Low-frequency weak magnetic field calibration device and method

Abstract

The invention discloses a low-frequency weak magnetic field calibration device and method. The device comprises a magnetic shielding chamber, a multi-layer permalloy shielding cylinder, an integrated ferrite shielding cylinder, a torque-free coil, a shunt, a low-frequency magnetic field excitation source, a data collector and an automatic magnetic eraser. The multi-layer permalloy shielding cylinder, the integrated ferrite shielding cylinder, the torque-free coil, the shunt, the low-frequency magnetic field excitation source and the data collector are all located in the magnetic shielding chamber; the integrated ferrite shielding cylinder is nested in the multi-layer permalloy shielding cylinder, and the torque-free coil is placed in the integrated ferrite shielding cylinder and used for reproducing a weak magnetic field; a calibrated magnetic sensor is placed in a working area of the torque-free coil, and magnetic axes of the two are parallel; the low-frequency magnetic field excitation source supplies power to the torque-free coil through the shunt, and the data collector collects output signals of the calibrated magnetic sensor. The automatic demagnetizer is used for demagnetizing the multi-layer permalloy shielding cylinder and the integrated ferrite shielding cylinder. The magnetic field noise is low, the lower limit of the reproduction magnetic field is low, and the external interference resistance is high.

Description

Technical Field

[0001] The present invention relates to the field of measurement technology, and in particular to a low-frequency weak magnetic field calibration device and method. Background Art

[0002] The low-frequency weak magnetic field calibration device is mainly used to calibrate low-frequency weak magnetic field test instruments such as induction magnetometers and non-relaxation spin exchange (SERF) magnetometers. It mainly solves the calibration of parameters such as magneto-electric conversion coefficient, linearity, magnetic field noise, indication error, etc. at different frequencies.

[0003] The traditional low-frequency weak magnetic field calibration device adopts a multi-layer Permalloy magnetic shielding tube + magnetic field coil: the multi-layer Permalloy magnetic shielding tube is used to shield the external interference magnetic field, and its low-frequency magnetic field noise can be as low as less than 10fT; the magnetic field coil passes a small current, which can reproduce the petascale to microscale (10 -12 T~10 -6 With the technical progress of low-frequency weak magnetic field testing instruments, the existing calibration devices have shortcomings such as insufficient magnetic field noise, insufficient lower limit of the reproduced magnetic field, and large electrical interference of the calibration equipment. Summary of the invention

[0004] In view of this, the present invention provides a low-frequency weak magnetic field calibration device and method, which has low magnetic field noise, low lower limit of reproduced magnetic field, and strong ability to resist external interference.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A low-frequency weak magnetic field calibration device comprises a magnetic shielding room, a multi-layer Permalloy shielding cylinder, an integrated ferrite shielding cylinder, a moment-free coil, a shunt, a low-frequency magnetic field excitation source, a data collector and an automatic demagnetizer;

[0007] The multi-layer Permalloy shielding tube, the integrated ferrite shielding tube, the moment-free coil, the shunt, the low-frequency magnetic field excitation source and the data collector are all located in the magnetic shielding room; the integrated ferrite shielding tube is nested in the multi-layer Permalloy shielding tube, and the moment-free coil is placed in the integrated ferrite shielding tube to reproduce the weak magnetic field; the calibrated magnetic sensor is placed in the working area of ​​the moment-free coil, and the magnetic axes of the two are parallel; the low-frequency magnetic field excitation source supplies power to the moment-free coil through the shunt, and the data collector is used to collect the output signal of the calibrated magnetic sensor; the automatic demagnetizer is used to demagnetize the multi-layer Permalloy shielding tube and the integrated ferrite shielding tube.

[0008] Furthermore, the automatic demagnetizer is located in the magnetic shielding room.

[0009] Furthermore, the moment-free coil includes inner and outer solenoids coaxially mounted, and the inner and outer solenoids satisfy the following relationship:

[0010]

[0011] Where D1 and D2 are the diameters of the inner and outer solenoids, respectively; L1 and L2 are the winding lengths of the inner and outer solenoids, respectively; N1 and N2 are the number of turns of the inner and outer solenoid windings, respectively.

[0012] Furthermore, the shunt includes a resistor R1 and a resistor R2, wherein the resistor R1 is connected in series with the moment-free coil and then connected in parallel with the resistor R2; R2=1Ω, R1=1kΩ~100kΩ.

[0013] A low-frequency weak magnetic field calibration method, using the low-frequency weak magnetic field calibration device mentioned above, the calibration method steps are as follows:

[0014] Step 1: Place the calibrated magnetic sensor in the working area of ​​the moment-free coil, and make the magnetic axis of the calibrated magnetic sensor parallel to the magnetic axis of the moment-free coil;

[0015] Step 2, demagnetizing the multi-layer Permalloy shielding tube and the integrated ferrite shielding tube using an automatic demagnetizer;

[0016] Step 3, using a low-frequency magnetic field excitation source to power the moment-free coil through a shunt, and reproducing the low-frequency standard magnetic field required for calibration in the working area of ​​the moment-free coil;

[0017] Step 4, using a data acquisition device to measure the output signal of the calibrated magnetic sensor, wherein the output signal is a magnetic field value or a voltage value of the calibrated magnetic sensor;

[0018] Step 5: By comparing the magnetic field value or voltage value of the calibrated magnetic sensor with the low-frequency standard magnetic field value reproduced by the moment-free coil, the magnetic field error or magneto-electric conversion coefficient of the calibrated magnetic sensor is obtained;

[0019] Step six, disconnect the output of the low-frequency magnetic field excitation source, and use a data acquisition device to measure the output signal of the calibrated magnetic sensor in a magnetic shielding environment. If the output of the calibrated magnetic sensor is a magnetic field value, it is the magnetic field noise of the calibrated magnetic sensor; if the output of the calibrated magnetic sensor is a voltage value, the voltage value is divided by the magneto-electric conversion coefficient obtained in step five to obtain the magnetic field noise of the calibrated magnetic sensor.

[0020] Furthermore, in step 3, the magnetic field value of the low-frequency standard magnetic field is calculated as follows:

[0021]

[0022] Where B is the low-frequency standard magnetic field reproduced by the momentless coil; K B is the coil constant of the momentless coil; I is the output current of the low-frequency magnetic field excitation source; k I is the split ratio of the splitter.

[0023] Beneficial effects:

[0024] 1. The present invention utilizes a combined shielding method, has low magnetic field noise, and has strong resistance to external interference. The shunt is used to shunt the power to the moment-free coil, which can stably reproduce a tiny low-frequency weak magnetic field. In addition, the one-piece ferrite shielding tube used in the present invention is integrally formed, has good shielding performance, and has low magnetic field noise.

[0025] 2. The dimension design of the moment-free coil of the present invention makes its magnetic moment approximately equal to 0, which can be ignored, and the magnetic field uniformity is good. When the moment-free coil reproduces the magnetic field, the mutual interference between the magnetic shielding tube and the magnetic shielding room is small, and its influence can be ignored.

[0026] 3. The resistance connection and resistance distribution of the shunt of the present invention can make its shunt ratio meet the requirements of reproducing a tiny low-frequency weak magnetic field. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the composition of the present invention.

[0028] Figure 2 Schematic diagram of a momentless coil.

[0029] Figure 3 This is a schematic diagram of the connection between the shunt and the moment-free coil.

[0030] Among them, 1-magnetic shielding room, 2-multi-layer Permalloy shielding tube, 3-integrated ferrite shielding tube, 4-momentless coil, 5-calibrated magnetic sensor, 6-shunt, 7-low-frequency magnetic field excitation source, 8-data collector, 9-automatic demagnetizer. DETAILED DESCRIPTION

[0031] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0032] The present invention provides a low-frequency weak magnetic field calibration device, comprising a magnetic shielding room 1, a multi-layer Permalloy shielding tube 2, an integrated ferrite shielding tube 3, a moment-free coil 4, a shunt 6, a low-frequency magnetic field excitation source 7, a data collector 8 and an automatic demagnetizer 9;

[0033] Magnetic shielding room 1, used to shield external interference magnetic field, low-frequency magnetic shielding coefficient ≥ 60dB;

[0034] The multi-layer Permalloy shielding tube 2 is used to shield the remaining interference magnetic field in the magnetic shielding room 1, and the low-frequency magnetic shielding coefficient is ≥90dB;

[0035] The integrated ferrite shielding tube 3 is used to suppress the internal thermal noise of the multi-layer Permalloy shielding tube 2, and the self-noise is ≤0.5fT;

[0036] Moment-free coil 4, used to reproduce weak magnetic field, coil constant 10μT / A~100μT / A;

[0037] The shunt 6 is used to shunt the power supply current from the low-frequency magnetic field excitation source 7 to the moment-free coil 4, and the shunt ratio is 1000:1 to 100000:1;

[0038] A low-frequency magnetic field excitation source 7 is used to supply power to the moment-free coil 4, and outputs 0.1 mA to 100 mA;

[0039] A data collector 8, used for collecting the output signal of the calibrated magnetic sensor 5;

[0040] The automatic demagnetizer 9 is used for demagnetizing the multi-layer Permalloy shielding tube 2 and the integrated ferrite shielding tube 3 to reduce the internal DC residual magnetism.

[0041] The connection relationship between the above components is as follows: Figure 1 As shown, the multi-layer Permalloy shielding tube 2, the integrated ferrite shielding tube 3, the moment-free coil 4, the shunt 6, the low-frequency magnetic field excitation source 7, the data acquisition device 8 and the automatic demagnetizer 9 are all located in the magnetic shielding room 1; in other embodiments, the automatic demagnetizer 9 can also be arranged outside the magnetic shielding room 1.

[0042] The integrated ferrite shielding tube 3 is nested in the multi-layer Permalloy shielding tube 2, and the moment-free coil 4 is placed in the integrated ferrite shielding tube 3; the calibrated magnetic sensor 5 is placed in the working area of ​​the moment-free coil 4, and the magnetic axes of the two are parallel; the low-frequency magnetic field excitation source 7 supplies power to the moment-free coil 4 through the shunt 6; the data acquisition device 8 is used to collect the output signal of the calibrated magnetic sensor 5; the automatic demagnetizer 9 is used to demagnetize the multi-layer Permalloy shielding tube 2 and the integrated ferrite shielding tube 3.

[0043] Specifically, Figure 2 As shown, the moment-free coil 4 includes inner and outer solenoids coaxially mounted, and the inner and outer solenoids satisfy the following relationship:

[0044]

[0045] Where D1 and D2 are the diameters of the inner and outer solenoids, respectively; L1 and L2 are the winding lengths of the inner and outer solenoids, respectively; N1 and N2 are the number of turns of the inner and outer solenoid windings, respectively.

[0046] The shunt 6 includes a resistor R1 and a resistor R2. Figure 3 As shown, the resistor R1 is connected in series with the moment-free coil 4 and then connected in parallel with the resistor R2; R2=1Ω, R1=1kΩ~100kΩ, thereby, the shunt ratio of the shunt 6 reaches 1000:1 to 100000:1.

[0047] The present invention also provides a low-frequency weak magnetic field calibration method. Based on the above-mentioned low-frequency weak magnetic field calibration device, the calibration method has the following steps:

[0048] Step 1: Place the calibrated magnetic sensor 5 in the working area of ​​the moment-free coil 4 in the low-frequency weak magnetic field calibration device, and make the magnetic axis of the calibrated magnetic sensor 5 parallel to the magnetic axis of the moment-free coil 4;

[0049] Step 2, demagnetizing the multi-layer Permalloy shielding tube 2 and the integrated ferrite shielding tube 3 using an automatic demagnetizer 9;

[0050] Step 3, use a low-frequency magnetic field excitation source 7 to power the moment-free coil 4 through the shunt 6, and reproduce the low-frequency standard magnetic field required for calibration in the working area of ​​the moment-free coil 4;

[0051] The magnetic field value calculation method of the low-frequency standard magnetic field is as follows:

[0052]

[0053] Where, B is the low-frequency standard magnetic field reproduced by the momentless coil, in T; K B is the coil constant of the moment-free coil, in T / A; I is the output current of the low-frequency magnetic field excitation source, in A; k I is the split ratio of the splitter.

[0054] Step 4: Use the data acquisition device 8 to measure the output signal of the calibrated magnetic sensor 5, that is, the indicated value of the calibrated magnetic sensor 5 (the indicated value is a magnetic field value or a voltage value).

[0055] Step 5: By comparing the magnetic field value or voltage value of the calibrated magnetic sensor 5 with the low-frequency standard magnetic field value reproduced by the moment-free coil 4, the magnetic field error or magneto-electric conversion coefficient (the voltage divided by the magnetic field is the magneto-electric conversion coefficient) of the calibrated magnetic sensor 5 is obtained.

[0056] Step six, disconnect the output of the low-frequency magnetic field excitation source 7, and use the data acquisition device 8 to measure the output signal of the calibrated magnetic sensor 5 in the magnetic shielding environment. If the output of the calibrated magnetic sensor 5 is a magnetic field value, it is the magnetic field noise of the calibrated magnetic sensor 5; if the output of the calibrated magnetic sensor 5 is a voltage value, the voltage value is divided by the magneto-electric conversion coefficient obtained in step five to obtain the magnetic field noise of the calibrated magnetic sensor 5.

[0057] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A low-frequency weak magnetic field calibration device, characterized in that: It includes a magnetic shielding room, a multi-layer Permalloy shielding tube, an integrated ferrite shielding tube, a moment-free coil, a shunt, a low-frequency magnetic field excitation source, a data collector and an automatic degaussing device; The multi-layer Permalloy shielding tube, the integrated ferrite shielding tube, the moment-free coil, the shunt, the low-frequency magnetic field excitation source and the data collector are all located in the magnetic shielding room; the integrated ferrite shielding tube is nested in the multi-layer Permalloy shielding tube, and the moment-free coil is placed in the integrated ferrite shielding tube to reproduce the weak magnetic field; the calibrated magnetic sensor is placed in the working area of ​​the moment-free coil, and the magnetic axes of the two are parallel; the low-frequency magnetic field excitation source supplies power to the moment-free coil through the shunt, and the data collector is used to collect the output signal of the calibrated magnetic sensor; the automatic demagnetizer is used to demagnetize the multi-layer Permalloy shielding tube and the integrated ferrite shielding tube.

2. The low-frequency weak magnetic field calibration device according to claim 1, characterized in that: The automatic degaussing device is located in the magnetic shielding room.

3. The low-frequency weak magnetic field calibration device according to claim 1, characterized in that: The moment-free coil includes inner and outer solenoids coaxially mounted, and the inner and outer solenoids satisfy the following relationship: Where D1 and D2 are the diameters of the inner and outer solenoids, respectively; L1 and L2 are the winding lengths of the inner and outer solenoids, respectively; N1 and N2 are the number of turns of the inner and outer solenoid windings, respectively.

4. The low-frequency weak magnetic field calibration device according to claim 1 or 3, characterized in that: The shunt comprises a resistor R1 and a resistor R2. The resistor R1 is connected in series with the moment-free coil and then connected in parallel with the resistor R2; R2 = 1Ω, R1 = 1kΩ to 100kΩ.

5. A low-frequency weak magnetic field calibration method, characterized in that: Using the low-frequency weak magnetic field calibration device as claimed in claim 1, the calibration method steps are as follows: Step 1: Place the calibrated magnetic sensor in the working area of ​​the moment-free coil, and make the magnetic axis of the calibrated magnetic sensor parallel to the magnetic axis of the moment-free coil; Step 2, demagnetizing the multi-layer Permalloy shielding tube and the integrated ferrite shielding tube using an automatic demagnetizer; Step 3, using a low-frequency magnetic field excitation source to power the moment-free coil through a shunt, and reproducing the low-frequency standard magnetic field required for calibration in the working area of ​​the moment-free coil; Step 4, using a data acquisition device to measure the output signal of the calibrated magnetic sensor, wherein the output signal is a magnetic field value or a voltage value of the calibrated magnetic sensor; Step 5: By comparing the magnetic field value or voltage value of the calibrated magnetic sensor with the low-frequency standard magnetic field value reproduced by the moment-free coil, the magnetic field error or magneto-electric conversion coefficient of the calibrated magnetic sensor is obtained; Step six, disconnect the output of the low-frequency magnetic field excitation source, and use a data acquisition device to measure the output signal of the calibrated magnetic sensor in a magnetic shielding environment. If the output of the calibrated magnetic sensor is a magnetic field value, it is the magnetic field noise of the calibrated magnetic sensor; if the output of the calibrated magnetic sensor is a voltage value, the voltage value is divided by the magneto-electric conversion coefficient obtained in step five to obtain the magnetic field noise of the calibrated magnetic sensor.

6. The low-frequency weak magnetic field calibration method according to claim 5, characterized in that: In step 3, the magnetic field value of the low-frequency standard magnetic field is calculated as follows: Where B is the low-frequency standard magnetic field reproduced by the momentless coil; K B is the coil constant of the momentless coil; I is the output current of the low-frequency magnetic field excitation source; k I is the split ratio of the splitter.

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