A metal rod linear expansion coefficient measuring instrument

Abstract

This utility model relates to the field of linear expansion coefficient measurement technology, and discloses a metal rod linear expansion coefficient measuring instrument, including an electromagnetic induction heating temperature measuring device, a micro-displacement measuring device platform, and a main unit. The electromagnetic induction heating temperature measuring device includes an electromagnetic induction heating coil and a real-time temperature measuring sensor for the metal rod. The micro-displacement measuring device platform includes a metal shell and an insulating built-in frame, a primary coil winding, a secondary coil winding one, a secondary coil winding two, and an iron core component located inside the metal shell. This utility model combines LVDT-based micro-displacement measurement technology with electromagnetic induction heating for experimental measurement of the linear expansion coefficient of metal rods. LVDT-based micro-displacement measurement technology has the advantages of high resolution, fast dynamic response, small size, light weight, simple structure, portability, and few restrictions on the material of the measured object. Electromagnetic induction heating enables rapid heating, good temperature uniformity, and high temperature control accuracy.

Description

Technical Field

[0001] This utility model relates to the field of linear expansion coefficient measurement technology, and more specifically, to a linear expansion coefficient measuring instrument for metal rods. Background Technology

[0002] When temperature changes, solids are affected by thermal motion, and the distance between atoms changes accordingly, causing changes in the density or length of the object. Most objects exhibit this characteristic known as "thermal expansion and contraction." The phenomenon of a solid's volume increasing with increasing temperature is called thermal expansion. When a solid thermally expands, it expands in all dimensions (such as length, width, height, and diameter). We call the increase in volume volume volumetric expansion; the increase in the length of an object is called linear expansion. The physical quantity α represents the degree of linear expansion and is called the coefficient of linear expansion. Although the coefficient of linear expansion of a solid is very small, and therefore the increase or decrease in length caused by temperature changes is also small, when the two ends of a solid are fixed, causing its expansion or contraction to be hindered by temperature changes, a non-negligible stress will appear inside, usually called thermal stress. For example, the thermal stress generated in an iron object when the temperature changes by 1°C is approximately 2 × 10⁻⁶. 6 N·m -2 Therefore, in engineering, certain measures must be taken to prevent the damage caused by thermal stress. For example, steel bridges are fixed at only one end while the other end rests on rollers; a certain gap must be left at rail joints; instruments made of two different materials and tightly assembled together must use materials with similar coefficients of linear expansion, etc., all to prevent thermal stress generated when temperatures change. This must be fully considered in engineering design (such as bridge, rail, and cable engineering), precision instrument design, and the welding and processing of materials. At the same time, this characteristic is also utilized for its advantages, such as in liquid thermometers.

[0003] Since the coefficient of linear expansion is generally very small, the change in length caused by thermal expansion and contraction is also generally small. In experiments measuring the coefficient of linear expansion of materials, the key is to measure the elongation of the material after thermal expansion. This elongation is difficult to measure accurately using ordinary length measuring instruments, requiring a magnified measurement method. Commonly used magnification methods in university physics experiments include optical lever magnification and dial indicator mechanical magnification.

[0004] The main problems with using an optical lever to measure minute elongations are: First, adjusting the optical lever's scale assembly is cumbersome and affected by indoor lighting; it cannot be adjusted if the light is too strong or too weak. Second, the distance between the telescope and the optical lever is limited by the telescope's magnification, and parallax occurs during the reading process, reducing measurement accuracy. Additionally, the telescope is expensive and easily damaged.

[0005] Although dial indicators do not have complicated adjustment steps, the deflection of the dial indicator pointer directly reflects the expansion of the metal rod, and students can intuitively understand the principle of "mechanical amplification". However, the pressure and friction between the dial indicator test head and the end face of the rod under test cause the temperature rise and fall data to lag. At the same time, the test head will also press on the end face of soft metal (such as aluminum) to produce micro-indentations, which will affect the measurement results.

[0006] Meanwhile, in existing technologies, the heating methods used in experiments measuring the coefficient of linear expansion mainly include electrothermal methods and water bath methods. Electrothermal methods have a simple and compact heating structure and a relatively fast heating rate, but suffer from poor temperature uniformity and large temperature fluctuations. In contrast, water bath methods offer good temperature uniformity and high temperature control accuracy, but have a lower upper temperature limit, slower heating rate, more complex structure, require circulating water pumps and insulated pipelines, and increase the risk of leakage. Utility Model Content

[0007] In view of this, the present invention proposes a metal rod linear expansion coefficient measuring instrument, the specific technical solution of which is as follows:

[0008] A metal rod linear expansion coefficient measuring instrument includes an electromagnetic induction heating temperature measuring device, a micro-displacement measuring device platform, and a main unit;

[0009] The electromagnetic induction heating temperature measuring device includes an electromagnetic induction heating coil sleeved on the outside of the metal rod to be tested, and a real-time temperature measuring sensor of the metal rod extending into the electromagnetic induction heating coil and in direct contact with the metal rod to be tested. The electromagnetic induction heating coil is electrically connected to the main unit and performs induction heating on the metal rod to be tested. The real-time temperature measuring sensor of the metal rod is also electrically connected to the main unit. The metal rod to be tested is supported by a bracket and its left and right ends are respectively held by a fixed top rod and a movable top rod. The outer end of the movable top rod on the right side abuts against the freely movable iron core component in the micro-displacement measuring device platform.

[0010] The micro-displacement measuring device platform includes a metal shell and an insulating built-in frame, a primary coil winding, a secondary coil winding one, a secondary coil winding two, and an iron core component disposed inside the metal shell. The insulating built-in frame is fixed inside the metal shell. The primary coil winding is uniformly wound in the middle position of the insulating built-in frame. The secondary coil winding one and the secondary coil winding two are two identical coils and are symmetrically wound on the insulating built-in frame on both sides of the primary coil winding. The output voltages of the secondary coil winding one and the secondary coil winding two are connected in series in reverse. The iron core component passes through the center hole of each coil winding and can move along the axial direction. All coil windings are electrically connected to the main unit through the primary and secondary coil interface lines.

[0011] Preferably, the electromagnetic induction heating temperature measuring device includes a second metal casing and a heating coil frame disposed inside the second metal casing. Baffles are installed on both the left and right sides of the second metal casing. The heating coil frame is fixed to the inner wall of the left baffle. The electromagnetic induction heating coil is uniformly wound on the heating coil frame. Several insulating supports are installed axially at the bottom of the inner wall of the heating coil frame. The top of the insulating supports correspondingly supports the metal rod to be measured located inside the heating coil frame. The fixed top rod is fixedly connected to the inner wall of the left baffle, and the movable top rod passes through the right baffle and is slidably connected to the right baffle.

[0012] Preferably, heat-insulating pads are provided at both ends of the heating coil frame.

[0013] Preferably, the baffle is a quartz baffle, the heating coil frame is a silicon nitride ceramic frame, and the fixed top rod and the movable top rod are ceramic top rods.

[0014] Preferably, the heating coil frame is fixed to the inner wall of the left side baffle by coil frame fixing screws; a quartz base is also fixed below the second metal shell.

[0015] Preferably, the core component includes a core body located in the middle and a fiberglass rod coaxially connected to the core body. The proximal end of the fiberglass rod is connected to the end of the core body facing the electromagnetic induction heating temperature measuring device, and the distal end of the fiberglass rod extends beyond the metal outer shell and abuts against the outer end of the movable top rod. When the core body is at the center of the primary coil winding, the voltage induced by the secondary coil winding one and the secondary coil winding two is equal.

[0016] Preferably, the iron core body is rod-shaped and has high magnetic permeability.

[0017] Preferably, the micro-displacement measuring device platform further includes a platform support frame for supporting the metal outer shell and the corresponding internal structures.

[0018] Preferably, the real-time temperature measurement sensor for the metal rod is a K-type micro thermocouple.

[0019] Preferably, the host is equipped with a power supply system, a main control system, and a display system for displaying the current of the electromagnetic induction heating coil, the real-time temperature of the metal rod, and the elongation of the metal rod.

[0020] Compared to existing technologies, the advantages of this utility model's metal rod linear expansion coefficient measuring instrument are as follows: This utility model creatively combines LVDT-based micro-displacement measurement technology with electromagnetic induction heating in the experimental measurement of the linear expansion coefficient of metal rods. LVDT-based micro-displacement measurement technology features high resolution, fast dynamic response, small size, light weight, simple structure, portability, and fewer restrictions on the materials being measured. Electromagnetic induction heating results in rapid temperature rise, good temperature uniformity, and high temperature control accuracy.

[0021] This electromagnetic induction heating metal rod linear expansion coefficient measuring device based on LVDT micro-displacement measurement technology makes experimental operation more convenient, saves time in adjusting the instrument, reduces heating waiting time, greatly improves classroom efficiency, and makes experimental results more accurate. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this utility model 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 only embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0023] Figure 1 This is a three-dimensional structural diagram of a metal rod linear expansion coefficient measuring instrument according to the present invention.

[0024] Figure 2 This is a front view of a metal rod linear expansion coefficient measuring instrument according to the present invention.

[0025] Figure 3 This is a top view of a metal rod linear expansion coefficient measuring instrument according to the present invention.

[0026] Figure 4 for Figure 3 A cross-sectional view along the AA direction.

[0027] In the diagram: 1-Electromagnetic induction heating temperature measuring device; 101-Electromagnetic induction heating coil; 102-Real-time temperature measurement sensor for metal rod; 103-Fixed top rod; 104-Modible top rod; 105-Metal casing II; 106-Heating coil frame; 107-Baffle; 108-Insulating bracket; 109-Insulating pad; 110-Quartz base; 111-Coil frame fixing screw; 2-Micro displacement measuring device platform; 201-Metal casing I; 202-Primary coil winding; 203-Secondary coil winding I; 204-Secondary coil winding II; 205-Primary and secondary coil interface wires; 206-Iron core body; 207-Fiberglass rod; 208-Platform support frame; 3-Main unit; 4-Metal rod to be measured. Detailed Implementation

[0028] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this utility model, and should not be construed as limiting this utility model.

[0029] In the description of this utility model, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and 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. Therefore, they should not be construed as limitations on this utility model.

[0030] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0031] Example:

[0032] like Figures 1-4 As shown, this utility model embodiment provides a metal rod linear expansion coefficient measuring instrument based on LVDT electromagnetic induction heating. The metal rod linear expansion coefficient measuring instrument mainly includes an electromagnetic induction heating temperature measuring device 1, a micro-displacement measuring device platform 2, and a host 3.

[0033] The electromagnetic induction heating temperature measuring device 1 includes an electromagnetic induction heating coil 101 sleeved on the outside of the metal rod 4 to be tested, and a metal rod temperature real-time measuring sensor 102 extending into the electromagnetic induction heating coil 101 and in direct contact with the metal rod 4 to be tested. The electromagnetic induction heating coil 101 is electrically connected to the host 3 and performs induction heating on the metal rod 4 to be tested. The metal rod temperature real-time measuring sensor 102 is also electrically connected to the host 3. The metal rod 4 to be tested is supported by a bracket and its left and right ends are respectively held by a fixed top rod 103 and a movable top rod 104. The outer end of the movable top rod 104 on the right side abuts against the freely movable iron core component in the micro-displacement measuring device platform 2.

[0034] In specific embodiments, such as Figure 4 As shown, the tips of the fixed push rod 103 and the movable push rod 104 are respectively abutted against the center of the corresponding end of the metal rod 4 to be tested.

[0035] The micro-displacement measuring device platform 2 includes a metal shell 201 and an insulating built-in frame, a primary coil winding 202, a secondary coil winding 203, a secondary coil winding 204, and an iron core component located inside the metal shell 201. The insulating built-in frame is fixed inside the metal shell 201. The primary coil winding 202 is evenly wound in the middle position of the insulating built-in frame. The secondary coil winding 203 and the secondary coil winding 204 are two identical coils and are symmetrically wound on the insulating built-in frame on both sides of the primary coil winding. The output voltages of the secondary coil winding 203 and the secondary coil winding 204 are connected in series in reverse. The iron core component passes through the center hole of each coil winding and can move along the axial direction. All coil windings are electrically connected to the main unit 3 through the primary and secondary coil interface lines 205.

[0036] The metal casing 201 in the micro-displacement measuring device platform 2 is used to protect the internal coil and iron core components, while shielding against external electromagnetic interference.

[0037] In a further specific embodiment, the electromagnetic induction heating temperature measuring device 1 includes a metal outer shell 105 and a heating coil frame 106 disposed inside the metal outer shell 105. Baffles 107 are installed on both the left and right sides of the metal outer shell 105. The heating coil frame 106 is fixed to the inner wall of the left baffle. The electromagnetic induction heating coil 101 is evenly wound on the heating coil frame 106. Several insulating supports 108 are installed axially at the bottom of the inner wall of the heating coil frame 106. The top of the insulating supports 108 supports the metal rod 4 to be measured located inside the heating coil frame 106. The fixed top rod 103 is fixedly connected to the inner wall of the left baffle, and the movable top rod 104 passes through the right baffle 107 and is slidably connected to the right baffle.

[0038] The metal outer casing 105 in the electromagnetic induction heating temperature measuring device 1 is used to protect the internal coil and metal rod, and at the same time shield external electromagnetic interference.

[0039] Meanwhile, to further optimize the solution, this embodiment also provides heat insulation pads 109 at both ends of the heating coil frame 106. The function of the heat insulation pads is to keep the temperature warm. If the heat insulation pads are not provided, when the metal rod 4 under test is heated, the heat inside it will be transferred outward along the metal outer shell 105 of the heating coil frame 106, which may affect the temperature control of the metal rod 4 under test.

[0040] Furthermore, the baffle 107 is preferably a quartz baffle, the heating coil frame 106 is preferably a silicon nitride ceramic frame, and the fixed push rod 103 and the movable push rod 104 are preferably ceramic push rods.

[0041] In a further specific embodiment, the heating coil frame 106 is fixed to the inner wall of the left side baffle by the coil frame fixing screw 111.

[0042] In this embodiment, the core component includes a core body 206 located in the middle and a glass fiber rod 207 coaxially connected to the core body 206. The core body 206 is rod-shaped and has high magnetic permeability. The core body 206 is preferably a permalloy rod. The proximal end of the glass fiber rod 207 is connected to the end of the core body facing the electromagnetic induction heating temperature measuring device. The distal end of the glass fiber rod 207 extends beyond the metal outer shell 201 and abuts against the outer end of the movable top rod 104. When the core body 206 is at the center of the primary coil winding 202, the voltage induced by the secondary coil winding 203 and the secondary coil winding 204 is equal.

[0043] In a further specific embodiment, a quartz base 110 is fixed below the metal outer shell 2 105. The micro-displacement measuring device platform 2 also includes a platform support frame 208 for supporting the metal outer shell 201 and the corresponding internal structures. This ensures that the distal end of the fiberglass rod 207 and the outer end of the movable top rod 104 can be matched and abutted at the same height, and also ensures the stable placement of the electromagnetic induction heating temperature measuring device 1 and the micro-displacement measuring device platform 2.

[0044] In a further specific embodiment, the real-time temperature measurement sensor 102 of the metal rod is a K-type micro thermocouple. The K-type micro thermocouple has the advantages of small size, fast response, wide measurement range, high accuracy, good stability, low cost and strong versatility, and can better reflect the real-time temperature of the metal rod 4 under test.

[0045] In this embodiment, the main unit 3 is equipped with a power supply system, a central control system, and a display system for displaying the current of the electromagnetic induction heating coil, the real-time temperature of the metal rod, and the elongation of the metal rod. The power supply system provides appropriate current to each coil through the central control system. Meanwhile, the main unit 3 may also be equipped with components such as a power switch and power indicator lights.

[0046] The working principle of the measuring instrument for measuring the coefficient of linear expansion in this embodiment is as follows:

[0047] The increase in length of a solid after being heated is called linear expansion. Let l o Let l be the length of the object at 0℃. Then the length l of the object at t℃ is:

[0048] l = l o (1+αt)

[0049] α is the coefficient of linear expansion of the object, which is a constant when the temperature change is small. The above formula can be written as: Therefore, the physical meaning of α is that for every 1℃ increase in temperature, the growth of the object Δl = ll o The ratio of its length to its length at 0°C.

[0050] Assume l o Let l be the length of the object at temperature 0℃. Let l1 be the length of the object at room temperature t1, and l2 be the length at temperature t2. From this, we can obtain:

[0051]

[0052] From the formula, we get: Because l1 and l2 are very close, but Therefore, the value of α can be obtained as long as Δl, Δt, and l1 are measured.

[0053] Firstly, the electromagnetic induction heating temperature measuring device in this embodiment heats the solid bar (i.e., the metal rod to be tested) based on the principle of electromagnetic induction. When a high-frequency current passes through the electromagnetic induction heating coil, an alternating magnetic field is generated around the coil. When the solid bar is placed in this magnetic field, eddy currents are generated inside the bar due to electromagnetic induction. According to Joule's law, these eddy currents generate heat under the influence of the bar's own resistance, causing the bar to heat up rapidly.

[0054] Compared to electrothermal and water bath methods, the unique advantage of this electromagnetic induction heating method in this embodiment is:

[0055] (1) Rapid heating: Electromagnetic induction heating has an extremely fast heating speed, even heating metal bars within 1 second. This rapid heating capability has significant advantages over traditional heating methods (such as flame heating, resistance heating, etc.). Rapid heating can make the entire experimental process more compact and reduce waiting time.

[0056] (2) Uniform heating: Electromagnetic induction heating ensures uniform temperature in the heating area of ​​solid bars. Since the alternating magnetic field is generated around the bar, the eddy currents generated inside the bar are relatively uniformly distributed, and heat is generated uniformly inside the bar. Uneven heating may lead to uneven stress distribution inside the material, thereby causing problems such as deformation and cracking, while uniform heating can effectively avoid these situations.

[0057] (3) Precise control: Electromagnetic induction heating can precisely control heating parameters, such as heating temperature, heating time, and frequency. By adjusting these parameters using the central control system, the heating process can be precisely controlled according to the material, size, and specific heat treatment requirements of the solid bar stock.

[0058] Secondly, the micro-displacement measurement device platform in this embodiment adopts micro-displacement measurement technology based on LVDT.

[0059] LVDT refers to a linear variable differential transformer, belonging to the category of linear displacement sensors. It mainly consists of three coil windings (including a primary coil winding, secondary coil winding one, and secondary coil winding two) wound on an insulated internal frame, a freely movable rod-shaped high-permeability iron core, and a metal casing. The two secondary coil windings have opposite winding directions, the same number of turns, and are connected in series. An alternating voltage signal is applied to the primary coil winding, causing it to generate an alternating magnetic field. When the iron core moves to the middle position within the entire measurement range, the two secondary coil windings will generate induced electromotive forces of the same magnitude but opposite directions, resulting in zero output voltage across the secondary coils. When the rod-shaped iron core moves left or right and is not at the center position, the two secondary coils will generate unequal induced electromotive forces, resulting in a voltage output across the secondary coils. The magnitude of this output voltage is determined by the amount of displacement of the iron core from the center position, and the two exhibit a linear relationship; that is, the output voltage across the secondary coils is linearly proportional to the displacement of the iron core from the center position. After calibrating the LVDT system, the displacement of the object can be obtained from the measured voltage. Based on the measured Δl, and then based on Δt and l1, the linear expansion coefficient α of the metal rod under test can be calculated.

[0060] This invention combines LVDT-based micro-displacement measurement technology with electromagnetic induction heating for the experimental measurement of the linear expansion coefficient of metal rods. LVDT-based micro-displacement measurement technology features high resolution, fast dynamic response, small size, light weight, simple structure, portability, and few limitations on the materials being measured. Electromagnetic induction heating enables rapid temperature rise, good temperature uniformity, and high temperature control accuracy.

[0061] This electromagnetic induction heating metal rod linear expansion coefficient measuring device based on LVDT micro-displacement measurement technology makes experimental operation more convenient, saves time in adjusting the instrument, reduces heating waiting time, greatly improves classroom efficiency, and makes experimental results more accurate.

[0062] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0063] The above description of the disclosed embodiments enables those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A metal rod linear expansion coefficient measuring instrument, characterized by, Includes an electromagnetic induction heating temperature measuring device, a micro-displacement measuring device platform, and a main unit; The electromagnetic induction heating temperature measuring device includes an electromagnetic induction heating coil sleeved on the outside of the metal rod to be tested, and a real-time temperature measuring sensor of the metal rod extending into the electromagnetic induction heating coil and in direct contact with the metal rod to be tested. The electromagnetic induction heating coil is electrically connected to the main unit and performs induction heating on the metal rod to be tested. The real-time temperature measuring sensor of the metal rod is also electrically connected to the main unit. The metal rod to be tested is supported by a bracket and its left and right ends are respectively held by a fixed top rod and a movable top rod. The outer end of the movable top rod on the right side abuts against the freely movable iron core component in the micro-displacement measuring device platform. The micro-displacement measuring device platform includes a metal shell and an insulating built-in frame, a primary coil winding, a secondary coil winding one, a secondary coil winding two, and an iron core component disposed inside the metal shell. The insulating built-in frame is fixed inside the metal shell. The primary coil winding is uniformly wound in the middle position of the insulating built-in frame. The secondary coil winding one and the secondary coil winding two are two identical coils and are symmetrically wound on the insulating built-in frame on both sides of the primary coil winding. The output voltages of the secondary coil winding one and the secondary coil winding two are connected in series in reverse. The iron core component passes through the center hole of each coil winding and can move along the axial direction. All coil windings are electrically connected to the main unit through the primary and secondary coil interface lines.

2. The metal rod linear expansion coefficient measuring instrument according to claim 1, characterized in that, The electromagnetic induction heating temperature measuring device includes a second metal casing and a heating coil frame disposed inside the second metal casing. Baffles are installed on both the left and right sides of the second metal casing. The heating coil frame is fixed to the inner wall of the left baffle. The electromagnetic induction heating coil is evenly wound on the heating coil frame. Several insulating supports are installed axially at the bottom of the inner wall of the heating coil frame. The top of the insulating supports correspondingly supports the metal rod to be measured located inside the heating coil frame. The fixed top rod is fixedly connected to the inner wall of the left baffle, and the movable top rod passes through the right baffle and is slidably connected to the right baffle.

3. The metal rod linear expansion coefficient measuring instrument according to claim 2, wherein Insulating pads are provided at both ends of the heating coil frame.

4. The metal rod linear expansion coefficient measuring instrument according to claim 2, characterized in that, The baffle is a quartz baffle, the heating coil frame is a silicon nitride ceramic frame, and the fixed top rod and the movable top rod are ceramic top rods.

5. The metal rod linear expansion coefficient measuring instrument according to claim 2, characterized in that, The heating coil frame is fixed to the inner wall of the left side baffle by coil frame fixing screws; a quartz base is also fixed below the second metal shell.

6. The metal rod linear expansion coefficient measuring instrument according to claim 1, characterized in that, The core component includes a core body located in the middle and a fiberglass rod coaxially connected to the core body. The proximal end of the fiberglass rod is connected to the end of the core body facing the electromagnetic induction heating temperature measuring device, and the distal end of the fiberglass rod extends beyond the metal outer shell and abuts against the outer end of the movable top rod. When the core body is at the center of the primary coil winding, the voltage induced in the secondary coil winding one and the secondary coil winding two is equal.

7. The metal rod linear expansion coefficient measuring instrument according to claim 6, characterized in that, The iron core body is rod-shaped and has high magnetic permeability.

8. The metal rod linear expansion coefficient measuring instrument according to claim 1, characterized in that, The micro-displacement measuring device platform also includes a platform support frame for supporting the metal outer shell and the corresponding internal structures.

9. A metal rod linear expansion coefficient measuring instrument according to claim 1, characterized in that, The real-time temperature measurement sensor for the metal rod is a K-type micro thermocouple.

10. A metal rod linear expansion coefficient measuring instrument according to claim 1, characterized in that, The host is equipped with a power supply system, a central control system, and a display system for displaying the current of the electromagnetic induction heating coil, the real-time temperature of the metal rod, and the elongation of the metal rod.

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