A high-sensitivity thermocouple

Abstract

The present invention discloses a highly sensitive thermocouple comprising a bare wire protruding from the thermocouple insulation layer. The front end of the bare wire is flattened, leaving a transition section with a gradually changing cross-section between the flattened portion and the unflattened bare wire. The flattened portion is provided with a temperature measuring section. The temperature measuring sections of the positive and negative poles of the thermocouple are overlapped, and the contact surfaces are welded and fused. The present invention has high accuracy, can precisely adjust sensitivity, has good measurement sensitivity consistency, and is not prone to breakage.

Description

Technical Field

[0001] The invention belongs to the technical field of temperature measuring elements and relates to a high-sensitivity thermocouple. Background Art

[0002] At present, when thermocouples are used for temperature measurement in environments with rapid temperature changes, ultra-thin thermocouples with a diameter of less than 0.1 mm are usually selected to improve the sensitivity of the thermocouples.

[0003] In the process of realizing the present invention, the inventors found that the installation method of the prior art has the following problems: (1) The thermocouple wire is too thin and is easily subjected to stress during packaging or use, causing the wire cross-section to deform, resulting in errors or even breakage; (2) The sensitivity of the thermocouple wire cannot be accurately adjusted by simply controlling the diameter of the metal wire, and in response to different sensitivity requirements, a variety of thermocouples with different diameters need to be prepared, resulting in a large number of spare parts; (3) The currently commonly used thermocouple welding method cannot accurately control the size of the weld point and the welding area when the weld point is melted and balled, resulting in large individual differences among the same type of thermocouples, affecting the consistency of the measurement sensitivity. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a high-sensitivity thermocouple with high precision, the ability to accurately adjust sensitivity, good measurement sensitivity consistency, and not easy to break, thereby solving the problems existing in the prior art.

[0005] The technical solution adopted by the present invention is a high-sensitivity thermocouple, including a bare wire that leaks out of the thermocouple insulation layer, the front end of the bare wire is flattened, and a transition section with a gradually changing cross-section is left between the flattened part and the unflattened bare wire. The flattened part is provided with a temperature measuring section, the temperature measuring sections of the positive and negative poles of the thermocouple are placed overlapping, and the contact surfaces are welded and fused.

[0006] Furthermore, a low dissipation section is provided between the temperature measuring section and the transition section of the flattened portion, and an opening or a notch is provided on the low dissipation section.

[0007] Furthermore, a deformation buffer structure is provided on the low dissipation section.

[0008] Furthermore, the deformation buffer structure is a curved U-shaped or S-shaped structure.

[0009] Furthermore, the diameter of the unflattened bare wire is 0.2 mm to 2 mm.

[0010] Furthermore, the temperature measuring section is cylindrical.

[0011] Furthermore, the temperature measuring section is a flat strip with a twisted center.

[0012] Furthermore, the temperature measuring section is flat and radial.

[0013] Furthermore, a flat ring is provided in the middle of the positive and negative temperature measuring sections, and an outward extending section is provided on the circumference of the ring, and the width of the extending section is smaller than the diameter of the ring.

[0014] Furthermore, the completely overlapping area of ​​the positive and negative temperature measuring sections is not less than 40% of the total area, and the actual welding area is not less than 50% of the completely overlapping area.

[0015] The beneficial effects of the present invention are:

[0016] (1) The response time of the thermocouple of the present invention is uncorrelated with the wire diameter, enabling the use of thermocouples with larger wire diameters, thereby reducing the number of stock materials in stock. In addition, the thermocouple wire has a large diameter, a strong load-bearing capacity, is not easily deformed or deteriorated by oxidation and corrosion, and has better durability.

[0017] (2) The present invention can maintain the thickness and welding degree of thermocouples of the same size in the temperature measurement area with high precision through shaping and quantitative welding, thereby greatly reducing the response time difference between different thermocouples and improving measurement stability and consistency.

[0018] (3) The low dissipation section of the present invention can greatly reduce the minimum response heat, and the deformation buffer structure can effectively prevent the head temperature measurement section from being stressed due to the installation movement or high-temperature deformation of the rear section of the thermocouple, thereby ensuring measurement accuracy.

[0019] (4) The present invention can effectively improve the consistency of measurement parameters of thermocouples of the same type by precisely controlling the welding points of the thermocouples. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 This is a structural diagram of Example 1 of the present invention.

[0022] Figure 2 This is a structural diagram of Example 2 of the present invention.

[0023] Figure 3 This is a structural diagram of Example 3 of the present invention.

[0024] In the figure, 01. Double-layer sheath section, 02. Single-layer sheath section, 03. Bare wire, 04. Transition section, 05. Low dissipation section, 051. Deformation buffer structure, 052. Opening, 06. Temperature measurement section. DETAILED DESCRIPTION

[0025] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] Example 1,

[0027] A high-sensitivity thermocouple, such as Figure 1 As shown, it includes a bare wire 03 that leaks out of the insulation layer of the thermocouple, the front end of the bare wire 03 is flattened, and a transition section 04 with a gradual cross-section is left between the flattened part and the unflattened bare wire 03. The flattened part is provided with a temperature measuring section 06, and the temperature measuring sections 06 of the positive and negative poles of the thermocouple are overlapped and the contact surfaces are welded and fused.

[0028] In some embodiments, the insulation layer of the single-layer sheath section 02 at the front end of the double-layer sheath section 01 of the thermocouple is removed to expose the bare wire 03, and the exposed bare wire 03 at the front end is flattened into a foil strip by a sheet press, and a transition section 04 with a gradual cross-section is retained between the cylindrical bare wire 03 and the foil strip to prevent the occurrence of stress concentration points; the flattened foil strip is cut and shaped by a die-cutting machine or a laser to obtain a low dissipation section 05 and a temperature measuring section 06; the temperature measuring sections 06 of the positive and negative poles of the thermocouple are overlapped and placed, and the overlapping area of ​​the temperature measuring section 06 is welded using a high-energy welding method with precisely controllable energy (such as resistance welding, laser welding or electron beam welding, etc.), and the welding energy is controlled to fuse the contact surfaces of the positive and negative poles, and it is strictly avoided that the metal foil area melts and forms balls due to excessive energy.

[0029] Finally, the low dissipation section 05 and the temperature measurement section 06 are shaped according to the usage of the thermocouple, and are packaged as a whole when necessary to make them more suitable for different temperature measurement requirements.

[0030] The diameter of the unflattened bare wire 03 is 0.2 mm to 2 mm; in some embodiments, the diameter is not less than 0.254 mm, that is, an AWG30 thermocouple.

[0031] In some embodiments, the thickness of the flattened foil strip is determined according to the measurement conditions to ensure that the surface area to volume ratio of the final temperature measuring section 06 after welding meets the requirements of the corresponding temperature measurement time and the corresponding heat. For fast temperature measurement with a measurement response time of less than 0.2ms, the foil strip thickness should be controlled below 0.1mm; for trace gases. When measuring liquid temperature, it is necessary to first calculate the overall heat content based on the flow rate, response time, specific heat capacity, and estimated temperature of the gas or liquid, and then calculate the mass of the temperature measuring section 06 corresponding to the specific heat capacity of the thermocouple and the estimated temperature change. Finally, according to the gas flow field and flow rate at the temperature measurement point, a suitable shape of the temperature measuring section 06 is designed to ensure that the temperature measuring section 06 can exchange heat with the gas or liquid with sufficient heat within the required response time, thereby achieving effective temperature measurement within the specified response time.

[0032] In some embodiments, the low dissipation section 05 is provided with an opening 052 or a notch to reduce the cross-sectional area of ​​the foil strip in this region, thereby reducing heat loss.

[0033] In some embodiments, a deformation buffer structure 051 is provided on the low-dissipation section 05 to prevent the temperature measuring section 06 from being subjected to stress, resulting in changes in the conductive cross-section and errors or breakage. The deformation buffer structure 051 is a curved U-shaped or S-shaped structure with low rigidity and a reserve for elongation and deformation. When the temperature measuring section 06 is subjected to stress, it deforms before the temperature measuring section 06, thereby protecting the shape of the temperature measuring section 06 from deformation due to stress. If the bare wire 03 is misaligned or torsionally deformed during the installation or use of the thermocouple, the relative displacement of the thicker positive and negative electrodes will not cause deformation of the temperature measuring section 06 or even cracking of the weld area.

[0034] The temperature measuring section 06 of the embodiment of the present invention can be designed according to the response time and minimum response heat requirements. The overall package needs to be insulated according to the thermocouple installation requirements, and the exposed metal wire (all exposed metal parts) at the front end must be insulated.

[0035] In some embodiments, the temperature measuring section 06 is cylindrical. The manufacturing process involves cutting the flattened foil strip into a T-shape at its end and rolling the two symmetrical extensions of the T into a cylindrical shape. This maximizes the surface area to volume ratio, thereby increasing temperature measurement sensitivity. The device is suitable for measuring pulsed gas or liquid temperatures.

[0036] Example 2,

[0037] like Figure 2 As shown, the temperature measuring section 06 is a flat strip with a central twist in a spiral shape. This ensures that the flow area is not affected by the installation angle and effectively controls the end force. It is suitable for measuring the temperature uniformity of gas or liquid flow fields. High-temperature insulating paint or an insulating sheet is applied between the positive and negative electrodes of the low-dissipation section 05 to prevent short circuits.

[0038] Example 3,

[0039] like Figure 3 As shown, the temperature measuring section 06 is a flat radial shape, that is, a shape radiating from the center to the surroundings, using the least amount of material to occupy as much area as possible.

[0040] In some embodiments, each temperature measuring segment 06 has a flat ring in the middle, with an outward extension around the ring's circumference. The extension's width is smaller than the ring's diameter. This increases the sensing and bonding area while reducing the mass and bending stiffness of the temperature measuring segment 06, preventing warping and debonding. Suitable for measuring the surface temperature of high-temperature objects, the positive and negative electrodes of the low-dissipation segment 05 are separated by ceramic fiber cloth or glass fiber cloth, which is then applied with a high-temperature adhesive to enhance insulation and bonding.

[0041] In Examples 1-3, the completely overlapping areas of the positive and negative temperature measuring sections 06 are not less than 40% of the total area, and the actual welding area is not less than 50% of the completely overlapping area, thereby ensuring the effectiveness and reliability of temperature measurement by the temperature measuring section 06.

[0042] Existing thermocouple welding uses a stored-energy welding method, which uses a momentary high current to melt the contact points of the thermocouple's positive and negative electrodes. The welding time is very short, and the inability to precisely control the contact point state makes it difficult to accurately and quantitatively control the arc state. Therefore, the weld size and welding area cannot be accurately controlled.

[0043] In the embodiment of the present invention, the overlapping area of ​​the positive and negative electrode foil strips that have been flattened and shaped can be accurately adjusted with the help of a microscope or a camera, and the area size of the welding point can be finely controlled with a thinner laser beam. Therefore, the external dimensions, volume, and mass of the temperature measuring section 06 can be accurately controlled, thereby controlling the response time, sensitivity, and improving consistency.

[0044] When measuring the cross-sectional temperature distribution of a low-speed, vortex-bearing air flow field at a flow rate of approximately 1 m / s at normal pressure within a duct, and requiring a temperature measurement response time of no more than 0.2 s, the K-type thermocouple temperature measurement section 06 of Example 2, with an expanded size of 4 mm by 4 mm and a thickness of 0.05 mm, can be inserted from the sidewall of the ventilation duct in the hemisphere for measurement. Alternatively, the K-type thermocouple temperature measurement section of Example 1, with an expanded size of 8 mm long, 2 mm high, and 0.05 mm thick, can be inserted from the sidewall of the ventilation duct in the perpendicular direction for measurement. Example 3 requires adhesive fixation to control the consistency of the thermocouple itself, while the consistency of ordinary thermocouples is largely dependent on the individual's welding skills.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention are included in the scope of protection of the present invention.

Claims

1. A high-sensitivity thermocouple, characterized in that: The invention comprises a bare wire (03) leaking out of the insulation layer of the thermocouple, the front end of the bare wire (03) is flattened, a transition section (04) with a gradual cross-section is left between the flattened part and the unflattened bare wire (03), the flattened part is provided with a temperature measuring section (06), the flattened foil strip is cut and shaped by a die-cutting machine or a laser to obtain a low dissipation section (05) and a temperature measuring section (06); the temperature measuring sections (06) of the positive and negative poles of the thermocouple are overlapped and placed, and the overlapping area of ​​the temperature measuring sections (06) is welded using a high-energy welding method with precisely controllable energy, the welding energy is controlled to fuse the contact surfaces of the positive and negative poles, and the metal foil area is strictly prevented from melting and balling due to excessive energy, and the high-energy welding method is resistance welding, laser welding or electron beam welding; A low dissipation section (05) is provided between the temperature measuring section (06) and the transition section (04) of the flattened portion, and an opening (052) or a notch is provided on the low dissipation section (05); The low dissipation section (05) is provided with a deformation buffer structure (051); The deformation buffer structure (051) is a curved U-shaped or S-shaped structure; The temperature measuring section (06) is cylindrical, or the temperature measuring section (06) is a flat strip with a twisted center; or the temperature measuring section (06) is a flat radial shape; The area of ​​the positive and negative temperature measuring sections (06) completely overlapping is not less than 40% of the total area, and the actual welding area is not less than 50% of the area of ​​the completely overlapping area.

2. A high-sensitivity thermocouple according to claim 1, characterized in that: The unflattened bare wire (03) has a wire diameter of 0.2 mm to 2 mm.

3. A high-sensitivity thermocouple according to claim 1, characterized in that: A flat ring is provided in the middle of the positive and negative temperature measuring sections (06), and an outward extending section is provided on the circumference of the ring, and the width of the extending section is smaller than the diameter of the ring.

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