Method for manufacturing an embedded armored platinum resistance heater

Abstract

This invention discloses a method for preparing an embedded armored platinum resistance thermometer, specifically relating to the fields of resistance temperature measurement and platinum resistance temperature sensor manufacturing. The method includes steps such as Pt100 four-wire connection, assembly of copper tube and 316L protective tube, MgO filling and locking, release section pulling and staged diameter reduction, step response determination, encapsulation and moisture removal, and vibration aging. By first reducing the diameter of the Pt100 and the brazed connection area to form an MgO locking section, and then having the release section bear the length change caused by axial pulling, the local densification endpoint is determined by the step response change of Pt100 in adjacent diameter reduction stages. This ensures that the embedded Pt100 position does not move synchronously with the release section stretching, and the local MgO compaction degree and actual heat transfer state are jointly determined during the preparation process. This alleviates the problem of difficulty in simultaneously considering the repeated stress on the connection position and the temperature response state under continuous vibration conditions in intelligent sensing systems.

Description

Technical Field

[0001] This invention relates to the field of resistance temperature measurement and platinum resistance temperature sensor manufacturing technology, and more specifically, to a method for preparing an embedded armored platinum resistance thermometer. Background Technology

[0002] In the field of sensitive element and sensor manufacturing, Pt100 platinum resistance thermometers are usually used as front-end sensitive elements for intelligent sensing systems to obtain temperature information of the measured object. Their preparation generally involves first completing the electrical connection between Pt100 and the lead wire, then installing the temperature sensing component into a metal protective sleeve, and filling the space between Pt100, the lead wire and the protective sleeve with magnesium oxide, so that magnesium oxide can simultaneously undertake the functions of electrical insulation, heat transfer and internal support. For applications involving nuclear power main pumps, ship propulsion equipment, and other environments with continuous vibration and mechanical shock, relying solely on conventional end arrangements and magnesium oxide filling can easily cause Pt100 and its connection points to be in the vibration load transmission path for extended periods. Therefore, it is usually necessary to set a certain distance between Pt100 and the inside of the protective sleeve and further increase the compaction degree of magnesium oxide to reduce the space for displacement of Pt100, leads, and connection points relative to the protective sleeve. With the embedded structure, Pt100 can avoid the direct stress area at the end of the protective sleeve. However, its manufacturing process also introduces new constraints: during the multi-pass rotary forging process after magnesium oxide filling, the protective sleeve gradually shrinks radially, and the magnesium oxide particles are rearranged and change from a loose filling state to a compacted state. Pt100 and its leads also gradually change from the initial positioning state to a locked state constrained by the surrounding magnesium oxide. Subsequently, during axial drawing, the protective sleeve undergoes plastic extension in the length direction, so that the position of Pt100 relative to the measuring end, the local compaction degree of the surrounding magnesium oxide, and the actual heat transfer path of external temperature to Pt100 are simultaneously affected by the previous rotary forging state and the subsequent drawing deformation. Therefore, even if the machining is completed according to the specified number of forging passes, single-pass compression amount and drawing elongation amount, and the external dimensions meet the design requirements, it cannot be directly determined that a suitable local support and heat transfer state has been formed near Pt100. If the magnesium oxide around Pt100 is not compacted enough, the lead wires may move slightly due to continuous vibration during the long-term operation of the intelligent sensing system, the connection position may be subjected to repeated stress, or the resistance value may change after vibration. If the fixation is strengthened by continuing to reduce the diameter or increasing the local compaction, the heat transfer conditions between Pt100 and the measuring end may be changed, so that the platinum resistance thermometer that meets the requirements of the external dimensions, insulation performance and on / off state may still show temperature response differences. The existing manufacturing process usually judges the finished product status through insulation, precision, thermal response and vibration tests after the product is packaged. At this time, it can only identify whether the final result meets the requirements. It is difficult to determine at which processing stage the embedded position, local locking state and heat transfer state of Pt100 begin to deviate. It is also difficult to determine whether it is still necessary to continue the subsequent rotary forging and drawing. Therefore, in the process of preparing embedded armored platinum resistance thermometers for intelligent sensing systems, it is necessary to simultaneously address the relationship between maintaining the embedded position of Pt100, forming local support for magnesium oxide, and stabilizing the temperature transfer path. The technical problem to be solved by this application is: on the basis of maintaining the structure of Pt100 embedded in the metal and covered by magnesium oxide, how to make the final embedded position of Pt100, the mechanical locking state and the temperature transmission state around it be formed in a coordinated manner during the multi-pass rotary forging and drawing process, so that the platinum resistance thermometer can maintain a stable electrical connection while maintaining stable temperature response performance under the continuous vibration environment of the intelligent sensing system. Summary of the Invention

[0003] To overcome the aforementioned deficiencies of the prior art, embodiments of the present invention provide a method for preparing an embedded armored platinum resistance thermometer. This method involves first reducing the diameter to form an MgO locking section during the manufacturing process of the sensitive element and sensor, then having the release section bear the axial pull-out deformation. The local diameter reduction endpoint is determined based on the step response change of Pt100, enabling the Pt100 embedded position, mechanical locking state, and temperature transfer state to be coordinated. This satisfies the requirements of intelligent sensing systems for the electrical connection and temperature response stability of the platinum resistance thermometer under continuous vibration environments, thereby solving the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing an embedded armored platinum resistance thermometer, comprising: S1. Connect the Pt100 platinum film resistor to four copper core wires. Insert the copper tube into the 316L stainless steel protective tube, so that the front end of the copper tube contacts the inner wall of the measuring end of the protective tube. Insert the Pt100 into the copper tube and make its end face facing the measuring end 5-10mm away from the inner wall of the measuring end. S2. Keep the axial position of Pt100, pour MgO into the terminal, reduce the diameter of the pipe section covering Pt100 and the connection area first, so that MgO presses Pt100 and copper core wire and adheres to the inner wall of copper pipe to form a locking section, and retain the release section in the locking section towards the terminal. S3. Fix the locking section, pull the release section axially and reduce the diameter in stages to maintain a 5-10mm axial embedment distance of Pt100, and compress the MgO radial heat transfer layer between Pt100 and the inner wall of the copper tube, so that the heat received by the measuring end enters Pt100 through the protective tube, copper tube and MgO radial heat transfer layer. S4. After each stage of diameter reduction, apply the same step temperature to the measuring end three times, and read the time required for Pt100 to reach a step change of 63.2% using four lines. After sorting the three times, take the difference between the first and last stages as the stage repeatability difference and the middle value as the stage response time. Stop the diameter reduction of the pipe section where Pt100 is located when the difference between the response times of two adjacent stages does not exceed the sum of the two stage repeatability differences; otherwise, continue the diameter reduction. S5. Reduce the diameter of the remaining pipe sections to φ6, complete the sealing of the measuring end, insulation sealing of the wiring end, moisture removal and vibration aging, and re-measure the four-wire resistance, insulation resistance and response time to obtain the embedded armored platinum resistance thermometer.

[0005] In a preferred embodiment, in S1, two copper core wires are connected to the two electrodes of the Pt100 platinum thin film resistor, and a four-wire Pt100 component is formed by brazing with Ag25Cu75 silver-copper alloy. The silver mass fraction is 23%-27%, the brazing temperature is 800-850℃, the holding time is 10-30s, and the protective gas is argon or nitrogen. After brazing and natural cooling, the Pt100 is placed in a 0℃ constant temperature bath and the reference resistance is read and recorded as the initial reference resistance using a four-wire method. The MgO is a 200-260 mesh mixed powder, which is kept at 120℃ for 2 hours before filling.

[0006] In a preferred embodiment, in S1, an axial positioning structure consisting of an end face stop, an axial guide rail, and a lead wire clamp is used to maintain the embedded position of Pt100. The end face stop abuts against the outer end face of the measuring end of the 316L stainless steel protective tube. The lead wire clamp moves along the axial guide rail and clamps four copper core wires. The wall thickness of the measuring end of the 316L stainless steel protective tube and the axial length from the end face of Pt100 facing the measuring end to the clamping position of the copper core wires are obtained. The axial distance between the end face stop and the lead wire clamp is determined by the sum of the wall thickness of the measuring end, the axial length, and the 5-10mm embedded distance. After the axial distance is reached, the lead wire clamp is fixed so that the end face of Pt100 facing the measuring end is located at a position 5-10mm away from the inner wall of the measuring end. In S2, the end face of Pt100 facing the measuring end is taken as the starting point of the preliminary diameter reduction, and the end face of the brazed connection area facing the terminal is taken as the ending point of the preliminary diameter reduction. The pipe section between the two is subjected to preliminary diameter reduction to form a locking section. The end face of the brazed connection area facing the terminal is taken as the starting point of the release section. The pipe section that has not undergone preliminary diameter reduction is retained along the direction of the terminal to form a release section. After MgO presses Pt100, the brazed connection area and the copper core wire in the locking section, the lead clamp is released, so that the position of Pt100 is transferred from the lead clamp to the MgO pressing and holding in the locking section.

[0007] In a preferred embodiment, in S3, a fixed clamping position is set on the outer periphery of the locking section, and a traction position is set on the side of the release section facing the terminal. In each round, the locking section is clamped and the release section is pulled to increase the length of the release section by 5%-10%. Then, the diameter of the release section is reduced by 0.2-0.5 mm. The local densification process where Pt100 is located is performed in 2-3 rounds. The locking section does not enter between the two clamping positions for axial pull. After the local densification of Pt100 is completed, the clamping of the locking section is released, and the diameter of the remaining pipe sections in the direction of the terminal continues to be reduced, so that the locking section bears the position of Pt100 and the release section bears the length change caused by axial pull.

[0008] In a preferred embodiment, the front end of the copper tube forms an annular end face, and the inner wall of the measuring end of the 316L stainless steel protective tube forms an annular contact area that fits with the annular end face. The copper tube extends continuously along the axial direction and covers the axial range where Pt100 is located. Only MgO is filled between the outer periphery of Pt100 and the inner wall of the copper tube. The measuring end, the annular contact area, the copper tube wall, the MgO radial heat transfer layer, and Pt100 sequentially form a heat transfer path from the object being measured to Pt100, so that Pt100 is kept axially embedded while the copper tube undertakes the metal heat transfer from the measuring end to the axial range where Pt100 is located.

[0009] In a preferred embodiment, the axial distance from the end face of Pt100 facing the measuring end to the inner wall of the measuring end of the 316L stainless steel protective tube is taken as the mechanical embedment distance, and the radial thickness of MgO between the outer surface of Pt100 and the inner wall of the copper tube is taken as the final stage heat transfer distance. The staged diameter reduction in S3 adjusts the final stage heat transfer process from the measuring end to Pt100 by changing the final stage heat transfer distance, and the mechanical embedment distance is kept at 5-10mm by the locking section, so that the mechanical embedment distance is formed by axial positioning, and the final stage heat transfer distance is formed by the radial diameter reduction of the pipe section where Pt100 is located.

[0010] In a preferred embodiment, in each stage detection in S4, the measuring end is first placed in a 0°C constant temperature bath, and the four-wire resistance of Pt100 is continuously read. When three consecutive readings are the same, the 0°C resistance is recorded. Then, the measuring end is transferred to a 100°C constant temperature bath, and the four-wire resistance of Pt100 is continuously read. When three consecutive readings are the same, the 100°C resistance is recorded. The change in resistance from 0°C to 100°C is taken as the step change. The time taken for Pt100 to reach 63.2% of the step change from the time it is transferred to the 100°C constant temperature bath is recorded. Three stage detections are performed continuously in the same stage.

[0011] In a preferred embodiment, the three times obtained in the same stage are sorted by value, the difference between the first time and the last time is used as the stage repetition difference, and the middle time is used as the stage response time; the stage response times of two adjacent stages are subtracted and the absolute value is taken. When the absolute value exceeds the sum of the repetition differences between the two stages, the next stage of diameter reduction is executed. When the absolute value does not exceed the sum of the repetition differences between the two stages, the diameter reduction of the pipe section where Pt100 is located is stopped. At each stage, the 0℃ resistance and the insulation resistance between the protective tube and the copper core wire are read simultaneously. When the 0℃ resistance enters the range of 100Ω±0.12Ω and the insulation resistance reaches 100MΩ or above, the stage test results are retained. If either condition is not met, the subsequent diameter reduction of the current workpiece is stopped, so that the stabilization process of the stage response time is established on the basis that both the Pt100 resistance state and the insulation state meet the measurement requirements.

[0012] In a preferred embodiment, in step S5, the measuring end is sealed by argon arc welding, the MgO around the lead wire is removed from the terminal and epoxy resin is poured in to form a lead wire fixing seal, and the sealed workpiece is placed in an environment of 200°C for 4 hours to remove moisture; after moisture removal, vibration aging is performed in the X direction, 100-220Hz, 10g for 8 hours. Before and after vibration aging, the response time, 0°C resistance and 100°C resistance are obtained by step temperature detection process from 0°C to 100°C, and the insulation resistance between the protective tube and the copper core wire is read. The retention state of the locking section and the MgO radial heat transfer layer after encapsulation is checked by the Pt100 measurement state before and after vibration.

[0013] In a preferred embodiment, after vibration aging, the three response times are sorted numerically and the stage repeatability difference and stage response time are obtained. The stage response times before and after vibration aging are subtracted and the absolute value is taken. If the absolute value does not exceed the sum of the stage repeatability differences before and after vibration aging, the resistance at 0°C is in the range of 100Ω±0.12Ω, the resistance at 100°C is in the range of 138.51Ω±0.15Ω, the insulation resistance reaches 100MΩ or above, and the response time does not exceed 5s, the workpiece is judged as a finished product. If the resistance and insulation resistance meet the listed ranges but the absolute value exceeds the sum of the stage repeatability differences before and after vibration aging, the workpiece is transferred to rework and the locking section and MgO radial heat transfer layer are inspected.

[0014] The technical effects and advantages of this invention are as follows: 1. By first reducing the diameter of the pipe section where Pt100 and the brazed connection area are located to form an MgO locking section, and then making the release section bear the length change caused by axial pull-out, and using the step response change of Pt100 in adjacent diameter reduction stages to determine the local densification endpoint, the embedded position of Pt100 does not move synchronously with the stretching of the release section, and the local compaction degree of MgO and the actual heat transfer state are determined together in the preparation process, thereby alleviating the problem that it is difficult to take into account the repeated stress on the connection position and the temperature response state under the continuous vibration of the intelligent sensing system. 2. First, a mechanical embedment distance of 5-10mm is formed by the end face stop and the lead wire clamp. After the MgO presses the Pt100, the brazing connection area and the copper core wire, the external clamp is released, so that the position constraint is borne by the locking section, and the subsequent axial deformation is concentrated in the release section, reducing the direct impact of the pull-out process on the Pt100 embedment position and the connection area. 3. By forming an annular metal contact between the inner wall of the measuring end and the front end of the copper tube, and extending from the copper tube to the axial range of Pt100, the input of the measuring end enters Pt100 through the protective tube, copper tube and MgO radial heat transfer layer, thus separating the mechanical embedding distance and the final stage MgO heat transfer distance. This is suitable for the structural requirements of embedded protection and temperature transfer in the manufacturing of sensitive elements and sensors. 4. Three 63.2% step response times were obtained for each local shrinkage stage. The difference between the first and last stages was used to form the stage repetition difference, and the median value was used to form the stage response time. The response changes of adjacent stages were compared with the sum of the repetition differences between the two stages, so that whether to continue shrinkage was determined by the actual response change of Pt100, avoiding the determination of the local densification endpoint of MgO based solely on a fixed number of passes. 5. By performing vibration aging after φ6 sizing, measuring end sealing, wiring end sealing and moisture removal, and verifying the response time, resistance and insulation status before and after, the mechanical locking status, electrical connection status and heat transfer status of the platinum resistance thermometer used in the intelligent sensing system can be checked in conjunction with each other at the finished product stage. Attached Figure Description

[0015] Figure 1 This is a flowchart of the method for preparing the embedded armored platinum resistance thermometer used in Embodiment 3 of the present invention. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Refer to the instruction manual appendix Figure 1The method for preparing the embedded armored platinum resistance thermometer of the present invention includes: Example 1: A Pt100 platinum thin-film resistor, four copper core wires, a copper tube, a 316L stainless steel protective tube, and 200-260 mesh MgO powder were selected. The length, width, and thickness of the Pt100 platinum thin-film resistor were recorded. The four copper core wires were numbered as the first copper core wire, the second copper core wire, the third copper core wire, and the fourth copper core wire. The first and second copper core wires were connected to one electrode of the Pt100 platinum thin-film resistor, and the third and fourth copper core wires were connected to the other electrode. The four copper core wires were separated in the assembly fixture. The arrangement ensures that the four copper core wires remain separated after entering the copper tube; the Pt100 platinum film resistor is brazed to the four copper core wires using Ag25Cu75 silver-copper alloy, with a silver mass fraction of 23%, a brazing temperature of 800℃, a holding time of 10s, and argon as the protective gas; the brazing is then allowed to cool naturally; the four brazing positions are set along the same axial region, and if there is axial misalignment among the four brazing positions, the position furthest from the terminal is taken as the end face of the brazing connection area facing the terminal. The MgO powder used is sieved in the range of 200-260 mesh and kept at 120℃ for 2 hours before filling. After drying, the MgO powder is transferred to a covered container for storage until the filling process to reduce moisture absorption during the period from the end of drying to the start of filling. The effective filling space of MgO is determined based on the inner diameter of the copper tube, the axial length to be filled, the space occupied by the Pt100 platinum film resistor, and the space occupied by the four copper core wires. The unit volume mass of the same batch of MgO powder is weighed using a fixed-volume container, and the required powder mass for a single workpiece is determined based on the effective filling space. During actual filling, the MgO addition mass is checked by weighing before and after filling, and the powder surface position at the terminal is not used as the filling endpoint. A copper tube is inserted into a 316L stainless steel protective tube. The front end of the copper tube is machined into a continuous annular end face, which directly abuts against the inner wall of the measuring end of the 316L stainless steel protective tube, without filling the space between them with MgO. The copper tube extends axially from the annular contact position and covers the axial range where the Pt100 platinum film resistor is located. After the Pt100 platinum film resistor is inserted into the copper tube, the outer surface of the Pt100 platinum film resistor that bears the temperature sensing function faces the inner wall of the copper tube, and MgO filling space is reserved between the Pt100 platinum film resistor and the inner wall of the copper tube. An axial positioning structure consisting of an end face stop, an axial guide rail, and a lead wire clamp is used to establish the mechanical embedment distance of the Pt100 platinum film resistor. The end face stop abuts against the outer end face of the measuring end of a 316L stainless steel protective tube. The lead wire clamp has four separate clamping positions, each clamping one of four copper core wires. The wall thickness of the measuring end of the 316L stainless steel protective tube is measured, and the axial length from the end face of the Pt100 platinum film resistor facing the measuring end to the copper core wire clamping position is also measured. The wall thickness of the measuring end, the axial length, and the 5mm mechanical embedment distance are added together, and the axial distance between the end face stop and the lead wire clamp is adjusted based on the obtained length. After reaching the corresponding distance, the lead wire clamp is locked so that the end face of the Pt100 platinum film resistor facing the measuring end is 5mm from the inner wall of the measuring end. Keep the lead clamp in the locked state, and pour the weighed MgO powder into the terminal in stages. After each addition of MgO powder, allow the powder to enter the copper tube along the gap between the copper core wires until all the weighed MgO has been added. After filling, take the end face of the Pt100 platinum film resistor facing the measuring end as the starting point of the preliminary diameter reduction, and the end face of the brazed connection area facing the terminal as the ending point of the preliminary diameter reduction, and perform preliminary radial diameter reduction on the tube section between the two. The preliminary diameter reduction causes the inner wall of the copper tube to move inward, and the MgO particles rearrange between the Pt100 platinum film resistor, the four copper core wires, and the inner wall of the copper tube, gradually forming a circumferential coating on the Pt100 platinum film resistor and the brazed connection area, thus forming a locking section. After the end face of the brazed connection area facing the terminal, the preliminary diameter reduction is not performed, and the release section is retained. Axial position marks are set on one side of the four copper core wires at the terminal. After one round of diameter reduction, the lead clamp is released, and the axial position of the position marks of the four copper core wires relative to the terminal reference plane is observed. If the position marks change axially, the four copper core wires are re-clamped, and the diameter of the locking section is reduced again. When the four position marks remain in their original positions after the lead clamp is released, the clamping of the four copper core wires by the axial positioning structure ends. At this time, the position holding of the Pt100 platinum film resistor is changed from the lead clamp to the compression holding formed by MgO in the locking section on the Pt100 platinum film resistor, the brazing connection area, and the copper core wire. The axial position marks are only used to confirm that the position holding has been transferred and do not participate in the stage response stop judgment. After the locking section is completed, two rounds of local densification are implemented. Before each round, the effective length between the fixed clamping position of the locking section and the traction position of the release section is measured. The axial pull-out elongation rate of this round is calculated based on the effective length measured at the beginning of this round. In the first round, the locking section is clamped, and the release section is axially pulled to increase the length of the release section by 5%. Then, the release section is reduced in diameter by 0.2 mm. At the same time, the first stage of radial densification is implemented on the tube section where the Pt100 platinum film resistor is located. The locking section and the measuring end are located outside the two positions that bear the axial elongation, so that the release section absorbs the length change caused by the axial pull-out. In the second round, the effective length of the release section is measured again, and the second round of axial pull-out is completed according to the 5% elongation rate. The 0.2 mm diameter reduction and the second stage of radial densification of the tube section where the Pt100 platinum film resistor is located are also completed. During the two rounds of local densification, the annular end face of the copper tube is always in contact with the inner wall of the measuring end of the 316L stainless steel protective tube. The temperature change received by the measuring end is first transmitted to the annular contact area through the measuring end of the 316L stainless steel protective tube, then enters the copper tube wall and is transmitted along the copper tube axis to the axial region where the Pt100 platinum film resistor is located. Subsequently, it passes through the MgO radial heat transfer layer between the outer surface of the Pt100 platinum film resistor and the inner wall of the copper tube and enters the Pt100 platinum film resistor. The 5mm axial distance from the end face of the Pt100 platinum film resistor facing the measuring end to the inner wall of the measuring end is taken as the mechanical embedment distance. The radial distance between the outer surface of the Pt100 platinum film resistor that bears the temperature sensing function and the inner wall of the copper tube, passing through MgO, is taken as the final stage heat transfer distance. The mechanical embedment distance is maintained by the axial positioning and locking section, and the final stage heat transfer distance changes with the radial densification of the tube section where the Pt100 platinum film resistor is located. After each local densification stage, three stage tests are performed. The stage tests use a 0℃ constant temperature bath and a 100℃ constant temperature bath equipped with a thermally conductive metal sleeve. The measuring end is inserted into the thermally conductive metal sleeve to the fixed stop position, and the measuring end does not directly contact the liquid in the bath, thereby avoiding the entry of the constant temperature medium into MgO before the final sealing is completed. First, the measuring end is inserted into the thermally conductive metal sleeve of the 0℃ constant temperature bath, and the resistance value of the Pt100 platinum film resistor is continuously read using a four-wire resistance reading device at a fixed sampling period. The 0℃ resistance is recorded when three consecutive identical readings are obtained according to the device display resolution. Then, the measuring end is transferred to the thermally conductive metal sleeve of the 100℃ constant temperature bath, and the time when the measuring end reaches the fixed stop position is used as the timing start point. The four-wire resistance is continuously read, and the 100℃ resistance is recorded when three consecutive identical readings are obtained. The change in resistance from 0℃ to 100℃ is taken as the step change. When the discrete sampling point does not fall exactly at the 63.2% step position, two adjacent sampling points that first cross the 63.2% step position are selected, and linear interpolation is performed between the two sampling points according to the time and resistance change to obtain the time when the step change reaches 63.2%. After each 100℃ test, the measuring end is placed back into the 0℃ constant temperature bath. After obtaining three consecutive identical 0℃ resistance readings, the next test begins. Each stage is executed three times consecutively. The three response times obtained in each stage are sorted numerically, with the difference between the first and last times as the stage repetition difference, and the time in the middle of the sort as the stage response time. The first stage completes the first set of records. The second stage forms the second set of records according to the same steps. The absolute value of the difference between the response times of two adjacent stages is calculated and compared with the sum of the repetition differences between the two stages. When the relationship between the two meets the stopping condition, and the 0℃ resistance is in the range of 100Ω±0.12Ω and the insulation resistance between the protective tube and the copper core wire reaches 100MΩ or above, the local radial densification of the tube segment where the Pt100 platinum film resistor is located ends. If the stopping condition is not met in the second stage, the workpiece is removed from the subsequent finished product process of this embodiment, and no more local densification times are added outside the two rounds. In this embodiment, the tube segment containing the Pt100 platinum film resistor is sizing to φ6 in the second stage. Therefore, the stage response stops and the tube segment containing the Pt100 platinum film resistor reaches φ6 in the same processing stage. After the local densification is completed, sizing is only performed on the remaining tube segments in the direction of the wiring terminal until the remaining tube segments reach φ6, and the radial dimension of the tube segment containing the Pt100 platinum film resistor is no longer changed. After sizing the φ6, the measuring end is argon-arc welded to form a sealed connection between the end wall of the measuring end and the 316L stainless steel protective tube. MgO around the lead wires is removed from the wiring terminals to expose the four copper core wires. Epoxy resin used in production is then poured in, and the lead wires are fixed and sealed according to the mixing, potting, and curing procedures specified for the epoxy resin material. After the epoxy resin has cured, the workpiece is placed in an oven. Timing begins after the oven reaches 200℃ and is maintained for 4 hours. After dehumidification, vibration aging is performed in the X direction at 100-220Hz, 10g, and 8 hours. Before and after vibration aging, the 0℃ resistance, 100℃ resistance, and three response times were obtained using the same four-wire resistance reading method. The insulation resistance between the protective tube and the copper core wire was also measured. In the final judgment, the three response times were sorted to form the stage repeatability difference and stage response time. The difference in stage response time before and after vibration aging was then compared with the sum of the two sets of stage repeatability differences. At the same time, the 0℃, 100℃, insulation resistance, and response time conditions were judged. If any finished product condition was not met, the finished product receiving process was not initiated. If the resistance and insulation conditions were met but the response relationship was not met, the workpiece was disassembled and the MgO coating in the locking section and the MgO radial heat transfer layer between the Pt100 platinum thin film resistor and the inner wall of the copper tube were checked. The disassembled workpiece was not directly used as a finished product again. Implementation method description: In this embodiment, the axial positioning structure maintains the position of the Pt100 platinum film resistor only before the MgO is formed and constrained. After the locking section is formed, the lead clamp is released, and the position of the Pt100 platinum film resistor is transferred to the MgO in the locking section. The subsequent axial pulling action is concentrated in the release section. The locking section where the Pt100 platinum film resistor is located does not enter the axial elongation area of ​​the release section. Therefore, the mechanical embedment distance and the length of the release section are changed respectively. The annular end face of the copper tube makes metal contact with the inner wall of the measuring end. The copper tube continues to extend to the axial region where the Pt100 platinum thin film resistor is located, so that the mechanical embedded distance serves as the end position isolation function. The MgO radial heat transfer layer serves as the insulation between the Pt100 platinum thin film resistor and the copper tube and the final stage heat transfer function. The stage response judgment directly acts on the local densification process of the tube section where the Pt100 platinum thin film resistor is located, and no additional stop parameters unrelated to the actual preparation state are set. Example 2: A Pt100 platinum thin-film resistor, four copper core wires, a copper tube, a 316L stainless steel protective tube, and 200-260 mesh MgO powder were selected. The four copper core wires were arranged such that two were connected to one electrode of the Pt100 platinum thin-film resistor, and the other two were connected to the other electrode. The Pt100 platinum thin-film resistor and the copper core wires were brazed with Ag25Cu75 silver-copper alloy, with a silver mass fraction of 25%. The brazing temperature was 820℃, and the holding time was 15s. Argon gas protection was used, and the components were allowed to cool naturally after brazing. After the four-wire Pt100 assembly was formed at the brazing position, the Pt100 platinum thin-film resistor was placed under a constant temperature condition of 0℃ and the initial reference resistance was recorded in a four-wire manner. The initial reference resistance was used as the state record before the same workpiece was processed. The 0℃ resistance of each subsequent stage was recorded together with the initial reference resistance in the manufacturing record, and no new diameter reduction stop condition was set. MgO powder was kept at 120℃ for 2 hours, and then transferred to a covered container. The effective filling space was determined based on the actual dimensions of the inner cavity of the copper tube, the Pt100 platinum film resistor, and the four copper core wires. The powder filling mass was determined based on the unit volume mass of the same batch of MgO powder. The amount of MgO added was confirmed by weighing before and after filling. The copper tube forms a continuous annular end face at its front end and abuts against the inner wall of the 316L stainless steel protective tube measuring end, maintaining direct metal-to-metal contact at the contact position; the copper tube covers the area where the Pt100 platinum film resistor is located along the axial direction; an axial positioning structure is composed of an end face stop, an axial guide rail, and a lead wire clamping seat, with the end face stop abutting against the outer end face of the measuring end, and the four copper core wires being held by four clamping positions respectively; the wall thickness of the measuring end and the axial length between the end face of the Pt100 platinum film resistor facing the measuring end and the copper core wire clamping position are measured, and the distance between the end face stop and the lead wire clamping seat is determined by the sum of the two measured lengths and the 7.5mm mechanical embedment distance, so that the end face of the Pt100 platinum film resistor facing the measuring end is 7.5mm from the inner wall of the measuring end; Keep the lead clamp fixed and pour MgO treated at 120℃ into the terminal. After all the MgO is added, perform a preliminary diameter reduction on the Pt100 platinum thin film resistor from the end face facing the measuring end to the end face facing the brazing connection area to the terminal, forming a locking section. After the brazing connection area, retain the release section. Set axial position marks on the terminals of the four copper core wires respectively. If the position marks move after the lead clamp is released, restore the clamp and continue the preliminary diameter reduction. When the position marks are retained after the clamp is released, end the axial retention of the four copper core wires by the lead clamp. This embodiment employs a two-round local densification process. Before each round, the effective length of the release section is measured. In the first round, the release section length is increased by 7.5%, followed by a 0.35mm diameter reduction, completing the first stage of local radial densification for the Pt100 platinum film resistor section. In the second round, the 7.5% elongation is recalculated based on the effective length of the release section after the first round, and a second round of drawing and a 0.35mm diameter reduction are performed, completing the second stage of local radial densification for the Pt100 platinum film resistor section. During both rounds of processing, the locking section remains outside the axial drawing zone. The outer diameter of the tube section containing the Pt100 platinum thin film resistor is set to 6.7 mm at the beginning of local densification, 6.35 mm after the first stage is completed, and φ6 after the second stage is completed. The change in outer diameter is only used to form the two-stage solid processing state and is not used to replace the stage response judgment. The annular end face of the copper tube forms an annular contact area with the inner wall of the measuring end. The copper tube wall transmits the input from the measuring end to the location of the Pt100 platinum thin film resistor along the axial direction, and then enters the Pt100 platinum thin film resistor through the MgO radial heat transfer layer. The mechanical embedding distance is recorded as 7.5 mm. The final stage heat transfer distance is determined according to the actual distance from the outer surface of the Pt100 platinum thin film resistor that bears the temperature sensing function to the inner wall of the copper tube along the radial direction through MgO. Three phase tests are performed after each round; identical thermally conductive metal sleeves are installed in the 0℃ and 100℃ constant temperature baths, and the measuring end is inserted into the fixed stop position; the same four-wire resistance reading device and the same sampling period are used; when three consecutive readings at 0℃ are the same, the 0℃ resistance is recorded, and then the device is transferred to the 100℃ constant temperature bath, and timing begins when it reaches the fixed stop position; when three consecutive readings at 100℃ are the same, the 100℃ resistance is obtained, and the step change between the 0℃ resistance and the 100℃ resistance is used; the response time is obtained by linear interpolation between two adjacent sampling points crossing the 63.2% position; after each test, the device is restored to the 0℃ state before starting the next test; After sorting the response times three times, the difference between the first and last times is taken as the stage repetition difference, and the middle time is taken as the stage response time. The first stage and the second stage form the stage response time and stage repetition difference, respectively. The absolute value of the response time difference between two adjacent stages does not exceed the sum of the two stage repetition differences. At the same time, when the 0℃ resistance and insulation resistance meet the electrical conditions in the manufacturing process, the local densification of the tube section where the Pt100 platinum thin film resistor is located ends. Workpieces that do not meet the stopping relationship in the second stage are removed from the subsequent process without changing the two rounds of manufacturing boundaries by adding additional diameter reduction times. At the end of the second stage, the section containing the Pt100 platinum thin film resistance tube had reached φ6, so subsequent sizing of the remaining sections in the direction of the wiring terminal was only performed to φ6. Then, argon arc welding of the measuring end, MgO cleaning of the wiring terminal, epoxy resin potting and curing were carried out. After sealing, the tube was placed in an oven. When the oven temperature returned to 200℃, timing was started and maintained for 4 hours. Then, vibration aging was carried out in the X direction, 100-220Hz, 10g, and 8h. Before and after vibration, the four-wire resistance, insulation resistance and three-response tests were performed using the same clamping direction and the same measurement process. Then, the workpiece was processed according to the established finished product judgment relationship. Implementation method description: This implementation method uses a 7.5mm mechanical embedment distance, a 7.5% release section elongation rate, and a 0.35mm single-wheel diameter reduction to demonstrate that axial position maintenance, release section deformation, and MgO radial heat transfer layer formation can be continuously implemented within the range of parameters; the length of the release section in each round is remeasured to avoid using the length at the beginning of the first round as the basis for subsequent pull-out calculations; The mechanical embedment distance is formed by the end face stop and the lead wire clamp, and the final stage heat transfer distance is formed by the radial densification of the tube section where the Pt100 platinum thin film resistor is located. The two distances act on the mechanical position and the final stage heat transfer process respectively, avoiding the axial distance of the Pt100 platinum thin film resistor being withdrawn into the measuring end as the total temperature transfer distance. Example 3: A Pt100 platinum thin film resistor, four copper core wires, a copper tube, a 316L stainless steel protective tube, and 200-260 mesh MgO powder were selected. Two copper core wires were connected to the electrodes on both sides of the Pt100 platinum thin film resistor. Ag25Cu75 silver-copper alloy was used for brazing, with a silver mass fraction of 27%, a brazing temperature of 850℃, a holding time of 30s, and nitrogen gas as the protective gas. The resistor was allowed to cool naturally after brazing. The four brazing connection positions together formed the brazing connection area. When there was axial misalignment, the end face of the brazing connection area facing the terminal was determined by the brazing position farthest from the terminal. MgO powder is kept at 120℃ for 2 hours; the effective filling space of MgO is obtained based on the actual inner size of the copper tube, the cross-sectional area of ​​the four copper core wires and the outer size of the Pt100 platinum thin film resistor, and the powder filling mass is obtained based on the unit volume mass of MgO powder in the same batch; after weighing, MgO is added from the terminal. The front end of the copper tube is machined into a continuous annular end face, which abuts against the inner wall of the measuring end of the 316L stainless steel protective tube. MgO is not clamped at the annular contact position. The copper tube extends continuously along the axial direction and covers the location of the Pt100 platinum film resistor. The axial position of the Pt100 platinum film resistor is maintained by an end face stop, axial guide rail, and lead wire clamp. The four copper core wires are clamped by four separate positions in the lead wire clamp. The wall thickness of the measuring end and the axial length from the end face of the Pt100 platinum film resistor facing the measuring end to the copper core wire clamp position are measured. Then, a 10mm mechanical embedment distance is added to determine the distance between the end face stop and the lead wire clamp, so that the end face of the Pt100 platinum film resistor facing the measuring end is 10mm from the inner wall of the measuring end. After the lead clamp is fixed and MgO filling is completed, the diameter of the Pt100 platinum film resistor is reduced from the end face of the measuring end to the end face of the brazing connection area facing the terminal to form a locking section; the pipe section in the direction of the terminal after the locking section forms a release section; the four copper core wires form axial position marks at the terminal; when the position marks change after the lead clamp is released, the diameter reduction of the locking section is continued; when the position marks are maintained after the clamp is released, the work of the lead clamp is ended, so that the MgO in the locking section supports the position of the Pt100 platinum film resistor; This embodiment employs a three-round local densification process; the initial outer diameter of the tube segment containing the Pt100 platinum thin film resistor is set to 7.5 mm; the first, second, and third rounds reduce the diameter of the tube segment containing the Pt100 platinum thin film resistor to 7.0 mm, 6.5 mm, and φ6, respectively; the axial pull-out elongation of the release section in each round is 10%, and the radial diameter reduction in each round is 0.5 mm; the effective length of the release section is remeasured before each round, and then the axial extension is calculated by 10% based on the length of this round; the locking section is never located between the two positions bearing the axial elongation. After the first round, the first stage of three response tests is performed; after the second round, the second stage of three response tests is performed; and after the third round, the third stage of three response tests is performed. Each test starts from 0°C, with the measuring end inserted into the thermally conductive metal sleeve in the constant temperature bath until it reaches a fixed position. When three consecutive four-wire resistance readings are the same, the 0°C resistance is recorded, and then the device is transferred to a 100°C constant temperature bath. Timing begins when the measuring end reaches the fixed position in the 100°C constant temperature bath. After the 100°C state stabilizes, the step change is obtained, and the response time is obtained by linear interpolation across adjacent sampling points spanning 63.2%. After each test, the device returns to the 0°C state. The three response times of each stage are sorted numerically to form the stage repetition difference and stage response time. When the response time relationship between the first stage and the second stage does not reach the stopping relationship, the third round is entered. When the stopping relationship is met between the second stage and the third stage, and the 0℃ resistance and insulation resistance meet the manufacturing process conditions, the local densification of the tube section where the Pt100 platinum thin film resistor is located ends. If the stopping relationship is not met after the third round, the workpiece is removed from the finished product preparation process and the fourth round of local densification is not performed. When the third round was completed, the section of the tube containing the Pt100 platinum thin film resistor reached φ6; the remaining sections in the direction of the wiring terminal were sized to φ6, and then the measuring end was sealed by argon arc welding, the wiring terminal was cleaned of MgO, the four copper core wires were led out, and epoxy resin was potted; the epoxy resin was cured according to the specifications of the actual material used; after curing, it was kept in an oven at 200℃ for 4 hours, and then vibration aging was performed in the X direction, 100-220Hz, 10g, 8h; After vibration ends, the 0℃ resistance, 100℃ resistance, and three response times are obtained according to the same four-wire detection procedure as before vibration, and the insulation resistance is measured. The three response times form the stage repeatability difference and stage response time. The same comparison method is used before and after vibration for judgment. When the resistance, insulation, and response conditions are all within the acceptable range of finished products, the preparation is completed. If they are not met, the finished product acceptance process is terminated. If the response changes abnormally but the resistance and insulation conditions still meet the requirements, the locking section and MgO radial heat transfer layer are disassembled and inspected. The disassembled workpiece is used for process cause analysis. Implementation method description: Three rounds of local densification constitute the processing boundary of the tube segment where the Pt100 platinum thin film resistor is located; after the third round, no further local diameter reduction is added, so that a definite termination relationship is formed between the stage response judgment and the manufacturing range of 2-3 rounds; if the local densification cannot be completed in the third stage, the workpiece is removed from the subsequent preparation process, instead of adding a new diameter reduction round. The copper tube extends along the 10mm mechanical embedment distance to the location of the Pt100 platinum film resistor, so that the axial transmission process of the measuring end entering the copper tube and the radial transmission process of the MgO around the Pt100 platinum film resistor occur sequentially; the 10mm mechanical embedment does not convert into a 10mm MgO axial transmission path. Comparative Example 1; The Pt100 platinum thin film resistor, four-wire connection, Ag25Cu75 brazing, 7.5mm mechanical embedding distance, MgO and copper tube structure are used in Example 2. However, after completing the MgO filling, the locking section is omitted from the pre-diameter reduction and the partition relationship between the locking section and the release section is not established. After the lead clamp is released, the tube body is directly subjected to axial pulling and radial diameter reduction. Implementation Description: By omitting the locking section, the Pt100 platinum film resistor directly enters the axial pulling state from the external clamping state, and MgO has not yet formed an independent position holding area; the release section no longer bears the responsibility of an independent axial deformation area, and there is a lack of isolation process between the Pt100 platinum film resistor, the brazed connection area, and the copper core wire and the tube body axial deformation; the comparative example is used to illustrate the role of the order of forming the locking section first, then releasing the external clamping, and then pulling the release section; Comparative Example 2; The Pt100 platinum thin film resistor is embedded in the circuit with a locking section, a release section, and a staged diameter reduction process as described in Example 2. However, the front end of the copper tube does not form an annular metal contact with the inner wall of the measuring end of the 316L stainless steel protective tube. MgO is filled between the front end of the copper tube and the inner wall of the measuring end to add an MgO layer between the measuring end and the copper tube in the transmission path of the measuring end into the Pt100 platinum thin film resistor. Implementation Description: The locking and releasing sections can still maintain the position and distribute axial deformation. Therefore, the comparative example retains the mechanically embedded part, only changing the heat transfer structure from the measuring end to the Pt100 platinum thin film resistor. After the copper tube front end loses its metal contact with the inner wall of the measuring end, the input to the measuring end needs to pass through the MgO outside the copper tube front end before entering the copper tube or the inner MgO. The mechanically embedded distance and the non-metallic transmission path are recoupled. The comparative example is used to illustrate that the annular contact area and the axial extension of the copper tube are not ordinary support structures, but part of the heat transfer path under embedded conditions. Comparative Example 3; The mechanical embedded distance, locking section, release section, copper tube annular contact area and MgO radial heat transfer layer in Example 2 are adopted, but the local densification is fixed in two rounds. After each round, no three step response detections are performed, no stage repeat difference and stage response time are formed, and no decision is made on whether to continue the diameter reduction of the tube section where the Pt100 platinum thin film resistor is located based on the response relationship of adjacent stages. Implementation method description: A fixed number of times can specify the actions performed by the equipment, but it cannot directly reflect whether the radial heat transfer layer of MgO around the Pt100 platinum thin film resistor still changes between adjacent processing states; the number of times the same equipment is used only to describe the processing history and cannot replace the stage response state formed by the Pt100 platinum thin film resistor itself; the comparative example is used to illustrate that the stage response judgment is involved in the end point of local densification, rather than adding an independent detection after the finished product is completed. Comparative Example 4; The materials, four-wire connection, MgO, copper tube and staged diameter reduction process in Example 2 are used, but the Pt100 platinum film resistor is not buried 5-10mm inward towards the terminal, but the end face of the Pt100 platinum film resistor facing the measuring end is set near the inner wall of the measuring end. Implementation Description: By omitting the 5-10mm mechanical embedding, the Pt100 platinum thin film resistor and the brazing connection area enter the area adjacent to the measuring end, and the end structure lacks the positional separation formed by axial retraction between it and the temperature sensing component. In this solution, after mechanical embedding, a heat transfer path is formed through the annular contact area of ​​the copper tube, the copper tube wall, and the MgO radial heat transfer layer. The purpose is not simply to extend the distance between the Pt100 platinum thin film resistor and the measuring end, but to establish two different structural paths between position protection and temperature transfer. Comparative Example 5; Using the Pt100 platinum thin film resistor, four copper core wires, copper tube and mechanical embedding position in Example 2, MgO is still 200-260 mesh powder, but the treatment of keeping it at 120℃ for 2 hours is omitted, and the stored MgO is directly poured in from the terminal, and the rest of the process remains unchanged. Implementation method description: In this preparation process, MgO is simultaneously located between the Pt100 platinum thin film resistor and the copper tube, as well as between the copper core wire and the metal tube. Subsequently, a locking section and a radial heat transfer layer of MgO will be formed. If the moisture state changes with storage conditions before filling, the difference in raw material state will be carried into the subsequent insulation and heat transfer process after MgO enters the sealed tube. Setting the 120℃ temperature for 2 hours before filling allows the MgO entering the locking section formation process to undergo the same dehumidification process first, reducing the interference of moisture state changes on subsequent processes from the material preparation stage. Comparative Example 6; The Pt100 platinum thin film resistor, four copper core wires, mechanical embedded position, MgO filling, locking section, release section and stage response judgment in Example 2 are used, but the Pt100 platinum thin film resistor and copper core wire are not brazed with Ag25Cu75 silver copper alloy, but are connected with ordinary soft solder, while the rest of the process remains unchanged. Implementation Description: The four-wire Pt100 module undertakes both the final temperature measurement and the response reading during the local densification stage. The connection position is located within the locking section and undergoes the manufacturing process together with MgO compaction, subsequent encapsulation, and vibration aging. Therefore, the connection status between the electrode and the copper core wire directly enters the four-wire resistance reading process at each stage. Using Ag25Cu75 silver-copper alloy and limiting the silver mass fraction, brazing temperature, and holding time, the electrode connection is first formed in the predetermined brazing process, and then enters the MgO locking and stage response judgment, avoiding mixing the connection process changes with the MgO radial heat transfer layer changes in the same manufacturing stage.

[0018] Table 1. Results of Four-Line Pt100 Assembly, Axial Positioning, and Locking: ; In Table 1, the initial reference resistance was obtained after the Pt100 platinum film resistor was brazed with four copper core wires using Ag25Cu75 and allowed to cool naturally. During measurement, the Pt100 was placed under a constant temperature condition of 0°C, and the resistance was read in a four-wire manner. Examples 1, 2, and 3 used silver mass fractions of 23%, 25%, and 27%, and brazing conditions of 800°C, 820°C, and 850°C, respectively. The resulting initial reference resistance was used to record the electrical state of the four-wire Pt100 assembly before it entered the MgO filling and diameter reduction process, and did not participate in the local densification stop calculation. The mechanical embedded distance is the axial distance between the end face of Pt100 facing the measuring end and the inner wall of the measuring end of the 316L stainless steel protective pipe. After the mechanical embedded distance is established, a position reference is set at the connection end of the four copper core wires, and the reference position is read with a resolution of 0.01mm. When no change in the reference position is read after the locking section is formed and the lead clamp is released, it is recorded as 0.00mm in the table. During the local densification process, the locking section does not enter between the two positions that bear the axial extension of the release section. Therefore, the mechanical embedded distance continues to maintain the positional relationship formed by the locking section. The 5%, 7.5%, and 10% axial extension of the release section are not included in the mechanical embedded distance. When the local densification is completed in the three embodiments, the pipe section where Pt100 is located enters φ6, so that the same measuring section shape conditions can be formed for subsequent encapsulation. Table 2. Staged densification and response results of the pipe section containing Pt100: ; In Table 2, each stage starts from a steady state at 0℃, then the measuring end is transferred to a constant temperature condition of 100℃, and timing begins when the measuring end reaches the fixed insertion position. The change in resistance between 0℃ and the steady resistance at 100℃ is taken as the step change, and the time taken for the Pt100 resistance change to reach 63.2% of the step change is obtained. When the sampling point crosses the 63.2% position, linear interpolation is performed using the adjacent sampling points on both sides of the crossed position. After one 100℃ process is completed, the system returns to a steady state at 0℃ before starting the next measurement. Therefore, the three response times in the table have the same starting conditions. The three response times are ordered numerically. The difference between the first and last times is taken as the stage repetition difference, and the middle time is taken as the stage response time. In Example 1, the stage response time difference between the two stages is 0.06s, and the sum of the repetition differences between the two stages is 0.09s. Therefore, local densification ends in the second stage. In Example 2, the stage response time difference between the two stages is 0.08s, and the sum of the repetition differences between the two stages is 0.09s. Similarly, the second stage ends. In Example 3, the stage response time difference between the first and second stages is 0.28s, and the sum of the repetition differences between the two stages is 0.21s. Therefore, the third stage continues. The stage response time difference between the second and third stages is 0.12s, and the sum of the repetition differences between the two stages is 0.14s. Therefore, local densification ends in the third stage. The resistance at 0℃ in each stage is within the range of 100Ω ± 0.12Ω, and the insulation resistance reaches more than 100MΩ. Therefore, the stage response results proceed to the subsequent judgment process. This process allows the decision to continue or stop necking to be determined by the response change of the same Pt100 under adjacent machining conditions, rather than by a fixed number of machining operations. Table 3. Pt100 condition results before and after packaging and vibration aging: ; Table 2 shows that after the local densification cessation stage, the remaining pipe sections are sized to φ6, and then the argon arc welding of the measuring end, the epoxy resin fixing and sealing of the wiring end, and the 200℃ maintenance for 4 hours for moisture removal are completed in sequence. The pre-vibration data in Table 3 were obtained after the sealing and moisture removal were completed. Therefore, the response time of the pre-vibration stage is not directly used from the local densification stage response time in Table 2. Subsequently, vibration aging is carried out in the X direction, 100-220Hz, 10g, and 8h, and the same 0℃ to 100℃ step method as before vibration is used to obtain the response time of the three vibration stages. In Example 1, the response time difference before and after vibration was 0.02s, and the sum of the repeatability differences before and after vibration was 0.09s; in Example 2, the differences were 0.02s and 0.08s respectively; in Example 3, the differences were 0.03s and 0.10s respectively. The stage response time difference in all three examples did not exceed the sum of the repeatability differences before and after vibration. The resistance at 0℃ after vibration was in the range of 100Ω±0.12Ω, and the resistance at 100℃ was in the range of 138.51Ω±0.15Ω. The insulation resistance reached more than 100MΩ, and the stage response time after vibration did not exceed 5s. Table 2 reflects the formation state of the MgO radial heat transfer layer during the local densification process. Table 3 further reflects whether the locking section, electrical connection, and radial heat transfer state changed beyond the repeatability fluctuation range after the completion of encapsulation, dehumidification, and vibration. The two sets of data were used for the manufacturing process stoppage and the finished product status judgment, respectively. Table 4. Results of the single-factor comparison: ; Among them, Comparative Examples 1, 2, 4, 5 and 6 use the process conditions of Example 2 as a reference, only changing the process contents listed in the table; Comparative Example 3 uses the three-stage processing conditions of Example 3 as a reference, and artificially ends the local densification in the second stage. Table 4 records the absolute values ​​of the response time differences between adjacent stages and the sum of the repetition differences between the two stages in the order of “response time difference between adjacent stages and sum of the repetition differences between the two stages”. In Comparative Example 1, after omitting the division of labor between the locking and releasing stages, Pt100 does not form a position constraint borne by MgO before the axial drawing begins, and the releasing stage no longer bears the drawing length change alone. Therefore, the initial 7.5mm embedded position changes axially after forming. Comparative Example 2 retains the position locking and only cancels the annular metal contact between the front end of the copper tube and the inner wall of the measuring end, so that an MgO transfer zone is added between the measuring end and the copper tube. The final change is mainly manifested as an extension of the response time. Comparative Example 3 does not change the material and heat transfer structure, and only ends the processing in the second stage of Example 3. The response time difference between the second stage and the first stage is 0.28s, while the sum of the repetition differences between the two stages is 0.21s. According to the stage judgment relationship, it should still continue to enter the third stage. Therefore, the fixed number of times cannot replace the stage response relationship to determine the stopping point. Comparative Example 4 places Pt100 near the inner wall of the measuring end, shortening the temperature transfer process. Therefore, the response time is not a limiting factor. However, the Pt100 body and the connection area lose the positional isolation formed by the 5-10mm axial embedment. After vibration, the 0℃ resistance enters the range of the finished product. Comparative Example 5 only omits the 120℃ holding time of 2 hours before MgO filling. Its mechanical position, stage response and Pt100 resistance state do not show the same abnormality. However, the insulation resistance drops below 100MΩ, reflecting that the moisture state of MgO before entering the closed structure directly affects the insulation between the copper core wire and the metal tube. Comparative Example 6 retains MgO, embedding and heat transfer structure, only changing the connection method between Pt100 and copper core wire. After vibration and 200℃ dehumidification process, the 0℃ resistance enters the range of the specified range. This links the Ag25Cu75 brazing process with the electrical connection state of the four-wire Pt100 assembly in the subsequent diameter reduction, packaging and vibration processes.

[0019] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an embedded armored platinum resistance thermometer, characterized in that, include: S1. Connect the Pt100 platinum film resistor to four copper core wires. Insert the copper tube into the 316L stainless steel protective tube, so that the front end of the copper tube contacts the inner wall of the measuring end of the protective tube. Insert the Pt100 into the copper tube and make its end face facing the measuring end 5-10mm away from the inner wall of the measuring end. S2. Keep the axial position of Pt100, pour MgO into the terminal, reduce the diameter of the pipe section covering Pt100 and the connection area first, so that MgO presses Pt100 and copper core wire and adheres to the inner wall of copper pipe to form a locking section, and retain the release section in the locking section towards the terminal. S3. Fix the locking section, pull the release section axially and reduce the diameter in stages to maintain a 5-10mm axial embedment distance of Pt100, and compress the MgO radial heat transfer layer between Pt100 and the inner wall of the copper tube, so that the heat received by the measuring end enters Pt100 through the protective tube, copper tube and MgO radial heat transfer layer. S4. After each stage of diameter reduction, apply the same step temperature to the measuring end three times, and read the time required for Pt100 to reach a step change of 63.2% using four lines. After sorting the three times, take the difference between the first and last stages as the stage repeatability difference and the middle value as the stage response time. Stop the diameter reduction of the pipe section where Pt100 is located when the difference between the response times of two adjacent stages does not exceed the sum of the two stage repeatability differences; otherwise, continue the diameter reduction. S5. Reduce the diameter of the remaining pipe sections to φ6, complete the sealing of the measuring end, insulation sealing of the wiring end, moisture removal and vibration aging, and re-measure the four-wire resistance, insulation resistance and response time to obtain the embedded armored platinum resistance thermometer.

2. The method for preparing the embedded armored platinum resistance thermometer according to claim 1, characterized in that: In S1, two copper core wires are connected to the two electrodes of the Pt100 platinum thin film resistor. The four-wire Pt100 assembly is formed by brazing with Ag25Cu75 silver-copper alloy. The silver mass fraction is 23%-27%. The brazing temperature is 800-850℃, the holding time is 10-30s, and the protective gas is argon or nitrogen. After brazing and natural cooling, the Pt100 is placed in a 0℃ constant temperature bath and the reference resistance is read and recorded as the initial reference resistance using the four-wire method. The MgO is a 200-260 mesh mixed powder and is kept at 120℃ for 2 hours before filling.

3. The method for preparing the embedded armored platinum resistance thermometer according to claim 2, characterized in that: In S1, an axial positioning structure consisting of an end face stop, an axial guide rail, and a lead wire clamp is used to maintain the embedded position of Pt100. The end face stop abuts against the outer end face of the measuring end of the 316L stainless steel protective tube. The lead wire clamp moves along the axial guide rail and clamps four copper core wires. The wall thickness of the measuring end of the 316L stainless steel protective tube and the axial length from the end face of Pt100 facing the measuring end to the clamping position of the copper core wires are obtained. The axial distance between the end face stop and the lead wire clamp is determined by the sum of the wall thickness of the measuring end, the axial length, and the 5-10mm embedded distance. After the axial distance is reached, the lead wire clamp is fixed so that the end face of Pt100 facing the measuring end is located at a position 5-10mm away from the inner wall of the measuring end. In S2, the end face of Pt100 facing the measuring end is taken as the starting point of the preliminary diameter reduction, and the end face of the brazed connection area facing the terminal is taken as the ending point of the preliminary diameter reduction. The pipe section between the two is subjected to preliminary diameter reduction to form a locking section. The end face of the brazed connection area facing the terminal is taken as the starting point of the release section. The pipe section that has not undergone preliminary diameter reduction is retained along the direction of the terminal to form a release section. After MgO presses Pt100, the brazed connection area and the copper core wire in the locking section, the lead clamp is released, so that the position of Pt100 is transferred from the lead clamp to the MgO pressing and holding in the locking section.

4. The method for preparing the embedded armored platinum resistance thermometer according to claim 3, characterized in that: In S3, a fixed clamping position is set on the outer periphery of the locking section, and a traction position is set on the side of the release section facing the terminal. In each round, the locking section is clamped and the release section is pulled to increase the length of the release section by 5%-10%. Then, the diameter of the release section is reduced by 0.2-0.5mm. The local densification process where Pt100 is located is performed in 2-3 rounds. The locking section does not enter between the two clamping positions for axial pull. After the local densification of Pt100 is completed, the clamping of the locking section is released, and the diameter of the remaining pipe sections in the direction of the terminal continues to be reduced so that the locking section bears the position of Pt100 and the release section bears the length change caused by axial pull.

5. The method for preparing the embedded armored platinum resistance thermometer according to claim 4, characterized in that: The copper tube has an annular end face at its front end, and the inner wall of the measuring end of the 316L stainless steel protective tube forms an annular contact area that fits with the annular end face. The copper tube extends continuously along the axial direction and covers the axial range where Pt100 is located. Only MgO is filled between the outer periphery of Pt100 and the inner wall of the copper tube. The measuring end, the annular contact area, the copper tube wall, the MgO radial heat transfer layer, and Pt100 sequentially form a heat transfer path from the object being measured to Pt100, so that Pt100 is kept axially embedded while the copper tube undertakes the metal heat transfer from the measuring end to the axial range where Pt100 is located.

6. The method for preparing the embedded armored platinum resistance thermometer according to claim 5, characterized in that: The axial distance from the end face of Pt100 facing the measuring end to the inner wall of the measuring end of the 316L stainless steel protective pipe is taken as the mechanical embedment distance, and the radial thickness of MgO between the outer surface of Pt100 and the inner wall of the copper pipe is taken as the final stage heat transfer distance. The staged diameter reduction in S3 adjusts the final stage heat transfer process from the measuring end to Pt100 by changing the final stage heat transfer distance, and the mechanical embedment distance is kept at 5-10mm by the locking section, so that the mechanical embedment distance is formed by axial positioning, and the final stage heat transfer distance is formed by the radial diameter reduction of the pipe section where Pt100 is located.

7. The method for preparing the embedded armored platinum resistance thermometer according to claim 6, characterized in that: In each stage of the S4 test, the measuring end is first placed in a 0℃ constant temperature bath, and the four-wire resistance of Pt100 is continuously read. When three consecutive readings are the same, the 0℃ resistance is recorded. Then, the measuring end is transferred to a 100℃ constant temperature bath, and the four-wire resistance of Pt100 is continuously read. When three consecutive readings are the same, the 100℃ resistance is recorded. The change in resistance from 0℃ to 100℃ is taken as the step change. The time taken for Pt100 to reach 63.2% of the step change from the time it is transferred to the 100℃ constant temperature bath is recorded. The same stage test is performed three times consecutively.

8. The method for preparing the embedded armored platinum resistance thermometer according to claim 7, characterized in that: The three times obtained in the same stage are sorted by value. The difference between the first and last times is taken as the stage repetition difference, and the middle time is taken as the stage response time. The stage response times of two adjacent stages are subtracted and the absolute value is taken. When the absolute value exceeds the sum of the repetition differences of the two stages, the next stage of diameter reduction is executed. When the absolute value does not exceed the sum of the repetition differences of the two stages, the diameter reduction of the pipe section where Pt100 is located is stopped. At each stage, the 0℃ resistance and the insulation resistance between the protective tube and the copper core wire are read simultaneously. When the 0℃ resistance enters the range of 100Ω±0.12Ω and the insulation resistance reaches 100MΩ or above, the stage test results are retained. If either condition is not met, the subsequent diameter reduction of the current workpiece is stopped, so that the stabilization process of the stage response time is established on the basis that both the Pt100 resistance state and the insulation state meet the measurement requirements.

9. The method for preparing the embedded armored platinum resistance thermometer according to claim 8, characterized in that: In S5, the measuring end is sealed by argon arc welding, the MgO around the lead wire is removed from the terminal and epoxy resin is poured in to form a lead wire fixation seal, and the sealed workpiece is placed in a 200℃ environment for 4 hours to remove moisture. After moisture removal, vibration aging is performed in the X direction, 100-220Hz, 10g for 8 hours. Before and after vibration aging, the response time, 0℃ resistance and 100℃ resistance are obtained by step temperature detection process from 0℃ to 100℃. The insulation resistance between the protective tube and the copper core wire is read. The Pt100 measurement status before and after vibration is used to check the retention status of the locking section and MgO radial heat transfer layer after encapsulation.

10. The method for preparing the embedded armored platinum resistance thermometer according to claim 9, characterized in that: After vibration aging, the three response times are sorted by value, and the stage repeatability difference and stage response time are obtained. The stage response times before and after vibration aging are subtracted and the absolute value is taken. If the absolute value does not exceed the sum of the stage repeatability differences before and after vibration aging, the resistance at 0℃ is in the range of 100Ω±0.12Ω, the resistance at 100℃ is in the range of 138.51Ω±0.15Ω, the insulation resistance reaches 100MΩ or above, and the response time does not exceed 5s, the workpiece is judged as a finished product. If the resistance and insulation resistance meet the listed ranges but the absolute value exceeds the sum of the stage repeatability differences before and after vibration aging, the workpiece is transferred to rework and the locking section and MgO radial heat transfer layer are inspected.

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