Capacitive infrasound sensor and self-calibration device and method thereof

Abstract

The invention provides a capacitive infrasound sensor and a self-calibration device and method thereof, and relates to the technical field of infrasound sensors. The device comprises a vibrating diaphragm assembly which is arranged in a rear cavity of the capacitive infrasound sensor and is in sealing connection with the rear cavity, wherein the vibrating diaphragm assembly comprises a polymer vibrating diaphragm and a supporting ring; the coil assembly comprises a coil framework with a hollow structure and a coil wound at one end of the coil framework; one end of the coil skeleton away from the coil is fixedly connected with the polymer diaphragm; the magnetic assembly is used for forming a gap magnetic field; configuring the coil to be completely located in the gap magnetic field; the limiting mechanism is used for selectively locking the coil assembly; and the front-end circuit module comprises a central control module, a calibration current generation module and an acoustic-electric conversion module. Based on the electromagnetic moving coil principle, the self-calibration capacity can be remarkably improved under the condition that the advantages of high sensitivity and good vibration resistance of a capacitive infrasound sensor are reserved, and the requirement for long-term use in the field is met.

Description

Technical Field

[0001] This invention relates to the field of infrasound sensor technology, and in particular to a capacitive infrasound sensor and its self-calibration device and method. Background Technology

[0002] Infrasound sensors are microphones that can receive infrasound signals from the air. Their lower frequency limit can reach 0.003Hz, and they are widely used in fields such as natural disaster monitoring and long-distance underwater acoustic communication.

[0003] Existing infrasound sensor products can be divided into two main categories according to their working principles: capacitive and dynamic. For capacitive infrasound sensors, the acoustic sensing structure is a variable capacitor composed of a circular fixed metal thin film (diaphragm) and a back electrode plate. The diaphragm will undergo forced vibration under the action of infrasound waves, and the capacitance value will change accordingly. Then, a voltage signal is generated and output through an impedance transformation circuit.

[0004] As the front-end sensing unit of the system, the accuracy of key parameters such as sensitivity of the infrasound sensor directly determines the reliability of infrasound sound pressure testing. Since sensors are inevitably affected by environmental factors such as seasonal temperature and air pressure changes, diaphragm and circuit aging can occur, leading to changes in sensitivity and zero-point drift, thus affecting the operational stability of the infrasound sensor. Therefore, to meet usage requirements, the sensitivity of the infrasound sensor needs to be calibrated periodically.

[0005] Currently, the precise calibration of infrasound sensors must be completed in a laboratory using high-precision laser measurement methods. Laboratory calibration equipment is bulky and heavy, making it impossible to deploy and operate outside of a laboratory environment. However, in the actual deployment of infrasound monitoring systems, monitoring points are typically located far from densely populated areas, in open terrain, strategic locations, or border areas, making it extremely inconvenient to frequently disassemble and transport the sensors back to the laboratory for calibration.

[0006] In related technologies, patent application CN211291733U proposes a portable calibration device for infrasound sensors, but it still requires on-site operation by personnel for calibration and cannot achieve remote self-calibration function, making it unsuitable for infrasound sensor calibration work deployed in remote areas.

[0007] Patent application CN211291720U proposes an infrasound sensor with self-calibration function, which uses electromagnetic excitation to achieve the self-calibration function of the infrasound sensor. Although this solution can solve the remote self-calibration requirement of infrasound sensors, it has the following drawbacks in use: the electrostatic excitation method vibrates the diaphragm through electrostatic force, which requires the diaphragm to be under a high electric field strength. Therefore, the electrostatic exciter needs to provide a high bias voltage (usually greater than 100V), which makes the power supply system of the sensor more complex and consumes more power. At the same time, the higher operating voltage will reduce the intrinsic safety of the sensor. All of these seriously affect the sensor's deployment, maintenance process and long-term working stability. Summary of the Invention

[0008] This invention provides a capacitive infrasound sensor and its self-calibration device and method, solving the problem of how to achieve low power consumption and convenient self-calibration of capacitive infrasound sensors.

[0009] To achieve the above objectives, this application adopts the following technical solution: In a first aspect, a self-calibration device for a capacitive infrasound sensor is provided, comprising: A diaphragm assembly is disposed in the rear cavity of the capacitive infrasound sensor and is sealed to the rear cavity; the diaphragm assembly includes a polymer diaphragm and a support ring for supporting and tautly fixing it. A coil assembly includes a hollow coil frame and a coil wound on one end of the coil frame; the end of the coil frame away from the coil is fixedly connected to a polymer diaphragm. A magnetic component is used to form a gap magnetic field; the coil is configured to be completely within the gap magnetic field. A limiting mechanism is provided for selectively locking the coil assembly to restrict its axial movement. The front-end circuit module includes a central control module, a calibration current generation module, and a sound-to-electricity conversion module; During use, the system acquires calibration commands and calibration signals, controls the limit device to disengage from the coil assembly, generates a calibration current, excites axial vibration in the coil assembly, and simultaneously drives the polymer diaphragm to vibrate. The gas in the rear cavity fluctuates periodically with the vibration of the polymer diaphragm, which in turn drives the diaphragm of the capacitive infrasound sensor to vibrate. The signal is then output as a voltage signal through the acoustic-to-electric conversion module.

[0010] In a second aspect, a self-calibrating capacitive infrasound sensor is provided, characterized in that it includes a self-calibrating device for a capacitive infrasound sensor as described in the first aspect.

[0011] Thirdly, a self-calibration method for a capacitive infrasound sensor is provided, which performs self-calibration based on the capacitive infrasound sensor self-calibration device as described in the first aspect, including: S1 receives calibration commands and calibration signals sent by the host computer; S2, the limiting mechanism is disengaged from the coil frame; S3 generates a calibration current based on the calibration signal; S4, acquire the output voltage signal of the self-calibration device of the capacitive infrasound sensor; S5. Calculate the sensitivity ratio based on the amplitude of the output voltage signal and the amplitude of the calibration signal, and compare it with the pre-stored reference value to determine the sensor status. S6 is equipped with a limit mechanism to reset and lock the coil frame.

[0012] The capacitive infrasound sensor and its self-calibration device and method of the present invention have the following beneficial effects: This application presents a self-calibration device and method for a capacitive infrasound sensor based on electromagnetic principles. The structure of the capacitive infrasound sensor is optimized by adding a polymer diaphragm to the rear cavity. The vibration of the polymer diaphragm is controlled by an electromagnetic coil, generating infrasound waves with controllable amplitude and frequency in the sensor's rear cavity, thus achieving sensitivity calibration of the infrasound sensor. This addresses the problems of system complexity, high power consumption, poor intrinsic safety, and low stability encountered when using electromagnetic excitation methods for self-calibration in unattended field environments. While retaining the advantages of high sensitivity and good vibration resistance of capacitive infrasound sensors, this method significantly improves self-calibration capabilities, meeting the needs of long-term field use. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of a self-calibration device for a capacitive infrasound sensor provided in an embodiment of this application; Figure 2 A schematic diagram of a conventional capacitive infrasound sensor provided in an embodiment of this application; Figure 3 This is a schematic flowchart illustrating the self-calibration of a capacitive infrasound sensor provided in an embodiment of this application. Detailed Implementation

[0014] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the technical solutions in the embodiments of this application are clearly described. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art are within the scope of protection of this application.

[0015] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0016] The steps described in the specification and the flowcharts in the accompanying drawings of this invention are not necessarily strictly executed according to the step numbers; the execution order of the method steps can be changed. Furthermore, certain steps can be omitted, multiple steps can be combined into one step, and / or one step can be broken down into multiple steps.

[0017] Traditional capacitive infrasound sensors, such as Figure 2 As shown, it mainly consists of a front cavity 1, a support ring 2, a diaphragm 3, a back electrode plate 4, a pressure equalization hole 5, and a rear cavity 6. The diaphragm 3 and the back electrode plate 4 form the electrode capacitor. The space between the diaphragm 3 and the back electrode plate 4 is the working gap of the electrode capacitor. The rear cavity 6 forms an approximately closed volume connected to this gap, which is used to provide a stable pressure reference volume, adjust the air damping characteristics, and stabilize the working environment of the electrode capacitor.

[0018] When a sound wave acts on the diaphragm 3, the diaphragm 3 will undergo forced vibration, causing a change in capacitance. The sound wave is characterized by detecting the change in capacitance, thus achieving sound wave-to-electrical signal conversion. To ensure the flatness of the diaphragm 3, it needs to be taut on the support ring 2 with a certain tension. The lower limit of the frequency response of the infrasound sensor can reach 0.003Hz. To achieve such a low frequency detection limit, the rear cavity 6 of the infrasound sensor is connected to the outside through a pressure equalization hole 5. Since the pressure equalization hole is very small, the rear cavity 6 can be considered approximately sealed.

[0019] Considering that the sensitive structure of a capacitive microphone is a taut diaphragm, the commonly used calibration method is electrostatic excitation, as described in patent application CN 211291720 U (an infrasound sensor with self-calibration function). In this method, the electrostatic exciter needs to be placed directly above the diaphragm (3), with a fixed distance maintained between the exciter and the diaphragm 3 via an insulating support. Electrostatic excitation causes the diaphragm to vibrate through electrostatic force, requiring the diaphragm to be under a high electric field strength. Therefore, it needs to operate at a high bias voltage (usually greater than 100V). Typically, the electrostatic exciter needs to be paired with a signal generator, an AC boost unit, and a DC boost unit. First, the signal generator generates a sinusoidal signal with frequency f. Then, the AC boost conversion unit amplifies the calibration signal voltage to U, and a DC voltage-sound-pressure conversion unit applies the bias to form an AC signal with a bias voltage of over 100V at the electrostatic exciter.

[0020] At this point, the diaphragm's vibration frequency is the same as the calibration sinusoidal signal f, and the vibration amplitude A is proportional to the amplitude U after AC voltage boosting and the bias voltage. Correspondingly, the infrasound sensor will also output an electrical signal with a frequency f and an effective value proportional to A. By comparing the output signal with the input signal, the sensitivity calibration function of the infrasound sensor is achieved.

[0021] The aforementioned electrostatic excitation method for sensitivity self-calibration suffers from high operating voltage, which reduces the inherent safety of the sensor and severely impacts its deployment, maintenance, and long-term operational stability. Therefore, this specification provides a self-calibration device and method for a capacitive infrasound sensor. This method, based on an electromagnetic moving coil, addresses the problems of existing infrasound sensor self-calibration systems being complex, power-consuming, and unsuitable for widespread use, thus meeting the requirements for long-term field application of infrasound sensors. The following detailed description, in conjunction with the accompanying drawings and preferred embodiments, provides further insights.

[0022] Please see Figure 1 This application provides a self-calibration device for a capacitive infrasound sensor, such as... Figure 1 As shown, it includes: A diaphragm assembly is disposed in the rear cavity of the capacitive infrasound sensor and is sealed to the rear cavity; the diaphragm assembly includes a polymer diaphragm 8 and a support ring for supporting and fixing it tightly. The coil assembly includes a hollow coil frame 10 and a coil wound on one end of the coil frame 10; the end of the coil frame 10 away from the coil is fixedly connected to a polymer diaphragm 8. A magnetic component is used to form a gap magnetic field; the coil is configured to be completely within the gap magnetic field. A limiting mechanism is provided for selectively locking the coil assembly to restrict its axial movement. The front-end circuit module 9 includes a central control module, a calibration current generation module, and a sound-to-electricity conversion module; In use, the system acquires calibration instructions and calibration signals, controls the limit device to disengage from the coil assembly, generates a calibration current, excites axial vibration of the coil assembly, and simultaneously drives the polymer diaphragm 8 to vibrate. The gas in the rear cavity fluctuates periodically with the vibration of the polymer diaphragm 8, which drives the diaphragm 3 of the capacitive infrasound sensor to vibrate, and outputs a voltage signal through the sound-to-electric conversion module.

[0023] Furthermore, the coil is a copper wire coil 12, which is wound on the coil frame 10 using an inner and outer winding structure.

[0024] Furthermore, the magnetic component includes a permanent magnet 11, which has an annular gap for accommodating a coil.

[0025] Furthermore, the limiting mechanism includes a limiting clamp 14, which mechanically contacts the coil frame 10 to achieve locking in the non-calibrated state.

[0026] Furthermore, the front circuit module 9 is configured as an annular plate surrounding the coil frame 10; the front circuit module 9 also includes a connector 13 for transmitting host computer commands, the connector 13 being embedded in the rear cavity wall.

[0027] For example, referring to the figure, in a specific implementation, an additional lower support ring 7 and a polymer diaphragm 8 are added to the bottom of the rear cavity 6 of the infrasound sensor. The polymer diaphragm 8 is stretched on the lower support ring 7 with a certain tension. The coil frame 10 is bonded to the polymer diaphragm 8. The copper wire coil 12 is wound on the coil frame 10 using an inner and outer winding structure. The coil frame 10 is hollow. After the copper wire coil 12 is wound, it can be inserted into the gap of the permanent magnet 11, so that the copper wire coil 12 is completely in the magnetic field of the gap of the permanent magnet 11. The pre-amplifier circuit 9 is circular and realizes the functions of infrasound sound-to-electric conversion, calibration control, etc. It is connected to the back electrode plate 4 of the diaphragm 3, the copper wire coil 12, the limiting clamp 14, and the connector 13. In the idle state, the limiting clamp 14 contacts the coil frame 10 to play a fixing role, which can effectively limit the axial displacement of the coil frame 10.

[0028] The working principle of this capacitive infrasound sensor self-calibration device is as follows: The host computer issues a calibration command and simultaneously generates a calibration signal with a frequency of f0, which is input to the preamplifier module 9 through the connector 13. The preamplifier module 9 first controls the limit clamp 14 to disengage from the coil frame 10, allowing the coil frame 10 to move axially. At the same time, it amplifies the calibration signal, generating an alternating current with the same frequency f0 as the calibration signal in the copper wire coil 12. Since the copper wire coil 12 is in the magnetic field of the gap between the permanent magnets 11, the copper wire coil 12 will generate an axial driving force, pushing the coil frame 10 to reciprocate axially at f0, while simultaneously driving the polymer diaphragm 8 to vibrate at a frequency of f0. Since the rear cavity 6 is approximately sealed, when the polymer diaphragm 8 vibrates at a frequency of f0, the gas density in the rear cavity will periodically fluctuate, driving the diaphragm 3 to vibrate at a frequency of f0. At this time, the distance between the diaphragm 3 and the back electrode plate 4 will also change at a frequency of f0. After passing through the acoustic-to-electric conversion module of the pre-amplifier circuit module 9, a voltage signal with a frequency of f0 is generated. The amplitude A of the output signal is proportional to the sensitivity S and the amplitude A0 of the calibration signal. By comparing the ratio of the A and A0 parameters in the factory settings, it is determined whether the current sensitivity of the sensor is within a reasonable range and whether the sensor is working properly. After completing the self-calibration, the pre-amplifier circuit module 9 controls the limit clamp 14 to contact the coil frame 10 to reduce vibration and noise interference.

[0029] Corresponding to the above-described embodiment of the self-calibration device for a capacitive infrasound sensor, this application provides a self-calibrating capacitive infrasound sensor, including the above-described self-calibration device for a capacitive infrasound sensor.

[0030] The self-calibrating capacitive infrasound sensor described above implements each process of the above-described self-calibration device embodiment for the capacitive infrasound sensor and achieves the same technical effect. To avoid repetition, it will not be described again here.

[0031] Please see Figure 3 This application provides a self-calibration method for a capacitive infrasound sensor, which performs self-calibration based on the aforementioned capacitive infrasound sensor self-calibration device, including: Step S1: Receive calibration instructions and calibration signals sent by the host computer; The calibration signal is a sinusoidal electrical signal with a frequency of f0. Step S2: Configure the limiting mechanism to disengage from the coil frame; Step S3: Generate a calibration current based on the calibration signal; Step S4: Obtain the output voltage signal of the self-calibration device for the capacitive infrasound sensor; Step S5: Calculate the sensitivity ratio based on the amplitude of the output voltage signal and the amplitude of the calibration signal, and update the sensitivity data.

[0032] Step S6: Configure the limit mechanism to reset and lock the coil frame.

[0033] Further, the step of calculating the sensitivity ratio based on the amplitude of the output voltage signal and the amplitude of the calibration signal, and comparing it with a pre-stored reference value to determine the sensor state, includes: Calculate the sensitivity ratio S = A / A0. Where A is the amplitude of the output voltage signal, and A0 is the amplitude of the calibration signal. In some possible implementations, the following steps are performed before updating the sensitivity data: The sensor status is determined by comparing the calculated sensitivity ratio with the pre-stored reference value; if the sensor is determined to be working normally, the sensitivity data is updated.

[0034] Specifically: if the current sensitivity value of the sensor is within the error threshold range, If so, the sensor is considered normal; Among them, S ref δ represents the factory-set reference sensitivity, and δ represents the permissible error threshold.

[0035] If the sensor's sensitivity is within the error threshold range determined in this step, it means that the sensor meets the normal operating conditions, and the sensor's sensitivity data is updated for subsequent data processing; if the sensor's current sensitivity is not within the error threshold range, it is determined that the sensor is not working properly and needs to be replaced.

[0036] This application presents a self-calibration device and method for a capacitive infrasound sensor based on electromagnetic principles. The structure of the capacitive infrasound sensor is optimized by adding a polymer diaphragm to the rear cavity. The vibration of the polymer diaphragm is controlled by an electromagnetic coil, generating infrasound waves with controllable amplitude and frequency in the sensor's rear cavity, thus achieving sensitivity calibration of the infrasound sensor. This addresses the problems of system complexity, high power consumption, poor intrinsic safety, and low stability encountered when using electromagnetic excitation methods for self-calibration in unattended field environments. While retaining the advantages of high sensitivity and good vibration resistance of capacitive infrasound sensors, this method significantly improves self-calibration capabilities, meeting the needs of long-term field use.

[0037] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0038] It is understood that the embodiments of this application have been described above in conjunction with the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. As those skilled in the art will know, various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, those skilled in the art, under the guidance or instruction of this application, can modify these features and embodiments to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, this invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of this invention.

Claims

1. A self-calibration device for a capacitive infrasound sensor, characterized in that, include: A diaphragm assembly is disposed in the rear cavity of the capacitive infrasound sensor and is sealed to the rear cavity; the diaphragm assembly includes a polymer diaphragm and a support ring for supporting and tautly fixing it. A coil assembly includes a hollow coil frame and a coil wound on one end of the coil frame; the end of the coil frame away from the coil is fixedly connected to a polymer diaphragm. A magnetic component is used to form a gap magnetic field; the coil is configured to be completely within the gap magnetic field. A limiting mechanism is provided for selectively locking the coil assembly to restrict its axial movement. The front-end circuit module includes a central control module, a calibration current generation module, and a sound-to-electricity conversion module; During use, the system acquires calibration commands and calibration signals, controls the limit device to disengage from the coil assembly, generates a calibration current, excites axial vibration in the coil assembly, and simultaneously drives the polymer diaphragm to vibrate. The gas in the rear cavity fluctuates periodically with the vibration of the polymer diaphragm, which in turn drives the diaphragm of the capacitive infrasound sensor to vibrate. The signal is then output as a voltage signal through the acoustic-to-electric conversion module.

2. The self-calibration device for a capacitive infrasound sensor according to claim 1, characterized in that, The coil is a copper wire coil, which is wound around the coil frame using an inner and outer winding structure.

3. The self-calibration device for a capacitive infrasound sensor according to claim 1, characterized in that, The limiting mechanism includes a limiting clamp, which makes mechanical contact with the coil frame to achieve locking in the non-calibrated state.

4. The self-calibration device for a capacitive infrasound sensor according to claim 1, characterized in that, The front-end circuit module is configured as an annular plate surrounding the coil frame; the front-end circuit module also includes a connector for transmitting host computer commands, which is embedded in the rear cavity wall.

5. An electrically self-calibrating capacitive infrasound sensor, characterized in that, Includes the self-calibration device for a capacitive infrasound sensor as described in any one of claims 1-4.

6. A self-calibration method for a capacitive infrasound sensor, characterized in that, Self-calibration based on the capacitive infrasound sensor self-calibration device as described in any one of claims 1-4 includes: S1 receives calibration commands and calibration signals sent by the host computer; S2, the limiting mechanism is disengaged from the coil frame; S3 generates a calibration current based on the calibration signal; S4, acquire the output voltage signal of the self-calibration device of the capacitive infrasound sensor; S5, calculate the sensitivity ratio based on the amplitude of the output voltage signal and the amplitude of the calibration signal, and update the sensitivity data; S6 is equipped with a limit mechanism to reset and lock the coil frame.

7. The self-calibration method for a capacitive infrasound sensor according to claim 6, characterized in that, Sensitivity ratio S = A / A0 Where A is the amplitude of the output voltage signal and A0 is the amplitude of the calibration signal.

8. The self-calibration method for a capacitive infrasound sensor according to claim 7, characterized in that, Before updating the sensitivity data, perform the following steps: The sensor status is determined by comparing the calculated sensitivity ratio with the pre-stored reference value; if the sensor is determined to be working normally, the sensitivity data is updated.

9. The self-calibration method for a capacitive infrasound sensor according to claim 8, characterized in that, If the current sensitivity value of the sensor is within the error threshold range If so, the sensor is considered normal; Among them, S ref δ represents the factory-set reference sensitivity, and δ represents the permissible error threshold.

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