Magnetic material eddy current magnetic field measurement system

Abstract

The invention provides a magnetic material eddy current magnetic field measurement system, which is characterized in that the direct proportion relation exists between the sum of a coil excitation magnetic field and an induced magnetic field of a measured object and current, and the product of the proportion coefficient sum and a real-time current value is utilized to replace the interference of the coil excitation magnetic field and the induced magnetic field when the eddy current magnetic field in a variable magnetic field is measured. The problem that only eddy magnetic fields for non-magnetic materials can be measured is solved, eddy magnetic fields of various materials (non-magnetic, low-magnetic and magnetic materials) can be measured, and the application range is wide.

Description

Technical Field

[0001] The invention relates to the technical field of eddy current magnetic field measurement, and in particular to an eddy current magnetic field measurement system for magnetic materials. Background Art

[0002] There are currently two methods for measuring eddy current magnetic fields: one is to use mechanical movement to make the object cut a constant magnetic field, thereby forming an eddy current magnetic field; the other is to use a coil to generate a regularly changing current, change the magnetic flux of the object, and thus form an eddy current magnetic field. The essence of the two methods is the same, that is, the relative movement of the object and the magnetic field causes the change of the magnetic flux of the object, thereby generating an eddy current magnetic field. However, the operability of controlling the regular movement of the object is poor, and the measurement difficulty is relatively high. Therefore, the second method is generally used in the laboratory to measure the eddy current magnetic field of the object.

[0003] However, the second method of measuring the eddy current magnetic field of an object has certain limitations, that is, it can only measure the eddy current magnetic field of non-magnetic materials, such as aluminum and copper (reference "Research on Eddy Current Magnetic Field Measurement Method"). The purpose of using such metal materials is mainly to eliminate the induced magnetic field generated by the magnetic material under the influence of the changing magnetic field. However, the materials used in specific equipment are diverse, which may include non-magnetic and magnetic materials. Therefore, the eddy current magnetic field of the equipment cannot be measured by the previous eddy current magnetic field measurement method. Summary of the invention

[0004] The technical problem to be solved by the present invention is that the existing eddy current magnetic field measurement method avoids the corresponding induced magnetic field generated by the magnetic material as the external magnetic field changes, and cannot measure the size of the eddy current magnetic field of the actual equipment containing magnetic materials, so it can only measure the eddy current magnetic field of non-magnetic materials.

[0005] In order to solve the above technical problems, the technical solution of the present invention provides a magnetic material eddy current magnetic field measurement system, including a magnetic field measurement device and a corresponding magnetic field measurement method;

[0006] The magnetic field measurement device includes:

[0007] n measuring magnetic sensors disposed below the magnetic material, used to measure a first magnetic field value, a second magnetic field value or a third magnetic field value of the real-time magnetic field of the magnetic material, wherein the first magnetic field value includes the sum of the magnetic field values ​​of the earth's magnetic field and the induced magnetic field of the magnetic material under the earth's magnetic field;

[0008] a magnetic field excitation coil, which surrounds the outside of the center point between the magnetic material and the n measuring magnetic sensors, generates a uniform excitation coil magnetic field and an induced magnetic field of the magnetic material under the excitation coil magnetic field when a constant current is passed through it, and generates an additional eddy current magnetic field when a variable current is passed through it, the second magnetic field value includes the excitation coil magnetic field and the induced magnetic field of the magnetic material under the excitation coil magnetic field, and the third magnetic field value includes the excitation coil magnetic field, the induced magnetic field of the magnetic material under the excitation coil magnetic field, and the eddy current magnetic field;

[0009] A power supply, connected to the magnetic field excitation coil, for providing a constant current to the magnetic field excitation coil to generate the magnetic field of the excitation coil and the induced magnetic field of the magnetic material under the magnetic field of the excitation coil, or providing a changing current with a periodic change law to generate the magnetic field of the excitation coil and the induced magnetic field and eddy current magnetic field of the magnetic material under the magnetic field of the excitation coil;

[0010] A data acquisition module is connected to the power supply and the n measuring magnetic sensors, respectively, and is used to obtain a constant current signal or a changing current signal corresponding to the constant current or the changing current of the power supply, and a first electrical signal, a second electrical signal or a third signal having a first magnetic field value, a second magnetic field value or a third magnetic field value, and convert the first electrical signal, the second electrical signal or the third signal into a first magnetic field signal, a second magnetic field signal or a third magnetic field signal;

[0011] A background magnetic sensor is connected to the data acquisition module, measures the fourth magnetic field value of the earth's magnetic field and converts it into a fourth magnetic field signal and transmits it to the data acquisition module;

[0012] an industrial computer, connected to the data acquisition module and the power supply, respectively, for obtaining a constant current signal or a variable current signal, a fourth magnetic field signal, and a first magnetic field signal, a second magnetic field signal, or a third magnetic field signal from the data acquisition module to perform eddy current magnetic field calculation, and controlling the power supply switch to energize the magnetic field excitation coil;

[0013] The magnetic field measuring method corresponding to the magnetic field measuring device comprises the following steps:

[0014] Step 1: The industrial computer controls the power supply to be in a turned-off state. At this time, the magnetic field measuring device is not powered on. The data acquisition module obtains electrical signals having a first magnetic field value and a fourth magnetic field value from n measuring magnetic sensors and a background magnetic sensor in real time, converts them into a first magnetic field signal and a fourth magnetic field signal, and transmits them to the industrial computer. The industrial computer calculates the change value of the first magnetic field value and the change value of the fourth magnetic field value, respectively, and adjusts the difference between the change value of the first magnetic field value and the change value of the fourth magnetic field value to zero, thereby achieving zero adjustment of the magnetic field measuring device, thereby eliminating interference from the earth's magnetic field.

[0015] Step 2: The industrial computer controls the power supply to be turned on and passes a constant current. At this time, the magnetic field measuring device is powered on. The data acquisition module obtains the electrical signal with the second magnetic field value from the n measuring magnetic sensors, converts it into a second magnetic field signal, and obtains a constant current signal from the power supply, and transmits the second magnetic field signal and the constant current signal to the industrial computer;

[0016] Step 3: The industrial computer analyzes the second magnetic field signal and the constant current signal to obtain a second magnetic field value and a constant current value, and determines the proportional coefficient according to the proportional coefficient formula;

[0017] Step 4: The industrial computer controls the power supply to be turned on and passes a changing current. At this time, the magnetic field measuring device is powered on. The data acquisition module obtains the electrical signal with the third magnetic field value from the n measuring magnetic sensors, converts it into a third magnetic field signal, and obtains the changing current signal from the power supply. The signal is transmitted to the industrial computer for analysis to obtain the third magnetic field value and the changing current value. The eddy current magnetic field is determined according to the eddy current magnetic field value calculation formula combined with the proportional coefficient.

[0018] Preferably, the number of n measuring magnetic sensors, the spacing between the measuring magnetic sensors, and the distance between the measuring magnetic sensors and the magnetic material are determined according to the size of the magnetic material.

[0019] Preferably, the proportionality coefficient formula is as follows:

[0020] B x =k1·I

[0021] B ix =k2·I

[0022] B1=B x +B ix =(k1+k2)·I=K·I

[0023]

[0024] Where I is the constant current value, B x is the value of the magnetic field of the excitation coil in the second magnetic field value, k1 is the ratio of the value of the magnetic field of the excitation coil to the constant current value; B ix is the induced magnetic field of the magnetic material under the magnetic field of the excitation coil, k2 is the ratio of the induced magnetic field of the magnetic material under the magnetic field of the excitation coil to the constant current value, B1 is the second magnetic field value, and K is the proportional coefficient.

[0025] Preferably, the eddy current magnetic field value calculation formula is as follows:

[0026] B w =B-(B x +B ix )=BK·I i

[0027] Among them, B w is the value of the eddy current magnetic field in the third magnetic field value, B is the third magnetic field value, I i is the changing current value.

[0028] Preferably, the varying current includes a current with a sinusoidal and / or ramp waveform.

[0029] Preferably, the uniformity of the magnetic field generated by the magnetic field excitation coil is between [95%, 100%].

[0030] Preferably, the time drift of the measuring magnetic sensor is between [0nT, 2nT].

[0031] Preferably, the fluctuation range of the constant current is between [-0.001, 0.001].

[0032] Preferably, the first magnetic field value, the second magnetic field value and the third magnetic field value all include a fixed magnetic field of a magnetic material.

[0033] Preferably, a diverter is provided inside the data acquisition module.

[0034] The technical solution of the present invention proposes a system for measuring eddy current magnetic fields of magnetic materials. The positive proportional relationship between the sum of the coil excitation magnetic field, the induced magnetic field of the object being measured and the current is used. The product of the proportional coefficient and the real-time current value is used to replace the interference of the coil excitation magnetic field and the induced magnetic field when measuring the eddy current magnetic field in a changing magnetic field, thereby solving the problem that only eddy current magnetic fields of non-magnetic materials can be measured. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic structural diagram of a device for measuring eddy current magnetic field of a magnetic material provided by an embodiment of the present invention;

[0036] Figure 2 A schematic diagram of eddy current magnetic field values ​​at corresponding measuring points of a device measured by an eddy current magnetic field measuring device with magnetic material provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0038] like Figure 1 As shown, the present invention provides a system for measuring eddy current magnetic field of magnetic materials. Specifically, the system includes: a background magnetic sensor for detecting fluctuations in the earth's magnetic field; a measuring magnetic sensor for measuring the real-time magnetic field under the magnetic material; an excitation magnetic field coil for simulating magnetic field changes to make the magnetic material generate an induced magnetic field and an eddy current magnetic field; a power supply module for powering the excitation magnetic field coil; a data acquisition module for data acquisition, coil current monitoring, etc.; and an industrial computer for data post-processing. The uniformity of the magnetic field generated by the magnetic field excitation coil is between [95%, 100%]. A shunt is provided inside the data acquisition module.

[0039] Furthermore, the measuring magnetic sensor selects the number, spacing and distance from the magnetic material according to the size of the magnetic material, and is fixed at the bottom of the magnetic material; the background magnetic sensor obtains the earth's magnetic field signal as a basis for the measuring magnetic sensor to deduct the earth's magnetic field interference, and is placed far away from the magnetic field model excitation coil and cannot be affected by the magnetic field of the magnetic field excitation coil;

[0040] Furthermore, the power supply module provides a constant current and a changing current of a sine and / or ramp waveform for the excitation magnetic field coil, and has a communication interface with the industrial computer to realize the current input and output control of the industrial computer;

[0041] Furthermore, the data acquisition module includes a synchronous and real-time acquisition of magnetic field data and current data; a power supply module for voltage conversion, and a communication module for data transmission with an industrial computer.

[0042] Furthermore, the post-processing of the industrial computer includes the following steps:

[0043] Step 1: Before the coil is powered on, the position of the object to be measured is arranged according to the test technical plan, and the number, gap and height of the magnetic sensors are measured. Each measuring magnetic sensor is horizontally calibrated by a level ruler;

[0044] Step 2: After the preparation work is completed, the industrial computer obtains the change value of each measuring magnetic sensor. If the magnetic field change value of each measuring magnetic sensor is less than 2nT in real time, the test can be carried out; if the magnetic field change value of a measuring magnetic sensor is greater than 2nT in real time, the measuring magnetic sensor needs to be calibrated or replaced until the magnetic field change value of the measuring magnetic sensor is less than 2nT in real time; the time drift of the measuring magnetic sensor is between [0nT, 2nT]

[0045] Step 3: The industrial computer controls the power supply to be in a turned-off state. At this time, the magnetic field measuring device is not powered on. The data acquisition module obtains the electrical signals having the first magnetic field value and the fourth magnetic field value from the n measuring magnetic sensors and the background magnetic sensor in real time, converts them into the first magnetic field signal and the fourth magnetic field signal, and transmits them to the industrial computer. The industrial computer calculates the change value of the first magnetic field value and the change value of the fourth magnetic field value respectively, and adjusts the difference between the change value of the first magnetic field value and the change value of the fourth magnetic field value to zero, thereby achieving zero adjustment of the magnetic field measuring device, thereby eliminating the interference of the earth's magnetic field.

[0046] Step 4: The industrial computer controls the power supply to be turned on and passes a constant current. At this time, the magnetic field measuring device is powered on. The data acquisition module obtains the electrical signal with the second magnetic field value from the n measuring magnetic sensors, converts it into a second magnetic field signal, and obtains the constant current signal from the power supply, and transmits the second magnetic field signal and the constant current signal to the industrial computer; the fluctuation range of the constant current, that is, the ratio of the actual output value to the rated value is between [-0.001, 0.001].

[0047] Step 5: The industrial computer analyzes the second magnetic field signal and the constant current signal to obtain a second magnetic field value and a constant current value, and determines the proportional coefficient according to the proportional coefficient formula;

[0048] Step 6: The industrial computer controls the power supply to be turned on and passes a changing current. At this time, the magnetic field measuring device is powered on. The data acquisition module obtains the electrical signal with the third magnetic field value from the n measuring magnetic sensors, converts it into a third magnetic field signal, and obtains the changing current signal from the power supply in real time and synchronously. The signal is transmitted to the industrial computer for analysis to obtain the third magnetic field value and the changing current value, and the eddy current magnetic field is determined according to the eddy current magnetic field value calculation formula combined with the proportional coefficient.

[0049] Preferably, the proportionality coefficient formula is as follows:

[0050] B x =k1·I

[0051] B ix =k2·I

[0052] B1=B x +B ix =(k1+k2)·I=K·I

[0053]

[0054] Among them, I is the value corresponding to the current, B x is the value of the coil excitation magnetic field, k1 is the ratio of the coil excitation magnetic field value to the current; B ix is the induced magnetic field of the object being measured, k2 is the ratio of the coil excitation magnetic field value to the current, B1 is the real-time magnetic field data collected when a constant current is passed through the magnetic field excitation coil, and K is the proportional coefficient.

[0055] Preferably, the value B corresponding to the changing magnetic field x The value B corresponding to the induced magnetic field ix The sum is directly proportional to the value corresponding to the current.

[0056] Preferably, the eddy current magnetic field value formula is as follows:

[0057] B w =B-(Bx +B ix )=BK·I i

[0058] Among them, B w is the eddy current magnetic field value, B is the real-time magnetic field data collected when the magnetic field excitation coil is fed with a changing current, and I i is the current value at each moment.

[0059] like Figure 2 As shown, one of the sensors is arranged 15 cm directly below the device, the coil excitation current is 5A and rises continuously per second, and the eddy current magnetic field value at this point is measured to be about 100nT.

[0060] The technical solution of the present invention proposes a system for measuring eddy current magnetic fields of magnetic materials. The positive proportional relationship between the sum of the coil excitation magnetic field, the induced magnetic field of the measured object and the current is used. The product of the proportional coefficient and the real-time current value is used to replace the interference of the coil excitation magnetic field and the induced magnetic field when measuring the eddy current magnetic field in a changing magnetic field. This solves the problem of only being able to measure the eddy current magnetic field of non-magnetic materials. The system can measure the eddy current magnetic fields of a variety of materials (non-magnetic, low-magnetic and magnetic materials) and has a wide range of applications.

Claims

1. A magnetic material eddy current magnetic field measurement system, characterized in that: It includes a magnetic field measuring device and a corresponding magnetic field measuring method; The magnetic field measurement device includes: n measuring magnetic sensors disposed below the magnetic material, used to measure a first magnetic field value, a second magnetic field value or a third magnetic field value of the real-time magnetic field of the magnetic material, wherein the first magnetic field value includes the sum of the magnetic field values ​​of the earth's magnetic field and the induced magnetic field of the magnetic material under the earth's magnetic field; a magnetic field excitation coil, which surrounds the outside of the center point between the magnetic material and the n measuring magnetic sensors, generates a uniform excitation coil magnetic field and an induced magnetic field of the magnetic material under the excitation coil magnetic field when a constant current is passed through it, and generates an additional eddy current magnetic field when a variable current is passed through it, the second magnetic field value includes the excitation coil magnetic field and the induced magnetic field of the magnetic material under the excitation coil magnetic field, and the third magnetic field value includes the excitation coil magnetic field, the induced magnetic field of the magnetic material under the excitation coil magnetic field, and the eddy current magnetic field; A power supply, connected to the magnetic field excitation coil, for providing a constant current to the magnetic field excitation coil to generate the magnetic field of the excitation coil and the induced magnetic field of the magnetic material under the magnetic field of the excitation coil, or providing a changing current with a periodic change law to generate the magnetic field of the excitation coil and the induced magnetic field and eddy current magnetic field of the magnetic material under the magnetic field of the excitation coil; A data acquisition module is connected to the power supply and the n measuring magnetic sensors, respectively, and is used to obtain a constant current signal or a changing current signal corresponding to the constant current or the changing current of the power supply, and a first electrical signal, a second electrical signal or a third signal having a first magnetic field value, a second magnetic field value or a third magnetic field value, and convert the first electrical signal, the second electrical signal or the third signal into a first magnetic field signal, a second magnetic field signal or a third magnetic field signal; A background magnetic sensor is connected to the data acquisition module, measures the fourth magnetic field value of the earth's magnetic field and converts it into a fourth magnetic field signal and transmits it to the data acquisition module; an industrial computer, connected to the data acquisition module and the power supply, respectively, for obtaining a constant current signal or a variable current signal, a fourth magnetic field signal, and a first magnetic field signal, a second magnetic field signal, or a third magnetic field signal from the data acquisition module to perform eddy current magnetic field calculation, and controlling the power supply switch to energize the magnetic field excitation coil; The magnetic field measuring method corresponding to the magnetic field measuring device comprises the following steps: Step 1: The industrial computer controls the power supply to be in a turned-off state. At this time, the magnetic field measuring device is not powered on. The data acquisition module obtains electrical signals having a first magnetic field value and a fourth magnetic field value from n measuring magnetic sensors and a background magnetic sensor in real time, converts them into a first magnetic field signal and a fourth magnetic field signal, and transmits them to the industrial computer. The industrial computer calculates the change value of the first magnetic field value and the change value of the fourth magnetic field value, respectively, and adjusts the difference between the change value of the first magnetic field value and the change value of the fourth magnetic field value to zero, thereby achieving zero adjustment of the magnetic field measuring device, thereby eliminating interference from the earth's magnetic field. Step 2: The industrial computer controls the power supply to be turned on and passes a constant current. At this time, the magnetic field measuring device is powered on. The data acquisition module obtains the electrical signal with the second magnetic field value from the n measuring magnetic sensors, converts it into a second magnetic field signal, and obtains a constant current signal from the power supply, and transmits the second magnetic field signal and the constant current signal to the industrial computer; Step 3: The industrial computer analyzes the second magnetic field signal and the constant current signal to obtain a second magnetic field value and a constant current value, and determines the proportionality coefficient according to the proportionality coefficient formula; Step 4: The industrial computer controls the power supply to be turned on and passes a changing current. At this time, the magnetic field measuring device is powered on. The data acquisition module obtains the electrical signal with the third magnetic field value from the n measuring magnetic sensors, converts it into a third magnetic field signal, and obtains the changing current signal from the power supply. The signal is transmitted to the industrial computer for analysis to obtain the third magnetic field value and the changing current value. The eddy current magnetic field is determined according to the eddy current magnetic field value calculation formula combined with the proportional coefficient.

2. A magnetic material eddy current magnetic field measurement system as claimed in claim 1, characterized in that: The number of n measuring magnetic sensors, the spacing between the measuring magnetic sensors, and the distance between the measuring magnetic sensors and the magnetic material are determined according to the size of the magnetic material.

3. The eddy current magnetic field measurement system of a magnetic material as claimed in claim 1, characterized in that: The proportionality coefficient formula is as follows: B x =k1 I B ix =k2·I B1=B x +B ix =(k1+k2) I=K I Where I is the constant current value, B x is the value of the magnetic field of the excitation coil in the second magnetic field value, k1 is the ratio of the value of the magnetic field of the excitation coil to the constant current value; B ix is the induced magnetic field of the magnetic material under the magnetic field of the excitation coil, k2 is the ratio of the induced magnetic field of the magnetic material under the magnetic field of the excitation coil to the constant current value, B1 is the second magnetic field value, and K is the proportional coefficient.

4. A magnetic material eddy current magnetic field measurement system as claimed in claim 3, characterized in that: The eddy current magnetic field value calculation formula is as follows: B w =B-(B x +B ix )=B-K·I i Among them, B w is the value of the eddy current magnetic field in the third magnetic field value, B is the third magnetic field value, I i is the changing current value.

5. The eddy current magnetic field measurement system of magnetic materials according to claim 1, characterized in that: The varying current includes a current with a sinusoidal and / or ramp waveform.

6. A magnetic material eddy current magnetic field measurement system as claimed in claim 5, characterized in that: The uniformity of the magnetic field generated by the magnetic field excitation coil is between [95%, 100%].

7. A magnetic material eddy current magnetic field measurement system as claimed in claim 6, characterized in that: The time drift of the measuring magnetic sensor is between [0nT, 2nT].

8. The eddy current magnetic field measurement system of magnetic materials as claimed in claim 7, characterized in that: The fluctuation range of the constant current is between [-0.001, 0.001].

9. The eddy current magnetic field measurement system of magnetic materials according to claim 1, characterized in that: The first magnetic field value, the second magnetic field value and the third magnetic field value all include a fixed magnetic field of a magnetic material.

10. The eddy current magnetic field measurement system of magnetic materials according to claim 1, characterized in that: A flow divider is provided inside the data acquisition module.

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