Switching control metal mesh modulated seawater electric field measurement system and method

Abstract

The application provides a kind of switch control metal screen modulation seawater electric field measurement system and method, realize high resolution, high signal-to-noise ratio seawater electric field measurement.The application uses metal screen to obtain seawater electric field modulation signal by switching and shielding cover intermittent on-off.Through the matching circuit of measuring electrode, the voltage and power received on the measuring electrode can be improved.Frequency conversion circuit and narrow band filter can suppress various interference and noise closer to useful signal, greatly improve signal-to-noise ratio.Lock-in amplifier further filters out noise signal, while demodulating electric field modulation signal, measures the amplitude of measured electric field.This measuring instrument system suppresses seawater electric field drift and noise, improves the reliability, repeatability, reproducibility, signal-to-noise ratio and resolution of measurement, can measure weak seawater electric field, constitutes sensor array and vector electric field measuring instrument, and is applied to more extensive field.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ocean electric field measurement, in particular to a switch control metal mesh modulated seawater electric field measurement system and method. BACKGROUND

[0002] In the existing ocean measurement system, mainly acoustic and magnetic detection is adopted. The acoustic and magnetic measurement in seawater is relatively mature, and the electric field measurement is relatively less studied and more difficult. In the ocean, which is a special propagation medium with a large number of ion-conducting solutions, the high-frequency electromagnetic field attenuates very greatly, and the physical methods and electric field sensors that can measure the electric field in the air are almost impossible to be applied to the ocean. Therefore, a new high-sensitivity electric field sensor and instrument need to be researched according to the special equivalent circuit and propagation characteristics of the ocean electric field, the adverse effects of seawater on the electric field propagation need to be solved, and the measurement and accurate positioning of the long-distance and weak electric field in the ocean need to be realized. This is of great significance to the research of ocean resource investigation, mineral discovery, marine biology and ship movement.

[0003] The low-frequency / direct-current electric field of the ocean is measured by using the natural potential method, which is widely used at present. The principle is that two potential sensors measure the potential difference in a distance of seawater to measure the electric field. The farther the distance of the measured electric field source is, the greater the distance of the two measurement electrodes needs to be. Although researchers have continuously discovered new materials and improved the noise of the electrode, due to the fact that the measurement sensor does not consider the low-frequency / direct-current electromagnetic field drift and the unavoidable ocean environment electric field interference, it is greatly affected by the seawater environment and other factors, in addition, the matching problem of the measurement probe is not considered, when the distance is far, not only the distance of the measurement electrode needs to be large, but also the sensitivity of the measurement is poor, and it is difficult to be used for the detection of long-distance, small interval and weak electric field signal.

[0004] Another type is a modulation type electric field sensor with mechanical modulation, field grinding and chopper circuit added in front of the electric field measurement sensor, which is used to reduce the influence of low-frequency ocean electric field drift and circuit drift. This kind of sensor and circuit can suppress the drift through mechanical modulation and chopper circuit. However, the mechanical modulation frequency is low, and it will stir up waves and produce interference, and the chopper circuit can only improve the drift of the receiving circuit, without considering the matching of the electric field transducer and the received signal, so the maximum sensor output voltage, the lowest drift and the highest signal-to-noise ratio cannot be obtained, and the sensor sensitivity is low. It can be seen that the traditional representative electric field sensing principle and instrument cannot meet the application requirements of long-distance ocean weak electric field detection.

[0005] Seawater has good conductivity, high frequency electric field cannot be transmitted over long distances, only very low frequency, even static electric field can be transmitted over long distances, the regulation and control of electric field signal in seawater is completely different from that in air, not only the electric field transmission should be considered, but also the conduction movement of electric field charge, therefore, a new method of high frequency electronic regulation and control of measured electric field and matching electrode output is needed, which not only greatly improves the modulation frequency and reduces the matching inductance, but also uses small measurement electrode to meet the higher sensitivity measurement. SUMMARY

[0006] In view of the defects in the prior art, the purpose of the present application is to provide a switch-controlled metal mesh modulated electric field measurement system and method for seawater.

[0007] According to the present application, a switch-controlled metal mesh modulated electric field measurement system for seawater is provided, comprising:

[0008] Shielding cover 103, metal mesh 102, measurement electrode 104, wire 105, electronic switch 106, and matching circuit 109, amplification and filtering circuit 110, frequency conversion circuit 111, narrowband filter 112, lock-in amplifier 113, and computer 114

[0009] The measurement electrode 104 and the metal mesh 102 are arranged in the shielding cover 103, and the measurement electrode 104 and the metal mesh 102 are arranged parallel to the opening surface of the shielding cover 103, and the metal mesh 102 is close to the opening surface of the shielding cover 103; the metal mesh 102 is connected to the shielding cover 103 through the wire 105 and the electronic switch 106; the measurement electrode 104 is connected to the matching circuit 109 through the wire 105;

[0010] The matching circuit 109, the amplification and filtering circuit 110, the frequency conversion circuit 111, the narrowband filter 112, the lock-in amplifier 113, and the computer 114 are connected in sequence.

[0011] Preferably, the holes of the metal mesh 102 meet the preset requirements.

[0012] Preferably, the measurement electrode 104 uses inert silver or carbon fiber electrode material; the metal mesh 102 and the shielding cover 103 use titanium alloy or navy copper metal material.

[0013] Preferably, the computer 114 generates a modulation control 116 to control the electronic switch 106 to be on or off; when the electronic switch 106 is on, the metal mesh 102 is short-circuited with the shield 103, the opening of the shield 103 is filled by the metal mesh 102, the seawater electric field is blocked, so that the electric field cannot reach the measuring electrode 104; when the electronic switch 106 is off, the seawater electric field can reach the measuring electrode 104 through the opening of the shield 103 and the metal mesh 102.

[0014] Preferably, the metal mesh 102 is intermittently connected and disconnected with the shield 103 through the electronic switch 106, so as to obtain a seawater electric field modulation signal; the seawater electric field modulation signal is input into the measuring electrode 104, the seawater electric field modulation signal obtained is converted into a corresponding voltage signal by the measuring electrode 104, and then the voltage signal is input into the matching circuit 109, so as to improve the corresponding voltage and power.

[0015] Preferably, the output voltage of the matching circuit 109 is sequentially input into the amplification and filtering circuit 110, the frequency conversion circuit 111, the narrowband filter 112 and the lock-in amplifier 113, so as to obtain a direct current signal reflecting the modulation amplitude.

[0016] The amplification and filtering circuit 110 is configured to improve the output voltage and suppress interference and noise far away from the frequency of the modulation signal.

[0017] The frequency conversion circuit 111 is configured to improve the frequency of the frequency conversion.

[0018] The narrowband filter 112 is configured to filter out interference and noise within a preset range from the frequency conversion signal.

[0019] The lock-in amplifier 113 is configured to filter out noise signals at non-modulation frequencies, demodulate the modulation signal, and obtain a direct current signal reflecting the modulation amplitude.

[0020] Preferably, the direct current signal is input into the computer 114 through A / D conversion to complete the measurement.

[0021] Preferably, the computer 114 generates a frequency control 117 to control the frequency conversion circuit.

[0022] Preferably, the narrowband filter 112 adopts a bulk acoustic wave filter or a surface acoustic wave filter.

[0023] According to the present application, a seawater electric field measurement method using a switch-controlled metal mesh modulation system is provided.

[0024] Step S1: the computer 114 generates a modulation control 116 to turn on and off the electronic switch 106, so that the metal net 102 is intermittently connected with the shield 103, and a seawater electric field modulation signal is obtained;

[0025] Step S2: the seawater electric field modulation signal is converted into a corresponding voltage signal by using the measuring electrode 104;

[0026] Step S3: the voltage signal is improved by using the matching circuit 109;

[0027] Step S4: the output voltage is improved, and the interference and noise far away from the modulation signal frequency are suppressed by using the amplification and filtering circuit;

[0028] Step S5: the frequency is raised by using the frequency conversion circuit;

[0029] Step S6: the interference and noise within a preset range of the frequency conversion signal are filtered out by using the narrowband filter;

[0030] Step S7: the noise signal at the non-modulation frequency is filtered out by using the lock-in amplifier, and the modulation signal is demodulated to obtain a direct current signal capable of reflecting the modulation amplitude;

[0031] Step S8: the direct current signal is input into the computer 114 through A / D conversion to complete the measurement.

[0032] Compared with the prior art, the present application has the following beneficial effects:

[0033] 1. The present application adopts the electronic switch to control the metal net to modulate the electric field of seawater, the metal net modulation structure is small in size, high in modulation frequency and large in modulation depth, can suppress the seawater electric field drift and noise, and improve the reliability, repeatability and reproducibility of the measurement;

[0034] 2. The present application adopts seawater modulation and matching output to improve the electric field measurement sensitivity of the small-size sensor, and also makes the phased sensor array and vector electric field measurement possible due to the significant reduction of the sensor size and spacing, and significantly expands the application range of the underwater electric field measurement;

[0035] 3. The present application adopts the noise signal suppression processing and demodulation circuit, and significantly reduces the noise and interference influence through the frequency conversion and narrowband filtering technology, improves the signal-to-noise ratio and resolution of the measurement, and can measure the more weak seawater electric field;

[0036] 4. The seawater modulation method provided by the present application is different from the modulation of changing the seawater electric field direction, completely blocks the measured electric field, can be suitable for various frequency seawater electric field and charge modulation of movement speed, and has obvious superiority. BRIEF DESCRIPTION OF DRAWINGS

[0037] Other features, objects, and advantages of the application will become apparent from the following detailed description of non-limiting embodiments, when read in connection with the following accompanying drawings:

[0038] Figure 1 The schematic diagram of the electric field measurement system for switch-controlled metal mesh modulation of seawater.

[0039] Figure 2 The schematic diagram of the structure for switch-controlled metal mesh modulation of seawater.

[0040] Figure 3 The schematic diagram of the principle of the measurement electrode and the matching circuit.

[0041] Figure 4 The schematic diagram of the principle of the cascaded filter circuit of the acoustic wave filter with multiple resonant frequencies being completely identical.

[0042] Figure 5 The schematic block diagram of the up-conversion circuit.

[0043] Figure 6 The schematic block diagram of the lock-in amplifier.

[0044] Figure 7 The schematic diagram of the principle of the surface acoustic wave narrowband filter.

[0045] Wherein, 100-electric field source; 101-seawater; 102-metal mesh; 103-shield; 104-measurement electrode; 105-conductor; 106-electronic switch; 107-frequency conversion receiving and matching; 108-frequency conversion signal; 109-matching circuit; 110-amplification and filter circuit; 111-frequency conversion circuit; 112-narrowband filter; 113-lock-in amplifier; 114-computer; 115-noise suppression signal processing and demodulation circuit; 116-modulation control; 117-frequency control. DETAILED DESCRIPTION

[0046] The application will be described in detail below with specific embodiments. The following embodiments will help those skilled in the art to further understand the application, but do not limit the application in any form. It should be pointed out that those skilled in the art can make several changes and improvements without departing from the concept of the application. These are within the scope of protection of the application.

[0047] Example 1

[0048] The application provides an electric field measurement system for switch-controlled metal mesh modulation of seawater, as Figure 1As shown, it comprises: a shield 103, a metal mesh 102, a measuring electrode 104, a wire 105, an electronic switch 106, a matching circuit 109, an amplification and filter circuit 110, a frequency conversion circuit 111, a narrow-band filter 112, a lock-in amplifier 113 and a computer 114

[0049] The measuring electrode 104 and the metal mesh 102 are arranged in the shield 103, and the measuring electrode 104 and the metal mesh 102 are arranged parallel to the opening surface of the shield 103, and the metal mesh 102 is close to the opening surface of the shield 103; the metal mesh 102 is connected with the shield 103 through the wire 105 and the electronic switch 106; the measuring electrode 104 is connected with the matching circuit 109 through the wire 105;

[0050] The matching circuit 109, the amplification and filter circuit 110, the frequency conversion circuit 111, the narrow-band filter 112, the lock-in amplifier 113 and the computer 114 are connected in sequence.

[0051] Wherein, the metal mesh 102 with large holes is installed in front of the measuring electrode 104, and the metal mesh 102 is connected with the shielding cover 103 through the switch 106. When the switch 106 is off, the electric field source 100 in the seawater can pass through the metal mesh 102 with large holes to the measuring electrode 104 without any obstruction; when the electronic switch 106 is on, the metal mesh 102 is connected with the shielding cover 103, the electric charges generated by the metal mesh 102 are absorbed by the shielding cover 103, and the electric field in the seawater 101 is blocked by the metal mesh 102. The electric field reaching the measuring electrode 104 is modulated by alternating the on and off of the electronic switch 106. The seawater modulation method provided by the present application is different from the modulation of changing the direction of the seawater electric field, which completely blocks the measured electric field, and can adapt to the charge modulation of seawater electric field with various frequencies and motion speeds, and has obvious advantages. Since the modulation completely changes the characteristics of the seawater electric field, the voltage and power received on the measuring electrode 104 can be obviously improved by adding a matching circuit 109 after the electric field / voltage conversion of the measuring electrode 104, which is also a feature that the traditional modulation does not have. The matching circuit 109 passes through an amplifier and a filter 110 to improve the output voltage and suppress the interference and noise far away from the frequency of the modulation signal. Then, the frequency conversion circuit 111 is used to improve the frequency of the frequency conversion, so that the interference and noise far away from the frequency conversion signal 108 can be well filtered out through the narrowband filter 112. The lock-in amplifier 113 has two functions, one of which is to further filter out the noise signal at the non-modulation frequency, and the other of which is to demodulate the modulation signal into a direct current signal reflecting the modulation amplitude. The direct current signal is sent into the computer 114 for measurement through A / D conversion. The modulation control 116 of the electronic switch 106 and the frequency control 117 of the frequency conversion circuit 111 are both generated by the computer 114. The present application modulates the measured electric field through the electrically controlled metal mesh 102, and then performs matching output, the modulation frequency can be very high, the output amplitude is improved, and the modulation degree can be close to 100%, which avoids the influence of the traditional modulation method and the motion speed of the electric charge on the modulation, and improves the amplitude of the frequency conversion modulation signal. This is also impossible for the traditional mechanical modulation and electric control modulation, which improves the resolution and frequency measurement range of the measurement system, greatly reduces the size, and improves the output amplitude. This also lays a foundation for the future array sensor, which can form an electric field phased array sensor system, measure the vector electric field and electric field distribution, and greatly expand the measurement range of the ocean electric field.

[0052] Example 2

[0053] Embodiment 2 is a preferred example of Embodiment 1

[0054] According to the present application, a switch-controlled metal mesh modulation seawater electric field measurement system is provided, which comprises: a frequency conversion receiving and matching 107, a noise signal suppression processing and demodulation circuit 115, and a computer 114.

[0055] Wherein, the frequency conversion receiving and matching 107 includes: metal mesh 102, shield 103, measuring electrode 104, wire 105, electronic switch 106, matching circuit 109; the computer 114 controls the on-off of the electronic switch 106 through the modulation control 116, the metal mesh 102 blocks the electric field when the switch is on, the shield 103 cooperates with the metal mesh 102 so that the electric field cannot reach the measuring electrode 104, the electronic switch 106 does not affect the electric field to reach the measuring electrode 104 when it is off, the electronic switch 106 realizes the modulation of the electric field by alternating on-off, and the matching circuit 109 enables the electric field to have maximum output voltage and power output;

[0056] The noise signal processing and demodulation circuit 115 includes: amplification and filtering circuit 110, frequency conversion circuit 111, narrow-band filter 112 and lock-in amplifier 113; the amplification and filtering circuit 110 amplifies the output voltage and filters out noise and interference far away from the modulation frequency, the frequency conversion circuit 111 up-converts the modulation signal frequency to the narrow-band filter 112, the narrow-band filter 112 filters out noise and interference very close to the modulation frequency, and the lock-in amplifier 113 further suppresses noise while demodulating the modulation signal into a direct current signal representing the amplitude of the modulation signal, which is sent to the computer 114. The frequency control 117 of the frequency conversion signal 108 is generated by the computer 114. After the above-mentioned noise signal processing and demodulation circuit 115, the noise and interference are well suppressed, thereby improving the signal-to-noise ratio and the resolution of the electric field.

[0057] The metal mesh 102 is placed in front of the measuring electrode 104 and together with the measuring electrode 104 in the shield, and the electronic switch 106 is connected to the metal mesh 102 and the shield 103 respectively, as shown in Figure 2 . The measuring electrode uses stable inert silver or carbon fiber electrode material, and the metal mesh and the shield use titanium alloy or navy copper metal material resistant to seawater corrosion. When the switch is off, the seawater electric field can reach the measuring electrode through the opening of the shield and the metal mesh, and the metal mesh hardly attenuates the electric field; when the switch is on, the metal mesh and the shield are short-circuited, the opening of the shield is filled with the metal mesh, and the ocean electric field is blocked, thereby realizing the modulation of the ocean electric field signal.

[0058] Seawater is conductive, and the electric field propagation can be equivalent to the parallel connection of resistors R0, R1, R2 and R3 and capacitors C0, C1, C2 and C3, as shown in Figure 3 . The metal mesh is controlled by the switch S1 to modulate the electric field. The measuring electrode can be equivalent to the series-parallel connection of resistors R Sl , R ctl and C ctl , R mTo measure the resistance between the measuring electrodes and the shield, matching is necessary to achieve the maximum signal output from the measuring electrodes. Since the equivalent circuit after the electric field passes through the measuring electrodes consists of several resistors and capacitors in parallel, matching requires connecting an inductive element to the load. Considering the low resistance of seawater and the very high impedance of the load, impedance transformation is also necessary. Therefore, a transformer is introduced, and a capacitor C is connected to the output. L This matching circuit ensures that the primary and secondary circuits of the transformer resonate at the same frequency, and that the equivalent resistances of the primary and secondary circuits are the same at the resonant frequency. This achieves conjugate impedance matching. At this point, the measuring electrodes obtain the maximum output voltage and power, and the signal-to-noise ratio is also improved.

[0059] The amplifier uses a traditional low-noise amplifier circuit, and the filter uses a traditional multi-stage bandpass filter. However, due to the imperfect performance of bandpass filters, even multi-stage bandpass filters struggle to effectively suppress noise signals close to the frequency of the electric field modulation signal. Therefore, a narrowband filter is added, employing a bulk acoustic wave (FBAR) filter. This ensures that only signals very close to the resonant frequency pass through by cascading one or more FBAR filters with identical resonant frequencies. Figure 4 As shown. Where Z in and Z out These are the input impedance and output impedance, respectively. These values ​​are typically very large and do not affect the input and output characteristics. Alternatively, a surface acoustic wave (SAW) filter can be used for narrowband filters, such as... Figure 7 As shown, a surface acoustic wave (SAW) filter consists of two interdigital transducers built on a piezoelectric substrate. The transmitting and receiving interdigital transducers are identical. The transmitted SAW wave is transmitted to the receiving interdigital transducer to obtain a signal with a very narrow bandwidth, typically in the range of tens to hundreds of MHz, which can effectively filter out various noises.

[0060] Since the frequency of the seawater modulated electric field signal cannot be the same as the frequency of the acoustic filter, a frequency converter circuit is needed to transform the frequency of the modulated signal to the resonant frequency of the bulk acoustic filter, thereby achieving narrowband filtering. The up-conversion effect can be achieved using a traditional multiplier and bandpass filter, such as... Figure 5 As shown. The input signal is the amplified and filtered signal after modulation by the seawater electric field, with a frequency of f0. The frequency control signal is a high-frequency signal with a frequency of f. S After passing through the multiplier, the new signal includes the sum and difference of the harmonic frequencies of the two signals. By setting an appropriate bandpass filter, the sum-frequency signal (f) of the two signals can be obtained. S +f0), here is the bandpass filter, which is Figure 4 A narrowband filter is formed by cascading one or more acoustic filters with identical resonant frequencies.

[0061] To further reduce the impact of various noise signals in the ocean on measurement resolution, a lock-in amplifier with narrowband filtering is used to improve the signal-to-weight ratio, and the modulated signal is demodulated, such as... Figure 6 As shown. Input signal V i The signal is an up-converted signal with a frequency of f. S +f0, after being amplified, is fed into multipliers 1 and 2 respectively. The control signal frequency is the same as the input signal, also f. S +f0, after passing through the quadrature pulse generation circuit, generates quadrature pulse signals and in-phase pulse signals respectively. These are multiplied by multipliers 1 and 2, respectively, and then passed through low-pass filters 1 and 2 to obtain two quadrature signals. After passing through the square root operation circuit, a DC signal related only to the amplitude of the input signal is obtained, thus achieving demodulation of the input signal. Here, the lock-in amplifier is also a narrowband filter circuit, further improving the signal-to-noise ratio. The output of the lock-in amplifier is converted by a computer A / D converter to send the measured seawater electric field amplitude to the computer.

[0062] The computer outputs a modulation control signal, which turns on the electronic switch 106, thereby modulating the seawater electric field. Figure 1 As shown. The control signal frequency is f0-f1, where f1 is the input seawater signal frequency. Since f0 >> f1, the control signal frequency is approximately f0. Simultaneously, the computer generates a frequency control signal for the frequency converter circuit, adjusting the modulation signal frequency to the resonant frequency of the narrowband filter to suppress various noises, thereby detecting weak electric field signals.

[0063] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A system for measuring the electric field of seawater modulated by a switch-controlled metal mesh, characterized in that, include: The components include a shield (103), a metal mesh (102), measuring electrodes (104), wires (105), an electronic switch (106), a matching circuit (109), an amplification and filtering circuit (110), a frequency conversion circuit (111), a narrowband filter (112), a lock-in amplifier (113), and a computer (114). The measuring electrode (104) and the metal mesh (102) are disposed inside the shielding cover (103), and the measuring electrode (104), the metal mesh (102) and the opening surface of the shielding cover (103) are arranged parallel to each other, with the metal mesh (102) close to the opening surface of the shielding cover (103); the metal mesh (102) is connected to the shielding cover (103) through the wire (105) and the electronic switch (106); the measuring electrode (104) is connected to the matching circuit (109) through the wire (105); The matching circuit (109), the amplification and filtering circuit (110), the frequency conversion circuit (111), the narrowband filter (112), the lock-in amplifier (113), and the computer (114) are connected in sequence.

2. The electric field measurement system for modulating seawater using a switch-controlled metal mesh according to claim 1, characterized in that, The holes in the metal mesh (102) meet the preset requirements.

3. The electric field measurement system for modulating seawater by switching a metal mesh according to claim 1, characterized in that, The measuring electrode (104) is made of inert silver or carbon fiber electrode material; the metal mesh (102) and the shield (103) are made of titanium alloy or naval copper metal material.

4. The electric field measurement system for modulating seawater using a switch-controlled metal mesh according to claim 1, characterized in that, The computer (114) generates modulation control (116) to turn the electronic switch (106) on or off; when the electronic switch (106) is on, the metal mesh (102) is short-circuited with the shield (103), the opening of the shield (103) is filled by the metal mesh (102), the seawater electric field is blocked, so that the electric field cannot reach the measuring electrode (104); when the electronic switch (106) is off, the seawater electric field can reach the measuring electrode (104) through the opening of the shield (103) and the metal mesh (102).

5. The switch-controlled metal mesh modulation seawater electric field measurement system according to claim 4, characterized in that, The metal mesh (102) is intermittently switched on and off with the shield (103) by the electronic switch (106) to obtain a seawater electric field modulation signal; the seawater electric field modulation signal is input to the measuring electrode (104), and the measuring electrode (104) converts the obtained seawater electric field modulation signal into a corresponding voltage signal, and then inputs the voltage signal into the matching circuit (109) to increase the corresponding voltage and power.

6. The electric field measurement system for modulating seawater with a switch-controlled metal mesh according to claim 5, characterized in that, The output voltage of the matching circuit (109) passes sequentially through the amplification and filtering circuit (110), the frequency conversion circuit (111), the narrowband filter (112), and the lock-in amplifier (113) to obtain a DC signal that reflects the modulation amplitude. The amplification and filtering circuit (110) is used to increase the output voltage and suppress interference and noise far from the modulation signal frequency; The frequency converter circuit (111) is used to increase the frequency of the frequency converter; The narrowband filter (112) is used to filter out interference and noise within a preset range of the distance-converted frequency signal; The lock-in amplifier (113) is used to filter out noise signals at non-modulated frequencies and demodulate the modulated signal to obtain a DC signal that reflects the modulation amplitude.

7. The switch-controlled metal mesh modulation seawater electric field measurement system according to claim 6, characterized in that, The DC signal is input into the computer (114) through A / D conversion to complete the measurement.

8. The electric field measurement system for modulating seawater using a switch-controlled metal mesh according to claim 1, characterized in that, The computer (114) generates frequency control (117) for the frequency conversion circuit.

9. The electric field measurement system for modulating seawater using a switch-controlled metal mesh according to claim 1, characterized in that, The narrowband filter (112) is a bulk acoustic wave filter or a surface acoustic wave filter.

10. A method for measuring the electric field of seawater modulated by a switch-controlled metal mesh, characterized in that, The electric field measurement system for modulating seawater by a switch-controlled metal mesh, as described in any one of claims 1 to 9, performs the following operations: Step S1: The computer (114) generates modulation control (116) and the electronic switch (106) is turned on and off, thereby causing the metal mesh (102) and the shield (103) to be intermittently switched on and off, so as to obtain the seawater electric field modulation signal; Step S2: Use the measuring electrode (104) to convert the seawater electric field modulation signal into a corresponding voltage signal; Step S3: Use the matching circuit (109) to increase the voltage signal; Step S4: Use amplification and filtering circuits to increase the output voltage and suppress interference and noise that are far from the modulation signal frequency; Step S5: Increase the frequency of the inverter using a frequency converter circuit; Step S6: Use a narrowband filter to filter out interference and noise within a preset range of the distance-converted frequency signal; Step S7: Use a lock-in amplifier to filter out noise signals at non-modulated frequencies and demodulate the modulated signal to obtain a DC signal that reflects the modulation amplitude; Step S8: Input the DC signal into the computer (114) through A / D conversion to complete the measurement.

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