Dielectric constant test system and test method based on charge amplifier

Abstract

The invention discloses a dielectric constant testing system and method based on a charge amplifier, and belongs to the technical field of dielectric constant testing. In order to realize a precise broadband dielectric coefficient test function, the device comprises a test sample piece, a first clamp and a table body, a second clamp is arranged in a stainless steel tank, the test sample piece is placed on the table body, and the table body is an acrylic plate platform of which the top surface is coated with silver; the first clamp tightly contacts with the upper surface of the test sample, and the second clamp tightly contacts with the top surface of the table body; one end of the test signal generator is connected with the first clamp, the other end of the test signal generator is connected with the pre-amplifier, the pre-amplifier is connected with the band-pass filter, the band-pass filter is connected with the reference signal generator and the multiplier, the multiplier is connected with the low-pass filter, and the low-pass filter is connected with the output amplifier. The output amplifier is connected with the charge amplifier which is connected with the second clamp and connected with the signal detector in parallel. According to the invention, the test efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of dielectric constant testing, and particularly relates to a dielectric constant testing system and a testing method based on a charge amplifier. Background Art

[0002] The testing method of dielectric materials is an important means to study the electrical properties of materials. By mainly measuring key parameters such as the dielectric constant and dielectric loss of materials, it reflects the behavior of materials in an electric field and helps to evaluate their applicability in electrical and electronic devices. In recent years, with the rapid development of dielectric ceramics in many high-tech fields such as electronics, communication, energy, audio, and biotechnology, especially the dielectric constant, which represents the ability of a material to store electrical energy. Against the background of the booming development of new energy vehicles, the increasing demand for high-energy storage batteries has put forward higher requirements for materials with high dielectric constants. Therefore, higher demands are put forward for reliable and accurate dielectric testing methods. Through more efficient and accurate dielectric testing, reliable basic data can be provided for material development and engineering applications.

[0003] The main current method for measuring the dielectric constant is the bridge method, which is realized through an impedance analyzer. The working principle is to measure the impedance by balancing the bridge. In the balanced state, the measured impedance is equal to the known impedance of the bridge, so that the value of the measured impedance can be accurately calculated. The bridge uses the relationship between the output voltage and current and utilizes the measured amplitude and phase information to achieve accurate impedance calculation. In addition, the digital bridge method also has an automatic balancing mechanism. The bridge will provide an alternating current signal (usually a sine wave) with a known frequency and amplitude to excite the object to be measured. The comparator will measure the phase difference between the output voltage and current of the bridge to determine whether the bridge is balanced. If it is not balanced, the control element will automatically adjust the internal digital potentiometer, DAC, etc., so as to adjust the size of the known impedance and make the bridge reach the balanced state. However, there are problems such as a relatively narrow measurement frequency range and a significant decrease in the accuracy of the equipment when measuring the dielectric constant at lower frequencies. Summary of the Invention

[0004] The problem to be solved by the present invention is to realize the function of accurate broadband dielectric coefficient testing, and a dielectric constant testing system and a testing method based on a charge amplifier are proposed.

[0005] To achieve the above object, the present invention is realized through the following technical solutions:

[0006] A dielectric constant testing system based on a charge amplifier includes a test signal generator, a reference signal generator, a preamplifier, a band-pass filter, a multiplier, a low-pass filter, an output amplifier, a charge amplifier, a signal detector, a test specimen, a first fixture, a stainless steel tank, a table body, and a second fixture;

[0007] The test sample, the first fixture, the table body, and the second fixture are placed in a stainless-steel tank. The test sample is placed on the table body, and the table body is an acrylic plate platform with a silver-coated top surface;

[0008] The first fixture is in close contact with the upper surface of the test sample, and the second fixture is in close contact with the top surface of the table body;

[0009] One end of the test signal generator is connected to the first fixture, the other end of the test signal generator is connected to a preamplifier, the preamplifier is connected to a band-pass filter, the band-pass filter is respectively connected to a reference signal generator and a multiplier, the multiplier is connected to a low-pass filter, the low-pass filter is connected to an output amplifier, the output amplifier is connected to a charge amplifier, the charge amplifier is connected to the second fixture, and the charge amplifier is connected in parallel with a signal detector.

[0010] Furthermore, both the first fixture and the second fixture are of a steel spring structure.

[0011] Furthermore, the connection method is wire connection, and all the wires are connected using BNC wires.

[0012] A dielectric constant test method based on a charge amplifier is realized relying on the above-mentioned dielectric constant test system based on a charge amplifier, and includes the following steps:

[0013] S1. Connect the above-mentioned dielectric constant test system based on a charge amplifier using BNC wires;

[0014] S2. Set the sensor sensitivity T and the scale factor S on the charge amplifier, and the parameter ranges are as follows:

[0015] T is set to 8.5·10 -9 ~9.1·10 -9 C / Mechanical_unit, and S is set to 9.5 - 10.5Mechanical_unit / V;

[0016] S3. Set the amplitude of the reference signal generator to U;

[0017] S4. Set the excitation frequency of the reference signal generator, then select the time constant of the signal detector, and then measure the voltage of the charge amplifier as U 测 ;

[0018] S5. Adjust the excitation frequency of the reference signal generator and repeat step S4, then calculate the equivalent capacitance C of the test sample according to the calculation formula p , and then calculate the dielectric constant ε r of the test sample. The calculation formulas are as follows:

[0019]

[0020] Among them, d is the thickness of the test specimen, ε 0 is the vacuum permittivity, and s is the surface area of the test specimen.

[0021] Furthermore, the amplitude range of the reference signal generator set in step S3 is 0.995 - 1.005 V.

[0022] Furthermore, the adjustment range of the excitation frequency of the reference signal generator in step S5 is 10 Hz - 102.4 kHz.

[0023] Furthermore, the length of the BNC cable is 0.25 - 1.00 m.

[0024] Advantages of the present invention:

[0025] A dielectric constant test system based on a charge amplifier according to the present invention has a precise broadband dielectric coefficient test function and low cost. The present invention can implement broadband dielectric loss angle and voltage test functions, and combined with calculation formulas, the dielectric coefficient of a sample can be calculated, greatly improving the test efficiency and accelerating the R & D and application processes of dielectric and derivative materials. Description of the Drawings

[0026] Figure 1 is a schematic structural diagram of a dielectric constant test system based on a charge amplifier according to the present invention;

[0027] Figure 2 is a schematic connection diagram of the fixture and the test specimen of the present invention;

[0028] Figure 3 is a comparison diagram of test effects at higher frequencies of the present invention;

[0029] Figure 4 is a comparison diagram of test effects at lower frequencies of the present invention. Detailed Embodiments

[0030] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the specific embodiments described are only a part of the embodiments of the present invention, rather than all of the specific embodiments. The components of the specific embodiments of the present invention usually described and shown in the drawings here can be arranged and designed in various different configurations, and the present invention can also have other embodiments.

[0031] Accordingly, the following detailed description of the specific embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected specific embodiments of the present invention. All other specific embodiments obtained by those skilled in the art based on the specific embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0032] To further understand the content, features and effects of the present invention, the following specific embodiments are exemplified and are accompanied by the attached Figure 1 - attached Figure 4 The details are described as follows:

[0033] Embodiment 1:

[0034] A dielectric constant test system based on a charge amplifier, comprising a test signal generator 1, a reference signal generator 2, a preamplifier 3, a band-pass filter 4, a multiplier 5, a low-pass filter 6, an output amplifier 7, a charge amplifier 8, a signal detector 9, a test specimen 10, a first fixture 11, a stainless steel tank 12, a table body 13, and a second fixture 14;

[0035] The test specimen 10, the first fixture 11, the table body 13, and the second fixture 14 are placed inside the stainless steel tank 12. The test specimen 10 is placed on the table body 13, and the table body 13 is an acrylic plate platform with a silver-coated top surface;

[0036] The first fixture 11 is in close contact with the upper surface of the test specimen 10, the second fixture 14 is in close contact with the top surface of the table body 13, and then the lower surface of the test specimen 10 is conductively connected through the top surface of the table body 13;

[0037] One end of the test signal generator 1 is connected to the first fixture 11, the other end of the test signal generator 1 is connected to the preamplifier 3, the preamplifier 3 is connected to the band-pass filter 4, the band-pass filter 4 is respectively connected to the reference signal generator 2 and the multiplier 5, the multiplier 5 is connected to the low-pass filter 6, the low-pass filter 6 is connected to the output amplifier 7, the output amplifier 7 is connected to the charge amplifier 8, the charge amplifier 8 is connected to the second fixture 14, and the charge amplifier 8 is connected in parallel with the signal detector 9.

[0038] Furthermore, both the first fixture 11 and the second fixture 14 are steel spring structures.

[0039] Furthermore, the connection method is wire connection, and all the wires are connected using BNC cables.

[0040] Furthermore, the technical parameters of the test signal generator 1 are that it can generate sine and cosine waves, the set adjustment frequency range is 10 Hz to 102.4 KHz, and the output amplitude range is 0.01 V to 5.00 V;

[0041] Furthermore, the technical parameters of the reference signal generator 2 are that it can generate sine and cosine waves, and the set adjustment frequency range is 10 Hz to 102.4 KHz, and the output amplitude range is 0.01 V to 5.00 V;

[0042] Furthermore, the model of the preamplifier 3 is OPA627AM;

[0043] Furthermore, the technical parameters of the band-pass filter 4 are that the dynamic reserve > 100 dB;

[0044] Furthermore, the model of the multiplier 5 is AD630AD;

[0045] Furthermore, the model of the low-pass filter 6 is NE5532AI;

[0046] Furthermore, the technical parameters of the output amplifier 7 are that the amplification factor is 1 to 1000 times and the gain accuracy is ±1%;

[0047] Furthermore, the model of the charge amplifier 8 is KISTLER Type 5011;

[0048] Furthermore, the model of the signal detector 9 is SDS1000X-E.

[0049] For a dielectric constant test system based on a charge amplifier described in this embodiment, the noise reduction principle is as follows:

[0050] In the circuit, the output signal of the signal generator to be measured can be defined as:

[0051]

[0052] Among them, S 1 (t) is the AC signal to be measured, with an amplitude of U 1 、angular frequency of ω, and phase of B is the total noise, and B is very weak compared to U 1 The main principle is to provide an excitation frequency to excite the sample to be measured, and the sample generates corresponding signal characteristics, and then outputs through the signal generator to be measured; the reference signal generator generates a reference AC signal, which is defined as follows:

[0053] Two-channel sine reference signals:

[0054]

[0055] First, it enters the multiplier for multiplication operation, and then performs sum-to-product and difference-to-product. Then, the signal to be measured and the reference signal S R enter the low-pass filter, and the signal to be measured is filtered by means of the reference signal, and then after passing through the output amplifier, the following can be obtained:

[0056]

[0057] Among them, U R is the reference signal amplitude;

[0058] Since the amplitude of the reference signal can be adjusted, for the sake of simplicity in calculation, we select a value equal to the amplitude of the signal to be measured. Then, the amplitude R and phase of the signal to be measured

[0059]

[0060]

[0061] Among them, δ is the dielectric loss angle; the dielectric material to be measured can be equivalent to a capacitor C p and a resistor R p in parallel in the circuit diagram. By means of the above two measurement parameters, its relative dielectric constant ε r and the dielectric loss tanδ can be obtained, and their relationship is:

[0062]

[0063] Among them, d is the thickness of the material to be measured, s is the effective area of the material, and ε 0 is the vacuum permittivity;

[0064] In the circuit, the signal generator applies a voltage in the circuit. After passing through the filter, the voltage signal is characterized as U, so that the charge amplifier and the material to be measured are respectively subjected to the measurement voltage U 测 and the voltage U p . Among them, since the resistance of the charge amplifier is much smaller than that of the sample to be measured, U p can be approximated as the initial set voltage U of the signal generator (set to 0.995 - 1.005V in the experiment). Through the sensor sensitivity T and the scaling factor S set by the charge amplifier, and the measurement voltage U 测 , the charge at both ends of the sample to be measured can be calculated, and then through the voltage U p at both ends of it, its capacitance can be further obtained.

[0065] By setting the time constant of the signal detector and the excitation frequency f of the reference signal generator, where the time constant determines the detection frequency of the signal detector. The shorter the time, the faster the measurement speed, but due to the fewer data selected, the error will also be larger. Usually during the test, the time constant is set to 6πf - 20πf. Often, the dielectric constant characterized by the sample to be measured is inconsistent at different excitation frequencies, so it is necessary to excite the sample one by one from low frequency to relatively high frequency (usually from 10Hz to 100kHz) to comprehensively understand the dielectric properties of the sample.

[0066] Affected by the phase transition in the circuit, the actual dielectric loss angle δ is as follows:

[0067]

[0068] Example 2:

[0069] A method for measuring the dielectric constant based on a charge amplifier is realized relying on the system for measuring the dielectric constant based on a charge amplifier described in Example 1, and includes the following steps:

[0070] S1. Connect the system for measuring the dielectric constant based on a charge amplifier well using a BNC cable;

[0071] S2. Set the sensor sensitivity T and the scale factor S on the charge amplifier, and the parameter ranges are as follows:

[0072] T is set to 8.5·10 -9 ~9.1·10 -9 C / Mechanical_unit, and S is set to 9.5~10.5Mechanical_unit / V;

[0073] S3. Set the amplitude of the reference signal generator to U;

[0074] Furthermore, the range of setting the amplitude of the reference signal generator in step S3 is 0.995V~1.005V.

[0075] S4. Set the excitation frequency of the reference signal generator, then select the time constant of the signal detector, and then measure the voltage of the charge amplifier as U 测 ;

[0076] S5. Adjust the excitation frequency of the reference signal generator and repeat step S4, then calculate the equivalent capacitance C of the test sample according to the calculation formula p , and then calculate the dielectric constant ε r of the test sample, and the calculation formula is as follows:

[0077]

[0078] Among them, d is the thickness of the test sample, ε 0 is the vacuum permittivity, and s is the surface area of the test sample.

[0079] Furthermore, the adjustment range of the excitation frequency of the reference signal generator in step S5 is 10Hz~102.4kHz.

[0080] Furthermore, the length of the BNC cable is 0.25m~1.00m.

[0081] The specific implementation effects of this embodiment are as follows:

[0082] Sapphire with a thickness d = 0.22 mm and a radius r = 5.00 mm was taken as the experimental object. In the experiment, the parameters of the charge amplifier were set as follows:

[0083] T = 9·10 -9 C / Mechanical_unit, S = 10 Mechanial_unit / V;

[0084] By testing different excitation frequencies of the same sample and comparing the charge amplifier method and the bridge method, where the bridge method uses the Tonghui TH2838 impedance tester. The experimental data comparison is as Figure 3 shown, Figure 3 where the ordinate in represents the dielectric constant ε r . It can be seen that the accuracy of the charge amplifier method is basically the same as that of the bridge method, proving the reliability of the charge amplifier method.

[0085] The test results at low frequencies are as Figure 4 shown. It can be seen that there are large deviations in the results obtained by the bridge method, and the lowest test frequency of the bridge method instrument is 20 Hz, while the charge amplifier method can measure the dielectric parameters at lower frequencies. It can be seen that the performance of the charge amplifier method is better at low frequencies.

[0086] It should be noted that relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of another identical element in the process, method, article or device including the element.

[0087] Although the present application has been described above with reference to specific embodiments, various improvements can be made thereto and components thereof can be replaced with equivalents without departing from the scope of the present application. In particular, as long as there is no structural conflict, the features in the specific embodiments disclosed in the present application can be combined with each other in any way, and the exhaustive description of these combinations is not given in this specification only for the sake of saving space and resources. Therefore, the present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A dielectric constant test system based on a charge amplifier, characterized in that: It comprises a test signal generator (1), a reference signal generator (2), a preamplifier (3), a bandpass filter (4), a multiplier (5), a low-pass filter (6), an output amplifier (7), a charge amplifier (8), a signal detector (9), a test sample (10), a first fixture (11), a stainless steel tank (12), a platform (13), and a second fixture (14); The test sample (10), the first fixture (11), the platform (13), and the second fixture (14) are placed in a stainless steel tank (12), and the test sample (10) is placed on the platform (13), and the platform (13) is an acrylic plate platform with a silver-coated top surface; The first clamp (11) is in close contact with the upper surface of the test sample (10), and the second clamp (14) is in close contact with the bottom surface of the platform (13); One end of the test signal generator (1) is connected to a first fixture (11), and the other end of the test signal generator (1) is connected to a preamplifier (3), the preamplifier (3) is connected to a bandpass filter (4), the bandpass filter (4) is respectively connected to a reference signal generator (2) and a multiplier (5), the multiplier (5) is connected to a low-pass filter (6), the low-pass filter (6) is connected to an output amplifier (7), the output amplifier (7) is connected to a charge amplifier (8), the charge amplifier (8) is connected to a second fixture (14), and the charge amplifier (8) is connected in parallel to a signal detector (9).

2. A dielectric constant test system based on a charge amplifier according to claim 1, characterized in that: The first clamp (11) and the second clamp (14) are both steel spring structures.

3. The dielectric constant testing system based on charge amplifier according to claim 1, characterized in that: The connection method adopts wire connection, and the wires are all connected using BNC lines.

4. A dielectric constant test method based on a charge amplifier, implemented by a dielectric constant test system based on a charge amplifier according to any one of claims 1 to 3, characterized in that: The steps include: S1. Use a BNC cable to connect the charge amplifier-based dielectric constant test system; S2. Set the sensor sensitivity T and scale factor S on the charge amplifier. Set the parameter range as follows: T is set to 8.5·10 -9 ~9.1·10 -9 C / Mechanical_unit, S is set to 9.5~10.5Mechanical_unit / V; S3. Set the amplitude of the reference signal generator to U; S4. Set the excitation frequency of the reference signal generator, then select the time constant of the signal detector, and then measure the voltage of the charge amplifier as U 测 ; S5. Adjust the excitation frequency of the reference signal generator and repeat step S4, then calculate the equivalent capacitance C of the test sample according to the calculation formula p , and then calculate the dielectric constant ε of the test sample r , the calculation formula is as follows: Where d is the thickness of the test sample, ε0 is the vacuum dielectric constant, and s is the surface area of ​​the test sample.

5. The dielectric constant testing method based on a charge amplifier according to claim 4, characterized in that: In step S3, the amplitude of the reference signal generator is set to range from 0.995V to 1.005V.

6. The dielectric constant testing method based on a charge amplifier according to claim 5, characterized in that: The adjustment range of the excitation frequency of the reference signal generator in step S5 is 10 Hz to 102.4 kHz.

7. The method for testing dielectric constant based on charge amplifier according to claim 6, characterized in that: The length of the BNC line is 0.25m to 1.00m.

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