Electrochemical sensor for measuring conductivity and dielectric constant of liquid

Abstract

The invention relates to the field of liquid on-line monitoring, and provides an electrochemical sensor for measuring conductivity and dielectric constant of liquid, comprising: a probe comprising a first electrode plate, a second electrode plate and a third electrode plate which are successively arranged; the measuring circuit comprises an RC circuit, an amplifying circuit, a comparison circuit and a NOT gate circuit, the NOT gate circuit is used for obtaining a fourth voltage u4, the duration time of a high level in the fourth voltage u4 is first time t1, the duration time of a low level in the fourth voltage u4 is second time t2, and the first time t1 is a second time t2; the first time t1 and the second time t2 are used for determining the conductivity and the dielectric constant. The dielectric property is determined through accurate time measurement, the measurement technology and high time / bandwidth are integrated together, and very high precision and repeatability are achieved. Wherein the accuracy of the conductivity can reach piezemens / meter (pS / m), and the accuracy of the dielectric constant can reach 0.0001.

Description

Technical Field

[0001] The present application relates to the field of online monitoring of liquids, and in particular, to an electrochemical sensor for measuring the electrical conductivity and dielectric constant of liquids. Background Art

[0002] Rapid analysis and determination of the quality and changing characteristics of liquids such as oil (such as lubricating oil) and ethanol is the premise and guarantee for the safe and efficient operation of industrial equipment that uses oil, ethanol and other liquids for lubrication. Unlike chemical analysis methods that obtain information on the composition and structure of substances based on chemical reactions, physical analysis methods are currently usually used to analyze the physical and chemical characteristics of liquids, such as spectral analysis, spectroscopic analysis, organic mass spectrometry and other instrumental analysis techniques. For example, in the field of lubricating oil analysis and testing, the physical and chemical properties of lubricating oil (force, sound, heat, electricity, light, etc.) are the focus of various physical analysis technologies. For example, spectral analysis technology (infrared spectroscopy, near-infrared spectroscopy, Raman spectroscopy, etc.) makes full use of the optical and physical properties of lubricating oil.

[0003] Dielectric properties are one of the important physical properties of liquids used for industrial lubrication, such as lubricating oil and ethanol. The dielectric properties are mainly characterized by dielectric constant and conductivity. The dielectric constant / conductivity analysis method is a feasible analysis method for evaluating the oxidation decay process of liquids. The dielectric property parameter measurement values ​​(dielectric constant and conductivity) of lubricating oil and other liquids during the degradation process have a good linear relationship with quality indicators such as pH value.

[0004] However, at present, the main methods for measuring the dielectric properties of electrochemical sensors include capacitance method, impedance analysis method, resonance method, etc. The accuracy of the dielectric constant and conductivity measured by these methods is low, which leads to a high degree of uncertainty in the monitoring results of the online monitoring system. The reason is that liquids such as lubricating oil and ethanol have very high resistance R and very low capacitance C, which causes the measurement methods such as capacitance method, impedance analysis method, resonance method to have high errors and low resolution, and the measurement accuracy cannot be achieved. Therefore, at this stage, there is an urgent need for electrochemical sensors with higher measurement resolution and smaller errors for monitoring the dielectric properties of liquids. Summary of the invention

[0005] The present application provides an electrochemical sensor for measuring the conductivity and dielectric constant of liquids, which determines the dielectric properties through precise time measurement, that is, integrating the measurement technology with high time / bandwidth, and finally measuring the conductivity and dielectric constant with very high accuracy and repeatability. The accuracy of the conductivity can reach 1 pico-Siemens / meter (pS / m) and the sensitivity can reach 0.1 pS / m, and the accuracy of the dielectric constant can reach 0.0001 and the sensitivity can reach 1×10 -6 .

[0006] The electrochemical sensor comprises: a probe, the probe comprises a first electrode sheet, a second electrode sheet and a third electrode sheet arranged in sequence, wherein the first electrode sheet close to the sensor and the second electrode sheet are connected via two electrode posts, and the third electrode sheet at the outermost side of the sensor is connected to the second electrode sheet via one electrode post; a measuring circuit, the measuring circuit comprises an RC circuit, an amplifying circuit, a comparing circuit and a NOT gate circuit, the RC circuit is used to measure the voltage change of the liquid, and the amplifying circuit is used to amplify the voltage change of the RC circuit to obtain a first voltage u 1. The comparison circuit is used to compare the first voltage output by the amplifier circuit. u 1 and 0 to get the third voltage u 3. The NOT gate circuit is used to compare the third voltage u 3 and a second voltage applied to the measurement circuit u 2 to obtain the fourth voltage u 4, wherein the fourth voltage u 4 The duration of the high level is the first time t 1. The fourth voltage u 4 The duration of the low level is the second time t 2. The first time t 1 and the second time t 2 is used to determine the conductivity and the dielectric constant.

[0007] In the embodiment of the present application, the structure of the three-electrode sheet is preferably used as the probe of the sensor. The embodiment of the present application improves the measurement accuracy and stability through the structure of the three-electrode sheet, and the construction and maintenance cost of the three-electrode sheet structure is relatively low, and no complicated setting and calibration process is required. The three-electrode sensor can eliminate the influence of the polarization effect on the measurement to a large extent by introducing a reference electrode, thereby improving the measurement accuracy and stability. The potential of the reference electrode is stable and is not affected by changes in the composition of the electrolyte. It can be used as a reference benchmark for the electrode, so that the electrochemical reaction is only affected by the substance to be measured. Through the structure of the three-electrode sheet of the present application, the sensor of the embodiment of the present application has a wider measurement range, the measurement unit of conductivity can reach 0.1~2000000 pS / m, and the relative dielectric constant (the ratio of the dielectric constant of the dielectric to the dielectric constant in a vacuum) can reach 1~6.

[0008] In the embodiments of the present application, a comparison circuit and a NOT gate circuit are introduced, and the dielectric properties obtained by measuring R and C are replaced by determining the dielectric properties by precise time measurement, that is, the measurement technology and high time / bandwidth are integrated together, and the conductivity and dielectric constant finally measured have very high accuracy and repeatability.

[0009] Optionally, the electrochemical sensor may also include a shell material to protect the internal sensitive components, which should not only be able to withstand external physical impact and chemical corrosion, but also have excellent heat dissipation performance and sealing. Common shell materials include metal, plastic, and ceramic.

[0010] Optionally, the structure of the sensor can adopt a standardized design to facilitate rapid connection and interchange with other devices or systems. For example, modern sensors often integrate multiple interface types such as RS485 to meet the needs of different application scenarios. At the same time, in order to improve the reliability and speed of data transmission, the sensor of the embodiment of the present application can also use wireless communication technology, such as 4 / 5G, Wi-Fi, etc.

[0011] In combination with the first aspect, in a possible implementation of the first aspect, the liquid includes at least one of oil, methanol, and ultrapure water, and the oil includes at least one of lubricating oil, hydraulic oil, and transformer oil.

[0012] In combination with the first aspect, in a possible implementation manner of the first aspect, the third electrode sheet is a reference electrode, and the first electrode sheet and the second electrode sheet are a working electrode and an auxiliary electrode, respectively.

[0013] In the embodiments of the present application, adding a reference electrode is equivalent to connecting an external voltage stabilizing circuit, which can stabilize the electromotive force of the sensitive electrode. At the same time, no current flows through the reference electrode to maintain the stability of the respective voltages, so that even if the negative electrode continues to polarize, it will not have any effect on the working electrode. The biggest advantage of the three-electrode design is that it provides a bias voltage for the sensor, which enhances the reactivity of some inactive gases and causes them to undergo oxidation or reduction reactions. The reference electrode electromotive force generally does not undergo bias catalytic reactions.

[0014] In combination with the first aspect, in a possible implementation manner of the first aspect, the first time t 1 and the second time t 2 is used to determine the conductivity and the dielectric constant, including: The conductivity k Determined by the following formula: ; in, l is the distance between the first electrode sheet, the second electrode sheet and the third electrode sheet; A is the surface area of ​​the electrode plate; C is a known capacitance.

[0015] In combination with the first aspect, in a possible implementation manner of the first aspect, the first time t 1 and the second time t 2 is used to determine the conductivity and the dielectric constant, including: The dielectric constant Obtained by the following formula: ; in, k is the conductivity, is the dielectric constant in vacuum.

[0016] In the above formula, the conductivity and dielectric constant are calculated using more accurate time values ​​instead of directly using the resistance R and capacitance C. By integrating the measurement technology with high time / bandwidth, it has very high accuracy and repeatability.

[0017] In combination with the first aspect, in a possible implementation of the first aspect, the electrochemical sensor further includes a self-cleaning module, and after the electrochemical sensor measures, the self-cleaning module is used to release acetone or ethylene glycol to clean the probe of the sensor.

[0018] The sensor of the embodiment of the present application can be used to measure multiple liquids, so it is possible that the sensor is used to measure another liquid after measuring one liquid. The self-cleaning module makes the sensor probe more sensitive during the next measurement.

[0019] In combination with the first aspect, in a possible implementation manner of the first aspect, the electrochemical sensor is also used to measure the temperature and pressure of the liquid.

[0020] By integrating multiple measurement functions, it helps reduce the number of sensors in the device, reducing cost and complexity.

[0021] In combination with the first aspect, in a possible implementation of the first aspect, the electrochemical sensor adopts low-power materials and technologies, and implements an intelligent wake-up mechanism (ie, the sensor is activated only when needed).

[0022] In a second aspect, a liquid online monitoring system is provided, the liquid online monitoring system comprising a sensor module, the sensor module comprising the electrochemical sensor as described in any one of the embodiments of the first aspect.

[0023] Optionally, the liquid online monitoring system may also include multiple modules such as data acquisition equipment, data processing and analysis modules, communication modules, and early warning modules. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of an oil online monitoring system provided in an embodiment of the present application.

[0025] Figure 2 Schematic diagram of an electrochemical sensor for measuring liquid conductivity and dielectric constant provided in an embodiment of the present application.

[0026] Figure 3 It is a schematic diagram of a measurement circuit provided in an embodiment of the present application.

[0027] Figure 4 It is a schematic diagram of measurement waveforms of a measurement circuit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0028] Embodiments of the present application are described in detail below, and examples of the embodiments of the present application are shown in the accompanying drawings. In the accompanying drawings, the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0029] Unless otherwise defined, the technical terms or scientific terms used herein shall have the usual meanings understood by persons having ordinary skills in the technical field to which this application belongs. In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to this application.

[0030] References to "one embodiment" or "some embodiments" etc. described in this specification mean that a particular feature, structure or characteristic described in conjunction with the embodiment is included in one or more embodiments of the present application. Thus, the phrases "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear at different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0031] For ease of understanding, the online monitoring system to which the electrochemical sensor of the embodiment of the present application is applied is first introduced. The online monitoring system may be an online monitoring system for monitoring oil (such as lubricating oil), ethanol, methanol or ultrapure water. The online monitoring system of the embodiment of the present application is introduced below by taking the online monitoring system of oil as an example.

[0032] Oil monitoring technology is an important technical means to realize equipment lubrication status monitoring and damage fault diagnosis. Its principle is mainly to obtain information on the lubrication and wear status of the equipment's friction pairs through analysis of the physical and chemical performance indicators of the lubricating oil used in the equipment, as well as the water content, wear metal particles and pollution products in the oil, so as to diagnose the equipment's lubrication status and wear faults. Figure 1 A schematic diagram of an oil online monitoring system 100 provided in an embodiment of the present application is shown.

[0033] like Figure 1 As shown, the online monitoring system 100 for oil is a comprehensive system that integrates multiple modules such as sensors, data acquisition equipment, data processing and analysis modules, communication modules, and early warning modules. The online monitoring system 100 for oil is mainly used to monitor and analyze the conditions of lubricating oil, hydraulic oil and other liquids in industrial equipment when they are entering or returning the oil tank in real time to ensure the normal operation of the equipment and reduce maintenance costs. For example, the modules mainly included in the online monitoring system 100 for oil are: 1. Sensor modules are used to measure key parameters of oil, such as temperature, conductivity, dielectric constant, water content, water activity, moisture, acid value, viscosity, density, and particle size. For example, oil data can be collected and converted into electrical signals by contact with the oil or by transmission through the oil. These sensors usually include viscosity sensors, pollution particle sensors, dielectric property sensors, etc.

[0034] 2. Data acquisition module, used to receive and process data signals transmitted by sensors. It can sample, convert and store data for subsequent analysis and management. Data acquisition can be carried out by wire or wireless means to ensure real-time performance.

[0035] 3. Data processing and analysis software module, used for real-time analysis, trend analysis, fault diagnosis and prediction of collected data, and generating reports and alarms. It can provide an intuitive graphical interface for users to view the changing trends and abnormal conditions of oil status. In addition, it can also predict the failure trend of equipment through data models and analysis algorithms, and take measures in advance to prevent failures.

[0036] 4. Communication and remote monitoring module, used to realize the communication between the system and the remote terminal or cloud platform, as well as the remote transmission and monitoring of data. Users can remotely view the status of the oil, analyze reports and receive alarm notifications through devices such as smartphones, tablets or computers. At the same time, the setting and adjustment of equipment parameters can also be remotely controlled.

[0037] 5. Early warning and notification module, used to trigger alarm and notification mechanism according to the set threshold or condition. When the oil parameters exceed the preset range, the system can automatically issue an alarm and notify relevant personnel so that appropriate measures can be taken in time.

[0038] In summary, through the collaborative work of these modules, the oil online monitoring system can realize functions such as real-time monitoring of oil status, data analysis, and early warning notification, thereby improving equipment reliability and operating efficiency and reducing maintenance costs.

[0039] It is worth noting that Figure 1 The oil online monitoring system 100 is only taken as an example, which does not limit the protection scope of the present application. Figure 1 The system architecture shown is applied to the online monitoring system of liquids such as methanol and ultrapure water.

[0040] As can be seen from the above, the sensor module of the online monitoring system can be used to measure multiple key parameters of the liquid, such as the physical and chemical properties of the liquid. Among them, dielectric properties are one of the important physical properties of liquids such as oil and methanol introduced in the previous article, and their dielectric properties are mainly characterized by dielectric constant and conductivity. For example, there are two aspects to the relevant application research using the dielectric properties of lubricating oil: one is the analysis and testing of the lubricating oil in use, using the changes in the dielectric constant or conductivity of the lubricating oil in use to detect or monitor the quality changes of the lubricating oil, and then monitor the operating status of the equipment; the second aspect is to use the dielectric constant of the lubricating oil to associate the quality indicators of the lubricating oil, so as to achieve the purpose of using the dielectric constant of the lubricating oil to measure its related quality indicators.

[0041] In addition, the dielectric constant / conductivity analysis method is a feasible analysis method for evaluating the oxidation decay process of liquids. The measured values ​​of dielectric performance parameters (dielectric constant conductivity) of liquids such as lubricating oil during the deterioration process have a good linear relationship with quality indicators such as pH value.

[0042] Generally speaking, the higher the cleanliness of lubricating oil, the lower its dielectric constant and the higher its resistivity, which is the basis for monitoring the cleanliness of lubricating oil using its dielectric constant and resistivity. After the lubricating oil is polluted and deteriorated, some hydrocarbon molecules in the oil are oxidized into peroxides, acids and other groups, polarizing the molecules. The deeper the oxidation of the lubricating oil, the relatively increased content of polar substances in it, reflecting the stronger polarity of the oil, so the dielectric constant of the oil also increases accordingly.

[0043] Therefore, in the online monitoring technology of liquids such as oil, methanol, and ultrapure water, online monitoring of the dielectric properties of the liquid is very important, that is, the sensor used to monitor the dielectric properties is an important part of the sensor module of the online monitoring system.

[0044] At present, sensors used to monitor the dielectric properties of liquids usually measure dielectric properties through the following methods: capacitance method, impedance analysis method, resonance method, etc. For example, the capacitance method is based on the basic principle of capacitors, and the dielectric constant (ε) of the material is inferred by measuring the capacitance value when the sample is used as a medium between the capacitor plates. For another example, the impedance analysis method is a method of evaluating the dielectric properties of a sample by measuring its impedance characteristics in an AC electric field. This method uses an impedance analyzer to measure the impedance and phase angle of the sample over a wide frequency range to obtain the complex dielectric constant (ε*=ε′-jε″, where ε′ is the real part of the dielectric constant and ε″ is the imaginary part of the dielectric constant, which is related to the dielectric loss). For another example, the resonance method is a method of measuring the dielectric constant by using the relationship between the resonant frequency of the circuit and the dielectric constant of the sample when the sample and the circuit form a resonant circuit. This method usually uses a microwave resonant cavity or an LC resonant circuit to place the sample in the resonant circuit and infer the dielectric constant of the sample by measuring the change in the resonant frequency.

[0045] However, since liquids such as lubricating oil and methanol have very high resistance R and very low capacitance C, and the aforementioned dielectric property measurement methods all require resistance or capacitance values. Very high resistance R and very low capacitance C will affect the resistance and capacitance values ​​during measurement, reduce the resolution of the measurement results, increase the error of the measurement results, and ultimately affect the measurement accuracy of the dielectric constant and conductivity, resulting in a high degree of uncertainty in the monitoring results of the online monitoring system.

[0046] In other words, the current sensors for measuring dielectric properties have low measurement resolution and large errors, resulting in inaccurate measurement results. In order to solve the above problems, the present application embodiment shows an electrochemical sensor for measuring liquid conductivity and dielectric constant, which has higher measurement accuracy, wherein the accuracy of conductivity can reach 1 pico-Siemens / meter (pS / m) and the sensitivity can reach 0.1 pS / m, and the accuracy of dielectric constant can reach 0.0001 and the sensitivity can reach 1×10 -6 .

[0047] The electrochemical sensor provided in the embodiments of the present application is described below with reference to the accompanying drawings.

[0048] Figure 2 FIG. 2 shows a schematic diagram of the appearance of an electrochemical sensor 200 provided in an embodiment of the present application and a schematic diagram of the structure of a probe. Figure 2 As shown in (a) in FIG. 1 , the electrochemical sensor 200 includes a housing and a probe connected to the housing. The housing of the sensor is used to protect the internal sensitive components. It must not only be able to withstand external physical impact and chemical corrosion, but also have excellent heat dissipation performance and sealing. Common housing materials include stainless steel, engineering plastics, etc.

[0049] The interface and connector of the sensor are the key parts to realize data transmission and control. In the embodiments of the present application, a standardized design can be adopted to facilitate rapid connection and interchange with other devices or systems. For example, modern sensors often integrate multiple interface types such as RS485 to meet the needs of different application scenarios. At the same time, in order to improve the reliability and speed of data transmission, the sensor of the embodiment of the present application can also use wireless communication technology, such as 4 / 5G, Wi-Fi, etc.

[0050] Figure 2 The probe shown is the sensitive element of the sensor, which is the part of the sensor that directly responds to the measurement and converts the physical quantity signal of the liquid to be measured into an electrical signal (such as voltage, current, resistance, etc.). In the embodiment of the present application, a three-electrode sheet structure is preferably used as the sensor probe. Figure 2 As shown in (b) of FIG. 1 , the three-electrode probe includes three arranged electrode sheets, wherein the two electrode sheets close to the inner side of the sensor housing are connected through two electrode posts, and the outermost electrode sheet is connected to the middle electrode sheet only through one electrode post. Figure 2 The top electrode in (b) acts as a reference electrode (also called reference electrode, reference electrode, base electrode, etc.), and the other two electrode sheets are the working electrode and the auxiliary electrode respectively.

[0051] In the current two-electrode sensor, the polarization of the negative electrode limits the measurement to a certain extent. Therefore, in the embodiment of the present application, adding a reference electrode is equivalent to connecting an external voltage stabilizing circuit, which can stabilize the electromotive force of the sensitive electrode. At the same time, no current flows through the reference electrode to maintain the stability of each voltage, so that even if the negative electrode continues to polarize, it will not have any effect on the working electrode. The biggest advantage of the three-electrode design is that it provides a bias voltage for the sensor, which enhances the reactivity of some inactive gases and causes them to undergo oxidation or reduction reactions. The reference electrode electromotive force generally does not undergo bias catalytic reactions.

[0052] It is worth noting that those skilled in the art should understand that the use of three electrode sheets as the sensor electrode structure in the embodiment of the present application is not a simple modification of the number of electrode sheets in the existing two-electrode sheet and four-electrode sheet, but takes into account the specific scenario of measuring the conductivity of the liquid, i.e. the dielectric constant. In other words, the use of three electrode sheets in the embodiment of the present application is not a random decision.

[0053] First, as mentioned above, in the sensor of the three-electrode probe of the embodiment of the present application, the introduction of the reference electrode can stabilize the potential of the working electrode, thereby effectively reducing the influence of the polarization effect on the measurement. In the measurement of liquids such as oil and methanol, the polarization effect may cause distortion of the measurement signal, thereby affecting the measurement accuracy. The three-electrode design ensures the accuracy and stability of the measurement signal by separating the polarization current and the measurement current.

[0054] Second, the conductivity of liquids such as oil and methanol may change due to a variety of factors such as temperature and water content. The three-electrode sensor can compensate for conductivity changes online, eliminating the impact of such changes on measurement accuracy. This is particularly important for monitoring liquids such as oil and methanol, because changes in liquid state are often accompanied by changes in conductivity. For example, a three-electrode sensor can extract liquid film fluctuation information under conditions where the conductivity of the liquid film varies over a wide range, and can compensate online for the impact of conductivity changes on liquid film thickness measurements.

[0055] Third, the measurement accuracy and stability of the probe structure with four or more electrodes are higher, but increasing the number of electrodes will undoubtedly increase the manufacturing cost of the sensor, and more electrodes also mean more potential failure points and more complicated maintenance processes. In addition, although the probe structure with four or more electrodes can provide more advanced measurement capabilities in some cases, such as more accurate measurement of the impedance value of the solution interface, its complexity may not always bring significant accuracy improvement in general electrochemical performance measurements.

[0056] In summary, the embodiment of the present application improves the measurement accuracy and stability through the structure of the three-electrode sheet, and the construction and maintenance cost of the three-electrode sheet structure is relatively low, and no complicated setting and calibration process is required. The three-electrode sensor can eliminate the influence of the polarization effect on the measurement to a large extent by introducing a reference electrode, thereby improving the measurement accuracy and stability. The potential of the reference electrode is stable and is not affected by changes in the composition of the electrolyte. It can be used as a reference benchmark for the electrode, so that the electrochemical reaction is only affected by the substance to be measured. Through the structure of the three-electrode sheet of the present application, the sensor of the embodiment of the present application has a wider measurement range, the measurement unit of conductivity can reach 0.1~2000000 pS / m, and the relative dielectric constant (the ratio of the dielectric constant of the dielectric to the dielectric constant in a vacuum) can range from 1 to 6.

[0057] Finally, if Figure 2 As shown in (c), Figure 2 (c) includes a sensor holder for fixing the sensor and a pipe coupled to the sensor holder for conveying the liquid, and the sensor holder is fixed as follows Figure 2The electrochemical sensor shown in (a) above converts the physical signal of the liquid into an electrical signal after the liquid in the pipeline, such as oil, methanol, etc., passes through the probe.

[0058] Figure 3 Shows Figure 2 The structure diagram of the measurement circuit in the electrochemical sensor 200 is shown. The measurement circuit of this structure is used to process the electrical signal (such as voltage) converted by the probe of the aforementioned sensor to obtain parameters for calculating conductivity and dielectric constant.

[0059] like Figure 3 As shown, the measuring circuit includes four parts: an RC circuit, an amplifier circuit, a comparison circuit (or a comparator) and a NOT gate circuit.

[0060] Among them, the RC circuit is used to measure the voltage change of the liquid, that is, the change of the voltage signal converted by the measuring probe. The amplifier circuit is used to amplify the voltage signal converted by the probe. The RC circuit and the amplifier circuit are the main parts of the measurement circuit of the current sensor. According to the above, since liquids such as oil and methanol have a large resistance R and a small capacitance C, the accuracy is low when only the RC circuit is used for measurement. Therefore, if Figure 3 As shown, in the embodiments of the present application, a comparison circuit and a NOT gate circuit are introduced, and the dielectric properties obtained by measuring R and C are replaced by determining the dielectric properties by precise time measurement, that is, the measurement technology and high time / bandwidth are integrated together, and the conductivity and dielectric constant finally measured have very high accuracy and repeatability.

[0061] First combine Figure 3 Introduce the structure of the measurement circuit. Figure 3 As shown, the first end on the left side of the RC circuit is connected to the first input end on the left side of the NOT gate circuit (i.e. Figure 3 The second end on the right side of the RC circuit is connected to the first end on the left side of the amplifier circuit. The potential on the left side of the RC circuit is u 2, and then the potential of the first input terminal of the NAND gate circuit is also u 2. The potential on the right side of the RC circuit is amplified by the amplifier circuit and becomes u 1. The second end on the right side of the amplifier circuit is connected to the two input ends of the comparison circuit. The comparison circuit u 1 is compared with the potential 0 and the output potential u 3. The first output terminal of the comparison circuit (i.e. Figure 3 The output terminal above the comparison circuit is connected to the first input terminal of the NOT gate circuit and the first terminal of the RC circuit. The second output terminal of the comparison circuit (i.e. Figure 3 The output terminal below is connected to the second input terminal of the NOT gate circuit.u 2 and the second input u 3. Compare and get the potential u 4. The potential u The waveform of 4 can be used to calculate conductivity and dielectric constant through precise time measurement.

[0062] Combine the following Figure 4 Introduction This application is based on Figure 3 Measurement method and measurement process of the circuit shown.

[0063] like Figure 4 As shown, when a potential is applied to the left side of the circuit or RC circuit u 2, the voltage across the resistor R and capacitor C will change. Figure 4 Shown u The change of 1 is the change of the voltage across the resistor R and the capacitor C. For example, when u 2 is -1 (high level in the opposite direction), the capacitor C is discharged to 0 and then charged. u 1 first drops to 0 and then increases. u When 2 is 1 (high level), capacitor C is also discharged to 0 and then charged.

[0064] The comparison circuit passes u Comparing the potential value of 1 with 0, we get u 3. Among them, when u When 1 is greater than 0, u The value of 3 is 1; when u When 1 is less than 0, u The value of 3 is -1. u The value of 2 and u 3, we get u 4. That is, when u The value of 2 is u When the value of 3 is the same, u 4 is 0, when u The value of 2 is u When the value of 3 is different, u 4 is 1. Finally, if Figure 4 As shown, u The value of 4 includes the duration of the high level t 1 and the duration of low level t 2. These two time values ​​can be used to calculate the conductivity and dielectric constant of the liquid.

[0065] For example, for a homogeneous liquid, the resistance R and the conductivity k The relationship is: ; in, lis the distance between the electrode plates, that is Figure 2 The spacing between the three electrode plates shown; A is the surface area of ​​the electrode plate.

[0066] And because, the relationship between capacitance C and resistance R is: ; in, is a time constant. In the embodiment of the present application, The value of can be t 1.

[0067] Therefore, the conductivity of the liquid It can be obtained by the following formula: ; Similarly, the dielectric constant of a liquid is It can be obtained by the following formula: ; in, k is the conductivity, is the dielectric constant in vacuum (approximately 8.854×10 −12 F / m).

[0068] It is worth noting that the above formula is only an example, and the present application can also use other more accurate calculation methods to calculate the duration of the high level. t 1 and the duration of low level t 2 to accurately calculate the conductivity and dielectric constant.

[0069] In other words, in the embodiment of the present application, the electrochemical sensor does not directly calculate the conductivity and dielectric constant through the resistance R and the capacitance C, but uses a more accurate time value to calculate the conductivity and dielectric constant. By integrating the measurement technology with high time / bandwidth, it has very high accuracy and repeatability, and the accuracy of conductivity can reach 1 pico-Siemens / meter (pS / m) and the accuracy of dielectric constant can reach 0.0001.

[0070] Optionally, in other embodiments of the present application, since there may be temperature interference when measuring liquids, the present application can improve the accuracy and stability of the sensor by finding out the variation pattern of the error, or measuring its size and direction, and using appropriate methods (such as electronic circuits, software algorithms, etc.) to perform temperature compensation or correction for the error caused by the characteristics of the sensor itself, working conditions, or external environment. Figure 3The circuit shown introduces a differential circuit. The differential technology can significantly reduce the impact of temperature changes, power supply fluctuations, external interference, etc. on the sensor accuracy, offset common-mode errors, reduce nonlinear errors, and thus improve the accuracy of the sensor.

[0071] Optionally, in order to improve the stability of the sensor, necessary stability treatments may be performed on the sensor materials, components or the entire sensor, such as time aging, temperature aging, mechanical aging and AC stabilization treatments, aging screening, etc. of the permanent magnetic material to improve the long-term stability of the sensor performance.

[0072] Since the sensor of the embodiment of the present application can be used to measure multiple liquids, it is possible that the sensor is used to measure another liquid after measuring one liquid. Therefore, optionally, in the embodiment of the present application, a self-cleaning module can be introduced into the sensor, and after the sensor measures the conductivity and dielectric constant of one liquid, the self-cleaning module releases acetone or ethylene glycol to clean the sensor probe, thereby making the sensor probe more sensitive during the next measurement.

[0073] Optionally, the electrochemical sensor in the embodiment of the present application can also be used to integrate other measurement modules, such as measurement modules for measuring temperature and pressure. By integrating multiple measurement functions, it helps to reduce the number of sensors in the device, reduce costs and complexity.

[0074] Optionally, the electrochemical sensor in the present application can adopt low-power materials and technologies, and implement an intelligent wake-up mechanism (i.e., activating the sensor only when needed), which can significantly reduce the power consumption of the sensor and extend the use time of the device.

[0075] For example, sensors can be awakened through task cycles. For example, the awakening cycle and sleep cycle of each node can be pre-set and coexist with other nodes in other working modes to assist in completing specific tasks. The advantage of task cycle awakening is that the working status of each node can be clearly known, which is convenient for management and optimization. In addition, through reasonable task scheduling, the power consumption of the entire system can be reduced and the service life of the equipment can be extended.

[0076] For another example, when the sensor detects that there is vibration in the oil tank when the oil is delivered or returned, the sensor wakes up. For example, a ball mechanism and a sensing electrode can be integrated in the sensor. When the environment or equipment where the sensor is located vibrates, the ball mechanism moves accordingly, causing the contact state between the ball and the sensing electrode to change, thereby generating an electrical signal. This electrical signal is processed by amplification, filtering, etc., and is used to trigger the wake-up circuit.

[0077] For another example, the sensor can automatically adjust the wake-up mode according to changes in the external environment and internal state. This mechanism dynamically adjusts the sensor's wake-up strategy and parameters by monitoring factors such as environmental changes, device status, and task requirements in real time. For example, when only conductivity and dielectric constant need to be measured, the sensor will reduce the sampling rate and resolution to reduce power consumption; when more parameters need to be measured and very high accuracy requirements are required, the sampling rate and resolution will be increased to improve monitoring accuracy.

[0078] Optionally, the electrochemical sensor in the present application may be integrated with intelligent algorithms to self-calibrate and repair, thereby reducing the number and time of maintenance and reducing maintenance costs. For example, the sensor can automatically detect and correct errors, or self-repair when a fault occurs.

[0079] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0080] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0081] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0082] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0083] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application can be essentially or partly embodied in the form of a software product that contributes to the prior art. The computer software product is stored in a storage medium and includes several instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present application. The aforementioned storage media include: U disk, mobile hard disk, read-only memory (ROM), random access memory (RAM), disk or optical disk, and other media that can store program codes.

[0084] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. An electrochemical sensor for measuring liquid conductivity and dielectric constant, characterized in that: include: A probe, the probe comprising a first electrode sheet, a second electrode sheet and a third electrode sheet arranged in sequence, wherein the first electrode sheet close to the sensor and the second electrode sheet are connected via two electrode posts, and the third electrode sheet at the outermost side of the sensor is connected to the second electrode sheet via one electrode post; The measuring circuit includes an RC circuit, an amplifier circuit, a comparison circuit and a NOT gate circuit, wherein the RC circuit is used to measure the voltage change of the liquid, and the amplifier circuit is used to amplify the voltage change of the RC circuit to obtain a first voltage u 1. The comparison circuit is used to compare the first voltage output by the amplifier circuit u 1 and 0 to get the third voltage u 3. The NOT gate circuit is used to compare the third voltage u 3 and a second voltage applied to the measuring circuit u 2 to obtain the fourth voltage u 4. Wherein, the fourth voltage u 4 The duration of the high level is the first time t 1. The fourth voltage u 4 The duration of the low level is the second time t 2. The first time t 1 and the second time t 2 is used to determine the conductivity and the dielectric constant.

2. The electrochemical sensor according to claim 1, characterized in that The liquid includes at least one of oil, methanol, and ultrapure water, and the oil includes at least one of lubricating oil, hydraulic oil, and transformer oil.

3. The electrochemical sensor according to claim 1 or 2, characterized in that: The third electrode sheet is a reference electrode, and the first electrode sheet and the second electrode sheet are a working electrode and an auxiliary electrode, respectively.

4. The electrochemical sensor according to claim 1 or 2, characterized in that: The first time t 1 and the second time t 2 for determining the conductivity and the dielectric constant, comprising: The conductivity k Determined by the following formula: ； in, l is the distance between the first electrode sheet, the second electrode sheet and the third electrode sheet; A is the surface area of ​​the electrode plate; C is a known capacitance.

5. The electrochemical sensor according to claim 4, characterized in that The first time t 1 and the second time t 2 for determining the conductivity and the dielectric constant, comprising: The dielectric constant Obtained by the following formula: ； in, k is the conductivity, is the dielectric constant in vacuum.

6. The electrochemical sensor according to claim 1 or 2, characterized in that: The electrochemical sensor further comprises a self-cleaning module, which is used to release acetone or ethylene glycol to clean the sensor probe after the electrochemical sensor measures.

7. The electrochemical sensor according to claim 1 or 2, characterized in that: The electrochemical sensor is also used to measure the temperature of the liquid.

8. A liquid online monitoring system, characterized in that: The liquid online monitoring system comprises a sensor module, wherein the sensor module comprises the electrochemical sensor according to any one of claims 1 to 7.

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