/12GB0052/13GB0056/17GB0034/18GB0034) |
PDFダウンロード |
エレソ技報アーカイブへのリンク:MW2009-93 |