A high-temperature conductivity measurement system and method based on eddy current method

Abstract

This invention relates to the field of conductivity measurement technology, and more particularly to a high-temperature conductivity measurement system and method based on the eddy current method. The system includes a stage, a high-temperature eddy current probe, a moving device, a pyrometer, a laser heating subsystem, and a data measurement subsystem. The stage is used to place the sample to be measured. The high-temperature eddy current probe is used to receive an excitation signal and pick up the measurement signal. The moving device is used to move the high-temperature eddy current probe laterally above the sample. The laser heating subsystem emits a continuous laser in the near-infrared band to heat the sample. The data measurement subsystem generates a set of multi-frequency excitation signals to excite the high-temperature eddy current probe, determines the inductance changes corresponding to the multi-frequency excitation signals measured by the high-temperature eddy current probe at the same position above the sample, and calculates the conductivity of the sample based on the inductance changes. This invention enables accurate, non-contact measurement of the conductivity of materials under high-temperature conditions.

Description

Technical Field

[0001] This invention relates to the field of conductivity measurement technology, and in particular to a high-temperature conductivity measurement system and method based on the eddy current method. Background Technology

[0002] Electrical conductivity is an important material property and is affected by factors such as temperature. Aerospace and other applications often require the use of various carbon-based composite materials. Due to the specific application scenarios, to test material performance and obtain accurate conductivity measurements, it is necessary to simulate the ambient temperature of the material's application environment. Especially in high-temperature environments of several hundred or even thousands of degrees Celsius, the impact of temperature on material conductivity becomes significant.

[0003] Eddy current method is a method for measuring conductivity at room temperature, which can calculate conductivity based on the measured inductance and resistance data. However, because ambient temperature has a significant impact on resistance, high or ultra-high temperature interference can render the data measured by conventional eddy current method invalid, making it impossible to accurately measure the conductivity of materials in high-temperature environments. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] The technical problem to be solved by the present invention is to address the difficulty of accurately measuring the conductivity of conductive materials under high-temperature conditions using the eddy current method in the prior art.

[0006] (II) Technical Solution

[0007] To address the aforementioned technical problems, this invention provides a high-temperature conductivity measurement system based on the eddy current method, comprising:

[0008] The stage is used to hold the sample to be tested.

[0009] The high-temperature eddy current probe has an internal coil for receiving excitation signals and picking up measurement signals.

[0010] A moving device is used to move the high-temperature eddy current probe laterally above the sample being tested.

[0011] A pyrometer is used to monitor the temperature of a sample being tested.

[0012] The laser heating subsystem is used to emit a continuous laser in the near-infrared band to heat the sample under test from below through a heating hole opened on the stage.

[0013] A data measurement subsystem, connected to the high-temperature eddy current probe, is used to generate a set of multi-frequency excitation signals to excite the high-temperature eddy current probe, acquire the measurement signals picked up by the high-temperature eddy current probe, determine the inductance changes corresponding to the set of multi-frequency excitation signals measured by the high-temperature eddy current probe at the same position above the sample under test based on the measurement signals, and calculate the conductivity of the sample under test based on the inductance changes; wherein, the set of multi-frequency excitation signals includes at least three different frequencies of excitation signals, and the frequency difference between any two frequencies does not exceed a preset frequency difference threshold.

[0014] Optionally, the high-temperature eddy current probe is made of a high-temperature resistant material, and the outer shell has a hollow interlayer containing cooling oil.

[0015] Optionally, the coil is located at the detection end at the bottom of the high-temperature eddy current probe, and the wall thickness of the detection end does not exceed 1 mm.

[0016] Optionally, the moving device includes a slide rail, a slider, and a drive module; wherein,

[0017] The slide rail is located on one side of the platform;

[0018] The slider is disposed on the slide rail and is capable of moving along the slide rail;

[0019] The drive module is connected to the slider and is used to drive the slider to move;

[0020] The high-temperature eddy current probe is mounted on one side of the slider via a bracket and suspended above the sample being tested.

[0021] Optionally, the laser emitted by the laser heating subsystem forms a laser beam with a diameter of not less than 10 mm at the point of heating the sample under test, and the uniformity is not less than 90%.

[0022] Optionally, the set of multi-frequency excitation signals includes no more than five different frequency excitation signals.

[0023] Optionally, the preset frequency difference threshold value ranges from 5 to 10 kHz.

[0024] Optionally, the high-temperature conductivity measurement system further includes:

[0025] The control module is connected to the high-temperature eddy current probe, the pyrometer, the mobile device, the laser heating subsystem, and the data measurement subsystem, and is used to generate corresponding control commands and send them accordingly.

[0026] The present invention also provides a high-temperature conductivity measurement method based on the eddy current method, which is implemented using the high-temperature conductivity measurement system based on the eddy current method as described in any of the above claims, and includes the following steps:

[0027] Place the sample to be tested on the stage;

[0028] The laser heating subsystem emits a laser to heat the sample under test, and the temperature is monitored by a pyrometer to heat the sample to a preset temperature.

[0029] Set a set of operating parameters for a multi-frequency excitation signal, including the number of signals, signal frequency, excitation sequence, excitation duration, and excitation interval duration;

[0030] The high-temperature eddy current probe is moved by a moving device, so that the high-temperature eddy current probe is moved from a position away from the sample to above the sample. A set of multi-frequency excitation signals is generated according to the set working parameters to obtain the corresponding inductance data.

[0031] The high-temperature eddy current probe is moved to a position away from the sample being tested, and a set of multi-frequency excitation signals is generated again according to the set working parameters to obtain the corresponding inductance data.

[0032] Based on the acquired inductance data, the inductance change data corresponding to each frequency of excitation signal is obtained;

[0033] Based on the obtained inductance change data, the conductivity under the current temperature environment is calculated.

[0034] Optionally, the step of calculating the conductivity under the current temperature environment based on the obtained inductance change data includes:

[0035] For each of the two different excitation signals, based on the corresponding inductance change data, a system of equations is solved to obtain a conductivity value.

[0036] Based on all the obtained conductivity values, the conductivity under the current temperature environment is calculated by averaging them.

[0037] (III) Beneficial Effects

[0038] The above-described technical solution of the present invention has the following advantages:

[0039] This invention provides a high-temperature conductivity measurement system based on the eddy current method. The system uses a rapidly movable high-temperature eddy current probe to measure the inductance change corresponding to excitation signals at different frequencies, so as to calculate the conductivity under high-temperature conditions. At the same time, the system uses a continuous laser in the near-infrared band to heat the sample under test, which can provide a high-temperature or even ultra-high-temperature environment, realize non-contact rapid heating of the sample under test, and the laser heating method does not introduce electromagnetic interference, enabling accurate measurement.

[0040] This invention also provides a high-temperature conductivity measurement method based on eddy current method, which is suitable for non-contact measurement of the conductivity of conductive materials under high temperature or even ultra-high temperature conditions. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the eddy current method principle;

[0042] Figure 2 This is a schematic diagram of a high-temperature conductivity measurement system based on the eddy current method in an embodiment of the present invention;

[0043] Figure 3 This is a schematic diagram of the steps of a high-temperature conductivity measurement method based on eddy current method in an embodiment of the present invention.

[0044] In the figure: 1: Sample under test; 2: High-temperature eddy current probe; 3: Cooling device; 4: Pyrometer; 5: Motion controller; 6: Impedance analyzer; 7: Laser output module; 8: Control module. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. 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] As mentioned earlier, the electrical conductivity of a material is affected by temperature; therefore, to obtain accurate results, it is necessary to simulate the ambient temperature of the environment in which the material is applied during the measurement process. Eddy current testing (ECT) is a non-destructive testing technique based on electromagnetic induction. Figure 1 As shown, when an alternating excitation signal is applied to the coil and placed near a conductive material, an alternating electromagnetic field, referred to as the primary field, is generated in the space surrounding the coil. According to Faraday's law of electromagnetic induction, under the influence of the primary field, an induced current (eddy current) is generated in the conductive material below the coil. This eddy current generates an alternating electromagnetic field in the opposite direction to the primary field, referred to as the secondary field. The generation of the secondary field partially cancels out the primary field, thus causing a change in the coil's impedance. When detecting conductive materials with different conductivities, the magnitude of the generated eddy currents varies, resulting in different effects on the detection coil's impedance. Therefore, by measuring the change in coil impedance and then using the coil impedance change model, the conductivity of the conductive material can be deduced.

[0047] Conventional eddy current conductivity measurements typically calculate conductivity by picking up changes in the resistance and inductance of a coil at a single frequency. However, the coil resistance is highly temperature-dependent and easily affected by temperature interference. Therefore, conventional eddy current methods are only suitable for measuring conductivity at room temperature and are not applicable to high-temperature conductivity measurements. Furthermore, conductive samples undergo expansion and sublimation during heating, which alters the distance (lift-off) between the eddy current probe and the sample. Overcoming the impact of lift-off changes during measurement is a key challenge in high-temperature conductivity measurements.

[0048] In view of this, the present invention provides a conductivity measurement system and method applicable to high temperature and ultra-high temperature conditions, which can realize non-contact and accurate measurement of the conductivity of conductive materials under high temperature conditions.

[0049] like Figure 2 As shown, the high-temperature conductivity measurement system based on the eddy current method (hereinafter referred to as the system) provided in this embodiment of the invention includes: a stage, a high-temperature eddy current probe 2, a moving device, a pyrometer 4, a laser heating subsystem, and a data measurement subsystem; specifically:

[0050] The stage is used to place the sample 1 to be tested; the high-temperature eddy current probe 2 has a coil inside, the coil is connected to the excitation source, and the high-temperature eddy current probe 2 is used to pass in the excitation signal and pick up the measurement signal; the moving device is used to drive the high-temperature eddy current probe 2 to move laterally above the sample 1 to be tested; the pyrometer 4 is used to monitor the temperature of the sample 1 to be tested.

[0051] The laser heating subsystem is used to emit a continuous laser in the near-infrared band to heat the sample 1 under test from below through the heating hole opened on the stage.

[0052] The data measurement subsystem is connected to the high-temperature eddy current probe 2 and is used to generate a set of multi-frequency excitation signals to excite the high-temperature eddy current probe 2, acquire the measurement signals picked up by the high-temperature eddy current probe 2, and determine the inductance changes corresponding to the set of multi-frequency excitation signals measured by the high-temperature eddy current probe 2 at the same position above the sample 1. That is, at the same position above the sample 1, different frequencies of excitation signals are switched in a time-division manner to obtain the corresponding inductance data, and then at the same position away from the sample 1, the same set of multi-frequency excitation signals is switched in a time-division manner to obtain the corresponding inductance data. The difference is taken to obtain the inductance change corresponding to each frequency of excitation signal, and the conductivity of the sample 1 is calculated based on the inductance change. The set of multi-frequency excitation signals includes at least three different frequencies of excitation signals, and the frequency difference between any two frequencies does not exceed a preset frequency difference threshold. The directional terms "above" and "below" refer to relative to the ground.

[0053] The system provided by this invention only needs to measure inductance data, without measuring resistance data. It utilizes the inductance changes corresponding to different frequency excitation signals to eliminate the influence of lift-off changes and calculate the conductivity of the sample under test. The high temperature environment has little impact on the inductance data, and the inductance data corresponding to different frequencies are measured at the same location, which can achieve more accurate conductivity measurement results.

[0054] The system uses a moving device to move the high-temperature eddy current probe 2 above the sample 1 being tested. The moving speed and dwell time are adjustable. By moving quickly and dwelling briefly, the influence of thermal radiation on the high-temperature eddy current probe 2 itself can be effectively reduced, which is also conducive to achieving accurate measurement.

[0055] Furthermore, this system employs a near-infrared continuous laser to heat the sample, enabling high-temperature and ultra-high-temperature measurements. Traditional high-temperature conductivity measurements, to achieve temperatures above 1000°C, typically utilize resistance heating, electromagnetic induction, and radiation heating. Radiation heating primarily relies on graphite furnaces and muffle furnaces, but the maximum heating temperature cannot exceed 1700°C and requires an inert gas environment, making high-temperature conductivity measurements impossible in oxygen-rich environments. Resistance heating and electromagnetic induction heating apply current and magnetic fields to the sample, causing electromagnetic interference and affecting normal measurements. Therefore, this invention proposes a conductivity measurement system using a high-power continuous laser for rapid, non-contact, and electromagnetically interference-free heating, enabling rapid heating and measurement of samples with high thermal conductivity above 2000°C.

[0056] Optionally, the high-temperature eddy current probe 2 is made of high-temperature resistant material, and the outer shell has a hollow interlayer containing cooling oil.

[0057] The high-temperature eddy current probe 2 (hereinafter referred to as the probe) can be made of high-temperature resistant ceramic material, preferably porous zirconia with low thermal conductivity. Ceramic material possesses high-temperature resistance, remaining stable at hundreds or even thousands of degrees Celsius, and is an insulating material that will not introduce electromagnetic interference. Cooling oil has cooling and protective functions, and also provides insulation, making it suitable for the high-temperature eddy current probe 2.

[0058] Preferably, the high-temperature conductivity measurement system further includes a cooling device 3, which includes a circulating pump connected to the jacket to achieve circulating cooling oil and improve the cooling protection effect on the high-temperature eddy current probe 2. By setting the operating parameters of the circulating pump, the temperature of the high-temperature eddy current probe 2 can be controlled.

[0059] Optionally, the coil is located at the detection end at the bottom of the high-temperature eddy current probe 2, and the wall thickness of the detection end does not exceed 1 mm, more preferably 0.5 mm. With cooling oil for temperature protection, the wall of the detection end of the high-temperature eddy current probe 2 can be as thin as possible to improve the eddy current intensity and obtain more accurate detection results.

[0060] Optionally, the moving device includes a slide rail, a slider, and a drive module; wherein the slide rail is disposed on one side of the stage; the slider is disposed on the slide rail and is capable of moving along the slide rail; the drive module is connected to the slider and is used to drive the slider to move; the high-temperature eddy current probe 2 is disposed on one side of the slider via a bracket and suspended above the sample 1 to achieve lateral movement above the sample 1.

[0061] The above embodiment implements a moving device through a slide rail, a slider, and a drive module, enabling the high-temperature eddy current probe 2 to quickly sweep over the sample 1 being measured. This rapid movement reduces the impact of high temperature on the probe and interference with the measurement results. The drive module may include a motor and a motion controller 5. The motor moves the slider, and the motion controller 5 adjusts the movement parameters, with the control quantity being the slider's displacement X.

[0062] Optionally, both the slide rail and the slider are made of high-temperature resistant insulating material to avoid deformation caused by high temperature, which would interfere with the rapid movement of the high-temperature eddy current probe 2.

[0063] Preferably, the slider moves at a speed of not less than 900 mm / s to reduce the impact of high-temperature radiation.

[0064] Optionally, the laser emitted by the laser heating subsystem forms a laser beam with a diameter of not less than 10 mm at the heated sample 1, and the uniformity is not less than 90%.

[0065] Optionally, a laser heating subsystem includes:

[0066] Laser output module 7 is used to provide laser light;

[0067] The beam shaping module is used to perform two optical shapings on the laser output by the laser output module 7, one in the fast axis direction and the other in the slow axis direction.

[0068] The beam combining module is used to combine the shaped laser beam;

[0069] A beam expander module is used to expand the laser output from the beam combiner module to reduce the laser divergence angle.

[0070] A focusing module is used to focus the laser output from the beam expander module and couple it into the optical fiber;

[0071] The collimation module, connected to the convergence module via optical fiber, is used to irradiate the sample 1 being tested with the laser transmitted through the optical fiber.

[0072] In the above embodiments, the laser output module 7 of the laser heating subsystem can employ a high-power semiconductor laser or a high-power fiber-coupled laser, etc., to obtain a laser beam with a sufficiently large area and high uniformity after shaping, beam expansion, and other processing. High-energy laser beam heating has the characteristics of high directionality and fast heating rate. In a specific embodiment, the laser output module 7 of the present invention can provide a maximum of approximately 3 × 10⁻⁶ Ω·cm. 7 W / m 2 The high-energy laser beam can achieve a maximum heating rate of approximately 1000℃ / s for carbon-based composite materials. The collimating lens in the collimation module has a diameter of 20mm (Φ20mm), enabling uniform heating of a 20mm sample. Verification shows that this method can reach an upper limit of approximately 2200℃ for heating carbon-based composite materials. Given the high thermal conductivity of carbon / carbon materials, a preliminary estimate suggests that a 20mm laser beam can heat samples smaller than 40mm to approximately 1300℃. The heating area of ​​this system is determined by the collimating lens, while the heating temperature is determined by the laser power (energy density). Therefore, by replacing the collimating lens with a larger diameter one and increasing the laser power, uniform heating of larger samples can be achieved.

[0073] Optionally, the sidewalls of the sample 1 under test are encapsulated with thermal insulation material, which helps to achieve uniform heating.

[0074] Optionally, the pyrometer 4 can be a dual-color infrared thermometer, and the measured value is temperature T.

[0075] Optionally, the data measurement subsystem includes an impedance analyzer 6. The impedance analyzer 6 includes an excitation source. In use, the impedance analyzer 6 is connected to the coil inside the high-temperature eddy current probe 2, and the coil inductance data can be quickly detected through the impedance analyzer 6.

[0076] Optionally, the set of multi-frequency excitation signals includes no more than five different frequency excitation signals to avoid the probe remaining above the sample 1 for a long time when the excitation signal is generated in a time-division manner, thereby reducing the impact of high-temperature radiation on the coil and measurement data.

[0077] Optionally, the preset frequency difference threshold value ranges from 5 to 10 kHz.

[0078] In the above embodiment, the frequency difference between the various excitation signals of different frequencies included in the set of multi-frequency excitation signals does not exceed 10kHz, thereby reducing the interference introduced by different skin depths on the solution of conductivity due to excessive frequency difference.

[0079] Optionally, the system further includes a control module 8, which is connected to the high-temperature eddy current probe 2, the pyrometer 4, the mobile device, the laser heating subsystem, and the data measurement subsystem, and is used to generate and send corresponding control commands.

[0080] In the above embodiment, the heating power of the laser heating subsystem can be set by the control module 8, the temperature of the sample 1 under test can be obtained, and the high-temperature eddy current probe 2 can be moved above or away from the sample 1 under test by the moving device. This allows the high-temperature eddy current probe 2 to generate excitation signals of different frequencies at the same position in a time-division manner, and to obtain the corresponding inductance data. Finally, based on the obtained inductance data, the conductivity of the sample 1 under the current temperature condition can be calculated. The control module 8 automatically sends excitation signal switching commands and obtains inductance data, resulting in high speed, short processing time, and automated control and measurement.

[0081] like Figure 3 As shown, the present invention also provides a high-temperature conductivity measurement method based on the eddy current method, which is implemented using the high-temperature conductivity measurement system based on the eddy current method as described in any of the above embodiments, and specifically includes the following steps:

[0082] Step 300: Place the sample to be tested on the stage;

[0083] Step 302: The laser heating subsystem emits a laser to heat the sample under test, and the temperature is monitored by a pyrometer to heat the sample to a preset temperature.

[0084] Step 304: Set a set of operating parameters for a multi-frequency excitation signal, including the number of signals, signal frequency, excitation sequence, excitation duration, and excitation interval duration; wherein, the number of signals refers to the number of excitation signals of different frequencies used, the excitation sequence refers to the order in which different frequencies of excitation signals are switched in a time-division manner, the excitation duration refers to the duration of excitation by a single frequency excitation signal, and the excitation interval duration refers to the interval duration between two adjacent excitation signals.

[0085] Step 306: Move the high-temperature eddy current probe by moving the moving device, so that the high-temperature eddy current probe moves from a position away from the sample to above the sample. According to the set working parameters, generate a set of multi-frequency excitation signals through the data measurement subsystem to obtain the corresponding inductance data.

[0086] Step 308: Move the high-temperature eddy current probe by moving the moving device to a position away from the sample being tested. Then, according to the set working parameters, generate the same set of multi-frequency excitation signals as in step 306 through the data measurement subsystem to obtain the corresponding inductance data.

[0087] Step 310: Based on the acquired inductance data, obtain the inductance change data corresponding to each frequency of the excitation signal in a set of multi-frequency excitation signals;

[0088] Step 312: Based on the obtained inductance change data, calculate the conductivity under the current temperature environment.

[0089] Optionally, step 312 further includes:

[0090] For each of the two different excitation signals, based on the corresponding inductance change data, a system of equations is solved to obtain a conductivity value.

[0091] Based on all the obtained conductivity values, the conductivity under the current temperature environment is calculated by averaging them.

[0092] Alternatively, the relationship between inductance change and conductivity can be expressed as:

[0093]

[0094] Where, ΔL f (σ,h) represents the inductance change corresponding to an excitation signal with frequency f, σ represents the measured conductivity, h represents lift-off, N represents the number of coil turns, r1 and r2 represent the inner and outer diameters of the coil, respectively, μ0 represents the free permeability, δ represents the coil thickness, and ω represents the angular frequency corresponding to frequency f. J1(x) represents the Bessel function of the first kind, and α represents the integration variable. In step 312, when solving for the conductivity value, simultaneously solving the inductance changes corresponding to two different frequencies can eliminate the influence of lift-off h, thus obtaining the conductivity σ.

[0095] In one specific implementation, a set of multi-frequency excitation signals includes three excitation signals of different frequencies, f1, f2, and f3. Accordingly, in step 306, the high-temperature eddy current probe is moved from a position away from the sample to above the sample, sequentially generating the three excitation signals of different frequencies f1, f2, and f3, and acquiring the corresponding inductance data L1, L2, and L3. In step 308, the high-temperature eddy current probe is moved to a position away from the sample, sequentially generating the three excitation signals of different frequencies f1, f2, and f3, and acquiring the corresponding inductance data L1, L2, and L3. air1 L air2 and L air3 .

[0096] Step 310 obtains the inductance change data corresponding to each excitation signal frequency, that is, obtains the inductance change of the coil under three different excitation signals f1, f2 and f3. ΔL f2 (σ,h) and The expressions are as follows:

[0097]

[0098]

[0099]

[0100] Wherein, ω1, ω2 and ω3 represent the angular frequencies corresponding to f1, f2 and f3, respectively.

[0101] Step 312: For each of the two different excitation signals, solve for a conductivity value. That is, solve equations (1) and (2) simultaneously to obtain the first conductivity value σ1, equations (2) and (3) simultaneously to obtain the second conductivity value σ2, and equations (1) and (3) simultaneously to obtain the third conductivity value σ3. Finally, calculate the average to obtain the conductivity under the current temperature environment.

[0102] This invention uses the change in inductance of a coil to inversely determine conductivity. Simultaneously, three different excitation frequencies are used to excite the eddy current coil, and the inductance changes at each of the three frequencies are measured. By using the obtained inductance changes and treating lift-off as an unknown parameter, the conductivity can be further inversely determined. Therefore, this invention can overcome the adverse effects of mechanical vibration, expansion of the sample at high temperatures, and changes in lift-off caused by sublimation during the measurement process, and achieve rapid, non-contact, and accurate measurement of high-temperature conductivity.

[0103] Preferably, in step 306, the high-temperature eddy current probe is moved from a position away from the sample to above the sample at a speed of not less than 900 mm / s, generating a set of multi-frequency excitation signals, and the total time for acquiring the corresponding inductance data does not exceed 20 ms.

[0104] Preferably, in step 308, the high-temperature eddy current probe is moved to a position away from the sample being tested, and the moving speed is not less than 900 mm / s.

[0105] By using the above embodiments, the time that the probe is in close proximity to the sample being tested can be reduced, thus minimizing the impact of thermal radiation on the probe.

[0106] In summary, this invention provides a high-temperature conductivity measurement system and method based on the eddy current method. The system employs a rapidly movable high-temperature eddy current probe to measure the inductance changes corresponding to excitation signals at different frequencies, thereby calculating the conductivity under high-temperature conditions. The probe movement and excitation signal switching can both be achieved by the system, resulting in high efficiency and eliminating the need for manual operation. Simultaneously, the system uses a near-infrared continuous laser to heat the sample, providing a high-temperature or even ultra-high-temperature environment, enabling non-contact and rapid heating of the sample. Furthermore, laser heating does not introduce electromagnetic interference, allowing for accurate measurement. This method solves for the conductivity of conductive materials under high-temperature or even ultra-high-temperature conditions by simultaneously solving for the inductance changes corresponding to multiple frequency excitation signals. This overcomes the adverse effects of mechanical vibration, material expansion at high temperatures, and sublimation leading to changes in lift-off during measurement, achieving rapid, non-contact, and accurate measurement.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high temperature conductivity measurement system based on eddy current method, characterized in that, The system comprises: a sample stage for placing a sample to be measured; a high-temperature eddy current probe with a coil inside for passing in an excitation signal and picking up a measurement signal; a moving device for moving the high-temperature eddy current probe transversely above the sample to be measured; a pyrometer for monitoring the temperature of the sample to be measured; a laser heating subsystem for emitting continuous laser in near-infrared band to heat the sample to be measured from below through a heating hole opened on the sample stage; a data measurement subsystem connected with the high-temperature eddy current probe for generating a set of multi-frequency excitation signals to excite the high-temperature eddy current probe, acquiring the measurement signal picked up by the high-temperature eddy current probe, determining the inductance change corresponding to each of the set of multi-frequency excitation signals measured by the high-temperature eddy current probe at the same position above the sample to be measured based on the measurement signal, and calculating the electrical conductivity of the sample to be measured according to the inductance change; wherein the set of multi-frequency excitation signals comprises at least three excitation signals with different frequencies, and the frequency difference between any two frequencies does not exceed a preset frequency difference threshold.

2. The high-temperature electrical conductivity measurement system based on eddy current method according to claim 1, wherein: the high-temperature eddy current probe is made of high-temperature resistant material, and the shell is provided with a hollow interlayer, and the interlayer is provided with cooling oil.

3. The high-temperature electrical conductivity measurement system based on eddy current method according to claim 2, wherein: the coil is located at the detection end of the bottom of the high-temperature eddy current probe, and the wall thickness of the detection end is not more than 1 mm.

4. The high-temperature electrical conductivity measurement system based on eddy current method according to claim 1, wherein: the moving device comprises a sliding rail, a sliding block and a driving module; wherein, the sliding rail is arranged on one side of the sample stage; the sliding block is arranged on the sliding rail and can move along the sliding rail; the driving module is connected with the sliding block for driving the sliding block to move; the high-temperature eddy current probe is arranged on one side of the sliding block through a support and suspended above the sample to be measured.

5. The high-temperature electrical conductivity measurement system based on eddy current method according to claim 1, wherein: the laser emitted by the laser heating subsystem forms a laser beam with a diameter not less than 10 mm and a uniformity not less than 90% at the position of heating the sample to be measured.

6. The high-temperature electrical conductivity measurement system based on eddy current method according to claim 1, wherein: the set of multi-frequency excitation signals comprises no more than five excitation signals with different frequencies.

7. The high-temperature electrical conductivity measurement system based on eddy current method according to claim 1, wherein: the preset frequency difference threshold is in the range of 5-10 kHz.

8. The eddy current based high temperature conductivity measurement system of claim 1, wherein, Further comprising: a control module connected with the high-temperature eddy current probe, the pyrometer, the moving device, the laser heating subsystem and the data measurement subsystem for generating corresponding control instructions and sending correspondingly.

9. A method of high temperature conductivity measurement based on eddy current method, characterized by: The high-temperature electrical conductivity measurement system based on eddy current method is realized by adopting any one of claims 1-8, comprising the following steps: placing the sample to be measured on the sample stage; emitting laser by the laser heating subsystem to heat the sample to be measured, and monitoring the temperature by the pyrometer to heat the sample to be measured to a preset temperature; Set a group of working parameters of multi-frequency excitation signals, including the number of signals, signal frequency, excitation sequence, excitation duration and excitation interval duration; The high-temperature eddy current probe is moved by the moving device, and the high-temperature eddy current probe is moved from a position away from the measured sample to above the measured sample. A group of multi-frequency excitation signals are generated according to the set working parameters, and corresponding inductance data are obtained; The high-temperature eddy current probe is moved to a position away from the measured sample, and a group of multi-frequency excitation signals are generated again according to the set working parameters, and corresponding inductance data are obtained; Based on the obtained inductance data, the inductance change data corresponding to each frequency of the excitation signal is obtained; Based on the obtained inductance change data, the conductivity under the current temperature environment is solved.

10. The high-temperature conductivity measurement method based on the eddy current method according to claim 9, characterized in that: Based on the obtained inductance change data, the conductivity under the current temperature environment is solved, including: For each two different frequency excitation signals, based on the corresponding inductance change data, the relationship between inductance change and conductivity is solved to obtain a conductivity value; Based on all the conductivity values obtained by solving, the conductivity under the current temperature environment is calculated by averaging; The relationship between inductance change and conductivity is: wherein represents the inductance variation corresponding to the excitation signal of frequency f represents the measured conductivity, represents the lift-off, represents the number of turns of the coil, and respectively represent the inner and outer diameter of the coil, represents the vacuum permeability, represents the thickness of the coil, represents the angular frequency corresponding to the frequency f , represents the first kind Bessel function, represents the integration variable.​​

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