Film thickness measuring device, excitation signal frequency determination method thereof and terminal equipment

Abstract

The invention relates to a thin film thickness measuring device, an excitation signal frequency determining method thereof and terminal equipment, and the device comprises a housing which comprises an opening; the test coil circuit comprises a test coil and a first transmission line connected between the test coil and the signal processing circuit, and the test coil is close to the opening so as to generate a test alternating magnetic field penetrating through the opening and output a test signal; the reference coil circuit comprises a reference coil and a second transmission line connected between the reference coil and the signal processing circuit, and the reference coil is far away from the opening so as to generate a reference alternating magnetic field which cannot pass through the opening and output a reference signal; the amplifying circuit is used for performing differential operation on the test signal and the reference signal to obtain a differential signal, and performing phase-locked filtering processing on the differential signal based on the frequency of the excitation signal to obtain a phase-locked signal; and the signal processing circuit is used for generating an excitation signal with a set frequency and outputting a test signal according to the phase-locked signal. The method has the advantage of high film thickness accuracy.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear power plant equipment, and in particular to a film thickness measuring device, an excitation signal frequency determination method and terminal equipment thereof. Background Art

[0002] As the nuclear reaction proceeds for a long time, an oxide film will be produced on the surface of the fuel rod. The presence of the oxide film increases the thermal resistance between the cladding tube surface and the coolant, seriously affecting the thermal conductivity of the cladding tube and the heat exchange capacity of the fuel assembly. As the thickness of the oxide film increases, the temperature of the fuel rod will continue to rise, accelerating the corrosion and aging of the fuel rod, creating a huge safety hazard. Therefore, the measurement of the thickness of the oxide film on the surface of the fuel rod is related to the safety of the nuclear power plant, and the accuracy of the measurement of the thickness of the oxide film on the surface of the fuel rod is particularly important.

[0003] In the related art, although some existing thickness measuring devices can achieve accurate thickness measurement under normal conditions, in nuclear power plants, the ambient temperature of the fuel rods is high, and the temperature will affect the electrical parameters of the electronic devices in the thickness measuring device (such as magnetic permeability, etc.), resulting in poor measurement accuracy of the thickness measuring device, which is not conducive to the safe operation of the nuclear power plant. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a film thickness measuring device and an excitation signal frequency determination method and terminal equipment thereof.

[0005] The technical solution adopted by the present invention to solve the technical problem is: constructing a film thickness measuring device, including a test coil circuit, a reference coil circuit, an amplifier circuit, a signal processing circuit and a housing;

[0006] The housing includes an opening;

[0007] The test coil circuit comprises a test coil and a first transmission line connected between the test coil and the signal processing circuit, wherein the test coil is arranged in the housing and close to the opening, and the test coil is used to generate a test alternating magnetic field passing through the opening when receiving an excitation signal output by the signal processing circuit, and to act on the film to be tested when the test alternating magnetic field acts on the film to be tested, so as to output a test signal according to the thickness of the film to be tested;

[0008] The reference coil circuit includes a reference coil and a second transmission line connected between the reference coil and the signal processing circuit, wherein the reference coil is arranged in the housing and away from the opening, and is used to generate a reference alternating magnetic field that cannot pass through the opening when receiving an excitation signal output by the signal processing circuit, and output a reference signal;

[0009] The amplifier circuit is connected to the test coil circuit, the reference coil circuit and the signal processing circuit, and is used to perform a differential operation on the test signal and the reference signal to obtain a differential signal, and perform a phase-locked filtering process on the differential signal based on the frequency of the excitation signal to obtain a phase-locked signal;

[0010] The signal processing circuit is used to generate an excitation signal of a set frequency and output a test signal according to the phase-locked signal.

[0011] Preferably, the test coil and the reference coil are coils with consistent configuration parameters, and the first transmission line and the second transmission line are coaxial lines with consistent configuration parameters.

[0012] Preferably, the film thickness measuring device further comprises a magnetic field transmission element and a temperature sensor;

[0013] The magnetic field transmission member is covered on the opening;

[0014] The temperature sensor is disposed in the housing and close to the test coil to output a temperature signal to the signal processing circuit according to the temperature in the housing;

[0015] The signal processing circuit is further configured to compensate the test signal according to the temperature signal.

[0016] Preferably, the magnetic field transmission element is a microlens; the film thickness measurement device further comprises a spacer;

[0017] The spacer is disposed between the test coil and the reference coil.

[0018] Preferably, the amplifier circuit includes a differential amplifier circuit and a phase-locked amplifier circuit;

[0019] The first input end of the differential amplifier circuit is connected to the connection node between the test coil and the first transmission line, the second input end is connected to the connection node between the reference coil and the second transmission line, and the output end outputs the differential signal to the phase-locked amplifier circuit;

[0020] The phase-locked amplifier circuit is connected to the signal processing circuit to filter out the component of the differential signal whose frequency is different from the frequency of the excitation signal to obtain the phase-locked signal.

[0021] The present invention also constructs a method for determining the frequency of an excitation signal, comprising:

[0022] An equivalent coil circuit is established based on the test coil circuit or the reference coil circuit in the above-mentioned film thickness measuring device; wherein the equivalent coil circuit includes an equivalent coil and an equivalent transmission line;

[0023] The equivalent coil is equivalent to an RLC circuit, and coil design parameters are obtained; wherein the coil design parameters include an inductance value, an equivalent capacitance value, and an equivalent resistance value of the equivalent coil;

[0024] Obtaining a design length of the equivalent transmission line, and dividing the equivalent transmission line equally based on a set unit length to obtain n sub-equivalent lines; wherein n is a positive integer;

[0025] Each of the sub-equivalent lines is equivalent to an RLC circuit, and sub-equivalent line design parameters are obtained; wherein the sub-equivalent line design parameters include an equivalent inductance value, an equivalent capacitance value, and an equivalent resistance value of each of the sub-equivalent lines;

[0026] Determine a simulated impedance characteristic curve of the equivalent coil circuit based on the coil design parameters and the sub-equivalent line design parameters;

[0027] The optimal resonant frequency of the equivalent coil circuit is determined according to the simulated impedance characteristic curve, and the frequency of the excitation signal output by the signal processing circuit in the film thickness measurement device is determined according to the optimal resonant frequency.

[0028] Preferably, the step of determining the simulated impedance characteristic curve of the equivalent coil circuit based on the coil design parameters and the sub-equivalent line design parameters comprises:

[0029] Calculating an impedance expression of an equivalent coil circuit based on the coil design parameters and the sub-equivalent line design parameters;

[0030] Acquiring a resonant frequency setting range of the equivalent coil circuit, and generating a simulated impedance characteristic curve of the equivalent coil circuit according to the resonant frequency setting range and an impedance expression of the equivalent coil circuit;

[0031] Wherein, the impedance expression of the equivalent coil circuit is:

[0032] Zc represents the impedance of the equivalent coil, Rc represents the equivalent resistance value of the equivalent coil, Lc represents the inductance value of the equivalent coil, Cc represents the equivalent capacitance value of the equivalent coil, Z1 represents the impedance of the equivalent resistance and equivalent inductance of the sub-equivalent line in series, R represents the equivalent resistance value of the sub-equivalent line, L represents the equivalent inductance value of the sub-equivalent line, C represents the equivalent capacitance value of the sub-equivalent line, Z2 represents the equivalent capacitance impedance of the sub-equivalent line, f represents the excitation signal frequency of the equivalent coil circuit, and Zz represents the impedance of the equivalent coil circuit.

[0033] Preferably, the step of determining the optimal resonant frequency of the equivalent coil circuit according to the simulated impedance characteristic curve comprises:

[0034] The impedance variation characteristics in the simulated impedance characteristic curve are analyzed to determine that at least one impedance peak that meets the set requirements appears in the curve, the frequency value corresponding to each impedance peak is defined as an optional resonant frequency, and one of the optional resonant frequencies is determined as the optimal resonant frequency.

[0035] Preferably, the excitation signal frequency determination method further includes:

[0036] The excitation signal frequency output by the signal processing circuit in the film thickness measuring device is set to the optimal resonance frequency, and a plurality of test signals output by the film thickness measuring device when testing the thickness of a preset standard film group are obtained; wherein the standard film group includes a plurality of prefabricated standard films with different thicknesses;

[0037] Determine, according to the plurality of test signals, the actual measurement value corresponding to when the thin film thickness measuring device tests each of the standard films;

[0038] Calculating the error value between each actual measurement value and the thickness of the corresponding standard film to obtain a plurality of first error values;

[0039] It is determined whether each of the first error values ​​is within a set error range. If each of the first error values ​​is within the set error range, it is determined that the optimal resonant frequency is qualified.

[0040] The present invention also constructs a terminal device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above-mentioned method for determining the frequency of an excitation signal when executing the computer program.

[0041] The implementation of the present invention has the following beneficial effects: it achieves the filtering of the environmental noise component (including the ambient temperature) and the out-of-frequency noise in the test signal, thereby reducing the influence of environmental factors and circuit factors, and improving the accuracy of the test signal in characterizing the thickness of the measured film. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0043] Figure 1 is a circuit structure block diagram of a thin film thickness measuring device in some embodiments of the present invention;

[0044] Figure 2 is a schematic diagram of the structure of a film thickness measuring device in some embodiments of the present invention;

[0045] Figure 3 is a flowchart of a method for determining the frequency of an excitation signal in some embodiments of the present invention;

[0046] Figure 4 is an equivalent circuit schematic diagram of an equivalent coil and an equivalent transmission line in some embodiments of the present invention;

[0047] Figure 5 is a simulated impedance characteristic curve of an equivalent coil circuit in some embodiments of the present invention;

[0048] Figure 6 It is a circuit structure block diagram of a terminal device in some embodiments of the present invention. DETAILED DESCRIPTION

[0049] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0050] It should be noted that the flowcharts shown in the accompanying drawings are only exemplary and do not necessarily include all the contents and operations / steps, nor do they have to be executed in the order described. For example, some operations / steps can be decomposed, while some operations / steps can be combined or partially combined, so the actual execution order may change according to actual conditions.

[0051] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities may be implemented in software form, or in one or more hardware modules or integrated circuits, or in different networks and / or processor devices and / or microcontroller devices.

[0052] The embodiment of the present invention provides a film thickness measuring device, which can accurately measure the thickness of the film. Figure 1 and Figure 2 The film thickness measuring device may include a test coil circuit 1 , a reference coil circuit 2 , an amplifier circuit 3 , a signal processing circuit 4 and a housing 5 .

[0053] See also Figure 2 The shell 5 includes an opening 51, and a cavity capable of accommodating electronic devices is also provided in the shell 5.

[0054] See also Figure 1 The test coil circuit 1 includes a test coil 11 and a first transmission line 12 connected between the test coil 11 and the signal processing circuit 4. Figure 2As shown, the test coil 11 is arranged in the cavity of the housing 5 and close to the opening 51. The test coil 11 is used to generate a test alternating magnetic field passing through the opening 51 when receiving the excitation signal output by the signal processing circuit 4, and act on the film to be tested (referred to as the film to be tested) in the test alternating magnetic field to output a test signal according to the thickness of the film to be tested. Specifically, the first end of the test coil 11 is connected to the signal processing circuit 4 via the first transmission line 12, and the second end of the test coil 11 is grounded and forms a loop with the signal processing circuit 4. It can be understood that the opening 51 can be brought close to the film to be tested so that the test alternating magnetic field can act on the film to be tested, so that the eddy current generated by the test coil 11 will change based on the thickness of the different films to be tested, so that the first end of the test coil 11 can generate a test signal that can characterize the thickness of the film to be tested. It should be noted that the eddy current generated by the test coil 11 will also be affected by the environment in which the test coil 11 is located, so the test signal also contains the environmental noise component of the environment in which the test coil 11 is located.

[0055] See also Figure 1 The reference coil circuit 2 includes a reference coil 21 and a second transmission line 22 connected between the reference coil 21 and the signal processing circuit 4. Figure 2 As shown, the reference coil 21 is arranged in the cavity of the housing 5 and away from the opening 51. The reference coil 21 is used to generate a reference alternating magnetic field that cannot pass through the opening 51 when receiving the excitation signal output by the signal processing circuit 4, and output a reference signal. Specifically, the first end of the reference coil 21 is connected to the signal processing circuit 4 via the second transmission line 22, and the second end of the reference coil 21 is grounded and forms a loop with the signal processing circuit 4. It can be understood that when the test alternating magnetic field can act on the film to be tested, the reference coil 21 cannot act on the film to be tested, and the eddy current generated by the reference coil 21 cannot change with the thickness of the film to be tested. Therefore, the eddy current generated by the reference coil 21 is mainly determined by the environment where the reference coil 21 is located, and the reference coil 21 is arranged near the test coil 11. The actual working environment of the reference coil 21 and the test coil 11 is almost the same, so the reference signal generated by the first end of the reference coil 21 can characterize the environmental noise component of the environment where the test coil 11 is located.

[0056] See also Figure 1, the amplifier circuit 3 is connected to the test coil circuit 1, the reference coil circuit 2 and the signal processing circuit 4, and the amplifier circuit 3 is used to perform differential operation on the test signal and the reference signal to obtain a differential signal, and perform phase-locked filtering on the differential signal based on the frequency of the excitation signal to obtain a phase-locked signal. It can be understood that performing differential operation on the test signal and the reference signal is equivalent to subtracting the reference signal from the test signal, which is equivalent to filtering out the environmental noise component in the test signal, so the obtained differential signal is almost only determined by the thickness of the film to be measured. Since the test coil 11 is affected by the capacitive reactance, impedance, etc. in the test coil circuit 1 when excited by the excitation signal, it will inevitably generate noise of other frequencies (recorded as different frequency noise), and the role of performing phase-locked filtering on the differential signal based on the frequency of the excitation signal is to separate the component in the differential signal whose frequency is close to or the same as the frequency of the excitation signal, thereby obtaining a phase-locked signal whose frequency is close to or the same as the frequency of the excitation signal and can accurately characterize the thickness of the film to be measured.

[0057] See also Figure 1 , the signal processing circuit 4 is used to generate an excitation signal of a set frequency, and output a test signal according to the phase-locked signal. Specifically, the signal processing circuit 4 may include an existing signal generating circuit capable of generating excitation signals of multiple frequencies, which can not only output an excitation signal, but also set the set frequency of the excitation signal according to the operation of the staff. In addition, the excitation signal can be a sine wave signal, a pulse wave, a square wave and other types of signals. In order to improve the stability of the eddy current field generated by the test coil 11 and the reference coil 21 and improve the measurement accuracy of the device, the excitation signal is preferably a sine wave signal. The phase-locked signal is an AC signal of a certain frequency, which is not convenient for the terminal device to detect directly, and the signal processing circuit 4 will generate a test signal that can accurately characterize the thickness of the measured film and is a digital signal or an analog signal according to the phase-locked signal, so that the terminal device can calculate the thickness of the measured film according to the test signal. It should be noted that the main purpose of the embodiment of the present invention is to achieve the filtering of the environmental noise component (including the ambient temperature) and the different frequency noise in the test signal, thereby reducing the influence of environmental factors and circuit factors, and achieving the improvement of the accuracy of the test signal characterizing the thickness of the measured film.

[0058] In some embodiments, the test coil 11 and the reference coil 21 are coils with consistent configuration parameters, and the first transmission line 12 and the second transmission line 22 are coaxial lines with consistent configuration parameters. It can be understood that this embodiment is equivalent to designing the test coil circuit 1 and the reference coil circuit 2 as circuit structures with completely consistent circuit parameters and circuit connection structures (that is, the hardware of the test coil circuit 1 and the reference coil circuit 2 are consistent), so that the test coil 11 and the reference coil 21 can generate the same eddy current changes as much as possible when placed in the same environment, that is, the reference signal can more accurately characterize the environmental noise component of the test coil 11, thereby improving the accuracy of film thickness measurement.

[0059] In some embodiments, Figure 2 As shown, the film thickness measuring device may further include a magnetic field transmission member 6 and a temperature sensor 7. The magnetic field transmission member 6 is covered on the opening 51 so that the housing 5 forms a closed structure, which can maintain the stability of the internal environment of the housing 5, ensure that the test coil 11 and the reference coil 21 work in the same environment as much as possible, and help improve the reliability of the differential operation.

[0060] See also Figure 2 The temperature sensor 7 is arranged in the cavity of the housing 5 and close to the test coil 11, so as to output a temperature signal to the signal processing circuit 4 according to the temperature in the housing 5. Accordingly, the signal processing circuit 4 is also used to compensate the test signal according to the temperature signal. Specifically, the temperature sensor 7 can be a thermistor of model PT1000. Since the test coil 11 and the reference coil 21 will generate heat during operation, and the electrical parameters (including conductivity and magnetic permeability, etc.) of the test coil circuit 1 and the reference coil circuit 2 will be affected by temperature, although a part of the temperature effect can be filtered out after differential operation, the test alternating magnetic field generated by the test coil 11 acts on the film to be tested, while the reference alternating magnetic field generated by the reference coil 21 does not act on the film to be tested, resulting in a difference in the actual power of the test coil 11 and the reference coil 21, so the heating of the two coils is slightly different, and the temperature sensor 7 is arranged close to the test coil 11 mainly to measure the temperature of the test coil 11 to generate a temperature signal that can characterize the temperature of the test coil 11, and compensating the test signal based on the temperature signal can improve the accuracy of film thickness measurement. Furthermore, the signal processing circuit 4 can restore the temperature of the test coil 11 based on the temperature signal and restore the initial measured thickness of the film under test based on the phase-locked signal, and then substitute the temperature of the test coil 11 into the pre-stored function to obtain a compensation value, and add the compensation value to the initial measured thickness to obtain the compensated measured thickness, and finally generate a test signal based on the compensated measured thickness.

[0061] In some embodiments, Figure 2 As shown, the magnetic field transmission member 6 may be a micro lens. In order to ensure the strength of the magnetic field transmission member 6, the magnetic field transmission member 6 is preferably a sapphire micro lens.

[0062] In some embodiments, Figure 2 As shown, the thin film thickness measuring device may further include a spacer 8 .

[0063] See also Figure 2The spacer 8 is disposed between the test coil 11 and the reference coil 21, so that the test coil 11 and the reference coil 21 are kept at a certain distance. On the one hand, it can ensure that the reference coil 21 is as close to the test coil 11 as possible, so as to ensure that the working environment of the two coils is as similar as possible, and improve the reliability of the reference signal. On the other hand, it ensures that the reference alternating magnetic field generated by the reference coil 21 cannot pass through the opening 51. In order to reduce the influence of the spacer 8 on the test alternating magnetic field and the reference alternating magnetic field, the spacer 8 is preferably a frame made of ceramic. In addition, the frame can also be used to fix the test coil 11 and the reference coil 21.

[0064] In some embodiments, Figure 1 As shown, the amplifier circuit 3 includes a differential amplifier circuit 31 and a phase-locked amplifier circuit 32 .

[0065] See also Figure 1 , the first input end of the differential amplifier circuit 31 is connected to the connection node between the test coil 11 and the first transmission line 12 to access the test signal, the second input end of the differential amplifier circuit 31 is connected to the connection node between the reference coil 21 and the second transmission line 22 to access the reference signal, the output end of the differential amplifier circuit 31 is connected to the phase-locked amplifier circuit 32, and the differential amplifier circuit 31 is used to subtract the reference signal from the test signal to output the differential signal to the phase-locked amplifier circuit 32 through the output end of the differential amplifier circuit 31. Among them, the differential amplifier circuit 31 can be an existing differential amplifier circuit or a subtraction amplifier circuit.

[0066] See also Figure 1 The phase-locked amplifier circuit 32 is connected to the signal processing circuit 4 to access the excitation signal to filter out the component with a frequency different from the frequency of the excitation signal in the differential signal to obtain a phase-locked signal. The phase-locked amplifier circuit 32 can be an existing phase-locked amplifier or a phase-locked amplifier circuit.

[0067] The present invention outputs a test signal capable of characterizing the thickness of a film to be measured through a test coil in a test coil circuit; at the same time, a reference signal capable of representing an environmental noise component in the test signal is output through a reference coil in a reference coil circuit; then, an amplifier circuit is used to filter out the environmental noise component in the test signal based on the test signal and the reference signal, and a differential signal after filtering out the environmental noise component is phase-locked filtered to filter out the out-of-frequency noise in the test signal to obtain a phase-locked signal; finally, a signal processing circuit is used to output a test signal capable of representing the thickness of the film to be measured according to the phase-locked signal; it can be understood that the present invention achieves the filtering out of the environmental noise component (including the ambient temperature) and the out-of-frequency noise in the test signal, thereby reducing the influence of environmental factors and circuit factors, and achieving the improvement of the accuracy of the test signal in representing the thickness of the film to be measured.

[0068] See also Figure 3The present invention also provides a method for determining the frequency of an excitation signal, which may include step S10, step S20, step S30, step S40, step S50 and step S60.

[0069] Step S10 includes: establishing an equivalent coil circuit based on the test coil circuit or the reference coil circuit in the film thickness measuring device; wherein the equivalent coil circuit includes an equivalent coil and an equivalent transmission line. In this step, the existing circuit EDA software can be used based on Figure 1 The circuit structure block diagram shown establishes an equivalent coil circuit. It should be noted that, since the circuit structures of the test coil circuit and the reference coil circuit are the same, the equivalent coil circuit is applicable to both the test coil circuit 1 and the reference coil circuit 2, and the equivalent coil can be equivalent to the test coil 11 or the reference coil 21, and the equivalent transmission line is equivalent to the first transmission line 12 and the second transmission line 22.

[0070] Step S20 includes: converting the equivalent coil into an RLC circuit and obtaining coil design parameters; wherein the coil design parameters include the inductance value, equivalent capacitance value and equivalent resistance value of the equivalent coil. In this step, since the equivalent coil has a certain internal resistance (i.e., equivalent resistance value) and the equivalent coil must have a parasitic capacitance of a certain capacitance value (i.e., equivalent capacitance value), the equivalent coil can be converted into the following: Figure 4 In addition, the inductance, capacitance and resistance of the equivalent coil are determined by the actual model of the coil, so the inductance, capacitance and resistance can be directly obtained from the coil specification sheet or measured using an LCR tester.

[0071] Step S30 includes: obtaining the design length of the equivalent transmission line, dividing the equivalent transmission line equally based on the set unit length, and obtaining n sub-equivalent lines; wherein n is a positive integer. In a nuclear power plant, the film thickness measuring device needs to measure the thickness of the oxide film on the surface of the fuel rod, and the length of the first and second transmission lines is generally configured to be more than 33 feet (approximately equal to 10 meters). In theory, the more sub-equivalent lines there are, the more conducive to the accuracy of the simulation results. However, considering that setting the unit length too short will increase the difficulty of testing the sub-equivalent line design parameters of the sub-equivalent line, the set unit length is preferably set to 0.1 feet. It can be understood that n can be set to the integer digit of the quotient of the design length divided by the set unit length.

[0072] Step S40 includes: each sub-equivalent line is equivalent to an RLC circuit, and the sub-equivalent line design parameters are obtained; wherein the sub-equivalent line design parameters include the equivalent inductance value, equivalent capacitance value and equivalent resistance value of each sub-equivalent line. In this step, a transmission line (i.e., a coaxial line) of a set unit length can be intercepted, and then the sub-equivalent line design parameters are measured by an LCR tester.

[0073] Step S50 includes: determining a simulated impedance characteristic curve of the equivalent coil circuit based on the coil design parameters and the sub-equivalent line design parameters.

[0074] In some embodiments, the step of determining a simulated impedance characteristic curve of the equivalent coil circuit based on the coil design parameters and the sub-equivalent line design parameters may include:

[0075] The impedance expression of the equivalent coil circuit is calculated based on the coil design parameters and the sub-equivalent line design parameters;

[0076] Obtaining a resonant frequency setting range of the equivalent coil circuit, and generating a simulated impedance characteristic curve of the equivalent coil circuit according to the resonant frequency setting range and an impedance expression of the equivalent coil circuit;

[0077] Among them, the impedance expression of the equivalent coil circuit is:

[0078]

[0079] Zc represents the impedance of the equivalent coil, Rc represents the equivalent resistance value of the equivalent coil, Lc represents the inductance value of the equivalent coil, Cc represents the equivalent capacitance value of the equivalent coil, Z1 represents the impedance of the equivalent resistance and equivalent inductance of the sub-equivalent line in series, R represents the equivalent resistance value of the sub-equivalent line, L represents the equivalent inductance value of the sub-equivalent line, C represents the equivalent capacitance value of the sub-equivalent line, Z2 represents the equivalent capacitance impedance of the sub-equivalent line, f represents the excitation signal frequency of the equivalent coil circuit, and Zz represents the impedance of the equivalent coil circuit.

[0080] In this embodiment, after calculating n, the coil design parameters and the sub-equivalent line design parameters are substituted into the impedance expression of the equivalent coil circuit, and the frequency range of f is limited (such as 0MHz to 12MHz), so that the impedance of the equivalent coil circuit corresponding to different excitation signal frequencies can be obtained. Finally, the simulated impedance characteristic curve of the equivalent coil circuit is fitted through a graph generation tool (such as Excel, etc.).

[0081] In some embodiments, the simulated impedance characteristic curve of the equivalent coil circuit can refer to Figure 5 In this embodiment, the inductance, capacitance and resistance of the equivalent coil are 1.5 microhenry, 2.08 pF and 3.3 ohms, respectively, the equivalent inductance, capacitance and resistance of each sub-equivalent line are 0.12 microhenry, 37 pF and 0.000048 ohms, respectively, and n is equal to 330.

[0082] Step S60 includes: determining the optimal resonant frequency of the equivalent coil circuit according to the simulated impedance characteristic curve, and determining the frequency of the excitation signal output by the signal processing circuit in the film thickness measurement device according to the optimal resonant frequency.

[0083] In some embodiments, the step of determining the optimal resonant frequency of the equivalent coil circuit according to the simulated impedance characteristic curve may include: analyzing the impedance change characteristics in the simulated impedance characteristic curve to determine at least one impedance peak that meets the set requirements in the curve, defining the frequency value corresponding to each impedance peak as an optional resonant frequency, and determining one of the optional resonant frequencies as the optimal resonant frequency. Figure 5 For example, the simulated impedance characteristic curve can be analyzed by the existing graph analysis algorithm to determine all the peaks contained in the simulated impedance characteristic curve, and each peak corresponds to an impedance peak. It can be understood that the simulated impedance characteristic curve of this embodiment has two impedance peaks, one of which has a frequency of 2.6 MHz and the other has a frequency of 8.6 MHz, so this embodiment can define 2.6 MHz and 8.6 MHz as optional resonant frequencies. Of course, the staff can also determine the two "obvious" peaks by observing the simulated impedance characteristic curve, and can also determine the two impedance peaks, and then input the frequencies of the two "obvious" peaks through the human-computer interaction unit.

[0084] To ensure the accuracy of the optimal resonant frequency, in some embodiments, the method for determining the excitation signal frequency further includes step S61, step S62, step S63 and step S64.

[0085] Step S61 includes: setting the excitation signal frequency output by the signal processing circuit in the film thickness measuring device to the optimal resonant frequency to obtain a plurality of test signals output by the film thickness measuring device when testing the thickness of a preset standard film group; wherein the standard film group includes a plurality of prefabricated standard films with different thicknesses. In this step, the standard film group may include four standard films with thicknesses of 0 μm, 10 μm, 20 μm, and 30 μm, respectively.

[0086] Step S62 includes: determining, according to the plurality of test signals, actual measurement values ​​corresponding to the film thickness measurement device when testing each standard film.

[0087] Step S63 includes: calculating the error value between each actual measurement value and the thickness of the corresponding standard film, and obtaining a plurality of first error values. In this step, after subtracting the thickness of the corresponding standard film from the actual measurement value, the corresponding first error value can be obtained. For example, when the film thickness measuring device measures a standard film with a thickness of 10 μm, the actual measurement value is 9.8 μm, then the first error value is equal to -0.2 μm (equal to 9.8 μm minus 10 μm).

[0088] Step S64 includes: determining whether each first error value is within a set error range, and if each first error value is within the set error range, determining that the optimal resonant frequency is qualified. The set error range may be -2 μm to 2 μm.

[0089] Furthermore, if there is at least one first error value that is not within the set error range, the optimal resonant frequency is determined to be unqualified, and the optimal resonant frequency can be fine-tuned, or other optional resonant frequencies can be selected to be determined as the optimal resonant frequency, and each time the optimal resonant frequency is re-determined, steps S61 to S64 are executed until the requirements of step S64 are met.

[0090] like Figure 6 As shown, the present invention also provides a terminal device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the method for determining the frequency of an excitation signal provided in an embodiment of the present invention are implemented.

[0091] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0092] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0093] The steps of the method or algorithm described in conjunction with the embodiments disclosed herein may be implemented directly using hardware, a software module executed by a processor, or a combination of the two. The software module may be placed in a random access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0094] It can be understood that the above embodiments only express the preferred implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the patent scope of the present invention. It should be pointed out that, for ordinary technicians in this field, the above technical features can be freely combined without departing from the concept of the present invention, and several deformations and improvements can be made, which all belong to the protection scope of the present invention. Therefore, all equivalent changes and modifications made to the scope of the claims of the present invention should belong to the coverage of the claims of the present invention.

Claims

1. A film thickness measuring device, characterized in that: It comprises a test coil circuit (1), a reference coil circuit (2), an amplifier circuit (3), a signal processing circuit (4) and a housing (5); The housing (5) comprises an opening (51); The test coil circuit (1) comprises a test coil (11) and a first transmission line (12) connected between the test coil (11) and the signal processing circuit (4); the test coil (11) is arranged in the housing (5) and close to the opening (51); the test coil (11) is used to generate a test alternating magnetic field passing through the opening (51) when receiving an excitation signal output by the signal processing circuit (4), and to act on a film to be tested in the test alternating magnetic field, so as to output a test signal according to the thickness of the film to be tested; The reference coil circuit (2) comprises a reference coil (21) and a second transmission line (22) connected between the reference coil (21) and the signal processing circuit (4); the reference coil (21) is arranged in the housing (5) and away from the opening (51); the reference coil (21) is used to generate a reference alternating magnetic field that cannot pass through the opening (51) when receiving an excitation signal output by the signal processing circuit (4), and output a reference signal; The amplifier circuit (3) is connected to the test coil circuit (1), the reference coil circuit (2) and the signal processing circuit (4), and the amplifier circuit (3) is used to perform a differential operation on the test signal and the reference signal to obtain a differential signal, and to perform a phase-locked filtering process on the differential signal based on the frequency of the excitation signal to obtain a phase-locked signal; The signal processing circuit (4) is used to generate an excitation signal of a set frequency and output a test signal according to the phase-locked signal.

2. The thin film thickness measuring device according to claim 1, characterized in that: The test coil (11) and the reference coil (21) are coils having consistent configuration parameters, and the first transmission line (12) and the second transmission line (22) are coaxial lines having consistent configuration parameters.

3. The thin film thickness measuring device according to claim 1, characterized in that: It also includes a magnetic field transmission element (6) and a temperature sensor (7); The magnetic field transmission component (6) is covered on the opening (51); The temperature sensor (7) is arranged in the housing (5) and close to the test coil (11) to output a temperature signal to the signal processing circuit (4) according to the temperature in the housing (5); The signal processing circuit (4) is also used to compensate the test signal according to the temperature signal.

4. The thin film thickness measuring device according to claim 3, characterized in that: The magnetic field transmission element (6) is a microlens; the film thickness measuring device also includes a spacer (8); The spacer (8) is arranged between the test coil (11) and the reference coil (21).

5. The thin film thickness measuring device according to any one of claims 1 to 4, characterized in that: The amplifier circuit (3) comprises a differential amplifier circuit (31) and a phase-locked amplifier circuit (32); The first input end of the differential amplifier circuit (31) is connected to the connection node between the test coil (11) and the first transmission line (12), the second input end is connected to the connection node between the reference coil (21) and the second transmission line (22), and the output end outputs the differential signal to the phase-locked amplifier circuit (32); The phase-locked amplifier circuit (32) is connected to the signal processing circuit (4) to filter out the component of the differential signal whose frequency is different from the frequency of the excitation signal, so as to obtain the phase-locked signal.

6. A method for determining the frequency of an excitation signal, characterized in that: include: An equivalent coil circuit is established based on the test coil circuit or the reference coil circuit in the thin film thickness measuring device according to any one of claims 1 to 5; wherein the equivalent coil circuit includes an equivalent coil and an equivalent transmission line; The equivalent coil is equivalent to an RLC circuit, and coil design parameters are obtained; wherein the coil design parameters include an inductance value, an equivalent capacitance value, and an equivalent resistance value of the equivalent coil; Obtaining a design length of the equivalent transmission line, and dividing the equivalent transmission line equally based on a set unit length to obtain n sub-equivalent lines; wherein n is a positive integer; Each of the sub-equivalent lines is equivalent to an RLC circuit, and sub-equivalent line design parameters are obtained; wherein the sub-equivalent line design parameters include an equivalent inductance value, an equivalent capacitance value, and an equivalent resistance value of each of the sub-equivalent lines; Determine a simulated impedance characteristic curve of the equivalent coil circuit based on the coil design parameters and the sub-equivalent line design parameters; The optimal resonant frequency of the equivalent coil circuit is determined according to the simulated impedance characteristic curve, and the frequency of the excitation signal output by the signal processing circuit in the film thickness measurement device is determined according to the optimal resonant frequency.

7. The method for determining the frequency of an excitation signal according to claim 6, characterized in that: The step of determining the simulated impedance characteristic curve of the equivalent coil circuit based on the coil design parameters and the sub-equivalent line design parameters comprises: Calculating an impedance expression of an equivalent coil circuit based on the coil design parameters and the sub-equivalent line design parameters; Acquiring a resonant frequency setting range of the equivalent coil circuit, and generating a simulated impedance characteristic curve of the equivalent coil circuit according to the resonant frequency setting range and an impedance expression of the equivalent coil circuit; Wherein, the impedance expression of the equivalent coil circuit is: Zc represents the impedance of the equivalent coil, Rc represents the equivalent resistance value of the equivalent coil, Lc represents the inductance value of the equivalent coil, Cc represents the equivalent capacitance value of the equivalent coil, Z1 represents the impedance of the equivalent resistance and equivalent inductance of the sub-equivalent line in series, R represents the equivalent resistance value of the sub-equivalent line, L represents the equivalent inductance value of the sub-equivalent line, C represents the equivalent capacitance value of the sub-equivalent line, Z2 represents the equivalent capacitance impedance of the sub-equivalent line, f represents the excitation signal frequency of the equivalent coil circuit, and Zz represents the impedance of the equivalent coil circuit.

8. The method for determining the frequency of an excitation signal according to claim 7, characterized in that: The step of determining the optimal resonant frequency of the equivalent coil circuit according to the simulated impedance characteristic curve comprises: The impedance variation characteristics in the simulated impedance characteristic curve are analyzed to determine that at least one impedance peak that meets the set requirements appears in the curve, the frequency value corresponding to each impedance peak is defined as an optional resonant frequency, and one of the optional resonant frequencies is determined as the optimal resonant frequency.

9. The method for determining the excitation signal frequency according to claim 8, characterized in that: Also includes: The excitation signal frequency output by the signal processing circuit in the film thickness measuring device is set to the optimal resonance frequency, and a plurality of test signals output by the film thickness measuring device when testing the thickness of a preset standard film group are obtained; wherein the standard film group includes a plurality of prefabricated standard films with different thicknesses; Determine, according to the plurality of test signals, the actual measurement value corresponding to when the thin film thickness measuring device tests each of the standard films; Calculating the error value between each actual measurement value and the thickness of the corresponding standard film to obtain a plurality of first error values; It is determined whether each of the first error values ​​is within a set error range. If each of the first error values ​​is within the set error range, it is determined that the optimal resonant frequency is qualified.

10. A terminal device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method for determining the frequency of an excitation signal according to any one of claims 6 to 9 are implemented.

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