JPH0320890B2 - - Google Patents
Info
- Publication number
- JPH0320890B2 JPH0320890B2 JP61271051A JP27105186A JPH0320890B2 JP H0320890 B2 JPH0320890 B2 JP H0320890B2 JP 61271051 A JP61271051 A JP 61271051A JP 27105186 A JP27105186 A JP 27105186A JP H0320890 B2 JPH0320890 B2 JP H0320890B2
- Authority
- JP
- Japan
- Prior art keywords
- magnetic field
- reference signal
- magnet
- strength
- normal
- 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.)
- Expired - Lifetime
Links
- 238000001514 detection method Methods 0.000 claims description 11
- 230000003068 static effect Effects 0.000 claims description 7
- BGPVFRJUHWVFKM-UHFFFAOYSA-N N1=C2C=CC=CC2=[N+]([O-])C1(CC1)CCC21N=C1C=CC=CC1=[N+]2[O-] Chemical compound N1=C2C=CC=CC2=[N+]([O-])C1(CC1)CCC21N=C1C=CC=CC1=[N+]2[O-] BGPVFRJUHWVFKM-UHFFFAOYSA-N 0.000 description 16
- 238000010586 diagram Methods 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 238000001816 cooling Methods 0.000 description 3
- 239000000498 cooling water Substances 0.000 description 2
- 238000003384 imaging method Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 1
- 230000006870 function Effects 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000000034 method Methods 0.000 description 1
Landscapes
- Magnetic Resonance Imaging Apparatus (AREA)
Description
【発明の詳細な説明】
（産業上の利用分野）
本発明は、常伝導マグネツトを用いたMRイメ
ージング装置における静磁場電源装置に関し、詳
しくは電流制御特性の改善に関する。DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a static magnetic field power supply device in an MR imaging apparatus using a normal conduction magnet, and specifically relates to improvement of current control characteristics.
（従来の技術）
第３図は、従来の常伝導マグネツトを用いた
MRイメージング装置における静磁場電源装置の
一例を示す構成図である。図において、１は直流
電源である。該直流電源１の陽極端子はトランジ
スタ２のコレクタに接続され、トランジスタ２の
エミツタはシヤント抵抗器３を介して常伝導マグ
ネツト４の一端に接続されている。常伝導マグネ
ツト４の他端は直流電源１の陰極端子に接続され
ている。トランジスタ２のベースにはアンプ５の
出力端子が接続されている。該アンプ５の非反転
入力端子には基準電圧源６が接続され、反転入力
端子にはアンプ７を介してシヤント抵抗器３によ
る電流検出信号及びセンタ８による常伝導マグネ
ツト４の磁界の強さの検出信号が加えられてい
る。９は常伝導マグネツト４を冷却するための水
流である。(Conventional technology) Figure 3 shows a method using a conventional normal conduction magnet.
FIG. 2 is a configuration diagram showing an example of a static magnetic field power supply device in an MR imaging apparatus. In the figure, 1 is a DC power supply. The anode terminal of the DC power supply 1 is connected to the collector of a transistor 2, and the emitter of the transistor 2 is connected to one end of a normal conducting magnet 4 via a shunt resistor 3. The other end of the normal conducting magnet 4 is connected to the cathode terminal of the DC power supply 1. The base of the transistor 2 is connected to the output terminal of the amplifier 5. A reference voltage source 6 is connected to a non-inverting input terminal of the amplifier 5, and a current detection signal from a shunt resistor 3 and a current detection signal from a center 8 indicating the strength of the magnetic field of the normal conducting magnet 4 are connected to the inverting input terminal via an amplifier 7. A detection signal is added. 9 is a water flow for cooling the normal conducting magnet 4.
このような構成において、常伝導マグネツト４
に発生する磁界の強さＢは、常伝導マグネツト４
に流れる電流により制御される。 In such a configuration, the normal conducting magnet 4
The strength B of the magnetic field generated in the normal conducting magnet 4
controlled by the current flowing through the
ところが、常伝導マグネツト４に反省する磁界
の強さＢは、常伝導マグネツト４の温度Ｔによつ
て常伝導マグネツト４の開口面積が変化すること
によつても変化する。 However, the strength B of the magnetic field reflected on the normal conducting magnet 4 also changes as the opening area of the normal conducting magnet 4 changes depending on the temperature T of the normal conducting magnet 4.
そこで、磁界の強さＢの制御にあたつては常伝
導マグネツト４に一定電流Ｉを流しながら、一定
の水温、推量の水流９で常伝導マグネツト４を強
制的に冷却して常伝導マグネツト４で発生する熱
量I2RLと熱平衡状態を保つと共に、センサ８で
NMR信号そのものを検出することによつて磁界
の強さＢを検出し、目標とする磁界の強しB0に
対して偏差があれば電流Ｉにフイードバツクして
一定の磁場を発生することが行われている。 Therefore, when controlling the strength B of the magnetic field, the normal conducting magnet 4 is forcibly cooled down with a constant water temperature and an estimated water flow 9 while a constant current I is flowing through the normal conducting magnet 4. In addition to maintaining thermal equilibrium with the amount of heat generated by I 2 R L , sensor 8
The magnetic field strength B is detected by detecting the NMR signal itself, and if there is a deviation from the target magnetic field strength B0 , it is fed back to the current I to generate a constant magnetic field. ing.
（発明が解決しようとする問題点）
しかし、このような制御系における磁界の強さ
Ｂの制御範囲はB0±50ppm程度であるのに対し
て電流検出に用いられるシヤント抵抗器３の抵抗
値r0の経時変化は300ppm／2000H程度であり、
このような抵抗に基づく電流検出信号は数日〜数
ヵ月で制御範囲を外れてしまつて長時間にわたつ
て安定な磁場を得ることは困難である。(Problem to be solved by the invention) However, the control range of the magnetic field strength B in such a control system is about B 0 ±50 ppm, whereas the resistance value of the shunt resistor 3 used for current detection is The change in r 0 over time is about 300ppm/2000H,
A current detection signal based on such resistance goes out of the control range after several days to several months, making it difficult to obtain a stable magnetic field over a long period of time.
本発明は上記の問題点に鑑みてなされたもので
あり、その目的は、長時間にわたつて安定した磁
場が得られる静磁場電流装置を実現することにあ
る。 The present invention has been made in view of the above problems, and its purpose is to realize a static magnetic field current device that can obtain a stable magnetic field over a long period of time.
（問題点を解決するための手段）
前記した問題点を解決する本発明は、常伝導マ
グネツトに流れる電流を検出するシヤント抵抗器
と、常伝導マグネツトが発生する磁界の強さを検
出するセンタと、基準信号源とを具備し、これら
シヤント抵抗器の検出信号とセンサの検出信号と
基準信号源の基準信号に基づいて常伝導マグネツ
トに流れる電流を制御する静磁場電流装置におい
て、
センサの検出信号に基づいて基準信号源の基準
信号を変更する基準信号変更回路を設けたことを
特徴とするものでもある。(Means for Solving the Problems) The present invention, which solves the above-mentioned problems, includes a shunt resistor for detecting the current flowing through the normal conduction magnet, and a center for detecting the strength of the magnetic field generated by the normal conduction magnet. , a reference signal source, and controls a current flowing through a normal magnet based on the detection signal of the shunt resistor, the detection signal of the sensor, and the reference signal of the reference signal source, comprising: a detection signal of the sensor; The present invention is also characterized in that it includes a reference signal changing circuit that changes the reference signal of the reference signal source based on the reference signal source.
（作用）
本発明の静磁場電源装置によれば、シヤント抵
抗器の抵抗値の変化に応じてセンサの基準信号の
大きさが自動的に調整されることになり、長時間
にわたつて安定した磁場を得ることができる。(Function) According to the static magnetic field power supply device of the present invention, the magnitude of the reference signal of the sensor is automatically adjusted according to the change in the resistance value of the shunt resistor, so that it is stable for a long time. You can get a magnetic field.
（実施例）
以下、図面を参照して本発明の実施例を詳細に
説明する。(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.
第１図は本発明の一実施例を示す構成図であ
り、第３図と同一のものは同一符号を付けて示
す。図において、１０は常伝導マグネツト４の磁
界の強さを検出するセンサであり、制御の基準信
号を発生するマイクロプロセツサ１１に対して基
準信号の値を増減制御する制御信号Ｉ／Ｄを送出
すると共に磁界の強さが目標値に一致した時点で
ロツク信号LKDを送出する。マイクロプロセツ
サ１１には電源がオフの場合でもデータが発揮し
ない不揮発メモリ１２が設けられていて、該メモ
リ１２にはセンサ１０からロツク信号LKDが送
出された時点における基準信号データが格納され
る。１３はマイクロプロセツサ１１から基準信号
として出力されるデイジタルデータをアナログ信
号に変換するＤ／Ａ変換器であり、その出力端子
はアンプ５の非反転入力端子に接続されている。
このように構成された装置の動作について説明す
る。 FIG. 1 is a block diagram showing an embodiment of the present invention, and the same parts as in FIG. 3 are designated by the same reference numerals. In the figure, 10 is a sensor that detects the strength of the magnetic field of the normal conducting magnet 4, and sends a control signal I/D to control the increase or decrease of the value of the reference signal to the microprocessor 11 that generates the control reference signal. At the same time, when the strength of the magnetic field matches the target value, a lock signal LKD is sent out. The microprocessor 11 is provided with a non-volatile memory 12 which does not store data even when the power is off, and the reference signal data at the time when the lock signal LKD is sent from the sensor 10 is stored in the memory 12. A D/A converter 13 converts digital data output as a reference signal from the microprocessor 11 into an analog signal, and its output terminal is connected to the non-inverting input terminal of the amplifier 5.
The operation of the device configured in this way will be explained.
センサ１０は常伝導マグネツト４が発生する磁
界の強さＢが目標値B0に対して所定の範囲（例
えは±50ppm）の値に達したことを検出すると、
マイクロプロセツサ１１に対して基準信号の値を
増減制御するための制御信号Ｉ／Ｄを送出する。
磁界の強さを目標値に対して所定の範囲まで到達
させる作業は、図示しない自動シーケンス装置或
いは、オペレータによる手動操作によつて行われ
る。マイクロプロセツサ１１は、該制御信号Ｉ／
Ｄに従つて基準信号を変化させる。これにより、
常伝導マグネツト４に流れる電流Ｉの値が変化
し、磁界の強さＢも変化する。このようにして常
伝導マグネツト４が発生する磁界の強さＢが変化
して目標値B0との偏差が充分に小さくなると、
センサ１０はロツク信号LKDをマイクロプロセ
ツサ１１に送出する。そして、マイクロプロセツ
サ１１は、このロツク信号LKDに従つてその時
点における基準信号の値をメモリ１２に更新格納
する。これにより、メモリ１２は、最新の基準信
号の値が格納されることになる。このメモリ１２
に格納された基準信号の値は、次回のシステムの
再起動時にマイクロプロセツサ１１により読み出
され、制御の基準信号としてＤ／Ａ変換器１３を
通じてアンプ５に入力される。 When the sensor 10 detects that the strength B of the magnetic field generated by the normal conduction magnet 4 has reached a value within a predetermined range (for example, ±50 ppm) with respect to the target value B0 ,
A control signal I/D is sent to the microprocessor 11 to increase or decrease the value of the reference signal.
The work of bringing the strength of the magnetic field to a predetermined range with respect to the target value is performed by an automatic sequence device (not shown) or by manual operation by an operator. The microprocessor 11 receives the control signal I/
The reference signal is changed according to D. This results in
The value of the current I flowing through the normal conducting magnet 4 changes, and the strength B of the magnetic field also changes. In this way, when the strength B of the magnetic field generated by the normal conducting magnet 4 changes and the deviation from the target value B0 becomes sufficiently small,
Sensor 10 sends a lock signal LKD to microprocessor 11. Then, the microprocessor 11 updates and stores the value of the reference signal at that time in the memory 12 in accordance with this lock signal LKD. As a result, the memory 12 stores the latest reference signal value. This memory 12
The value of the reference signal stored in is read out by the microprocessor 11 the next time the system is restarted, and is input to the amplifier 5 through the D/A converter 13 as a control reference signal.
このように構成することにより、シヤント抵抗
器３の抵抗値r0が例えば第２図ａに示すように経
時的に変化しても、システムの起動時における制
御の基準信号も第２図ｂに示すようにシヤント抵
抗器３の抵抗値の変化に追従して変化することに
なる。従つて、シヤント抵抗器３の抵抗値r0が例
えば数ヵ月で100ppm変化してもシステムが停止
して再起動するまでの間（例えば半日乃至１日）
に磁界の制御が可能な範囲（例えば±50ppm）を
越えない限り、常に安定した磁界の強さＢ（＝
B0）を得ることができる。 With this configuration, even if the resistance value r 0 of the shunt resistor 3 changes over time as shown in FIG. 2a, for example, the reference signal for control at the time of system startup also remains as shown in FIG. 2b. As shown, it changes following the change in the resistance value of the shunt resistor 3. Therefore, even if the resistance value r 0 of the shunt resistor 3 changes, for example, by 100 ppm over a period of several months, the system will not change until the system is stopped and restarted (for example, half a day to one day).
The magnetic field strength B (=
B 0 ) can be obtained.
又、このように構成することにより、常伝導マ
グネツト４を冷却する冷却器の冷却能力の経時変
化に対しても有効である。即ち、夏と冬とで冷却
水の温度が変化するとか、冷却水量が経時的に変
化することがあつても、それに影響されることな
く磁界の強さは目標の値に維持される。 Furthermore, this configuration is effective against changes over time in the cooling capacity of the cooler that cools the normal conduction magnet 4. That is, even if the temperature of the cooling water changes between summer and winter, or the amount of cooling water changes over time, the strength of the magnetic field is maintained at the target value without being affected by this.
（発明の効果）
以上説明したように、本発明によれば、長時間
にわたつて無調整で安定した磁界が得られる静磁
場電源装置が実現でき、シヤント抵抗器や冷却系
統の長期安定性に求められる性能条件を緩和でき
ることからコストダウンも図れる。(Effects of the Invention) As explained above, according to the present invention, a static magnetic field power supply device that can obtain a stable magnetic field over a long period of time without adjustment can be realized, which improves the long-term stability of shunt resistors and cooling systems. Since the required performance conditions can be relaxed, costs can also be reduced.
第１図は本発明の一実施例を示す構成図、第２
図は第１図の動作説明図、第３図は従来の装置の
一例を示す構成図である。
１……直流電源、２……トランジスタ、３……
シヤント抵抗器、４……常伝導マグネツト、５，
７，１５……アンプ、９……水流、１０……セン
サ、１１……マイクロプセツサ、１２……メモ
リ、１３……Ｄ／Ａ変換器。
FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
The figure is an explanatory diagram of the operation of FIG. 1, and FIG. 3 is a configuration diagram showing an example of a conventional device. 1...DC power supply, 2...Transistor, 3...
shunt resistor, 4...normal conduction magnet, 5,
7, 15...Amplifier, 9...Water flow, 10...Sensor, 11...Microprocessor, 12...Memory, 13...D/A converter.
Claims (1)
ヤント抵抗器と、常伝導マグネツトが発生する磁
界の強さを検出するセンサと、基準信号源とを具
備し、これらシヤント抵抗器の検出信号とセンサ
の検出信号と基準信号源の基準信号に基づいて常
伝導マグネツトに流れる電流を制御する静磁場電
源装置において、 センサの検出信号に基づいて基準信号源の基準
信号を変更する基準信号変更回路を設けたことを
特徴とする静磁場電源装置。[Claims] 1. A shunt resistor that detects the current flowing through the normal conduction magnet, a sensor that detects the strength of the magnetic field generated by the normal conduction magnet, and a reference signal source. In a static magnetic field power supply device that controls the current flowing through a normal magnet based on a detection signal, a sensor detection signal, and a reference signal from a reference signal source, a reference signal that changes the reference signal from the reference signal source based on the sensor detection signal. A static magnetic field power supply device characterized by being provided with a changing circuit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61271051A JPS63124505A (en) | 1986-11-14 | 1986-11-14 | Magnetostatic field power source device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61271051A JPS63124505A (en) | 1986-11-14 | 1986-11-14 | Magnetostatic field power source device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS63124505A JPS63124505A (en) | 1988-05-28 |
| JPH0320890B2 true JPH0320890B2 (en) | 1991-03-20 |
Family
ID=17494718
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP61271051A Granted JPS63124505A (en) | 1986-11-14 | 1986-11-14 | Magnetostatic field power source device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS63124505A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7248731B2 (en) | 1992-05-19 | 2007-07-24 | Cummins-Allison Corp. | Method and apparatus for currency discrimination |
-
1986
- 1986-11-14 JP JP61271051A patent/JPS63124505A/en active Granted
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7590274B2 (en) | 1990-02-05 | 2009-09-15 | Cummins-Allison Corp. | Method and apparatus for currency discrimination |
| US7248731B2 (en) | 1992-05-19 | 2007-07-24 | Cummins-Allison Corp. | Method and apparatus for currency discrimination |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS63124505A (en) | 1988-05-28 |
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