Online oil metal pollutant detection device and method based on high-density solenoid coil

Abstract

The invention provides an oil metal pollutant online detection device and method based on a high-density solenoid coil, the device comprises a sensing unit, a flow channel assembly, a signal detection unit and a packaging structure, the sensing unit is used for generating a detection magnetic field and is composed of the high-density solenoid coil with a rectangular cross section; the flow channel assembly is used for guiding oil liquid to flow and comprises a capillary glass tube, the glass tube penetrates through the central axis of the high-density solenoid coil, and the two ends of the glass tube are fixed through stainless steel threaded clamping sleeves. The signal detection unit is used for exciting a magnetic field and detecting electromagnetic response signal change, comprises a resonant capacitor and an excitation circuit and is connected to two ends of the high-density solenoid coil; the sensing unit, the flow channel assembly and the signal detection module are integrally sealed in the metal shell through the packaging structure, and the metal shell is filled with epoxy resin to fix the sensing unit, the flow channel assembly and the signal detection module. According to the invention, the detection sensitivity and the anti-interference capability are obviously improved.

Description

Technical Field

[0001] This invention relates to the technical field of industrial equipment condition monitoring. Specifically, it relates to an online detection device and method for metal contaminants in oil based on a high-density solenoid coil. This device is particularly suitable for real-time detection of metal wear particles in oil circulation lines such as hydraulic systems and lubrication systems. By optimizing the coil structure, flow channel design, and packaging process, it achieves highly sensitive and interference-resistant metal contaminant detection, providing key technical support for fault prediction and health management of mechanical equipment. Background Art

[0002] In modern industrial production, oil circulation systems such as hydraulic systems and lubrication systems are widely used in various types of mechanical equipment. Their normal operation is crucial to ensuring the stability and reliability of the equipment. Metal wear particles in oil are a typical sign of abnormal wear of mechanical parts. Real-time detection of the size, material, and concentration of these particles is extremely important for timely detection of equipment failures, fault warnings, and equipment health management. Therefore, the development of an online detection device that can accurately detect metal contaminants in oil in real time is of great practical significance for improving the operating efficiency and safety of industrial equipment. Currently, common oil metal contaminant detection technologies include inductive, optical, and acoustic emission methods. Inductive detection is widely used due to its fast response speed and low cost. Traditional inductive sensors typically utilize a cylindrical coil design, detecting changes in coil inductance to sense the presence of metal particles in the oil. However, existing technologies still have some limitations and shortcomings in practical applications, as follows: First, the structure of existing inductive sensors has limitations. The traditional cylindrical coil design has low space utilization, resulting in limited detection sensitivity. In addition, the mechanical coupling accuracy between the flow channel and the coil is insufficient, which can easily cause signal drift under working conditions such as vibration or oil impact, affecting the accuracy and stability of detection. Secondly, the packaging reliability of existing sensors is a prominent issue. The outer shell is mostly made of plastic or ordinary metal, which lacks corrosion resistance and pressure resistance. The flow channel interface has poor sealing, which is prone to leakage after long-term use and is difficult to adapt to the complex and changing working environment of industrial sites. Furthermore, the online detection integration level of existing technologies is low. Some sensors require external complex circuits or rely on offline sampling, which cannot achieve in-situ integration of oil pipelines. The installation process often requires modification of the main oil circuit, which not only increases the difficulty and cost of installation, but also affects the continuity of system operation. For example, patent publication number CN118130314A proposes a multi-coil oil detection sensor. While this relay coil increases signal transmission distance, its flow channel is cast from a soft PDMS material, which has low mechanical strength and low coil density, resulting in insufficient ability to distinguish particles of different sizes. Furthermore, its packaging process fails to effectively address signal stability issues in vibration and high-temperature environments, making it difficult to meet the needs of long-term monitoring of heavy-duty equipment. Summary of the Invention

[0003] To address the aforementioned technical issues, a device and method for online detection of metal contaminants in oil, based on a high-density solenoid coil, are provided. This invention optimizes the magnetic field gradient distribution through a rectangular-cross-section coil and combines a capillary glass flow channel with a stainless steel ferrule for a composite sealing structure, significantly improving detection sensitivity and anti-interference capabilities. Furthermore, the use of an epoxy resin monolithic casting process ensures long-term stable operation of the sensor in high-pressure, vibration-prone environments. The device can be directly connected in parallel to the main oil circuit, simplifying installation and providing a highly efficient solution for the intelligent operation and maintenance of industrial equipment.

[0004] The technical means adopted in the present invention are as follows: An online detection device for metal contaminants in oil based on a high-density solenoid coil comprises: a sensing unit, a flow channel component, a signal detection unit and a packaging structure, wherein: The sensing unit is used to generate a detection magnetic field and is composed of a high-density solenoid coil with a rectangular cross-section; The flow channel assembly is used to guide the flow of oil and includes a capillary glass tube. The glass tube passes through the central axis of the high-density solenoid coil and is fixed at both ends by stainless steel threaded sleeves. The signal detection unit is used to excite the magnetic field and detect changes in the electromagnetic response signal, including a resonant capacitor and an excitation circuit, and is connected to both ends of the high-density solenoid coil; The packaging structure seals the sensing unit, the flow channel assembly and the signal detection module as a whole in a metal shell, and the interior of the metal shell is filled with epoxy resin to fix the sensing unit, the flow channel assembly and the signal detection module.

[0005] Furthermore, the capillary glass tube is connected in parallel with the main oil circuit through a bypass line, and when metal particles in the oil flow through the capillary glass tube, magnetization and eddy current effects are generated by the magnetic field of the high-density solenoid coil.

[0006] Furthermore, the cross-section of the high-density solenoid coil is a rectangle of 0.17 mm×0.9 mm, the number of turns is 16.5, the inner diameter is 2.2 mm, the outer diameter is 4 mm, and the axial length is 3.75 mm.

[0007] Furthermore, the high-density solenoid coil is wound with enameled copper wire of rectangular cross-section, and the number of turns and axial spacing are controlled by a CNC winding machine during winding to ensure the rectangular cross-sectional dimensional accuracy of the coil winding and the close arrangement between layers.

[0008] Furthermore, the stainless steel threaded ferrule includes an internal thread interface and an external thread locking ring. After the capillary glass tube is inserted into the ferrule, the gap is filled with epoxy resin to form a sealing structure.

[0009] Furthermore, the metal shell is made of stainless steel, and the surface of the metal shell is provided with interfaces for an oil inlet and an oil outlet, and the specifications of the interfaces match those of the main oil pipeline.

[0010] Furthermore, the resonant capacitor and the excitation circuit are integrated on a PCB board, which is welded to the leads of the high-density solenoid coil via pins and packaged in an independent chamber of a metal shell and isolated from the flow channel assembly by epoxy resin.

[0011] Furthermore, the curing parameters of the epoxy resin are: a mixing ratio of resin to curing agent of 10:1, a curing temperature of 80° C., and a curing time of 24 hours.

[0012] The present invention also provides an online detection method for metal contaminants in oil, which is implemented based on the online detection device for metal contaminants in oil based on the high-density solenoid coil, comprising: S1. Connect the oil metal contaminant online detection device in parallel to the main oil circuit through a bypass line, ensuring that the directions of the oil inlet and outlet are consistent with the flow channel markings; S2. Connect the signal detection unit, set the excitation frequency to 3.4 MHz, and the impedance sampling frequency to 250 Hz; S3. Complete the online detection preparation by calibrating the no-load reference signal; S4. When the metal particles in the oil flow through the capillary glass tube, they are magnetized and eddy current-induced by the magnetic field of the high-density solenoid coil, generating impedance signal changes. The impedance signal is collected and analyzed by the signal detection unit to achieve online detection of metal contaminants in the oil.

[0013] Compared with the prior art, the present invention has the following advantages: 1. This invention utilizes a high-density solenoid coil design with a rectangular cross-section. By optimizing the conductor arrangement (cross-sectional dimensions of 0.17 mm x 0.9 mm), the interlayer gap is reduced, achieving a more uniform axial magnetic field distribution. Experiments have shown that compared with a traditional circular coil with the same cross-sectional area, number of turns, and inner diameter, this device increases the impedance variation by approximately 60% when detecting iron particles of the same diameter. This allows for effective identification of micron-sized metal wear particles, significantly improving detection resolution.

[0014] 2. The present invention provides an online detection device for metal contaminants in oil based on a high-density solenoid coil. During the coil winding process, the number of turns and axial spacing are precisely controlled by a CNC winding machine to ensure the geometric accuracy of the rectangular cross-section and the close arrangement between layers, thereby improving the magnetic field strength.

[0015] 3. The present invention provides an online detection device for metal contaminants in oil based on a high-density solenoid coil. Its flow channel component adopts a composite sealing structure of a capillary glass tube and a stainless steel threaded ferrule, combined with an epoxy resin integral casting and packaging process, which significantly improves the sensor's pressure resistance, temperature resistance, vibration resistance and oil corrosion resistance, and adapts to harsh working conditions in industrial sites.

[0016] 3. This invention provides an online oil metal contaminant detection device based on a high-density solenoid coil. This device is connected in parallel to the main oil circuit via a bypass channel. The 2mm inner diameter channel design allows for in-situ integration without modifying the main oil circuit, and installation does not affect normal equipment operation. Its metal housing interface is compatible with standard piping, enabling rapid deployment and long-term online monitoring, providing reliable data support for real-time health management of mechanical equipment.

[0017] 4. The present invention provides an online detection device for metal contaminants in oil based on a high-density solenoid coil. The winding process of the rectangular-section enameled copper wire can achieve high-precision batch production through CNC equipment, reducing manufacturing costs; the epoxy resin encapsulation and standardized component design facilitate large-scale application and can be widely adapted to various industrial scenarios such as hydraulic systems and lubrication systems, with high engineering value.

[0018] Based on the above reasons, the present invention can be widely promoted in the fields of industrial equipment status monitoring and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0020] Figure 1 Schematic diagram of the online detection device for metal contaminants in oil according to the present invention Figure 2 Schematic diagram of a high-density solenoid coil with a rectangular cross-section according to the present invention.

[0021] Figure 3 Schematic diagram of the packaging structure of the present invention.

[0022] Figure 4 This is a signal diagram of 127 μm copper particles provided by an embodiment of the present invention.

[0023] Figure 5 A signal diagram of copper particles in a comparative test using a traditional circular cross-section coil provided in an embodiment of the present invention.

[0024] Figure 6 This is a signal diagram of 60 μm iron particles provided by an embodiment of the present invention.

[0025] Figure 7 A signal diagram of iron particles obtained by comparative testing using a conventional circular cross-section coil according to an embodiment of the present invention. DETAILED DESCRIPTION

[0026] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0027] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0028] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0029] Unless otherwise specified, the relative arrangement of the parts and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be clear that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to actual proportional relationships. The technology, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be considered as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of the exemplary embodiments can have different values. It should be noted that similar numbers and letters represent similar items in the following drawings, and therefore, once an item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0030] In the description of the present invention, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "horizontal, vertical, vertical, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention: the directional words "inside and outside" refer to the inside and outside relative to the outline of each component itself.

[0031] For ease of description, spatially relative terms such as "above," "above," "on the upper surface of," and "above" may be used herein to describe the spatial positional relationship of a device or feature to other devices or features as shown in the figures. It should be understood that spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is inverted, a device described as "above" or "on top of" another device or structure would then be positioned as "below" or "below" the other device or structure. Thus, the exemplary term "above" may include both the orientations of "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used herein should be interpreted accordingly.

[0032] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0033] like Figure 1 As shown, the present invention provides an online detection device for metal contaminants in oil based on a high-density solenoid coil, comprising: a sensing unit, a flow channel component, a signal detection unit and a packaging structure, wherein: The sensing unit is used to generate a detection magnetic field and is composed of a high-density solenoid coil with a rectangular cross section; Figure 2 shown.

[0034] The flow channel assembly is used to guide the flow of oil and includes a capillary glass tube. The glass tube passes through the central axis of the high-density solenoid coil and is fixed at both ends by stainless steel threaded ferrules. The ferrule and the capillary glass tube are sealed by pouring epoxy resin. The signal detection unit is used to excite the magnetic field and detect changes in the electromagnetic response signal, including a resonant capacitor and an excitation circuit, and is connected to both ends of the high-density solenoid coil; The packaging structure seals the sensing unit, flow channel assembly and signal detection module as a whole in a metal shell, and the metal shell is filled with epoxy resin to fix the sensing unit, flow channel assembly and signal detection module. Figure 3 shown.

[0035] In a preferred embodiment of the present invention, the capillary glass tube is connected in parallel to the main oil circuit via a bypass line. As metal particles in the oil flow through the capillary glass tube, they react with the magnetic field of the high-density solenoid coil to generate magnetization and eddy current effects. In this embodiment, the inner diameter of the bypass channel is 2 mm.

[0036] In specific implementation, as a preferred embodiment of the present invention, the cross-section of the high-density solenoid coil is a rectangle of 0.17 mm×0.9 mm, the number of turns is 16.5, the inner diameter is 2.2 mm, the outer diameter is 4 mm, and the axial length is 3.75 mm.

[0037] In practice, as a preferred embodiment of the present invention, the high-density solenoid coil is wound using enameled copper wire with a rectangular cross-section. During winding, a CNC winding machine controls the number of turns and axial spacing to ensure the rectangular cross-sectional dimensions of the coil winding and the close arrangement of the layers. In this embodiment, the cross-sectional dimensions of the copper wire are 0.17 mm in width and 0.9 mm in height. In specific implementation, as a preferred embodiment of the present invention, the stainless steel threaded ferrule includes an internal thread interface and an external thread locking ring. After the capillary glass tube is inserted into the ferrule, the gap is filled with epoxy resin to form a sealing structure.

[0038] In specific implementation, as a preferred embodiment of the present invention, the metal shell is made of stainless steel, and the surface of the metal shell is provided with interfaces for oil inlet and oil outlet, and the interface specifications match the main oil pipeline.

[0039] In specific implementation, as a preferred embodiment of the present invention, the resonant capacitor and the excitation circuit are integrated into a PCB board, the PCB board is welded to the leads of the high-density solenoid coil through pins, and is encapsulated in an independent chamber of a metal shell and isolated from the flow channel assembly by epoxy resin.

[0040] In a specific implementation, as a preferred embodiment of the present invention, the curing parameters of the epoxy resin are: a mixing ratio of resin to curing agent of 10:1, a curing temperature of 80° C., and a curing time of 24 hours.

[0041] The present invention also provides an online detection method for metal contaminants in oil, which is implemented based on the above-mentioned online detection device for metal contaminants in oil based on a high-density solenoid coil, comprising: S1. Connect the oil metal contaminant online detection device in parallel to the main oil circuit through a bypass line, ensuring that the directions of the oil inlet and outlet are consistent with the flow channel markings; S2. Connect the signal detection unit, set the excitation frequency to 3.4 MHz, and the impedance sampling frequency to 250 Hz; S3. Complete the online detection preparation by calibrating the no-load reference signal; S4. When the metal particles in the oil flow through the capillary glass tube, they are magnetized and eddy current-induced by the magnetic field of the high-density solenoid coil, generating impedance signal changes. The impedance signal is collected and analyzed by the signal detection unit to achieve online detection of metal contaminants in the oil.

[0042] Example Step 1: Sensor Assembly Pre-assembly of the housing: Fix the PCB board of the integrated measurement circuit in the card slot inside the stainless steel housing. After the circuit is soldered, pass it through the hole reserved on the top of the housing and use the bracket on the housing to fix the PCB board. Flow channel installation: insert the capillary glass tube with an outer diameter of 2mm from the flow channel hole reserved on the left side of the shell, pass through the central axis of the high-density solenoid coil in sequence, and exit from the flow channel hole on the right side. Adjust the capillary glass tube so that it is strictly centered; Ferrule fixing: Screw stainless steel threaded ferrules into both ends of the capillary glass tube. The ferrules include an internal thread interface and an external thread locking ring. Tighten them with a torque wrench at a torque of 5 N·m to form a mechanical seal. Epoxy resin pouring: Mix epoxy resin and curing agent in a ratio of 10:1 and stir thoroughly. Remove bubbles through vacuum degassing. Slowly inject the mixture from the injection port on the top of the housing until it completely covers the PCB board, coil, and flow channel components. Curing molding: Place the injected sensor in an 80°C constant temperature oven for 24 hours to complete the epoxy resin curing, forming an integrated packaging structure that is resistant to vibration and oil corrosion.

[0043] Step 2: System connection and debugging Connect the sensor in parallel to the main oil circuit through a bypass line, ensuring that the directions of the oil inlet and outlet are consistent with the flow channel markings; Connect the excitation circuit to the data acquisition unit, set the excitation frequency to 3.4 MHz, and the impedance sampling frequency to 250 Hz; Initialize the detection system through LabVIEW software, calibrate the no-load reference signal, and complete the online detection preparation.

[0044] Step 3: Copper particle detection experiment Test conditions: Test particles: spherical copper particles with a diameter of 127 μm; Oil flow rate: 0.2L / min; Excitation frequency: 3.4MHz; Data acquisition: Real-time impedance signals were recorded by an impedance analyzer.

[0045] Experimental results: like Figure 4 As shown in the figure, when copper particles pass through the sensor, the impedance signal presents a positive pulse peak, and the average peak amplitude is 203 (the original value of the sensor register). The image shows that the sensor has high sensitivity to detecting ultra-small non-ferromagnetic particles. Figure 5 For comparison tests using a traditional circular cross-section coil, it was found that the particle signal could not be measured correctly.

[0046] Step 4: Iron particle detection experiment Test conditions: Test particles: spherical iron particles with a diameter of 60 μm; Oil flow rate: 0.2L / min; Excitation frequency: 3.4MHz; Experimental results: like Figure 6 As shown in the figure, when iron particles pass through the sensor, the impedance signal presents a negative pulse peak, and the average peak amplitude is -1972 (the original value of the sensor register); Figure 7 For comparative testing using a traditional circular cross-section coil, the average peak amplitude was -1573 (raw value in the sensor register), verifying the sensor's excellent ability to distinguish ferromagnetic particles.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An online detection device for metal contaminants in oil based on a high-density solenoid coil, characterized in that: include: Sensing unit, flow channel assembly, signal detection unit and packaging structure, wherein: The sensing unit is used to generate a detection magnetic field and is composed of a high-density solenoid coil with a rectangular cross-section; The flow channel assembly is used to guide the flow of oil and includes a capillary glass tube. The glass tube passes through the central axis of the high-density solenoid coil and is fixed at both ends by stainless steel threaded sleeves. The signal detection unit is used to excite the magnetic field and detect changes in the electromagnetic response signal, including a resonant capacitor and an excitation circuit, and is connected to both ends of the high-density solenoid coil; The packaging structure seals the sensing unit, the flow channel assembly and the signal detection module as a whole in a metal shell, and the interior of the metal shell is filled with epoxy resin to fix the sensing unit, the flow channel assembly and the signal detection module.

2. The on-line detection device for metal contaminants in oil based on a high-density solenoid coil according to claim 1 is characterized in that: The capillary glass tube is connected in parallel with the main oil circuit through a bypass line. When metal particles in the oil flow through the capillary glass tube, magnetization and eddy current effects are generated with the magnetic field of the high-density solenoid coil.

3. The on-line detection device for metal contaminants in oil based on a high-density solenoid coil according to claim 1 is characterized in that: The high-density solenoid coil has a cross-section of a 0.17 mm×0.9 mm rectangle, 16.5 turns, an inner diameter of 2.2 mm, an outer diameter of 4 mm, and an axial length of 3.75 mm.

4. The on-line detection device for metal contaminants in oil based on a high-density solenoid coil according to claim 3 is characterized in that: The high-density solenoid coil is wound with enameled copper wire of rectangular cross-section. During winding, the number of turns and the axial spacing are controlled by a CNC winding machine to ensure the rectangular cross-section dimensional accuracy of the coil winding and the close arrangement between layers.

5. The on-line detection device for metal contaminants in oil based on a high-density solenoid coil according to claim 1 is characterized in that: The stainless steel threaded ferrule comprises an internal thread interface and an external thread locking ring. After the capillary glass tube is inserted into the ferrule, the gap is filled with epoxy resin to form a sealing structure.

6. The on-line detection device for metal contaminants in oil based on a high-density solenoid coil according to claim 1 is characterized in that: The metal shell is made of stainless steel, and the surface of the metal shell is provided with interfaces for an oil inlet and an oil outlet, and the interface specifications match those of the main oil pipeline.

7. The on-line detection device for metal contaminants in oil based on a high-density solenoid coil according to claim 1 is characterized in that: The resonant capacitor and the excitation circuit are integrated on a PCB board, which is welded to the leads of the high-density solenoid coil via pins and packaged in an independent chamber of a metal shell and isolated from the flow channel assembly by epoxy resin.

8. The on-line detection device for metal contaminants in oil based on a high-density solenoid coil according to claim 1 is characterized in that: The curing parameters of the epoxy resin are: a mixing ratio of resin to curing agent of 10:1, a curing temperature of 80° C., and a curing time of 24 hours.

9. An online detection method for metal contaminants in oil, implemented by the online detection device for metal contaminants in oil based on a high-density solenoid coil according to any one of claims 1 to 8, characterized in that: include: S1. Connect the oil metal contaminant online detection device in parallel to the main oil circuit through a bypass line, ensuring that the directions of the oil inlet and outlet are consistent with the flow channel markings; S2. Connect the signal detection unit, set the excitation frequency to 3.4 MHz, and the impedance sampling frequency to 250 Hz; S3. Complete the online detection preparation by calibrating the no-load reference signal; S4. When the metal particles in the oil flow through the capillary glass tube, they are magnetized and eddy current-induced by the magnetic field of the high-density solenoid coil, generating impedance signal changes. The impedance signal is collected and analyzed by the signal detection unit to achieve online detection of metal contaminants in the oil.

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