WO1997031273A2 - Magnetic field measuring arrangement - Google Patents
Magnetic field measuring arrangement Download PDFInfo
- Publication number
- WO1997031273A2 WO1997031273A2 PCT/DE1997/000315 DE9700315W WO9731273A2 WO 1997031273 A2 WO1997031273 A2 WO 1997031273A2 DE 9700315 W DE9700315 W DE 9700315W WO 9731273 A2 WO9731273 A2 WO 9731273A2
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- signal
- analog
- controller
- compensation
- digital
- Prior art date
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
- G01R33/035—Measuring direction or magnitude of magnetic fields or magnetic flux using superconductive devices
- G01R33/0354—SQUIDS
- G01R33/0356—SQUIDS with flux feedback
Definitions
- the invention relates to a measuring device for measuring magnetic fields with the aid of one or more highly sensitive SQUID magnetic field sensors (Superconducting Quantum Interference Devices).
- SQUID magnetic field sensors Superconducting Quantum Interference Devices
- Such sensors show a periodic characteristic of the voltage U as a function of the magnetic flux ⁇ with a
- Period length of a flux quantum ⁇ 0 2 ' ICT 1 Tm 2 [cf. e.g. R.Boll, KJOvershott Magnetic Sensors, 1989, VCH Verlagsgesellschaft mbH, ISB N 3-527-26771-9, pages 387-389]. Due to the periodic characteristic curve, the voltage can only change within% ⁇ 0
- the measurement signal 1 is converted into a voltage 4 by means of the SQUID sensor 3.
- the controller 5 calculates the compensation signal 6 from this signal.
- the compensation voltage is converted into a magnetic flux 8 via a linear voltage-flux converter 7 and fed back in such a way that the controller input signal 4 assumes a value of 0 volts.
- the compensation signal 6 is also the output signal of the circuit.
- analog compensation control The use of an analog compensation control is known.
- analog control existing from analog components such as operational amplifiers lies in the large measuring bandwidth and the high slew rate. Since it is a continuous-time control, the response time to changes in the input signal is short.
- the very limited measuring range of such an analog control proves to be disadvantageous.
- the measuring range is determined by the maximum voltage swing of the output amplifier and the intrinsic noise of the circuit.
- a digital compensation control with a flux quantum counter is also known.
- the advantage of such a digital control consisting of an analog-digital converter (ADC), a digital-analog converter (DAU) and an arithmetic unit, lies in the almost unlimited
- the periodic characteristic of the SQUID signal is used for the digitization of the analog signals.
- a reset unit performs defined jumps in compensation by an even number of flux quanta that are counted.
- the compensation unit keeps the compensation signal in a defined value range.
- the measurement signal is finally formed from the sum of the flux quantum jump number and the compensation signal.
- the digital control provides an almost unlimited measuring range. Because of the digital, time-discrete processing of the signals with AD-DA converters and the calculation If the compensation signal is used in accordance with a predefined algorithm, the measurement bandwidth and slew rate are lower than with analog circuits.
- the measuring device should be designed as a hybrid controller to solve the task, ie by combining an analog P controller (proportional controller) with a digital I controller (integral controller). In this way, the positive properties of these two control loops are combined with one another in the measuring device according to the invention.
- FIG. 1 Measuring device according to the invention
- FIG. 2 shows a measuring device according to the invention for measuring magnetic fields in a circuit diagram.
- a measurement signal 1 is converted by a SQUID 3 into a voltage signal 4 for an analog P-controller 5.
- the compensation signal 6 calculated by the P controller 5 forms the input signal of the digital I controller 9, 11, 13.
- This signal 6 is digitized by an AD converter 9 and fed to an arithmetic unit 11.
- This arithmetic unit 11 calculates the compensation signal 12 of the I controller.
- the digital signal 12 is converted into an analog signal 14 via a DA converter 13.
- An analog summing element 15 forms the total compensation signal 16 from the compensation signal 6 of the analog P-controller 5 and the compensation signal 12 of the digital I-controller 14 7/31273 PC 17DE97 / 00315
- linear voltage-flux converter 7 converted into a compensation flow 8.
- a reset unit and a flux quantum counter as well as the calculation of the output signal 17 are carried out by the arithmetic logic unit 11 with the aid of software, for example using a DSP.
- Such a measuring device shows the following properties:
- the control signal compensates the measurement signal so that the input signal of the closed control loop does not exceed a value range of ⁇ ⁇ ⁇ 0 . In this way it is avoided that the regulation can no longer follow the input signal.
- the P component of the control is responsible for the fast compensation, the limitation of the SQUID signal (2) to ⁇ M ⁇ 0 , and thus for the high slew rate and the large measurement bandwidth.
- the P controller is therefore analog.
- the disadvantage of the P controller is the remaining control deviation, which leads to the permissible value range of the SQUID signal (2) being exceeded by ⁇ M ⁇ 0 in the case of large input signals.
- an I controller is provided in addition to the P controller. He responds more slowly; However, it was recognized that the I-controller, however, for static signals, fully inputs the input signal of the I-controller (6) and thus the input signal of the P-controller (4). constantly compensated. This ensures that the SQUID remains in the specified operating point.
- the I controller is now implemented digitally with an additional flux quantum counter, then the measuring range limitation due to the maximum amplitude of the output amplifier does not apply to the measuring device, and it has an almost unlimited measuring range for measuring signals with a low frequency.
- the analog compensation signal 6 does not change its value during the flux quantum jump of the digital compensation signal 12.
- a hardware component such as a clamping device, can be provided in the circuit, which effects this.
- the measuring range limitation is specified by the analog P controller.
- the analog P-controller brings about the high slew rate and the large measurement bandwidth, while at the same time the digital I-controller uses lower-level ones
- FIGS. 3 to 5 For the purpose of explanation, the function for a flux quantum jump width of one flux quantum W is shown in FIGS. 3 to 5:
Abstract
Description
Claims
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP97917233A EP0882241A2 (en) | 1996-02-23 | 1997-02-21 | Magnetic field measuring arrangement |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE19606655.7 | 1996-02-23 | ||
DE1996106655 DE19606655C2 (en) | 1996-02-23 | 1996-02-23 | Measuring device for measuring magnetic fields |
Publications (2)
Publication Number | Publication Date |
---|---|
WO1997031273A2 true WO1997031273A2 (en) | 1997-08-28 |
WO1997031273A3 WO1997031273A3 (en) | 1997-10-02 |
Family
ID=7786136
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/DE1997/000315 WO1997031273A2 (en) | 1996-02-23 | 1997-02-21 | Magnetic field measuring arrangement |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0882241A2 (en) |
DE (1) | DE19606655C2 (en) |
WO (1) | WO1997031273A2 (en) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE10139883C1 (en) * | 2001-08-20 | 2003-06-05 | Stl Systemtechnik Ludwig Gmbh | Device for setting an operating point of a magnetic field sensor and a method therefor |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4672359A (en) * | 1985-11-12 | 1987-06-09 | Trw Inc. | Superconducting analog-to-digital converter and digital magnetometer and related method for its use |
US5469057A (en) * | 1994-03-08 | 1995-11-21 | University Of New Mexico | Method and apparatus for extending the dynamic range of DC-squid measurements using a flux tracking loop |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH0816692B2 (en) * | 1990-09-30 | 1996-02-21 | ダイキン工業株式会社 | Magnetic flux lock method and device |
-
1996
- 1996-02-23 DE DE1996106655 patent/DE19606655C2/en not_active Expired - Fee Related
-
1997
- 1997-02-21 WO PCT/DE1997/000315 patent/WO1997031273A2/en not_active Application Discontinuation
- 1997-02-21 EP EP97917233A patent/EP0882241A2/en not_active Withdrawn
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4672359A (en) * | 1985-11-12 | 1987-06-09 | Trw Inc. | Superconducting analog-to-digital converter and digital magnetometer and related method for its use |
US5469057A (en) * | 1994-03-08 | 1995-11-21 | University Of New Mexico | Method and apparatus for extending the dynamic range of DC-squid measurements using a flux tracking loop |
Non-Patent Citations (3)
Title |
---|
DRUNG D: "DIGITAL FEEDBACK LOOPS FOR D.C. SQUIDS" CRYOGENICS, Bd. 26, Nr. 11, 1.November 1986, Seiten 623-627, XP002001907 * |
DRUNG D: "RECENT LOW TEMPERATURE SQUID DEVELOPMENTS" IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, Bd. 4, Nr. 3, 1.September 1994, Seiten 121-127, XP000444733 * |
KUNG P J ET AL: "A direct current superconducting quantum interference device gradiometer with a digital signal processor controlled flux-locked loop and comparison with a conventional analog feedback scheme" REVIEW OF SCIENTIFIC INSTRUMENTS, JAN. 1996, AIP, USA, Bd. 67, Nr. 1, ISSN 0034-6748, Seiten 222-229, XP002037208 * |
Also Published As
Publication number | Publication date |
---|---|
DE19606655A1 (en) | 1997-08-28 |
WO1997031273A3 (en) | 1997-10-02 |
DE19606655C2 (en) | 2002-04-11 |
EP0882241A2 (en) | 1998-12-09 |
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