Bimetal adaptive thermal resistance temperature measurement system and method

Abstract

The invention discloses a bimetallic adaptive thermal resistance temperature measurement system and method, and relates to the technical field of industrial temperature measurement. The device is composed of a spiral bimetallic strip, a Pt100 platinum resistor, a variable compensation resistor sliding mechanism, a measuring range change-over switch, a thermal circuit breaker and the like. The spiral bimetallic strip generates displacement along with the temperature and drives the sliding sleeve block to change the compensation resistance, and meanwhile, the Kswitching potential-divider network is triggered at the threshold value of 400 DEG C, so that bridge circuit gain self-adaption is achieved. After the signal is amplified by INA333, the signal is resolved by the MCU according to a Calendar-VanDuen equation, and real-time linearization and drift compensation are realized in combination with an Rvar voltage; when the temperature exceeds the limit, the thermal circuit breaker automatically cuts off bridge power supply to ensure safety. The system is compact in structure, the measuring range covers 200-1000 DEG C, and the system has the advantages of wide-temperature-range high-sensitivity measurement and passive over-temperature protection, and is suitable for accurate temperature monitoring in an extreme industrial environment.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial temperature measurement, and in particular to a bimetallic self-adaptive thermal resistor temperature measurement system and method. Background Art

[0002] In the industrial temperature measurement field, traditional platinum resistance thermometers (Pt100) are widely used due to their high linearity and excellent stability. However, existing Pt100 temperature probes mostly utilize a fixed bridge circuit and a constant-gain amplifier structure, typically limiting their operating range to −200°C–850°C. When the temperature exceeds the upper limit, they rely on MCU software to compress the gain or cut off the power supply, resulting in delayed response and unreliable protection. Furthermore, fixed-gain amplifiers are insensitive to small resistance changes at low temperatures, but are prone to over-amplification at high temperatures, causing output saturation. Nonlinear errors caused by bridge imbalance require back-end software correction, increasing the computational burden on the MCU. To address drift, traditional solutions generally rely on periodic calibration or the addition of expensive reference resistor networks, failing to achieve online, adaptive compensation. Furthermore, most probes only provide overtemperature alarms via software thresholds. If the MCU or ADC fails, this poses the risk of sensor burnout and potential safety incidents. In summary, existing technologies still suffer from limitations such as a limited measurement sensitivity range, insufficient real-time linearization, limited overtemperature protection, and weak hardware adaptability. Summary of the Invention

[0003] In order to overcome the defects of the above-mentioned prior art, the present invention provides the following technical solutions: a bimetallic adaptive thermal resistor temperature measurement system, comprising a signal processing unit, a spiral bimetallic strip and a resistance thermometer element, wherein the spiral bimetallic strip is formed by welding a first metal layer and a second metal layer along the length direction and then rolling them; the resistance thermometer element and the spiral bimetallic strip are coaxially bonded and wound; the system also includes a mechanical displacement conversion mechanism, which is used to convert the deformation displacement of the spiral bimetallic strip into a sliding displacement along the potential sliding rod; the signal processing unit includes a bridge, a differential amplifier and a microcontroller; the spiral bimetallic strip is spirally arranged on the spiral bimetallic strip lead On the outside of the guide column, the spiral bimetallic guide column is fixed on the temperature measuring plate, wherein the bottom end of the potential sliding rod is fixed to the temperature measuring plate, and the bottom end of the spiral bimetallic strip is fixed to the potential sliding rod and the temperature measuring plate through the bottom fixed block, and the top of the spiral bimetallic strip is fixed with a sliding sleeve block, and the sliding sleeve block 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 section that is conductively slidably matched with the sliding sleeve block, which is used to switch the bridge resistance and disconnect the resistance thermometer element circuit when the temperature is over-temperature; the outer side of the spiral bimetallic guide column is provided with a heated ceramic cover, and the spiral bimetallic strip can freely expand and contract between the spiral bimetallic 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 ≥13×10⁻ 6 / K.

[0005] Preferably, the resistance thermometer element is a Pt100 grade platinum resistor with a temperature measurement range of −200°C to 1000°C.

[0006] Preferably, a measuring arm rod is fixedly installed on the heated ceramic cover by connecting the ceramic disk, the heated ceramic cover is fixedly matched with the temperature measuring plate, and a lead channel is opened at the axial position of the measuring arm rod. The inside of the lead channel is used for threading wires to lead out the electrical signals of the resistance thermometer element and the potential sliding rod.

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

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

[0009] A temperature measurement method for a bimetallic adaptive thermal resistor temperature measurement system, comprising the following steps: S1. The resistance thermometer element is brought into contact with the object to be measured through the heated ceramic cover and the temperature measuring plate, so that heat is transferred to the spiral bimetallic strip and the resistance thermometer element; S2. The position of the sliding sleeve 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 on the potential sliding rod reaches a threshold, the bridge is reconfigured to switch the bridge resistance value; S4. The signal processing unit synchronously reads the signals of the resistance thermometer element and the potential sliding rod and outputs the temperature; S5. When the displacement of the sliding sleeve on the potential sliding rod reaches the limit displacement, the measurement circuit is disconnected.

[0010] Preferably, step S4 includes jointly calculating a correction coefficient for the resistance value of the resistance thermometer element using the Callendar-Van Dusen equation and the resistance value of the potential sliding rod.

[0011] Preferably, in step S2, the deformation displacement of the spiral bimetallic strip is continuously adjusted within a displacement range of 0-4 mm according to the temperature.

[0012] Compared with the prior art, the present invention has the following advantages: (1) The present invention uses a variable compensation resistor driven by a spiral bimetallic strip and a range switch K1 to achieve dual adaptation of the bridge resistance and the amplifier input dynamic range. When the temperature is below 400°C, the compensation resistor maintains a high resistance state, improves the bridge imbalance in the low temperature section, and amplifies the tiny ΔV B; When the temperature rises, the resistance decreases continuously with the displacement and triggers K1 to cut into the voltage divider network at the threshold point, actively compressing the gain and avoiding output saturation in the high temperature section. This purely mechanical-electrical coupling mechanism can maintain excellent signal-to-noise ratio and linearity in the range of −200℃-1000℃ without the intervention of the MCU, significantly expanding the effective working range of the temperature measurement system; (2) The displacement of the spiral bimetallic material of the present invention is in a one-to-one correspondence with the temperature. The displacement of the sliding sleeve on the potential sliding rod changes the compensation resistance value in real time, which is equivalent to pre-linearizing the change in the resistance value of Pt100. Combined with the micro-correction of the MCU based on the Callendar-Van Dusen equation, the overall nonlinear error can be compressed to less than half of the traditional solution, while significantly reducing the MCU computing power and storage consumption, realizing high-precision temperature solution coordinated by hardware and software; (3) The present invention connects a thermal circuit breaker in series with the Pt100 power supply circuit. When the ambient temperature exceeds the limit of 1050℃, the thermal circuit breaker automatically trips and directly cuts off the power supply of the bridge, making ΔV B The device is reset to zero and the fault is determined by the MCU. This protection is completely dependent on the material properties of the component itself, and does not require an external power supply or control signal, thus avoiding the risk of software failure and ensuring the safety of sensors and back-end equipment. After cooling, the device automatically resets and can quickly resume measurement, thereby improving system reliability and maintainability; (4) The spiral bimetallic strip, Pt100 winding body and variable resistor sliding mechanism of the present invention are coaxially integrated. The heated ceramic cover and the guide column form a protection channel, which not only provides thermal isolation above 1000°C, but also allows the bimetal to expand and contract freely. No additional induction rod or spring assembly is required, and the overall number of parts is reduced by more than 30%, thereby reducing assembly complexity and cost; (5) The present invention detects the potential sliding rod R var Voltage and K1 status, MCU can quickly identify the range and the health of the compensation resistor. When the compensation resistor is abnormally open or stuck, ΔV B -R var If the corresponding relationship deviates from the calibration curve, an alarm will be issued and a maintenance code will be recorded immediately. In normal operation, the range switching information is also used to automatically select the optimal gain table, zero point compensation and filter constant to ensure the stability of the measurement throughout the entire process. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic structural diagram of the heated ceramic cover of the present invention.

[0014] Figure 2 Schematic diagram of the internal structure of the heated ceramic cover of the present invention.

[0015] Figure 3 This is a schematic diagram of the spiral bimetallic strip structure of the present invention.

[0016] Figure 4 This is a working principle diagram of the present invention.

[0017] In the figure: 101 - measuring arm rod; 102 - connecting ceramic disk; 103 - heated ceramic cover; 104 - temperature measuring plate; 105 - lead channel; 106 - spiral bimetallic strip guide column; 107 - resistance thermometer element; 108 - spiral bimetallic strip; 109 - bottom fixing block; 110 - potential sliding rod; 111 - sliding sleeve block. DETAILED DESCRIPTION

[0018] The following is combined with Figure 1-4 , and further illustrate the technical solution of the present invention through specific implementation methods.

[0019] The present invention provides a bimetallic adaptive thermal resistor temperature measurement system, comprising a signal processing unit, a spiral bimetallic strip 108 and a resistance thermometer element 107, wherein 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; the resistance thermometer element 107 and the spiral bimetallic strip 108 are coaxially bonded and wound; the system also comprises a mechanical displacement conversion mechanism, which is used to convert the deformation displacement of the spiral bimetallic strip 108 into a sliding displacement along a potential sliding rod 110; the signal processing unit comprises an electric bridge, a differential amplifier and a microcontroller; wherein the spiral bimetallic strip 108 is spirally arranged on the outside of the spiral bimetallic strip guide column 106, and the spiral bimetallic strip guide column 106 is fixed to 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 via a bottom fixing block 109. The top of the spiral bimetallic strip 108 is fixed with a sliding sleeve 111, which slides onto 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 electrically slides with the sliding sleeve 111, which is used to switch the bridge resistance and disconnect the resistance thermometer element 107 circuit when the temperature exceeds the limit. The outer side of the spiral bimetallic strip guide column 106 is provided with a heated ceramic cover 103, which allows the spiral bimetallic strip 108 to freely expand and contract between the spiral bimetallic strip guide column 106 and the heated ceramic cover 103. The linear expansion coefficient of the first metal layer is ≤3×10⁻ 6 / K, the linear expansion coefficient of the second metal layer is ≥13×10⁻ 6 / K. The resistance thermometer element 107 is a Pt100 grade platinum resistor with a temperature measurement range of −200°C to 1000°C. A measuring arm 101 is fixedly mounted on the heated ceramic cover 103 via a connecting ceramic disk 102. The heated ceramic cover 103 is fixedly mated with the temperature measuring plate 104. A lead channel 105 is provided at the axis of the measuring arm 101. This channel is used to thread wires and lead electrical signals from the resistance thermometer element 107 and the potential sliding rod 110. The resistance of the sliding conductive mating section between the potential sliding rod 110 and the sliding sleeve 111 is 0-5 kΩ, and its travel matches the displacement of the spiral bimetallic strip 108. The signal processing unit also collects the output of the resistance thermometer element 107 to perform real-time drift correction for the resistance thermometer element 107.

[0020] A temperature measurement method for a bimetallic adaptive thermal resistor temperature measurement system includes the following steps: S1. placing a resistance thermometer element 107 in contact with a measured object through a heated ceramic cover 103 and a temperature measuring plate 104, transferring heat to a spiral bimetallic strip 108 and the resistance thermometer element 107; S2. automatically adjusting the position of a sliding sleeve 111 on a potentiometric sliding rod 110 based on the displacement of the spiral bimetallic strip 108; S3. triggering a bridge reconfiguration to switch the bridge resistance when the displacement of the sliding sleeve 111 on the potentiometric sliding rod 110 reaches a threshold; S4. a signal processing unit synchronously reading signals from the resistance thermometer element 107 and the potentiometric sliding rod 110 and outputting the temperature; S5. disconnecting the measurement circuit when the displacement of the sliding sleeve 111 on the potentiometric sliding rod 110 reaches a limit displacement. Step S4 includes calculating a correction coefficient for the resistance of the resistance thermometer element 107 using the Callendar-Van Dusen equation and the resistance of the potentiometric sliding rod 110. In step S2, the deformation displacement of the spiral bimetallic strip 108 is continuously adjusted within a displacement range of 0-4 mm according to the temperature.

[0021] The spiral bimetallic strip 108 comprises a 2mm wide, 0.2mm thick bimetallic strip wound into four turns, with an outer diameter of 10mm and a free length of 40mm. A 0.05mm diameter Pt100 platinum resistance wire is wound around the outer surface of the strip at a 1mm pitch and secured with a high-temperature glass glaze. The bimetallic strip exhibits a bending displacement of 0-4mm at temperatures between 0°C and 1000°C, matching the travel of the conductive sliding sections of the potential sliding rod 110 and the sliding sleeve 111.

[0022] Range switching: When the temperature is ≤400℃, the free end of the bimetallic plate is less than 1.2mm displaced, and the contacts of the range switching switch K1 remain disconnected; when T>400℃ and the displacement is >1.2mm, the contacts are pressed together, cutting into the 1kΩ voltage divider network to reduce sensitivity and prevent signal saturation.

[0023] like Figure 4As shown, temperature detection and bridge output are formed. Pt100 is one arm of the bridge. Its resistance increases with the increase of temperature. The bridge is powered by a 2.5V precision reference voltage V REF Provides high stability, in the initial equilibrium state: ; When the temperature changes → R Pt Change → Bridge imbalance → Generates differential voltage ΔV B .

[0024] Differential amplification and signal output: INA333 samples the ΔV at the diagonal of the bridge circuit B The input terminal is connected to the intersection of R2 and R. A potential sliding rod 110 (composed of the conductive sliding section of the potential sliding rod 110 and the sliding sleeve 111) is connected in parallel to the input terminal and grounded. The INA amplifies this tiny voltage and outputs it to the MCU for subsequent digital processing.

[0025] The function of the variable compensating resistor (composed of the conductive sliding section of the potential sliding rod 110 and the sliding sleeve 111) is as follows: This resistor, connected in parallel with the INA333− input to ground, is a variable compensating resistor driven by the deformation of the spiral bimetallic strip 108. The sliding sleeve 111 slides on the conductive sliding section of the potential sliding rod 110. Its function is: At low temperatures: the Pt100 resistance value changes little → ΔV B / Weak; at this time, the compensation resistance value is large, which increases the imbalance of the bridge and improves the output sensitivity; in the high temperature range: the Pt100 resistance value changes greatly → ΔV B Too large; at this time, the compensation resistance gradually decreases, limiting the negative input of INA to avoid output saturation; this is equivalent to forming dynamic zero point fine-tuning and dynamic response range voltage control, which is a purely physical-mechanical adaptive linearization mechanism.

[0026] The function of the range switch K1 (high temperature adaptive): K1 is a mechanical contact that moves with temperature changes (controlled by the spiral bimetallic strip 108, specifically, the sliding sleeve 111 slides on the conductive sliding section of the potential sliding rod 110. When it slides to a set value, the voltage across the conductive sliding section of the potential sliding rod 110 reaches the set value. At this time, the relay coil of K1 has enough voltage to start (the relay coil is set in parallel with the two ends of the conductive sliding section of the potential sliding rod 110), so that K1 can be closed); when the temperature reaches a certain threshold (such as ≥400℃), it is closed and the positive input end 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 being compressed; suppressing excessive amplification of the high-temperature signal to prevent amplifier saturation.

[0027] Overtemperature protection: This component is a thermal circuit breaker, connected in series above the Pt100 power supply. When the temperature exceeds the design limit (such as 1050℃), it will automatically trip and disconnect the power supply: no voltage on the bridge → ΔVB When the INA333 output drops sharply to 0, the MCU can quickly identify the sensor as overtemperature or abnormal, thus preventing Pt100 damage due to overheating. It automatically resets after cooling, without electronic intervention, achieving passive protection.

[0028] MCU processing logic: MCU collects INA333 analog output signal and performs the following processing: sampling + calculating temperature (based on ΔV B →R Pt Derivation; using the Callendar–Van Dusen equation or a lookup table algorithm); determining the range (can be determined by detecting the conduction state of K1 or ΔV B Threshold switching different gain curves); linearization / compensation calculation (can be recorded by R var Sliding voltage / resistance → compensation for temperature drift / non-linearity); abnormal protection judgment (if the INA output is too low (<0.05V), or the signal is completely lost → cutoff action is determined → alarm or system load is cut off).

Claims

1. A bimetallic adaptive thermal resistor temperature measurement system, characterized by: The invention comprises a signal processing unit, a spiral bimetallic strip (108) and a resistance thermometer element (107), wherein the spiral bimetallic strip (108) is formed by welding a first metal layer and a second metal layer along a length direction and then rolling them; the resistance thermometer element (107) and the spiral bimetallic strip (108) are coaxially laminated and wound; It also includes a mechanical displacement conversion mechanism, which is used to convert the deformation displacement of the spiral bimetallic strip (108) into a sliding displacement along the potential sliding rod (110); The signal processing unit includes a bridge, a differential amplifier, and a microcontroller; The spiral bimetallic strip (108) is spirally arranged on the outside of the spiral bimetallic strip guide column (106), and the spiral bimetallic strip guide column (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 in conductive sliding cooperation with the sliding sleeve (111) and is used to switch the bridge resistance value and disconnect the resistance thermometer element (107) circuit when the temperature is over-temperature; The outer side of the spiral bimetallic plate guide column (106) is provided with a heated ceramic cover (103), and the spiral bimetallic plate (108) can freely expand and contract between the spiral bimetallic plate guide column (106) and the heated ceramic cover (103).

2. A bimetallic adaptive thermal resistor temperature measurement system according to claim 1, characterized in that: The linear expansion coefficient of the first metal layer is ≤3×10⁻ 6 / K, the linear expansion coefficient of the second metal layer is ≥13×10⁻ 6 / K.

3. The bimetallic adaptive thermal resistor temperature measurement system according to claim 1, characterized in that: The resistance thermometer element (107) is a Pt100 grade platinum resistor with a temperature measurement range of −200° C. to 1000° C.

4. The bimetallic adaptive thermal resistor temperature measurement system according to claim 1, characterized in that: A measuring arm rod (101) is fixedly mounted on the heated ceramic cover (103) by connecting the ceramic disk (102). The heated ceramic cover (103) is fixedly matched with the temperature measuring plate (104). A lead channel (105) is opened at the axis position of the measuring arm rod (101). The lead channel (105) is used for threading wires to lead out electrical signals from the resistance thermometer element (107) and the potential sliding rod (110).

5. The bimetallic adaptive thermal resistor temperature measurement system according to claim 1, characterized in that: The resistance of the sliding conductive matching section between the potential sliding rod (110) and the sliding sleeve (111) is 0-5 kΩ, and the stroke matches the displacement of the spiral bimetallic strip (108).

6. The bimetallic adaptive thermal resistor temperature measurement system according to claim 1, characterized in that: The signal processing unit also collects the output of the resistance thermometer element (107) for real-time correction of the drift of the resistance thermometer element (107).

7. A temperature measurement method for a bimetallic adaptive thermal resistor temperature measurement system, characterized in that: The steps include: S1, the resistance thermometer element (107) is brought into contact with the object to be 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, automatically adjusting the position of the sliding sleeve (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 (111) on the potential sliding rod (110) reaches a threshold value, triggering the reconfiguration of the bridge to achieve switching of the bridge resistance value; 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 (111) on the potential sliding rod (110) reaches the limit displacement, the measuring circuit is disconnected.

8. The temperature measurement method of a bimetallic adaptive thermal resistor temperature measurement system according to claim 7, characterized in that: Step S4 includes calculating the correction coefficient of the resistance value of the resistance thermometer element (107) using the Callendar-Van Dusen equation and the resistance value of the potential sliding rod (110).

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

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