JPH0943328A - Superconductive magnetic detecting device - Google Patents
Superconductive magnetic detecting deviceInfo
- Publication number
- JPH0943328A JPH0943328A JP7193491A JP19349195A JPH0943328A JP H0943328 A JPH0943328 A JP H0943328A JP 7193491 A JP7193491 A JP 7193491A JP 19349195 A JP19349195 A JP 19349195A JP H0943328 A JPH0943328 A JP H0943328A
- Authority
- JP
- Japan
- Prior art keywords
- magnetic
- sensor
- magnetic field
- superconducting
- coil
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、超電導磁気検出装
置に関し、詳しくは弱結合特性を示す結晶粒界を有する
セラミック超電導磁気抵抗素子を用いて磁界に対する感
度を著しく向上させた超電導磁気検出装置に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting magnetic detecting device, and more particularly to a superconducting magnetic detecting device in which a ceramic superconducting magnetoresistive element having a grain boundary exhibiting weak coupling characteristics is used to remarkably improve the sensitivity to a magnetic field. .
【０００２】[0002]
【従来の技術】従来より、磁界を検出する素子として、
半導体のホール効果を応用したホール素子や半導体、磁
性体の磁気抵抗効果を応用した磁気抵抗素子が広く用い
られてきた。これらの素子は常温で使用されるものであ
り、１０-3〜１０-4ガウス程度の磁気感度が得られる
が、それ以上の感度を得ることは不可能であった。一
方、１０-10ガウスを示す高感度なものとして、超電導
体を使用した超電導量子干渉素子ＳＱＵＩＤがあるが、
その動作には極低温（４Ｋ）を必要とし、液体ヘリウム
を使用するため、装置が極めて高価であり、また、その
操作も複雑であった。その後、高い磁気検出感度を有
し、かつ、液体窒素温度（７７Ｋ）で簡便に使用できる
高温超電導体を用いたセラミック超電導磁気抵抗素子が
開発された。そして、このセラミック超電導磁気抵抗素
子を利用した高感度磁気検出装置は、交流磁界変調方式
を使用することにより１０-7ガウス程度の磁界分解能を
有していた。2. Description of the Related Art Conventionally, as an element for detecting a magnetic field,
Hall elements that apply the Hall effect of semiconductors, and magnetoresistive elements that apply the magnetoresistive effect of semiconductors and magnetic materials have been widely used. These elements are used at room temperature, and magnetic sensitivities of about 10 -3 to 10 -4 Gauss can be obtained, but it is impossible to obtain sensitivity higher than that. On the other hand, there is a superconducting quantum interference device SQUID using a superconductor as a highly sensitive one showing 10 -10 gauss.
The operation requires extremely low temperature (4K), and liquid helium is used, so that the apparatus is extremely expensive and its operation is complicated. After that, a ceramic superconducting magnetoresistive element using a high temperature superconductor having a high magnetic detection sensitivity and being easily usable at a liquid nitrogen temperature (77K) was developed. The high-sensitivity magnetic detection device using this ceramic superconducting magnetoresistive element has a magnetic field resolution of about 10 −7 Gauss by using the AC magnetic field modulation method.
【０００３】上記セラミック超電導磁気抵抗素子をセン
サとして使用した場合の外部磁場と出力電圧との相関関
係は、図５に示すような特性を有する。なお、この相関
関係はセンサに定電流Ｉ＝４．５mAを流した場合に測定
されたものである。図５において、任意の点をとって磁
電変換率を求めると、磁電変換率（Ｖ／Ｇ）＝１６×１
０-3（Ｖ）／７４．２×１０-3（Ｇ）＝０．２１６とな
る。The correlation between the external magnetic field and the output voltage when the above ceramic superconducting magnetoresistive element is used as a sensor has the characteristics shown in FIG. It should be noted that this correlation is measured when a constant current I = 4.5 mA is passed through the sensor. In FIG. 5, when the magnetoelectric conversion rate is obtained by taking an arbitrary point, the magnetoelectric conversion rate (V / G) = 16 × 1
0 −3 (V) /74.2×10 −3 (G) = 0.216.
【０００４】図６はセラミック超電導磁気抵抗素子を用
いた従来の磁気検出装置の動作原理を示す構成図であ
る。図６において、この磁気検出装置は、発振器４０と
抵抗４１と変調磁場発生用コイル４２とからなる変調磁
場発生装置と、セラミック超電導磁気抵抗素子からなる
センサ４４と、該センサ４４にＤＣ バイアス電流を印
加するための定電流源４３と、センサ４４の電圧端子か
ら得られる微弱磁気信号を増幅するための低雑音４nV／
√Hzの差動増幅器４５及び４６とを備えている。すなわ
ち、図６の磁気検出装置では、差動増幅器４５及び４６
を二段（１段目１０倍、２段目２０００倍）にして使用
している。FIG. 6 is a block diagram showing the operating principle of a conventional magnetic detection device using a ceramic superconducting magnetoresistive element. In FIG. 6, this magnetic detection device includes a modulating magnetic field generating device including an oscillator 40, a resistor 41, and a modulating magnetic field generating coil 42, a sensor 44 including a ceramic superconducting magnetoresistive element, and a DC bias current to the sensor 44. Low noise 4nV / for amplifying the weak magnetic signal obtained from the constant current source 43 for applying and the voltage terminal of the sensor 44
√Hz differential amplifiers 45 and 46 are provided. That is, in the magnetic detection device of FIG. 6, the differential amplifiers 45 and 46 are
Is used in two stages (first stage 10 times, second stage 2000 times).
【０００５】[0005]
【発明が解決しようとする課題】しかしながら、最近注
目を浴びている心磁場、肺磁場等の生体磁気計測や金属
材料の欠陥、腐食等の非破壊検査、地下資源探査等への
応用には、１０-9ガウスレベルの磁界分解能が必要であ
る。よって、上述した従来の増幅手段によれば、１段目
の差動増幅器４５前段でのセラミック超電導磁気抵抗素
子からなるセンサ４４の磁電変換率が０．２〜０．０５
Ｖ／Ｇ程度のため（図５参照）、１０-9ガウスレベルの
非常に微弱な磁気信号を差動増幅器４５及び４６で増幅
すると、この磁気信号が増幅器４５及び４６の入力電圧
雑音に埋もれてしまうという問題がある。However, the biomagnetic measurement of the magnetic field of the heart, lung magnetic field, etc., which has recently been attracting attention, nondestructive inspection of defects such as metal materials, corrosion, etc., and application to underground resource exploration, etc. A magnetic field resolution of 10 −9 Gauss level is required. Therefore, according to the conventional amplifying means described above, the magnetoelectric conversion rate of the sensor 44 including the ceramic superconducting magnetoresistive element in the preceding stage of the first stage differential amplifier 45 is 0.2 to 0.05.
Since it is approximately V / G (see FIG. 5), when a very weak magnetic signal of 10 −9 Gauss level is amplified by the differential amplifiers 45 and 46, this magnetic signal is buried in the input voltage noise of the amplifiers 45 and 46. There is a problem that it ends up.
【０００６】すなわち、１０-9ガウスレベルの磁気信号
を測定するためには、低雑音４nV／√Hzの差動増幅器の
前段で磁電変換率（Ｖ／Ｇ）＝４（nV／√Hz）／１（nG
／√Hz）＝４(Ｖ／Ｇ）程度は必要であり、１桁から２
桁程度磁電変換率が不足していた。さらに、上記のよう
に高利得で差動増幅器を使用しているため、２段で使用
する場合、増幅器の入力電圧雑音が利得により倍増し、
結果として出力から得られる磁気信号の雑音レベルが増
加してしまう、すなわち、Ｓ／Ｎが上がらないという問
題がある。That is, in order to measure a magnetic signal of 10 −9 Gauss level, the magnetoelectric conversion rate (V / G) = 4 (nV / √Hz) / in the preceding stage of the low noise 4 nV / √Hz differential amplifier. 1 (nG
/ √Hz) = 4 (V / G) is necessary, and from 1 digit to 2
The magnetoelectric conversion rate was insufficient by the order of magnitude. Furthermore, since the differential amplifier is used with high gain as described above, when used in two stages, the input voltage noise of the amplifier is doubled due to the gain,
As a result, there is a problem that the noise level of the magnetic signal obtained from the output increases, that is, the S / N does not increase.
【０００７】図７は、ＤＣ ＳＱＵＩＤを使用した従来
の磁気検出装置の動作原理を示す構成図である。図７に
示すように、この磁気検出装置は、発振器５０と変調磁
場発生用コイル５１とからなる変調磁場発生装置と、Ｄ
Ｃ ＳＱＵＩＤ５３と、このＤＣ ＳＱＵＩＤ５３にバ
イアス電流を印加するための定電流源５２と、コイル５
４とコンデンサ５５とで構成されたＬＣ直列共振回路
と、差動増幅器５６とを備えている。この磁気検出装置
は、コンデンサ５５の両端より磁気信号を検出し、差動
増幅器５６に入力するものである。しかし、この場合、
差動増幅器５６においてＤＣ増幅器の入力トランジスタ
をバイアスするのに必要な入力バイアス電流のため、外
部容量、すなわちコンデンサ５５の両端に静電気が蓄積
して充電が行われ、結果として、差動増幅器５６の出力
は飽和し、安定な動作を得ることが難しいという問題が
ある。FIG. 7 is a block diagram showing the operating principle of a conventional magnetic detection device using a DC SQUID. As shown in FIG. 7, this magnetic detection device includes a modulation magnetic field generation device including an oscillator 50 and a modulation magnetic field generation coil 51, and
C SQUID 53, constant current source 52 for applying a bias current to this DC SQUID 53, and coil 5
4 and a capacitor 55, and an LC series resonance circuit, and a differential amplifier 56. This magnetic detection device detects a magnetic signal from both ends of the capacitor 55 and inputs it to the differential amplifier 56. But in this case
Due to the input bias current required to bias the input transistor of the DC amplifier in the differential amplifier 56, static electricity is accumulated and charged in the external capacitance, that is, across the capacitor 55, and as a result, the differential amplifier 56 is charged. There is a problem that the output is saturated and it is difficult to obtain stable operation.
【０００８】また、本発明で使用するセラミック超電導
磁気抵抗素子は、磁気信号ゼロのとき数百Ωの抵抗を有
する。よって、定電流Ｉ＝数mAをセンサに流す場合、セ
ンサの出力電圧は、数百mV程度となる（図５参照）。従
って、コンデンサにセンサの出力電圧のほとんどがかか
るため、コンデンサから出力電圧を取ると、結果とし
て、その電圧を増幅器が数千倍に増幅し、出力が飽和し
てしまい、測定不可能になるという問題もある。The ceramic superconducting magnetoresistive element used in the present invention has a resistance of several hundred Ω when the magnetic signal is zero. Therefore, when the constant current I = several mA is passed through the sensor, the output voltage of the sensor is about several hundred mV (see FIG. 5). Therefore, most of the output voltage of the sensor is applied to the capacitor. Therefore, when the output voltage is taken from the capacitor, the amplifier amplifies the voltage several thousand times, and the output saturates, making it impossible to measure. There are also problems.
【０００９】そこで、本発明は、上記従来の課題に鑑み
てなされたものであり、セラミック超電導磁気抵抗素子
を用いて１０-9ガウス程度以上の磁気検出感度を示す超
電導磁気検出装置を提供することを目的とする。Therefore, the present invention has been made in view of the above-mentioned conventional problems, and provides a superconducting magnetism detecting device which uses a ceramic superconducting magnetoresistive element and exhibits a magnetic detection sensitivity of about 10 −9 Gauss or more. With the goal.
【００１０】[0010]
【課題を解決するための手段】請求項１の発明は、弱結
合特性を示す結晶粒界を有するセラミック超電導磁気抵
抗素子からなると共に磁界を検出するセンサと、変調磁
場を発生させると共に発生した変調磁場を前記センサに
印加する変調磁場発生手段と、前記センサからの磁気信
号のうち、共振周波数と等しい変調周波数の磁気信号を
選択するための磁気信号選択手段と、当該磁気信号選択
手段により選択された磁気信号を増幅するための増幅手
段とを備えたことを特徴とする超電導磁気検出装置であ
る。According to a first aspect of the present invention, there is provided a sensor which comprises a ceramic superconducting magnetoresistive element having crystal grain boundaries exhibiting a weak coupling characteristic and which detects a magnetic field, and a modulation magnetic field and a generated modulation. Modulated magnetic field generation means for applying a magnetic field to the sensor, magnetic signal selection means for selecting a magnetic signal having a modulation frequency equal to the resonance frequency among magnetic signals from the sensor, and selected by the magnetic signal selection means. And a amplifying means for amplifying the magnetic signal.
【００１１】請求項２の発明は、請求項１において、前
記磁気信号選択手段はＬＣ直列共振回路であり、かつ、
当該ＬＣ直列共振回路のコイルの両端の電圧を前記増幅
手段に入力することを特徴とする超電導磁気検出装置で
ある。According to a second aspect of the present invention, in the first aspect, the magnetic signal selection means is an LC series resonance circuit, and
The superconducting magnetism detecting device is characterized in that the voltage across the coil of the LC series resonance circuit is input to the amplifying means.
【００１２】請求項３の発明は、請求項１又は２におい
て、前記センサに印加する変調磁場の変調周波数を１kH
z以上とすることを特徴とする超電導磁気検出装置であ
る。According to a third aspect of the present invention, in the first or second aspect, the modulation frequency of the modulation magnetic field applied to the sensor is 1 kHz.
It is a superconducting magnetic detection device characterized by having z or more.
【００１３】[0013]
【発明の実施の形態】以下、本発明の実施の形態を図面
を参照して詳細に説明する。図１は、本発明の超電導磁
気検出装置の動作原理を示す構成図である。図１に示す
ように、本発明にかかる超電導磁気検出装置は、基本的
に、発振器１と抵抗２と変調磁場発生用コイル３とで構
成された変調磁場発生装置と、弱結合特性を示す結晶粒
界を有するセラミック超電導磁気抵抗素子からなると共
に磁界を検出するセンサ４と、このセンサ４の電流端子
に定電流（Ｉ＝４．５mA）を供給する定電流源５と、コ
ンデンサ６とコイル７とで構成されると共にセンサ４の
電圧端子に接続されたＬＣ直列共振回路と、センサ４か
らの磁気信号を増幅すると共にコイル７の電圧端子に接
続された差動増幅器（図示せず）とを備えている。BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram showing the operating principle of the superconducting magnetic detection device of the present invention. As shown in FIG. 1, the superconducting magnetic detection device according to the present invention is basically a modulation magnetic field generation device including an oscillator 1, a resistor 2 and a modulation magnetic field generation coil 3, and a crystal exhibiting a weak coupling characteristic. A sensor 4 composed of a ceramic superconducting magnetoresistive element having grain boundaries and for detecting a magnetic field, a constant current source 5 for supplying a constant current (I = 4.5 mA) to a current terminal of the sensor 4, a capacitor 6 and a coil 7. And an LC series resonance circuit connected to the voltage terminal of the sensor 4 and a differential amplifier (not shown) that amplifies the magnetic signal from the sensor 4 and is connected to the voltage terminal of the coil 7. I have it.
【００１４】上記変調磁場発生装置は、変調磁場を発生
させると共に発生した変調磁場（変調周波数＝共振周波
数＝１０kHz）及びＤＣ磁気信号をセンサ４に印加する
ものである。また、上記ＬＣ直列共振回路は、センサ４
からの磁気信号のうち、共振周波数と等しい変調周波数
の磁気信号を選択するものであり、このＬＣ直列共振回
路のコイル７の両端の電圧ＶLは差動増幅器に入力され
る。さらに、セラミック超電導磁気抵抗素子は、液体窒
素温度（７７Ｋ）に保持されている。なお、センサ４に
印加する変調磁場の変調周波数は１kHz以上であること
が望ましい。その理由としては、特に生体の心臓や脳か
ら発生する磁界は数１０Hzの周波数成分を有しており、
そのため変調周波数がその領域にかからないように考慮
する必要があるからである。上記の場合、センサ４の電
圧端子の出力からは１０kHzの交流信号が得られ、ＬＣ
直列共振回路に流れる。The above-mentioned modulating magnetic field generator generates a modulating magnetic field and applies the generated modulating magnetic field (modulation frequency = resonance frequency = 10 kHz) and a DC magnetic signal to the sensor 4. In addition, the LC series resonance circuit includes the sensor 4
The magnetic signal having a modulation frequency equal to the resonance frequency is selected from among the magnetic signals from (1), and the voltage V L across the coil 7 of the LC series resonance circuit is input to the differential amplifier. Further, the ceramic superconducting magnetoresistive element is maintained at the liquid nitrogen temperature (77K). The modulation frequency of the modulation magnetic field applied to the sensor 4 is preferably 1 kHz or higher. The reason is that the magnetic field generated from the heart and brain of a living body has a frequency component of several tens Hz,
Therefore, it is necessary to consider so that the modulation frequency does not cover the area. In the above case, an AC signal of 10 kHz is obtained from the output of the voltage terminal of the sensor 4, and LC
It flows into the series resonance circuit.
【００１５】図１において、センサ４の超電導状態時の
抵抗値をｒ、センサ４の出力電圧をＥ、コンデンサ６の
静電容量をＣ、コイル７のインダクタンスをＬとすれ
ば、回路のインピーダンスＺはＺ＝ｒ＋ｊ（ωＬ−１／
ωＣ）となり、インピーダンスの絶対値｜Ｚ｜は｜Ｚ｜
＝√（ｒ2−（ωＬ−１／ωＣ）2）となる。ここで、ｆ
（ω＝２πｆ）が共振周波数ｆ0となるとき、ωＬ＝１
／ωＣ、ω＝１／√（ＬＣ）が成り立ち、インピーダン
スの絶対値は｜Ｚ｜＝√（ｒ2）＝Ｒとなり最小値とな
る（図２参照）。よって、回路を流れる電流は、Ｉ’＝
Ｅ／ｒとなり最大となる。（図３参照）。すると、コイ
ル７の両端の電圧ＶLは、ＶL＝ωＬＥ／ｒ＝２πｆＬＥ
／ｒとなり、センサ４の出力電圧Ｅは２πｆＬ／ｒ倍で
得られることになる。特にｆが高く、Ｌが大きく、ｒが
小さければより大きな出力電圧が得られる。これにより
差動増幅器前段でのセンサ４の磁電変換率が向上し、磁
気検出感度が向上する。In FIG. 1, if the resistance value of the sensor 4 in the superconducting state is r, the output voltage of the sensor 4 is E, the capacitance of the capacitor 6 is C, and the inductance of the coil 7 is L, the impedance Z of the circuit is shown. Is Z = r + j (ωL-1 /
ωC), and the absolute value of impedance | Z | is | Z |
= √ (r 2 − (ωL−1 / ωC) 2 ). Where f
When (ω = 2πf) becomes the resonance frequency f 0 , ωL = 1
/ ΩC, ω = 1 / √ (LC) holds, and the absolute value of impedance is | Z | = √ (r 2 ) = R, which is the minimum value (see FIG. 2). Therefore, the current flowing through the circuit is I ′ =
It becomes E / r, which is the maximum. (See Figure 3). Then, the voltage V L across the coil 7 is V L = ωLE / r = 2πfLE
/ R, and the output voltage E of the sensor 4 is obtained by multiplying by 2πfL / r. In particular, if f is high, L is large, and r is small, a larger output voltage can be obtained. As a result, the magnetoelectric conversion rate of the sensor 4 in the preceding stage of the differential amplifier is improved, and the magnetic detection sensitivity is improved.
【００１６】図４は、本発明にかかる超電導磁気検出装
置の一実施形態を示す構成図である。図４に示すよう
に、セラミック超電導磁気抵抗素子１１はデュワー２８
内の液体窒素中に浸漬されて、７７Ｋに冷却保持されて
いる。なお、本実施形態で使用されたセラミック超電導
磁気抵抗素子１１の超電導体は、その粒界が極めて薄い
絶縁膜、又は、常電導体膜を介在して結合したものか、
あるいは、ポイント状に弱く結合したもので、磁界によ
り容易にその超電導状態が破れる構成にしてある。使用
した超電導体は、高温超電導体として知られているＹ1
Ｂａ2Ｃｕ3Ｏ7-X系である。これはミアンダ状にパター
ニングされており、電流、電圧端子が設けてある。FIG. 4 is a block diagram showing an embodiment of the superconducting magnetism detecting device according to the present invention. As shown in FIG. 4, the ceramic superconducting magnetoresistive element 11 is a dewar 28.
It is immersed in the liquid nitrogen inside and kept cooled at 77K. The superconductor of the ceramic superconducting magnetoresistive element 11 used in the present embodiment has an extremely thin grain boundary, is an insulating film, or is a normal conductor film and is connected to the superconductor.
Alternatively, the points are weakly coupled, and the superconducting state is easily broken by the magnetic field. The superconductor used is Y 1 which is known as high temperature superconductor.
A Ba 2 Cu 3 O 7-X system. This is patterned in a meandering shape, and current and voltage terminals are provided.
【００１７】セラミック超電導磁気抵抗素子１１の周囲
には、変調磁場発生用コイル１２、地磁気補正用コイル
１３、標準磁場信号発生用コイル１４がそれぞれ設けて
ある。この変調磁場発生用コイル１２には、発振器１５
と抵抗２６とが接続されており、発振器１５より１０kH
zの電流を変調磁場発生用コイル１２に供給することに
より変調磁場を発生させる。同様に、地磁気補正用コイ
ル１３には定電流源１７が接続され、標準磁場信号発生
用コイル１４には抵抗２７と発振器１６とが接続されて
おり、それぞれ地磁気補正用磁場、標準磁場が発生す
る。発生したこれらの磁場はセラミック超電導磁気抵抗
素子１１からなるセンサに印加される。また、定電流源
１８はシールドツイストペア線１９を介してセラミック
超電導磁気抵抗素子１１の電流端子へ直流電流Ｉ＝４．
５mAを印加する。A modulation magnetic field generating coil 12, a geomagnetic field correcting coil 13, and a standard magnetic field signal generating coil 14 are provided around the ceramic superconducting magnetoresistive element 11. The modulating magnetic field generating coil 12 includes an oscillator 15
And resistor 26 are connected, and 10kH from oscillator 15
A modulation magnetic field is generated by supplying a current of z to the modulation magnetic field generation coil 12. Similarly, a constant current source 17 is connected to the geomagnetic correction coil 13, and a resistor 27 and an oscillator 16 are connected to the standard magnetic field signal generation coil 14, which generate a geomagnetic correction magnetic field and a standard magnetic field, respectively. . These generated magnetic fields are applied to the sensor including the ceramic superconducting magnetoresistive element 11. Further, the constant current source 18 supplies a direct current I = 4. To the current terminal of the ceramic superconducting magnetoresistive element 11 via the shield twisted pair wire 19.
Apply 5mA.
【００１８】上述したように、センサに変調磁場発生用
コイル１２より発生した変調磁場を印加し、さらに測定
すべき磁気信号が加わると、セラミック超電導磁気抵抗
素子１１の電圧端子から変調された出力電圧が得られ
る。その得られた出力電圧は、シールドツイストペア線
２０を介してコンデンサ２１とコイル２２とで構成され
たＬＣ直列共振回路に入力される。ここで、変調周波数
（１０kHz）にＬＣ直列共振回路の共振周波数が一致す
るようにコイル２２のインダクタンスＬ＝４００mHとコ
ンデンサ２１の静電容量（Ｃ＝５００pF）＋（Ｃ｀＝１
００pF可変）とを組み合わせてあるので、コイル２２の
両端から得られる変調された磁気信号は最大限に増幅さ
れることになる。この場合、ＬＣ直列共振回路による増
幅度は、約１０倍となる。As described above, when the modulating magnetic field generated by the modulating magnetic field generating coil 12 is applied to the sensor and the magnetic signal to be measured is further applied, the output voltage modulated from the voltage terminal of the ceramic superconducting magnetoresistive element 11 is applied. Is obtained. The obtained output voltage is input to the LC series resonance circuit composed of the capacitor 21 and the coil 22 via the shielded twisted pair wire 20. Here, the inductance L of the coil 22 is 400 mH and the capacitance of the capacitor 21 is C (500 pF) + (C = 1) so that the resonance frequency of the LC series resonance circuit matches the modulation frequency (10 kHz).
(00 pF variable), the modulated magnetic signal obtained from both ends of the coil 22 is amplified to the maximum extent. In this case, the amplification factor of the LC series resonance circuit is about 10 times.
【００１９】そして、コイル２２の両端から得られる増
幅された磁気信号をさらに低雑音差動増幅器（×２５６
０）２３及びロックイン増幅器２４に入力する。ここで
ロックイン増幅器２４には、発振器１５からの参照信号
も入力されるので、変調周波数成分の信号を検出するこ
とになる。そして最終的に交流成分をカットするため、
低域フィルタ２５に入力する。以上の回路動作により測
定している磁場の強さを電圧として取り出す。また、特
に外部の電磁波の影響を除くために、ＬＣ直列共振回路
及び低雑音差動増幅器２３は、シャーシ２９に収納され
ている。Then, the amplified magnetic signals obtained from both ends of the coil 22 are further converted into a low noise differential amplifier (× 256).
0) 23 and lock-in amplifier 24. Since the reference signal from the oscillator 15 is also input to the lock-in amplifier 24 here, the signal of the modulation frequency component is detected. And in order to finally cut the AC component,
Input to the low pass filter 25. The strength of the magnetic field measured by the above circuit operation is extracted as a voltage. In addition, the LC series resonance circuit and the low noise differential amplifier 23 are housed in the chassis 29 in order to remove the influence of external electromagnetic waves.
【００２０】次に、上記の構成を有する回路の磁気検出
感度を測定した。Ａ点での磁気検出感度を測定するため
に、まずセンサに定電流４．５mAを流した。また、発振
器１６より、標準磁場発生用コイル（５．３Ｇ／Ａ）１
４に変調電流を供給し、変調磁場２０３．０７×１０-6
Ｇ（１０kHz）を発生させセンサに印加した。そして、
Ａ点の出力にＦＦＴアナライザーを接続することで、以
下に示す結果を得た。 Ａ点の出力電圧Vout=1.17(Vpp) 磁電変換率(V/G)=1.17/(203.07×10-6)=8420.74(V/G) １０Hzにおける雑音Ｎ=-95.4dBV=33.96×10-6(Vpp) 差動増幅器の前段での磁電変換率(V/G)=8420.74/2560=
3.29(V/G) 以上より、ＬＣ直列共振回路をセンサの電圧端子と差動
増幅器間に使用することで、差動増幅器の前段でのセン
サの磁電変換率が、従来の０．２〜０．０５（Ｖ／Ｇ）
程度から３．２９（Ｖ／Ｇ）に増大し、１桁から２桁向
上した。また、Ａ点での感度は、２．０２×１０-9（Ｇ
／√Hz）であった。Next, the magnetic detection sensitivity of the circuit having the above structure was measured. In order to measure the magnetic detection sensitivity at point A, a constant current of 4.5 mA was first applied to the sensor. In addition, from the oscillator 16, a standard magnetic field generating coil (5.3 G / A) 1
4 is supplied with the modulation current, and the modulation magnetic field is 203.07 × 10 -6
G (10 kHz) was generated and applied to the sensor. And
By connecting an FFT analyzer to the output at point A, the results shown below were obtained. Output voltage at A point Vout = 1.17 (Vpp) Magnetoelectric conversion rate (V / G) = 1.17 / (203.07 × 10 -6 ) = 8420.74 (V / G) Noise at 10Hz N = -95.4dB V = 33.96 × 10 -6 (Vpp) Magnetoelectric conversion rate (V / G) before the differential amplifier = 8420.74 / 2560 =
3.29 (V / G) From the above, by using the LC series resonance circuit between the voltage terminal of the sensor and the differential amplifier, the magnetoelectric conversion rate of the sensor in the preceding stage of the differential amplifier is 0.2 ~ 0. .05 (V / G)
It increased from about 3.29 (V / G) and improved by 1 to 2 digits. The sensitivity at point A is 2.02 × 10 -9 (G
/ √Hz).
【００２１】従って、本発明の超電導磁気検出装置は、
弱い磁界にも粒界の接合による作用で高い感度をもつこ
とができるセラミック超電導磁気抵抗素子を用いて、１
０-9ガウスレベルの磁界分解能を実現することができる
ものである。また、本発明の原理を用いることにより、
低周波での１０-9ガウスレベル磁界信号測定において、
信号増幅のための低雑音４nV／√Hzレベルを実現でき
る。Therefore, the superconducting magnetic detection device of the present invention is
Using a ceramic superconducting magnetoresistive element that has high sensitivity to weak magnetic fields due to the action of grain boundary bonding,
0 -9 it is capable to realize the magnetic field resolution of the Gauss level. Also, by using the principles of the present invention,
In the low frequency 10 -9 Gauss level magnetic field signal measurement,
Low noise 4nV / √Hz level for signal amplification can be realized.
【００２２】[0022]
【発明の効果】請求項１に記載の超電導磁気検出装置に
よれば、弱結合特性を示す結晶粒界を有するセラミック
超電導磁気抵抗素子からなる磁界検出センサと、変調磁
場を発生させてセンサに印加する変調磁場発生手段と、
センサからの磁気信号のうち、共振周波数と等しい変調
周波数の磁気信号を選択する磁気信号選択手段とを具備
することにより、超電導磁気抵抗素子の磁電変換率が従
来のものより高くなり、また低ノイズとなるため磁気検
出感度の向上を図ることができる。According to the superconducting magnetism detecting device of the present invention, a magnetic field detecting sensor composed of a ceramic superconducting magnetoresistive element having crystal grain boundaries exhibiting weak coupling characteristics and a modulating magnetic field are generated and applied to the sensor. Modulating magnetic field generating means for
By providing a magnetic signal selecting means for selecting a magnetic signal having a modulation frequency equal to the resonance frequency among the magnetic signals from the sensor, the magnetoelectric conversion rate of the superconducting magnetoresistive element becomes higher than that of the conventional one, and the noise is low. Therefore, the magnetic detection sensitivity can be improved.
【００２３】請求項２に記載の超電導磁気検出装置によ
れば、磁気信号選択手段をＬＣ直列共振回路とすること
により、磁気検出におけるノイズを除去することができ
る。さらに、ＬＣ直列共振回路のコイルの両端の電圧を
磁気信号を増幅するための増幅手段に入力することによ
り、安定、かつ、低ノイズで磁気信号を増幅でき、磁気
検出感度の向上を図ることができる。According to the superconducting magnetism detecting device of the second aspect, the magnetic signal selecting means is an LC series resonance circuit, so that noise in magnetism detection can be removed. Further, by inputting the voltage across the coil of the LC series resonance circuit to the amplifying means for amplifying the magnetic signal, the magnetic signal can be amplified stably and with low noise, and the magnetic detection sensitivity can be improved. it can.
【００２４】請求項３に記載の超電導磁気検出装置によ
れば、センサに印加する変調磁場の変調周波数を１kHz
以上とすることにより、変調周波数を生体の心臓や脳か
ら発生する磁界の数十Hz程度の周波数領域にかからない
ようにすることができ、磁気検出感度の向上を図ること
ができる。According to the superconducting magnetic detection device of the third aspect, the modulation frequency of the modulation magnetic field applied to the sensor is 1 kHz.
With the above, it is possible to prevent the modulation frequency from being applied to the frequency region of a few tens Hz of the magnetic field generated from the heart or brain of the living body, and it is possible to improve the magnetic detection sensitivity.
【図１】本発明の超電導磁気検出装置の動作原理を示す
構成図である。FIG. 1 is a configuration diagram showing an operation principle of a superconducting magnetic detection device of the present invention.
【図２】本発明の超電導磁気検出装置を動作させた場合
の周波数に対するＬＣ直列共振回路のインピーダンスの
絶対値｜Ｚ｜の変化を示す特性図である。FIG. 2 is a characteristic diagram showing changes in the absolute value | Z | of the impedance of the LC series resonance circuit with respect to the frequency when the superconducting magnetic detection device of the present invention is operated.
【図３】本発明の超電導磁気検出装置を動作させた場合
の周波数に対するＬＣ直列共振回路内を流れる電流及び
コイルの両端の電圧の変化を示す特性図である。FIG. 3 is a characteristic diagram showing changes in the current flowing in the LC series resonance circuit and the voltage across the coil with respect to frequency when the superconducting magnetic detection device of the present invention is operated.
【図４】本発明にかかる超電導磁気検出装置の一実施形
態を示す構成図である。FIG. 4 is a configuration diagram showing an embodiment of a superconducting magnetic detection device according to the present invention.
【図５】セラミック超電導磁気抵抗素子をセンサとして
使用した場合の外部磁場と出力電圧との相関関係を示す
図である。FIG. 5 is a diagram showing a correlation between an external magnetic field and an output voltage when a ceramic superconducting magnetoresistive element is used as a sensor.
【図６】セラミック超電導磁気抵抗素子を用いた従来の
磁気検出装置の動作原理を示す構成図である。FIG. 6 is a configuration diagram showing an operating principle of a conventional magnetic detection device using a ceramic superconducting magnetoresistive element.
【図７】ＤＣ ＳＱＵＩＤを用いた従来の磁気検出装置
の動作原理を示す構成図である。FIG. 7 is a configuration diagram showing an operation principle of a conventional magnetic detection device using a DC SQUID.
１ 発振器 ２ 抵抗 ３ 変調磁場発生用コイル ４ センサ ５ 定電流源 ６ コンデンサ ７ コイル 1 Oscillator 2 Resistance 3 Modulation magnetic field generating coil 4 Sensor 5 Constant current source 6 Capacitor 7 Coil
Claims (3)
ミック超電導磁気抵抗素子からなると共に磁界を検出す
るセンサと、変調磁場を発生させると共に発生した変調
磁場を前記センサに印加する変調磁場発生手段と、前記
センサからの磁気信号のうち、共振周波数と等しい変調
周波数の磁気信号を選択するための磁気信号選択手段
と、当該磁気信号選択手段により選択された磁気信号を
増幅するための増幅手段とを備えたことを特徴とする超
電導磁気検出装置。1. A sensor comprising a ceramic superconducting magnetoresistive element having crystal grain boundaries exhibiting weak coupling characteristics and detecting a magnetic field, and a modulating magnetic field generating means for generating a modulating magnetic field and applying the generated modulating magnetic field to the sensor. A magnetic signal selecting means for selecting a magnetic signal having a modulation frequency equal to the resonance frequency among the magnetic signals from the sensor; and an amplifying means for amplifying the magnetic signal selected by the magnetic signal selecting means. A superconducting magnetic detection device comprising:
路であり、かつ、当該ＬＣ直列共振回路のコイルの両端
の電圧を前記増幅手段に入力することを特徴とする請求
項１記載の超電導磁気検出装置。2. The superconducting magnet according to claim 1, wherein the magnetic signal selection means is an LC series resonance circuit, and the voltage across the coil of the LC series resonance circuit is input to the amplification means. Detection device.
波数を１kHz以上とすることを特徴とする請求項１又は
２記載の超電導磁気検出装置。3. The superconducting magnetic detector according to claim 1, wherein the modulation frequency of the modulation magnetic field applied to the sensor is 1 kHz or more.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7193491A JPH0943328A (en) | 1995-07-28 | 1995-07-28 | Superconductive magnetic detecting device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7193491A JPH0943328A (en) | 1995-07-28 | 1995-07-28 | Superconductive magnetic detecting device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0943328A true JPH0943328A (en) | 1997-02-14 |
Family
ID=16308931
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP7193491A Pending JPH0943328A (en) | 1995-07-28 | 1995-07-28 | Superconductive magnetic detecting device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0943328A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102183736A (en) * | 2011-02-28 | 2011-09-14 | 上海奥波信息科技有限公司 | Device and method for measuring low-intensity magnetic field |
| KR101487337B1 (en) * | 2014-08-13 | 2015-01-28 | 국방과학연구소 | Apparatus and Method for testing wideband alternating current magnetic sensor using series RLC resonance |
| JP2020008380A (en) * | 2018-07-05 | 2020-01-16 | 富士通株式会社 | Magnetic measurement module, magnetic property measurement device and magnetic property measurement method |
| WO2020113467A1 (en) * | 2018-12-05 | 2020-06-11 | 中国科学院地质与地球物理研究所 | Inductive magnetic sensor and electromagnetic exploration device |
-
1995
- 1995-07-28 JP JP7193491A patent/JPH0943328A/en active Pending
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102183736A (en) * | 2011-02-28 | 2011-09-14 | 上海奥波信息科技有限公司 | Device and method for measuring low-intensity magnetic field |
| KR101487337B1 (en) * | 2014-08-13 | 2015-01-28 | 국방과학연구소 | Apparatus and Method for testing wideband alternating current magnetic sensor using series RLC resonance |
| JP2020008380A (en) * | 2018-07-05 | 2020-01-16 | 富士通株式会社 | Magnetic measurement module, magnetic property measurement device and magnetic property measurement method |
| WO2020113467A1 (en) * | 2018-12-05 | 2020-06-11 | 中国科学院地质与地球物理研究所 | Inductive magnetic sensor and electromagnetic exploration device |
| US11914092B2 (en) | 2018-12-05 | 2024-02-27 | Institute Of Geology And Geophysics, The Chinese Academy Of Sciences | Inductive magnetic sensor and electromagnetic prospecting equipment |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US6815949B2 (en) | Apparatus for measuring a magnetic field | |
| US4324255A (en) | Method and apparatus for measuring magnetic fields and electrical currents in biological and other systems | |
| US5343147A (en) | Method and apparatus for using stochastic excitation and a superconducting quantum interference device (SAUID) to perform wideband frequency response measurements | |
| Cromar et al. | Low‐noise tunnel junction dc SQUID’s | |
| JP5978310B2 (en) | DCSQUID-based RF magnetometer that operates over 200MHz bandwidth | |
| Goodman et al. | Superconducting instrument systems | |
| US7394246B2 (en) | Superconductive quantum interference device (SQUID) system for measuring magnetic susceptibility of materials | |
| Ripka et al. | Fluxgate: Tuned vs. untuned output | |
| Templeton | A superconducting modulator | |
| Boukhenoufa et al. | High-sensitivity giant magneto-inductive magnetometer characterization implemented with a low-frequency magnetic noise-reduction technique | |
| US4315215A (en) | Plural frequency type superconducting quantum interference fluxmeter | |
| TonThat et al. | Direct current superconducting quantum interference device spectrometer for pulsed nuclear magnetic resonance and nuclear quadrupole resonance at frequencies up to 5 MHz | |
| JPH0943328A (en) | Superconductive magnetic detecting device | |
| Senaj et al. | Inductive measurement of magnetic field gradients for magnetic resonance imaging | |
| Ripka et al. | Tuned current-output fluxgate | |
| JP2005188947A (en) | Magnetic detector | |
| Liao et al. | Longitudinal relaxation time detection using a high-Tc superconductive quantum interference device magnetometer | |
| Stolz et al. | Long baseline thin film SQUID gradiometers | |
| Sokol-Kutylovskii | A magneto-modulating meter of a weak variable magnetic field | |
| Zakosarenko et al. | Integrated LTS gradiometer SQUID systems for unshielded measurements in a disturbed environment | |
| He | Developing gradiometer to reduce the low frequency noise of magnetic sensor with amorphous wire | |
| Cruz et al. | Design of a fourth harmonic fluxgate magnetometer | |
| Qian et al. | Integrated driving and readout circuits for orthogonal fluxgate sensor | |
| JP3133803B2 (en) | Method for measuring magnetic field inside superconductor structure, method for measuring magnetic shield characteristics of superconductor, and apparatus for measuring magnetic field inside superconductor structure | |
| Robbes et al. | Performances and place of magnetometers based on amorphous wires compared to conventional magnetometers |