A kind of detecting coil calibration device and method

Abstract

This invention relates to a probe coil calibration device and method. The device includes a DC power supply, a magnet, a probe coil, and a data acquisition and analysis system. The positive and negative terminals of the DC power supply are connected to the two ends of the magnet, respectively, to output DC current to power the magnet. It also includes a coil support, comprising a column and a coil tray. The probe coil to be calibrated is placed on the coil tray, positioned precisely at the center of the magnet's magnetic field. The two ends of the probe coil are connected to the input of the data acquisition and analysis system via coaxial cables. The magnet is a resistive magnet or a superconducting magnet, consisting of an internal conductive coil and an external container with a room-temperature aperture in the center. This probe coil calibration device is simple and convenient to operate, enabling rapid and accurate calibration of probe coils.

Description

Technical Field

[0001] This invention relates to the field of measurement and calibration technology, and in particular to an apparatus and method for calibrating and exchanging a probe coil. Background Technology

[0002] Probe coils are commonly used instruments in many scientific experiments and research, such as magnetic field measurement and magnetic testing. The coil parameter NS is a key parameter determining whether a probe coil can achieve accurate measurements, where N is the number of turns and S is the effective area enclosed by the coil.

[0003] Due to differences in coil winding processes, the NS parameters calculated based on coil dimensions are not accurate. To achieve accurate measurement, the NS parameters of the coil must be calibrated and adjusted.

[0004] Currently, some overseas detector coil suppliers offer two types of detector coils: one is a coil that has not been calibrated for its NS value; the other is a coil that has been calibrated and verified. The latter is significantly more expensive than the former.

[0005] According to IEEE standards, there are two methods for calibrating magnetic field probes in the time domain: 1) Compare the field strength value measured by the calibrated magnetic field probe with the measured value of the magnetic field probe to be calibrated; 2) Measure the field strength value of the magnetic field probe to be calibrated in a known or accurately calculated reference field and compare the measured field strength value with the known or accurately calculated value.

[0006] A probe coil is a type of magnetic field probe, and its calibration should conform to the aforementioned standards. However, it differs from some probes that measure steady-state magnetic fields because it is based on the principle of electromagnetic induction and can only measure changing magnetic fields. This makes its calibration more difficult compared to other types of magnetic field probes. Currently, the common practice for calibrating probe coil parameters is to place the probe coil in a relatively constant magnetic field and design a complex motor drive and support mechanism. By controlling the motor, the probe coil moves at a constant speed in the magnetic field, and standard instruments such as a fluxmeter are used to measure the change in magnetic flux in the probe coil. Then, based on the measurement data, the coil's N / S parameters are further calculated. Summary of the Invention

[0007] To calibrate and standardize detection coils and achieve precise measurement, this invention overcomes the shortcomings of existing detection coil calibration methods and devices, such as complex operation and insufficient accuracy. It provides a device and method for calibrating and standardizing detection coils, which is simple and convenient to operate, has high measurement accuracy, and can achieve rapid and accurate calibration and standardization of detection coils.

[0008] To achieve the above functions, the present invention adopts the following technical solution:

[0009] A method and apparatus for calibrating a detection coil, comprising a high-precision DC power supply, a magnet, a coil support, a detection coil, a coaxial cable, and a data acquisition and analysis system;

[0010] The high-precision DC power supply has its positive and negative output terminals connected to the two ends of the magnet, respectively, and can output DC current to power the magnet. The coil support consists of a column and a coil tray. The probe coil to be calibrated is placed on the coil tray, and the probe coil is located at the center of the magnetic field of the magnet. The two ends of the probe coil are connected to the input end of the acquisition and calculation analysis system by coaxial cables.

[0011] The high-precision DC power supply is a controllable current source that can rise, fall, and operate stably according to the set target current value and current rate.

[0012] The magnet is a resistive magnet or a superconducting magnet, consisting of an internal conductive coil and an external container with a room temperature aperture in the middle. For a well-designed magnet, the magnetic field strength it generates is linearly related to the current flowing through it.

[0013] Prior to calibration, the relationship between the magnetic field strength and the current of the magnet (i.e., the magnetic system number) had been precisely measured by nuclear magnetic resonance.

[0014] Furthermore, the coil support is made of non-magnetic material and consists of a column and a coil tray. One end of the column is fixed to the ground, and the other end is fixed to the coil tray, on which the detection coil is placed.

[0015] Furthermore, the length of the bracket is such that when the detection coil calibration and alignment device of the present invention is calibrating the detection coil, the detection coil is positioned precisely at the center of the magnetic field of the magnet.

[0016] Furthermore, the bracket can be configured as a telescopic structure with adjustable length to meet the calibration requirements of the detection coil when the center positions of magnets of different specifications differ.

[0017] Furthermore, the detection coil is a calibration device, made of N turns (N≥1) of coil, fixed on the coil tray of the bracket, and the two ends of the detection coil are connected to one end of the coaxial cable, and the other end of the coaxial cable is connected to the input end of the acquisition and calculation analysis system.

[0018] Furthermore, the acquisition and analysis system consists of a data acquisition card, a digital filter, coil parameter calculation and result display, as well as a processor and hardware and software units. The input of the data acquisition card is connected to the output of the coaxial cable, which is used to acquire the induced voltage signal generated on the detection and measurement coil. The sampling rate of the data acquisition card should meet the requirements of the Niguet sampling theorem.

[0019] The digital filter is implemented using software to filter the induced voltage signal output by the detection coil, filtering out AC signals other than the DC component.

[0020] The coil parameter calculation and result display unit can perform real-time calculation and processing on the output data of the digital filter to obtain the calculation result of the coil parameter NS, and display the calculation result.

[0021] The data acquisition and analysis system can be a regular computer or a microcomputer, or it can be an independent control chassis that includes hardware and software units such as the data acquisition card, processor, and digital integrator.

[0022] Furthermore, the processor and hardware / software units include, but are not limited to, the CPU, motherboard, keyboard, memory, hard disk, operating system, computer application software, etc. in a computer, and are a collective term for all hardware and software that support the operation of data acquisition cards, digital filters, coil parameter calculation results, and display units.

[0023] On the other hand, the principle of calibrating the detection coil in this invention is explained as follows:

[0024] Let the rate of rapid current rise be k, and the number of magnetic systems be a (T / A), then the output waveform during the current rise phase is as follows:

[0025] I=kt+I1sin(ω1t)+I2sin(ω2t)+I3sin(ω3t)+…

[0026] Where kt is the DC component, and I1, I2, I3... are the peak values ​​of the current ripple at each frequency.

[0027] It should be noted that the magnetic field strength generated by a magnet has a strict linear relationship with the current passing through it (B = aI). The magnetic system number 'a' is a key parameter for each magnet in a steady-state strong magnetic field. It has been obtained using standard nuclear magnetic resonance (NMR) measuring instruments (i.e., the value of the magnetic system number 'a' for each magnet is known and can be accurately measured, with units of Tesla / Ampere). The NMR frequency is proportional to the magnetic field strength. NMR technology is a recognized precision magnetic field measurement technique.

[0028] The magnetic field strength generated by the output current at the center of the magnet is:

[0029] B=aI=a·[kt+I1sin(ω1t)+I2sin(ω2t)+I3sin(ω3t)+…];

[0030] When the detection coil is placed at the center of the magnetic field of the magnet, according to Faraday's law of electromagnetic induction, an induced electromotive force will be generated in the detection coil, the magnitude of which is:

[0031]

[0032] Where NS is the effective number of turns area of ​​the coil, which is also the parameter value of the detection coil that needs to be calibrated;

[0033] After performing a digital high-pass filter on the induced voltage u output by the detection coil to remove the AC component, the DC component can be obtained as follows:

[0034] U0 = NSak

[0035] The DC component U0 obtained by digitally high-pass filtering the induced voltage output by the detection coil, divided by ak, yields the parameter values ​​of the detection coil:

[0036]

[0037] The present invention provides a detection coil calibration device, which employs the following calibration method:

[0038] Step 1: Prepare for calibration: ① Connect the positive and negative output terminals of the high-precision DC power supply to the current input terminal of the magnet to be used; ② Install and fix the probe coil to be calibrated on the coil tray of the bracket, connect the two ends of the probe coil to one end of the coaxial cable, adjust the length of the bracket, and place the probe coil at the center of the magnetic field of the magnet; ③ Connect the other end of the coaxial cable to the input terminal of the data acquisition card in the acquisition and analysis system.

[0039] Step 2: Power on the data acquisition and analysis system, and input the magnetic system number a (T / A) of the magnet used in this calibration, and the current rise rate or current fall rate k to be used by the high-precision power supply.

[0040] Step 3: Set the target current value and current rise rate (or current fall rate) of the high-precision DC power supply, and click "Run" to start the power supply's excitation (or demagnetization) operation.

[0041] Step 4: Following Step 3, run the "Acquisition and Calculation Analysis System" to begin collecting the output data of the detection coil.

[0042] Step 5: The acquisition and analysis system acquires and high-pass filters the output data of the detection coil to obtain the DC component U0 of the induced voltage output generated by the detection coil. The analysis system divides U0 by ak to obtain the coil parameters NS of the detection coil to be calibrated and displays them on the system.

[0043] The present invention discloses a method for calibrating a detection coil. It utilizes the known strict linear relationship between the magnetic field strength of a magnet and its power supply current. By designing the output current of the power supply to rise or fall rapidly at a fixed rate and measuring the output voltage of the detection coil, the parameters of the detection coil can be calculated, thereby achieving accurate calibration and standardization of the detection coil. Compared to existing calibration and standardization methods, which require complex motor drive and support mechanisms and control the motor to make the probe coil move at a constant speed in the magnetic field, the programmable DC power supply designed in this invention not only makes it easier to achieve rapid rise or fall of the output current, but also achieves a much more precise rate of rise and fall compared to the rate of constant motion of the coil in existing technologies. Furthermore, existing calibration and standardization methods require a uniform magnetic field within the movement area of ​​the probe coil. The larger the area of ​​coil movement (to obtain a higher output voltage and more accurate measurement results, the rate of uniform motion of the coil must be increased, and consequently, the area of ​​coil movement becomes larger), the larger the required uniform magnetic field area becomes. We know that achieving a large uniform magnetic field is difficult; currently, artificially designed magnetic field strengths exhibit a gradient distribution in space, which inevitably affects the accuracy of the measurement results. In this invention, the probe coil only needs to be placed at the center of the magnet and remain stationary, eliminating the need for a large uniform magnetic field area. The magnet's power supply current has a strictly linear relationship with its magnetic field strength. Therefore, the calibration and standardization method described in this invention is not only easier to implement but also offers higher measurement accuracy. In summary, the detection coil calibration device and method described in this invention can accurately calibrate and standardize the coil parameter values ​​of various detection coils. The device not only has a simple structure and is easy to operate, but also has higher measurement accuracy and a high degree of automation in measurement and calibration, enabling rapid and accurate calibration and standardization of detection coils. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of a method and device for calibrating a detection coil. Detailed Implementation

[0045] The present invention will be further described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] See Figure 1 A detection coil calibration device comprises a high-precision DC power supply 1, a magnet 2, a coil support 4-5, a detection coil 3, a coaxial cable 6, and an acquisition and calculation analysis system 7;

[0047] The positive and negative output terminals of the high-precision DC power supply 1 are respectively connected to the two ends of the magnet, and can output DC current to power the magnet 2; the coil support consists of a column 4 and a coil tray 5, the calibrated detection coil 3 is placed on the coil tray, the detection coil is located at the center of the magnetic field of the magnet 2, and the two ends of the detection coil are connected to the input end of the acquisition and calculation analysis system 7 by a coaxial cable 6.

[0048] Specifically, the high-precision DC power supply is a controllable current source that can rise, fall, and operate stably according to the set target current value and current rate.

[0049] The magnet is a resistive magnet or a superconducting magnet, consisting of an internal conductive coil and an external container with a room temperature aperture in the middle. The magnet is not "solid" but "hollow" in the middle. The magnetic field is strongest at the center and has the highest spatial uniformity. It is used to place experimental samples, measuring probes, etc. For a well-designed magnet, the magnetic field strength it generates is linearly related to the current flowing through it.

[0050] Prior to calibration, the relationship between the magnetic field strength and the current of the magnet (i.e., the magnetic system number) had been precisely measured by nuclear magnetic resonance.

[0051] The coil support is made of non-magnetic material and consists of a column and a coil tray. One end of the column is fixed to the ground and the other end is fixed to the coil tray, on which the detection coil is placed.

[0052] The length of the bracket is such that, when calibrating the detection coil, the detection coil is positioned precisely at the center of the magnetic field of the magnet; the magnetic field strength inside the magnet is gradient-distributed, with the strongest magnetic field at the center.

[0053] The bracket can be configured as a telescopic structure with adjustable length to meet the calibration requirements of the detection coil when the center positions of magnets of different specifications differ.

[0054] The probe coil is the device being calibrated. It is made of N turns (N≥1) of coil and fixed on the coil tray of the bracket. Both ends of the probe coil are connected to one end of the coaxial cable, and the other end of the coaxial cable is connected to the input end of the acquisition and calculation analysis system.

[0055] The acquisition and analysis system 7 consists of a data acquisition card 71, a digital filter 72, a coil parameter calculation and result display 73, and a processor and hardware and software 74. The input of the data acquisition card is connected to the output of the coaxial cable and is used to acquire the induced voltage signal generated on the detection and measurement coil. The sampling rate of the data acquisition card should meet the requirements of the Niguet sampling theorem.

[0056] The digital filter is implemented using software to filter the induced voltage signal output by the detection coil, filtering out AC signals other than the DC component.

[0057] The coil parameter calculation and result display unit can perform real-time calculation and processing on the output data of the digital filter to obtain the calculation result of the coil parameter NS, and display the calculation result.

[0058] The data acquisition and analysis system can be a regular computer or a microcomputer, or it can be an independent control chassis that includes hardware and software units such as the data acquisition card, processor, and digital integrator.

[0059] The processor and hardware / software units include, but are not limited to, the CPU, motherboard, keyboard, memory, hard disk, operating system, and computer application software in a computer, and are a collective term for all hardware and software that support the operation of data acquisition cards, digital filters, coil parameter calculation results, and display units.

[0060] The principle of calibrating the detection coil in this embodiment of the invention is explained as follows:

[0061] Let the rate of rapid current rise be k, and the number of magnetic systems be a (T / A), then the output waveform during the current rise phase is as follows:

[0062] I=kt+I1sin(ω1t)+I2sin(ω2t)+I3sin(ω3t)+…

[0063] Where kt is the DC component, and I1, I2, I3... are the peak values ​​of the current ripple at each frequency.

[0064] It should be noted that the magnetic field strength generated by a magnet has a strict linear relationship with the current passing through it (B = aI). The magnetic system number 'a' is a key parameter for each magnet in a steady-state strong magnetic field. It has been obtained using standard nuclear magnetic resonance (NMR) measuring instruments (i.e., the value of the magnetic system number 'a' for each magnet is known and can be accurately measured, with units of Tesla / Ampere). The NMR frequency is proportional to the magnetic field strength. NMR technology is a recognized precision magnetic field measurement technique.

[0065] The magnetic field strength generated by the output current at the center of the magnet is:

[0066] B=aI=a·[kt+I1sin(ω1t)+I2sin(ω2t)+I3sin(ω3t)+…];

[0067] When the detection coil is placed at the center of the magnetic field of the magnet, according to Faraday's law of electromagnetic induction, an induced electromotive force will be generated in the detection coil, the magnitude of which is:

[0068]

[0069] Where NS is the effective number of turns area of ​​the coil, which is also the parameter value of the detection coil that needs to be calibrated;

[0070] After performing a digital high-pass filter on the induced voltage u output by the detection coil to remove the AC component, the DC component can be obtained as follows:

[0071] U0 = NSak

[0072] The DC component U0 obtained by digitally high-pass filtering the induced voltage output by the detection coil, divided by ak, yields the parameter values ​​of the detection coil:

[0073]

[0074] The calibration device for a detection coil according to an embodiment of the present invention employs the following calibration method:

[0075] Step 1: Prepare for calibration: ① Connect the positive and negative output terminals of the high-precision DC power supply to the current input terminal of the magnet to be used; ② Install and fix the probe coil to be calibrated on the coil tray of the bracket, connect the two ends of the probe coil to one end of the coaxial cable, adjust the length of the bracket, and place the probe coil at the center of the magnetic field of the magnet; ③ Connect the other end of the coaxial cable to the input terminal of the data acquisition card in the acquisition and analysis system.

[0076] Step 2: Power on the data acquisition and analysis system, and input the magnetic system number a (T / A) of the magnet used in this calibration, and the current rise rate or current fall rate k to be used by the high-precision power supply.

[0077] Step 3: Set the target current value and current rise rate (or current fall rate) of the high-precision DC power supply, and click "Run" to start the power supply's excitation (or demagnetization) operation.

[0078] Step 4: Following Step 3, run the "Acquisition and Calculation Analysis System" to begin collecting the output data of the detection coil.

[0079] Step 5: The acquisition and analysis system acquires and high-pass filters the output data of the detection coil to obtain the DC component U0 of the induced voltage output by the detection coil. The analysis system divides U0 by ak to obtain the coil parameters NS of the detection coil to be calibrated and displays them on the system.

[0080] In summary, the detection coil calibration method of the present invention utilizes the known strict linear relationship between the magnetic field strength of a magnet and its power supply current. By designing the output current of the power supply to rise or fall rapidly at a fixed rate and measuring the output voltage of the detection coil, the parameters of the detection coil can be calculated, thereby achieving accurate calibration and adjustment of the detection coil. Compared to existing calibration and standardization methods, which require complex motor drive and support mechanisms and control the motor to make the probe coil move at a constant speed in the magnetic field, the programmable DC power supply designed in this invention not only makes it easier to achieve rapid rise or fall of the output current, but also achieves a much more precise rate of rise and fall compared to the rate of constant motion of the coil in existing technologies. Furthermore, existing calibration and standardization methods require a uniform magnetic field within the movement area of ​​the probe coil. The larger the area of ​​coil movement (to obtain a higher output voltage and more accurate measurement results, the rate of uniform motion of the coil must be increased, and consequently, the area of ​​coil movement becomes larger), the larger the required uniform magnetic field area becomes. We know that achieving a large uniform magnetic field is difficult; currently, artificially designed magnetic field strengths exhibit a gradient distribution in space, which inevitably affects the accuracy of the measurement results. In this invention, the probe coil only needs to be placed at the center of the magnet and remain stationary, eliminating the need for a large uniform magnetic field area. The magnet's power supply current has a strictly linear relationship with its magnetic field strength. Therefore, the calibration and standardization method described in this invention is not only easier to implement but also offers higher measurement accuracy.

[0081] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A probe coil calibration device, characterized by: It includes a DC power supply, a magnet, a detection coil, and a data acquisition and analysis system. The positive and negative output terminals of the DC power supply are respectively connected to the two ends of the magnet, and it can output DC current to power the magnet. The DC power supply is a controllable current source, capable of rising, falling, and stabilizing according to a set target current value and current rate. It also includes a coil support, comprising a column and a coil tray. The calibrated probe coil is placed on the coil tray, positioned precisely at the center of the magnet's magnetic field. Both ends of the probe coil are connected to the input of the acquisition and analysis system via coaxial cables. The magnet is a resistive magnet or a superconducting magnet, consisting of an internal conductive coil and an external container with a room-temperature aperture in the middle. The acquisition and analysis system includes a data acquisition card, a digital filter, a coil parameter calculation and result display system, and a processor. The input of the data acquisition card is connected to the output of the coaxial cable, used to acquire the induced voltage signal generated on the probe coil. The sampling rate of the data acquisition card should meet the requirements of the Niguet sampling theorem. The digital filter uses software to filter the induced voltage signal output by the probe coil, removing AC signals other than the DC component. The coil parameter calculation and result display unit performs real-time calculation and processing on the output data of the digital filter to obtain the calculated coil parameter NS and displays the results.

2. The detection coil calibration device according to claim 1, characterized in that: The coil support is made of non-magnetic material and consists of a column and a coil tray. One end of the column is fixed to the ground and the other end is fixed to the coil tray, on which the detection coil is placed.

3. The detection coil calibration device according to claim 1, characterized in that: The length of the bracket is such that, when calibrating the detection coil, the detection coil is positioned precisely at the center of the magnet's magnetic field.

4. The detection coil calibration device according to claim 1, characterized in that: The bracket is designed as a telescopic structure with an adjustable length.

5. The detection coil calibration device according to claim 1, characterized in that: The detection coil is the device being calibrated. It is made of N turns of coil, where N≥1, and is fixed on the coil tray of the bracket. The two ends of the detection coil are connected to one end of a coaxial cable, and the other end of the coaxial cable is connected to the input end of the acquisition and calculation analysis system.

6. A method for calibrating a detection coil, using a detection coil calibration device as described in any one of claims 1-5, characterized in that: Includes the following steps, Step 1: Complete the preparations before calibration; Step 2: Power on the data acquisition and analysis system and input the magnetic series number of the magnet used in this calibration. (T / A), the rate of rise or fall of current used in power supply preparation. ; Step 3: Set the target current value, current rise rate, or current fall rate of the DC power supply, and click "Run" to start the power supply's excitation or demagnetization operation; Step 4: Following Step 3, run the "Acquisition and Calculation Analysis System" to begin collecting the output data from the detection coil; Step 5: Acquisition and Calculation Analysis The system acquires and high-pass filters the output data of the detection coil to obtain the DC component of the induced voltage output by the detection coil. The computational analysis system will Divide by The coil parameters of the probe coil to be calibrated can then be obtained. And display it on the system.

7. The method for calibrating a detection coil according to claim 6, characterized in that: Step 1: Complete the preparatory work before calibration. The specific steps are as follows: Connect the positive and negative output terminals of the DC power supply to the current input terminal of the magnet to be used; Install and fix the probe coil to be calibrated on the coil tray of the bracket, connect the two ends of the probe coil to one end of the coaxial cable, adjust the length of the bracket, and place the probe coil at the center of the magnetic field of the magnet. Connect the other end of the coaxial cable to the input terminal of the data acquisition card in the data acquisition and analysis system.

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