Adjustable multi-point calibration device and method based on water-gas-liquid two-phase equilibrium state

Abstract

The application relates to the technical field of temperature standard devices, and discloses a kind of adjustable multi-point calibration device and method based on water gas-liquid two-phase equilibrium state, the device includes airtight cavity, pressure sensing unit, heating adjustment assembly, thermometer trap and heat exchange medium. By vacuum injection of pure water to form gas-liquid two-phase equilibrium, the reference temperature value is obtained by real-time measurement of saturated vapor pressure using the pressure sensing unit and combining the calculation module, and multi-point temperature calibration is realized. The heating adjustment assembly controls the temperature in sections, quickly switches the test points, and the thermometer trap is filled with heat exchange medium to ensure temperature consistency. The application can provide high-precision, adjustable multi-point temperature calibration, and is suitable for deviation characteristic analysis and adjustment of various thermometers.

Description

Technical Field

[0001] This invention relates to the field of temperature standard device technology, and in particular to an adjustable multi-point calibration device and method based on the water-gas-liquid two-phase equilibrium state. Background Technology

[0002] Temperature calibration is of great significance in industrial production and scientific research, its main purpose being to ensure the accuracy and reliability of measuring equipment. Currently, temperature calibration methods mainly include two types: the comparative method and the fixed-point method. The comparative method typically relies on comparing a constant temperature bath with a standard platinum resistance thermometer at multiple temperature points, while the fixed-point method uses a fixed-point device (such as the triple point of water, the melting point of zinc, etc.) as a reference temperature. These two methods each have their own characteristics in practical applications.

[0003] The comparative method requires a constant temperature bath to provide a stable temperature environment and multiple comparative measurements using a standard thermometer. Its advantage lies in its high flexibility and applicability to various temperature ranges; however, in practice, the overall efficiency is limited due to the need for point-by-point comparisons. Furthermore, the performance of the constant temperature bath and the accuracy of the standard thermometer significantly affect the results, potentially introducing some uncertainty.

[0004] The fixed-point method uses the phase transition point of a substance as a reference temperature, such as the triple point of water (0.01℃) or the melting point of a metal (e.g., the melting point of zinc 419.53℃). These fixed points have high thermodynamic accuracy. However, the fixed-point method requires the design of dedicated fixed-point devices for different temperature points, which leads to high equipment costs. Furthermore, since each fixed-point device can only provide a single temperature point, multiple devices are needed to cover a wider temperature range, further increasing the implementation difficulty and resource investment. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide an adjustable multi-point calibration device and method based on a water-gas-liquid two-phase equilibrium state. This method utilizes the one-to-one correspondence between temperature and saturated vapor pressure of pure water in a gas-liquid two-phase equilibrium state, achieving precise control of multiple temperature points by adjusting the pressure. This method not only avoids the need for frequent replacement of fixed-point devices but also enables multi-point calibration through rapid heating, thereby improving efficiency and reducing equipment complexity. Furthermore, by combining modern pressure sensors and computational models, high-precision temperature calculations can be achieved, providing an economical and efficient solution for temperature calibration.

[0006] To achieve the above objectives, the present invention provides the following technical solution: an adjustable multi-point calibration device based on a water-gas-liquid two-phase equilibrium state, comprising a sealed cavity, a pressure sensing unit, a heating and regulating component, a thermometer trap, and a heat exchange medium. A certain amount of pure water is injected into the sealed cavity, and a gas-liquid two-phase equilibrium state is formed after vacuuming. The pressure sensing unit is installed at the top of the sealed cavity and communicates with the interior of the cavity, used for real-time measurement of the saturated vapor pressure inside the cavity. The heating and regulating component is embedded at the bottom of the sealed cavity and consists of an electric heating wire and a temperature sensor, used to control temperature changes within the cavity. The thermometer trap is located at the center of the top of the sealed cavity, recessed inward to form an independent space for placing the thermometer to be calibrated. The heat exchange medium fills the thermometer trap to ensure that the temperature inside the thermometer trap remains consistent with the temperature inside the sealed cavity.

[0007] Adjustable multi-point calibration methods based on water-gas-liquid two-phase equilibrium include

[0008] The device preparation steps involve assembling the adjustable multi-point calibration device.

[0009] The initial cooling step involves placing the sealed cavity into a cooling water bath at a preset cooling temperature. Cooling preparation is considered complete when the temperature measured by the temperature sensor remains constant for a continuous first preset time period.

[0010] The multi-point calibration test procedure involves setting multiple target calibration temperatures, activating the heating and regulating component, and using a PID algorithm to automatically adjust the power of the heating wire, gradually increasing the temperature to each target calibration temperature.

[0011] The data acquisition process involves the following steps: After heating to the target calibration temperature, if the temperature sensor detects that the measured temperature remains constant for a continuous second preset time period, the temperature adjustment is considered complete. The thermometer reading is recorded as the measured temperature, and the measured pressure value output by the pressure sensor unit is also recorded. Data acquisition is then completed sequentially at each target calibration temperature.

[0012] The data comparison step involves generating a reference temperature value based on the measured pressure, and then comparing the measured temperature with the reference temperature to obtain the calibration result.

[0013] Furthermore, the sealed cavity is a cylindrical structure made of stainless steel, with a heat insulation plate at the top. Small holes in the heat insulation plate allow for the insertion of a thermometer. The pressure sensing unit is fixed to the top of the sealed cavity via a threaded connection, with its sensing end extending into the cavity and directly contacting the gas environment. The heating element in the heating control assembly is spirally embedded in the bottom of the sealed cavity and connected to an external power source via wires; the temperature sensor is embedded in the center of the heating element to monitor the temperature at the bottom of the cavity in real time. The thermometer trap is a cylindrical groove with a high thermal conductivity coating on its inner wall to enhance heat exchange efficiency. Anhydrous ethanol is used as the heat exchange medium, injected into the thermometer trap through an injection port, which is then sealed after filling.

[0014] Furthermore, the real-time pressure value collected by the pressure sensing unit is transmitted to the calculation module. The calculation module obtains the current cavity temperature based on the pressure value using a preset algorithm. The preset algorithm includes three modes: lookup table method, empirical formula method, and precise calculation method. The lookup table method retrieves the saturation temperature at the corresponding pressure by consulting international standard data, such as the steam table published by IAPWS; the empirical formula method uses the Antoine equation for calculation; and the precise calculation method uses polynomial or iterative formulas provided by the International Association for the Properties of Water and Steam to solve the problem. The calculation module outputs the corresponding temperature value according to the mode selected by the user.

[0015] Furthermore, the heating regulation component enables rapid switching between multiple temperature testing points through segmented heating. The electric heating wire is divided into several independent heating sections, each with its own power adjustment via an independent control circuit. A temperature sensor monitors the temperature at the bottom of the cavity in real time and feeds the signal back to the control circuit. When the target temperature approaches the set value, the control circuit reduces the heating power, entering a stabilization phase. During the stabilization phase, the pressure sensing unit collects the pressure value inside the cavity and outputs a reference temperature value through a calculation module.

[0016] Furthermore, the heat exchange medium within the thermometer trap transfers heat to the inner wall of the sealed cavity through natural convection. The liquid level of the heat exchange medium is adjusted via the inlet to ensure the thermometer is completely submerged. The insulation plate is made of a low thermal conductivity material with an optimized thickness to reduce heat loss while maintaining mechanical strength during thermometer insertion. A sealing ring is installed at the thermometer insertion hole to prevent gas leakage from the cavity.

[0017] Furthermore, the calibration process includes a reset phase and a multi-point testing phase. In the reset phase, the device is placed in a cold water environment to lower the internal temperature of the chamber to its initial state. In the multi-point testing phase, multiple temperature test points are set sequentially. The procedure for each test point is as follows: first, the temperature is rapidly increased to near the target temperature using the heating and regulating components; then, a stabilization phase begins. Once the pressure and temperature values ​​stabilize, the current pressure value is recorded, and the reference temperature value is calculated. Simultaneously, the reading of the thermometer to be calibrated is recorded. These steps are repeated until calibration of all test points is completed.

[0018] Furthermore, after completing multi-point tests, the calculation module generates a calibration curve, with the reference temperature value on the x-axis and the thermometer reading to be calibrated on the y-axis. The deviation characteristics of the thermometer are obtained by fitting the calibration curve, and the thermometer reading is adjusted accordingly. The calibration curve fitting method includes both linear and nonlinear fitting modes, allowing users to choose the appropriate method based on their specific needs.

[0019] Furthermore, the manufacturing process of the sealed cavity includes two key steps: inner wall polishing and sealing performance testing. The inner wall polishing combines mechanical and chemical polishing to ensure a smooth, defect-free inner surface, reducing the impact of impurities on the gas-liquid two-phase equilibrium. Sealing performance testing is performed using a high-pressure helium leak detector, with a testing pressure range covering 1.5 times the device's operating pressure to ensure reliable sealing during long-term use.

[0020] Furthermore, the installation position of the pressure sensing unit has been optimized, with its sensing end located in the central area at the top of the sealed cavity, away from the heat source of the heating and regulating components, thus avoiding the impact of local temperature fluctuations on the accuracy of pressure measurement. The signal transmission line of the pressure sensing unit uses a shielded cable, externally wrapped with a heat insulation layer to reduce the impact of external electromagnetic interference and heat conduction on signal quality.

[0021] Furthermore, the heating wire of the heating regulating component is made of nickel-chromium alloy, which has high resistivity and high-temperature resistance. A PT100 platinum resistance thermometer is used for the temperature sensor, with its sensing end in close contact with the heating wire to ensure accurate temperature measurement. The control circuit employs a PID control algorithm to achieve precise temperature control by adjusting the heating power in real time.

[0022] Furthermore, the thermometer trap design considered a balance between heat exchange efficiency and mechanical strength. The groove depth was calculated and optimized to ensure full contact between the thermometer and the heat exchange medium after insertion, while avoiding excessive depth that could reduce structural strength. The thickness and material selection of the insulation plate comprehensively considered thermal conductivity, mechanical strength, and processing difficulty, ultimately determining it to be a polyimide composite material.

[0023] Furthermore, the temperature stability of the cold water environment is monitored and adjusted in real time by the temperature control unit to ensure temperature consistency during the reset phase.

[0024] Furthermore, the vacuuming operation of the sealed cavity is completed using a vacuum pump, and the vacuuming process is divided into two stages: roughing and fine evacuation. The roughing stage uses a rotary vane vacuum pump to reduce the pressure inside the cavity to below 100 Pa; the fine evacuation stage uses a molecular pump to further reduce the pressure to below 1 Pa. After vacuuming is completed, precisely measured pure water is injected into the cavity using a micro-syringe to ensure that the liquid volume ratio in the gas-liquid two-phase equilibrium state meets the design requirements.

[0025] The beneficial effects of this invention are:

[0026] 1. This device uses the strict correlation between the saturated vapor pressure and temperature of pure water as its core calibration benchmark. Through the vapor gauge or polynomial formula published by the international standard IAPWS, pressure measurements can be directly converted into highly reliable reference temperature values. Compared to traditional constant temperature baths or blackbody furnace calibration methods, it avoids the influence of uneven heat field distribution or emissivity errors, resulting in high theoretical calibration accuracy. It is particularly suitable for the calibration requirements of high-precision temperature sensors. The device employs segmented independent heating technology, achieving rapid switching and stable maintenance of the target temperature through the coordinated control of multiple nickel-chromium alloy electric heating wires and a PID algorithm.

[0027] 2. This device supports wide-temperature range calibration, covering typical temperature requirements from biomedicine to industrial process control. By configuring different heat exchange media, such as silicone oil or molten salt, the calibration capability in the high-temperature range can be further expanded. The calibration algorithm is compatible with lookup table methods, Antoine equations, and IAPWS iterative formulas, allowing users to flexibly select the mode according to accuracy requirements.

[0028] 3. Compared to traditional calibration equipment, this device requires only a trace amount of pure water and recyclable anhydrous ethanol as the medium, thus reducing energy consumption. Its modular design, such as the standardized thermometer trap, significantly reduces maintenance costs. Furthermore, an intelligent control system can be incorporated to achieve automatic acquisition of calibration data, curve generation, and report export, facilitating analysis and use. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the overall structure of the device of the present invention;

[0030] Figure 2 This is a partial enlarged view of the heating regulation component and the thermometer trap;

[0031] Figure 3 This is a three-phase diagram of water under varying temperature and pressure conditions.

[0032] Reference numerals: 1. Sealed cavity; 2. Pressure sensing unit; 3. Heating adjustment assembly; 4. Thermometer trap; 5. Heat insulation plate; 6. Electric heating wire; 7. Temperature sensor. Detailed Implementation

[0033] 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.

[0034] It should be noted that when a component is described as "fixed to" another component, it can be directly on the other component or may have a component in between. When a component is described as "connected to" another component, it can be directly connected to the other component or may have a component in between. When a component is described as "set on" another component, it can be directly set on the other component or may have a component in between. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0036] This invention relates to an adjustable multi-point calibration device based on a gas-liquid two-phase equilibrium state, the specific implementation of which is as follows. Figure 1 This is a schematic diagram of the overall structure of the invention, showing the cylindrical design of the sealed cavity 1 and the arrangement of the top heat insulation plate 5. The sealed cavity 1 is made of stainless steel, and the inner wall is mechanically and chemically polished to ensure a smooth and defect-free surface. A heat insulation plate 5 is located at the top of the cavity. The heat insulation plate 5 is made of polyimide composite material, and its thickness is optimized to reduce heat loss while ensuring mechanical strength. A small hole is opened in the center of the heat insulation plate 5 for inserting a thermometer, and a sealing ring is installed at the hole to prevent gas leakage from the cavity. The pressure sensing unit 2 is fixed to the center of the top of the sealed cavity 1 via a threaded connection. Its sensing end extends into the cavity to directly contact the gas environment, away from the heat source area of ​​the heating and regulating component 3 to avoid the impact of local temperature fluctuations on measurement accuracy.

[0037] The heating adjustment component 3 is embedded in the bottom of the sealed cavity 1, the electric heating wire 6 is embedded in the bottom of the cavity in a spiral shape and connected to an external power source through a wire, and the temperature sensor 7 is embedded in the center of the electric heating wire 6 and connected to the control circuit. Figure 2This is a partially enlarged view of the heating adjustment assembly 3 and the thermometer trap 4, showing the spiral embedding structure of the electric heating wire 6 and the mounting position of the temperature sensor 7. The electric heating wire 6 is made of nickel-chromium alloy, which has high resistivity and high temperature resistance. The temperature sensor 7 is a PT100 platinum resistance thermometer, and its sensing end is in close contact with the electric heating wire 6 to ensure accurate temperature measurement. The control circuit uses a PID control algorithm to achieve precise temperature control by adjusting the heating power in real time. The electric heating wire 6 is divided into several independent heating sections, each of which is controlled by an independent control circuit for power adjustment, enabling rapid switching between multiple temperature test points.

[0038] The thermometer trap 4 is located at the top center of the sealed cavity 1, featuring a cylindrical groove design with a high thermal conductivity coating on its inner wall to enhance heat exchange efficiency. The inlet is used to inject the heat exchange medium, specifically anhydrous ethanol, which is sealed after filling. The groove depth of the thermometer trap 4 has been calculated and optimized to ensure full contact between the thermometer and the heat exchange medium after insertion, while avoiding excessive depth that could reduce structural strength. The heat exchange medium within the thermometer trap 4 transfers heat to the inner wall of the sealed cavity 1 through natural convection. The liquid level is adjusted via the inlet to ensure the thermometer is completely submerged in the medium. The material and thickness of the insulation plate 5 were selected after considering thermal conductivity, mechanical strength, and processing difficulty, ultimately choosing a polyimide composite material.

[0039] A certain amount of pure water is injected into the sealed chamber 1. The vacuuming operation is completed by a vacuum pump, consisting of two stages: rough evacuation and fine evacuation. In the rough evacuation stage, a rotary vane vacuum pump is used to reduce the pressure inside the chamber to below 100 Pa. In the fine evacuation stage, a molecular pump is used to further reduce the pressure to below 1 Pa. After vacuuming is completed, precisely measured pure water is injected into the chamber through a micro-syringe to ensure that the liquid volume ratio in the gas-liquid two-phase equilibrium state meets the design requirements. The sealing performance of the sealed chamber 1 is tested using a high-pressure helium leak detector, with the testing pressure range covering 1.5 times the operating pressure of the device to ensure sealing reliability during long-term use.

[0040] The calibration process includes a reset phase and a multi-point testing phase. The reset phase is achieved by immersing the sealed cavity 1 in cooling water, or alternatively by using an external water-cooling system. The cooling water temperature is controlled between 0°C and 5°C. The multi-point testing phase sequentially sets multiple temperature test points. The procedure for each test point is as follows: First, the heating regulating component 3 rapidly raises the temperature to near the target temperature, followed by a stabilization phase. When the target temperature approaches the set value, the control circuit reduces the heating power and enters a stabilization phase. After the pressure and temperature values ​​stabilize, the current pressure value is recorded, and the reference temperature value is calculated. Simultaneously, the reading of the thermometer to be calibrated is recorded. The above steps are repeated until the calibration of all test points is completed.

[0041] The real-time pressure value collected by pressure sensing unit 2 is transmitted to the calculation module. The calculation module obtains the current cavity temperature based on the pressure value using a preset algorithm. The preset algorithm includes three modes: lookup table method, empirical formula method, and precise calculation method. The lookup table method obtains the saturation temperature at the corresponding pressure by consulting international standard data such as the steam table published by IAPWS. The empirical formula method uses the Antoine equation for calculation. The precise calculation method calls polynomial or iterative formulas provided by the International Association for the Properties of Water and Steam to solve the problem. The calculation module outputs the corresponding temperature value according to the user-selected mode and generates a calibration curve. The calibration curve uses the reference temperature value as the x-axis and the reading of the thermometer to be calibrated as the y-axis. The fitting method includes both linear and nonlinear fitting modes, and the user can choose the appropriate fitting method according to actual needs.

[0042] The signal transmission line of the pressure sensing unit 2 uses a shielded cable, with an external heat insulation layer to reduce the impact of external electromagnetic interference and heat conduction on signal quality. The electric heating wire 6 and temperature sensor 7 in the heating regulation assembly 3 are connected to an external power supply and control circuit via wires. The control circuit receives the signal from the temperature sensor 7 in real time and feeds it back to the heating regulation assembly 3 to achieve precise temperature control. The heat exchange medium in the thermometer trap 4 is injected through the injection port and sealed, ensuring that the thermometer is completely immersed in the medium and maintains the same temperature as the inside of the sealed cavity 1. A sealing ring is installed at the small hole of the heat insulation plate 5 to prevent gas leakage inside the cavity and to ensure mechanical strength when the thermometer is inserted.

[0043] The manufacturing process of the sealed cavity 1 includes two key steps: inner wall polishing and sealing performance testing. The inner wall polishing combines mechanical and chemical polishing to ensure a smooth, defect-free inner surface, minimizing the impact of impurities on the gas-liquid two-phase equilibrium. Sealing performance testing is performed using a high-pressure helium leak detector, with a testing pressure range covering 1.5 times the device's operating pressure to ensure reliable sealing during long-term use. The installation position of the pressure sensing unit 2 is optimized, with its sensing end located in the top center of the sealed cavity 1, away from the heat source of the heating and regulating assembly 3, avoiding the impact of local temperature fluctuations on pressure measurement accuracy. The heating wire 6 and temperature sensor 7 of the heating and regulating assembly 3 are connected to an external power supply and control circuit via wires. The control circuit receives the signal from the temperature sensor 7 in real time and feeds it back to the heating and regulating assembly 3 for precise temperature control. The design of the thermometer trap 4 considers a balance between heat exchange efficiency and mechanical strength. The groove depth is calculated and optimized to ensure sufficient contact between the thermometer and the heat exchange medium after insertion, while avoiding excessive depth that could reduce structural strength. The material and thickness of the insulation board 5 were selected by comprehensively considering thermal conductivity, mechanical strength and processing difficulty, and finally polyimide composite material was determined.

[0044] An adjustable multi-point calibration method based on the water-gas-liquid two-phase equilibrium state includes...

[0045] The device preparation steps involve assembling the adjustable multi-point calibration device.

[0046] The initial cooling step involves placing the sealed cavity 1 into a cooling water bath at a preset cooling temperature. Cooling preparation is considered complete when the measured temperature by the temperature sensor remains constant for a continuous first preset time period.

[0047] The multi-point calibration test procedure involves setting multiple target calibration temperatures, activating the heating and regulating component, and using a PID algorithm to automatically adjust the power of the electric heating wire 6, gradually increasing the temperature to each target calibration temperature.

[0048] The data acquisition process involves the following steps: After heating to the target calibration temperature, if the temperature sensor detects that the measured temperature remains constant for a continuous second preset time period, the temperature adjustment is considered complete. The thermometer reading is recorded as the measured temperature, and the measured pressure value output by the pressure sensing unit 2 is recorded. Data acquisition is then completed sequentially at each target calibration temperature.

[0049] The data comparison step involves generating a reference temperature value based on the measured pressure, and then comparing the measured temperature with the reference temperature to obtain the calibration result.

[0050] To enable those skilled in the art to fully understand and implement this invention, the specific implementation principle of this invention is further explained below in conjunction with a specific application scenario.

[0051] In practical applications, users must first place the device in a stable experimental environment and ensure that the cold water circulation cooling system is correctly connected to the external water source. After injecting precisely measured pure water into the sealed chamber 1 using a micro-syringe, the vacuum pump is started to complete the vacuuming operation. During the coarse evacuation stage, a rotary vane vacuum pump is used to reduce the pressure inside the chamber to below 100 Pa, followed by switching to a molecular pump for fine evacuation, further reducing the pressure to below 1 Pa. This process effectively removes residual gas from the chamber, ensuring the purity of the gas-liquid two-phase equilibrium state. After vacuuming is complete, the sealing performance of the sealed chamber 1 is tested using a high-pressure helium leak detector to ensure that the calibration accuracy will not be affected by leakage during long-term use.

[0052] At the start of the reset phase, the sealed cavity 1 is immersed in cooling water. The temperature control unit monitors the cooling water temperature in real time and maintains it between 0°C and 5°C to ensure that the internal temperature of the cavity drops rapidly to its initial state. During this process, the design of the heat insulation plate 5 plays an important role; its low thermal conductivity and optimized thickness effectively reduce the impact of external heat on the internal temperature of the cavity, while ensuring the mechanical strength when the thermometer is inserted.

[0053] After entering the multi-point testing phase, the heating adjustment component 3 begins operation. The electric heating wire 6 is divided into several independent heating sections, each with its own power adjusted via an independent control circuit, enabling rapid switching between multiple temperature test points. Taking a test point with a target temperature of 37℃ as an example, the control circuit, based on the real-time signal fed back by the temperature sensor 7, uses a PID control algorithm to gradually adjust the heating power, causing the internal temperature of the cavity to quickly approach the set value. When the temperature approaches the target value, the control circuit reduces the heating power, entering a stabilization phase. At this time, the pressure sensing unit 2 collects the saturated vapor pressure inside the cavity and transmits the data to the calculation module. The calculation module calculates the current internal temperature of the cavity according to a preset algorithm (such as a lookup table method or the Antoine equation) and generates a reference temperature value. Simultaneously, the reading of the thermometer to be calibrated is recorded.

[0054] During the stabilization phase, the heat exchange medium within the thermometer trap 4 transfers heat to the inner wall of the sealed cavity 1 via natural convection, ensuring that the temperature within the thermometer trap 4 remains consistent with the temperature inside the cavity. Anhydrous ethanol is selected as the heat exchange medium, as its high thermal conductivity and chemical stability effectively improve heat exchange efficiency. The inlet design allows users to adjust the liquid level as needed, ensuring the thermometer is completely immersed in the medium and preventing measurement errors due to poor contact.

[0055] After calibrating a single test point, repeat the above steps until the calibration process for all test points is complete. The calculation module generates a calibration curve based on the recorded reference temperature value and the reading of the thermometer to be calibrated. Taking linear fitting as an example, the calculation module fits the data points using the least squares method to obtain the thermometer's deviation characteristics and adjusts the thermometer reading accordingly. If the user selects nonlinear fitting mode, the calculation module calls a more complex mathematical model to further improve the fitting accuracy.

[0056] Throughout the calibration process, the signal transmission line of pressure sensing unit 2 uses a shielded cable with an external heat insulation layer, effectively reducing the impact of external electromagnetic interference and heat conduction on signal quality. Furthermore, the inner wall of the sealed cavity 1 undergoes mechanical and chemical polishing to ensure a smooth, defect-free surface, thereby reducing the interference of impurities on the gas-liquid two-phase equilibrium state. Sealing rings are installed at the small holes of the heat insulation plate 5 to prevent gas leakage inside the cavity and to ensure mechanical strength when the thermometer is inserted.

[0057] Through the above steps, this invention achieves multi-reference point temperature calibration based on a gas-liquid two-phase equilibrium state. This method not only avoids the need for frequent replacement of fixed-point devices but also enables multi-point calibration through rapid heating, significantly improving calibration efficiency and reducing equipment complexity. Combined with modern pressure sensors and computational models, this device can achieve high-precision temperature calculations, providing an economical and efficient solution for industrial production and scientific research.

[0058] All content not described in detail in this specification is prior art known to those skilled in the art, and the model parameters of each electrical appliance are not specifically limited; conventional equipment can be used. Electrical control components not mentioned in this technical solution are prior art and are therefore not shown in the figures, nor will they be described further here.

[0059] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A device for adjustable multi-point calibration based on water vapor-liquid two-phase equilibrium state, characterized in that: The device comprises a sealed cavity (1), a pressure sensing unit (2), a heating and adjusting assembly (3), a thermometer well (4) and a heat exchange medium, The sealed cavity (1) is in a cylindrical structure and is filled with a certain amount of pure water, and a gas-liquid two-phase equilibrium state is formed after vacuumizing, The pressure sensing unit (2) is installed on the top of the sealed cavity (1) and is connected with the inside of the cavity through screw connection, and is used for measuring the saturated vapor pressure in the cavity in real time, The heating and adjusting assembly (3) is embedded in the bottom of the sealed cavity (1) and is composed of an electric heating wire (6) and a temperature sensor (7), and is used for controlling the temperature change in the cavity, The thermometer well (4) is located at the center of the top of the sealed cavity (1) and is recessed inward to form an independent space, and is used for placing a thermometer to be calibrated, The heat exchange medium is filled in the thermometer well (4) to ensure that the temperature in the thermometer well is consistent with the inside of the sealed cavity (1), After the heating and adjusting assembly is heated to the vicinity of the target temperature, and the saturated vapor pressure detected by the pressure sensing unit (2) and the temperature value detected by the thermometer tend to be stable, the current pressure value is recorded and the reference temperature value is calculated, and the value of the thermometer to be calibrated is recorded, and the above steps are repeated until the calibration of all temperature test points is completed.

2. The water vapor-liquid two-phase equilibrium state based adjustable multi-point calibration device according to claim 1, characterized in that: The sealed cavity (1) is made of stainless steel material, and a heat insulation plate (5) is arranged on the top, and a small hole is opened on the heat insulation plate (5) for inserting the thermometer, and a sealing ring is arranged at the small hole.

3. The water vapor-liquid two-phase equilibrium state based adjustable multi-point calibration device according to claim 1, wherein: The sensing end of the pressure sensing unit (2) extends to the gas environment in the sealed cavity (1), and the signal transmission line adopts a shielded cable and is wrapped with a heat insulation layer outside.

4. The water vapor-liquid two-phase equilibrium state based adjustable multi-point calibration device according to claim 1, characterized in that: The electric heating wire (6) is embedded in the bottom of the sealed cavity (1) in a spiral form and is connected with an external power supply through a wire, and the temperature sensor (7) is embedded in the center position of the electric heating wire (6) and is connected with a control circuit.

5. The water-based gas-liquid two-phase equilibrium state based adjustable multi-point calibration device according to claim 1, characterized in that: The thermometer well (4) is designed as a cylindrical groove, the inner wall is coated with a high-thermal-conductivity coating, the injection port is used for injecting a heat exchange medium, and the heat exchange medium is selected from anhydrous ethanol.

6. The water-air-liquid two-phase equilibrium state based adjustable multi-point calibration device according to claim 1, characterized in that: The device comprises a calculation module, the calculation module acquires the current cavity temperature according to the pressure value collected by the pressure sensing unit (2) through a preset algorithm, and the preset algorithm comprises a table lookup method, an empirical formula method and an accurate calculation method.

7. The water-air-liquid two-phase equilibrium state based adjustable multi-point calibration device according to claim 6, characterized in that: The table lookup method acquires the saturated temperature under the corresponding pressure by querying international standard data, the empirical formula method adopts the Antoine equation for calculation, and the accurate calculation method calls a polynomial or an iterative formula for solution.

8. The water-based gas-liquid two-phase equilibrium state based adjustable multi-point calibration device according to claim 1, characterized in that: The electric heating wire (6) of the heating and adjusting assembly (3) is divided into several independent heating sections, each section is adjusted in power through an independent control circuit, and the temperature sensor (7) monitors the temperature at the bottom of the cavity in real time and feeds back the signal to the control circuit.

9. The water vapor-liquid two-phase equilibrium state based adjustable multi-point calibration device according to claim 1, characterized in that: The calibration process comprises a reset stage and a multi-point test stage, and the reset stage is realized through a cold water circulation cooling system, and the cooling water temperature is controlled between 0℃ and 5℃.

10. The adjustable multi-point calibration method based on water vapor-liquid two-phase equilibrium state, providing the adjustable multi-point calibration device as claimed in any one of claims 1-9, characterized in that: The device comprises A device preparation step, an adjustable multi-point calibration device is assembled, An initial cooling step, the sealed cavity (1) is placed in a cooling water tank at a preset cooling temperature, and when it is detected that the measured temperature of the temperature sensor remains unchanged within a continuous first preset time, it is considered that the cooling preparation is completed, The multi-point calibration test step sets multiple target calibration temperatures, starts the heating adjusting component, and the control circuit automatically adjusts the power of the electric heating wire (6) according to the PID algorithm to gradually increase the temperature to each target calibration temperature, The data acquisition step records the reading of the thermometer to define the measured temperature when the temperature sensor detects that the measured temperature remains unchanged within a continuous second preset time length after the temperature is increased to the target calibration temperature, records the measured pressure value output by the pressure sensing unit (2), and sequentially completes the data acquisition at each target calibration temperature, The data comparison step generates a reference temperature value based on the measured pressure, compares the measured temperature with the reference temperature to obtain a calibration result.

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