Metal matrix internal high-temperature non-contact measurement method using eddy current constant-inductance frequency modulation

Abstract

The invention discloses a metal matrix internal high-temperature non-contact measurement method using eddy current constant-inductance frequency modulation, and relates to the technical field of temperature measurement. According to the method, an electromagnetic field is excited through an eddy current coil, and the interference of a coating layer on the surface of a metal matrix is effectively overcome by utilizing the penetrability of the electromagnetic field. According to the method, a linear relation between the excitation frequency of an eddy current coil and the internal temperature of a measured metal matrix is established by utilizing an eddy current constant-inductance frequency modulation principle. And the internal temperature of the measured metal matrix is estimated by measuring the excitation frequency. The method comprises the steps of customizing a constant-temperature standard sample, recording a constant-inductance posture, obtaining coil constant inductance, changing the temperature of the standard sample, repeatedly measuring the standard sample, establishing a calibration formula, recovering the constant-inductance posture, measuring a metal matrix, obtaining a temperature value and the like. The method is a novel non-contact lossless temperature measurement means, effectively overcomes external interference factors such as surface oxidation and coating, realizes high-precision internal temperature measurement, and is of great significance.

Description

Technical Field

[0001] This invention relates to the field of temperature measurement technology, specifically to a non-contact measurement method for high-temperature interiors of metal substrates using eddy current fixed-sensor frequency modulation. Background Technology

[0002] In existing technologies, two main categories of measurement methods are generally used to obtain the temperature of high-temperature metal substrates. The first category is contact measurement, such as embedding thermocouples, which can effectively measure the internal temperature of the high-temperature metal substrate. The other category is non-contact measurement, such as installing infrared thermometers, which can effectively measure the surface temperature of the high-temperature metal substrate.

[0003] However, comparing the two existing categories of temperature measurement methods reveals several key differences: the first category effectively measures the internal temperature of a metal substrate, but requires contact with the object being measured, sometimes even causing damage; the second category solves the problem of non-contact measurement, but cannot accurately obtain the internal temperature of the metal substrate. Especially when the metal substrate surface is coated with protective materials (such as heat-insulating paint or thermal insulation coatings), neither category can achieve non-destructive temperature measurement without damaging the surface coating.

[0004] As is well known, electromagnetic fields have a penetrating effect and can effectively penetrate coatings on the surface of metal substrates. Electromagnetic field technology combines non-destructive, non-contact, and penetrating properties; however, the use of electromagnetic field technology for temperature measurement and monitoring of high-temperature metal substrates has not yet been fully developed and applied.

[0005] Therefore, in the field of high-temperature metal substrate temperature measurement, non-contact, non-destructive measurement methods have become a research focus. Compared to traditional contact measurement methods, such as infrared thermal imaging technology, remote measurement can be achieved in high-temperature heat flux environments, avoiding quality problems caused by high temperatures on the probe. However, current infrared thermal imaging technology is still based on the thermal radiation of the measured material. For objects with surface-coated insulation materials, it is still difficult to actually measure the metal substrate inside the insulation material. Therefore, researching novel non-contact, non-destructive temperature measurement methods to achieve high-temperature measurement inside the metal substrate through surface coatings is of great significance. Summary of the Invention

[0006] The purpose of this invention is to address the problems of existing technologies, such as contact measurements damaging the object being measured and non-contact measurements failing to penetrate surface coatings to obtain internal temperatures. This invention provides a non-contact method for measuring high temperatures inside a metal substrate using eddy current fixed-inductance frequency modulation. Based on the principle of "eddy current fixed-inductance frequency modulation," this invention uses an eddy current coil to excite an electromagnetic field, and then utilizes the penetrating power of the electromagnetic field to effectively overcome interference from the surface coating of the metal substrate. This method can penetrate the surface coating and accurately measure the internal temperature of the metal substrate without contact or damage to the object being measured.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] A non-contact measurement method for high-temperature interior of a metal substrate using eddy current fixed-inductance frequency modulation includes the following steps:

[0009] Step 1: Customize a constant temperature standard sample: Take a sample material of the same material as the metal substrate to be tested, and make a standard sample according to the surface morphology of the surface to be measured of the metal substrate; place the standard sample in a constant temperature environment with adjustable temperature; the standard sample has the same surface morphology of the surface to be measured as the metal substrate to be tested.

[0010] Step 2: Record the sensing attitude: Fix the eddy current coil above the surface to be measured of the standard sample, and record the sensing attitude of the eddy current coil at this time;

[0011] Step 3: Obtain the coil inductance: Measure the actual inductance of the eddy current coil using an inductance measuring instrument, and record the measured inductance value as the fixed inductance of the eddy current coil. ;

[0012] Step 4: Change the standard sample temperature: By adjusting the temperature of the constant temperature environment, the standard sample mentioned in Step 1 is brought to a suitable temperature. The standard samples were placed in different constant temperature environments; simultaneously, the actual temperature of the standard samples was measured and recorded using a temperature measuring instrument. The measured value of the sub-temperature is , , ..., The ;

[0013] Step 5: Repeat the measurement of the standard sample: This step involves repeating the measurement of the standard sample from step 4. The standard samples under different temperature conditions were respectively subjected to... Measurements of secondary eddy current constant inductance frequency modulation were performed, and the obtained measurement results were recorded. , , ..., , and as Measured value of the excitation frequency;

[0014] Step Six: Establish Calibration Formulas: Based on the results obtained in Steps Four and Five... Measured values ​​of each temperature , , ..., and Measured values ​​of each excitation frequency , , ..., Perform regression or fitting to establish an eddy current constant sensing calibration formula related to the material of the metal matrix to be tested;

[0015] Step 7: Restore the sensing posture: Place the eddy current coil above the surface to be measured of the metal substrate and fix it in the same sensing posture as in Step 2.

[0016] Step 8: Measurement of the metal substrate: Perform the eddy current constant inductance frequency modulation measurement on the metal substrate under test, and record the obtained measurement results as the measured value of the excitation frequency. ;

[0017] Step 9: Obtain the temperature value: The measured value of the excitation frequency mentioned in Step 8... Substituting the values ​​into the eddy current constant inductance calibration formula established in step six, the calculation result is... This refers to the internal temperature value of the metal substrate being measured. .

[0018] In the above steps, when performing the eddy current constant inductance frequency modulation, at all excitation frequencies... , , ..., , Under the influence of the current, all the eddy current coils exhibit the same inductance value. .

[0019] The sensing attitude is the lift-off and tilt angle between the eddy current coil and the surface to be measured.

[0020] The eddy current sensing calibration formula is used to describe the internal temperature of the metal substrate under test. Value and excitation frequency The functional relationship between them; the eddy current constant inductance calibration formula has the following linear functional relationship form: The parameters and This is a constant coefficient, the value of which is related to the material of the metal matrix to be tested, and can be obtained through regression or fitting of measured data.

[0021] In step five, the eddy current constant-inductance frequency modulation is a measurement process, and the measurement result is frequency. Specifically, it includes the following steps:

[0022] Step 1: Apply an excitation frequency of [frequency value] to the eddy current coil using a frequency modulation signal source. The exchange and encouragement;

[0023] Step 2: Using an inductance measuring instrument, measure the eddy current coil at the excitation frequency. Record the actual inductance value at this point. ;

[0024] Step 3: If the measured inductance value Less than the fixed inductance of the eddy current coil Then reduce the excitation frequency to And repeat step 1; if the measured inductance value Greater than the constant inductance of the eddy current coil Then the excitation frequency is increased to And repeat step 1; if the measured inductance value Equal to the constant inductance of the eddy current coil Then proceed to step 4; the The frequency adjustment accuracy of the frequency modulation signal source mentioned in step 1;

[0025] Step 4: Feedback on the current excitation frequency This is the measurement result of the eddy current constant inductance frequency modulation.

[0026] During the eddy current fixed-inductance frequency modulation process, the measured inductance value of the eddy current coil With excitation frequency There is a negative correlation between them, that is, the excitation frequency The higher the measured inductance value, the better. The smaller, the greater; conversely, the smaller.

[0027] Compared with existing temperature measurement technologies, this invention has the following advantages:

[0028] ①This invention utilizes the characteristics of eddy currents for temperature measurement, without requiring contact with the metal substrate being measured or any destructive treatment, thus achieving non-contact temperature measurement and exhibiting significant non-destructive properties.

[0029] ② This invention utilizes the internal conductivity characteristics of the metal substrate under test for temperature inversion, thus it is independent of external interference factors such as oxidation and coatings on the surface of the metal substrate, and has better stability. The electromagnetic field can effectively penetrate non-metallic coatings (such as heat-insulating paint and oxide layers) on the surface of the metal substrate, directly reflecting the internal state of the substrate, overcoming the application bottleneck of infrared thermometry and other technologies in such scenarios.

[0030] ③ Based on the eddy current fixed-inductance frequency modulation principle, the complex nonlinear relationship is transformed into a simple linear calibration relationship. The measurement model is simple and reliable, and is less affected by interference factors such as lift-off and small fluctuations in coil parameters. The internal temperature of the measured metal substrate is also measured. With excitation frequency The two exhibit a good linear relationship, thus the method of the present invention has high temperature measurement accuracy. Attached Figure Description

[0031] Figure 1 A schematic diagram of the overall flow of the measurement method according to an embodiment of the present invention;

[0032] Figure 2 A schematic diagram illustrating the principle of system device connection in the measurement method of this invention. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0034] This invention is based on the principle of "eddy current constant inductance frequency modulation." By actively adjusting the excitation frequency of the eddy current coil, its equivalent inductance remains constant (i.e., "constant inductance") when placed above a metal substrate at different temperatures. At this point, a definite correspondence exists between the excitation frequency and the resistivity of the metal substrate. Since the resistivity of metal exhibits a strong linear positive correlation with temperature, a linear functional relationship is also established between the excitation frequency and the internal temperature of the metal substrate. By pre-calibrating this relationship, the temperature can be inverted by measuring the frequency.

[0035] This invention can establish the excitation frequency of eddy current coils. Temperature of the metal substrate being measured The linear relationship between them. And further utilizing the excitation frequency... The measurement enables the determination of the internal temperature of the tested metal substrate. The estimate.

[0036] Inductance is a physical characteristic of a coil, which can be measured using an impedance meter (such as an LCR meter). When the coil is placed in air, the measured inductance is related to the excitation frequency used. Unrelated. However, when a coil is placed above (but not necessarily in contact with) a metal substrate being tested, it is called an eddy current coil. Eddy current coils generate eddy currents within the metal substrate. According to Lenz's law, the measured inductance of an eddy current coil... It is no longer equal to the measured inductance value in the air and will decrease due to the influence of eddy currents.

[0037] Based on the eddy current principle, the measured inductance of an eddy current coil placed above the metal substrate being tested is... , is the excitation frequency The electrical conductivity (material resistivity) of the metal being tested. The function of eddy currents. Research shows that, influenced by eddy currents, the measured inductance of the eddy current coil... It can be approximated as:

[0038]

[0039] Based on the inverse function relationship, the above equation can also be expressed as:

[0040]

[0041] The resistivity of most pure metallic materials It changes with temperature, and is related to its temperature. The relationship is mainly positively correlated, meaning it increases with increasing temperature, exhibiting a good linear growth relationship. The internal temperature of metallic materials... Its resistivity Satisfying the formula:

[0042] ‌

[0043] in: The resistivity of the measured metallic material at 0℃. is the temperature coefficient of resistance.

[0044] By reorganizing the above formulas, we can establish the internal temperature of metallic materials. With excitation frequency Relationship:

[0045]

[0046] In the above formula, for a given tested metallic material, the parameters are... and All are constants; while It is a variable whose value is the measured inductance of the eddy current coil. The function of . Therefore, the internal temperature of metallic materials. With excitation frequency The relationships between them are quite complex.

[0047] However, if constraints are set to ensure that the measured inductance of the eddy current coil is always kept constant... Constant (i.e., constant perception) ),but That is, it is a constant. Therefore, the internal temperature of the measured metal substrate is... With excitation frequency This will result in an ideal linear relationship, i.e., a linear evaluation model:

[0048]

[0049] In the formula, and All are constant coefficients.

[0050] This linear relationship can then be conveniently utilized by setting constraints (in this invention, a fixed sense). Furthermore, by adjusting the excitation frequency... The internal temperature of the metal substrate being measured Linear estimation is performed. In this invention, the detection mechanism is referred to as the principle of "eddy current constant induction frequency modulation".

[0051] This invention utilizes eddy current coils to generate an electromagnetic field, and then leverages the penetrating power of the electromagnetic field to effectively overcome interference from coatings on the surface of a metal substrate. Based on the principle of "eddy current fixed-inductance frequency modulation," a non-contact high-temperature measurement method for the interior of a metal substrate using eddy current fixed-inductance frequency modulation is realized.

[0052] The following combination Figure 1 Taking the measurement of the internal temperature of a 20mm thick copper plate with a coating as an example, the measurement method of this embodiment includes the following steps:

[0053] Step 1: Customize the constant temperature standard sample. Take a piece of copper material of the same type as the 20mm thick flat copper plate, with the surface to be measured being flat, and make a standard sample 10mm thick, 100mm long, and 100mm wide; for example... Figure 2 As shown, the standard sample is placed in a temperature-controlled constant temperature chamber (such as the GYJ-H480 type).

[0054] Step Two: Record the sensing attitude. Take a circular coil as the eddy current coil. The coil's parameters are: inner diameter 3.015mm, outer diameter 5.460mm, coil thickness 2.940mm, and 10 turns. Figure 2 As shown, the eddy current coil is also placed in a temperature-adjustable constant temperature chamber GYJ-H480 and placed parallel to the plane of the standard sample 1 mm above it. In this embodiment, the recorded sensing posture is the lifting distance of the eddy current coil from the plane of the standard sample by 1 mm and the tilt angle of 0° (i.e., parallel).

[0055] Step 3: Obtain the coil's inductance. For example... Figure 2 As shown, the leads of the eddy current coil in this embodiment were led out of the GYJ-H480 constant temperature chamber, and the actual inductance of the eddy current coil was measured in air (i.e., away from any metal conductor) using a MICROTEST6630E LCR analyzer. The measured inductance value was 0.7. As the inductance of the eddy current coil .

[0056] Step 4: Change the temperature of the standard sample. By adjusting the temperature of the internal environment of the GYJ-H480 constant temperature chamber, the standard sample was placed in different constant temperature environments three times. At the same time, the actual temperature of the internal environment of the GYJ-H480 constant temperature chamber was measured by thermocouples, and the measured values ​​of the three different temperatures were recorded as 100℃, 300℃ and 500℃.

[0057] Step 5: Repeat the measurement of the standard sample. For the standard sample under three different temperature conditions in Step 4, perform three measurements of eddy current constant inductance frequency modulation. Set the measured values ​​of the excitation frequency at 100℃, 300℃ and 500℃ as 18.96KHz, 42.97KHz and 66.95KHz respectively.

[0058] Step Six: Establish Calibration Formula. Linear fitting is performed on the measured values ​​of the three temperatures (100℃, 300℃, and 500℃) and the three excitation frequencies (18.96kHz, 42.97kHz, and 66.95kHz) obtained in Steps Four and Five to establish an eddy current constant-sensitivity calibration formula related to the copper plate. .

[0059] Step 7: Restore the sensing posture. Place the eddy current coil on the plane of the 20mm thick copper plate and fix it in the same sensing posture as in Step 2, that is, lift it 1mm away from the copper plate and tilt it at 0°.

[0060] Step 8: Measurement of the metal substrate. Eddy current constant inductance frequency modulation measurement was performed on a 20mm thick copper plate. The measurement results are as follows: It is 50.32KHz.

[0061] Step 9: Obtain the temperature value. The measured value of the excitation frequency... 50.32kHz, substitute into the eddy current constant inductance calibration formula established in step six. The calculation results The internal temperature of the copper plate is 361.2℃.

[0062] like Figure 1 As shown, the eddy current fixed-inductance frequency modulation in this embodiment is a measurement process, and the measurement result is a frequency value. Specifically, it includes the following steps:

[0063] Step 1: Apply excitation frequency to the eddy current coil using a MICROTEST 6630E LCR analyzer. 40kHz AC excitation;

[0064] Step 2: Using a MICROTEST 6630E LCR analyzer, measure the eddy current coil in this embodiment at the excitation frequency. Measured inductance value If it is 0.73 ;

[0065] Step 3: Obviously, in this embodiment, the measured inductance value 0.73 The eddy current coil has a constant inductance. 0.7 Then adjust the excitation frequency. And repeat step 1. Here To ensure the frequency adjustment accuracy of the MICROTEST6630E LCR analyzer; in this embodiment, after multiple adjustments, when the measured inductance value... 0.7 , and eddy current coil fixed inductance They are equal. At this time, the excitation frequency of the LCR analyzer is equal. 50.32KHz.

[0066] Step 4: Feedback on the current excitation frequency 50.32kHz was used as the measurement result for this eddy current fixed-inductance frequency modulation.

[0067] This invention utilizes eddy current coils to excite an electromagnetic field, and then leverages the penetrating power of the electromagnetic field to effectively overcome interference from coatings on the surface of a metal substrate. The method employs the principle of eddy current induction frequency modulation to establish a linear relationship between the excitation frequency of the eddy current coil and the internal temperature of the measured metal substrate. Furthermore, by measuring the excitation frequency, the internal temperature of the measured metal substrate is estimated. The provided method includes steps such as customizing a constant-temperature standard sample, recording the induction posture, obtaining coil induction, changing the standard sample temperature, repeating the standard sample measurement, establishing a calibration formula, restoring the induction posture, measuring the metal substrate, and obtaining the temperature value. This invention is a novel non-contact, non-destructive temperature measurement method that effectively overcomes external interference factors such as surface oxidation and coatings, achieving high-precision internal temperature measurement, and is of significant importance.

[0068] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. 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 or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A non-contact measurement method for high-temperature interior of a metal substrate using eddy current fixed-inductance frequency modulation, characterized in that, Includes the following steps: Step 1: Customize the constant temperature standard sample: Take a sample material of the same material as the metal substrate to be tested, and make a standard sample according to the surface morphology of the surface to be measured of the metal substrate; and place the standard sample in a constant temperature environment with adjustable temperature. Step 2: Record the sensing attitude: Fix the eddy current coil above the surface to be measured of the standard sample and record the sensing attitude at this time; Step 3: Obtain the coil's fixed inductance: Use an inductance measuring instrument to measure the actual inductance of the eddy current coil, and record the measured inductance value as the fixed inductance of the eddy current coil. ; Step 4: Change the standard sample temperature: By adjusting the temperature of the constant temperature environment, the standard sample from Step 1... The samples were placed in different constant temperature environments; simultaneously, the actual temperature of the standard samples was measured and recorded using temperature measuring instruments. The measured value of the sub-temperature is , , ..., ;in, ; Step 5: Repeated measurement of standard sample: This involves repeating the measurements from step 4. Standard samples under different temperature conditions were subjected to [further testing]. Measurements of secondary eddy current constant inductance frequency modulation were performed, and the obtained measurement results were recorded. , , ..., , and as Measured value of the excitation frequency; Step Six: Establish Calibration Formula: Based on the results obtained in Steps Four and Five Measured values ​​of each temperature , , ..., and Measured values ​​of each excitation frequency , , ..., Perform regression or fitting to establish an eddy current constant sensing calibration formula related to the material of the metal matrix to be tested; Step 7: Restore the sensing posture: Place the eddy current coil above the surface to be measured of the metal substrate and fix it in the same sensing posture as in Step 2. Step 8: Measurement of the metal substrate: Perform eddy current constant inductance frequency modulation measurement on the metal substrate under test, and record the obtained measurement results as the measured value of the excitation frequency. ; Step Nine: Obtain the temperature value: The measured value of the excitation frequency from Step Seven... Substituting the values ​​into the eddy current constant inductance calibration formula established in step six, the calculation result is... This refers to the internal temperature value of the metal substrate being tested. .

2. The method for high-temperature non-contact measurement of the interior of a metal substrate using eddy current fixed-inductance frequency modulation according to claim 1, characterized in that, When performing eddy current fixed-inductance frequency modulation, at the excitation frequency , , ..., , Under the influence of the current, all eddy current coils exhibit the same inductance value. .

3. The method for high-temperature non-contact measurement inside a metal substrate using eddy current fixed-inductance frequency modulation according to claim 1, characterized in that, In step two or step seven, the sensing posture is the lift-off and tilt angle between the eddy current coil and the surface to be measured.

4. The method for high-temperature non-contact measurement of the interior of a metal substrate using eddy current fixed-inductance frequency modulation according to claim 1, characterized in that, In step six, the eddy current constant inductance calibration formula describes the internal temperature of the metal substrate under test. Value and excitation frequency The functional relationship between them; the eddy current constant inductance calibration formula has a linear functional relationship form: Among them, parameters and It is a constant coefficient.

5. The method for high-temperature non-contact measurement inside a metal substrate using eddy current fixed-inductance frequency modulation according to claim 1, characterized in that, In step five or step eight, eddy current constant inductance frequency modulation is a measurement process, and the measurement result is frequency. Specifically, it includes the following steps: Step 1: Apply an excitation frequency of [frequency value] to the eddy current coil using a frequency modulation signal source. The exchange and encouragement; Step 2: Using an inductance measuring instrument, measure the eddy current coil at the excitation frequency. Record the actual inductance value at this point. ; Step 3: If the measured inductance value Less than the fixed inductance of eddy current coils Then reduce the excitation frequency to And repeat step 1; if the measured inductance value Greater than the fixed inductance of eddy current coils Then the excitation frequency is increased to And repeat step 1; if the measured inductance value Equal to the fixed inductance of an eddy current coil Then proceed to step 4; This refers to the frequency adjustment accuracy of the frequency modulation signal source in step 1; Step 4: Feedback on the current excitation frequency As the measurement result of eddy current fixed inductance frequency modulation.

6. The method for high-temperature non-contact measurement inside a metal substrate using eddy current fixed-inductance frequency modulation according to claim 5, characterized in that, In step five or eight, during the measurement of eddy current constant inductance frequency modulation, the measured inductance value of the eddy current coil is... With excitation frequency There is a negative correlation between them, i.e., excitation frequency. The higher the value, the higher the measured inductance. The smaller, the greater; conversely, the smaller.

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