Low frequency weak magnetic field calibration device and method

Abstract

The application discloses a low-frequency weak magnetic field calibration device and method, and relates to the technical field of magnetic field calibration, and aims at solving the problems of low-frequency weak magnetic field calibration devices that have high noise, high lower limit of reproduced magnetic field and low anti-interference ability. The device comprises a magnetic shielding chamber, a multilayer permalloy shielding cylinder, an integrated ferrite shielding cylinder, a zero-moment coil, a shunt, a low-frequency magnetic field excitation source, a data collector and an automatic degaussing device; the multilayer permalloy shielding cylinder, the integrated ferrite shielding cylinder, the zero-moment 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 multilayer permalloy shielding cylinder, and the zero-moment coil is placed in the integrated ferrite shielding cylinder and used for reproducing a weak magnetic field; a calibrated magnetic sensor is placed in the working area of the zero-moment coil, and the magnetic axes of the two are parallel; the low-frequency magnetic field excitation source supplies power to the zero-moment coil through the shunt, and the data collector collects the output signal of the calibrated magnetic sensor; and the automatic degaussing device is used for degaussing the multilayer permalloy shielding cylinder and the integrated ferrite shielding cylinder. The application has the advantages of small magnetic field noise, low lower limit of reproduced magnetic field and strong anti-interference ability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of metrology, in particular to a low-frequency weak magnetic field calibration device and method. BACKGROUND

[0002] The low-frequency weak magnetic field calibration device is mainly used for calibrating low-frequency weak magnetic field testing instruments such as inductive magnetometers and non-relaxation spin exchange (SERF) magnetometers, and mainly solves the calibration of parameters such as magnetic-electric conversion coefficient, linearity, magnetic field noise and indication error at different frequencies.

[0003] The traditional low-frequency weak magnetic field calibration device adopts a multi-layer permalloy magnetic shielding cylinder + magnetic field coil mode: the multi-layer permalloy magnetic shielding cylinder is used for shielding external interference magnetic field, and its low-frequency magnetic field noise is lowest and can be less than 10fT; the magnetic field coil passes through a small current, and can reproduce a low-frequency weak magnetic field of the order of 10 -12 T~10 -6 T). With the technical progress of low-frequency weak magnetic field testing instruments, the existing calibration device has the disadvantages of insufficient low magnetic field noise, insufficient lower limit of reproducible magnetic field, and large electrical interference of the matching equipment for calibration. SUMMARY

[0004] Therefore, the present application provides a low-frequency weak magnetic field calibration device and method, which has small magnetic field noise, low lower limit of reproducible magnetic field and strong anti-interference ability.

[0005] The technical scheme adopted by the present application is as follows:

[0006] A low-frequency weak magnetic field calibration device, comprising a magnetic shielding chamber, a multi-layer permalloy shielding cylinder, an integrated ferrite shielding cylinder, a non-moment coil, a shunt, a low-frequency magnetic field excitation source, a data collector and an automatic degaussing device.

[0007] The multi-layer permalloy shielding cylinder, the integrated ferrite shielding cylinder, the non-moment 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 non-moment coil is placed in the integrated ferrite shielding cylinder and used for reproducing a weak magnetic field; the calibrated magnetic sensor is placed in the working area of the non-moment coil, and the magnetic axes of the two are parallel; the low-frequency magnetic field excitation source supplies power to the non-moment coil through the shunt, and the data collector is used for collecting the output signal of the calibrated magnetic sensor; and the automatic degaussing device is used for degaussing the multi-layer permalloy shielding cylinder and the integrated ferrite shielding cylinder.

[0008] Further, the automatic degaussing device is located in the magnetic shielding chamber.

[0009] Further, the non-moment coil comprises coaxially sleeved inner and outer solenoids, and the inner and outer solenoids satisfy the following relationship:

[0010]

[0011] In the formula, 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 numbers of turns of the windings of the inner and outer solenoids respectively.

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

[0013] A low-frequency weak magnetic field calibration method, which adopts the low-frequency weak magnetic field calibration device, and the calibration method steps are as follows:

[0014] Step one, place the magnetic sensor to be calibrated in the working area of the zero-moment coil, and make the magnetic axis of the magnetic sensor to be calibrated parallel to the magnetic axis of the zero-moment coil;

[0015] Step two, demagnetize the multi-layer permalloy shielding cylinder and the integrated ferrite shielding cylinder by using the automatic demagnetizer;

[0016] Step three, supply power to the zero-moment coil by the shunt through the low-frequency magnetic field excitation source, and reproduce the required low-frequency standard magnetic field in the working area of the zero-moment coil;

[0017] Step four, measure the output signal of the magnetic sensor to be calibrated by using the data acquisition device, and the output signal is the magnetic field value or voltage value of the magnetic sensor to be calibrated;

[0018] Step five, obtain the magnetic field error or the magneto-electric conversion coefficient of the magnetic sensor to be calibrated by comparing the magnetic field value or the voltage value of the magnetic sensor to be calibrated with the low-frequency standard magnetic field value reproduced by the zero-moment coil;

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

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

[0021]

[0022] In the formula, B is the low-frequency standard magnetic field reproduced by the zero-moment coil; K B is the coil constant of the zero-moment coil; I is the output current of the low-frequency magnetic field excitation source; k I is the shunt ratio of the shunt.

[0023] Beneficial effects:

[0024] 1、 The present application utilizes combined shielding means, small magnetic field noise, strong anti-interference ability, utilizes shunt to supply power to the non-moment coil, can stably reproduce small low-frequency weak magnetic field, and the integrated ferrite shielding cylinder of the present application is integrally formed, has good shielding performance and low magnetic field noise.

[0025] 2、 The size design of the non-moment coil makes its magnetic moment approximately equal to 0, which can be ignored, and the magnetic field uniformity is good, and the mutual interference between the non-moment coil and the magnetic shielding cylinder and the magnetic shielding chamber when reproducing the magnetic field is small, and the influence can be ignored.

[0026] 3、 The resistance connection and resistance distribution of the shunt can make the shunt ratio meet the requirements of reproducing small low-frequency weak magnetic field. BRIEF DESCRIPTION OF DRAWINGS

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

[0028] Figure 2 It is a schematic diagram of the non-moment coil.

[0029] Figure 3 It is a schematic diagram of the connection of the shunt and the non-moment coil.

[0030] Among them, 1-magnetic shielding chamber, 2-multilayer permalloy shielding cylinder, 3-integrated ferrite shielding cylinder, 4-non-moment coil, 5-magnetic sensor to be calibrated, 6-shunt, 7-low-frequency magnetic field excitation source, 8-data collector, 9-automatic degaussing device. DETAILED DESCRIPTION

[0031] The present application will be described in detail below in combination with the drawings and examples.

[0032] The present application provides a low-frequency weak magnetic field calibration device, which comprises a magnetic shielding chamber 1, a multilayer permalloy shielding cylinder 2, an integrated ferrite shielding cylinder 3, a non-moment coil 4, a shunt 6, a low-frequency magnetic field excitation source 7, a data collector 8 and an automatic degaussing device 9.

[0033] The magnetic shielding chamber 1 is used for shielding external interference magnetic field, and the low-frequency magnetic shielding coefficient is ≥60dB;

[0034] The multilayer permalloy shielding cylinder 2 is used for shielding the remaining interference magnetic field in the magnetic shielding chamber 1, and the low-frequency magnetic shielding coefficient is ≥90dB;

[0035] The integrated ferrite shielding cylinder 3 is used for suppressing the self thermal noise of the multilayer permalloy shielding cylinder 2, and the self noise is ≤0.5fT;

[0036] The non-moment coil 4 is used for reproducing weak magnetic field, and the coil constant is 10μT / A~100μT / A;

[0037] Shunt 6 is used to shunt the power supply current from the low-frequency magnetic field excitation source 7 to the torqueless coil 4, with a shunt ratio of 1000:1 to 100000:1;

[0038] The low-frequency magnetic field excitation source 7 is used to power the torqueless coil 4, with an output of 0.1mA to 100mA;

[0039] Data acquisition unit 8 is used to acquire the output signal of the magnetic sensor 5 being calibrated;

[0040] Automatic demagnetizer 9 is used to demagnetize multi-layer permalloy shielding cylinder 2 and integrated ferrite shielding cylinder 3, reducing their internal DC residual magnetism.

[0041] The connection relationships between the above-mentioned components are as follows: Figure 1 As shown, the multi-layer permalloy shielding cylinder 2, the integrated ferrite shielding cylinder 3, the torque-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 inside the magnetic shielding chamber 1; in other embodiments, the automatic demagnetizer 9 can also be located outside the magnetic shielding chamber 1.

[0042] An integrated ferrite shielding cylinder 3 is nested inside a multi-layer permalloy shielding cylinder 2, and a torque-free coil 4 is placed inside the integrated ferrite shielding cylinder 3; the magnetic sensor 5 to be calibrated is placed in the working area of ​​the torque-free coil 4, with their magnetic axes parallel; a low-frequency magnetic field excitation source 7 supplies power to the torque-free coil 4 through a shunt 6; a data acquisition unit 8 is used to acquire the output signal of the magnetic sensor 5 to be calibrated; and an automatic demagnetizer 9 is used to demagnetize the multi-layer permalloy shielding cylinder 2 and the integrated ferrite shielding cylinder 3.

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

[0044]

[0045] In the formula, 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; and N1 and N2 are the number of turns of the inner and outer solenoid windings, respectively.

[0046] Shunt 6 includes resistors R1 and R2, such as Figure 3 As shown, resistor R1 is connected in series with the torqueless coil 4 and then in parallel with resistor R2; R2 = 1Ω, R1 = 1kΩ ~ 100kΩ, thus, the shunt ratio of shunt 6 reaches 1000:1 to 100000:1.

[0047] This 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 steps are as follows:

[0048] Step one, place the magnetic sensor 5 to be calibrated in the working area of the non-moment coil 4 in the above low frequency weak magnetic field calibration device, and make the magnetic axis of the magnetic sensor 5 to be calibrated parallel to the magnetic axis of the non-moment coil 4;

[0049] Step two, demagnetize the multi-layer permalloy shielding cylinder 2 and the integrated ferrite shielding cylinder 3 by using the automatic demagnetizer 9;

[0050] Step three, supply power to the non-moment coil 4 by the shunt 6 through the low frequency magnetic field excitation source 7, and reproduce the low frequency standard magnetic field required for calibration in the working area of the non-moment coil 4;

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

[0052]

[0053] In the formula, B is the low frequency standard magnetic field reproduced by the non-moment coil, the unit is T; K B is the coil constant of the non-moment coil, the unit is T / A; I is the output current of the low frequency magnetic field excitation source, the unit is A; k I is the shunt ratio of the shunt.

[0054] Step four, measure the output signal of the magnetic sensor 5 to be calibrated, that is, the indication value (the indication value is the magnetic field value or the voltage value) of the magnetic sensor 5 to be calibrated by using the data collector 8.

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

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

[0057] In summary, the above is only a preferred embodiment of the present application, and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A low frequency weak magnetic field calibration method, characterized in that, The low-frequency weak magnetic field calibration device comprises a magnetic shielding chamber, a multilayer permalloy shielding cylinder, an integrated ferrite shielding cylinder, a zero-moment coil, a shunt, a low-frequency magnetic field excitation source, a data collector and an automatic degaussing device; the multilayer permalloy shielding cylinder, the integrated ferrite shielding cylinder, the zero-moment coil, the shunt, the low-frequency magnetic field excitation source and the data collector are located in the magnetic shielding chamber; the integrated ferrite shielding cylinder is nested in the multilayer permalloy shielding cylinder, and the zero-moment coil is placed in the integrated ferrite shielding cylinder and used for reproducing a weak magnetic field; the calibrated magnetic sensor is placed in the working area of the zero-moment coil, and the magnetic axes of the two are parallel; the low-frequency magnetic field excitation source supplies power to the zero-moment coil through the shunt, and the data collector is used for collecting the output signal of the calibrated magnetic sensor; the automatic degaussing device is used for degaussing the multilayer permalloy shielding cylinder and the integrated ferrite shielding cylinder; the calibration method comprises the following steps: Step one, place the calibrated magnetic sensor in the working area of the zero-moment coil, and make the magnetic axis of the calibrated magnetic sensor parallel to the magnetic axis of the zero-moment coil; Step two, degauss the multilayer permalloy shielding cylinder and the integrated ferrite shielding cylinder by using the automatic degaussing device; Step three, supply power to the zero-moment coil through the shunt by using the low-frequency magnetic field excitation source to reproduce the required low-frequency standard magnetic field in the working area of the zero-moment coil; Step four, measure the output signal of the calibrated magnetic sensor by using the data collector, wherein the output signal is the magnetic field value or the voltage value of the calibrated magnetic sensor; Step five, obtain the magnetic field error or the magneto-electric conversion coefficient of the calibrated magnetic sensor by comparing the magnetic field value or the voltage value of the calibrated magnetic sensor with the low-frequency standard magnetic field value reproduced by the zero-moment coil; Step six, disconnect the output of the low-frequency magnetic field excitation source, and measure the output signal of the calibrated magnetic sensor in the magnetic shielding environment by using the data collector; if the output of the calibrated magnetic sensor is the magnetic field value, the magnetic field noise of the calibrated magnetic sensor is obtained; if the output of the calibrated magnetic sensor is the voltage value, the magnetic field noise of the calibrated magnetic sensor is obtained by dividing the voltage value by the magneto-electric conversion coefficient obtained in step five.

2. The low frequency weak magnetic field calibration method of claim 1, wherein, In step three, 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 non-rotating coil; K B is the coil constant of the non-rotating coil; I is the output current of the low frequency magnetic field excitation source; k I is the shunt ratio of the shunt.

Images