A welding rod moisture measurement device and measurement method based on interdigital capacitive sensor

Abstract

The present invention discloses a welding rod moisture measuring device based on a forked-finger capacitive sensor, which comprises a sensor assembly, a bracket and a positioning assembly; the sensor assembly comprises a forked-finger electrode and a U-shaped supporting spring piece, the two top ends of the U-shaped supporting spring piece are provided with electrode connecting tubes, and the forked-finger electrode is connected between the two electrode connecting tubes; the bracket comprises a support plate, an upper baffle and a lower baffle fixed on both sides of the support plate; the lower end of the U-shaped supporting spring piece is fixedly connected to the support plate, and the two side walls of the U-shaped supporting spring piece are located between the upper baffle and the lower baffle; the positioning assembly comprises a welding rod fixing device and a guide rod, and the support plate is slidably connected to the guide rod; the forked-finger electrode can be moved in the direction of the welding rod by sliding the support plate on the guide rod, so that the forked-finger electrode is tightly fitted to the welding rod to achieve measurement; the present invention has a simple structure, is easy to carry, has high measurement accuracy, and can achieve fast, non-destructive, and real-time detection.

Description

Technical Field

[0001] The present invention relates to the field of sensor measurement technology, and in particular to a welding rod moisture measurement device and a measurement method based on an interdigital capacitive sensor. Background Art

[0002] Welding rods are key materials in welding technology and play an indispensable role in today's welding process. Welding rods are very susceptible to moisture. Improper storage can lead to problems such as bubbles and slag inclusions during welding. Therefore, it is necessary to test the humidity of welding rods before welding to ensure welding quality and improve welding rod utilization. In addition, the moisture contained in welding rods is one of the main sources of hydrogen in welding. By controlling the hydrogen content of welding rod coatings, the welding quality can be effectively improved. Most of the hydrogen in the weld is in the form of H2 and H3. + 、H - It exists in the form of solid molten droplets with the weld metal; various atmospheric parameters will have a significant impact on the humidity of the welding rod. The welding rod contains a large amount of hydrogen. Usually, the dielectric constant of the welding rod compound medium is around 3-7. When the proportion of water vapor increases, the dielectric constant of the air will change; the relative dielectric constant of water is 78.5, which is much higher than the relative dielectric constant of the welding rod. When the water content in the welding rod increases, the equivalent dielectric constant of the welding rod coating will increase accordingly.

[0003] Currently, the main methods for measuring welding rod moisture include the resistance-capacitance method and the drying method. In earlier national standards, the test for measuring the moisture content of welding rod coatings involved using a peeled coating as a sample. The sample was placed in a heating furnace at (980±15)°C, flowed with oxygen, and held for 30 minutes. The moisture was absorbed by a U-shaped absorption tube filled with anhydrous magnesium perchlorate, and the weight gain of the U-shaped tube was measured as the sample's moisture content. However, this method suffers from long cycle times, poor accuracy, high welding rod loss rates, and impracticality for field operation. To rapidly and accurately determine the moisture content of welding rod coatings, DE Bunnel proposed the Karl-Fischer potentiometric titration method (volumetric method). This method can test a wide range of materials, has low sensitivity, and is less susceptible to interference from side reactions. However, the apparatus is complex, requires large consumables, and the measurement time is long, making it difficult to carry around.

[0004] In addition, in the utility model patent application number ZL97201190.0, when measuring the humidity of the welding rod, the electrode is prone to rust due to its structure. At the same time, manual pressure is used to tightly bind the electrode to the surface of the welding rod during measurement. Due to the different pressing forces, the sensor data contains errors. Although the invention patent application number ZL201710024398.6 structurally solves the problems of electrode rust and errors caused by manual pressure in the above invention, the welding core of this invention is wrapped by two electrodes, and a parallel capacitance is generated between the electrode and the welding rod core. When the welding core is eccentric, the generated parallel capacitance value is inconsistent, affecting the detection results. At the same time, during measurement, the dielectric constant of its filler affects the detection results of the welding rod humidity. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a welding rod moisture measurement device and method based on an interdigital capacitive sensor, so as to solve the technical problems of low welding rod moisture measurement efficiency and low measurement accuracy in the prior art.

[0006] In order to solve the above technical problems, the present invention is implemented by adopting the following technical solutions:

[0007] In a first aspect, the present invention provides a welding rod moisture measurement device based on an interdigital capacitive sensor, comprising a sensor assembly, a bracket, and a positioning assembly;

[0008] The sensor assembly includes interdigitated electrodes and a U-shaped supporting spring. Both top ends of the U-shaped supporting spring are provided with electrode connecting tubes, and the interdigitated electrodes are connected between the two electrode connecting tubes.

[0009] The bracket includes a support plate, an upper baffle and a lower baffle fixed on both sides of the support plate; the lower end of the U-shaped support spring is fixedly connected to the support plate, and the two side walls of the U-shaped support spring are located between the upper baffle and the lower baffle, and the upper baffle and the lower baffle limit the outward elastic deformation of the two side walls of the U-shaped support spring;

[0010] The positioning assembly includes a welding rod fixing device and a guide rod, the welding rod is placed on the welding rod fixing device, and the support plate is slidably connected to the guide rod; through the sliding of the support plate on the guide rod, the interdigitated electrode can move toward the direction of the welding rod, so that the interdigitated electrode is tightly attached to the welding rod to achieve measurement.

[0011] Preferably, the outer surface of the interdigital electrode is wrapped with a polyester PET film.

[0012] Preferably, the interdigitated electrodes include an upper electrode and a lower electrode, the upper electrode and the lower electrode have the same number of interdigitated segments, and the interdigitated segments of the upper electrode and the lower electrode are arranged crosswise to form a periodic structure.

[0013] Preferably, the positioning assembly includes a base, on which two symmetrical support columns are installed; the welding rod fixing device includes two symmetrical welding rod placement columns installed on the base; there are two guide rods, and the two ends of one of the guide rods are respectively fixed on one of the support columns and one of the welding rod placement columns; the two ends of the other guide rod are respectively fixed on the other support column and the other welding rod placement column.

[0014] Preferably, both of the welding rod placement columns are provided with V-shaped grooves for placing welding rods.

[0015] Preferably, the support plate includes a support bar and support blocks connected to both ends of the support bar; the support block is fixedly sleeved with a hollow stepped shaft, and the hollow stepped shaft is sleeved on a guide rod and slidably connected to the guide rod.

[0016] Preferably, the welding rod fixing device also includes a column and a rocker arm; the column is fixed on the base, the top end of the rocker arm is rotatably connected to one end of the connecting rod, and the other end of the connecting rod is fixedly connected to the top end of the column; the rod body of the rocker arm is connected to the column body of the column through a spring; the rocker arm can swing in the direction of the welding rod to fix the welding rod against the V-shaped groove of the welding rod placement column.

[0017] Preferably, it also includes a winding wheel, on which a traction rope is wound; the rotating shaft of the winding wheel is connected to the knob; a pulley is provided on the rocker arm; one end of the traction rope is fixed in the winding wheel, and the other end is moved out from the winding wheel, wrapped around the pulley, and then fixed to the center position of the support plate.

[0018] Preferably, the number of the sensor components is set to four, and the four sensor components are fixed on the support plate at even intervals.

[0019] In a second aspect, the present invention provides a method for measuring welding rod moisture using the welding rod moisture measuring device based on an interdigital capacitive sensor according to the first aspect, the method comprising the following steps:

[0020] The welding rod moisture measurement device based on the interdigital capacitive sensor is grounded using a grounding lead to eliminate the influence of stray capacitance on the measurement;

[0021] connecting the upper electrode and the lower electrode of the interdigitated electrode with a lead to eliminate residual charge;

[0022] placing the welding rod on the V-shaped groove of the welding rod placement column;

[0023] Turn the knob to drive the winding wheel to reel in the traction rope. During the reeling process, the traction rope pulls the support plate toward the welding rod through the pulley. At the same time, the pulley drives the swing arm to firmly press the welding rod against the V-shaped groove. The elasticity of the support spring causes the interdigital electrodes to deform elastically until the interdigital electrodes are completely and tightly attached to the outer surface of the welding rod. Stop turning the knob to start measuring.

[0024] Connect an external capacitance detection instrument through the interdigital electrode leads to measure the capacitance;

[0025] The relationship between the capacitance measured by the interdigital capacitive sensor and the moisture content of the welding rod is calibrated using the national standard GB-5117 1995 measurement method, so that the humidity of the welding rod can be obtained based on the measured capacitance C.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] Compared with conventional sensor electrodes that rely on fillers for fixing and supporting, the present invention connects the interdigital electrodes to the two ends of the U-shaped supporting spring and places them in the air, thereby avoiding the influence of the relative dielectric constant of other fillers on the sensor detection results during the measurement process. At the same time, the interdigital electrodes are used, and their interdigital structural characteristics are utilized to avoid the influence of the parallel capacitance generated by the eccentricity of the welding rod core on the detection results, thereby improving the measurement accuracy. The present invention utilizes the characteristics of the flexible material of the interdigital electrodes to enable the interdigital electrodes to fit tightly to the welding rod to achieve measurement, thereby solving the problem of linear sensitivity within the high bending stress range such as wrapped welding rods. In conjunction with the welding rod fixing device, the humidity of different types of welding rods can be measured. In addition, the outer surface of the interdigital electrodes is wrapped with a polyester PET film, which completely covers the interdigital electrodes and prevents them from contacting the air, thereby reducing the wear on the interdigital electrodes during the measurement process and increasing their service life. The present invention has accurate measurement, simple structure, and is easy to carry. It can be widely used in welding sites, welding rod storage, and other places. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 2 is a schematic diagram of the front three-dimensional structure of a welding rod moisture measurement device based on an interdigital capacitive sensor provided by an embodiment of the present invention;

[0029] Figure 2 2. It is a schematic diagram of the back three-dimensional structure of a welding rod moisture measurement device based on an interdigital capacitive sensor provided by an embodiment of the present invention;

[0030] Figure 3 This is a schematic structural diagram of the connection between a traction rope, a pulley, and a support bar provided by an embodiment of the present invention;

[0031] Figure 4 The embodiment of the present invention provides Figure 3 A top view of

[0032] Figure 5 is a structural diagram of a sensor assembly provided by an embodiment of the present invention;

[0033] Figure 6 This is a schematic structural diagram of an electrode connecting tube provided by an embodiment of the invention;

[0034] Figure 7 Schematic diagram of the structure of the connection between the column and the swing arm provided by an embodiment of the present invention;

[0035] Figure 8 is a structural schematic diagram of a support plate provided by an embodiment of the present invention;

[0036] Figure 9 Schematic diagram of the structure of the support column and welding rod placement column provided by an embodiment of the present invention;

[0037] Figure 10 1 is a schematic structural diagram of a hollow stepped shaft provided by an embodiment of the present invention and its connection with a guide rod and a support block;

[0038] Figure 11 is a schematic structural diagram of an interdigitated electrode provided by an embodiment of the present invention;

[0039] Figure 12 Schematic diagram of inter-electrode capacitance distribution of an interdigital electrode sensor during measurement provided by an embodiment of the present invention;

[0040] In the figure: 1. Sensor assembly; 11. Interdigitated electrode; 12. U-shaped supporting spring; 13. Electrode connecting tube; 14. Upper electrode; 15. Lower electrode; 2. Bracket; 21. Support plate; 22. Upper baffle; 23. Lower baffle; 24. Support bar; 25. Support block; 26. Hollow stepped shaft; 3. Positioning assembly; 31. Welding rod fixing device; 32. Guide rod; 33. Base; 34. Support column; 35. Welding rod placement column; 36. Column; 37. Rocker arm; 38. Connecting rod; 39. Spring; 4. Welding rod; 5. Winding wheel; 51. Traction rope; 52. Knob; 53. Pulley. DETAILED DESCRIPTION

[0041] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0042] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0043] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0044] Example 1

[0045] Reference Figures 1 to 4 The welding rod moisture measuring device based on the interdigital capacitive sensor provided by the embodiment of the present invention includes a sensor component 1, a bracket 2 and a positioning component 3; specifically, Figure 5 The sensor assembly 1 shown includes a forked electrode 11 and a U-shaped supporting spring 12. Both top ends of the U-shaped supporting spring 12 are provided with an electrode connecting tube 13. The forked electrode 11 is connected between the two electrode connecting tubes 13. The outer surface of the forked electrode 11 is wrapped with a polyester PET film. The electrode connecting tube 13 and the U-shaped supporting spring 12 are connected in a closed loop from end to end. The material of the U-shaped supporting spring 12 in the embodiment of the present invention is stainless steel foil, and the selected model is 304. The thickness of the U-shaped supporting spring 12 is 0.1mm, the length is 70mm, the width is 25mm, and there is a round hole in the middle with a diameter of 2mm. In addition, the material of the electrode connecting tube 13 in the embodiment of the present invention is steel foil, and the model is 304. Its outer diameter is 1mm, the length is 28mm, and the wall thickness is 0.1mm. Figure 6 The electrode connecting tube 13 shown has a first connecting seam D and a first connecting seam E with a length of 25 mm cut out of the tube wall by wire cutting. The angle between the first connecting seam D and the first connecting seam E is 90°, and they are respectively used to connect the U-shaped supporting spring piece 12 and the interdigital electrode 11 wrapped with polyester PET film. Epoxy resin glue is used for bonding during connection, so that the U-shaped supporting spring piece 12 and the interdigital electrode 11 wrapped with polyester PET film are more firmly connected to the electrode connecting tube 13.

[0046] The positioning assembly 3 provided in an embodiment of the present invention includes a base 33, a welding rod fixing device 31 and a guide rod 32; wherein, the welding rod fixing device 31 includes two symmetrical welding rod placement columns 35 installed on the base 33, and both of the welding rod placement columns 35 are provided with V-shaped grooves for placing welding rods 4, which are used to place welding rods 4 whose humidity needs to be measured; two symmetrical support columns 34 are also installed on the base 33, and reference 9 is a structural schematic diagram of the support columns 34 and the welding rod placement columns 35; there are two guide rods 32, and the two ends of one of the guide rods 32 are respectively fixed on one of the support columns 34 and one of the welding rod placement columns 35; the two ends of the other guide rod 32 are respectively fixed on the other support column 34 and the other welding rod placement column 35. Specifically, the base 33 of the embodiment of the present invention has a length of 230 mm, a width of 120 mm, and a thickness of 5 mm; the diameters of the welding rod placement column 35 and the support column 34 are both 10 mm, and the heights are both 30 mm, and a through hole with a length of 4 mm and a diameter of 4 mm is provided 25 mm away from the bottom end for inserting the guide rod 32; in addition, a 2.5 mm deep V-groove is drawn out on the welding rod placement column 35 at a distance of 25 mm from the bottom end for placing the welding rod 4; the guide rod 32 has a diameter of 8 mm and a length of 63 mm, and small cones with a diameter of φ=4 mm and a length of 4 mm are drawn out at both ends for easy insertion between the two support columns 34 and the welding rod placement column 35.

[0047] As an embodiment of the present invention, the sensor assembly 1 has four evenly spaced ones fixed on the bracket 2; the bracket 2 includes a support plate 21, an upper baffle 22 and a lower baffle 23 fixed to both sides of the support plate 21 by screws, and the support plate 21 is a 5mm thin rolled steel plate; a circular hole with a diameter of 2mm is punched in the middle of the lower end of the U-shaped support spring piece 12, which is fixedly connected to the support plate 21 by screws, and the two side walls of the U-shaped support spring piece 12 are located between the upper baffle 22 and the lower baffle 23, and the upper baffle 22 and the lower baffle 23 limit the outward elastic deformation of the two side walls of the U-shaped support spring piece 12; Figure 8 As shown, the support plate 21 includes a support bar 24 and support blocks 25 connected to both ends of the support bar 24; the support bar 24 is provided with through holes for fixing the U-shaped support spring piece 12 at two locations with a distance of 22 mm from the center and at two locations with a distance of 60 mm from the center, and the through holes have a diameter of 3 mm; the support blocks 25 at both ends are provided with a circular hole with a diameter of 11 mm for sleeve-fitting the hollow stepped shaft 26 and fixed with a nut B; the hollow stepped shaft 26 is a hollow sleeve with a total length of 20 mm, of which the 4 mm long portion is used to connect the support block 25, and the remaining 18 mm is a threaded line for tightening the nut B; refer to Figure 10It is a structural schematic diagram of the hollow stepped shaft and its connection with the guide rod and the support block. The hollow stepped shaft 26 is sleeved on the guide rod 32 and is slidingly connected to the guide rod 32, thereby realizing the sliding connection between the support plate 21 and the guide rod 32. The forked electrode 11 can move toward the direction of the welding rod 4 through the sliding of the support plate 21 on the guide rod 32, so that the forked electrode 11 is tightly fitted to the welding rod 4 to achieve measurement.

[0048] As an embodiment of the present invention, the welding rod fixing device 31 further includes a column 36 and a swing rod 37; Figure 7 3 is a schematic diagram of the structure of the connection between the column and the swing arm provided in an embodiment of the present invention. The column 36 is fixed to the base 33. The top end of the swing arm 37 is rotatably connected to one end of the connecting rod 38, and the other end of the connecting rod 38 is fixedly connected to the top end of the column 36. A spring 39 is connected to the column 36 38 mm from the lower end. The rod body of the swing arm 37 is connected to the column body of the column 36 via the spring 39. The swing arm 37 can swing toward the direction of the welding rod 4 to fix the welding rod 4 against the V-shaped groove of the welding rod placement column 35. In addition, a winding wheel 5 is fixed on the base 33, and a traction rope 51 is wound around the winding wheel 5. The traction rope 51 used in the embodiment of the present invention is a steel wire rope; the rotating shaft of the winding wheel 5 is connected to the knob 52; when the knob 52 is rotated, the rotating shaft can be driven to rotate, thereby realizing the winding and releasing operations of the traction rope 51; a pulley 53 is provided on the rocker arm 37; one end of the traction rope 51 is fixed in the winding wheel 5, and the other end moves out of the winding wheel 5, is wound around the pulley 53, and is fixed to the center position A of the support plate 21. During measurement, the welding rod 4 is placed on the V-shaped groove of the welding rod placement column 35. It is only necessary to turn the knob 52 to reel in the traction rope 51. The traction rope 51 pulls the support plate 21 toward the welding rod 4 through the pulley 53. At the same time, the pulley 53 drives the rocker arm 37 to move toward the welding rod 4. The spring 39 supports the rocker arm 37 to firmly press the welding rod 4 against the V-shaped groove. Due to the restriction of the upper baffle 22 and the lower baffle 23, the two side walls of the U-shaped support spring piece 12 cannot be elastically deformed outward, so that the forked electrode 11 is subjected to force and elastically deformed and fits completely and tightly against the outer surface of the welding rod 4, thereby completing the measurement.

[0049] As an embodiment of the present invention, Figure 11The interdigitated electrode 11 shown includes an upper electrode 14 and a lower electrode 15, wherein the upper electrode 14 and the lower electrode 15 have the same number of interdigitated joints, and the interdigitated joints of the upper electrode 14 and the lower electrode 15 are placed crosswise to form a periodic structure; both sides of the interdigitated electrode 11 are completely wrapped and fixed with a polyester PET film, and a wire is led out; it should be noted that the common materials suitable for the protective film of the interdigitated electrode 11 are alumina ceramics, polyester PET flexible materials, single crystal silicon, etc.; alumina ceramics have the characteristics of high hardness, light material and good wear resistance; single crystal silicon has significant semi-conductivity, and is hard and brittle with a metallic luster; polyester PET flexible material has high tensile strength, abrasion resistance, strong ductility, low dielectric loss, high hardness and good viscosity; due to the ductility of polyester PET flexible material The polyester PET flexible material itself has a dielectric constant of no more than 3, so the polyester PET film in the embodiment of the present invention is used as a protective film for the interdigital electrode 11; the selected polyester PET film has a thickness of 0.07 mm, a length of 25 mm, and a width of 25 mm, and is tightly attached to the interdigital electrode 11; in addition, the interdigital electrode 11 is an interdigital metal Cu material, and the overall shape is a rectangular parallelepiped with a length of 25 mm, a width of 15 mm, and a thickness of 0.013 mm. The interdigital electrode 11 is fixed at the center of the 25 mm * 25 mm polyester PET film, and the interdigital spacing between the upper electrode 14 and the lower electrode 15 is 0.2 mm, the interdigital width is 0.2 mm, the interdigital length is 7 mm, and the number of interdigital pairs is 18.

[0050] In one embodiment of the present invention, by measuring the capacitance value of the interdigital electrode 11, the relationship between the capacitance value and the dielectric constant of the medium can be derived to determine the influence relationship between the water content of the coating of the welding rod 4; Figure 11 and Figure 12 The basic interdigital electrode unit of the interdigital electrode 11 is formed by the interdigital sections of the upper electrode 14 and the lower electrode 15 being placed crosswise with each other, wherein the two adjacent interdigital sections form a pair. When voltage is applied to the upper electrode 14 and the lower electrode 15, the electric field lines will point from the positive electrode to the negative electrode. The area where the electric field mainly exists on the surface of the interdigital electrode 11 is called the electric field sensitive area. By utilizing the edge effect between its metal electrodes, the electric field lines will flow from the excitation electrode to the sensing electrode. When the welding rod 4 to be tested appears in the sensor measurement area or its physical properties change (change in dielectric constant), its electric field will change, thereby causing the capacitance value of the sensor to change; therefore, the change in the dielectric constant of the welding rod 4 coating can be converted into a change in capacitance value, thereby achieving the purpose of welding rod humidity detection.

[0051] Reference Figure 12 The diagram of the capacitance distribution between the electrodes of the interdigital electrode sensor during measurement is shown. The measurement principle is analyzed as follows: since the interdigital electrode 11 is arc-shaped during measurement, when the interdigital electrode 11 is pressed tightly, the medium between two adjacent interdigital joints is the welding rod 4 coating and the polyester PET film. The distance between the two adjacent interdigital joints is , the grounding of the sensor device does not affect the capacitance of the capacitive sensor. When the water content of the electrode coating is different, the dielectric constant of the coating will change, so the capacitance The value of will also change; when the interdigital electrode 11 is pressed tightly, the distance between the other side of the electrode increases, and the medium between the two electrodes is air, so The value of becomes smaller, but when measuring the same type of welding rod 4, the bending degree of the interdigital electrode 11 is consistent, so here and Can be regarded as a fixed value. Figure 12 It can be seen that the capacitor 、 and It is a parallel relationship, so the total inter-electrode capacitance between a pair of interdigital joints is:

[0052] (1)

[0053] In formula (1), It is the flat plate capacitance generated between a pair of interdigital joints. and They are respectively a pair of interdigitated joints, the capacitance generated by the edge effect on the material side to be tested and the base material. The calculation is relatively complex and is usually obtained using the conformal mapping method. The base material of the embodiment of the present invention is polyester PET film.

[0054] When the water content of the welding rod 4 changes, that is, the dielectric constant of the material to be measured changes, the change in capacitance value is , the total capacitance at this time is:

[0055] (2)

[0056] For the interdigital capacitive sensor, due to its unique interdigital structure, when other conditions remain unchanged, changes in the number of interdigital segments, the length of the interdigital segments, and the dielectric constant will cause changes in the capacitance value of the interdigital capacitive sensor; when the size of the interdigital electrode 11 is determined, when the relative dielectric constant in the coating of the welding rod 4 changes, the capacitance value also changes accordingly.

[0057] The present invention is to meet the needs of on-site rapid detection of commonly used welding rods 4 (diameter: 2.5 / 3.2 / 4.0mm), utilize the sensitivity of the relative dielectric constant of the welding rod 4 coating, and adopt an interdigital capacitive sensor to measure the moisture content of the welding rod coating. The moisture content can be converted from the change in the relative dielectric constant to the capacitance value of the capacitive sensor; the purpose is to ensure that the humidity of the welding rod 4 meets the welding requirements before welding, realize non-destructive detection and on-site detection of the humidity of the welding rod 4, avoid the influence of the surrounding environment on the detection results, and improve the efficiency of the detection of the moisture content of the welding rod 4. The sensor assembly provided by the embodiment of the present invention The interdigitated electrodes 11 and electrode lead wires of component 1 are effectively shielded and waterproof sealed to eliminate their influence on the measurement results, especially the influence on the material properties in the sensor component 1, to prevent the stray capacitance generated by the measuring device from affecting the detection results, and the ground lead of the measuring device is grounded; when in use, in order to prevent wear caused by close contact between the interdigitated electrodes 11 and the welding rod 4, polyester PET film is used to tightly fix both sides of the interdigitated electrodes 11, so that the interdigitated electrodes 11 are completely covered and not in contact with the air, which can effectively avoid the influence of the dielectric constant of the filler on the measurement.

[0058] To sum up, the welding rod humidity measuring device based on the forked-finger capacitive sensor provided by the embodiment of the present invention utilizes the characteristics of the flexible material of the forked-finger electrode 11 to closely fit the welding rod 4 for measurement to improve the measurement accuracy; in addition, due to the forked-finger structure characteristics of the forked-finger electrode 11, the capacitance error caused by the parallel capacitance generated by the eccentricity of the welding core of the welding rod 4 in the previous capacitive sensor is avoided. In addition, compared with the conventional sensor electrode fixed and supported by fillers, the present invention connects the forked-finger electrode 11 to the two ends of the U-shaped support spring piece 12 and places it in the air, thereby avoiding the influence of the relative dielectric constant of other fillers on the sensor detection results during the measurement process, thereby further improving the measurement accuracy; the humidity measuring device of the embodiment of the present invention winds up the wire by rotating the knob 52, driving the forked-finger electrode 11 to tightly wrap the welding rod 4, effectively solving the problem that a certain air gap will cause series capacitance. The welding rod moisture measurement device based on the interdigital capacitive sensor provided by the embodiment of the present invention can be applied to the moisture content detection of different types of welding rods 4. Its accurate measurement can realize non-destructive testing and on-site testing. It has a simple structure, is easy to integrate, is easy to carry, and has a long service life. It can be widely used in welding sites, welding rod manufacturers, welding rod storage and other testing places, and has extremely broad application prospects.

[0059] Example 2

[0060] An embodiment of the present invention provides a welding rod moisture measurement method using the welding rod moisture measurement device based on the interdigital capacitive sensor described in Example 1, the method comprising the following steps:

[0061] Step 1: grounding the welding rod moisture measurement device based on the interdigital capacitive sensor using a grounding lead to eliminate the influence of stray capacitance on the measurement;

[0062] Step 2: connecting the upper electrode 14 and the lower electrode 15 of the interdigital electrode 11 with wires to eliminate residual charges;

[0063] Step 3: Place the welding rod 4 on the V-shaped groove of the welding rod placement column 35;

[0064] Step 4: Turn the knob 52 to drive the reel 5 to reel in the traction rope 51. During the reeling process, the traction rope 51 pulls the support plate 21 toward the welding rod 4 via the pulley 53. At the same time, the pulley 53 drives the rocker 37 to firmly press the welding rod 4 against the V-shaped groove. The elasticity of the U-shaped support spring 12 causes the interdigital electrodes 11 to elastically deform until the interdigital electrodes 11 are completely and tightly attached to the outer surface of the welding rod 4. Stop turning the knob 52 and start measuring.

[0065] As an embodiment of the present invention, the capacitance of the interdigital capacitive sensor measuring the welding rod (4) is:

[0066] (3)

[0067] In formula (3), is the dielectric constant of vacuum, is the relative dielectric constant of the gap between each pair of interdigital joints, is the dielectric constant of the welding rod (4), is the dielectric constant of polyester PET film, is the width of the interknuckle, is the spacing between the gaps between each pair of interdigital joints, is the length of the interknuckle, is the thickness of the interdigital electrode (11), is the number of interdigital joints;

[0068] Step 5: Connect an external capacitance detection meter through the interdigital electrodes 11 to display the capacitance C;

[0069] Step 6: Using the national standard GB-5117 1995 measurement method, calibrate the relationship between the capacitance of the interdigital capacitive sensor and the percentage of moisture content of the welding rod 4, thereby obtaining the humidity of the welding rod 4 based on the measured capacitance C.

[0070] Among them, in step 5, the real-time transmission and data storage of the data in the external capacitance detection instrument of the interdigital electrode 11 lead specifically include: using a capacitance-to-digital converter integrated chip to detect the humidity of the welding rod 4, and the capacitance-to-digital converter integrated chip is directly connected to the upper electrode 14 and the lower electrode 15 in the sensor component 1; the microcontroller uses a single-chip microcomputer as the main control chip, analyzes and processes the collected sensor capacitance value C, and sends it to the host computer through the USB serial port conversion; the host computer program is designed using the virtual instrument development platform LabVIEW, and through the data flow driving method, the parallel execution of the program is realized to improve the execution speed of the program; the host computer receives the humidity detection data sent by the main control chip through the serial port, processes the detection data, and then sends it to the display control of the capacitance detection instrument for display.

[0071] The welding rod moisture measurement method of the welding rod moisture measurement device based on the interdigital capacitive sensor provided in the embodiment of the present invention is based on the same technical concept as the welding rod moisture measurement device based on the interdigital capacitive sensor provided in Example 1, and can produce the beneficial effects as described in Example 1. For the contents not described in detail in this embodiment, please refer to Example 1.

[0072] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A welding rod moisture measurement device based on an interdigital capacitive sensor, characterized in that: It comprises a sensor assembly (1), a bracket (2) and a positioning assembly (3); The sensor assembly (1) comprises an interdigitated electrode (11) and a U-shaped supporting spring (12), wherein both top ends of the U-shaped supporting spring (12) are provided with an electrode connecting tube (13), and the interdigitated electrode (11) is connected between the two electrode connecting tubes (13); The bracket (2) includes a support plate (21), an upper baffle (22) and a lower baffle (23) fixed on both sides of the support plate (21); the lower end of the U-shaped support spring (12) is fixedly connected to the support plate (21), and the two side walls of the U-shaped support spring (12) are located between the upper baffle (22) and the lower baffle (23), and the upper baffle (22) and the lower baffle (23) limit the outward elastic deformation of the two side walls of the U-shaped support spring (12); The positioning assembly (3) includes a welding rod fixing device (31) and a guide rod (32), the welding rod (4) is placed on the welding rod fixing device (31), and the support plate (21) is slidably connected to the guide rod (32); the forked electrode (11) can be moved toward the welding rod (4) by sliding the support plate (21) on the guide rod (32), so that the forked electrode (11) is closely attached to the welding rod (4) to achieve measurement; The outer surface of the interdigital electrode (11) is wrapped with a polyester PET film; The interdigitated electrode (11) comprises an upper electrode (14) and a lower electrode (15); the upper electrode (14) and the lower electrode (15) have the same number of interdigitated segments, and the interdigitated segments of the upper electrode (14) and the lower electrode (15) are interdigitated and arranged to form a periodic structure.

2. The welding rod moisture measuring device based on the interdigital capacitive sensor according to claim 1, characterized in that: The positioning assembly (3) includes a base (33), and two symmetrical support columns (34) are installed on the base (33); the welding rod fixing device (31) includes two symmetrical welding rod placement columns (35) installed on the base (33); there are two guide rods (32), and the two ends of one of the guide rods (32) are respectively fixed to one of the support columns (34) and one of the welding rod placement columns (35); the two ends of the other guide rod (32) are respectively fixed to the other support column (34) and the other welding rod placement column (35).

3. The welding rod moisture measuring device based on the interdigital capacitive sensor according to claim 2, characterized in that: Both welding rod placement columns (35) are provided with V-shaped grooves for placing welding rods (4).

4. The welding rod moisture measuring device based on the interdigital capacitive sensor according to claim 3, characterized in that: The support plate (21) comprises a support bar (24) and support blocks (25) connected to both ends of the support bar (24); the support block (25) is sleeved and fixed with a hollow stepped shaft (26), and the hollow stepped shaft (26) is sleeved on a guide rod (32) and slidably connected to the guide rod (32).

5. The welding rod moisture measuring device based on the interdigital capacitive sensor according to claim 4, characterized in that: The welding rod fixing device (31) further includes a column (36) and a swing rod (37); the column (36) is fixed on the base (33); the top end of the swing rod (37) is rotatably connected to one end of the connecting rod (38), and the other end of the connecting rod (38) is fixedly connected to the top end of the column (36); the rod body of the swing rod (37) is connected to the column body of the column (36) via a spring (39); the swing rod (37) can swing in the direction of the welding rod (4) to fix the welding rod (4) against the V-shaped groove of the welding rod placement column (35).

6. The welding rod moisture measuring device based on the interdigital capacitive sensor according to claim 5, characterized in that: It also includes a winding wheel (5), a traction rope (51) wound around the winding wheel (5); a rotating shaft of the winding wheel (5) is connected to a knob (52); a pulley (53) is provided on the swing rod (37); one end of the traction rope (51) is fixed in the winding wheel (5), and the other end is moved out of the winding wheel (5), wound around the pulley (53), and then fixed to the center position of the support plate (21).

7. The welding rod moisture measuring device based on the interdigital capacitive sensor according to claim 6, characterized in that: The number of the sensor components (1) is set to four, and the four sensor components (1) are fixed on the support plate (21) at even intervals.

8. A method for measuring welding rod moisture using the welding rod moisture measuring device based on an interdigital capacitive sensor according to any one of claims 6 or 7, characterized in that: The method comprises the following steps: The welding rod moisture measurement device based on the interdigital capacitive sensor is grounded using a grounding lead to eliminate the influence of stray capacitance on the measurement; connecting the upper electrode (14) and the lower electrode (15) of the interdigitated electrode (11) with a lead wire to eliminate residual charge; Placing the welding rod (4) on the V-shaped groove of the welding rod placement column (35); The knob (52) is turned to drive the winding wheel (5) to reel in the traction rope (51). During the reeling process, the traction rope (51) pulls the support plate (21) toward the welding rod (4) through the pulley (53). At the same time, the pulley (53) drives the swing rod (37) to press the welding rod (4) firmly against the V-shaped groove. The elasticity of the U-shaped supporting spring (12) is used to elastically deform the forked electrode (11) until the forked electrode (11) is completely and tightly fitted to the outer surface of the welding rod (4). The knob (52) is stopped to perform measurement. An external capacitance detection instrument is connected via the interdigital electrodes (11) to display the capacitance C; The relationship between the capacitance of the interdigitated capacitive sensor and the percentage of water content of the welding rod (4) is calibrated using the national standard GB-5117 1995 standard measurement method, thereby obtaining the humidity of the welding rod (4) based on the capacitance C obtained by measurement.

Images