Mechanical modulation ocean static electric field non-contact measuring device

Abstract

The application provides a mechanical modulation ocean static electric field non-contact measuring device, which does not need to place two probes at a long distance and directly measures the device by using mechanical modulation ocean static electric field at a long distance. The application uses a mechanical turntable to interval on-off static electric field, and modulates the static electric field to a fixed AC frequency signal. A measurement electrode and a reference electrode output signal differential amplifier is used to suppress common-mode noise interference signals, and a lock-in amplifier narrow-band filter is used to suppress wide-band noise signals other than the modulation frequency, so that the influence of various noises and interferences in the ocean is greatly reduced. The detection method provided by the application can be applied to electric field measurement of minerals, ships, water flow and aquatic plants in liquid media such as seawater, lake water, river water and underground water, and has the characteristics of small drift, high measurement resolution and wide applicability.

Description

Technical Field

[0001] This invention relates to the technical field of marine electric field measurement, and more specifically, to a non-contact measurement device for mechanically modulated marine static electric fields. Background Technology

[0002] The decay relationship of ocean electric fields with distance follows the skin effect; static or quasi-static electric fields decay slowly and can be transmitted over long distances in seawater. Measuring static and quasi-static ocean electric fields is of great value for marine activities such as marine mineral discovery, biological monitoring, and long-distance ship detection. Due to the excellent conductivity of seawater, the methods for measuring its electric field are completely different from those in air. Traditional ocean electric field measurement uses the natural potential method, which utilizes the voltage division relationship between the resistance of two measuring electrodes and the object being measured in seawater to indirectly and non-contactly measure the electric field. For long-distance electric field measurements, although increasing the distance between the measuring electrodes can increase the voltage distribution of the equivalent resistance of the seawater, interference fields generated by seawater fluctuations and the surrounding environment significantly reduce the resolution of long-distance electric field measurements. Especially for static electric fields, it is difficult to distinguish between the static electric field received by the two electric field measurement probes and common-mode interference, posing an insurmountable challenge to signal processing. Therefore, it is necessary to address the shortcomings of electric field sensors in measuring ocean static electric fields, reduce the impact of ultra-low frequency noise interference on static electric field measurements, and realize long-distance ocean electric field measurements.

[0003] The "field grinding" principle, a modulation technique used in air-medium applications, enables the measurement of static electric fields in air. However, electric field measuring instruments based on the atmospheric "field grinding" principle must be avoided in environments with smog pollution, railways, highways, hillsides, etc. The probe must also be kept away from static electricity and foundations (typically requiring a distance greater than 1.5 meters), meaning it should be kept away from objects close to the ground. This also applies to marine environments, to avoid the influence of conductive objects, the ground, and the ocean on the electric field measurement. Seawater's excellent conductivity, unlike air's insulation, means the "field grinding" principle, invented in the 1940s, has not yet been used to measure static electric fields in seawater. While the rotating natural potential method probe can also modulate the measurement signal, the principle of electric field measurement still relies on the indirect method of voltage division between two probes and the measured electric field. The measurement is closely related to the various media and their movement between the two probes and the measured electric field, resulting in low resolution and a long stabilization time.

[0004] Therefore, a new technical solution is needed to improve the above-mentioned technical problems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a non-contact measurement device for mechanically modulated marine static electric fields.

[0006] A non-contact measurement device for mechanically modulated marine static electric field according to the present invention includes: a static electric field, a grounding terminal, a turntable, a rotating shaft, a shielding shell, measuring electrodes, a reference electrode, a differential amplifier, a lock-in amplifier, a reference signal, an A / D conversion circuit, a computer, a control circuit, and a motor;

[0007] The measuring electrode and the reference electrode are externally shielded, and the shielding shell is connected to the grounding terminal. The measuring electrode and the reference electrode are connected to a differential amplifier. The differential amplifier, the lock-in amplifier, the A / D conversion circuit, and the computer constitute a data acquisition / processor. The turntable, the shielding shell, the measuring electrode, and the reference electrode constitute a modulation sensor unit. The computer, the control circuit, and the motor constitute a turntable stabilization rotation speed controller. The turntable is driven by the control circuit to rotate at a constant speed. The control circuit encodes the rotation of the turntable to construct a reference signal with the same frequency as the frequency at which the turntable blocks the measuring electrode. The reference signal and the output signal of the differential amplifier are sent together to the lock-in amplifier for correlation narrowband filtering.

[0008] Preferably, the turntable is made of metal plates with equally spaced circular arcs.

[0009] Preferably, a measuring electrode and a reference electrode are fixed inside the shielding shell, the measuring electrode is disposed at the opening of the shielding shell, and the reference electrode is disposed in the closed area of ​​the shielding shell. The measuring electrode receives the modulated electric field and common-mode interference, and the reference electrode receives the common-mode interference signal.

[0010] Preferably, the turntable is installed in front of the measuring electrode, and the turntable is driven by a motor. The static electric field is blocked by the turntable at intervals, resulting in modulation.

[0011] Preferably, the measuring electrode and the reference electrode are planar electrodes made of a material with a high specific surface area, and have the same material, area and structure; the modulation signal obtained on the measuring electrode is the measured electric field signal blocked by the turntable, and the modulation signal frequency is the blocking frequency.

[0012] Preferably, the reference electrode obtains the common-mode interference signal in seawater; the signals from the measuring electrode and the reference electrode are phase-differentially amplified to remove the common-mode noise signal.

[0013] Preferably, the lock-in amplifier performs correlation narrowband filtering on the differential signal and the electrode rotation control signal to filter out various noise signals with frequencies different from the modulation signal; after denoising, the signal is converted by A / D and the digital signal is sent to the computer to calculate the measured electric field value.

[0014] Preferably, the computer controls the motor to maintain a constant speed of rotation via a control circuit.

[0015] Preferably, the motor shaft and the turntable shaft are connected by a shaft connector, the motor and brushes are fixed on a grounded base, the turntable is fixed on the base by bearings, the control circuit drives the motor to rotate, and the turntable rotates through the shaft connector.

[0016] Preferably, the measuring electrode and the reference electrode are made of Ag / AgCl electrode material, and the measuring electrode and the reference electrode are the same size.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The device of the present invention uses mechanical modulation to realize long-distance non-contact measurement of the static electric field of the ocean. Mechanical modulation transforms the static electric field into a fixed frequency AC electric field, reducing the influence of electric field drift and low-frequency noise, and improving the measurement resolution.

[0019] 2. This invention can measure the electric field of liquid media such as seawater, lake water, river water and groundwater, and can measure the electric field generated by minerals in water, underwater ships, ocean currents and aquatic plants and animals;

[0020] 3. The device of the present invention and the electric field to be measured are non-contact measurements. It can measure not only static electric fields, but also quasi-static electric fields with lower frequencies. As long as the rotation frequency of the turntable is much higher than the frequency of the electric field to be measured, the device can also perform the function of measuring electric fields. Attached Figure Description

[0021] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0022] Figure 1 This is a general block diagram illustrating a mechanically modulated marine static electric field long-distance non-contact measurement device involved in the present invention;

[0023] Figure 2 This is a schematic diagram illustrating the principle of a typical brush connection between the turntable shaft and the ground, provided in an embodiment of the present invention.

[0024] Figure 3 This is a schematic diagram showing the connection between the motor and the turntable via a shaft connector, provided in an embodiment of the present invention.

[0025] Figure 4 A circuit schematic diagram of differential amplification of the modulated electric field signal sensed by the measuring electrode and the common-mode signal sensed by the reference electrode, provided in an embodiment of the present invention;

[0026] Figure 5 A block diagram illustrating the principle of a lock-in amplifier for implementing narrowband filtering, provided in an embodiment of the present invention;

[0027] Figure 6A schematic block diagram of the motor control circuit and reference signal generation circuit provided in an embodiment of the present invention;

[0028] Figure 7 A block diagram of a device for modulating an ocean electric field using two rotating disks with opposite directions, provided in an embodiment of the present invention;

[0029] Figure 8 A block diagram of a device for modulating an ocean electric field using a camera shutter, provided in an embodiment of the present invention.

[0030] in:

[0031] Static electric field 101 Differential amplifier 108

[0032] Ground terminal 102 Lock-in amplifier 109

[0033] Turntable 103 Reference Signal 110

[0034] Shaft 104 A / D conversion circuit 111

[0035] Shielding enclosure 105 Computer 112

[0036] Measuring electrode 106 Control circuit 113

[0037] Reference electrode 107, motor 114 Detailed Implementation

[0038] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0039] Example 1:

[0040] This invention provides a non-contact measurement device for mechanically modulated marine static electric fields, comprising: a static electric field 101, a grounding terminal 102, a turntable 103, a rotating shaft 104, a shielding shell 105, measuring electrodes 106, a reference electrode 107, a differential amplifier 108, a lock-in amplifier 109, a reference signal 110, an A / D conversion circuit 111, a computer 112, a control circuit 113, and a motor 114; the measuring electrodes 106 and 107 are externally shielded by the shielding shell 105, which is connected to the grounding terminal 102; the measuring electrodes 106 and 107 are connected to the differential amplifier 108, which is a lock-in amplifier... The device 109, A / D conversion circuit 111, and computer 112 constitute a data acquisition / processor; the turntable 103, shielding shell 105, measuring electrode 106, and reference electrode 107 constitute a modulation sensor unit; the computer 112, control circuit 113, and motor 114 constitute a stable rotation speed controller for the turntable 103; the turntable 103 is driven by the control circuit 113 to rotate the motor 114 at a uniform speed; the control circuit 113 encodes the rotation of the turntable 103 to construct a reference signal 110 with the same blocking frequency as the turntable 103, and the reference signal 110 and the output signal of the differential amplifier 108 are sent together to the lock-in amplifier 109 for correlation narrowband filtering.

[0041] The turntable 103 is composed of metal plates with equal-angled circular arcs; the measuring electrode 106 and the reference electrode 107 are fixed inside the shielding shell 105. The measuring electrode 106 is set at the opening of the shielding shell 105, and the reference electrode 107 is set in the closed area of ​​the shielding shell 105. The measuring electrode 106 receives the modulated electric field and common-mode interference, and the reference electrode 107 receives the common-mode interference signal.

[0042] The turntable 103 is installed in front of the measuring electrode 106. The turntable 103 is driven by the motor 114. The static electric field 101 is blocked by the turntable 103 at intervals, generating modulation. The measuring electrode 106 and the reference electrode 107 are planar electrodes made of materials with high specific surface area, and have the same material, area and structure. The modulation signal obtained on the measuring electrode 106 is the measured electric field signal blocked by the turntable 103, and the modulation signal frequency is the blocking frequency.

[0043] The reference electrode 107 obtains the common-mode interference signal in seawater; the signals of the measuring electrode 106 and the reference electrode 107 are phase-differentially filtered by the differential amplifier 108 to remove the common-mode noise signal; the lock-in amplifier 109 performs correlation narrowband filtering on the differential signal and the electrode rotation control signal to filter out various noise signals with frequencies different from the modulation signal; the denoised signal is then converted by an A / D converter and sent to the computer 112 to calculate the measured electric field value.

[0044] The computer 112 controls the motor 114 to rotate at a constant speed via the control circuit 113. The shaft of the motor 114 is connected to the shaft of the turntable 103 via a shaft connector. The motor 114 and brushes are fixed to a grounded base. The turntable 103 is fixed to the base via bearings. The control circuit 113 drives the motor 114 to rotate, which in turn drives the turntable 103 to rotate via the shaft connector. The measuring electrode 106 and the reference electrode 107 are made of Ag / AgCl electrode material and have the same size.

[0045] Example 2:

[0046] The present invention addresses the shortcomings of the prior art by providing a long-distance measurement device for mechanically modulated marine static electric fields 101. The technical concept involves installing a grounded turntable 103 in front of a measuring electrode 106. A motor 114 drives the turntable 103 to rotate, causing the static electric field 101 in the seawater to be intermittently blocked by the turntable 103, thus generating modulation. The measuring electrode 106 and the reference electrode 107 are planar electrodes constructed of a high specific surface area material, possessing identical material, area, and structure. The measured electric field signal, with its carrier wave blocked by the turntable 103, is obtained on the measuring electrode 106; the carrier frequency is the blocking frequency. The reference electrode 107 can obtain... Common-mode interference signals are detected in the seawater, but the measured electric field signal cannot be received. The signals from the measuring electrode 106 and the reference electrode 107 are phase-differentially amplified by the differential amplifier 108 to remove common-mode noise. The lock-in amplifier 109 performs correlation narrowband filtering on the differential signal and the electrode rotation control signal to filter out various noise signals with frequencies different from the modulation signal. After denoising, the signal is sampled by the A / D converter 111 and sent to the computer 112, where the measured electric field value is calculated. The computer 112 uses the control circuit 113 to keep the motor 114 rotating at a constant speed. The overall principle and structure of the device are as follows: Figure 1 As shown, this measurement method directly measures the electric field in seawater by modulating the electric field being measured, rather than indirectly measuring the voltage drop across the seawater resistance using a measuring probe. This avoids the shortcomings of the traditional natural potential method. Thus, regardless of whether the electric field is static or a low-frequency signal, the measurement system can convert it into a fixed-frequency AC signal through mechanical modulation. As long as the rotation frequency of the turntable 103 is higher than the frequency of the measured signal, the measuring device can measure the weak electric field of the ocean at high resolution, exhibiting high stability. This device can measure the electric field of various liquid media, including seawater, lake water, river water, and groundwater. It can also measure the electric fields generated by minerals in water, underwater vessels, ocean currents, and aquatic plants and animals.

[0047] A remote measuring device for mechanically modulated marine static electric fields 101, comprising a turntable 103 connected to ground 102, a rotating shaft 104 connected to ground 102, a motor 114, a control circuit 113, measuring electrodes 106, a reference electrode 107, and a shielding shell 105 connected to ground 102. The device is characterized by further including a data acquisition / processor consisting of a differential amplifier circuit 108, a locking amplifier circuit 109, an A / D conversion circuit 111, and a computer 112. The rotating turntable 103 is composed of metal plates with equally spaced circular arcs. The disk 103, shielding shell 105, measuring electrode 106, and reference electrode 107 constitute an electrostatic field modulation sensor unit. The rotating speed controller of the disk 103 is composed of computer 112, control circuit 113, and motor 114. The rotating disk 103 is driven by the control circuit 113 to rotate the motor 114 at a uniform speed. The control circuit 113 encodes the rotation of the disk 103 to construct a reference signal 110 with the same blocking frequency as the disk 103. This reference signal 110 is sent together with the output of differential amplifier 108 to lock-in amplifier 109 for correlation narrowband filtering.

[0048] A measuring electrode 106 and a reference electrode 107 are fixed in two areas inside the shielding shell 105 that do not contact the shielding shell 105, respectively. A measuring electrode 106 is arranged at the opening of the shielding shell 105, and a reference electrode 107 is arranged in the closed area of ​​the shielding shell 105. Seawater can flow inside the closed shell, but the measured electric field signal cannot reach the closed shell. The measuring electrode 106 receives both the modulated electric field and the common-mode interference signal, while the reference electrode 107 can only receive the common-mode interference signal. The differential energy between the two can suppress common-mode interference and drift.

[0049] The connection between the turntable's shaft and ground is achieved through a typical brush, such as... Figure 2 As shown. The good conductivity of the brushes ensures low-resistance connection between the shaft and ground during rotation.

[0050] The motor shaft and the turntable shaft are connected by a shaft connector, such as... Figure 3 As shown. The motor and brushes are fixed to a grounded base, and the turntable is fixed to the base connected to ground via bearings. The control circuit drives the motor to rotate, which in turn drives the turntable to rotate via a shaft connector. The brushes connect both the shaft and the turntable to ground.

[0051] Both the measuring and reference electrodes are made of Ag / AgCl electrode material and have identical dimensions. These electrodes possess a high specific surface area, good reversibility, are not easily polarized, have relatively stable electrode potentials close to zero, exhibit good potential reproducibility, a small temperature coefficient, and are durable in seawater. The two electrodes are... Figure 1 Within the shielded structure, the same common-mode signal can be obtained. The reference electrode is shielded and cannot sense the modulation electric field; only the measuring electrode can sense the modulation electric field.

[0052] The modulated electric field signals sensed by the measuring and reference electrodes are processed by a differential circuit to remove common-mode interference, such as... Figure 4 As shown, the measuring electrode and the reference electrode are equivalent to a current source connected in parallel with a capacitor and a resistor. Their outputs must be a charge amplifier to recover the electric field signal without distortion. Since the output of charge amplifier 1 includes the electric field signal and common-mode interference, while the output of charge amplifier 2 only includes common-mode interference, passing the two outputs through a differential amplifier can significantly suppress common-mode interference and improve the signal-to-noise ratio of the output electric field signal.

[0053] A static electric field under test, modulated at a fixed frequency by a mechanical turntable, can have its various interference signals in the environment significantly reduced by narrow-band filtering through a lock-in amplifier. The principle of the lock-in amplifier is as follows: Figure 5 As shown. The input signal is the output signal of the differential amplifier, and the reference signal comes from... Figure 1 The control circuit uses a reference signal that has been shaped and phase-shifted, then subjected to phase-sensitive detection (PSD) and low-pass filtering with the amplified and filtered input signal to obtain its difference frequency signal. This ensures that only the input signal with the exact same frequency as the reference signal can be output, while interference at other frequencies is filtered out. The lock-in amplifier achieves very narrow bandpass filtering, with a bandwidth below 1 MHz.

[0054] The motor control circuit must not only ensure stable motor operation but also generate a reference signal for the latch-up amplifier, such as... Figure 6 As shown. The computer inputs control signals, which, through speed and current sensors, adjust the motor speed and drive current via speed and current feedback to ensure uniform motor rotation and stable drive current. PWM regulation can change the torque of the motor driving the turntable. The drive circuit provides sufficient drive power to the motor, typically using a typical H-type motor drive circuit. The motor rotation drives the angle encoder, a special frequency signal generator that provides a reference signal for the lock-in amplifier. The output frequency of the angle encoder is almost identical to the turntable's blocking frequency; that is, the angle encoder's output signal can replace the turntable's blocking signal.

[0055] Example 3

[0056] Those skilled in the art can understand this embodiment as a more specific description of Embodiment 2.

[0057] The turntable in Example 2 is constructed by combining two turntables rotating in opposite directions, such as... Figure 7 As shown. The control circuit drives electrode 1 and motor 2 respectively. Turntable 1 and turntable 2 rotate counterclockwise and clockwise respectively. The frequency of the turntable blocking can be increased compared to the frequency of a single turntable, and the frequency of the modulated electric field is also increased.

[0058] Example 4

[0059] Those skilled in the art can understand this embodiment as a more specific description of Embodiment 2.

[0060] The turntable in Example 2 is constructed using a camera shutter capable of continuously opening and closing, such as... Figure 8 As shown, the control circuit controls the shutter drive circuit, causing the shutter to periodically block the measured electric field, generating a modulated electric field. The shutter switching frequency can be very high; therefore, the modulation electric field frequency can be further increased, thus expanding the measurement bandwidth of the electric field.

[0061] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0062] 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 non-contact measurement device for mechanically modulated marine static electric fields, characterized in that, include: The components include a static electric field (101), a grounding terminal (102), a turntable (103), a rotating shaft (104), a shielding shell (105), a measuring electrode (106), a reference electrode (107), a differential amplifier (108), a lock-in amplifier (109), a reference signal (110), an A / D conversion circuit (111), a computer (112), a control circuit (113), and a motor (114). The measuring electrode (106) and the reference electrode (107) are provided with a shielding shell (105), which is connected to the grounding terminal (102). The measuring electrode (106) and the reference electrode (107) are connected to a differential amplifier (108), which, along with a lock-in amplifier (109), an A / D conversion circuit (111), and a computer (112), constitutes a data acquisition / processor. The turntable (103), the shielding shell (105), the measuring electrode (106), and the reference electrode (107) constitute a modulation transmission. The sensor unit; the computer (112), control circuit (113) and motor (114) constitute a turntable (103) stable rotation speed controller; the turntable (103) is driven by the control circuit (113) to rotate the motor (114) at a constant speed; the control circuit (113) encodes the rotation of the turntable (103) and constructs a reference signal (110) with the same frequency as the frequency of the measurement electrode blocked by the turntable (103); the reference signal (110) and the output signal of the differential amplifier (108) are sent together to the lock-in amplifier (109) for correlation narrowband filtering; The measuring electrode (106) and the reference electrode (107) are fixed inside the shielding shell (105). The measuring electrode (106) is set at the opening of the shielding shell (105), and the reference electrode (107) is set in the closed area of ​​the shielding shell (105). The measuring electrode (106) receives the modulated electric field and common-mode interference, and the reference electrode (107) receives the common-mode interference signal.

2. The non-contact measurement device for mechanically modulated marine static electric fields according to claim 1, characterized in that, The turntable (103) is made of metal plates with equally spaced arcs.

3. The non-contact measurement device for mechanically modulated marine static electric fields according to claim 1, characterized in that, The turntable (103) is installed in front of the measuring electrode (106). The turntable (103) is driven by the motor (114). The static electric field (101) is blocked by the interval of the turntable (103) and modulated.

4. The non-contact measurement device for mechanically modulated marine static electric fields according to claim 1, characterized in that, The measuring electrode (106) and the reference electrode (107) are planar electrodes made of a material with a high specific surface area, and have the same material, area and structure. The modulation signal obtained on the measuring electrode (106) is the electric field signal to be measured blocked by the turntable (103), and the modulation signal frequency is the blocking frequency.

5. The non-contact measurement device for mechanically modulated marine static electric fields according to claim 1, characterized in that, The reference electrode (107) obtains the common-mode interference signal in seawater; the signals of the measuring electrode (106) and the reference electrode (107) are phase-differentially compared by the differential amplifier (108) to remove the common-mode noise signal.

6. The non-contact measurement device for mechanically modulated marine static electric fields according to claim 1, characterized in that, The lock-in amplifier (109) performs correlation narrowband filtering on the differential signal and the electrode rotation control signal to filter out various noise signals with frequencies different from the modulation signal; after noise reduction, the signal is converted by A / D and the digital signal is sent to the computer (112) to calculate the measured electric field value.

7. The non-contact measurement device for mechanically modulated marine static electric fields according to claim 1, characterized in that, The computer (112) uses a control circuit (113) to keep the motor (114) rotating at a constant speed.

8. The non-contact measurement device for mechanically modulated marine static electric fields according to claim 1, characterized in that, The shaft of the motor (114) is connected to the shaft of the turntable (103) by a shaft connector. The motor (114) and the brush are fixed on the grounded base. The turntable (103) is fixed on the base by a bearing. The control circuit (113) drives the motor (114) to rotate and drives the turntable (103) to rotate through the shaft connector.

9. The non-contact measurement device for mechanically modulated marine static electric fields according to claim 1, characterized in that, The measuring electrode (106) and the reference electrode (107) are made of Ag / AgCl electrode material, and the measuring electrode (106) and the reference electrode (107) are the same size.

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