Flow velocity measurement device based on electric arc plasma

Abstract

This application relates to a flow field velocity measurement device based on electric arc plasma. The device includes a high-voltage power supply module, a load module, a negative feedback RC coupling module, a gas flow supply module, an optical observation module, a data acquisition and processing module, and a water cooling module. The high-voltage power supply module provides a controllable high-frequency AC voltage to the load module. The load module employs non-directly facing conical electrodes; when the gas between the electrodes is broken down, electric arc plasma is generated. The negative feedback RC coupling module is used to suppress the positive feedback process of gas discharge, achieving stable gas discharge. The optical observation module assists in electrode spacing calibration and plasma morphology observation. The gas flow supply module provides a continuously adjustable gas flow. The data acquisition and processing module collects and processes the voltage and current of the electric arc plasma at different wind speeds to obtain the flow field velocity. This device can achieve high-resolution time-correlated sequential flow field velocity measurement of hypersonic flow.

Description

Technical Field

[0001] This application relates to the field of artificial intelligence technology, and in particular to a flow field velocity measurement device based on electric arc plasma. Background Technology

[0002] The study of hypersonic flow field characteristics plays a crucial role in promoting the development of hypersonic flight technology. The turbulent phenomena occurring in hypersonic flows are extremely complex and have long been considered a major fundamental scientific problem. Establishing an accurate hypersonic turbulent boundary layer model and studying its characteristics is of great significance to the study of hypersonic flow field characteristics. As one of the fundamental physical quantities of turbulence, the accurate measurement of turbulent velocity is intuitively important. Furthermore, the harsh environment of high temperature and high pressure in hypersonic flow fields also poses a significant challenge to the accurate measurement of turbulent velocity. To overcome these difficulties, there is an urgent need to develop a wide-range, high-precision gas velocity measurement technology. The carrier of gas velocity measurement technology is called an anemometer or wind speed sensor. Currently, anemometers are widely used in aerospace and other fields.

[0003] Optical flow visualization technologies such as schlieren and particle imaging velocimeters have become routine methods for measuring boundary layers in flow fields in recent years. They are non-invasive and can obtain full-field velocity information at a specific moment. However, due to limitations in image recording technology, they struggle to meet the tracking requirements in hypersonic flow fields, failing to obtain continuous and accurate turbulent velocities. Laser Doppler velocimeters are also an optical measurement technology based on particle tracking, achieving single-point non-contact velocity measurement based on Doppler frequency shift, but they are expensive and highly susceptible to the influence of tracer particles. Hot-wire anemometers are currently widely used in hypersonic flow field measurements, but due to the fragility of the hot wire and difficulties in calibration, stable measurements cannot be achieved in the harsh environment of hypersonic flow fields.

[0004] Among numerous approaches, the arc plasma anemometer based on gas discharge is undoubtedly one of the most promising, possessing several inherent advantages: 1) extremely high dynamic frequency response; 2) no compensation required; 3) elimination of common-mode noise and high signal-to-noise ratio; 4) insensitivity to temperature and simple calibration; 5) compact discharge probe structure with a discharge gap reaching the micrometer scale, enabling stable measurement. Therefore, arc anemometers can achieve stable and high-precision velocity measurement in the high-temperature and high-pressure environment of hypersonic flow fields.

[0005] As early as 1934, Lindvall proposed that gas discharge could be used for wind speed measurement. Plasma anemometers based on gas discharge have undergone rapid development, with many researchers and teams abroad making outstanding contributions. In 1949, Mettler in the United States successfully developed a DC glow discharge anemometer, which was successfully applied to the measurement of supersonic flow fields at Mach 1.6 with good results. Furthermore, Mettler developed a quantitative theory of the response of glow discharge to airflow, finding that the effect of temperature was not significant. In 1954, Vrebalovich studied and compared the design of DC and AC glow discharge anemometers, finding that AC arc anemometers were superior in terms of flow velocity measurement range and stability, while also discovering significant room for improvement in velocity measurement range and frequency response. However, the underdeveloped gas discharge and electronic technologies at the time limited its development. In 2003, Matlis and Corke continued their research on wind speed measurement systems based on AC gas discharge, building upon Vrebalovich's ideas. They scaled the discharge gap to the micrometer scale, improving the stability of the measurement system. They also employed a high-frequency discharge power supply, reducing the discharge voltage and thus the electrical power required for stable gas discharge, significantly minimizing electrode damage. This demonstrated sensitivity to average and dynamic mass flux changes at Mach numbers up to 5.0 and frequencies up to 200 kHz, but velocity calibration was not performed. In 2015, the Marshall, Matlis, and Corke team made further progress in the field of AC plasma anemometers: 1) They used an RC network to generate a dielectric barrier discharge (DBD) effect to stabilize the plasma from arcing and minimize micro-discharge noise; 2) They implemented constant current feedback control, maintaining operation within the desired glow discharge state over an extended air velocity range; 3) They compared hot-wire anemometers with AC plasma anemometers, finding that AC plasma anemometers performed better in harsh environments such as high temperatures or under high Mach number airflows.

[0006] Research on plasma anemometer technology in China started relatively late, and to date, there are few reports on gas discharge-based plasma anemometers. In 2016, a research team led by Zhang Yunwei, Wang Weimin, and Jia Min studied the glow discharge characteristics of radio frequency plasma at low wind speeds. They built an experimental system for radio frequency plasma anemometer measurement and studied the air discharge characteristics of the system under different discharge gaps, wind speeds, and power outputs. The results showed that: a) the smaller the discharge gap, the higher the stability of the radio frequency glow discharge; b) the system load voltage has a good linear relationship with the wind speed. In 2018, Yuan Pei conducted research on plasma anemometer technology based on AC gas discharge from three aspects: numerical simulation, experiment, and electrical modeling. A numerical simulation platform and experimental measurement system for plasma were built; and a corresponding electrical model was established to comprehensively study the physical and electrical characteristics of arc plasma. In 2023, Chen Qinnan et al. designed an arc plasma anemometer for measuring the surface velocity of compressor blades and studied its performance, including velocity measurement range and operating temperature.

[0007] In summary, while significant progress has been made in experimental research on arc plasma anemometers, existing velocity measurement techniques, due to the unclear discharge mechanism, struggle to achieve high-resolution time-correlated sequential flow field velocity measurements in hypersonic flows. This study improves measurement accuracy through a segmented calibration method. Summary of the Invention

[0008] Therefore, it is necessary to provide a flow field velocity measurement device based on electric arc plasma to address the above-mentioned technical problems.

[0009] A flow field velocity measurement device based on electric arc plasma includes: a high-voltage power supply module, a load module, a negative feedback RC coupling module, an airflow supply module, an optical observation module, a data acquisition and data processing module, and a water cooling module.

[0010] The high-voltage power supply module is used to provide a controllable high-frequency AC voltage to the load module.

[0011] The load module is used to generate an electric arc plasma when the gas between the electrodes is broken down by a high-frequency AC voltage, employing non-aligned conical electrodes.

[0012] The negative feedback RC coupling module adopts a symmetrical structure and is connected between the high-voltage power supply module and the load module. It is used to suppress the positive feedback process of gas discharge and achieve stable gas discharge.

[0013] The optical observation module is used to assist in electrode spacing calibration and plasma morphology observation.

[0014] The airflow supply module is used to provide a continuously adjustable gas flow between the non-aligned conical electrodes.

[0015] The data acquisition and processing module is used to acquire the voltage and current of the arc plasma under different wind speeds, and to process the acquired voltage and current signals to obtain the flow field velocity.

[0016] The water-cooled module consists of a water pump and cooling water pipes in the transformer induction coil of the power module. The water pump draws water to cool the transformer.

[0017] In one embodiment, the high-voltage power supply module includes an AC power supply and a transformer. The voltage output by the AC power supply is controlled by the transformer.

[0018] In one embodiment, the load module includes two metal probes, the distance between which is adjusted manually.

[0019] The metal probe is a tungsten-copper alloy probe with a diameter of 2mm and a length of 40mm; the metal probe has a non-aligned conical structure.

[0020] The metal probe connected to the positive terminal of the transformer is used as the anode, and the metal probe connected to the negative terminal of the transformer is used as the common cathode.

[0021] In one embodiment, the negative feedback RC coupling module includes two resistors with the same resistance and two capacitors with the same capacitance.

[0022] One end of the first capacitor is connected to the positive output terminal of the high-voltage power supply module, the other end of the first capacitor is connected to one end of the first resistor, and the other end of the first resistor is connected to the anode of the load module.

[0023] One end of the second capacitor is connected to the negative output terminal of the high-voltage power supply module, the other end of the second capacitor is connected to one end of the second resistor, and the other end of the second resistor is connected to the common cathode of the load module.

[0024] In one embodiment, the air supply module includes a gas cylinder, a valve, and a Laval nozzle.

[0025] Valves are used to regulate wind speed.

[0026] In one embodiment, the optical observation module includes a microscope and a display.

[0027] In one embodiment, the data acquisition and data processing module includes a computer system and an oscilloscope.

[0028] The oscilloscope is used to acquire the voltage and current signals of the electric arc through a differential high-voltage probe and transmit them to the computer system via a USB interface.

[0029] The computer system is used to receive and store the voltage and current signals of the electric arc, and to obtain the average current of the stable section by averaging the current signal of the stable section. Based on the average current of the stable section and the calibration relationship, the wind speed of the flow field is determined.

[0030] In one embodiment, the calibration relationship is as follows: ;

[0031] Where V is the velocity of the flow field and I is the average current in the steady-state section.

[0032] In one embodiment, the overall layout of the flow field velocity measuring device is as follows:

[0033] The high-voltage power supply module and the negative feedback RC coupling module are integrated onto the PCB board, the load module and data acquisition line are connected to the PCB board, and then all the PCB board, load module and data acquisition line are encapsulated inside an insulating shell.

[0034] One of the above technical solutions has the following advantages and beneficial effects:

[0035] The aforementioned flow field velocity measurement device based on electric arc plasma includes: a high-voltage power supply module, a load module, a negative feedback RC coupling module, an airflow supply module, an optical observation module, a data acquisition and processing module, and a water-cooling module. The high-voltage power supply module provides a controllable high-frequency AC voltage to the load module. The load module uses non-aligned conical electrodes; when the gas between the electrodes is broken down, electric arc plasma is generated. The negative feedback RC coupling module suppresses the positive feedback process of gas discharge, achieving stable gas discharge. The optical observation module assists in electrode spacing calibration and plasma morphology observation. The airflow supply module provides a continuously adjustable gas flow. The data acquisition and processing module collects the voltage and current of the electric arc plasma at different wind speeds and processes the data to obtain the flow field velocity. The non-aligned conical electrode structure improves discharge stability and wind speed measurement stability. This device can achieve high-resolution time-correlated sequential flow field velocity measurement of hypersonic flow. By analyzing its time-frequency characteristics, characteristic changes in different flow field structures can be diagnosed, thereby achieving fine-structure diagnosis of the flow field. Attached Figure Description

[0036] Figure 1 This is a structural diagram of a flow field velocity measurement device based on electric arc plasma in one embodiment;

[0037] Figure 2 This is a schematic diagram of the electrode structure in one embodiment;

[0038] Figure 3 This is a schematic diagram of an experimental setup for measuring flow field velocity based on electric arc plasma in one embodiment.

[0039] Figure 4 This is a schematic diagram of the experimental results in another embodiment. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0041] In one embodiment, such as Figure 1 As shown, a flow field velocity measurement device based on electric arc plasma is provided. The device includes: a high-voltage power supply module 10, a load module 20, a negative feedback RC coupling module 30, an airflow supply module 40, an optical observation module 50, a data acquisition and data processing module 60, and a water cooling module 70.

[0042] The high-voltage power supply module 10 is used to provide a controllable high-frequency AC voltage to the load module 20.

[0043] The load module 20 is used to generate an electric arc plasma when the gas between the electrodes is broken down by a high-frequency AC voltage using a non-aligned conical electrode.

[0044] Specifically, it consists of two metal probes, the distance between which can be manually adjusted. The metal probes are 2mm in diameter and 40mm in length, made of tungsten-copper alloy. To prevent vibration caused by high-speed airflow, the probe tips are sharpened using a grinding machine. The probe connected to one end of the transformer is called the anode, and the probe at the ground end is called the common cathode. After the gas is broken down, a stable glow discharge plasma will be generated between the metal probes.

[0045] like Figure 2 As shown, the electrode adopts a non-aligned conical electrode structure design, which improves the stability of discharge and wind speed measurement.

[0046] The negative feedback RC coupling module 30 adopts a symmetrical structure and is connected between the high-voltage power supply module 10 and the load module 20. It is used to suppress the positive feedback process of gas discharge and realize stable gas discharge.

[0047] Specifically, the negative feedback RC coupling module 30 suppresses the positive feedback process of gas discharge, thereby achieving stable gas discharge. Its specific value can be determined based on the time constant mentioned earlier.

[0048] Stable glow discharge plasma was obtained after passing through the negative feedback RC coupling module 30. The voltage and current signals of the arc at different wind speeds were acquired using an oscilloscope. The current signal in the stable section was averaged, and the velocity-average current relationship was obtained according to the calibration relationship.

[0049] The parameter design of this function in existing technologies is mainly based on the premise that the time constant is not greater than the power supply cycle.

[0050] This solution provides a new experimental testing method for parameter design. The essence of matching parameter selection is to ensure that the arc power rises at a rate that is not too fast. Specific parameter selection can be achieved by power monitoring, testing the change in arc power after breakdown as the input voltage amplitude increases under different circuit component parameter settings, and selecting a parameter combination with a relatively slow power change.

[0051] Optical observation module 50 is used to assist in electrode spacing calibration and plasma morphology observation.

[0052] Specifically, the optical observation module consists of a microscope and a display, and its function is to assist in the calibration of electrode spacing and the observation of plasma morphology.

[0053] The airflow supply module 40 is used to provide a continuously adjustable airflow between the non-aligned conical electrodes.

[0054] Specifically, the air supply module is the air source system. The air supply module consists of three parts: a gas cylinder, valves, and a Laval nozzle. The provided air velocity can be continuously adjusted via valve control. Furthermore, a handheld industrial anemometer is used to calibrate the air velocity value; the relationship between airflow velocity and load voltage can be calibrated using the digital anemometer.

[0055] The data acquisition and processing module 60 is used to acquire the voltage and current of the arc plasma under different wind speeds, and to process the acquired voltage and current signals to obtain the flow field velocity.

[0056] The water-cooled module 70 consists of a water pump and cooling water pipes in the transformer induction coil of the power module. The water pump draws water to cool the transformer.

[0057] Specifically, the data acquisition and processing module also consists of three parts: a high-voltage probe, an oscilloscope, and a computer. The high-voltage probe is a differential high-voltage probe; the data and waveforms acquired by the oscilloscope can be transmitted to the computer system via a USB interface. Based on the pre-written post-processing program, the average current value of the stable segment of the acquired electrical signal data is calculated, and then substituted into the calibration formula to obtain the wind speed measurement value.

[0058] The workflow of the flow field velocity measurement device based on electric arc plasma includes:

[0059] (1) Check the circuit connection, ensure the insulation of each component, zero the current probe, and do not connect the high voltage probe of the oscilloscope at first;

[0060] (2) Use a microscope to align with the electrode tip of the load module and calibrate the recording electrode spacing;

[0061] (3) Turn on the water cooling system and check whether the gas cylinder is adequately filled;

[0062] (4) Adjust the gas cylinder valve, start the pressure scanning valve acquisition program, and record the pressure drop data after the airflow stabilizes;

[0063] (5) Turn on the DC power supply in the high voltage power supply module to cause breakdown between the electrodes of the load module. After the arc morphology stabilizes, connect the high voltage probe of the oscilloscope.

[0064] (6) Adjust the oscilloscope calibration line to the rising edge of the electrical signal and acquire stable voltage and current data;

[0065] (7) After the data collection is completed, the DC power supply is cut off and the air supply module 40 stops supplying air;

[0066] (8) Keep the water cooling system running and wait for the circuit components to cool down before starting the next set of tests;

[0067] This device was used for the comprehensive debugging of a hypersonic flow velocity measurement system. The system is functioning normally, with a velocity measurement range of 0-74 m / s. The average velocity sequence and pulsation time series obtained from the experimental device are analyzed for their time-frequency characteristics, which can diagnose the characteristic changes of different flow field structures, thereby achieving fine-scale flow field structure diagnosis. The flow field velocity measurement experimental device based on electric arc plasma is shown below. Figure 3 As shown.

[0068] The aforementioned flow field velocity measurement device based on electric arc plasma includes: a high-voltage power supply module, a load module, a negative feedback RC coupling module, a gas flow supply module, an optical observation module, a data acquisition and processing module, and a water cooling module. The high-voltage power supply module provides a controllable high-frequency AC voltage to the load module. The load module uses non-aligned conical electrodes; when the gas between the electrodes is broken down, electric arc plasma is generated. The negative feedback RC coupling module suppresses the positive feedback process of gas discharge, achieving stable gas discharge. The optical observation module assists in electrode spacing calibration and plasma morphology observation. The gas flow supply module provides a continuously adjustable gas flow. The data acquisition and processing module collects the voltage and current of the electric arc plasma at different wind speeds and processes the data to obtain the flow field velocity. This device can achieve high-resolution time-correlated sequential flow field velocity measurement of hypersonic flow.

[0069] In one embodiment, the high-voltage power supply module 10 includes: an AC power supply and a transformer; the voltage output by the AC power supply is controlled by the transformer.

[0070] In one embodiment, the load module 20 includes two metal probes, the distance between which is adjusted manually.

[0071] The metal probe is a tungsten-copper alloy probe with a diameter of 2mm and a length of 40mm; the metal probe has a non-aligned conical structure.

[0072] The metal probe connected to the positive terminal of the transformer is used as the anode, and the metal probe connected to the negative terminal of the transformer is used as the common cathode.

[0073] In one embodiment, the negative feedback RC coupling module 30 includes two resistors with the same resistance value and two capacitors with the same capacitance value.

[0074] One end of the first capacitor is connected to the positive output terminal of the high-voltage power supply module 10, the other end of the first capacitor is connected to one end of the first resistor, and the other end of the first resistor is connected to the anode of the load module 20.

[0075] One end of the second capacitor is connected to the negative output terminal of the high-voltage power supply module 10, the other end of the second capacitor is connected to one end of the second resistor, and the other end of the second resistor is connected to the common cathode of the load module 20.

[0076] In one embodiment, the airflow supply module 40 includes a gas cylinder, a valve, and a Laval nozzle; the valve is used to regulate the airflow speed.

[0077] In one embodiment, the optical observation module 50 includes a microscope and a display.

[0078] In one embodiment, the data acquisition and processing module 60 includes a computer system and an oscilloscope. The oscilloscope is used to acquire the voltage and current signals of the electric arc through a differential high-voltage probe and transmit them to the computer system via a USB interface. The computer system is used to receive and store the voltage and current signals of the electric arc, and to obtain the average current of the stable section by averaging the current signal of the stable section. Based on the average current of the stable section and the calibration relationship, the wind speed of the flow field is determined. The specific calibration method is as follows: the wind speed is measured by the voltage drop method. Different average currents of the stable section exist at different wind speeds. Two wind speed thresholds for switching discharge modes are selected. These two thresholds divide the entire data scatter plot into three parts. The three parts are calibrated using logarithmic, power function, and exponential functions, respectively, to obtain the piecewise calibration curve.

[0079] In one embodiment, the calibration relationship is as follows:

[0080] ;

[0081] Where V is the velocity of the flow field and I is the average current in the steady-state section.

[0082] Specifically, as the wind speed increases, the plasma discharge can be divided into three stages, and the average current growth rate of these three stages is different. For these three stages, exponential fitting, linear fitting and logarithmic fitting methods can be used respectively.

[0083] In one embodiment, the overall layout of the flow field velocity measurement device is as follows: the high-voltage power supply module 10 and the negative feedback RC coupling module 30 are integrated onto the PCB board, the load module 20 and the data acquisition line are connected to the PCB board, and then all the PCB board, the load module 20 and the data acquisition line are encapsulated inside an insulating shell.

[0084] In a verification embodiment, the flow field velocity measurement device based on electric arc plasma proposed in this application was tested and verified in a wind tunnel. The results met the expected objectives, and the experimental results are as follows: Figure 4 As shown.

[0085] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0086] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A flow field velocity measurement device based on electric arc plasma, characterized in that, The device includes: a high-voltage power supply module, a load module, a negative feedback RC coupling module, an airflow supply module, an optical observation module, a data acquisition and data processing module, and a water cooling module. The high-voltage power supply module is used to provide the load module with a controllable high-frequency AC voltage; The load module is used to generate an arc plasma when the gas between the electrodes is broken down by the high-frequency AC voltage, employing a non-aligned conical electrode. The load module includes two metal probes, which are non-aligned conical structures. The negative feedback RC coupling module adopts a symmetrical structure and is connected between the high-voltage power supply module and the load module. It is used to suppress the positive feedback process of gas discharge and realize stable gas discharge. The optical observation module is used to assist in electrode spacing calibration and plasma morphology observation; The airflow supply module is used to provide a continuously adjustable gas flow between the non-aligned conical electrodes. The data acquisition and processing module is used to acquire the voltage and current of the arc plasma under different wind speeds, and process the acquired voltage and current signals to obtain the flow field velocity. The processing includes: averaging the current signal in the stable section to obtain the average current I in the stable section, and determining the flow field velocity V based on a segmented calibration relationship based on the discharge mode switching threshold. The segmented calibration relationship divides the entire data scatter point into three segments based on the wind speed thresholds for the two discharge mode switching, and each segment is fitted using a logarithmic function, a power function, and an exponential function, respectively. The calibration relationship is as follows: Where V is the velocity of the flow field, and I is the average current in the steady-state section; The water-cooling module consists of a water pump and cooling water pipes in the transformer induction coil of the power module. The water pump draws water to cool the transformer.

2. The flow field velocity measuring device based on electric arc plasma according to claim 1, characterized in that, The high-voltage power supply module includes: an AC power supply and a transformer; The voltage output of the AC power supply is controlled by the transformer.

3. The flow field velocity measuring device based on electric arc plasma according to claim 1, characterized in that, The spacing between the two metal probes is adjusted manually. The metal probe is a tungsten-copper alloy probe with a diameter of 2 mm and a length of 40 mm; The metal probe connected to the positive terminal of the transformer is used as the anode, and the metal probe connected to the negative terminal of the transformer is used as the common cathode.

4. The flow field velocity measuring device based on electric arc plasma according to claim 1, characterized in that, The negative feedback RC coupling module includes two resistors with the same resistance and two capacitors with the same capacitance. One end of the first capacitor is connected to the positive output terminal of the high-voltage power supply module, the other end of the first capacitor is connected to one end of the first resistor, and the other end of the first resistor is connected to the anode of the load module. One end of the second capacitor is connected to the negative output terminal of the high-voltage power supply module, the other end of the second capacitor is connected to one end of the second resistor, and the other end of the second resistor is connected to the common cathode of the load module.

5. The flow field velocity measuring device based on electric arc plasma according to claim 1, characterized in that, The airflow supply module includes a gas cylinder, a valve, and a Laval nozzle; The valve is used to regulate the wind speed.

6. The flow field velocity measuring device based on electric arc plasma according to claim 1, characterized in that, The optical observation module includes a microscope and a display.

7. The flow field velocity measuring device based on electric arc plasma according to claim 1, characterized in that, The data acquisition and data processing module includes: a computer system and an oscilloscope; The oscilloscope is used to acquire the voltage and current signals of the electric arc through a differential high-voltage probe and transmit them to the computer system via a USB interface; The computer system is used to receive and store the voltage and current signals of the electric arc, and to obtain the average current of the stable section by averaging the current signal of the stable section. Based on the average current of the stable section and the calibration relationship, the wind speed of the flow field is determined.

8. The flow field velocity measuring device based on electric arc plasma according to claim 1, characterized in that, The overall layout of the flow field velocity measuring device is as follows: The high-voltage power supply module and the negative feedback RC coupling module are integrated onto the PCB board, the load module and data acquisition line are connected to the PCB board, and then all the PCB board, load module and data acquisition line are encapsulated inside an insulating shell.

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