Lstm model based ultra-low temperature thermometer multi-mode calibration system

Abstract

The utility model discloses a super low temperature thermometer multimode calibration system based on LSTM model, including multimode constant temperature source module, maintaining liquid nitrogen liquid level height and ensuring the liquid nitrogen cold source system of stable supply, intelligent temperature control heating system and the controller of support LSTM model parallel computation. Multimode constant temperature source module is integrated double cavity, and it is equipped with two kinds of calibration cavity's heat -conducting block, and the heat -conducting block is the long rod heat -conducting block of quick replacement, short heat -conducting block, the long rod heat -conducting block is opened with the long rod calibration cavity of suitable insertion depth >= 400mm long rod thermometer, and the short heat -conducting block is opened with the short type calibration cavity of suitable insertion depth <= 300mm short type thermometer. The integrated temperature, pressure multimode data fusion algorithm carries out calibration data correction processing, and the precision of traditional single temperature parameter calibration is improved.

Description

Technical Field

[0001] This utility model relates to the field of low temperature calibration, and in particular to a multi-mode calibration system for ultra-low temperature thermometers based on an LSTM model. Background Technology

[0002] Currently, there is a lack of suitable low-temperature field standard devices for the calibration of ultra-low temperature thermometers in the biomedical field (such as -86℃ freezer monitoring and biological sample storage thermometers). Existing domestic systems are mainly used in the liquid helium temperature range of -269℃, which cannot cover the continuous calibration needs of a wide temperature range of -196℃ to -80℃. Foreign equipment, such as the British Essonne 459 cryostat, although temperature adjustable, costs as much as 300,000 yuan per unit, and the temperature range only covers -180℃ to -80℃, which cannot meet the calibration needs of the low-temperature range of -196℃ to -180℃.

[0003] In existing technologies, domestic cryogenic thermometer calibration systems are mostly used in the liquid helium temperature range. These systems are complex in structure, have high operating costs, and suffer from the problem of non-adjustable temperature. For example, the (-180~-80)℃ adjustable cryogenic thermostat developed by the Chengdu Institute of Metrology and Testing is only suitable for long-rod cryogenic thermometers and cannot meet the calibration requirements of short-rod cryogenic thermometers. The cryogenic thermometer calibration device developed by the Shanghai Institute of Metrology is only suitable for short-rod cryogenic thermometers, and its technical specifications are poor, with the uniformity of the thermostat block only achieving a value better than ±20mK and the temperature control stability ≤50mK / h. Foreign cryogenic thermostats from companies such as Essonne in the UK and Cambage in Europe are expensive, and their designs are mostly suitable for calibrating long-rod cryogenic thermometers, with poor applicability to short-rod cryogenic thermometers. In addition, some existing technologies require refrigeration units and large equipment, which are complex to install and use, have high operating and maintenance costs, and have a narrow temperature range, which cannot meet the calibration requirements of a wide temperature range of (-196 to -80)℃ with continuous adjustment. At the same time, there is a lack of relevant calibration specifications as technical guidance, making it difficult to achieve accurate traceability of ultra-low temperature thermometer values.

[0004] Limitations of long rod thermometers: The (-180 to -80)℃ thermometer described in the patented low-temperature thermostat with continuously adjustable temperature (patent number: ZL202223263681X) is only suitable for long rod thermometers with an insertion depth >400mm, and is not compatible with short probes (such as micro sensors in biobanks with a length ≤300mm).

[0005] Limitations of short thermometers: The calibration system based on GM refrigeration units only supports short thermometers, and the thermostatic block is small (insertion depth ≤ 200 mm), which cannot accommodate long rod thermometers, resulting in poor technical performance (uniformity ≤ ±20 mK, temperature control stability ≤ 50 mK / h).

[0006] Traditional systems rely on a refrigerator and a vacuum device, such as the GM refrigerator system developed by Shanghai Jiao Tong University. These systems require complex operations such as vacuuming and cold shield installation, and a single calibration takes more than 2 hours, costing more than 3 times the hardware cost.

[0007] Insufficient existing value traceability methods: Currently, there is a lack of unified calibration standards in the (-196 to -80) °C temperature range. Existing technologies mostly refer to calibration methods in the liquid helium temperature range (-269 °C) or at room temperature, without considering factors such as the latent heat of liquid nitrogen phase change and changes in low-temperature thermal conductivity, resulting in unreliable calibration results.

[0008] Current calibrations do not consider the effects of mechanical deformation and contact thermal resistance during thermometer insertion on temperature measurement. For example, different insertion depths of long-rod thermometers can lead to axial temperature field deviations of up to 50 mK, while the contact thermal resistance between short probes and heat spreaders can cause errors of ±20 mK. Utility Model Content

[0009] To solve the above-mentioned technical problems, this utility model specifically designs a multi-mode calibration system for ultra-low temperature thermometers based on an LSTM model.

[0010] The present invention adopts the following technical solution: The LSTM-based multi-mode calibration system for cryogenic thermometers includes a multi-mode constant temperature source module, a liquid nitrogen cold source system that maintains the liquid nitrogen level and ensures a stable supply of cold source, an intelligent temperature control heating system, and a controller that supports parallel computing of the LSTM model. The multi-mode constant temperature source module is an integrated dual-cavity module, which has two types of heat spreaders for calibration cavities. The heat spreaders are quick-replaceable long rod heat spreaders and short heat spreaders. The long rod heat spreader has a long rod calibration cavity adapted to long rod thermometers with an insertion depth ≥400mm, and the short heat spreader has a short calibration cavity adapted to short thermometers with an insertion depth ≤300mm. The intelligent temperature control heating system includes a surrounding heating wire, a radiation shield heating layer, and multiple sensors. The sensors include a traceability sensor composed of second-class standard platinum resistance thermometers, a temperature control sensor composed of two sets of thin-film thermocouples arranged at the center and edge of the heat spreader, and a pressure sensor embedded inside the heat spreader.

[0011] Preferably, the liquid nitrogen cooling system includes a liquid nitrogen cooling tank, a liquid nitrogen storage tank, and a liquid nitrogen pipeline. The liquid nitrogen cooling tank and the liquid nitrogen storage tank are connected by the liquid nitrogen pipeline. An electromagnetic valve is installed in the liquid nitrogen pipeline, and a float-type liquid level sensor is provided in the liquid nitrogen cooling tank. The float-type liquid level sensor is connected to the controller, and the controller is connected to the solenoid valve.

[0012] Preferably, the heat spreader is made of oxygen-free copper with a purity of ≥99.95%, with gold plating on the inner wall, a thickness of 5μm, and an emissivity of <0.02; The long rod heat spreader has a diameter of 150mm and a height of 450mm. The long rod calibration cavity has a diameter of 20mm and a depth of 430mm. The long rod calibration cavity contains 3 sets of heating wires. The short heat spreader has a diameter of 150mm and a height of 300mm. The short calibration chamber has a diameter of 15mm and a depth of 280mm. The short calibration chamber contains 3 sets of heating wires.

[0013] Long-rod heat exchangers and short-rod heat exchangers can be quickly replaced via flanges.

[0014] Preferably, the heating wire consists of 6 sets of heating wires spirally wound on the outer wall of the heat spreader, and the heating wires are 0.5mm diameter nickel-chromium alloy heating wires.

[0015] Preferably, both the long-rod heat spreader and the short-shaped heat spreader are wrapped with a radiation shield heating layer. The radiation shield heating layer is a gold-plated copper screen with a thickness of 0.1 mm and a heating film with a resistance value of 100 Ω printed on its surface.

[0016] Preferably, the traceability sensor and the thermometer to be calibrated are inserted into the calibration chamber in parallel, with a sampling rate of 1Hz.

[0017] Preferably, the pressure sensor is a fiber Bragg grating pressure sensor with a range of 0-10 MPa and a resolution of 0.1% FS.

[0018] Preferably, the controller uses a quad-core Cortex-A73 with a main frequency of 2.0GHz and is connected to an external Xilinx Alveo U50 FPGA acceleration card.

[0019] Compared with the prior art, the beneficial effects of this utility model are: This LSTM-based multi-mode calibration system for cryogenic thermometers integrates temperature and pressure multi-modal data fusion algorithms for calibration data correction, resulting in improved accuracy compared to traditional single-temperature parameter calibration. It features wide-range continuous adjustable and high-precision temperature control, a dual-chamber design, and a quick-release structure for rapid module switching. It is compatible with long-rod / short-rod cryogenic thermometers within the (-196~-80)℃ range for calibration. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of a multi-mode calibration system.

[0022] Figure 2This is a schematic diagram of a long constant temperature source module.

[0023] In the diagram: 1. Liquid level sensor, 2. Quick-connect plug, 3. Short heat spreader, 4. High vacuum Dewar flask, 5. Heating wire, 6. Radiation shield heating layer, 7. Vacuum pump, 8. Solenoid valve, 9. Short calibration chamber, 3'. Long rod heat spreader, 5'. Long rod heating wire, 6'. Long rod radiation shield heating layer, 9'. Long rod calibration chamber. Detailed Implementation

[0024] The following will refer to the appendix in the embodiments of this utility model. Figure 1-2 The technical solutions in the embodiments of this utility model will be clearly and completely described. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments.

[0025] A multi-mode calibration system for ultra-low temperature thermometers based on LSTM models, such as Figure 1-2 As shown, the calibration of an ultra-low temperature thermometer suitable for (-196 to -80)℃ based on an LSTM model consists of four core parts: a dual-chamber multi-mode constant temperature source module, a liquid nitrogen cold source system, an intelligent temperature control heating system, and a room temperature controller. The device adopts a vertical structure, with a high-vacuum Dewar flask at the bottom containing a built-in heat spreader assembly, and the controller and sensor cable interfaces connected to the top via a flange.

[0026] The multi-mode constant temperature source module adopts a dual-cavity integrated design, with two types of calibration chambers for the heat spreader. The heat spreader is made of oxygen-free copper with a purity of ≥99.95%, gold-plated inner wall, 5μm thickness, and emissivity <0.02. The long rod heat spreader 3' has a diameter of 150mm and a height of 450mm, and has a long rod calibration chamber 9' with a diameter of 20mm and a depth of 430mm. It is suitable for long rod thermometers with an insertion depth of ≥400mm, such as long rod low temperature thermometers used in cold chain transportation monitoring instruments. It has 3 sets of heating wires (nickel-chromium alloy, resistance 50Ω).

[0027] The short heat spreader 3 has a diameter of 150mm and a height of 300mm. It has a short calibration cavity 9 with a diameter of 15mm and a depth of 280mm. It uses a zoned temperature-controlled copper block and has 3 sets of heating wires (nickel-chromium alloy, resistance 50Ω). It is suitable for short thermometers with an insertion depth of ≤300mm, such as miniature sensors for biobanks.

[0028] The long-rod / short-rod module can be quickly changed using a flange (M40×1.5 thread) and quick-connect plug 2. The changeover time is less than 5 minutes, and the module contact surfaces are equipped with fluororubber cryogenic seals to prevent cold leakage.

[0029] The liquid nitrogen cooling system employs a high-vacuum Dewar flask 4 equipped with an automatic liquid nitrogen replenishment device, including a float-type liquid level sensor 1 and a solenoid valve 8. The float-type liquid level sensor 1 collects liquid level information, converting the liquid level height into a reed switch on / off signal, which is transmitted to the controller via cable. The controller controls the solenoid valve and the liquid replenishment channel through control logic. A vacuum pump is also installed on the liquid replenishment channel to create a vacuum environment to reduce heat conduction and improve the insulation effect of the constant temperature source. The liquid nitrogen level is maintained at ≥ 1.5 times the height of the heat spreader, ensuring a stable supply of -196℃ cold source.

[0030] The solenoid valve is a cryogenic, normally closed type with a DN25 diameter. It connects the high-vacuum Dewar flask and the replenishment pipeline and is sealed with fluororubber. The replenishment pipeline is a 25mm diameter stainless steel bellows wrapped with MLI insulation and has a filter at the inlet.

[0031] Intelligent temperature control heating system: Heating and temperature control consist of a surrounding heating wire 5 and a radiation shield heating layer 6. Six sets of heating wires, 0.5mm diameter nickel-chromium alloy, are spirally wound around the outer wall of the heat spreader, with a total power of 200W. Power adjustment in 0.1W increments is achieved through a solid-state relay SSR-25DA. Figure 1 As shown, the heat spreader (a short heat spreader) is wrapped with a gold-plated copper screen with a thickness of 0.1 mm. A heating film with a resistance value of 100Ω is printed on the surface, serving as the main heating layer to reduce heat radiation loss. If it is a long-rod heat spreader, it is also equipped with a long-rod heating wire 5' and a long-rod radiation shielding heating layer 6'.

[0032] A second-order standard platinum resistance thermometer (PT1000, uncertainty ≤0.015℃) and the thermometer to be calibrated were inserted in parallel into the calibration chamber, with a sampling rate of 1Hz, as traceability sensors. Two sets of thin-film thermocouples were arranged at the center and edge of the heat spreader as temperature control sensors. Simultaneously, an auxiliary sensor, i.e., a pressure sensor, was embedded inside the heat spreader to synchronously collect pressure data and correct for temperature measurement deviations. A fiber Bragg grating pressure sensor with a range of 0-10MPa and a resolution of 0.1%FS was preferred as the pressure sensor.

[0033] The controller uses a quad-core Cortex-A73 with a main frequency of 2.0GHz and is connected to an external Xilinx Alveo U50 FPGA acceleration card. It supports parallel computing of LSTM models. The control module includes a 16-channel 24-bit ADC for acquiring temperature signals, 8-channel PWM output to control heating power, and is connected to the thermostat body through a control port. The CAN bus is connected to the liquid nitrogen replenishment system.

[0034] Based on this system, the heating rate reaches 5℃ / min through the coordinated control of LSTM prediction model and segmented PID, the overshoot is reduced from 0.5℃ in traditional PID to 0.1℃, the stabilization time is shortened from 25 minutes to 15 minutes (long rod module), the calibration efficiency is improved by 40%, and the liquid nitrogen consumption rate is reduced.

[0035] An integrated multi-modal data fusion algorithm for temperature and pressure is used to correct calibration data, improving accuracy compared to traditional single-temperature parameter calibration.

[0036] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope thereof. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection of the present invention.

Claims

1. A multi-mode calibration system for ultra-low temperature thermometers based on an LSTM model, characterized in that, It includes a multi-mode constant temperature source module, a liquid nitrogen cold source system that maintains the liquid nitrogen level and ensures a stable supply of cold source, an intelligent temperature control heating system, and a controller that supports parallel computing of LSTM models; The multi-mode constant temperature source module is an integrated dual-cavity module, which has two types of heat spreaders for calibration cavities. The heat spreaders are quick-replaceable long rod heat spreaders and short heat spreaders. The long rod heat spreader has a long rod calibration cavity adapted to long rod thermometers with an insertion depth ≥400mm, and the short heat spreader has a short calibration cavity adapted to short thermometers with an insertion depth ≤300mm. The intelligent temperature control heating system includes a surrounding heating wire, a radiation shield heating layer, and multiple sensors. The sensors include a traceability sensor composed of second-class standard platinum resistance thermometers, a temperature control sensor composed of two sets of thin-film thermocouples arranged at the center and edge of the heat spreader, and a pressure sensor embedded inside the heat spreader.

2. The multi-mode calibration system for ultra-low temperature thermometers based on an LSTM model according to claim 1, characterized in that, The liquid nitrogen cooling system includes a liquid nitrogen cooling tank, a liquid nitrogen storage tank, and a liquid nitrogen pipeline. The liquid nitrogen cooling tank and the liquid nitrogen storage tank are connected by the liquid nitrogen pipeline. A solenoid valve is installed in the liquid nitrogen pipeline, and a float-type liquid level sensor is installed in the liquid nitrogen cooling tank. The float-type liquid level sensor is connected to the controller, and the controller is connected to the solenoid valve.

3. The multi-mode calibration system for ultra-low temperature thermometers based on an LSTM model according to claim 1, characterized in that, The heat spreader is made of oxygen-free copper with a purity of ≥99.95%, with gold plating on the inner wall, a thickness of 5μm, and an emissivity of <0.

02. The long rod heat spreader has a diameter of 150mm and a height of 450mm. The long rod calibration cavity has a diameter of 20mm and a depth of 430mm. The long rod calibration cavity contains 3 sets of heating wires. The short heat spreader has a diameter of 150mm and a height of 300mm. The short calibration chamber has a diameter of 15mm and a depth of 280mm. The short calibration chamber contains 3 sets of heating wires.

4. The multi-mode calibration system for ultra-low temperature thermometers based on an LSTM model according to claim 3, characterized in that, The heating wire consists of 6 sets of heating wires spirally wound on the outer wall of the heat spreader, and the heating wires are 0.5mm diameter nickel-chromium alloy heating wires.

5. The multi-mode calibration system for ultra-low temperature thermometers based on an LSTM model according to claim 3, characterized in that, Both the long-rod heat spreader and the short-rod heat spreader are wrapped with a radiation shield heating layer. The radiation shield heating layer is a gold-plated copper screen with a thickness of 0.1 mm and a heating film with a resistance value of 100Ω printed on its surface.

6. The multi-mode calibration system for ultra-low temperature thermometers based on an LSTM model according to claim 1, characterized in that, The traceability sensor and the thermometer to be calibrated are inserted into the calibration chamber in parallel, with a sampling rate of 1Hz.

7. The multi-mode calibration system for ultra-low temperature thermometers based on an LSTM model according to claim 1, characterized in that, The pressure sensor is a fiber Bragg grating pressure sensor with a range of 0-10 MPa and a resolution of 0.1% FS.

8. The multi-mode calibration system for ultra-low temperature thermometers based on an LSTM model according to claim 1, characterized in that, The controller uses a quad-core Cortex-A73 processor with a main frequency of 2.0GHz and is connected to an external Xilinx Alveo U50 FPGA acceleration card.

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