System and method for measuring dielectric constant of liquid based on RC (Resistance-Capacitance) transient state

Abstract

The invention belongs to the technical field of electronic measurement, and particularly relates to a liquid dielectric constant measuring system and method based on an RC transient state. The measuring system comprises a liquid storage container, a measuring circuit, a signal processor and a display terminal, the measuring circuit comprises a parallel-plate capacitor, two polar plates of the parallel-plate capacitor are respectively fixed on opposite inner walls of the liquid storage container, the parallel-plate capacitor is connected with the signal processor, and the signal processor is connected with the display terminal; to-be-detected liquid is injected into the liquid storage container, the parallel plate capacitor is controlled to be charged, the signal processor collects transient voltage-time original data in the charging process of the parallel plate capacitor and transmits the collected data to the display terminal, the display terminal processes the transient voltage-time original data based on an RC zero-state response algorithm, and the display terminal displays the processed transient voltage-time original data. And obtaining and displaying the dielectric constant of the to-be-measured liquid. According to the invention, high-precision, rapid and low-cost liquid dielectric constant measurement can be realized.

Description

Technical Field

[0001] This invention belongs to the field of electronic measurement technology, and particularly relates to a liquid dielectric constant measurement system and method based on RC transient. Background Technology

[0002] The dielectric constant is an important physical parameter reflecting the dielectric properties of a material. It describes the material's polarization ability under the influence of an electric field and is closely related to its energy storage performance, electromagnetic wave propagation characteristics, and signal transmission features. Accurate measurement of the dielectric constant of liquids has significant applications in electromagnetic material detection, chemical sensing, environmental monitoring, pharmaceutical analysis, and industrial process control. For example, changes in the dielectric constant can be used to determine the composition, purity, and mixing ratio of a liquid, making it an important technical means for oil quality testing, liquid contamination monitoring, and solution characteristic analysis.

[0003] Currently, the measurement of the dielectric constant of liquids mainly relies on detection instruments based on principles such as the resonance method, the bridge method, and the capacitance method. Among them, the resonance method has high accuracy, but the measurement process is complex and requires high environmental stability; the bridge method is sensitive to circuit balance conditions, is cumbersome to operate, and is not easy to automate; while the conventional capacitance method mostly adopts a steady-state measurement mode, inferring the dielectric constant from the static capacitance value, but its testing time is long, its anti-interference ability is poor, and its ability to resolve small capacitance changes is limited. Therefore, traditional methods cannot simultaneously achieve high accuracy, fast response, and system simplicity.

[0004] Several key technical challenges exist in measuring the dielectric constant of liquids. First, there's the issue of high-precision measurement. The dielectric constant of liquids often fluctuates with minute changes in temperature, humidity, and concentration. Insufficient response speed or sampling resolution of the test circuit can easily lead to accumulated measurement errors. Second, there's the dynamic response characteristic. Traditional steady-state methods neglect the time characteristics of the RC charging and discharging transient process, which actually contains crucial information about the interaction between the material's polarization rate and the electric field. Establishing a precise mathematical relationship between the RC transient response and dielectric properties is a technical bottleneck for achieving high-sensitivity measurement. The third challenge is signal acquisition and noise reduction design. Extracting capacitor discharge characteristic signals on a nanosecond timescale places extremely high demands on the timing control and noise suppression capabilities of the sampling circuit. External electromagnetic interference, cable parasitic effects, and device errors can all affect the final results. Finally, the design of the sensor structure is equally crucial. The selection of the liquid reservoir, bipolar capacitor, and electrode materials directly affects the repeatability and stability of the measurement. For example, minute changes in electrode surface roughness or liquid flow state can cause measurement deviations. Summary of the Invention

[0005] In view of this, the present invention aims to provide a liquid dielectric constant measurement system and method based on RC transients, so as to solve the obvious shortcomings of the existing technology in terms of accuracy, speed, complexity and applicability. The present invention can achieve high-precision, fast and low-cost liquid dielectric constant measurement.

[0006] To achieve the above objectives, the technical solution created by this invention is implemented as follows: A liquid dielectric constant measurement system based on RC transients includes a liquid storage container, a measurement circuit, a signal processor, and a display terminal. The measurement circuit includes a parallel plate capacitor, and the two plates of the parallel plate capacitor are respectively fixed on the opposite inner walls of the liquid storage container. The parallel plate capacitor is connected to the signal processor, and the signal processor is connected to the display terminal. The liquid to be tested is injected into the storage container. The liquid to be tested comes into contact with the two plates of the parallel plate capacitor. The parallel plate capacitor is controlled to charge. The signal processor collects the raw transient voltage-time data during the charging process of the parallel plate capacitor and transmits the collected data to the display terminal. The display terminal processes the raw transient voltage-time data based on the RC zero-state response algorithm to obtain and display the dielectric constant of the liquid to be tested.

[0007] Furthermore, the liquid storage container is also equipped with an injection port and a pressure balance port. The injection port is used to inject the liquid to be tested, and the pressure balance port is used to discharge the liquid and eliminate the pressure resistance of the liquid storage container during injection and discharge.

[0008] Furthermore, the parallel plate capacitor has a wiring port on each of its two plates, and the liquid storage container has a through hole corresponding to each wiring port. The wiring port extends through the through hole to the outer wall of the liquid storage container, thereby realizing the electrical connection between the parallel plate capacitor and the signal processor.

[0009] Furthermore, the signal processor is a PC virtual oscilloscope, which includes an A acquisition interface and a B acquisition interface.

[0010] Furthermore, the measurement circuit also includes a DC regulated power supply, a first switch, a second switch, a first resistor, and a second resistor. One end of the parallel plate capacitor is connected to the negative terminal of the DC regulated power supply, and the other end of the parallel plate capacitor is connected to one end of the first resistor. The other end of the first resistor is connected to the positive terminal of the DC regulated power supply through the first switch. One end of the second resistor is connected to one end of the parallel plate capacitor, and the other end of the second resistor is connected to the other end of the parallel plate capacitor through the second resistor. The two ends of the A acquisition interface of the PC virtual oscilloscope are connected across the positive and negative terminals of the DC regulated power supply. One end of the B acquisition interface of the PC virtual oscilloscope is connected to the connection point of the parallel plate capacitor and the second switch, and the other end of the B acquisition interface of the PC virtual oscilloscope is connected to the connection point of the parallel plate capacitor and the second resistor.

[0011] A method for measuring the dielectric constant of a liquid based on RC transient states is implemented using an RC transient state-based liquid dielectric constant measurement system, and specifically includes the following steps: S1: Build a liquid dielectric constant measurement system based on RC transient and inject the liquid to be measured into the storage container; S2: Controls the charging of the parallel plate capacitor. The signal processor collects the transient voltage-time raw data during the charging process of the parallel plate capacitor and transmits the collected data to the display terminal. S3: The display terminal processes the transient voltage-time raw data based on the RC zero-state response algorithm to obtain and display the dielectric constant of the liquid under test.

[0012] Furthermore, step S3 specifically includes: S31: Use 50% of the voltage output by the DC regulated power supply of the measurement circuit as the reference threshold. S32: In the raw transient voltage-time data, the time corresponding to the reference threshold is taken as the half-response time, and the difference between the start time and the half-response time is taken as the half-response period. S33: Calculate the dielectric constant of the liquid to be tested using the following formula. : ; Where d is the distance between the two plates of the parallel plate capacitor. Let be the dielectric constant of the liquid being tested. is the vacuum dielectric constant; S is the area of ​​the two plates facing each other in the parallel plate capacitor; Δt is the half-response time period; and R is the resistance of the first resistor.

[0013] Compared with the prior art, the present invention can achieve the following beneficial effects: (1) The liquid dielectric constant measurement system and method based on RC transient response described in this invention effectively avoids the defects of existing technologies. By analyzing the transient process of RC charging and discharging, a direct mathematical mapping relationship is established between the liquid dielectric constant and the time constant. It does not rely on complex high-frequency systems or steady-state equilibrium conditions. During measurement, only the time when the voltage reaches the half-response point needs to be recorded to deduce the dielectric constant of the liquid, which greatly simplifies the hardware structure. This invention has the advantages of fast response speed, strong anti-interference ability, simple system structure, low cost, and wide applicability. It can complete high-sensitivity measurement with nanosecond-level time accuracy. In addition, the measurement principle based on RC transient response of this invention has both theoretical innovation and engineering feasibility, providing a new technical approach for achieving high-precision, fast, and low-cost liquid dielectric constant measurement.

[0014] (2) The liquid dielectric constant measurement system and method based on RC transient described in this invention, in terms of qualitative analysis, uses a simple cuboid model liquid storage container and is equipped with a bipolar capacitor. This invention uses copper as the electrode material, and by reducing the distance between the two electrodes, the edge effect is effectively suppressed, thereby reducing system error; by compressing the distance between the two electrodes, the container is filled with as little target liquid as possible, thereby reducing the amount of sample used. In addition, this invention has low cost, is easy to produce, and is simple to operate, enabling rapid measurement and analysis of the dielectric constant of the target liquid.

[0015] (3) The liquid dielectric constant measurement system and method based on RC transients described in this invention, in terms of quantitative analysis, when processing the measured values ​​of bipolar capacitors, innovatively uses the "RC zero-state response algorithm", introduces new concepts such as "response degree" and "half-response time period", and combines relevant theoretical knowledge such as RC transient response, Gauss's theorem, and differential equations to derive a dielectric constant calculation formula with high accuracy. The advantage of this dielectric constant calculation formula is that it only requires obtaining the half-response time period Δ of the zero-state response of the constructed circuit. t By combining the various scalar values ​​of the product, the capacitance value of the capacitor using the target liquid as the dielectric can be calculated. Therefore, this method for solving the dielectric constant of the target liquid is simple and highly accurate. This invention, as a data processing and analysis method for a novel liquid dielectric constant measurement technology product, enhances the product's utilization value to some extent. Attached Figure Description

[0016] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 A cross-sectional view of the liquid storage container described in the embodiment of the present invention; Figure 2 A side view of the liquid storage container described in an embodiment of the present invention; Figure 3 A schematic diagram of the measurement circuit described in the embodiment of the present invention; Figure 4 A schematic flowchart of the liquid dielectric constant measurement method based on RC transients as described in the embodiments of the present invention; Figure 5 The embodiments described in this invention U - t curve.

[0017] Explanation of reference numerals in the attached figures: 1. Liquid storage container; 2. Electrode plate; 3. Wiring port; 4. Liquid filling port; 5. PC virtual oscilloscope; 6. Display terminal; V, DC regulated power supply; R, first resistor; R1, second resistor; C, parallel plate capacitor; S1, first switch; S2, second switch. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the 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 merely illustrative of the invention and do not constitute a limitation thereof.

[0019] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0020] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0021] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0023] This invention is based on the RC transient response theory, which states that during the charging and discharging process of an RC circuit, there is a clear exponential relationship between voltage and time, and the capacitance directly affects the response time constant τ=RC. Therefore, as long as the half-response period (the time required for the voltage to reach half of its steady-state value) during charging or discharging can be measured with high precision, the capacitance value can be deduced, and thus the dielectric constant of the liquid can be calculated. This invention overcomes the limitations of traditional steady-state capacitance measurement by introducing time-domain analysis into dielectric parameter determination, providing a new solution for the real-time measurement of the dielectric constant of liquids.

[0024] At the implementation level, the challenges of existing technologies mainly focus on two aspects: First, how to transform theoretical formulas into practically measurable circuit models. This requires designing RC circuits that balance stability and sensitivity, ensuring that the half-response time can be clearly distinguished within a finite timeframe for the charge-discharge curve. Second is the signal extraction and processing problem. Because RC transient changes are extremely rapid, typically on the order of microseconds or even nanoseconds, high-sampling-rate data acquisition systems or virtual oscilloscopes are necessary for signal acquisition, and key time parameters must be accurately extracted using software algorithms. Furthermore, to ensure measurement repeatability, the structural design must address the influence of factors such as liquid filling, venting, and temperature compensation on the capacitive response. During operation, the discharge time of the parallel-plate capacitor C can be accurate to the nanosecond level, and the accuracy of measuring the dielectric constant of the liquid can reach at least two decimal places as currently required.

[0025] In summary, liquid dielectric constant measurement technology is currently transitioning from traditional steady-state measurement to high-speed transient measurement. This invention, based on the measurement principle of RC transient response, combines theoretical innovation with engineering feasibility, providing a new technical approach for achieving high-precision, rapid, and low-cost liquid dielectric constant measurement.

[0026] like Figures 1-2 As shown, the present invention proposes a liquid dielectric constant measurement system based on RC transient, including a liquid storage container 1, a measurement circuit, a signal processor and a display terminal 6. The measurement circuit includes a parallel plate capacitor C, and the two plates 2 of the parallel plate capacitor C are respectively fixed on the opposite inner walls of the liquid storage container 1. The parallel plate capacitor C is connected to the signal processor, and the signal processor is connected to the display terminal 6. The liquid to be tested is injected into the storage container 1. The liquid to be tested comes into contact with the two plates 2 of the parallel plate capacitor C. The parallel plate capacitor C is controlled to charge. The signal processor collects the transient voltage-time raw data during the charging process of the parallel plate capacitor C and transmits the collected data to the display terminal 6. The display terminal 6 processes the transient voltage-time raw data based on the RC zero-state response algorithm to obtain and display the dielectric constant of the liquid to be tested.

[0027] The charging time of the parallel plate is on the order of nanoseconds, and the charging test process is generally completed within a few hundred nanoseconds. Therefore, the discharge of the parallel plate can be carried out at an appropriate time after the charging switch is closed, according to the actual test requirements. If the user uses an automated electronic switch, the opening and closing interval of the two switches needs to be set to 1 microsecond to ensure complete discharge.

[0028] It should be noted that this invention innovatively adopts the concept of RC transient circuit, derives the relationship between the capacitance value, discharge time, and dielectric between the two plates of the parallel plate capacitor C, designs a measurement circuit, improves data processing efficiency, makes operation simpler, lowers cost, improves stability, and increases measurement accuracy. During operation, the discharge time of the capacitor can be accurate to the nanosecond level, and the accuracy of measuring the dielectric constant of the liquid can reach at least two decimal places as currently required.

[0029] Furthermore, the measurement circuit is a DC RC circuit, consisting of a 10V DC regulated power supply V, a parallel plate capacitor C, two 1000Ω resistors (the first resistor R and the second resistor R1), and two switches (the first switch S1 and the second switch S2) connected in a mixed configuration. The parallel plate capacitor C is charged or discharged by controlling the closing or opening of the switches. The parallel plate capacitor C is fixed inside the liquid storage container 1, and its upper and lower plates 2 are respectively fixed to the upper and lower surfaces of the inner wall of the liquid storage container 1. The length and width of the plates 2 are smaller than the length and width of the liquid storage container 1. The measurement circuit is connected to the signal processor, and the signal processor transmits data to the display terminal 6 via USB.

[0030] Furthermore, the liquid storage container 1 is made of quartz glass and has a four-sided closed cuboid structure. The upper and lower plates 2 of the parallel plate capacitor C are respectively attached to the upper and lower surfaces inside the liquid storage container 1.

[0031] In some embodiments, the liquid storage container 1 is further provided with an injection port 4 and a pressure balance port. The injection port 4 is used to inject the liquid to be tested, and the pressure balance port is used to discharge the liquid and eliminate the pressure resistance of the liquid storage container 1 during injection and discharge.

[0032] Furthermore, the side wall of the liquid storage container 1 is provided with an external liquid injection port 4, and the rear wall of the liquid storage container 1 is provided with a pressure balance port.

[0033] In some embodiments, the two plates 2 of the parallel plate capacitor C are respectively provided with wiring ports 3, and the liquid storage container 1 is provided with through holes corresponding to each wiring port 3. The wiring ports 3 extend through the through holes to the outer wall of the liquid storage container 1 to realize the electrical connection between the parallel plate capacitor C and the signal processor.

[0034] Furthermore, the two plates 2 of the parallel plate capacitor C are two copper plates, and the parallel plate capacitor C is connected to the measurement circuit through the wiring ports 3 respectively set in the middle of the upper and lower plates 2.

[0035] In some embodiments, the signal processor is a PC virtual oscilloscope 5, which includes an A acquisition interface and a B acquisition interface.

[0036] Furthermore, the PC virtual oscilloscope 5 is used to collect voltage and time data of the parallel plate capacitor C during the charging process, and transmits it to the display terminal 6 for processing and analysis.

[0037] In some embodiments, such as Figure 3 As shown, the measurement circuit also includes a DC regulated power supply V, a first switch S1, a second switch S2, a first resistor R, and a second resistor R1. One end of the parallel plate capacitor C is connected to the negative terminal of the DC regulated power supply V, and the other end of the parallel plate capacitor C is connected to one end of the first resistor R. The other end of the first resistor R is connected to the positive terminal of the DC regulated power supply V through the first switch S1. One end of the second resistor R1 is connected to one end of the parallel plate capacitor C, and the other end of the second resistor R1 is connected to the other end of the parallel plate capacitor C through the second resistor R1. The two ends of the A acquisition interface of the PC virtual oscilloscope 5 are connected across the positive and negative terminals of the DC regulated power supply V. One end of the B acquisition interface of the PC virtual oscilloscope 5 is connected to the connection point of the parallel plate capacitor C and the second switch S2. The other end of the B acquisition interface of the PC virtual oscilloscope 5 is connected to the connection point of the parallel plate capacitor C and the second resistor R1.

[0038] It should be noted that the measurement circuit includes a one-closed-two-open charging circuit and a one-open-two-closed discharging circuit. The one-closed-two-open charging circuit is a series charging circuit consisting of a parallel plate capacitor C powered by a DC regulated power supply V and a kiloohm resistor. The function of the one-closed-two-open charging circuit is to transmit the Ut data during the charging process to the signal processor, and then send it to the display terminal 6 for processing. The one-open-two-closed discharging circuit is used to discharge the fully charged capacitor in the one-closed-two-open charging circuit to prepare for the next charging.

[0039] like Figure 4 As shown, this invention provides a liquid dielectric constant measurement method based on RC transients, implemented using a liquid dielectric constant measurement system based on RC transients, specifically including the following steps: S1: Build a liquid dielectric constant measurement system based on RC transient and inject the liquid to be measured into the liquid storage container 1; S2: Control the charging of parallel plate capacitor C. The signal processor collects the transient voltage-time raw data during the charging process of parallel plate capacitor C and transmits the collected data to the display terminal 6. S3: Display terminal 6 processes the transient voltage-time raw data based on the RC zero-state response algorithm to obtain and display the dielectric constant of the liquid under test.

[0040] The signal processor refers to a high-performance oscilloscope. This invention does not specify a particular oscilloscope model, as long as it can recognize nanosecond time signals. The high-performance oscilloscope records voltage-time data during the circuit's charging process, obtaining a charging curve Ut, and transmits this charging curve data to the display terminal 6.

[0041] Furthermore, step S3 specifically includes: S31: Use 50% of the voltage output by the DC regulated power supply V of the measuring circuit as the reference threshold. S32: In the raw transient voltage-time data, the time corresponding to the reference threshold is taken as the half-response time, and the difference between the start time and the half-response time is taken as the half-response period. S33: Calculate the dielectric constant of the liquid to be tested using the following formula. : ; Where d is the distance between the two plates 2 of the parallel plate capacitor C. Let be the dielectric constant of the liquid being tested. denoted as the vacuum dielectric constant; S is the area of ​​the two plates 2 facing each other in the parallel plate capacitor C; Δt is the half-response time interval; and R is the resistance value of the first resistor R.

[0042] Example 1: The liquid dielectric constant measurement system based on RC transient proposed in this invention includes a liquid storage container 1, a measurement circuit, a signal processor, and a display terminal 6. The measurement circuit is a DC RC circuit, which consists of a 10V DC regulated power supply V, a parallel plate capacitor C, two 1000Ω resistors, and two switches connected in a mixed configuration. The charging or discharging of the parallel plate capacitor C is achieved by controlling the closing or opening of the switches. The measurement circuit is connected to the signal processor, and the signal processor and the display terminal 6 transmit data via USB.

[0043] The measurement circuit consists of two parts. The first part is a "one-closed, two-open" charging circuit, also known as a capacitor zero-state response circuit. This circuit is a series charging circuit composed of a parallel plate capacitor C powered by a DC power supply and a kiloohm resistor. The function of the "one-closed, two-open" charging circuit is to transmit the Ut data during the charging process to the PC virtual oscilloscope 5, and then to the display terminal 6 for processing. The other part is a "one-open, two-closed" discharging circuit, also known as a zero-input response circuit. The function of the "one-open, two-closed" discharging circuit is to discharge the fully charged capacitor in the first part, preparing it for the next charging.

[0044] The liquid storage container 1 is made of quartz glass and is a glass container measuring 110mm × 110mm × 30mm. Considering the volatility of some liquids, in order to ensure that the container is always full, the present invention adopts a rectangular structure with four closed sides, and the upper and lower plates 2 of the parallel plate capacitor C are respectively attached to the upper and lower surfaces inside the liquid storage container 1.

[0045] In this design, the parallel-plate capacitor C consists of two copper plates measuring 100mm × 100mm × 1mm. Because plate 2 will be in contact with the liquid during measurement, and copper plates possess high corrosion resistance and strong conductivity, as well as higher thermal conductivity, better heat dissipation, and better ductility compared to other metals, the copper plates can be made thinner under the same safety factor conditions. This allows for maximizing the parallelism of the two plates 2, reducing measurement errors in the dielectric constant caused by edge effects and non-parallelism of the plates.

[0046] The parallel plate capacitor C is connected to the measuring circuit through a 6mm diameter terminal 3 located in the middle of the upper and lower plates 2.

[0047] The side wall of the liquid storage container 1 is provided with a 10mm external injection port 4 for liquid injection and discharge. The rear wall of the liquid storage container 1 is provided with a 3mm diameter air pressure balance port (vent hole) to facilitate liquid injection and discharge.

[0048] The signal processor is a PC virtual oscilloscope 5, which is used to collect data such as voltage and time of the parallel plate capacitor C during the charging process and transmit it to the display terminal 6 for processing and analysis.

[0049] The theoretical derivation of the formula for calculating the dielectric constant of the liquid between the upper and lower plates 2 of a parallel plate capacitor C is as follows: Based on the potential distribution and Gaussian distribution of the parallel-plate capacitor C, the determining formula for the parallel-plate capacitor C can be derived: ; in, d The distance between parallel plates; The dielectric constant of the inter-plate insulating material; ρ is the dielectric constant in vacuum; in this embodiment, its value is 8.854 × 10⁻⁶. -12 C 2 / N·m 2 ; S The area of ​​the two electrodes 2 facing each other is [area missing]. In this embodiment, the upper and lower electrodes 2 are made of copper, each 100mm long and wide, and 1mm thick. The distance between the two electrodes is [area missing]. d =18mm.

[0050] From the above formula, we get: ; Therefore, to obtain the dielectric constant, we only need to determine the capacitance value. Theoretical derivation proves that the capacitance value and the RC zero-state response (charging process) satisfy the following: ; In the formula, m It refers to the charging level (0 < 0). m <1).

[0051] when m When the value is 1 / 2, the capacitance C and the half-response time Δ t The relationship between them is: ; The expression for the dielectric constant of the inter-plate insulating material ( ) with capacitance value and half-response time Δ t Combining the relationships, we obtain the expression for the dielectric constant of the interplate medium: ; In summary, by simply loading the liquid to be tested into the liquid dielectric constant measurement system based on RC transients and charging and discharging it, and finding the half-response period, the dielectric constant of the liquid to be tested can be determined given the known plate spacing and the area of ​​the plates facing each other in the measurement system.

[0052] In this embodiment, zero-state response refers to the circuit response (charging response) generated solely by external power supply excitation when the circuit is in a zero initial state (i.e., the initial energy of the energy storage element is zero). The measurement circuit transmits the instantaneous charging data to the signal processor (PC virtual oscilloscope 5). The PC virtual oscilloscope 5 identifies the half-response period of the charging degree from the extracted image information; it calculates the dielectric constant of the liquid under test using the dielectric constant expression of the interplate medium, where, d For the spacing between boards, The dielectric constant of the inter-plate insulating material. ρ is the dielectric constant in vacuum; in this embodiment, its value is 8.854 × 10⁻⁶. -12 C 2 / N·m 2 ; S The area of ​​the parallel plates facing each other is [area value missing]. In this embodiment, the upper and lower plates 2 are made of copper, each 100mm long and wide, and 1mm thick. The distance between the two plates is [area value missing]. d =18mm, Δ t This is a half-response period.

[0053] Next, we will conduct experimental calculations and algorithm error analysis: Given that the dielectric constant of pure water is 80.1, the method for measuring the dielectric constant of liquids provided by this invention is compared with two traditional methods for measuring dielectric constant, and the magnitude of random errors in the calculation results is analyzed.

[0054] (1) Linear fitting method The charging response equation is Where U is 10V. Rearranging terms and exponentiation to form the following: At this point, the equation is transformed into a linear equation with time t, so that... Using t as the dependent variable, perform a linear fit on time t.

[0055] In MATLAB software, the linear fitting equation for the response data is as follows: ; Where, let f(t) = Fit coefficients , ; Then capacitor The following can be derived using the definition of capacitance: .

[0056] Analysis using the goodness-of-fit test method shows that: Random error SSE: 0.01217; Sample coefficient of determination R 2: 0.9999; Root Mean Square Error (RMSE): 0.006934; Substitute the data as follows: ; The relative error is (82.41-80.1) / 80.1=2.88%, which is within the allowable error range.

[0057] (2) Time constant measurement method like Figure 5 As shown, a COMSOL simulation was performed: First, a physical model of a parallel-plate capacitor C was built. Then, this model was connected to the charging circuit of the measurement circuit, and calculations were performed using electromagnetic physics fields. The simulation results include potential distribution diagrams, U - t probe curve and U - t Dataset.

[0058] COMSOL simulation results U - t Dataset imported into Excel U - t The data table, as shown in Table 1, is... U - t Part of the data table: Table 1

[0059] Find the time corresponding to 6.32V in the data table. t = τ =3.96×10 -7 Substitute the data into s: ; The relative error is (81.15-80.1) / 80.1=1.3%, which is within the allowable error range.

[0060] (3) The liquid dielectric constant measurement method of the present invention is as follows: After shortening the time step, in Table 2 of the COMSOL simulation U - t The data table contains the half-response period: Δ t =2.77×10 -7 s.

[0061] Table 2

[0062] Substitute the data: ; The relative error is (80.39-80.1) / 80.1=0.36%, which is within the allowable error range.

[0063] Analysis of the experimental results obtained by three different measurement methods revealed that the linear fitting method had an error of 2.88%, the time constant measurement method had an error of 1.3%, while the measurement method provided by this invention had an error of only 0.36%. Compared with the first two calculation methods, the measurement results of this invention are closer to the standard value.

[0064] In addition, the present invention has another advantage. In order to reduce errors, the time constant measurement method can only find the corresponding data of integer multiples of the time constant τ in the response data, while the RC zero-state response of the present invention can select data at any time point for calculation while ensuring accuracy.

[0065] The dielectric constants of other liquids are calculated as follows: The dielectric constant values ​​of two liquids, toluene (dielectric constant of 2.3) and glycerol (dielectric constant of 45.8), were calculated using the measurement method provided in this invention.

[0066] The half-response time of toluene is 8.03 × 10⁻⁶. -9 s.

[0067] Table 3

[0068] As shown in Table 3, substituting the corresponding data into the calculation formula yields the dielectric constant of toluene: ; That is, the relative error is 2.17%. The half-time of glycerol is 1.56 × 10⁻⁶. -7 s.

[0069] Table 4

[0070] As shown in Table 4, substituting the corresponding data into the calculation formula yields the dielectric constant of glycerol: ; The relative error is 0.4‰. It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0071] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A liquid dielectric constant measurement system based on RC transients, characterized in that: The device includes a liquid storage container, a measuring circuit, a signal processor, and a display terminal. The measuring circuit includes a parallel plate capacitor, and the two plates of the parallel plate capacitor are respectively fixed on the opposite inner walls of the liquid storage container. The parallel plate capacitor is connected to the signal processor, and the signal processor is connected to the display terminal. The liquid to be tested is injected into the storage container, and the liquid to be tested comes into contact with the two plates of the parallel plate capacitor. The parallel plate capacitor is controlled to charge. The signal processor collects the transient voltage-time raw data during the charging process of the parallel plate capacitor and transmits the collected data to the display terminal. The display terminal processes the transient voltage-time raw data based on the RC zero-state response algorithm to obtain and display the dielectric constant of the liquid to be tested.

2. The liquid dielectric constant measurement system based on RC transient as described in claim 1, characterized in that: The liquid storage container is also equipped with an injection port and a pressure balance port. The injection port is used to inject the liquid to be tested, and the pressure balance port is used to discharge the liquid and eliminate the pressure resistance of the liquid storage container during injection and discharge.

3. The liquid dielectric constant measurement system based on RC transient as described in claim 1, characterized in that: The parallel plate capacitor has a terminal on each of its two plates, and the liquid storage container has a through hole corresponding to each terminal. The terminal extends through the through hole to the outer wall of the liquid storage container, thereby realizing the electrical connection between the parallel plate capacitor and the signal processor.

4. The liquid dielectric constant measurement system based on RC transient as described in claim 1, characterized in that: The signal processor is a PC virtual oscilloscope, which includes an A acquisition interface and a B acquisition interface.

5. The liquid dielectric constant measurement system based on RC transients according to claim 4, characterized in that: The measurement circuit also includes a DC regulated power supply, a first switch, a second switch, a first resistor, and a second resistor. One end of the parallel plate capacitor is connected to the negative terminal of the DC regulated power supply, the other end of the parallel plate capacitor is connected to one end of the first resistor, the other end of the first resistor is connected to the positive terminal of the DC regulated power supply through the first switch, one end of the second resistor is connected to one end of the parallel plate capacitor, and the other end of the second resistor is connected to the other end of the parallel plate capacitor through the second resistor. The two ends of the A acquisition interface of the PC virtual oscilloscope are connected across the positive and negative terminals of the DC regulated power supply. One end of the B acquisition interface of the PC virtual oscilloscope is connected to the connection point of the parallel plate capacitor and the second switch, and the other end of the B acquisition interface of the PC virtual oscilloscope is connected to the connection point of the parallel plate capacitor and the second resistor.

6. A method for measuring the dielectric constant of a liquid based on RC transients, implemented using the liquid dielectric constant measurement system based on RC transients as described in any one of claims 1-5, characterized in that: Specifically, the steps include the following: S1: Build a liquid dielectric constant measurement system based on RC transient and inject the liquid to be measured into the storage container; S2: Controls the charging of the parallel plate capacitor. The signal processor collects the transient voltage-time raw data during the charging process of the parallel plate capacitor and transmits the collected data to the display terminal. S3: The display terminal processes the transient voltage-time raw data based on the RC zero-state response algorithm to obtain and display the dielectric constant of the liquid under test.

7. The liquid dielectric constant measurement method based on RC transient as described in claim 6, characterized in that: Step S3 specifically includes: S31: Use 50% of the voltage output by the DC regulated power supply of the measurement circuit as the reference threshold. S32: In the raw transient voltage-time data, the time corresponding to the reference threshold is taken as the half-response time, and the difference between the start time and the half-response time is taken as the half-response period. S33: Calculate the dielectric constant of the liquid to be tested using the following formula. : ； Where d is the distance between the two plates of the parallel plate capacitor. Let be the dielectric constant of the liquid being tested. is the vacuum dielectric constant; S is the area of ​​the two plates facing each other in the parallel plate capacitor; Δt is the half-response time period; and R is the resistance of the first resistor.

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