Fixed online refractometer calibration device

Abstract

The invention discloses a fixed online refractometer calibration device which comprises a liquid medium circulation structure and a refractometer calibration structure. The liquid medium circulating structure is used for realizing dynamic circulation of a liquid medium at a specified temperature and comprises a plurality of liquid storage bottles, a constant-temperature liquid storage tank and a circulating pipeline; the liquid storage bottles are used for containing different liquid media, the constant-temperature liquid storage tank is connected with the liquid storage bottles, and the two ends of the circulating pipeline are communicated with the constant-temperature liquid storage tank. The refractometer calibration structure is arranged on the circulating pipeline and comprises a reference refractometer, a calibrated refractometer and a temperature sensor. According to the fixed online refractometer calibration device, dynamic calibration can be implemented under the conditions of specific refractive index or concentration and specified temperature, and data deviation caused by factors such as temperature and flow of a liquid medium in offline static calibration is avoided; the device is suitable for detachable online refractometers or online refractometers which have high requirements on measurement accuracy and can be used as reference instruments, and is reasonable in design and high in operability.

Description

Technical Field

[0001] The invention relates to the field of metrological calibration and instrument process verification, and in particular to a fixed online refractometer calibration device. Background Art

[0002] Refractive index (also known as refractive index or refractive index) is a specific intrinsic property of a substance and changes according to temperature and wavelength. For pure substances, the physical property of refractive index can be used to identify and distinguish samples; for binary mixtures (such as solutes dissolved in solvents), the refractive index can be used to measure concentration (common ones are Brix, which characterizes the concentration of sucrose aqueous solution, and salinity, which characterizes the concentration of sodium chloride aqueous solution); for binary or multicomponent mixtures with known composition ratios, quality control can also be performed by monitoring the refractive index. Online refractive index technology is a type of process analysis technology. Its basic application is to use the data stream provided by the online refractometer to realize process relative trend judgment and real-time monitoring. On this basis, combined with other data streams such as reference data from process variables and analytical laboratories for comprehensive data analysis, it can realize real-time monitoring of key quality attributes of products and associate them with key process parameters, and finally realize real-time release of product indicators. This helps to improve product quality, reduce production costs, improve production efficiency, reduce laboratory testing needs, and determine the timing of process improvement. The ultimate result is to reduce the risk and cost of product production. The online refractometer is the core of implementing online refractometer technology. The quality of its performance and the accuracy of its measurement value are related to the effectiveness of subsequent data flow, which ultimately affects product production.

[0003] Unlike laboratory refractometers, online refractometers are installed "in-line", "on-line" or "near-line", and sample collection and analysis are completed "in situ" or "near in situ". The actual measurement results are often far from the measurement results of laboratory refractometers under reference conditions, resulting in the "reference data" measured by laboratory refractometers being of no reference value for samples under working conditions, thus affecting the actual effect of online refractometer technology.

[0004] Therefore, a fixed online refractometer calibration device is needed to solve the above problems. Summary of the invention

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A fixed online refractometer calibration device comprises a liquid medium circulation structure and a refractometer calibration structure; the liquid medium circulation structure is used to realize the dynamic circulation of the liquid medium at a specified temperature, and the liquid medium flows through the refractometer calibration structure; the liquid medium circulation structure comprises a plurality of liquid storage bottles, a constant temperature liquid storage tank and a circulation pipeline; the plurality of liquid storage bottles are used to place different liquid media; the constant temperature liquid storage tank is respectively connected to the plurality of liquid storage bottles; both ends of the circulation pipeline are respectively connected to the constant temperature liquid storage tank; the refractometer calibration structure is arranged on the circulation pipeline, and comprises a refractometer to be calibrated.

[0007] Preferably, the refractometer calibration structure also includes a first reference refractometer, a second reference refractometer and two first temperature sensors. The first reference refractometer and the second reference refractometer are respectively arranged on both sides of the calibrated refractometer and connected to the calibrated refractometer. The two first temperature sensors are respectively arranged at the inlet end of the first reference refractometer and the outlet end of the second reference refractometer.

[0008] Preferably, the liquid medium circulation structure also includes a vacuum degassing tank, which is arranged between the constant temperature liquid storage tank and the second reference refractometer, the vacuum degassing tank is connected to the constant temperature liquid storage tank, the second reference refractometer is connected to the vacuum degassing tank, and the first reference refractometer is connected to the constant temperature liquid storage tank.

[0009] Preferably, each liquid storage bottle also includes a peristaltic pump, the input end of the peristaltic pump is connected to the interior of the corresponding liquid storage bottle through a pipeline, the output end of the peristaltic pump is connected to the input end of the switching valve through a pipeline, and the output end of the switching valve is connected to the constant temperature liquid storage tank; the liquid storage bottle is placed with a corresponding liquid medium, and the required liquid medium is transferred to the constant temperature liquid storage tank through the peristaltic pump and the switching valve.

[0010] Preferably, the switching valve is a multi-channel switching valve.

[0011] Preferably, a pressure sensor and a degassing pump are installed on the vacuum degassing tank, and both the pressure sensor and the degassing pump are connected to the vacuum degassing tank; the degassing pump is used to remove dissolved gas in the liquid in the vacuum degassing tank, and the pressure sensor is used to monitor the pressure in the vacuum degassing tank.

[0012] Preferably, the circulation pipeline is also provided with a first electric valve, a filter, a gear pump and a gear flowmeter. The first electric valve is respectively connected to the constant temperature liquid storage tank and the filter, the gear pump is respectively connected to the filter and the gear flowmeter, and the gear flowmeter is connected to the first reference refractometer.

[0013] Preferably, the fixed online refractometer calibration device also includes a second pipeline, which is connected to the circulation pipeline, and the connection is located between the first electric valve and the constant temperature liquid storage tank; the second pipeline contains two recovery pipelines, which are respectively connected to the inorganic waste liquid tank and the organic waste liquid tank, and a second electric valve is provided on the recovery pipeline; a sampling port is provided at the end of the second pipeline.

[0014] Preferably, a second pressure sensor and a second temperature sensor are provided on the constant temperature liquid storage tank, the second pressure sensor is used to detect the pressure in the constant temperature liquid storage tank, and the second temperature sensor is used to detect the temperature of the liquid medium in the constant temperature liquid storage tank; a semiconductor temperature controller and a third temperature sensor are provided outside the constant temperature liquid storage tank, the semiconductor temperature controller is used to control the temperature of the liquid in the constant temperature liquid storage tank, and the third temperature sensor is used to detect the temperature of the semiconductor temperature controller.

[0015] Preferably, the circulation pipeline is also provided with an insulation sleeve, which is arranged outside the circulation pipeline, and the interior of the sleeve is circulated and connected with a constant temperature water bath. The temperature of the liquid medium flowing through the circulation pipeline is maintained by adjusting the temperature of the external circulation water bath of the constant temperature water bath.

[0016] Preferably, the method for using the fixed online refractometer calibration device comprises the following steps:

[0017] (1) Select the appropriate calibration method according to the situation of the refractometer to be calibrated and the needs of the user. For the refractometer to be calibrated with high measurement accuracy requirements and used as a reference instrument, its value is traced back to a stable homogeneous liquid with a known specific refractive index or concentration through a calibration device, and the calibration device is not installed with a reference refractometer; for the refractometer to be calibrated with low measurement accuracy requirements and not used as a reference instrument, its value is traced back to the reference refractometer of the calibration device; the calibration items include temperature indication error, refractive index or concentration indication error, refractive index or concentration repeatability, and refractive index or concentration stability;

[0018] (2) At a specified temperature, the average temperature at both ends of the refractometer being calibrated is used as the standard value, and the temperature measurement value of the refractometer being calibrated is read and compared with it. The difference between the two is the temperature indication error of the refractometer being calibrated at the specified temperature;

[0019] (3) At a specified temperature, the refractive index or concentration value of a liquid with a known specific refractive index or concentration is used as the standard value, or the refractive index or concentration measured value of a reference refractometer is used as the standard value, and the refractive index or concentration measured value of the refractometer to be calibrated is read and compared with the standard value. The difference between the two is the refractive index or concentration indication error of the refractometer to be calibrated at the specified temperature;

[0020] (4) Continuously obtain a set of not less than 6 refractive index or concentration measurement data of the refractometer to be calibrated, and use the Bessel formula to calculate the standard deviation of the set of measurement data as the refractive index or concentration repeatability calibration result of the refractometer to be calibrated;

[0021] (5) Obtain the refractive index or concentration measurement data of the refractometer to be calibrated once every 15 minutes for 1 hour. The ratio of the difference between the maximum and minimum values ​​of the refractive index or concentration measurement data obtained and the initial measurement value is used as the refractive index or concentration stability calibration result of the refractometer to be calibrated;

[0022] (6) Calibrate the refractometer to be calibrated based on the calibration results of the temperature indication error, refractive index or concentration indication error, or perform data correction on the temperature measurement value, refractive index or concentration measurement value of the refractometer to be calibrated.

[0023] Due to the adoption of the above technical solution, the present invention has the following technical advances compared with the prior art:

[0024] 1. By adjusting the peristaltic pump, the switching valve, the first electric valve and the second electric valve, different liquid media can be selected to calibrate the refractometer to be calibrated, or different cleaning media can be selected to clean the pipeline, and finally the liquid medium in the pipeline is transferred to the inorganic waste liquid tank or the organic waste liquid tank according to its properties. The device is reasonably designed and highly operable.

[0025] 2. The fixed online refractometer calibration device is designed with a temperature control function. By allowing the liquid medium at a specific temperature to circulate in the pipeline, it can implement dynamic calibration of the refractometer under specific refractive index or concentration and specified temperature conditions, avoiding data deviation caused by factors such as the temperature and flow of the liquid medium in the offline static calibration.

[0026] 3. According to the situation of the refractometer to be calibrated, the fixed online refractometer calibration device can be divided into two different calibration methods. Calibration method 1: The calibration device is not equipped with a reference refractometer. The refractive index or concentration value of a stable homogeneous liquid with a known specific refractive index or concentration is used as a standard value to calibrate the refractive index or concentration indication error of the instrument. This method is suitable for detachable online refractometers that have high requirements for measurement accuracy and can be used as reference instruments. Calibration method 2: The calibration device is equipped with a reference refractometer. The refractive index or concentration measurement value of the reference refractometer is used as a standard value to calibrate the refractive index or concentration indication error of the instrument. This method is suitable for detachable online refractometers that have low requirements for measurement accuracy and are not used as reference instruments.

[0027] 4. After calibrating the instrument using a fixed online refractometer calibration device, the instrument can be calibrated according to the calibration results, and the built-in measurement parameters of the instrument can be corrected to reduce the indication error of the instrument. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0029] Figure 1 It is a structural schematic diagram of calibration method 1 of the fixed online refractometer calibration device of the present invention;

[0030] Figure 2 It is a structural schematic diagram of calibration method 2 of the fixed online refractometer calibration device of the present invention.

[0031] Explanation of the main component symbols: 1. Liquid storage bottle; 2. Peristaltic pump; 3. Switching valve; 4. Constant temperature liquid storage tank; 8. Inorganic waste liquid tank; 9. Organic waste liquid tank; 10. Sampling port; 11. First electric valve; 12. Filter; 13. Gear pump; 14. Gear flowmeter; 15. First reference refractometer; 16. Calibrated refractometer; 17. Second reference refractometer; 18. First temperature sensor; 20. Vacuum degassing tank; 21. Pressure sensor; 22. Degassing pump; 23. Circulation pipeline; 24. Constant temperature water bath; 30. Second pipeline; 301. Recovery pipeline; 302. Second electric valve; 41. Second pressure sensor; 42. Second temperature sensor; 43. Semiconductor temperature controller; 44. Third temperature sensor; 230. Insulation sleeve. DETAILED DESCRIPTION

[0032] The following embodiments may help those skilled in the art to more fully understand the present invention, but shall not limit the present invention in any way.

[0033] See also Figure 1-Figure 2 A fixed online refractometer calibration device includes a liquid medium circulation structure and a refractometer calibration structure; the liquid medium circulation structure is used to realize dynamic circulation of the liquid medium at a specified temperature, and the liquid medium flows through the refractometer calibration structure; the liquid medium circulation structure includes a plurality of liquid storage bottles 1, a constant temperature liquid storage tank 4 and a circulation pipeline 23; the plurality of liquid storage bottles 1 are used to place different liquid media; the constant temperature liquid storage tank 4 is respectively connected to the plurality of liquid storage bottles 1; both ends of the circulation pipeline 23 are respectively connected to the constant temperature liquid storage tank 4; the refractometer calibration structure is arranged on the circulation pipeline 23, and includes a calibrated refractometer 16.

[0034] In one embodiment of the present invention, the refractometer calibration structure further includes a first reference refractometer 15, a second reference refractometer 17 and two first temperature sensors 18. The first reference refractometer 15 and the second reference refractometer 17 are respectively arranged on both sides of the calibrated refractometer 16 and connected to the calibrated refractometer 16. The two first temperature sensors 18 are respectively arranged at the inlet end of the first reference refractometer 15 and the outlet end of the second reference refractometer 17.

[0035] In one embodiment of the present invention, the liquid medium circulation structure also includes a vacuum degassing tank 20, which is arranged between the constant temperature liquid storage tank 4 and the second reference refractometer 17, the vacuum degassing tank 20 is connected to the constant temperature liquid storage tank 4, the second reference refractometer 17 is connected to the vacuum degassing tank 20, and the first reference refractometer 15 is connected to the constant temperature liquid storage tank 4.

[0036] In one embodiment of the present invention, each liquid storage bottle 1 also includes a peristaltic pump 2, the input end of the peristaltic pump 2 is connected to the interior of the corresponding liquid storage bottle 1 through a pipeline, the output end of the peristaltic pump 2 is connected to the input end of the switching valve 3 through a pipeline, and the output end of the switching valve 3 is connected to the constant temperature liquid storage tank 4; the liquid storage bottle 1 is placed with a corresponding liquid medium, and the required liquid medium is transferred to the constant temperature liquid storage tank 4 through the peristaltic pump 2 and the switching valve 3.

[0037] In one embodiment of the present invention, the switching valve 3 is a multi-channel switching valve.

[0038] In one embodiment of the present invention, a pressure sensor 21 and a degassing pump 22 are installed on the vacuum degassing tank 20, and both the pressure sensor 21 and the degassing pump 22 are connected to the vacuum degassing tank 20; the degassing pump is used to remove dissolved gas in the liquid in the vacuum degassing tank 20, and the pressure sensor 21 is used to monitor the pressure in the vacuum degassing tank 20.

[0039] In one embodiment of the present invention, a first electric valve 11, a filter 12, a gear pump 13, and a gear flowmeter 14 are also provided on the circulation pipeline 23. The first electric valve 11 is respectively connected to the constant temperature liquid storage tank 4 and the filter 12, the gear pump 13 is respectively connected to the filter 12 and the gear flowmeter 14, and the gear flowmeter 14 is connected to the first reference refractometer 15.

[0040] Furthermore, the fixed online refractometer calibration device also includes a second pipeline 30, which is connected to the circulation pipeline 23, and the connection is located between the first electric valve 11 and the constant temperature liquid storage tank 4; the second pipeline 30 contains two recovery pipelines 301, which are respectively connected to the inorganic waste liquid tank 8 and the organic waste liquid tank 9, and a second electric valve 302 is provided on the recovery pipeline 301; a sampling port 10 is provided at the end of the second pipeline.

[0041] In one embodiment of the present invention, the thermostatic liquid storage tank 4 is provided with a second pressure sensor 41 and a second temperature sensor 42, the second pressure sensor 41 is used to detect the pressure in the thermostatic liquid storage tank 4, and the second temperature sensor 42 is used to detect the temperature of the liquid medium in the thermostatic liquid storage tank 4; the thermostatic liquid storage tank 4 is provided with a semiconductor thermostat 43 and a third temperature sensor 44 outside the thermostatic liquid storage tank 4, the semiconductor thermostat 43 is used to control the temperature of the liquid in the thermostatic liquid storage tank 4, and the third temperature sensor 44 is used to detect the temperature of the semiconductor thermostat 43. The semiconductor thermostat 43 can adjust and maintain the temperature of the liquid medium in the thermostatic liquid storage tank 4.

[0042] In one embodiment of the present invention, a heat-insulating sleeve 230 is further provided on the circulation pipe 23. The heat-insulating sleeve 230 is arranged outside the circulation pipe 23, and the interior of the sleeve is circulated and connected with the constant temperature water bath 24. The temperature of the liquid medium flowing through the circulation pipe 23 is maintained by adjusting the temperature of the external circulation water bath of the constant temperature water bath 24.

[0043] In one embodiment of the present invention, a method for using a fixed online refractometer calibration device comprises the following steps:

[0044] (1) Select the appropriate calibration method according to the situation of the refractometer to be calibrated and the needs of the user. For the refractometer to be calibrated with high measurement accuracy requirements and used as a reference instrument, its value is traced back to a stable homogeneous liquid with a known specific refractive index or concentration through a calibration device, and the calibration device is not installed with a reference refractometer; for the refractometer to be calibrated with low measurement accuracy requirements and not used as a reference instrument, its value is traced back to the reference refractometer of the calibration device; the calibration items include temperature indication error, refractive index or concentration indication error, refractive index or concentration repeatability, and refractive index or concentration stability;

[0045] (2) At a specified temperature, the average temperature at both ends of the refractometer being calibrated is used as the standard value, and the temperature measurement value of the refractometer being calibrated is read and compared with it. The difference between the two is the temperature indication error of the refractometer being calibrated at the specified temperature;

[0046] (3) At a specified temperature, the refractive index or concentration value of a liquid with a known specific refractive index or concentration is used as the standard value, or the refractive index or concentration measured value of a reference refractometer is used as the standard value, and the refractive index or concentration measured value of the refractometer to be calibrated is read and compared with the standard value. The difference between the two is the refractive index or concentration indication error of the refractometer to be calibrated at the specified temperature;

[0047] (4) Continuously obtain a set of not less than 6 refractive index or concentration measurement data of the refractometer to be calibrated, and use the Bessel formula to calculate the standard deviation of the set of measurement data as the refractive index or concentration repeatability calibration result of the refractometer to be calibrated;

[0048] (5) Obtain the refractive index or concentration measurement data of the refractometer to be calibrated once every 15 minutes for 1 hour. The ratio of the difference between the maximum and minimum values ​​of the refractive index or concentration measurement data obtained and the initial measurement value is used as the refractive index or concentration stability calibration result of the refractometer to be calibrated;

[0049] (6) Calibrate the refractometer to be calibrated based on the calibration results of the temperature indication error, refractive index or concentration indication error, or perform data correction on the temperature measurement value, refractive index or concentration measurement value of the refractometer to be calibrated.

[0050] The use process of the present invention:

[0051] See also Figure 1 , calibration method 1 (the calibration device is not equipped with a reference refractometer): add a stable homogeneous liquid with a known specific refractive index or concentration to the liquid storage bottle 1, transfer the required liquid to the constant temperature liquid storage tank 4 through the peristaltic pump 2 and the switching valve 3, and after completion, switch the switching valve 3 to the stop position, start the semiconductor temperature controller 43 and the constant temperature water bath 24 in turn, set the required temperature, turn on the gear pump 13 and the degassing pump 22, let the liquid medium circulate in the circulation pipe 23, and wait until the temperature is constant to the required temperature, and the temperature indications of the two first temperature sensors 18 are equal to each other. After the difference meets the calibration requirements and the indication of the refractometer 16 to be calibrated tends to be stable, the refractive index or concentration indication and temperature indication of the refractometer 16 to be calibrated are read respectively, and the refractive index or concentration value of the liquid with a known specific refractive index or concentration is used as the refractive index or concentration standard value, the average temperature indication of the two first temperature sensors 18 is used as the temperature standard value, and the difference between the indication of the refractometer 16 and the standard value is used as the indication error of the refractometer 16 to obtain the refractive index or concentration indication error and temperature indication error of the refractometer 16. By adjusting the peristaltic pump 2, the switching valve 3, the first electric valve 11, and the second electric valve 302, different stable homogeneous liquids with known specific refractive index or concentration can be replaced to calibrate the refractometer 16, or different cleaning media can be selected to clean the pipeline, and finally the liquid medium in the pipeline is transferred to the inorganic waste liquid tank 8 or the organic waste liquid tank 9 according to its properties. Under this calibration mode, the main flow direction of the liquid is liquid storage bottle 1 → peristaltic pump 2 → switching valve 3 → constant temperature liquid storage tank 4 → first electric valve 11 → filter 12 → gear pump 13 → gear flowmeter 14 → calibrated refractometer 16 → vacuum degassing tank 20 → constant temperature liquid storage tank 4.

[0052] See also Figure 2, calibration method 2 (calibration device with reference refractometer installed): add a stable liquid with uniform refractive index or concentration to the liquid storage bottle 1, transfer the required liquid to the constant temperature liquid storage tank 4 through the peristaltic pump 2 and the switching valve 3, switch the switching valve 3 to the stop position after completion, start the semiconductor temperature controller 43 and the constant temperature water bath 24 in turn, set the required temperature, turn on the gear pump 13 and the degassing pump 22, let the liquid medium circulate in the circulation pipe 23, wait until the constant temperature reaches the required temperature, the difference between the temperature indications of the two first temperature sensors 18 meets the calibration requirements, and the first reference refractometer 15 and the second reference refractometer After the indications of the refractometer 17 and the calibrated refractometer 16 tend to be stable, the refractive index or concentration indication and temperature indication of the first reference refractometer 15, the second reference refractometer 17 and the calibrated refractometer 16 are recorded respectively, the average of the refractive index or concentration indication of the first reference refractometer 15 and the second reference refractometer 17 is taken as the refractive index standard value, the average of the temperature indications of the two first temperature sensors 18 is taken as the temperature standard value, and the difference between the indication of the calibrated refractometer 16 and the standard value is taken as the indication error of the calibrated refractometer 16, and the refractive index or concentration indication error and temperature indication error of the calibrated refractometer 16 are obtained respectively. By adjusting the peristaltic pump 2, the switching valve 3, the first electric valve 11, and the second electric valve 302, different refractive index or concentration uniform liquids are selected to calibrate the calibrated refractometer 16, or different cleaning media are selected to clean the pipeline, and finally the liquid medium in the pipeline is transferred to the inorganic waste liquid tank 8 or the organic waste liquid tank 9 according to its properties. Under this calibration mode, the main flow direction of the liquid is liquid storage bottle 1 → peristaltic pump 2 → switching valve 3 → constant temperature liquid storage tank 4 → first electric valve 11 → filter 12 → gear pump 13 → gear flowmeter 14 → first reference refractometer 15 → calibrated refractometer 16 → second reference refractometer 17 → vacuum degassing tank 20 → constant temperature liquid storage tank 4.

[0053] The above generally describes the present invention in detail, but it is obvious to a person skilled in the art that some modifications or improvements can be made to the present invention. Therefore, modifications or improvements that do not depart from the spirit of the present invention are within the scope of protection of the present invention.

Claims

1. A fixed online refractometer calibration device, characterized in that: The invention comprises a liquid medium circulation structure and a refractometer calibration structure; the liquid medium circulation structure is used to realize the dynamic circulation of the liquid medium at a specified temperature, and the liquid medium flows through the refractometer calibration structure; the liquid medium circulation structure comprises a plurality of liquid storage bottles (1), a constant temperature liquid storage tank (4) and a circulation pipeline (23); the plurality of liquid storage bottles (1) are used to store different liquid media; the constant temperature liquid storage tank (4) is respectively connected to the plurality of liquid storage bottles (1); the two ends of the circulation pipeline (23) are respectively connected to the constant temperature liquid storage tank (4); the refractometer calibration structure is arranged on the circulation pipeline (23) and comprises a refractometer (16) to be calibrated.

2. The fixed online refractometer calibration device according to claim 1, characterized in that: The refractometer calibration structure also includes a first reference refractometer (15), a second reference refractometer (17) and two first temperature sensors (18). The first reference refractometer (15) and the second reference refractometer (17) are respectively arranged on both sides of the calibrated refractometer (16) and connected to the calibrated refractometer (16). The two first temperature sensors (18) are respectively arranged at the inlet end of the first reference refractometer (15) and the outlet end of the second reference refractometer (17).

3. The fixed online refractometer calibration device according to claim 1, characterized in that: The liquid medium circulation structure also includes a vacuum degassing tank (20), which is arranged between the constant temperature liquid storage tank (4) and the second reference refractometer (17), the vacuum degassing tank (20) is connected to the constant temperature liquid storage tank (4), the second reference refractometer (17) is connected to the vacuum degassing tank (20), and the first reference refractometer (15) is connected to the constant temperature liquid storage tank (4).

4. The fixed online refractometer calibration device according to claim 1, characterized in that: Each liquid storage bottle (1) further comprises a peristaltic pump (2); the input end of the peristaltic pump (2) is connected to the interior of the corresponding liquid storage bottle (1) through a pipeline; the output end of the peristaltic pump (2) is connected to the input end of a switching valve (3) through a pipeline; the output end of the switching valve (3) is connected to a constant temperature liquid storage tank (4); the liquid storage bottle (1) contains a corresponding liquid medium, and the required liquid medium is transferred to the constant temperature liquid storage tank (4) through the peristaltic pump (2) and the switching valve (3).

5. The fixed online refractometer calibration device according to claim 3, characterized in that: A pressure sensor (21) and a degassing pump (22) are installed on the vacuum degassing tank (20), and both the pressure sensor (21) and the degassing pump (22) are connected to the vacuum degassing tank (20); the degassing pump (22) is used to remove dissolved gas in the liquid in the vacuum degassing tank (20), and the pressure sensor (21) is used to monitor the pressure in the vacuum degassing tank (20).

6. The fixed online refractometer calibration device according to claim 1, characterized in that: The circulation pipeline (23) is also provided with a first electric valve (11), a filter (12), a gear pump (13), and a gear flow meter (14); the first electric valve (11) is connected to the constant temperature liquid storage tank (4) and the filter (12) respectively; the gear pump (13) is connected to the filter (12) and the gear flow meter (14) respectively; and the gear flow meter (14) is connected to a first reference refractometer (15).

7. The fixed online refractometer calibration device according to claim 1, characterized in that: The fixed online refractometer calibration device also includes a second pipeline (30), the second pipeline (30) is connected to the circulation pipeline (23), and the connection point is located between the first electric valve (11) and the constant temperature liquid storage tank (4); the second pipeline (30) contains two recovery pipelines (301), which are respectively connected to the inorganic waste liquid tank (8) and the organic waste liquid tank (9), and each recovery pipeline (301) is provided with a second electric valve (302); and a sampling port (10) is provided at the end of the second pipeline (30).

8. The fixed online refractometer calibration device according to claim 1, characterized in that: The constant temperature liquid storage tank (4) is provided with a second pressure sensor (41) and a second temperature sensor (42), the second pressure sensor (41) is used to detect the pressure in the constant temperature liquid storage tank (4), and the second temperature sensor (42) is used to detect the temperature of the liquid medium in the constant temperature liquid storage tank (4); a semiconductor temperature controller (43) and a third temperature sensor (44) are provided outside the constant temperature liquid storage tank (4), the semiconductor temperature controller (43) is used to control the temperature of the liquid in the constant temperature liquid storage tank (4), and the third temperature sensor (44) is used to detect the temperature of the semiconductor temperature controller (43).

9. The fixed online refractometer calibration device according to claim 1, characterized in that: The circulation pipe (23) is also provided with a heat-insulating sleeve (230), which is arranged outside the circulation pipe (23) and whose interior is in circulation communication with the constant-temperature water bath (24). The temperature of the liquid medium flowing through the circulation pipe (23) is maintained by adjusting the temperature of the external circulating water bath of the constant-temperature water bath (24).

10. The fixed online refractometer calibration device according to any one of claims 1 to 9, characterized in that: The method for using the fixed online refractometer calibration device comprises the following steps: (1) Select the appropriate calibration method according to the situation of the refractometer to be calibrated and the needs of the user. For the refractometer to be calibrated with high measurement accuracy requirements and used as a reference instrument, its value is traced back to a stable homogeneous liquid with a known specific refractive index or concentration through a calibration device, and the calibration device is not equipped with a reference refractometer. For the refractometer to be calibrated with low measurement accuracy requirements and not used as a reference instrument, its value is traced back to the reference refractometer of the calibration device. The calibration items include temperature indication error, refractive index or concentration indication error, refractive index or concentration repeatability, and refractive index or concentration stability. (2) At a specified temperature, the average temperature at both ends of the refractometer being calibrated is used as the standard value, and the temperature measurement value of the refractometer being calibrated is read and compared with it. The difference between the two is the temperature indication error of the refractometer being calibrated at the specified temperature; (3) At a specified temperature, the refractive index or concentration value of a liquid with a known specific refractive index or concentration is used as the standard value, or the refractive index or concentration measured value of a reference refractometer is used as the standard value, and the refractive index or concentration measured value of the refractometer to be calibrated is read and compared with the standard value. The difference between the two is the refractive index or concentration indication error of the refractometer to be calibrated at the specified temperature; (4) Continuously obtain a set of not less than 6 refractive index or concentration measurement data of the refractometer to be calibrated, and use the Bessel formula to calculate the standard deviation of the set of measurement data as the refractive index or concentration repeatability calibration result of the refractometer to be calibrated; (5) Obtain the refractive index or concentration measurement data of the refractometer to be calibrated once every 15 minutes for 1 hour. The ratio of the difference between the maximum and minimum values ​​of the refractive index or concentration measurement data obtained and the initial measurement value is used as the refractive index or concentration stability calibration result of the refractometer to be calibrated; (6) Calibrate the refractometer to be calibrated based on the calibration results of the temperature indication error, refractive index or concentration indication error, or perform data correction on the temperature measurement value, refractive index or concentration measurement value of the refractometer to be calibrated.

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