A temperature control circuit for achieving cable stability in a calorimetric system

Abstract

This invention discloses a temperature control circuit for achieving cable stability in a calorimetric system, comprising a voltage regulator circuit, a temperature measuring circuit, a temperature setting circuit, and an execution circuit. The power supply output terminal of the voltage regulator circuit is connected to the power supply input terminal of the temperature measuring circuit, which in turn is connected to the power supply input terminal of the temperature setting circuit. The signal output terminals of the temperature measuring circuit and the temperature setting circuit are connected to the signal input terminal of the execution circuit. The execution circuit receives a temperature detection voltage signal and a reference temperature voltage signal, compares the error, and adjusts it using a PI controller before outputting a drive signal to control the heating power of the heating element. This invention utilizes a dynamically adjusted environmental disturbance coefficient to accurately offset the interference of ambient temperature fluctuations on the measurement end face temperature. Simultaneously, the aging attenuation coefficient of the heating element adapts in real-time to changes in element performance, ensuring stable heating power.

Description

Technical Field

[0001] This invention relates to the field of temperature control circuit technology, specifically to a temperature control circuit for achieving cable stability in a calorimetric system. Background Technology

[0002] In the field of calorimetry systems, precise temperature control is crucial for ensuring the accuracy and reliability of measurement results. The calorimetric process is highly susceptible to interference from various factors, causing temperature fluctuations at the measurement end face, which in turn severely affects the accuracy of calorimetry.

[0003] On the one hand, the ambient temperature is constantly changing, and this change affects the calorimetric system through heat conduction and convection. For example, in industrial production sites, the heat generated by large equipment can alter the local ambient temperature. If the calorimetric system does not employ effective temperature control measures, the temperature of the measuring end face will fluctuate accordingly, causing deviations in the calorimetric results. Simultaneously, the heat generated by the internal electronic components of the instrument itself during operation, as well as the Joule heat generated by the connecting cables during signal transmission, can also interfere with the temperature of the measuring end face. Some high-precision calorimeters have complex internal circuits with numerous chips operating simultaneously, accumulating significant heat. If this heat is not properly managed, it can be conducted to the measuring end face, leading to a sharp increase in measurement error.

[0004] Traditional temperature control algorithms, such as the classic PI (Proportional-Integral) algorithm, have revealed numerous drawbacks in calorimetric system applications. They struggle to effectively compensate for environmental disturbances, failing to adjust control strategies promptly when ambient temperature changes rapidly, causing the measured end-face temperature to deviate from the target value. Regarding heating element aging, traditional PI algorithms lack adaptability. As heating elements age, their performance degrades, and heating efficiency decreases, but the PI algorithm cannot automatically adjust the drive voltage to maintain heating power, severely impacting temperature control stability. In terms of temperature overshoot, traditional PI algorithms lack the ability to predict temperature change trends, failing to reduce heating power in advance when the temperature approaches the target value, leading to frequent temperature overshoot and further reducing the accuracy of the calorimetric system. Therefore, a temperature control circuit that ensures cable stability in calorimetric systems is needed. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a temperature control circuit for achieving cable stability in a calorimetric system, which can effectively solve the problems mentioned in the background art.

[0006] This invention includes a voltage regulator circuit, a temperature measuring circuit, a temperature setting circuit, and an execution circuit; the power supply output terminal of the voltage regulator circuit is connected to the power supply input terminal of the temperature measuring circuit, and the power supply input terminal of the temperature setting circuit, respectively.

[0007] The signal output terminal of the temperature measuring circuit and the signal output terminal of the temperature setting circuit are respectively connected to the signal input terminal of the execution circuit.

[0008] The temperature measuring circuit is used to convert the temperature of the measuring end face into a temperature detection voltage signal;

[0009] The temperature setting circuit is used to output a reference temperature voltage signal;

[0010] The execution circuit includes an error comparison submodule, a PI adjustment submodule, and a power drive submodule, which are electrically connected in sequence. The execution circuit receives a temperature detection voltage signal and a reference temperature voltage signal, and outputs a drive signal after passing through error comparison and PI adjustment in sequence to control the heating power of the heating element and stabilize the temperature of the measuring end face at a constant level slightly higher than the highest value of room temperature. The PI adjustment is used to eliminate static temperature control error and calorific value fluctuation through an operational amplifier and a feedback network.

[0011] Furthermore, the voltage regulator circuit includes a first resistor (R1) and a voltage regulator chip (Z1); the first end of the first resistor (R1) is connected to a positive power supply, and the second end of the first resistor (R1) is connected to the first end of the voltage regulator chip (Z1); the second and fourth ends of the voltage regulator chip (Z1) are both grounded, and the third end of the voltage regulator chip (Z1) is connected to a positive power supply; the voltage regulator chip (Z1) is model LM399.

[0012] Further, the temperature measuring circuit includes a second resistor (R2), a temperature-sensing resistor (Rt), and a first operational amplifier (U1); the first terminal of the second resistor (R2) is connected to the second terminal of the first resistor (R1) and the first terminal of the voltage regulator chip (Z1) in the voltage regulator circuit, respectively; the second terminal of the second resistor (R2) is connected to the first terminal of the first operational amplifier (U1) and the first terminal of the temperature-sensing resistor (Rt), respectively; the second terminal of the temperature-sensing resistor (Rt) is connected to the fourth terminal of the first operational amplifier (U1); the second terminal of the first operational amplifier (U1) is grounded, the third terminal of the first operational amplifier (U1) is connected to a positive power supply, and the fifth terminal of the first operational amplifier (U1) is connected to a negative power supply; the temperature-sensing resistor (Rt) is a PT100 platinum resistance thermometer, and the second resistor (R2) is used as a constant current source to convert the temperature signal into a voltage signal.

[0013] Furthermore, the temperature setting circuit includes a third resistor (R3), a potentiometer (P1), and a fourth resistor (R4); the first end of the third resistor (R3) is connected to the second end of the first resistor (R1) in the voltage regulator circuit, the first end of the voltage regulator chip (Z1), and the first end of the second resistor (R2) in the temperature measuring circuit, respectively; the second end of the third resistor (R3) is connected to the third end of the potentiometer (P1); the first end of the potentiometer (P1) is connected to the first end of the fourth resistor (R4); and the second end of the fourth resistor (R4) is connected to the execution circuit.

[0014] Further, the error comparison submodule includes a fifth resistor (R5), a sixth resistor (R6), and a second operational amplifier (U2); the PI adjustment submodule includes a seventh resistor (R7), a third capacitor (C3), a fourth capacitor (C4), an eighth resistor (R8), and a third operational amplifier (U3); the power drive submodule includes a ninth resistor (R9), a field-effect transistor (Q1), and a heating resistor (Rh). The first terminal of the fifth resistor (R5) is connected to the fourth terminal of the first operational amplifier (U1) and the second terminal of the temperature-sensing resistor (Rt) in the temperature-sensing circuit, respectively. The second terminal of the fifth resistor (R5) is connected to the... In the temperature setting circuit, the second terminal of the fourth resistor (R4), the first terminal of the sixth resistor (R6), and the first terminal of the second operational amplifier (U2) are connected; the second terminal of the second operational amplifier (U2) is grounded; the third terminal of the second operational amplifier is connected to the positive power supply and the first terminal of the second capacitor (C2) respectively; the fifth terminal of the second operational amplifier is connected to the negative power supply and the first terminal of the first capacitor (C1) respectively; the fourth terminal of the second operational amplifier (U2) is connected to the second terminal of the sixth resistor (R6); and the second terminals of the first capacitor (C1) and the second terminal of the second capacitor (C2) are both grounded.

[0015] The first terminal of the seventh resistor (R7) is connected to the second terminal of the sixth resistor (R6) and the fourth terminal of the second operational amplifier (U2) in the error comparison submodule. The second terminal of the seventh resistor (R7) is connected to the first terminal of the third operational amplifier (U3) and the first terminal of the third capacitor (C3). The second terminal of the third capacitor (C3) is connected to the first terminal of the fourth capacitor (C4). The second terminal of the fourth capacitor (C4) is connected to the first terminal of the eighth resistor (R8). The second terminal of the eighth resistor (R8) is connected to the fourth terminal of the third operational amplifier (U3). The second terminal of the third operational amplifier (U3) is grounded, the third terminal is connected to a positive power supply, and the fifth terminal is connected to a negative power supply.

[0016] The first terminal of the ninth resistor (R9) is connected to the second terminal of the eighth resistor (R8) in the PI adjustment submodule and the fourth terminal of the third operational amplifier (U3). The second terminal of the ninth resistor (R9) is connected to the gate of the field-effect transistor (Q1). The source of the field-effect transistor (Q1) is grounded, and the drain of the field-effect transistor (Q1) is connected to the second terminal of the heating resistor (Rh). The first terminal of the heating resistor (Rh) is connected to a positive power supply.

[0017] On the other hand, a temperature control method for achieving cable stability in a calorimetric system includes the following steps:

[0018] S1. The target temperature value is preset through the temperature setting circuit;

[0019] S2. Construct a dual-path temperature acquisition link:

[0020] The real-time temperature T of the measuring end face is collected using the main temperature sensing element. m (t); The ambient real-time temperature T is simultaneously collected by an auxiliary temperature sensing element. env (t), which serves as the basic parameter for environmental disturbance compensation;

[0021] S3. Calculate the compensated temperature error to eliminate the interference of environmental disturbances on the error signal. The formula is:

[0022]

[0023] Among them, T ref Set a value for the target, T m (t) represents the real-time temperature of the measured end face, T env (t) represents the real-time ambient temperature, k dist (t) represents the environmental disturbance coefficient. When the real-time ambient temperature is greater than the target set value, the environmental disturbance coefficient will weaken the negative error; when the real-time ambient temperature is less than the target set value, the environmental disturbance coefficient will strengthen the positive error.

[0024] S4. Execute time-varying attenuation adaptive PI-D regulation: Based on the compensated temperature error, the final drive voltage is calculated using the formula based on the compensated error and the aging attenuation coefficient of the heating resistor. The formula is as follows:

[0025]

[0026] Where α(t) is the aging decay coefficient, K d To predict the differential gain, K is the integral term. p Based on the proportional gain, K i Based on the integral gain.

[0027] S5. Implement power limiting and closed-loop control:

[0028] Limit the driving voltage: when u drv (t)>u max The maximum drive voltage u of the output MOSFET max , when u drv (t) < minimum drive voltage u of the field-effect transistor min Output u min Otherwise, the original calculated value is maintained; the limited drive voltage is output to the power actuator to adjust the power of the heating device, and continuous feedback is provided through the temperature acquisition link until the temperature of the measuring end face stabilizes within the preset range.

[0029] The temperature control logic formula is converted into a frequency domain transfer function using the Laplace transform, and the formula is as follows:

[0030]

[0031] Where s is the Laplace operator, α is the aging coefficient, and k dist (t) represents the disturbance coefficient; when there is no environmental disturbance and the component is not aging, the transfer function degenerates into the traditional PI-D model; when there is environmental disturbance or component aging, the transfer function dynamically adjusts the gain.

[0032] Compared with the prior art, the embodiments of the present invention have at least the following beneficial effects:

[0033] (1) The present invention utilizes a dynamically adjusted environmental disturbance coefficient to accurately offset the interference of environmental temperature fluctuations on the measurement end face temperature, while the aging attenuation coefficient of the heating element is adapted to the changes in element performance in real time to ensure stable heating power.

[0034] (2) This invention effectively addresses the problem of cable heating hysteresis, avoiding delays and overshoot in temperature regulation. The environmental disturbance compensation term senses and counteracts the impact of ambient temperature changes on the measurement end face in real time, ensuring stable operation of the calorimetric system even in complex and variable environments. Whether in the high-temperature environment of industrial production workshops or the low-temperature environment of laboratories, this invention can accurately adapt to provide stable and reliable temperature control for the calorimetric system, powerfully promoting the efficient application of calorimetric technology in different scenarios. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the circuit diagram of the present invention; Detailed Implementation

[0036] 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.

[0037] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0038] Reference Figure 1 The preferred embodiment of this invention provides a simple temperature control circuit for achieving "thermal ground", including a voltage regulator circuit, a temperature measuring circuit, a temperature setting circuit, and an execution circuit. The voltage regulator circuit is electrically connected to the temperature measuring circuit and the temperature setting circuit, and the temperature measuring circuit and the temperature setting circuit are electrically connected to the execution circuit.

[0039] The voltage regulator circuit includes a first resistor and a voltage regulator chip. The first terminal of the first resistor is connected to a positive power supply, the second terminal of the first resistor is connected to the first terminal of the voltage regulator chip, the second terminal of the voltage regulator chip is grounded, the third terminal of the voltage regulator chip is connected to a positive power supply, and the fourth terminal of the voltage regulator chip is grounded.

[0040] The temperature measuring circuit includes a second resistor, a temperature measuring resistor, and a first operational amplifier. The first end of the second resistor is connected to the second end of the first resistor and the first end of the voltage regulator chip. The second end of the second resistor is connected to the first end of the first operational amplifier and the first end of the temperature measuring resistor. The second end of the temperature measuring resistor is connected to the fourth end of the first operational amplifier. The second end of the first operational amplifier is grounded. The third end of the first operational amplifier is connected to a positive power supply. The fifth end of the first operational amplifier is connected to a negative power supply.

[0041] The temperature setting circuit includes a third resistor, a potentiometer, and a fourth resistor. The first terminal of the third resistor is connected to the second terminal of the first resistor, the first terminal of the voltage regulator chip, and the first terminal of the second resistor. The second terminal of the third resistor is connected to the third terminal of the potentiometer, and the first terminal of the potentiometer is connected to the first terminal of the fourth resistor.

[0042] The execution circuit includes a fifth resistor, a sixth resistor, a first capacitor, a second capacitor, and a second operational amplifier. The first terminal of the fifth resistor is connected to the fourth terminal of the first operational amplifier and the second terminal of the temperature sensing resistor. The second terminal of the fifth resistor is connected to the second terminal of the fourth resistor, the first terminal of the second operational amplifier, and the first terminal of the sixth resistor. The second terminal of the sixth resistor is connected to the fourth terminal of the second operational amplifier. The second terminal of the second operational amplifier is grounded. The third terminal of the second operational amplifier is connected to a positive power supply and the first terminal of the second capacitor. The fifth terminal of the second operational amplifier is connected to a negative power supply and the first terminal of the first capacitor. The second terminal of the first capacitor is grounded, and the second terminal of the second capacitor is grounded.

[0043] The execution circuit further includes a seventh resistor, a third capacitor, a fourth capacitor, an eighth resistor, and a third operational amplifier. The first terminal of the seventh resistor is connected to the second terminal of the sixth resistor and the fourth terminal of the second operational amplifier. The second terminal of the seventh resistor is connected to the first terminal of the third operational amplifier and the first terminal of the third capacitor. The second terminal of the third capacitor is connected to the first terminal of the fourth capacitor, and the second terminal of the fourth capacitor is connected to the first terminal of the eighth resistor. The second terminal of the eighth resistor is connected to the fourth terminal of the third operational amplifier. The second terminal of the third operational amplifier is grounded. The third terminal of the third operational amplifier is connected to a positive power supply, and the fifth terminal of the third operational amplifier is connected to a negative power supply.

[0044] The execution circuit also includes a ninth resistor, a field-effect transistor, and a heating resistor. The first end of the ninth resistor is connected to the second end of the eighth resistor and the fourth end of the third operational amplifier. The second end of the ninth resistor is connected to the gate of the field-effect transistor. The source of the field-effect transistor is grounded. The drain of the field-effect transistor is connected to the second end of the heating resistor. The first end of the heating resistor is connected to a positive power supply.

[0045] In this embodiment, the resistors used have an accuracy of 0.1%, and the capacitors have an accuracy of 20%.

[0046] In this embodiment, the first terminal of the voltage regulator chip Z1LM399 is connected to the second terminal of R1, the second terminal of the voltage regulator chip Z1LM399 is grounded, the third terminal of the voltage regulator chip Z1LM399 is connected to a 15V power supply, and the fourth terminal of the voltage regulator chip Z1LM399 is grounded. The first terminal of R1 is connected to a 15V power supply.

[0047] The first terminal of R2 is connected to the second terminal of R1, the first terminal of the voltage regulator chip Z1LM399, the first terminal of R3, the second terminal of R2 is connected to the first terminal of the first operational amplifier Op-Amp1.1, the first terminal of the temperature sensing resistor Rt, the second terminal of R3 is connected to the third terminal of potentiometer P1, the second terminal of potentiometer P1 is connected to the third terminal of potentiometer P1, the first terminal of potentiometer P1 is connected to the first terminal of R4, the second terminal of the first operational amplifier Op-Amp1.1 is grounded, the third terminal of the first operational amplifier Op-Amp1.1 is connected to a +15V power supply, the fourth terminal of the first operational amplifier Op-Amp1.1 is connected to the second terminal of the temperature sensing resistor Rt, and the fifth terminal of the first operational amplifier Op-Amp1.1 is connected to a -15V power supply.

[0048] The first terminal of R5 is connected to the fourth terminal of the first operational amplifier Op-Amp1.1 and the second terminal of the temperature sensing resistor Rt. The second terminal of R5 is connected to the second terminal of R4, the first terminal of R6, and the first terminal of the second operational amplifier Op-Amp2.1. The second terminal of the second operational amplifier Op-Amp2.1 is grounded. The third terminal of the second operational amplifier Op-Amp2.1 is connected to the first terminal of C2 and the +15V power supply. The fourth terminal of the second operational amplifier Op-Amp2.1 is connected to the second terminal of R6. The fifth terminal of the second operational amplifier Op-Amp2.1 is connected to the first terminal of C1 and the -15V power supply. The second terminal of C1 is grounded, and the second terminal of C2 is grounded.

[0049] The first terminal of R7 is connected to the second terminal of R6 and the fourth terminal of the second operational amplifier Op-Amp2.1. The second terminal of R7 is connected to the first terminal of C3 and the first terminal of the third operational amplifier Op-Amp3.1. The second terminal of C3 is connected to the first terminal of C4. The second terminal of C4 is connected to the first terminal of R8. The second terminal of the third operational amplifier Op-Amp3.1 is grounded. The third terminal of the third operational amplifier Op-Amp3.1 is connected to a +15V power supply. The fourth terminal of the third operational amplifier Op-Amp3.1 is connected to a -15V power supply. The fifth terminal of the third operational amplifier Op-Amp3.1 is connected to the second terminal of R8 and the first terminal of R9. The second terminal of R9 is connected to the gate of the field-effect transistor IRF620. The source of IRF620 is grounded. The drain of IRF620 is connected to the second terminal of the heating resistor Rh. The first terminal of the heating resistor Rh is connected to a +18V power supply.

[0050] Capacitors C1 and C2 are used to filter DC, the IRF620 MOSFET is the regulating transistor, resistor R1 and the LM399 voltage regulator chip are used to form a highly stable reference voltage, and the Op-Amp1.1 operational amplifier, which can stabilize the output voltage, is used to effectively reduce voltage ripple on the load. R9 is a protection resistor.

[0051] Resistor R2 serves as a constant current source, and platinum resistance thermometer Rt serves as a temperature sensor. Together, they convert the temperature signal to be detected into an electrical signal equal to the voltage across the platinum resistance thermometer. Resistors R3 and R4, along with potentiometer P1, are used to set the reference temperature for the temperature control circuit. Adjusting the resistance of potentiometer P1 in the circuit regulates the reference temperature; a higher resistance corresponds to a higher reference temperature. Resistors R3 and R4 act as a voltage divider, limiting the voltage range of potentiometer P1 for fine-tuning.

[0052] The first capacitor (C1) and the second capacitor (C2) are used to filter out DC interference. The second operational amplifier (U2), the fifth resistor (R5), and the sixth resistor (R6) form an amplification circuit to compare and amplify the difference between the temperature detection voltage signal and the reference temperature voltage signal.

[0053] The third capacitor (C3) and the fourth capacitor (C4) are connected in series to form an equivalent capacitor (Ceq). The eighth resistor (R8) and the seventh resistor (R7) form a proportional circuit. The equivalent capacitor (Ceq) and the seventh resistor (R7) form an integral circuit, which together realize PI regulation to eliminate steady-state error.

[0054] The field-effect transistor (Q1) is model IRF620, and the ninth resistor (R9) is a protection resistor used to prevent damage to the gate of the field-effect transistor due to overcurrent.

[0055] The reference temperature can be adjusted by adjusting the resistance value of the potentiometer (P1) connected to the circuit. The third resistor (R3) and the fourth resistor (R4) are used to limit the voltage range of the potentiometer (P1) to achieve fine adjustment of the reference temperature.

[0056] Operational amplifier Op-Amp2.1, along with resistors R5 and R6, is used to compare and amplify the difference between the detected temperature and a reference temperature. The inverting input of Op-Amp2.1 consists of two signals: one is the electrical signal converted from the temperature of the measured object by the temperature-sensing resistor PT100 (negative potential); the other is the electrical signal from potentiometer P1 (positive potential). These two signals converge at the inverting input of Op-Amp2.1, thus inputting the difference between the measured and reference temperatures into Op-Amp2.1. This difference is amplified by the amplification circuit formed by Op-Amp2.1, resistors R5 and R6. The output voltage controls the voltage across resistor R7, thereby regulating subsequent circuitry. When the measured temperature is higher than the reference temperature, the output is low; when the measured temperature is lower than the reference temperature, the output is high.

[0057] S1. The target temperature value is preset through the temperature setting circuit;

[0058] S2. Construct a dual-path temperature acquisition link:

[0059] The real-time temperature T of the measuring end face is collected using the main temperature sensing element. m (t); The ambient real-time temperature T is simultaneously collected by an auxiliary temperature sensing element. env (t), which serves as the basic parameter for environmental disturbance compensation;

[0060] S3. Calculate the compensated temperature error to eliminate the interference of environmental disturbances on the error signal. The formula is:

[0061]

[0062] Among them, T ref Set a value for the target, T m (t) represents the real-time temperature of the measured end face, T env (t) represents the real-time ambient temperature, k dist (t) represents the environmental disturbance coefficient. When the real-time ambient temperature is greater than the target set value, the environmental disturbance coefficient will weaken the negative error; when the real-time ambient temperature is less than the target set value, the environmental disturbance coefficient will strengthen the positive error.

[0063] S4. Execute time-varying attenuation adaptive PI-D regulation: Based on the compensated temperature error, the final drive voltage is calculated using the formula based on the compensated error and the aging attenuation coefficient of the heating resistor. The formula is as follows:

[0064]

[0065] Where α(t) is the aging decay coefficient, K d To predict the differential gain, K is the integral term. p Based on the proportional gain, K i Based on the integral gain.

[0066] S5. Implement power limiting and closed-loop control:

[0067] Limiting of the driving voltage: When the final driving voltage u drv (t)>u max The maximum drive voltage u of the output MOSFET max When the final driving voltage u drv (t) < minimum drive voltage u of the field-effect transistor min Output u min Otherwise, the original calculated value is maintained; the limited drive voltage is output to the power actuator to adjust the power of the heating device, and continuous feedback is provided through the temperature acquisition link until the temperature of the measuring end face stabilizes within the preset range.

[0068] The temperature control logic formula is converted into a frequency domain transfer function using the Laplace transform, and the formula is as follows:

[0069]

[0070] Where s is the Laplace operator, α is the aging coefficient, and k dist (t) represents the disturbance coefficient; when there is no environmental disturbance and the component is not aging, the transfer function degenerates into the traditional PI-D model; when there is environmental disturbance or component aging, the transfer function dynamically adjusts the gain.

[0071] The main temperature measuring element is a PT100 platinum resistance thermometer, which is closely attached to the measuring end face of the calorimetry system. It is connected to the constant current source branch of the original temperature measuring circuit and connected in series with the second resistor R2. Its output is connected to the signal acquisition pin 4 of the first operational amplifier. The constant current source converts the temperature change into a voltage signal, which is then amplified by the operational amplifier and filtered by RC to output a real-time temperature electrical signal.

[0072] The auxiliary temperature sensing element is a PT100 platinum resistance thermometer of the same model, which is placed in the ventilation environment around the calorimetry system and connected in parallel to the constant current source power supply terminal of the original temperature sensing circuit. It can be connected to the first terminal of the second resistor R2. Its output terminal is connected to the spare input terminal pin 6 of the first operational amplifier. It is processed by the same RC filter network as the main temperature sensing channel to output the ambient temperature electrical signal. The spare input terminal is an unused pin of the operational amplifier in the original circuit. Connecting the auxiliary temperature sensing element does not disrupt the acquisition logic of the main temperature sensing signal.

[0073] Operational amplifier Op-Amp3.1, resistors R7 and R8, and capacitors C3 and C4 form an integrating amplifier circuit. Capacitors C3 and C4 are used for integration, eliminating steady-state error, preventing oscillation, and outputting a stable voltage signal. Resistors R7 and R8 form a proportional amplifier circuit, thereby achieving PID control. A field-effect transistor IRF620 and a heating resistor Rh output heating power to heat the object under test, thus controlling the object's temperature. Specifically, if the test temperature is higher than the reference temperature, the output voltage of operational amplifier Op-Amp3.1 is lower than the previous voltage. Therefore, the current flowing through heating resistor Rh decreases, resulting in a decrease in heating power and a decrease in the test temperature until it stabilizes at the reference temperature. Conversely, if the test temperature is lower than the reference temperature, the feedback mechanism will also stabilize the test temperature at the reference temperature. If the test temperature matches the reference temperature, the output voltage of operational amplifier Op-Amp3.1 is the same as the previous voltage. Therefore, the current flowing through heating resistor Rh remains unchanged, resulting in a constant heating power and a stable temperature at the reference temperature.

[0074] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. The selection and detailed description of these embodiments in this specification are intended to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. Any modifications or variations that do not deviate from the structure of the invention or exceed the scope defined by the invention should fall within the protection scope of the invention.

Claims

1. A temperature control circuit for achieving cable stability in a calorimetric system, characterized in that: It includes a voltage regulator circuit, a temperature measuring circuit, a temperature setting circuit, and an execution circuit; the power supply output terminal of the voltage regulator circuit is connected to the power supply input terminal of the temperature measuring circuit and the power supply input terminal of the temperature setting circuit, respectively. The signal output terminal of the temperature measuring circuit and the signal output terminal of the temperature setting circuit are respectively connected to the signal input terminal of the execution circuit. The temperature measuring circuit is used to convert the temperature of the measuring end face into a temperature detection voltage signal; The temperature setting circuit is used to output a reference temperature voltage signal; The execution circuit includes an error comparison submodule, a PI adjustment submodule, and a power drive submodule, which are electrically connected in sequence. The execution circuit receives a temperature detection voltage signal and a reference temperature voltage signal, and outputs a drive signal after passing through error comparison and PI adjustment in sequence to control the heating power of the heating element and stabilize the temperature of the measuring end face at a constant level slightly higher than the highest value of room temperature. The PI adjustment is used to eliminate static temperature control error and calorimetric fluctuations through an operational amplifier and a feedback network. The error comparison submodule includes a fifth resistor (R5), a sixth resistor (R6), and a second operational amplifier (U2); the PI adjustment submodule includes a seventh resistor (R7), a third capacitor (C3), a fourth capacitor (C4), an eighth resistor (R8), and a third operational amplifier (U3); the power drive submodule includes a ninth resistor (R9), a field-effect transistor (Q1), and a heating resistor (Rh). The first terminal of the fifth resistor (R5) is connected to the fourth terminal of the first operational amplifier (U1) and the second terminal of the temperature measuring resistor (Rt) in the temperature measuring circuit, respectively. The second terminal of the fifth resistor (R5) is connected to the temperature setpoint... The second terminal of the fourth resistor (R4), the first terminal of the sixth resistor (R6), and the first terminal of the second operational amplifier (U2) are connected; the second terminal of the second operational amplifier (U2) is grounded; the third terminal of the second operational amplifier (U2) is connected to the positive power supply and the first terminal of the second capacitor (C2) respectively; the fifth terminal of the second operational amplifier is connected to the negative power supply and the first terminal of the first capacitor (C1) respectively; the fourth terminal of the second operational amplifier (U2) is connected to the second terminal of the sixth resistor (R6); the second terminals of the first capacitor (C1) and the second terminals of the second capacitor (C2) are both grounded; The first terminal of the seventh resistor (R7) is connected to the second terminal of the sixth resistor (R6) and the fourth terminal of the second operational amplifier (U2) in the error comparison submodule. The second terminal of the seventh resistor (R7) is connected to the first terminal of the third operational amplifier (U3) and the first terminal of the third capacitor (C3). The second terminal of the third capacitor (C3) is connected to the first terminal of the fourth capacitor (C4). The second terminal of the fourth capacitor (C4) is connected to the first terminal of the eighth resistor (R8). The second terminal of the eighth resistor (R8) is connected to the fourth terminal of the third operational amplifier (U3). The second terminal of the third operational amplifier (U3) is grounded, the third terminal is connected to a positive power supply, and the fifth terminal is connected to a negative power supply. The first terminal of the ninth resistor (R9) is connected to the second terminal of the eighth resistor (R8) in the PI adjustment submodule and the fourth terminal of the third operational amplifier (U3). The second terminal of the ninth resistor (R9) is connected to the gate of the field-effect transistor (Q1). The source of the field-effect transistor (Q1) is grounded, and the drain of the field-effect transistor (Q1) is connected to the second terminal of the heating resistor (Rh). The first terminal of the heating resistor (Rh) is connected to a positive power supply.

2. The temperature control circuit according to claim 1, characterized in that, The voltage regulator circuit includes a first resistor (R1) and a voltage regulator chip (Z1); the first end of the first resistor (R1) is connected to a positive power supply, and the second end of the first resistor (R1) is connected to the first end of the voltage regulator chip (Z1); the second and fourth ends of the voltage regulator chip (Z1) are both grounded, and the third end of the voltage regulator chip (Z1) is connected to a positive power supply; the voltage regulator chip (Z1) is model LM399.

3. The temperature control circuit according to claim 1, characterized in that, The temperature measuring circuit includes a second resistor (R2), a temperature measuring resistor (Rt), and a first operational amplifier (U1). The first terminal of the second resistor (R2) is connected to the second terminal of the first resistor (R1) and the first terminal of the voltage regulator chip (Z1) in the voltage regulator circuit. The second terminal of the second resistor (R2) is connected to the first terminal of the first operational amplifier (U1) and the first terminal of the temperature measuring resistor (Rt). The second terminal of the temperature measuring resistor (Rt) is connected to the fourth terminal of the first operational amplifier (U1). The second terminal of the first operational amplifier (U1) is grounded, the third terminal of the first operational amplifier (U1) is connected to a positive power supply, and the fifth terminal of the first operational amplifier (U1) is connected to a negative power supply. The temperature measuring resistor (Rt) is a PT100 platinum resistance thermometer, and the second resistor (R2) is used as a constant current source to convert the temperature signal into a voltage signal.

4. The temperature control circuit according to claim 1, characterized in that, The temperature setting circuit includes a third resistor (R3), a potentiometer (P1), and a fourth resistor (R4). The first end of the third resistor (R3) is connected to the second end of the first resistor (R1) in the voltage regulator circuit, the first end of the voltage regulator chip (Z1), and the first end of the second resistor (R2) in the temperature measuring circuit. The second end of the third resistor (R3) is connected to the third end of the potentiometer (P1). The first end of the potentiometer (P1) is connected to the first end of the fourth resistor (R4). The second end of the fourth resistor (R4) is connected to the execution circuit.

5. A temperature control method for achieving cable stability in a calorimetric system, implemented based on the circuit described in any one of claims 1-4, characterized in that: S1. The target temperature value is preset through the temperature setting circuit; S2. Construct a dual-path temperature acquisition link: The real-time temperature of the measuring end face is collected using the main temperature sensing element. ; The ambient real-time temperature is collected synchronously by an auxiliary temperature sensing element. , serving as the basic parameter for environmental disturbance compensation; S3. Calculate the compensated temperature error to eliminate the interference of environmental disturbances on the error signal. The formula is: ； in, Set a value for the target. To measure the real-time temperature of the end face, For real-time ambient temperature, The environmental disturbance coefficient weakens negative errors when the real-time ambient temperature is greater than the target set value, and strengthens positive errors when the real-time ambient temperature is less than the target set value. S4. Execute time-varying attenuation adaptive PID control: Based on the compensated temperature error, the final drive voltage is calculated using the formula: in, For aging degradation coefficient, To predict the differential gain, For integration, Based on the proportional gain, Basic integral gain; S5. Implement power limiting and closed-loop control: Limit the driving voltage: when > Maximum drive voltage of the output MOSFET ,when Minimum drive voltage of field-effect transistor Time output Otherwise, the original calculated value is maintained; the limited drive voltage is output to the power actuator to adjust the power of the heating device, and continuous feedback is provided through the temperature acquisition link until the temperature of the measuring end face stabilizes within the preset range.

6. The temperature control method according to claim 5, characterized in that, The temperature control logic formula is converted into a frequency domain transfer function using the Laplace transform, and the formula is as follows: in, For the Laplace operator, This is the aging degradation coefficient. The disturbance coefficient is used; when there is no environmental disturbance and the component is not aging, the transfer function degenerates into the traditional PID model; when there is environmental disturbance or component aging, the transfer function dynamically adjusts the gain.

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