Single-coil electromagnetic resonance type seawater conductivity measurement sensor and system

Abstract

The invention discloses a single-coil electromagnetic resonance type seawater conductivity measurement sensor and system, and relates to the field of seawater conductivity measurement. The sensor comprises a measuring coil, a resonance circuit, a sampling resistor and a measuring circuit. The measuring coil is connected in parallel with the resonant circuit; the measuring coil is arranged in seawater, the measuring circuit generates an alternating current signal with resonant frequency, and the alternating current signal is applied to two ends of the measuring coil after capacitive compensation of the resonant circuit; an alternating current signal after capacitive compensation is introduced into the measuring coil, a high-frequency alternating current magnetic field is generated in the space, the high-frequency alternating current magnetic field excites high-frequency eddy current in the seawater space, and the high-frequency eddy current influences the current in the measuring coil; and the measuring circuit is also used for measuring the voltage at the two ends of the sampling resistor, obtaining an alternating current sampling signal of the voltage, and obtaining the seawater conductivity according to the alternating current sampling signal of the voltage by utilizing a relational expression between the sampling voltage and the seawater conductivity. The structure of the sensor can be simplified, and the measurement precision is improved.

Description

Technical Field

[0001] This application relates to the field of seawater conductivity measurement, and in particular to a single-coil electromagnetic resonant seawater conductivity measurement sensor and system. Background Technology

[0002] Seawater salinity refers to the ratio of total dissolved solids in seawater to the weight of the seawater itself, usually expressed as grams of dissolved solids per kilogram of seawater. It is closely related to indicators such as temperature and conductivity, and is a crucial environmental factor for seawater. Seawater salinity is not only closely related to marine environmental and ecological protection, but also, as a key hydrological element of seawater, is closely related to physical parameters such as sound speed and ocean currents, thus receiving significant attention from marine-related fields.

[0003] The conductivity method is a fast and efficient way to obtain water salinity online. Conductivity measurement offers advantages such as high accuracy and short response time. Currently, commonly used conductivity sensors are mainly divided into electrode sensors and inductive sensors. Electrode sensors are contact-type conductivity sensors, requiring contact with the liquid being measured. Electrode sensors consist of a pair of positive and negative electrodes. By applying a certain voltage to the electrodes and measuring the current, the conductivity of the conductive liquid can be calculated. They are smaller than electromagnetic induction sensors, making them advantageous for measurements in small spaces. Although the technology for measuring solution conductivity using electrode sensors is quite mature, the electrodes are often made of heavy metals like platinum, resulting in high costs. Furthermore, as a contact detection technology, it is prone to affecting the components in the sample solution, interfering with subsequent experiments. As a consumable, the electrodes are susceptible to corrosion after contact with the solution, severely impacting experimental accuracy and cost control. In daily applications, electrodes are also easily oxidized in air, leading to electrode failure and reduced concentration measurement; therefore, they are generally stored in anti-oxidant liquids such as distilled water. Therefore, if the conductivity measurement is applied to easily corrosive materials such as seawater, a non-contact conductivity measurement method should be used.

[0004] Inductive sensors do not require contact with the liquid being measured and therefore do not affect its composition. They primarily utilize electromagnetic induction to measure conductivity. An inductive sensor consists of a transmitting coil and a receiving coil. When a high-frequency current of a certain frequency passes through the transmitting coil, a changing magnetic field is generated around it due to the magnetic effect of the current. Because of the law of electromagnetic induction, this changing magnetic field generates eddy currents in the seawater. As these eddy currents flow through the seawater channel, an induced current is generated in the receiving coil. The magnitude of this induced current is related to the conductivity of the conductive fluid, and this relationship is used to measure conductivity. Inductive sensors have lower sensitivity and are relatively larger in size compared to electrode-based sensors, especially when measuring low conductivity. Furthermore, inductive conductivity sensors require a seawater channel to create seawater eddies for conductivity measurement, thus placing certain demands on the equipment structure.

[0005] It is evident that existing inductive sensors have two main drawbacks: First, the dual-coil structure is relatively complex, requiring an internal seawater guide tube to confine the seawater to be measured within the tube for conductivity measurement, which presents a certain level of difficulty in assembly. Second, the winding coil contains an iron core, which is significantly affected by temperature, impacting measurement accuracy. Summary of the Invention

[0006] The purpose of this application is to provide a single-coil electromagnetic resonant seawater conductivity measurement sensor and system, which can simplify the sensor structure and improve measurement accuracy.

[0007] To achieve the above objectives, this application provides the following solution.

[0008] In a first aspect, this application provides a single-coil electromagnetic resonant seawater conductivity measuring sensor, comprising: a measuring coil, a resonant circuit, a sampling resistor, and a measuring circuit. The measuring coil is connected in parallel with the resonant circuit; one end of the resonant circuit is connected to one end of the measuring circuit, and the other end of the resonant circuit is connected to one end of the sampling resistor, and the other end of the sampling resistor is connected to the other end of the measuring circuit; the measuring coil is placed in seawater, and the measuring circuit generates an AC signal at the resonant frequency, which, after capacitive compensation by the resonant circuit, is applied to both ends of the measuring coil; the capacitively compensated AC signal is passed through the measuring coil, generating a high-frequency AC magnetic field in space, which excites high-frequency eddy currents in the seawater space, and the high-frequency eddy currents affect the current in the measuring coil; the measuring circuit is also used to measure the voltage across the sampling resistor to obtain an AC sampling signal of the voltage, and based on the AC sampling signal of the voltage, the seawater conductivity is obtained using the relationship between the sampling voltage and the seawater conductivity.

[0009] Optionally, the relationship between the sampling voltage and the seawater conductivity is as follows: + ; In the formula, The electrical conductivity of seawater, For sampling voltage, , , and All are fitting coefficients.

[0010] Optionally, the method for determining the relationship between the sampling voltage and seawater conductivity specifically includes: establishing a polynomial fitting model of the sampling voltage and seawater conductivity; the polynomial fitting model includes multiple coefficients to be fitted; setting up various water environments with different seawater conductivity; collecting voltage measurements in water environments with each seawater conductivity; based on the principle of minimizing error using the least squares method, obtaining the value of each coefficient to be fitted when the error of the polynomial fitting model is minimized according to the various different seawater conductivity and the voltage measurements in water environments with each seawater conductivity; and substituting each value of the coefficient to be fitted into the polynomial fitting model to obtain the relationship between the sampling voltage and seawater conductivity.

[0011] Optionally, the measurement circuit includes: a central processing unit (CPU), a DDS signal generator, a sampling circuit, a measurement module, and an AD conversion module; the CPU controls the DDS signal generator to generate an AC signal at a resonant frequency; the DDS signal generator applies the generated AC signal at the resonant frequency, after capacitive compensation by the resonant circuit, to both ends of the measurement coil; the sampling circuit samples the voltage across the sampling resistor using differential measurement to obtain an AC sampling signal of the voltage; the measurement module measures the amplitude of the AC sampling signal of the voltage, generates an amplitude DC signal, and filters out noise from the amplitude DC signal to obtain a filtered amplitude DC signal; the AD conversion module converts the filtered amplitude DC signal into an amplitude digital signal; the CPU also obtains the seawater conductivity based on the amplitude digital signal using the relationship between the sampling voltage and seawater conductivity.

[0012] Optionally, the measurement module includes: an amplitude measurement unit and a filtering circuit; the amplitude measurement unit is used to measure the amplitude of the AC sampling signal of the voltage and generate an amplitude DC signal; the filtering circuit is used to filter out noise in the amplitude DC signal to obtain a filtered amplitude DC signal.

[0013] Optionally, the single-coil electromagnetic resonant seawater conductivity measuring sensor further includes: connecting leads; the two ends of the measuring coil are respectively connected to the two ends of the resonant circuit through the connecting leads.

[0014] Optionally, the single-coil electromagnetic resonant seawater conductivity measuring sensor further includes: a housing; the resonant circuit, sampling resistor, and measuring circuit are all disposed within the housing.

[0015] Optionally, the measuring coil adopts a planar helical structure.

[0016] Optionally, the central processing unit is an STM32F103 chip or an ATMEGA162 chip; the DDS signal generator is an AD9833 chip; the sampling circuit is an instrumentation amplifier or an operational amplifier; the amplitude measurement unit is an AD637 envelope detection chip; the filtering circuit is an active low-pass filter circuit; and the AD conversion module is a 16-bit voltage acquisition chip.

[0017] Secondly, this application provides a single-coil electromagnetic resonant seawater conductivity measurement sensing system, comprising: a host computer, a storage chip, and the single-coil electromagnetic resonant seawater conductivity measurement sensor described in any one of the above-mentioned embodiments. Both the host computer and the storage chip are connected to the measurement circuit in the single-coil electromagnetic resonant seawater conductivity measurement sensor. The measurement circuit is used to transmit the seawater conductivity to the host computer and the storage chip.

[0018] According to the specific embodiments provided in this application, this application has the following technical effects.

[0019] This application provides a single-coil electromagnetic resonant seawater conductivity measurement sensor and system. It simplifies the two measurement coils required in traditional inductive seawater conductivity sensors to a single measurement coil, saving half the equipment space and simplifying the sensor structure. Furthermore, this single-coil electromagnetic resonant seawater conductivity measurement sensor features an open measurement structure; measurement can be performed simply by placing the measurement coil in seawater, eliminating the need for a seawater guide pipe and reducing the difficulty of sensor design and assembly. An AC signal at a resonant frequency is generated through the measurement circuit, and after capacitive compensation, an electromagnetic resonance design is implemented. Measurement is performed under seawater conductivity-sensitive conditions, reducing the measurement error of the equipment and improving the sensor's measurement accuracy. Simultaneously, the magnetic core structure is omitted, significantly reducing the sensor's temperature coefficient and further improving measurement accuracy. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the connection method of a single-coil electromagnetic resonant seawater conductivity measurement sensor provided in an embodiment of this application.

[0022] Figure 2 This is a schematic diagram of a seawater conductivity measurement model provided in an embodiment of this application.

[0023] Figure 3 This is a schematic diagram of the internal structure of the measurement circuit provided in an embodiment of this application.

[0024] Figure 4 This is a schematic diagram of the composition structure of a single-coil electromagnetic resonant seawater conductivity measurement sensor provided in an embodiment of this application.

[0025] Figure 5 This is a schematic diagram of resonance curves at different conductivities provided in the embodiments of this application.

[0026] Figure 6 This is a schematic diagram of load voltage variation curves at different frequencies provided in the embodiments of this application.

[0027] Reference numerals: Measurement coil-1, Resonant circuit-2, Sampling resistor-3, Measurement circuit-4, Central processing unit-41, DDS signal generator-42, Sampling circuit-43, Measurement module-44, Amplitude measurement unit-441, Filtering circuit-442, AD conversion module-45, Connecting lead-5, Housing-6, Host computer-7, Storage chip-8. Detailed Implementation

[0028] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0029] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] Regarding inductive non-contact measurement, in 2012, a "Method and System for Measuring Downhole Medium Resistivity with a Single Coil" was published, demonstrating the feasibility of combining a single coil with related instruments to measure the resistivity of soil. However, the significant differences in soil topography and seawater conductivity make it difficult to use the same sensor. In 2021, a "Non-External Field Inductive Conductivity Sensor" was published, providing a non-external field inductive conductivity sensor for seawater and its internal structure. This sensor uses a dual-coil design and requires an outer shield and an embedded guide tube to restrict the seawater area. In 2022, a "Novel Seawater Conductivity Measurement Method and System" was published, demonstrating the enhancement effect of resonance technology on seawater conductivity measurement. However, this technology uses a dual-coil system, and the measurement results are also related to the distance between the two coils, adding difficulty to the design of seawater conductivity sensors. Currently, no one has combined magnetic resonance technology with a single coil to measure seawater conductivity parameters and designed this type of seawater conductivity sensor.

[0031] In view of this, in an exemplary embodiment, such as Figure 1 As shown, a single-coil electromagnetic resonant seawater conductivity measurement sensor is provided, comprising: a measuring coil 1, a resonant circuit 2, a sampling resistor 3, and a measuring circuit 4. The measuring coil 1 is connected in parallel with the resonant circuit 2; one end of the resonant circuit 2 is connected to one end of the measuring circuit 4, the other end of the resonant circuit 2 is connected to one end of the sampling resistor 3, and the other end of the sampling resistor 3 is connected to the other end of the measuring circuit 4.

[0032] The measuring coil 1 is placed in seawater. The measuring circuit 4 is used to generate an AC signal with a resonant frequency. After capacitive compensation by the resonant circuit 2, the signal is applied to both ends of the measuring coil 1. The measuring coil 1 is supplied with the capacitively compensated AC signal, which generates a high-frequency AC magnetic field in space. The high-frequency AC magnetic field excites high-frequency eddy currents in the seawater space, and the high-frequency eddy currents affect the current in the measuring coil 1. The measuring circuit 4 is also used to measure the voltage across the sampling resistor 3 to obtain the AC sampling signal of the voltage. Based on the AC sampling signal of the voltage, the seawater conductivity is obtained using the relationship between the sampling voltage and the seawater conductivity.

[0033] The working principle of the sensor in this application is as follows: The measuring circuit 4 generates a high-frequency sinusoidal AC signal with a resonant frequency. This high-frequency sinusoidal signal is applied across the measuring coil 1, thereby generating a high-frequency AC magnetic field in the seawater space. Since seawater is conductive, the high-frequency AC magnetic field excites high-frequency eddy currents in the underwater space. These eddy currents then affect the current in the measuring coil 1, resulting in a functional relationship between the current in the measuring coil 1 and the conductivity of the seawater. By measuring the voltage of the sampling resistor 3 and combining this with the relationship between the sampling voltage (also known as the load voltage) and the conductivity of the seawater, the conductivity of the tested seawater is obtained. Here, the high-frequency AC magnetic field refers to an AC magnetic field with a frequency greater than a preset threshold, and the high-frequency eddy current refers to an eddy current with an alternating frequency greater than a preset threshold.

[0034] As an alternative implementation method, theoretical derivation verifies that there is a certain relationship between the sampling voltage and the conductivity of seawater.

[0035] Seawater equivalent loop model as follows Figure 2 As shown, Figure 2 middle For the mutual inductance between the coil circuit and the seawater eddy current circuit, The left side is the coil circuit. The right side represents the seawater eddy current loop. At the circuit level, the seawater eddy current loop can be equivalent to an inductor and a resistor connected in series. The seawater eddy current loop is coupled to the excitation coil through the inductive component. The loop matrix can be obtained using Kirchhoff's laws: ; in, These represent the current, inductance, and resistance of the coil circuit, respectively. These represent the current, inductance, and resistance of the seawater eddy current loop, respectively. The input signal source voltage, The resonant frequency, It is the imaginary unit. , Let be the conductivity of seawater. After simplification, the loop impedance can be expressed as follows: ; ; in, and The equivalent circuit resistance and inductance values ​​can be physically interpreted as the resistance of the coil circuit to the conductivity of seawater. and the inductance of the coil circuit This had an effect, resulting in a change in the loop resistance value. and the changing loop inductance value The value that affects the subsequent circuit resistance and inductance is... and .

[0036] After calculation, from the resonant capacitor Impedance viewed from both ends The formula is: .

[0037] In an AC circuit containing inductors, capacitors, and resistors, the voltage and current across the circuit are generally out of phase. If the frequency is adjusted to make the voltage and current in phase, the circuit becomes purely resistive, a state known as circuit resonance. When the system inputs the resonant frequency, the electrical energy of the capacitor is converted into the magnetic energy of the inductor to the maximum extent, increasing the influence of seawater eddies on the coil impedance and making the circuit more sensitive to changes in seawater conductivity. In the resonant state, the current and voltage are in phase, and the circuit impedance contains only the real component; the imaginary part of the impedance at the resonant point is zero. The formula for the resonant frequency at this point is: .

[0038] Substituting the resonant frequency formula into the impedance... The formula, after approximation and simplification, gives the total impedance of the capacitor and coil connected in parallel as: .

[0039] By substituting into the voltage divider formula, the sampling resistor... Sampling voltage at both ends As follows, among which and It is related to the electrical conductivity of seawater.

[0040] .

[0041] Therefore, there is a certain relationship between the conductivity of seawater and the voltage across the sampling resistor, and this relationship can be used to measure the conductivity of seawater.

[0042] Based on theoretical derivation and verification, the following is a specific example of measuring the conductivity of seawater using polynomial fitting.

[0043] The method for determining the relationship between sampling voltage and seawater conductivity can be replaced by the following steps 101 to 105.

[0044] Step 101: Establish a polynomial fitting model of sampling voltage and seawater conductivity; the polynomial fitting model includes multiple coefficients to be fitted.

[0045] Step 102: Set up various water environments with different seawater conductivity.

[0046] In a constant-temperature conductivity water tank environment, various seawater conductivity values ​​were set. , … .in, , , They represent the electrical conductivity of the first type of seawater, the electrical conductivity of the second type of seawater, and the electrical conductivity of the third type of seawater, respectively. The electrical conductivity of seawater.

[0047] Step 103: Collect voltage measurements in the aquatic environment for each type of seawater conductivity.

[0048] Sensors were placed in aquatic environments with varying seawater conductivity to collect multiple voltage measurements. , .in, This represents the voltage measurement value in an aquatic environment with the first type of seawater conductivity. This represents the voltage measurement value in an aquatic environment with the second type of seawater conductivity. Indicates the first Voltage measurements in aquatic environments with varying seawater conductivity.

[0049] Step 104: Based on various seawater conductivity values ​​and voltage measurements in aquatic environments with each seawater conductivity, and based on the principle of minimizing error using the least squares method, obtain the value of each coefficient to be fitted when the error of the polynomial fitting model is minimized.

[0050] The collected voltage measurements are used to find the set of coefficients with the smallest least squares error through polynomial fitting (3rd order fitting).

[0051] Error of polynomial fitting model for: ; in, , , and All are fitting coefficients. Indicates the first One measurement data.

[0052] Step 105: Substitute the value of each coefficient to be fitted into the polynomial fitting model to obtain the relationship between the sampling voltage and the conductivity of seawater.

[0053] After obtaining all the values ​​of the coefficients to be fitted, the relationship between the sampling voltage and the conductivity of seawater can be obtained, and the conductivity can be measured in practice using this relationship.

[0054] As an optional implementation method, the relationship between sampling voltage and seawater conductivity is as follows: + .

[0055] As an optional implementation method, such as Figure 3 As shown, the measurement circuit 4 includes: a central processing unit 41, a DDS signal generator 42, a sampling circuit 43, a measurement module 44, and an AD conversion module 45. The central processing unit 41 controls the DDS signal generator 42 to generate an AC signal with a resonant frequency. The DDS signal generator 42 applies the generated AC signal with the resonant frequency to both ends of the measurement coil 1 after capacitive compensation by the resonant circuit 2. The sampling circuit 43 samples the voltage across the sampling resistor 3 using a differential measurement method to obtain an AC voltage sampling signal. The measurement module 44 measures the amplitude of the AC voltage sampling signal, generates an amplitude DC signal, and filters out noise from the amplitude DC signal to obtain a filtered amplitude DC signal. The AD conversion module 45 converts the filtered amplitude DC signal into an amplitude digital signal. The central processing unit 41 uses the amplitude digital signal and the relationship between the sampling voltage and seawater conductivity to obtain the seawater conductivity. The amplitude DC signal is a DC signal containing conductivity information.

[0056] The measurement module 44 may include an amplitude measurement unit 441 and a filtering circuit 442. The amplitude measurement unit 441 is used to measure the amplitude of the AC sampling signal of the voltage and generate an amplitude DC signal. The filtering circuit 442 is used to filter out noise in the amplitude DC signal to obtain a filtered amplitude DC signal.

[0057] In implementing this method, the DDS signal generator 42 uses the AD9833 chip, which can generate accurate sine signals within 3MHz and whose frequency can be controlled by a program, making it easy to adjust for resonance.

[0058] The resonant circuit 2 and sampling resistor 3 should be selected with capacitors and resistors having the smallest possible temperature drift coefficients to achieve resonant compensation of the coil voltage and improve measurement accuracy. The sampling circuit 43 uses a differential measurement method to directly measure the voltage across the sampling resistor 3. It should select instrumentation amplifiers or operational amplifiers with low noise, such as INA128 or AD8429. If the acquired signal is small, it can be amplified by 2 to 6 times in this part.

[0059] The amplitude measurement unit 441 selects the AD637 envelope detection chip, whose generated DC signal is equal to the effective value of the input AC signal. The filtering circuit 442 selects an active low-pass filter circuit and selects low-noise operational amplifiers, such as OP07 and OP27, to filter out noise in the electrical signal during the measurement process and improve the measurement accuracy. This achieves accurate signal measurement.

[0060] The AD conversion module 45 must use at least a 16-bit voltage acquisition chip, such as AD7606 or CS1237. In order to ensure the accuracy of the measurement, the AD chip needs to be connected to an external reference level.

[0061] The CPU processor used is the STM32F103 chip, and the ATMEGA162 chip can be selected as an alternative.

[0062] As an optional implementation method, such as Figure 4 As shown, the single-coil electromagnetic resonant seawater conductivity measuring sensor also includes: connecting leads 5. The two ends of the measuring coil 1 are connected to the two ends of the resonant circuit 2 respectively through the connecting leads 5.

[0063] The specific connection method is as follows: the measuring circuit 4 is connected to the measuring coil 1 through the connecting lead 5; the resonant circuit 2 is connected to the measuring coil 1 in parallel through the connecting lead 5, with both ends connected to achieve a resonance effect; the sampling resistor 3 is connected in series outside the resonant part to measure the total current. The resonant circuit 2 is a resonant capacitor.

[0064] As an optional implementation method, the following is still referred to Figure 4 The single-coil electromagnetic resonant seawater conductivity measuring sensor also includes: a housing 6. The resonant circuit 2, sampling resistor 3, and measuring circuit 4 are all housed within the housing 6. The measuring circuit 4 is mounted on a circuit board.

[0065] The measuring coil 1 adopts a planar spiral structure, allowing it to be placed in seawater. It utilizes the principle of electromagnetic induction to measure the conductivity parameter of seawater. The measuring circuit 4 includes sections for generating the AC excitation signal, sampling the AC signal from the coil, and calculating the conductivity. A sampling resistor 3 is connected in series within the coil circuit, and the sampling circuit 43 samples the voltage across its terminals. A resonant capacitor, acting as a compensating component, capacitively compensates for the inductive component of the coil, aiming to improve the circuit's responsiveness to changes in seawater conductivity, increase the numerical value of the parameter change, and thus improve measurement accuracy. The connecting lead 5 is a high-frequency shielded wire to prevent measurement errors caused by high-frequency signals to the sensor.

[0066] Figure 5 The variation trend of voltage across the load (sampling resistor 3) with frequency is given under different seawater conductivity conditions. Figure 5 The extreme point in the equation is the resonant point, and the frequency is the resonant frequency. At the resonant point, the voltage is most affected by the conductivity of seawater.

[0067] Figure 6 The diagram shows the variation of load voltage with seawater conductivity at different frequencies. The resonant frequency of 1422 kHz exhibits a clear trend with respect to seawater conductivity, which can be used for fitting and measurement of seawater conductivity.

[0068] This application establishes the relationship between the sampling voltage of the sampling resistor in underwater conditions and the conductivity of seawater; and, in conjunction with magnetic resonance technology, performs relevant derivations, verifying the improvement in sampling accuracy under resonant conditions, which is beneficial for accurate measurement of seawater conductivity.

[0069] This application proposes a single-coil electromagnetic resonant seawater conductivity measurement sensor. In terms of sensor structure, a single planar helical coil replaces the traditional two wound coils, reducing the design and assembly difficulty of the sensor. An open measurement structure is designed, eliminating the need for a seawater guide tube; the sensor can be placed in seawater for measurement. Combined with resonant technology, measurements are performed under conductivity-sensitive conditions, which can improve the sensor's measurement accuracy and eliminate the need for a magnetic core structure, greatly reducing the sensor's temperature coefficient.

[0070] Advantages of this application: This application provides a novel design scheme for a seawater conductivity measurement sensor, which solves the problem of the complex internal structure of existing traditional inductive seawater conductivity sensors. It simplifies the two measurement coils required by the traditional inductive seawater conductivity sensor to a single coil, saving half of the equipment space. Furthermore, it includes a related sensor system design, which simplifies the internal complexity of the equipment and incorporates electromagnetic resonance design, thereby reducing the measurement error of the equipment in terms of seawater conductivity and improving the sensor's measurement accuracy.

[0071] Structurally, the sensor of this application is smaller and simpler than traditional inductive seawater conductivity sensors; in terms of measurement principle, the sensor of this application is more accurate and sensitive, thus exhibiting superior performance compared to traditional sensors.

[0072] Based on the same inventive concept, this application also provides a single-coil electromagnetic resonant seawater conductivity measurement sensing system that utilizes the single-coil electromagnetic resonant seawater conductivity measurement sensor described above. The solution provided by this system is similar to the solution described in the above method; therefore, the specific limitations of one or more embodiments of the single-coil electromagnetic resonant seawater conductivity measurement sensing system provided below can be found in the limitations of the single-coil electromagnetic resonant seawater conductivity measurement sensor described above, and will not be repeated here.

[0073] In one exemplary embodiment, such as Figure 3 As shown, a single-coil electromagnetic resonant seawater conductivity measurement sensing system is provided, comprising: a host computer 7, a storage chip 8, and the aforementioned single-coil electromagnetic resonant seawater conductivity measurement sensor. Both the host computer 7 and the storage chip 8 are connected to the measurement circuit 4 in the single-coil electromagnetic resonant seawater conductivity measurement sensor. The measurement circuit 4 is used to transmit the seawater conductivity to the host computer 7 and the storage chip 8.

[0074] The central processing unit (CPU) can store data, send data to the storage chip 8 for storage, or send data to the host computer 7 for processing.

[0075] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0076] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A single-coil electromagnetic resonant seawater conductivity measuring sensor, characterized in that, The single-coil electromagnetic resonant seawater conductivity measurement sensor includes: a measurement coil, a resonant circuit, a sampling resistor, and a measurement circuit; The measuring coil is connected in parallel with the resonant circuit; one end of the resonant circuit is connected to one end of the measuring circuit, the other end of the resonant circuit is connected to one end of the sampling resistor, and the other end of the sampling resistor is connected to the other end of the measuring circuit. The measuring coil is placed in seawater. The measuring circuit generates an AC signal at the resonant frequency, which is capacitively compensated by the resonant circuit and then applied to both ends of the measuring coil. The capacitively compensated AC signal is passed through the measuring coil, generating a high-frequency AC magnetic field in space. The high-frequency AC magnetic field excites high-frequency eddy currents in the seawater space, and the high-frequency eddy currents affect the current in the measuring coil. The measuring circuit is also used to measure the voltage across the sampling resistor to obtain the AC sampling signal of the voltage. Based on the AC sampling signal of the voltage, the seawater conductivity is obtained using the relationship between the sampling voltage and the seawater conductivity.

2. The single-coil electromagnetic resonant seawater conductivity measuring sensor according to claim 1, characterized in that, The relationship between the sampling voltage and the seawater conductivity is as follows: + ； In the formula, The electrical conductivity of seawater, For sampling voltage, , , and All are fitting coefficients.

3. The single-coil electromagnetic resonant seawater conductivity measuring sensor according to claim 1, characterized in that, The method for determining the relationship between the sampling voltage and the conductivity of seawater specifically includes: A polynomial fitting model is established between the sampling voltage and the seawater conductivity; the polynomial fitting model includes multiple coefficients to be fitted. Set up various water environments with different seawater conductivity; Voltage measurements were collected in the aquatic environment for each type of seawater conductivity. Based on various seawater conductivity values ​​and voltage measurements in aquatic environments for each type of seawater conductivity, and based on the principle of minimizing error using the least squares method, the values ​​of each coefficient to be fitted are obtained when the error of the polynomial fitting model is minimized. By substituting the value of each coefficient to be fitted into the polynomial fitting model, the relationship between the sampling voltage and the conductivity of seawater is obtained.

4. The single-coil electromagnetic resonant seawater conductivity measuring sensor according to claim 1, characterized in that, The measurement circuit includes: a central processing unit, a DDS signal generator, a sampling circuit, a measurement module, and an AD conversion module; The central processing unit is used to control the DDS signal generator to generate an AC signal at the resonant frequency; The DDS signal generator is used to generate an AC signal at the resonant frequency, which, after capacitive compensation by the resonant circuit, is applied to both ends of the measuring coil. The sampling circuit is used to sample the voltage across the sampling resistor in a differential measurement manner to obtain an AC sampling signal of the voltage. The measurement module is used to measure the amplitude of the AC sampling signal of the voltage, generate an amplitude DC signal, and filter out noise in the amplitude DC signal to obtain a filtered amplitude DC signal. The AD conversion module is used to convert the filtered amplitude DC signal into an amplitude digital signal; The central processing unit is also used to obtain the seawater conductivity based on the amplitude digital signal and the relationship between the sampling voltage and the seawater conductivity.

5. The single-coil electromagnetic resonant seawater conductivity measuring sensor according to claim 4, characterized in that, The measurement module includes: an amplitude measurement unit and a filtering circuit; The amplitude measurement unit is used to measure the amplitude of the AC sampling signal of the voltage and generate an amplitude DC signal; The filter circuit is used to filter out noise in the amplitude DC signal to obtain the filtered amplitude DC signal.

6. The single-coil electromagnetic resonant seawater conductivity measuring sensor according to claim 1, characterized in that, The single-coil electromagnetic resonant seawater conductivity measurement sensor also includes: connecting leads; The two ends of the measuring coil are connected to the two ends of the resonant circuit one by one through connecting leads.

7. The single-coil electromagnetic resonant seawater conductivity measuring sensor according to claim 1, characterized in that, The single-coil electromagnetic resonant seawater conductivity measurement sensor also includes: a housing; The resonant circuit, sampling resistor, and measurement circuit are all housed inside the casing.

8. The single-coil electromagnetic resonant seawater conductivity measuring sensor according to claim 1, characterized in that, The measuring coil adopts a planar helical structure.

9. The single-coil electromagnetic resonant seawater conductivity measuring sensor according to claim 5, characterized in that, The central processing unit is either an STM32F103 chip or an ATMEGA162 chip; The DDS signal generator uses the AD9833 chip; The sampling circuit is an instrumentation amplifier or an operational amplifier; The amplitude measurement unit is an AD637 envelope detection chip; The filter circuit is an active low-pass filter circuit; The AD conversion module is a 16-bit voltage acquisition chip.

10. A single-coil electromagnetic resonant seawater conductivity measurement sensing system, characterized in that, The single-coil electromagnetic resonant seawater conductivity measurement sensing system includes: a host computer, a storage chip, and the single-coil electromagnetic resonant seawater conductivity measurement sensor according to any one of claims 1-9; Both the host computer and the storage chip are connected to the measurement circuit in the single-coil electromagnetic resonant seawater conductivity measurement sensor; The measurement circuit is used to send the seawater conductivity to the host computer and the storage chip.

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