A bimetallic self-adaptive thermal resistance temperature measurement system and method

Abstract

The application discloses a bimetallic self-adaptive thermistor temperature measuring system and method, and relates to the technical field of industrial temperature measurement. The application is composed of a spiral bimetallic sheet, a Pt100 platinum resistance, a variable compensation resistance sliding mechanism, a range switching switch and a thermal circuit breaker. The spiral bimetallic sheet generates displacement with temperature and drives the sliding sleeve block to change the compensation resistance, and simultaneously triggers a K1 switching voltage division network at a 400 DEG C threshold, so that the bridge gain is self-adaptive. After the signal is amplified by INA333, it is solved by MCU according to the Callendar-VanDusen equation, and combined with R var Voltage to realize real-time linearization and drift compensation; when the temperature is out of limit, the thermal circuit breaker automatically cuts off the power supply of the bridge, ensuring safety. The system has the advantages of compact structure, range coverage of-200 DEG C-1000 DEG C, wide temperature range high sensitivity measurement, passive over-temperature protection, and is suitable for precise temperature monitoring in extreme industrial environments.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial temperature measurement, in particular to a bimetallic self-adaptive thermistor temperature measurement system and method. BACKGROUND

[0002] In the field of industrial temperature measurement, traditional platinum resistance thermometers (Pt100) are widely used due to their high linearity and good stability. However, most existing Pt100 temperature measurement probes use fixed bridge circuits and constant gain amplification structures, and the working range is usually limited to the -200℃-850℃ interval. When the temperature exceeds the upper limit, the MCU software must be relied on to compress the gain or cut off the power supply, resulting in a lagging response and unreliable protection. In addition, fixed gain amplifiers are not sensitive to small resistance changes at low temperatures, and are prone to over-amplification at high temperatures, causing output saturation. The non-linear error after bridge imbalance needs to be corrected by the backend software, increasing the computational burden of the MCU. To deal with drift, traditional solutions generally rely on periodic calibration or the addition of expensive reference resistance networks, which cannot achieve online and self-adaptive compensation. At the same time, most probes only use software threshold alarms when the temperature is too high, and if the MCU or ADC fails, the sensor may be damaged and safety accidents may occur. In summary, the existing technology still has the problems of limited measurement sensitivity range, insufficient real-time linearization, single over-temperature protection, and weak hardware adaptive ability. SUMMARY

[0003] To overcome the above-mentioned defects of the prior art, the present application provides the following technical solution: a bimetallic self-adaptive thermistor temperature measurement system, comprising a signal processing unit, a spiral bimetallic sheet, and a resistance thermometer element, wherein the spiral bimetallic sheet is formed by welding the first metal layer and the second metal layer along the length direction and then rolling it; the resistance thermometer element is coaxially attached and wound with the spiral bimetallic sheet; further comprising a mechanical displacement conversion mechanism, which is used to convert the deformation displacement of the spiral bimetallic sheet into a sliding displacement along the potential sliding rod; the signal processing unit includes a bridge, a differential amplifier, and a microcontroller; wherein the spiral bimetallic sheet is spirally arranged on the outside of the spiral bimetallic sheet guide column, which is fixed on the temperature measurement plate, wherein the bottom end of the potential sliding rod is fixed with the temperature measurement plate, the bottom end of the spiral bimetallic sheet is fixed with the potential sliding rod and the temperature measurement plate through the bottom fixing block, and the top end of the spiral bimetallic sheet is fixed with a sliding sleeve block which is slidingly sleeved on the outer surface of the potential sliding rod; wherein the outer surface of the potential sliding rod is provided with a conductive sliding segment in conductive sliding cooperation with the sliding sleeve block, which is used to switch the resistance value of the bridge and disconnect the resistance thermometer element circuit when the temperature is too high; the outside of the spiral bimetallic sheet guide column is sleeved with a heated ceramic cover, and the spiral bimetallic sheet can freely stretch and contract between the spiral bimetallic sheet guide column and the heated ceramic cover.

[0004] Preferably, the linear expansion coefficient of the first metal layer is ≤3×10⁻ 6 / K, the linear expansion coefficient of the second metal layer is greater than or equal to 13*10⁻ 6 / K.

[0005] Preferably, the resistance thermometer element is a Pt100 grade platinum resistance, and the temperature measurement range is -200℃-1000℃.

[0006] Preferably, the measuring arm rod is fixedly installed on the heated ceramic cover through a connecting ceramic disc, the heated ceramic cover is fixedly matched with the temperature measuring plate, a lead wire passage is arranged at the axial position of the measuring arm rod, and the lead wire passage is used for threading to lead out the electric signal of the resistance thermometer element and the potential sliding rod.

[0007] Preferably, the resistance value of the potential sliding rod and the sliding sleeve block sliding conductive matching section is 0-5kΩ, and the stroke is matched with the displacement of the spiral bimetallic strip.

[0008] Preferably, the signal processing unit also collects the output of the resistance thermometer element, and is used for real-time correction of the drift of the resistance thermometer element.

[0009] A temperature measurement method of a bimetallic self-adaptive thermal resistance temperature measurement system, comprising the following steps:

[0010] S1, the resistance thermometer element is contacted with the measured body through the heated ceramic cover and the temperature measuring plate, so that heat is transmitted to the spiral bimetallic strip and the resistance thermometer element; S2, the position of the sliding sleeve block on the potential sliding rod is automatically adjusted according to the displacement of the spiral bimetallic strip; S3, when the displacement of the sliding sleeve block on the potential sliding rod reaches a threshold value, a reconfiguration bridge is triggered to realize switching of the bridge resistance value; S4, a signal processing unit synchronously reads the resistance thermometer element and the potential sliding rod signals and outputs the temperature; S5, when the displacement of the sliding sleeve block on the potential sliding rod reaches an extreme displacement, the measurement loop is disconnected.

[0011] Preferably, the step S4 comprises joint calculation of the correction coefficient of the resistance value of the resistance thermometer element and the resistance value of the potential sliding rod by using the Callendar-Van Dusen equation.

[0012] Preferably, in the step S2, the deformation displacement of the spiral bimetallic strip is continuously adjusted within a 0-4mm displacement range with temperature.

[0013] Compared with the prior art, the present application has the following beneficial effects: (1) the present application uses a variable compensation resistance driven by a spiral bimetallic strip and a range switching switch K1 to realize double self-adaptation of the bridge resistance value and the input dynamic range of the amplifier. When the temperature is lower than 400℃, the compensation resistance remains in a high resistance state, the low-temperature section bridge imbalance degree is improved, and the micro ΔV B; When the temperature rises, the resistance continuously decreases with displacement and triggers K1 to cut into the voltage division network at the threshold point, actively compresses the gain, and avoids output saturation at high temperature section. The pure mechanical-electrical coupling mechanism can maintain excellent signal-to-noise ratio and linearity in the range of-200℃-1000℃ without the intervention of MCU, and significantly expands the effective working interval of the temperature measurement system; (2) The spiral bimetallic displacement and temperature of the present application have one-to-one correspondence, and the displacement of the sliding sleeve on the potential sliding rod changes the compensation resistance value in real time, which is equivalent to the pre-linearization processing of the Pt100 resistance change. Combined with the MCU based on the Callendar-Van Dusen equation, the overall nonlinear error can be compressed to less than half of the traditional scheme, while significantly reducing the operation amount and storage consumption of MCU, realizing the high-precision temperature solution of hardware-software cooperation; (3) The present application connects the thermal circuit breaker in series in the Pt100 power supply loop. When the environmental temperature exceeds 1050℃ limit, the thermal circuit breaker automatically trips, directly cutting off the power supply of the bridge, so that ΔV B is zeroed and the fault is judged by the MCU. The protection completely depends on the material properties of the element itself without external power supply or control signal, avoiding software failure risk and ensuring the safety of the sensor and the backend equipment. After cooling down, the device automatically resets and can quickly recover measurement, improving system reliability and maintainability; (4) The spiral bimetallic sheet, Pt100 winding body and variable resistance sliding mechanism of the present application are coaxially integrated. The protection channel is formed by the heated ceramic cover and the guide column, which not only provides thermal isolation above 1000℃, but also allows the bimetal to freely expand and contract without additional induction rod or spring assembly. The overall number of parts is reduced by more than 30%, reducing assembly complexity and cost; (5) The present application detects the potential sliding rod R var voltage and K1 state, and the MCU can quickly identify the range interval and the health of the compensation resistance. When the compensation resistance is abnormally open or stuck, the ΔV B -R var corresponding relationship deviates from the calibration curve, it immediately alarms and records the maintenance code; In normal operation, the range switching information is also used to automatically select the best gain table, zero compensation and filter constant, to ensure the stability of the whole measurement. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 The present application is a schematic diagram of the heated ceramic cover structure.

[0015] Figure 2 The present application is a schematic diagram of the internal structure of the heated ceramic cover.

[0016] Figure 3 The present application is a schematic diagram of the spiral bimetallic sheet structure.

[0017] Figure 4 The present application is a schematic diagram of the working principle.

[0018] In the figure: 101-measuring arm rod; 102-connecting ceramic disc; 103-heated ceramic cover; 104-temperature measuring plate; 105-lead channel; 106-spiral bimetallic piece guide column; 107-resistance thermometer element; 108-spiral bimetallic piece; 109-bottom fixing block; 110-potentiometric sliding rod; 111-sliding sleeve block. DETAILED DESCRIPTION

[0019] The technical solutions of the present application will be further described below in combination with the accompanying drawings Figures 1-4 , and through the specific embodiments.

[0020] The present application provides a bimetallic self-adaptive thermal resistance temperature measurement system, comprising a signal processing unit, a spiral bimetallic piece 108 and a resistance thermometer element 107, wherein the spiral bimetallic piece 108 is wound after being welded along the length direction by a first metal layer and a second metal layer; the resistance thermometer element 107 is coaxially attached and wound with the spiral bimetallic piece 108; further comprising a mechanical displacement conversion mechanism, which is used to convert the deformation displacement of the spiral bimetallic piece 108 into sliding displacement along the potentiometric sliding rod 110; the signal processing unit comprises a bridge, a differential amplifier and a microcontroller; wherein the spiral bimetallic piece 108 is spirally arranged on the outside of the spiral bimetallic piece guide column 106, and the spiral bimetallic piece guide column 106 is fixed on the temperature measuring plate 104, wherein the bottom end of the potentiometric sliding rod 110 is fixed with the temperature measuring plate 104, and the bottom end of the spiral bimetallic piece 108 is fixed with the potentiometric sliding rod 110 and the temperature measuring plate 104 through the bottom fixing block 109, and the top end of the spiral bimetallic piece 108 is fixed with the sliding sleeve block 111, and the sliding sleeve block 111 is slidingly sleeved on the outer surface of the potentiometric sliding rod 110; wherein the outer surface of the potentiometric sliding rod 110 is provided with a conductive sliding section which is in conductive sliding cooperation with the sliding sleeve block 111, for switching the resistance value of the bridge, and disconnecting the resistance thermometer element 107 loop when overtemperature; the heated ceramic cover 103 is sleeved on the outside of the spiral bimetallic piece guide column 106, and the spiral bimetallic piece 108 can freely stretch and shrink between the spiral bimetallic piece guide column 106 and the heated ceramic cover 103. The linear expansion coefficient of the first metal layer is ≤3×10⁻ 6 / K, and the linear expansion coefficient of the second metal layer is ≥13×10⁻ 6 / K. The resistance thermometer element 107 is a Pt100 grade platinum resistance, with a temperature measurement range of -200℃-1000℃. The measuring arm rod 101 is fixedly installed on the heated ceramic cover 103 through the connecting ceramic disc 102, and the heated ceramic cover 103 is fixedly matched with the temperature measuring plate 104. The shaft center position of the measuring arm rod 101 is provided with a lead wire passage 105, which is used for threading and leading out the electrical signals of the resistance thermometer element 107 and the potential sliding rod 110. The resistance value of the sliding conductive section of the potential sliding rod 110 and the sliding sleeve block 111 is 0-5kΩ, and the stroke is matched with the displacement of the spiral bimetallic strip 108. The signal processing unit also collects the output of the resistance thermometer element 107, which is used for real-time correction of the drift of the resistance thermometer element 107.

[0021] A temperature measurement method of a bimetallic self-adaptive thermal resistance temperature measurement system, comprising the following steps: S1, contacting the resistance thermometer element 107 with the measured body through the heated ceramic cover 103 and the temperature measuring plate 104, so that heat is transferred to the spiral bimetallic strip 108 and the resistance thermometer element 107; S2, automatically adjusting the position of the sliding sleeve block 111 on the potential sliding rod 110 according to the displacement of the spiral bimetallic strip 108; S3, when the displacement of the sliding sleeve block 111 on the potential sliding rod 110 reaches a threshold value, triggering the reconfiguration of the bridge, so as to realize the switching of the resistance value of the bridge; S4, the signal processing unit synchronously reads the signals of the resistance thermometer element 107 and the potential sliding rod 110 and outputs the temperature; S5, when the displacement of the sliding sleeve block 111 on the potential sliding rod 110 reaches the limit displacement, the measurement circuit is disconnected. In step S4, the resistance value of the resistance thermometer element 107 is corrected by using the Callendar-Van Dusen equation and the resistance value of the potential sliding rod 110. In step S2, the deformation displacement of the spiral bimetallic strip 108 is continuously adjusted within the range of 0-4mm displacement with temperature.

[0022] The specific structure of the spiral bimetallic strip 108: the spiral bimetallic strip 108 is a 2mm wide and 0.2mm thick bimetallic strip coiled into 4 turns, with an outer diameter of ϕ10mm and a free length of 40mm. A Pt100 platinum resistance wire φ0.05mm is wound on the outer surface of the bimetallic strip with a 1mm pitch and fixed with high-temperature glass glaze. The bimetallic strip has a bending displacement of 0-4mm at 0-1000℃, which matches the stroke of the conductive sliding section of the potential sliding rod 110 and the sliding sleeve block 111.

[0023] Range switching: when the temperature is ≤400℃, the free end of the bimetallic strip has a displacement of less than 1.2mm, and the contacts of the range switching switch K1 remain disconnected; when T>400℃, the displacement is >1.2mm, the contacts are pressed, the 1kΩ voltage division network is switched in, and the sensitivity is reduced to prevent signal saturation.

[0024] As Figure 4As shown, temperature detection and bridge output formation, Pt100 is a bridge arm, its resistance rises with temperature, bridge power supply from 2.5V precision reference voltage V REF Provided, high stability, initial equilibrium state:

[0025] When the temperature changes → R Pt Changes → bridge imbalance → differential voltage ΔV B .

[0026] Differential amplification and signal output: INA333 sampling bridge diagonal ΔV B : input from the intersection of R2 and R; the input end is connected in parallel with a potential slide bar 110 (the potential slide bar 110 and the conductive sliding section of the sliding sleeve block 111 together constitute) to ground. INA amplifies this small voltage and outputs it to the MCU for subsequent digital processing.

[0027] The role of variable compensation resistance (the potential slide bar 110 and the conductive sliding section of the sliding sleeve block 111 together constitute): the resistance connected in parallel between the INA333 input and ground is a variable compensation resistance driven by the deformation of the spiral bimetallic strip 108, and the sliding sleeve block 111 slides on the conductive sliding section of the potential slide bar 110. Its function is: in the low temperature section: Pt100 resistance change is small → ΔV B Weak; At this time, the compensation resistance value is larger, which improves the degree of imbalance of the bridge and improves the output sensitivity; in the high temperature section: Pt100 resistance change is large → ΔV B Too big; At this time, the compensation resistance gradually decreases, limiting the INA negative input, avoiding output saturation; equivalent to forming a dynamic zero point trimming and dynamic response range voltage control, which belongs to a pure physical-mechanical self-adaptive linearization mechanism.

[0028] The role of range switching switch K1 (high temperature self-adaptation): K1 is a mechanical contact that changes action with temperature (controlled by the spiral bimetallic strip 108, specifically, the sliding sleeve block 111 slides on the conductive sliding section of the potential slide bar 110, when it slides to a set value, the voltage across the conductive sliding section of the potential slide bar 110 reaches the set value, at this time the relay coil of K1 has enough voltage to start (the relay coil is connected in parallel with the conductive sliding section of the potential slide bar 110), so that K1 can be closed); When the temperature reaches a certain threshold (such as ≥400℃), it is closed, and the positive input of INA is pulled down through the voltage divider; The effect is to reduce the common-mode input level; Equivalent to the input dynamic range of INA333 is compressed; suppresses excessive signal amplification in the high temperature section, preventing the amplifier from saturating.

[0029] Over-temperature protection: This component is a thermal cutout, connected in series above the Pt100 power supply, which automatically trips and disconnects the power supply when the temperature exceeds the design limit (e.g., 1050°C): no voltage on the bridge → ΔV = 0 B The INA333 output drops sharply, and the MCU can quickly determine that the sensor is overheating / abnormal; avoid Pt100 damage due to overheating. Automatically reset after cooling down, no need for electronic participation, achieve passive protection.

[0030] MCU processing logic: MCU collects INA333 analog output signal, processes as follows: sampling + calculating temperature (based on ΔV B → R Pt derivation; use Callendar-Van Dusen equation or lookup table algorithm); determine the range interval (can detect the conduction state of K1 or ΔV B threshold switches different gain curves); linearization / compensation calculation (can record the voltage / resistance of R var sliding changes → compensate for temperature drift / non-linearity); abnormal protection judgment (if INA output is too low (<0.05V), or completely lost signal → determine Cutoff action → alarm or cut off system load).

Claims

1. A bimetallic self-adapting thermal resistance temperature measurement system, characterized in that: It includes a signal processing unit, a spiral bimetallic strip (108), and a resistance thermometer element (107). The spiral bimetallic strip (108) is formed by welding a first metal layer and a second metal layer along the length direction and then rolling them together. The resistance thermometer element (107) is coaxially attached to the spiral bimetallic strip (108) and wound together. It also includes a mechanical displacement conversion mechanism, which is used to convert the deformation displacement of the helical bimetallic strip (108) into a sliding displacement along the potential sliding rod (110); The signal processing unit includes a bridge circuit, a differential amplifier, and a microcontroller; The spiral bimetallic strip (108) is spirally arranged on the outside of the spiral bimetallic strip guide post (106), and the spiral bimetallic strip guide post (106) is fixed on the temperature measuring plate (104). The bottom end of the potential sliding rod (110) is fixed to the temperature measuring plate (104), and the bottom end of the spiral bimetallic strip (108) is fixed to the potential sliding rod (110) and the temperature measuring plate (104) through the bottom fixing block (109). The top end of the spiral bimetallic strip (108) is fixed with a sliding sleeve block (111), and the sliding sleeve block (111) is slidably sleeved on the outer surface of the potential sliding rod (110). The outer surface of the potential sliding rod (110) is provided with a conductive sliding section that is conductively slidably engaged with the sliding sleeve (111) to switch the bridge resistance value and disconnect the circuit of the resistance thermometer element (107) when the temperature exceeds the limit. The outer side of the spiral bimetallic guide post (106) is fitted with a heated ceramic cover (103), which allows the spiral bimetallic strip (108) to freely extend and retract between the spiral bimetallic guide post (106) and the heated ceramic cover (103).

2. The bimetallic self-adapting thermal resistance temperature measurement system according to claim 1, characterized in that: a linear expansion coefficient of the first metal layer a linear expansion coefficient of the second metal layer .

3. The bimetallic adaptive resistance temperature measurement system according to claim 1, characterized in that: The resistance thermometer element (107) is a Pt 100 grade platinum resistance, temperature measurement range .

4. The bimetallic self-adapting thermal resistance temperature measurement system according to claim 1, characterized in that: A measuring arm (101) is fixedly installed on the heated ceramic cover (103) via a connecting ceramic plate (102). The heated ceramic cover (103) is fixedly fitted with the temperature measuring plate (104). A lead wire channel (105) is provided at the axial position of the measuring arm (101). The lead wire channel (105) is used for threading wires to lead out the electrical signals of the resistance thermometer element (107) and the potential sliding rod (110).

5. The bimetallic adaptive resistance temperature measurement system according to claim 1, characterized in that: The resistance of the sliding conductive section of the potential sliding rod (110) and the sliding sleeve block (111) is The stroke is matched with the displacement of the helical bimetallic strip (108).

6. The bimetallic self-adapting thermal resistance temperature measurement system according to claim 1, wherein: The signal processing unit also acquires the output of the resistance thermometer element (107) for real-time correction of the drift of the resistance thermometer element (107).

7. A temperature measuring method using the bimetallic self-adapting thermal resistance temperature measuring system according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1. The resistance thermometer element (107) is brought into contact with the object being measured through the heated ceramic cover (103) and the temperature measuring plate (104), so that heat is transferred to the spiral bimetallic strip (108) and the resistance thermometer element (107). S2. The position of the sliding sleeve block (111) on the potential sliding rod (110) is automatically adjusted according to the displacement of the spiral bimetallic strip (108); S3. When the displacement of the sliding sleeve (111) on the potential sliding rod (110) reaches the threshold, the bridge is reconfigured to switch the bridge resistance value. S4. The signal processing unit synchronously reads the signals from the resistance thermometer element (107) and the potential slider (110) and outputs the temperature. S5. When the displacement of the sliding sleeve (111) on the potential sliding rod (110) reaches the limit displacement, the measurement circuit is disconnected.

8. The temperature measuring method of a bimetallic self-adapting thermal resistance temperature measuring system according to claim 7, characterized in that: Step S4 includes calculating the correction coefficient for the resistance of the resistance thermometer element (107) using the Callendar-Van Dusen equation and the resistance of the potential slider (110).

9. The temperature measuring method of a bimetallic self-adapting thermal resistance temperature measuring system according to claim 7, characterized in that: In step S2, the deformation displacement of the spiral bimetallic strip (108) is continuously adjusted within the displacement range of 0-4 mm with temperature.

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