CN109100664B - Method for measuring small space magnetic field - Google Patents
Method for measuring small space magnetic field Download PDFInfo
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- CN109100664B CN109100664B CN201810640286.8A CN201810640286A CN109100664B CN 109100664 B CN109100664 B CN 109100664B CN 201810640286 A CN201810640286 A CN 201810640286A CN 109100664 B CN109100664 B CN 109100664B
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- 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
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/0017—Means for compensating offset magnetic fields or the magnetic flux to be measured; Means for generating calibration magnetic fields
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- 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
- G01R33/06—Measuring direction or magnitude of magnetic fields or magnetic flux using galvano-magnetic devices
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
- G01V3/40—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for measuring magnetic field characteristics of the earth
Abstract
The invention discloses a method for measuring a small space magnetic field, which sequentially generates more than three uniform strong magnetic fields with known strength in the direction of the small space magnetic field to be measured, wherein the strength is more than 30 times of the strength of a magnetic interference field; the method comprises the steps of measuring a total magnetic field value of a space after superposition every time through an optical pump magnetometer, constructing an equation set about the small magnetic field intensity to be measured, the uniform strong magnetic field intensity, the magnetic interference field intensity, the total magnetic field value of the space and an included angle between the magnetic interference field and the optical pump magnetometer in the direction of the small magnetic field to be measured along the axis of the optical pump magnetometer by utilizing trigonometric function relation, and obtaining the strength value of the small magnetic field to be measured in the space by solving the equation set. The invention can realize the measurement of the small magnetic field change to be measured in space.
Description
Technical Field
The invention relates to the technical field of quantum precision measurement, in particular to a method for measuring a small space magnetic field.
Background
In the field of space magnetic field detection, the optical pump magnetometer is a scalar magnetometer which is most widely applied, has the advantages of wide measurement range, high sensitivity, high precision, quick frequency response and the like, and is commonly used for measuring the total intensity of a geomagnetic field. The optical pump magnetometer has a blind area in the measuring process, namely, the optical pump magnetometer can normally measure the magnetic field to be measured only when the included angle between the direction of the magnetic field to be measured and the optical axis of the magnetometer is within a certain specific range, otherwise, no signal exists.
When the optical pump magnetometer is carried on a high orbit satellite, the intensity of the geomagnetic field is only about 100nT magnitude and the magnetic interference of a satellite platform is still kept at the original level due to the fact that the optical pump magnetometer is far away from the earth. The magnetic interference includes: (1) soft magnetic interference, which is mainly generated by satellite-borne equipment, such as wireless equipment interference, various electrical equipment interference and the like, and the frequency of the interference is generally higher; (2) the hard magnetic interference is mainly related to satellite maneuvering and self materials, the frequency of the interference is close to the static magnetic field frequency, and the strength of the interference is many times larger than that of the soft magnetic interference. The magnetic interferences generated by the satellite platform are different in magnitude and unfixed in direction, so that the direction of the resultant field of the geomagnetic field to be measured is also unfixed, and the resultant field is easily separated from the working area of the optical pump magnetometer and cannot be effectively measured. Particularly, if the interference field is perpendicular to the geomagnetic field to be measured and is much larger than the geomagnetic field to be measured, the contribution of the geomagnetic field to be measured to the total magnetic field is far smaller than the resolution of the optical pumping magnetometer. When the geomagnetic field to be measured is in the magnitude of 100nT, and the satellite interference field is far larger than the geomagnetic field to be measured and reaches more than 30 times of the geomagnetic field, the geomagnetic field can be called as a small space magnetic field. Therefore, for the measurement of the small magnetic field in the space, the problems of the working blind area of the optical pump magnetometer, the incapability of measuring the small magnetic field and the like need to be solved.
At present, the commonly used space magnetic measurement equipment mainly comprises a fluxgate magnetometer and an optical pump magnetometer. Due to the limitation of the working principle, the fluxgate magnetometer has the problems of accumulation along with time and null shift in the temperature change process, and the accuracy of magnetic measurement data can be influenced. The sensitivity required by the current magnetic field measurement is very high, and a magnetic anomaly signal with pT magnitude or even lower needs to be measured, so that the fluxgate magnetometer has extremely low sensitivity.
Disclosure of Invention
In view of this, the invention provides a method for measuring a small magnetic field in a space, which can realize measurement of changes of the small magnetic field to be measured in the space.
The specific embodiment of the invention is as follows:
a method for measuring a small space magnetic field sequentially generates more than three uniform strong magnetic fields with known strength in the direction of the small space magnetic field to be measured, wherein the strength is more than 30 times of the strength of a magnetic interference field; the method comprises the steps of measuring a total magnetic field value of a space after superposition every time through an optical pump magnetometer, constructing an equation set about the small magnetic field intensity to be measured, the uniform strong magnetic field intensity, the magnetic interference field intensity, the total magnetic field value of the space and an included angle between the magnetic interference field and the optical pump magnetometer in the direction of the small magnetic field to be measured along the axis of the optical pump magnetometer by utilizing trigonometric function relation, and obtaining the strength value of the small magnetic field to be measured in the space by solving the equation set.
If the magnetic interference field is perpendicular to the direction of the small magnetic field to be detected and a uniform strong magnetic field superposed in the direction of the small magnetic field to be detected in the space is far larger than the magnetic interference field, the magnetic interference field can be ignored, the superposed space total magnetic field value is measured by the optical pump magnetometer, the difference between the space total magnetic field value and the uniform strong magnetic field strength value is the strength value of the small magnetic field to be detected along the direction of the small magnetic field to be detected along the axis of the optical pump magnetometer.
Further, the uniform strong magnetic field is generated in the direction of the small magnetic field to be measured by utilizing a Helmholtz coil.
Further, the measuring system adopted by the measuring method comprises: the device comprises a Helmholtz coil, an optical pump magnetometer, a current source and a signal detection and processing module;
the axis of the Helmholtz coil is along the direction of the small magnetic field to be detected, the magnetic sensitive probe of the optical pump magnetometer is placed in the center of the Helmholtz coil along the axis of the Helmholtz coil, the current source provides stable and constant current for the Helmholtz coil, and the signal detection and processing module processes and analyzes a magnetic field voltage signal output by the detection of the magnetic sensitive probe of the optical pump magnetometer to obtain the strength of the small magnetic field to be detected in the space.
Has the advantages that:
the invention can measure the small space magnetic field with determined magnetic field direction, generates uniform strong magnetic field with the same direction as the small magnetic field to be measured, measures the total field value of the superposed magnetic field by the optical pump magnetometer, can measure the small space magnetic field under the condition of large satellite magnetic interference, meets the requirement of measuring the geosynchronous orbit magnetic field, and is suitable for the magnetic field measurement of the high orbit satellite optical pump magnetometer load aiming at the small space magnetic field.
Drawings
FIG. 1 is a schematic view of a measurement system of the method of the present invention;
FIG. 2 is a magnetic field vector overlay that constructs a system of equations.
The device comprises a Helmholtz coil 1, an optical pump magnetometer magnetic sensitive probe 2, a current source 3 and a signal detection and processing module 4.
Detailed Description
The invention is described in detail below by way of example with reference to the accompanying drawings.
The optical pump magnetometer is a scalar magnetometer, a working blind area is formed in an area with a magnetic field direction being 90 degrees to the axis of the optical pump magnetometer, the rest areas are working areas, and an optimal working area is formed in an area with a magnetic field direction being 0 degree to the axis of the optical pump magnetometer. When the magnetic interference field is perpendicular to the optical axis of the magnetometer and much larger than the small magnetic field to be measured, the superposed field will be in the dead zone of the optical pump magnetometer, so that the measurement cannot be performed, and the contribution of the field to be measured to the total field is very little, which is far smaller than the resolution of the optical pump magnetometer. At this time, if a strong magnetic field far greater than the satellite magnetic interference field is generated in the direction of the small magnetic field to be measured by using the helmholtz coil, the total magnetic field direction is pulled back to the working area of the optical pump magnetometer according to the magnetic field vector superposition principle, so that the size of the total magnetic field of the small magnetic field to be measured in space, the satellite interference magnetic field and the uniform magnetic field generated by the helmholtz coil is measured.
The invention provides a method for measuring a small space magnetic field, wherein if a magnetic interference field is vertical to the direction of the small magnetic field to be measured, namely is positioned in a blind area of an optical pump magnetometer, a Helmholtz coil is utilized to increase a strong magnetic field in the direction of the small magnetic field to be measured, the strength of the strong magnetic field is more than 30 times of that of the magnetic interference field, the direction of a total magnetic field is always kept in a working area of the optical pump magnetometer, at the moment, the contribution of the magnetic interference field vertical to the direction of an optical axis to the total field is almost zero, the magnetic interference field can be ignored, the size of the small magnetic field to be measured is the variable quantity of a uniform magnetic field generated relative to the coil, and the contribution of the small. Knowing the magnitude and direction of the applied uniform strong magnetic field, the signal detection and processing module can finally give the strength value of the small magnetic field to be detected. Since the resolution of the optical pump magnetometer is in the order of pT, the measurement resolution for spatially small magnetic fields depends mainly on the accuracy with which the coils generate a uniform magnetic field.
The magnetic field measurement system for measuring a small magnetic field in a space is composed of an optical pump magnetometer, a Helmholtz coil 1, a current source 3 and a signal detection and processing module 4, as shown in FIG. 1. The Helmholtz coil 1 is formed by two coaxially arranged coils with the same radius and the same number of turns, the distance between the coils is equal to the radius, and the coils are connected in series in the middle. The helmholtz coil 1 can produce a homogeneous magnetic field over a large range around the middle point of the axis, the strength of which is proportional to the current passed in the coil. The radius is 13cm, the number of turns is 70, and when the current flowing in the coil is 0.1A, a uniform magnetic field of 50000nT along the axis can be generated in the vicinity of the middle point of the axis.
Magnetic sensitive probe of optical pump magnetometer 2: the magnetic sensor is used for sensing the size of a small space magnetic field, a satellite magnetic interference field and a superimposed field of a uniform magnetic field generated by a coil.
The axis of the Helmholtz coil 1 is along the direction of the small magnetic field to be measured, and the current source 3 provides steady current for the Helmholtz coil 1. The optical pump magnetometer magnetic sensitive probe 2 is placed in the center of the Helmholtz coil 1, the optical axis of the optical pump magnetometer magnetic sensitive probe coincides with the axis of the Helmholtz coil 1, the superposed total magnetic field of the uniform strong magnetic field generated by the Helmholtz coil 1 and the external magnetic field is measured, and the small magnetic field to be measured is almost in the same direction as the total magnetic field, so that the optical pump magnetometer can detect the change of the total magnetic field to be measured. Meanwhile, because the magnitude of the applied uniform strong magnetic field is known, the intensity of the small magnetic field to be measured in the space can be obtained through the signal detection and processing module 4.
If the magnetic interference field is not in the blind area of the optical pump magnetometer but in the working area, the superposed fields of the two fields can still be detected by the magnetometer, and the magnetic interference field can not be ignored. At the moment, the Helmholtz coil 1 is utilized to continuously generate more than three uniform strong magnetic fields with known strength in the direction of the small magnetic field to be measured, the numerical value of each total magnetic field is measured, an equation set related to the small magnetic field strength to be measured in the space, the uniform strong magnetic field strength, the magnetic interference field strength and the included angle between the magnetic interference field and the axial direction of the optical pump magnetometer is constructed by utilizing the cosine law, and the strength value of the small magnetic field to be measured in the space is obtained by solving the equation set.
The equation set construction method comprises the following steps: as shown in fig. 2, it is assumed that the intensity of the small magnetic field to be measured in the space is x, the intensity of the magnetic interference field is y, the axis of the optical pump magnetometer is along the direction of the small magnetic field to be measured, the included angle between the magnetic interference field and the axis of the optical pump magnetometer is θ, and x, y, and θ are unknown quantities. The intensity of the uniform strong magnetic field generated by the Helmholtz coil 1 is m respectively1、m2、m3、···、mn，n≥3。
In the formula, a1、a2、a3、···、anRepresenting the total magnetic field value obtained for each measurement.
In summary, the above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (4)
1. A method for measuring a small space magnetic field is characterized in that more than three uniform strong magnetic fields with known strength are sequentially generated in the direction of the small space magnetic field to be measured, and the strength is more than 30 times of the strength of a magnetic interference field; the method comprises the steps of measuring a total magnetic field value of a space after superposition every time through an optical pump magnetometer, constructing an equation set about the small magnetic field intensity to be measured, the uniform strong magnetic field intensity, the magnetic interference field intensity, the total magnetic field value of the space and an included angle between the magnetic interference field and the optical pump magnetometer in the direction of the small magnetic field to be measured along the axis of the optical pump magnetometer by utilizing trigonometric function relation, and obtaining the strength value of the small magnetic field to be measured in the space by solving the equation set.
2. A method for measuring a small space magnetic field is characterized in that if a magnetic interference field is perpendicular to the direction of the small space magnetic field to be measured and a uniform strong magnetic field superposed in the direction of the small space magnetic field to be measured is far larger than the magnetic interference field, the magnetic interference field can be ignored, a superposed total space magnetic field value is measured through an optical pumping magnetometer, the axis of the optical pumping magnetometer is along the direction of the small space magnetic field to be measured, and the difference between the total space magnetic field value and the uniform strong magnetic field strength value is the strength value of the small space magnetic field to be measured.
3. The method for measuring the small spatial magnetic field according to claim 1 or 2, wherein the strong uniform magnetic field is generated in the direction of the small magnetic field to be measured by using a helmholtz coil.
4. The method for measuring the small magnetic field in the space according to claim 1 or 2, wherein the measuring system adopted by the measuring method comprises: the device comprises a Helmholtz coil, an optical pump magnetometer, a current source and a signal detection and processing module;
the axis of the Helmholtz coil is along the direction of the small magnetic field to be detected, the magnetic sensitive probe of the optical pump magnetometer is placed in the center of the Helmholtz coil along the axis of the Helmholtz coil, the current source provides stable and constant current for the Helmholtz coil, and the signal detection and processing module processes and analyzes a magnetic field voltage signal output by the detection of the magnetic sensitive probe of the optical pump magnetometer to obtain the strength of the small magnetic field to be detected in the space.
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| DE19903296A1 (en) * | 1999-01-28 | 2000-08-24 | Bosch Gmbh Robert | Device and method for determining a magnetic field |
| JP5005256B2 (en) * | 2005-11-28 | 2012-08-22 | 株式会社日立ハイテクノロジーズ | Magnetic field measurement system and optical pumping magnetometer |
| CN101893721B (en) * | 2010-06-28 | 2012-10-03 | 吉林大学 | Wide-dynamic-range high-temperature superconducting magnetometer |
| CN102298122A (en) * | 2011-05-25 | 2011-12-28 | 中国船舶重工集团公司第七一○研究所 | Apparatus and method for measuring vertical component of magnetic induction intensity by optical pump |
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