A wheatstone bridge type oil detection sensor

Abstract

The application provides a Wheatstone bridge type oil detection sensor, comprising a Wheatstone microfluid chip and a conditioning circuit, wherein the Wheatstone microfluid chip comprises a glass slide, a PDMS arranged on the glass slide, a Wheatstone bridge fixed on the PDMS and a microfluid channel, wherein the Wheatstone bridge is used for detecting a particle-containing oil signal and a particle-free signal, and comprises a reference coil, a detection coil, an adjustable potentiometer and an adjustable capacitor; the signal conditioning circuit is connected with the Wheatstone bridge and comprises an excitation unit, a differential amplifier, a lock-in amplifier circuit, an operational amplifier and a data export card connected in an electrical manner. The Wheatstone bridge combined with the signal conditioning circuit can be used for accurate detection at various temperatures, the temperature drift problem of the detection signal under a high-temperature condition is solved, and the signal-to-noise ratio of the abrasive particle detection under various temperatures is improved. The sensor is suitable for a lubricant detection system with varying or constant high oil temperature, and has important significance for health evaluation and fault diagnosis of a mechanical system.

Description

Technical Field

[0001] This invention relates to the field of oil detection technology, and more particularly to a Wheatstone bridge-type oil detection sensor. Background Technology

[0002] For large marine machinery operating at sea, unlike land-based equipment where damaged parts can be repaired or replaced immediately, malfunctions can be severe, even causing personal injury and property damage. Therefore, researching methods for detecting abrasive particles in the oil of large marine machinery is crucial for understanding equipment failures and extending its service life. Existing detection methods are mainly divided into online monitoring and offline testing. Major offline methods include spectral analysis, ferrography, and laboratory microscopy. Most of these methods require pre-collecting oil samples and sending them to the laboratory for testing. The testing cycle is long and requires specialized personnel. For large machinery such as ships, as well as offshore wind turbines, the health status cannot be determined from the time the oil sample arrives at the laboratory until testing is completed, making it impossible to provide timely warnings of malfunctions and potentially causing safety hazards. Conversely, online monitoring can provide real-time detection information for machinery. Currently, online monitoring oil sensors are mainly divided into acoustic sensors, optical sensors, and impedance sensors. Acoustic and optical sensors require high oil cleanliness, and their results are easily affected by impurities. Impedance sensors have advantages such as simple structure, low cost, high detection accuracy, and high stability.

[0003] However, all the above studies were conducted in a laboratory environment. The impact of temperature changes in the sensor itself and the detection medium during actual operation on the detection results was not considered. During long-term monitoring, electromagnetic sensors generate heat during prolonged operation, affecting the detection results. The heat generation problem is mainly concentrated in high-resistance coils, which overheat under strong AC excitation, leading to unstable coil characteristics and affecting the detection results. For low-resistance coils, it is important to note that during long-term online monitoring, the coil temperature gradually converges to the temperature of the detection medium; this temperature difference may alter the coil's parameter characteristics, affecting the detection results. When the lubrication system of large machinery such as ships starts operating, the lubricating oil needs to be preheated to around 40°C. After lubricating and cooling critical components, the lubricating oil temperature can reach 70°C or even higher. Some electromagnetic sensors with ferrite cores, silicon steel sheets, and other high-permeability materials are highly sensitive to high temperatures. Summary of the Invention

[0004] To address the technical problem of decreased detection accuracy at high temperatures caused by chip characteristics in existing oil detection technologies based on Wheatstone bridges, this invention provides a Wheatstone bridge-based oil detection sensor. This invention primarily utilizes a Wheatstone bridge combined with a signal conditioning circuit to achieve accurate detection at various temperatures, effectively solving the problem of temperature drift in detection signals under high-temperature conditions and improving the signal-to-noise ratio of abrasive particle detection at multiple temperatures.

[0005] The technical means employed in this invention are as follows:

[0006] A Wheatstone bridge-type oil detection sensor includes: a Wheatstone microfluidic chip and a conditioning circuit, wherein:

[0007] The Wheatstone microfluidic chip includes a glass substrate, a PDMS disposed on the glass substrate, a Wheatstone bridge fixed on the PDMS, and microchannels, wherein:

[0008] The Wheatstone bridge, used to detect oil signals with and without particles, includes a reference coil, a detection coil, an adjustable potentiometer, and an adjustable capacitor.

[0009] The signal conditioning circuit is connected to a Wheatstone bridge and includes an excitation unit, a differential amplifier, a lock-in amplifier circuit, an operational amplifier, and a data export card that are electrically connected.

[0010] Furthermore, the microchannel includes a first microchannel and a second microchannel arranged parallel to each other. The first microchannel passes through the center of the reference coil, and the second microchannel passes through the center of the detection coil. The end of the reference coil is connected to an adjustable potentiometer via an insulated wire, and the end of the detection coil is connected to an adjustable capacitor via an insulated wire.

[0011] Furthermore, the first microchannel is used to inject particle-free lubricating oil as a reference oil; the second microchannel is used to inject lubricating oil containing iron particles as a test oil.

[0012] Furthermore, the reference coil is used as a reference for the detection coil, and the detection coil is used to change the magnetic field within the sensor's detection area.

[0013] Furthermore, the reference coil and the detection coil are two identical two-wire solenoid coils, both wound with copper wire of 70μm diameter, with 230 turns, an outer diameter of 3.1mm, an inner diameter of 1.1mm, and a height of 3mm.

[0014] Furthermore, the Whistler microfluidic chip is also provided with acrylic blocks. Two acrylic blocks are provided. One block is located directly below the overlapping position of the first microchannel and the reference coil to elevate the first microchannel and the reference coil. The other block is located directly below the overlapping position of the second microchannel and the detection coil to elevate the second microchannel and the detection coil.

[0015] Furthermore, in the signal conditioning circuit:

[0016] The excitation unit is used to provide a reference signal for the lock-in amplifier and to provide AC excitation for the sensor;

[0017] The differential amplifier is used to differentially divide the voltage signals at the two ports of the Wheatstone bridge output signal terminal, so that the signal output by the Wheatstone bridge is an AC signal, thereby reducing the noise signal when detecting iron particles.

[0018] The lock-in amplifier circuit is used to convert the sensor's detection signal into a DC signal;

[0019] The operational amplifier is used to amplify the particle signal;

[0020] The data export card is used to import the processed data from the circuit into the computer.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. The Wheatstone bridge oil detection sensor provided by this invention can accurately detect ferromagnetic particles in oil at high temperatures without affecting the detection accuracy. It effectively solves the problem of temperature drift of detection signal under high temperature conditions and improves the signal-to-noise ratio of abrasive particle detection at multiple temperatures.

[0023] 2. The Wheatstone bridge-type oil detection sensor provided by this invention is suitable for lubricant detection systems with varying or constant high oil temperatures, and is of great significance for health assessment and fault diagnosis of mechanical systems.

[0024] Based on the above reasons, this invention can be widely applied in fields such as oil detection. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1This is a structural diagram of the Wheatstone microfluidic chip of the present invention.

[0027] Figure 2 This is a diagram of the Wheatstone bridge and conditioning circuit of the present invention.

[0028] Figure 3 This is a data graph of 150μm iron particles at 20-70℃ provided in an embodiment of the present invention.

[0029] In the diagram: 1. Reference coil; 2. Detection coil; 3. Adjustable potentiometer; 4. First microchannel; 5. Second microchannel; 6. Acrylic block; 7. PDMS; 8. Glass carrier; 9. Adjustable capacitor; 10. Excitation unit; 11. Differential amplifier; 12. Lock-in amplifier circuit; 13. Operational amplifier; 14. Data export card; 15. Wheatstone bridge. Detailed Implementation

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0033] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0034] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0035] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and in relation to the spatial relationships used herein...

[0036] The corresponding descriptions should be explained accordingly.

[0037] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0038] like Figure 1 As shown, the present invention provides a Wheatstone bridge-type oil detection sensor, comprising: a Wheatstone microfluidic chip and a conditioning circuit, wherein:

[0039] The Wheatstone microfluidic chip includes a glass substrate 8, a PDMS7 disposed on the glass substrate 8, a Wheatstone bridge 15 fixed on the PDMS7, and microchannels, wherein:

[0040] The Wheatstone bridge 15 is used to detect oil signals with particles and signals without particles, and includes a reference coil 1, a detection coil 2, an adjustable potentiometer 3, and an adjustable capacitor 9.

[0041] like Figure 2 As shown, the signal conditioning circuit, connected to the Wheatstone bridge 15, includes an excitation unit 10, a differential amplifier 11, a lock-in amplifier circuit 12, an operational amplifier 13, and a data export card 14 that are electrically connected.

[0042] In specific implementation, as a preferred embodiment of the present invention, please refer to [reference needed]. Figure 1 The microchannel includes a first microchannel 4 and a second microchannel 5 arranged in parallel with each other. The first microchannel 4 passes through the center of the reference coil 1, and the second microchannel 5 passes through the center of the detection coil 2. The end of the reference coil 1 is connected to an adjustable potentiometer 3 through an insulated wire, and the end of the detection coil 2 is connected to an adjustable capacitor 9 through an insulated wire.

[0043] In a specific implementation, as a preferred embodiment of the present invention, the first microchannel 4 is used to inject particle-free lubricating oil as a reference oil; the second microchannel 5 is used to inject lubricating oil containing iron particles as a detection oil.

[0044] In a preferred embodiment of the present invention, the reference coil 1 is used as a reference for the detection coil, and the detection coil 2 is used to change the magnetic field within the sensor detection area. The reference coil 1 and the detection coil 2 are two identical double-wire solenoid coils, both wound with copper wire of 70 μm diameter. The coils have 230 turns, an outer diameter of 3.1 mm, an inner diameter of 1.1 mm, and a height of 3 mm.

[0045] In specific implementation, as a preferred embodiment of the present invention, please refer to [reference needed]. Figure 1 The Whistler microfluidic chip is also provided with an acrylic block 6. There are two acrylic blocks 6. One is located directly below the overlapping position of the first microchannel 4 and the reference coil 1, which is used to elevate the first microchannel 4 and the reference coil 1. The other is located directly below the overlapping position of the second microchannel 5 and the detection coil 2, which is used to elevate the second microchannel 5 and the detection coil 2.

[0046] In specific implementation, as a preferred embodiment of the present invention, please refer to [reference needed]. Figure 2 In the signal conditioning circuit: the excitation unit 10 provides a reference signal for the lock-in amplifier and an AC excitation for the sensor; the differential amplifier 11 differentially divides the voltage signals at the two ports of the bridge output signal terminal, making the signal output by the Wheatstone bridge 15 an AC signal, greatly reducing the noise signal during iron particle detection and making the particle detection signal more obvious; the lock-in amplifier circuit 12 converts the sensor's detection signal into a DC signal; the operational amplifier 13 amplifies the particle signal; and the data export card 14 imports the processed data into a computer.

[0047] Example

[0048] First, 150μm iron particles are accurately measured using a microscope. Lubricating oil containing 150μm iron particles is injected into the first microchannel 4. The second microchannel 3, used as a reference channel, only passes through the lubricating oil and not through the abrasive particles. Under conditions where the water temperature is heated from 20℃ to 70℃, detection is performed at 10℃ intervals. At each temperature, when a 150μm iron particle passes through the detection coil, it generates an electromagnetic pulse. Figure 3 As shown.

[0049] In summary, the oil detection method based on a Wheatstone bridge microfluidic chip proposed in this invention can accurately and stably detect ferromagnetic particles of 75-400μm at relatively high temperatures of 20-70℃, solving the problem of signal drift in oil detection at various temperatures.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions 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. A Wheatstone bridge-type oil detection sensor, characterized in that, include: Wheatstone microfluidic chip and conditioning circuit, wherein: The Wheatstone microfluidic chip includes a glass substrate (8), a PDMS (7) disposed on the glass substrate (8), a Wheatstone bridge (15) fixed on the PDMS (7), and microchannels, wherein: The Wheatstone bridge (15) is used to detect oil signals with particles and signals without particles, and includes a reference coil (1), a detection coil (2), an adjustable potentiometer (3) and an adjustable capacitor (9). The signal conditioning circuit, connected to the Wheatstone bridge (15), includes an electrically connected excitation unit (10), a differential amplifier (11), a lock-in amplifier circuit (12), an operational amplifier (13), and a data export card (14).

2. The Wheatstone bridge-type oil detection sensor according to claim 1, characterized in that, The microchannel includes a first microchannel (4) and a second microchannel (5) arranged in parallel with each other. The first microchannel (4) passes through the center of the reference coil (1), and the second microchannel (5) passes through the center of the detection coil (2). The end of the reference coil (1) is connected to an adjustable potentiometer (3) through an insulated wire, and the end of the detection coil (2) is connected to an adjustable capacitor (9) through an insulated wire.

3. The Wheatstone bridge-type oil detection sensor according to claim 2, characterized in that, The first microchannel (4) is used to inject particle-free lubricating oil as a reference oil; the second microchannel (5) is used to inject lubricating oil containing iron particles as a test oil.

4. The Wheatstone bridge-type oil detection sensor according to claim 1, characterized in that, The reference coil (1) is used as a reference for the detection coil, and the detection coil (2) is used to change the magnetic field in the sensor detection area.

5. The Wheatstone bridge-type oil detection sensor according to claim 1, characterized in that, The reference coil (1) and the detection coil (2) are two identical double-wire solenoid coils, both made of copper wire with a diameter of 70μm. The coil has 230 turns, an outer diameter of 3.1mm, an inner diameter of 1.1mm, and a height of 3mm.

6. The Wheatstone bridge-type oil detection sensor according to claim 1, characterized in that, The Whistler microfluidic chip is also provided with an acrylic block (6). There are two acrylic blocks (6). One is located directly below the overlapping position of the first microchannel (4) and the reference coil (1) to raise the first microchannel (4) and the reference coil (1). The other is located directly below the overlapping position of the second microchannel (5) and the detection coil (2) to raise the second microchannel (5) and the detection coil (2).

7. The Wheatstone bridge-type oil detection sensor according to claim 1, characterized in that, In the signal conditioning circuit: The excitation unit (10) is used to provide a reference signal for the lock-in amplifier and to provide AC excitation for the sensor; The differential amplifier (11) is used to differentially divide the voltage signals at the two ports of the bridge output signal terminal, so that the signal output by the Wheatstone bridge (15) is an AC signal, thereby reducing the noise signal when detecting iron particles. The lock-in amplifier circuit (12) is used to convert the sensor's detection signal into a DC signal; The operational amplifier (13) is used to amplify the particle signal; The data export card (14) is used to import the processed data from the circuit into the computer.

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