A device and calibration method for long-term calibration of seawater salinity sensor

Abstract

The present invention belongs to the technical field of seawater salinity sensor calibration, and provides a device and calibration method for long-term calibration of seawater salinity sensors. The device includes a rotary valve, a pressure-bearing bladder, and a sensor placement chamber. The pressure-bearing bladder is provided with a sensor placement chamber, in which a test sensor and a reference sensor are installed. A corresponding watertight joint is provided above the sensor placement chamber, which is fixed to the top of the pressure-bearing bladder. The test sensor and the reference sensor are both connected to a power supply device and a computer via the watertight joint. The top of the pressure-bearing bladder is also provided with a rotary valve, the top of which is connected to a liquid injection / exhaust port. The outer surface of the pressure-bearing bladder is provided with a plurality of heat-conducting windows and an observation window. The outer wall of the pressure-bearing bladder on the side close to the sensor placement chamber is provided with an installation port, which is connected to a sealing device. The present invention can solve the problems of high measurement cost and volatile seawater in calibrating sensors using large water tanks.

Description

Technical Field

[0001] The present invention belongs to the technical field of seawater salinity sensor calibration, and in particular relates to a device and a calibration method for long-term calibration of a seawater salinity sensor. Background Art

[0002] Currently, there are multiple methods for measuring seawater salinity. Remote sensing satellite measurements can estimate salinity over large areas, but errors are significant. Fiber optic measurements infer salinity by analyzing changes in the properties of light in media such as seawater. However, in real-world marine environments, these measurements are affected by aquatic organisms, waves, bubbles, and droplets, limiting accuracy. Density methods are primarily laboratory-based and difficult to perform continuously at sea. Traditional chemical methods are cumbersome and, with the growing demand for in-situ testing, are becoming increasingly difficult to meet. Simple-to-use, fast-acting, and portable salinity measurement instruments are increasingly being used in marine environmental monitoring. However, salinity sensors can experience data drift during long-term operation, necessitating regular calibration. Sensor calibration typically involves filling a large tank with seawater, maintaining a uniform temperature, and stirring the tank to achieve a uniform temperature and salinity. The sensor is then compared with a solution of known conductivity or seawater to determine the accuracy of the measured value. While conventional calibration procedures can ensure the accuracy of sensor measurements in a laboratory environment to a certain extent, they fail to account for the impact of pressure changes caused by water depth on salinity measurements. Furthermore, the composition and concentration of seawater within the tank constantly change during long-term operation, which can easily lead to additional errors in the calibration process. Furthermore, while standard seawater solutions offer advantages such as fixed salinity, high accuracy, and reduced time required for seawater preparation, they can volatilize, leading to salinity fluctuations and reduced accuracy. This makes frequent use prohibitively expensive for sensors that require frequent calibration. Summary of the Invention

[0003] To address the deficiencies in the prior art, the present invention provides a device for long-term calibration of a seawater salinity sensor, which has good sealing properties and can prevent seawater volatilization and changes in composition and concentration. Furthermore, the device is relatively small and can be used in small test environments, thereby improving the device's applicability. The present invention also provides a method for long-term calibration of a seawater salinity sensor, which can calibrate the temperature, conductivity, and pressure of the salinity sensor, thereby improving the sensor's calibration accuracy.

[0004] The present invention adopts the following technical solutions.

[0005] On the one hand, the present invention provides a device for long-term calibration of a seawater salinity sensor, comprising a rotary valve, a pressure-bearing bladder and a sensor placement cabin, wherein the pressure-bearing bladder is provided with a sensor placement cabin, wherein a test sensor and a reference sensor are installed in the sensor placement cabin, and a watertight joint is correspondingly provided above the sensor placement cabin, which is fixed to the top of the pressure-bearing bladder, and the test sensor and the reference sensor are both connected to a power supply device and a computer through the watertight joint; a rotary valve is also provided on the top of the pressure-bearing bladder, and the top of the rotary valve is connected to an injection / exhaust port; a plurality of heat-conducting windows and observation windows are provided on the outer surface of the pressure-bearing bladder, and an installation port is provided on the outer wall of the pressure-bearing bladder close to the sensor placement cabin, which is connected to a sealing device, and the sealing device can be opened and closed, and the test sensor and the reference sensor are placed in the sensor placement cabin through the installation port and the sealing device thereon.

[0006] Furthermore, the top of the rotary valve is connected to the liquid injection / exhaust port via a flange. The rotary valve adopts a rotary ball valve, the through hole diameter of which is 2-6 cm and can withstand unidirectional pressure.

[0007] Furthermore, the sealing device includes a sealing cover and a fixing ring, the fixing ring is fixedly connected to the pressure-bearing bag, and the diameter of the central through hole of the fixing ring is adapted to the diameter of the mounting port; the sealing device also includes a snap-fit ​​structure, the snap-fit ​​structure includes a male buckle and a female buckle, one end of the sealing cover is hinged to one end of the fixing ring, the other end of the sealing cover is provided with a male buckle, and the other end of the fixing ring is provided with a female buckle, when the sealing cover is closed, the male buckle and the female buckle are snapped together, thereby locking the sealing cover and the fixing ring.

[0008] Furthermore, a groove is provided on the fixing ring, and a sealing protrusion is provided on the sealing cover. The height of the sealing protrusion is not less than the depth of the groove. When the sealing cover is closed, the sealing protrusion engages with the groove to improve the sealing performance of the pressure-bearing sac.

[0009] Furthermore, the pressure-bearing bladder is made of one or more layered structures of polyurethane material, nitrile rubber, and fluorosilicone rubber, extruded composite, with a thickness of 0-5.0 mm and a pressure resistance range of 0-60 MPa; the thermal conductive window is made of corrosion-resistant thermal conductive titanium alloy, the number is 1-10, the thickness is 0.2-1.5 cm, and the thermal conductive window and the pressure-bearing bladder are connected by a cold vulcanization process.

[0010] In another aspect, the present invention provides a long-term calibration method for a seawater salinity sensor, which is implemented based on the apparatus for long-term calibration of a seawater salinity sensor and includes the following steps:

[0011] S1: Place the test sensor and the reference sensor in the sensor placement chamber through the installation port and connect them to the watertight joints respectively. Close the sealing device and inject degassed and sterilized seawater of known salinity into the device for long-term calibration of seawater salinity sensors until the liquid level rises above the rotary valve. After removing the residual gas inside the device, close the rotary valve to fill the device with seawater.

[0012] S2: Immerse the device for long-term calibration of seawater salinity sensor in the liquid inside the thermostatic bath, control the temperature value of the thermostatic bath to decrease step by step within the calibration temperature range, keep the thermostatic bath warm at each set temperature point, and wait for the temperature fluctuation of the reference sensor to If the temperature fluctuation value is less than the set temperature fluctuation value, the temperature and conductivity measurement values ​​of the test sensor and the reference sensor corresponding to the set temperature point are recorded, and then the thermostat insulation and sensor data recording operations of the next set temperature point are entered until the recording of the entire calibration temperature range is completed. The temperature and conductivity measurement values ​​of the test sensor are calibrated by regressing the temperature and conductivity measurement values ​​of the test sensor and the reference sensor corresponding to each set temperature point in the calibration temperature range;

[0013] S3: Place the device for long-term calibration of seawater salinity sensor in a pressure tank, control the pressure inside the pressure tank to decrease step by step in the calibration pressure range, and control the pressure inside the pressure tank to be constant at each set pressure point. The pressure fluctuation ΔP of the reference sensor is If the pressure fluctuation value is less than the set pressure fluctuation value, the pressure measurement values ​​of the test sensor and the reference sensor corresponding to the set pressure point are recorded, and then the constant pressure and sensor data recording operation of the next set pressure point is entered until the recording of the entire calibration pressure range is completed. The pressure measurement value of the test sensor is calibrated by regressing the pressure measurement values ​​of the test sensor and the reference sensor corresponding to each set pressure point in the calibration pressure range;

[0014] S4: placing the calibrated test sensor and reference sensor into the device for long-term calibration of seawater salinity sensors at fixed intervals, filling the device with seawater of known salinity, keeping the device airtight, and immersing the device in the liquid inside a constant temperature bath, controlling the temperature value of the constant temperature bath to decrease step by step within a calibration temperature range, determining the difference in temperature and conductivity values ​​between the test sensor and the reference sensor at different temperatures, and thereby determining the data drift of the temperature indication and conductivity indication of the test sensor over time; placing the calibrated test sensor and reference sensor into the device for long-term calibration of seawater salinity sensors at fixed intervals, filling the device with seawater of known salinity, keeping the device airtight, and placing the device into a pressure tank, controlling the pressure of the pressure tank to decrease step by step within the calibration pressure range, and determining the difference in pressure indication of the test sensor and the reference sensor, and thereby determining the data drift of the pressure value of the test sensor over time; if the data drift range of the test sensor exceeds the set range, repeating S1-S3 to recalibrate the test sensor.

[0015] The beneficial effects of the present invention are as follows:

[0016] 1. The method for long-term calibration of a seawater salinity sensor provided by the present invention can calibrate the temperature, conductivity, and pressure of the sensor, thereby improving the accuracy and stability of the salinity sensor calibration and reducing errors caused by water depth changes and seawater volatilization.

[0017] 2. The device for long-term calibration of seawater salinity sensors provided by the present invention has good sealing performance, can effectively maintain the composition and concentration of seawater, and extend the service life of the calibration solution;

[0018] 3. The size design of the device for long-term calibration of seawater salinity sensors provided by the present invention is suitable for small test environments, making the calibration process more flexible and convenient, reducing calibration costs, and improving the economic benefits of the laboratory. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a front view of a device for long-term calibration of a seawater salinity sensor provided by the present invention.

[0020] Figure 2 The diagram is a top view of a device for long-term calibration of a seawater salinity sensor provided by the present invention.

[0021] Figure 3 It is a structural schematic diagram of the sealing device provided by the present invention.

[0022] In the figure: 1- liquid filling / exhaust port; 2- rotary valve; 3- watertight joint; 4- observation window; 5- pressure bladder; 6- sensor placement cabin; 7- thermal window; 8- installation port; 9- sealing cover; 10- fixing ring; 11- sealing protrusion; 12- groove; 13- male buckle; 14- female buckle. DETAILED DESCRIPTION

[0023] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. The embodiments described in this application are only part of the embodiments of the present invention, not all of them. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] like Figure 1-3 As shown, the present invention provides a device for long-term calibration of a seawater salinity sensor, comprising a rotary valve 2, a pressure-bearing bladder 5, and a sensor placement cabin 6. The pressure-bearing bladder 5 is provided with a sensor placement cabin 6, in which a test sensor and a reference sensor are installed. A watertight joint 3 is correspondingly provided above the sensor placement cabin 6 and fixed to the top of the pressure-bearing bladder 5. The test sensor and the reference sensor are both connected to a power supply device and a computer via the watertight joint 3.

[0025] A rotary valve 2 is also provided on the top of the pressure-bearing sac 5. The top of the rotary valve 2 is connected to the injection / exhaust port 1 through a flange. The rotary valve 2 adopts a rotary ball valve with a through hole diameter of 2-6 cm, which can withstand unidirectional pressure.

[0026] The outer surface of the pressure-bearing sac 5 is provided with a plurality of heat-conducting windows 7 and an observation window 4. The outer wall of the pressure-bearing sac 5 close to the sensor placement cabin 6 is provided with a mounting port 8. The mounting port 8 is fixedly connected to the sealing device, and the sealing device can be opened and closed. The test sensor and the reference sensor are placed in the sensor placement cabin 6 through the mounting port 8 and the sealing device thereon.

[0027] The sealing device includes a sealing cover 9 and a fixing ring 10. The fixing ring 10 is welded to the pressure-bearing sac 5. The diameter of the central through hole of the fixing ring 10 is adapted to the diameter of the mounting port 8. Sealant can also be applied to the connection between the fixing ring 10 and the mounting port 8 to further enhance the sealing performance.

[0028] The sealing device also includes a snap-fit ​​structure, which includes a male buckle 13 and a female buckle 14. One end of the sealing cover 9 is hinged to one end of the fixing ring 10, and the other end of the sealing cover 9 is provided with a male buckle 13, and the other end of the fixing ring 10 is provided with a female buckle 14. When the sealing cover 9 is closed, the male buckle 13 and the female buckle 14 are snapped together, thereby locking the sealing cover 9 and the fixing ring 10.

[0029] A groove 12 is provided on the fixing ring 10, and a sealing protrusion 11 is provided on the sealing cover 9. The height of the sealing protrusion 11 is not less than the depth of the groove 12. When the sealing cover 9 is closed, the sealing protrusion 11 engages with the groove 12 to improve the sealing performance of the pressure-bearing bladder 5.

[0030] The pressure-bearing bladder 5 is made of one or more layered structures of polyurethane material, nitrile rubber, and fluorosilicone rubber through extrusion and compounding, with a thickness of 0-5.0 mm and a pressure resistance range of 0-60 MPa.

[0031] The thermal conductive window 7 is made of corrosion-resistant thermal conductive titanium alloy, the number of which is 1-10 and the thickness is 0.2-1.5 cm. The thermal conductive window 7 is connected to the pressure bladder 5 using a cold vulcanization process to improve the heat exchange speed between the liquid inside the pressure bladder 5, the sensor and the external constant temperature water tank.

[0032] The observation window 4 is made of high-strength and high-transparency borosilicate glass, which can easily check the installation position and probe status of the sensor inside the pressure bag 5.

[0033] The present invention also provides a method for long-term calibration of a seawater salinity sensor, comprising the following steps.

[0034] S1: Place the test sensor and reference sensor in the sensor placement chamber 6 through the installation port 8 and connect them to the watertight joint 3 respectively. Close the sealing device and inject degassed and sterilized seawater of known salinity into the device for seawater salinity sensor calibration until the liquid level rises above the rotary valve 2. After removing the residual gas inside the device, close the rotary valve 2 to fill the device with seawater.

[0035] S2: Immerse the device for calibrating the seawater salinity sensor in the liquid inside the temperature-controlled thermostatic bath, control the temperature value of the thermostatic bath to gradually decrease from 40°C to 5°C, and set a set temperature point every 5°C. Keep the thermostatic bath warm for 30 minutes at each set temperature point, and wait for the temperature fluctuation of the reference sensor to After the temperature is less than ±0.005℃ / 15min, record the temperature and conductivity measurement values ​​of 5 groups of test sensors and reference sensors, and take the average value of the 5 groups of temperature and conductivity measurement values ​​as the temperature and conductivity measurement value corresponding to the test sensor and reference sensor at the set temperature point. Then enter the constant temperature bath insulation and sensor data recording operation at the next set temperature point until the recording of the entire calibration temperature range is completed. By regressing the temperature and conductivity measurement values ​​corresponding to each set temperature point in the calibration temperature range, the temperature and conductivity measurement values ​​of the test sensor are calibrated.

[0036] Temperature fluctuation at each set temperature point use Calculate, where Indicates the temperature fluctuation, Indicates the highest temperature value of the reference sensor during the insulation time. Indicates the lowest temperature value of the reference sensor during the holding time.

[0037] S3: Place the device for long-term calibration of seawater salinity sensor in a pressure tank, control the pressure inside the pressure tank to decrease step by step in the calibration pressure range, and set a pressure point every 5 MPa. At each set pressure point, control the pressure inside the pressure tank to be constant. The pressure fluctuation of the reference sensor is After the temperature is less than ±0.005℃ / 15min, record 5 groups of pressure measurement values ​​of the test sensor and the reference sensor, and take the average value of the 5 groups of pressure measurement values ​​as the pressure measurement value corresponding to the test sensor and the reference sensor at the set pressure point. Then enter the constant pressure and sensor data recording operation of the next set pressure point until the recording of the entire calibration pressure range is completed. By regressing the pressure measurement value corresponding to each set pressure point in the calibration pressure range, the pressure measurement value of the test sensor is calibrated.

[0038] Pressure fluctuation at each set pressure point use Calculate, where Indicates the pressure fluctuation, Indicates the maximum pressure value output by the reference sensor during the constant pressure period. Indicates the minimum pressure value output by the reference sensor during the constant pressure period.

[0039] S4: Check the temperature, conductivity, and pressure drift values ​​of the calibrated test sensor at fixed intervals. If the temperature drift of the test sensor exceeds 0.0002 degrees Celsius per year, or the conductivity drift of the test sensor exceeds 0.0003mS / cm per month, or the pressure drift of the test sensor exceeds 0.01%FS per year, repeat S1-S3 and recalibrate the test sensor to complete the long-term calibration of the test sensor.

[0040] The inspection of the temperature and conductivity drift values ​​of the test sensor includes: placing the calibrated test sensor and reference sensor into the device for long-term calibration of seawater salinity sensors at fixed intervals, filling the device with seawater of known salinity, keeping the device sealed, and immersing the device in the liquid inside a constant temperature bath, controlling the temperature value of the constant temperature bath to decrease step by step within the calibration temperature range, measuring the temperature and conductivity values ​​of the test sensor and reference sensor at different temperatures at fixed intervals, determining the difference in temperature and conductivity values ​​between the test sensor and the reference sensor, and thus determining the data drift of the temperature indication and conductivity indication of the test sensor over time.

[0041] The inspection of the pressure drift value of the test sensor includes: placing the calibrated test sensor and the reference sensor into the device for long-term calibration of the seawater salinity sensor at fixed intervals, filling the device with seawater of known salinity, keeping the device airtight, and placing the device in a pressure tank, controlling the pressure of the pressure tank to decrease step by step within the calibration pressure range, measuring the pressure values ​​of the test sensor and the reference sensor under different pressures at fixed intervals, determining the difference between the pressure indication of the test sensor and the pressure indication of the reference sensor, and thus determining the data drift of the pressure value of the test sensor over time.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A device for long-term calibration of a seawater salinity sensor, comprising a rotary valve (2), a pressure-bearing bladder (5), and a sensor placement cabin (6), characterized in that: A sensor placement cabin (6) is provided in the pressure-bearing sac (5), a test sensor and a reference sensor are installed in the sensor placement cabin (6), a watertight joint (3) is provided above the sensor placement cabin (6), the watertight joint (3) is fixed to the top of the pressure-bearing sac (5), and the test sensor and the reference sensor are connected to the power supply device and the computer through the watertight joint (3); The top of the pressure-bearing sac (5) is also provided with a rotary valve (2), and the top end of the rotary valve (2) is connected to the injection / exhaust port (1); the pressure-bearing sac (5) is made of one or more layered structures of polyurethane material, nitrile rubber, and fluorosilicone rubber by extrusion and compounding; The outer surface of the pressure-bearing sac (5) is provided with a plurality of heat-conducting windows (7) and an observation window (4); the outer wall of the pressure-bearing sac (5) on the side close to the sensor placement cabin (6) is provided with an installation opening (8); the installation opening (8) is connected to a sealing device, and the sealing device can be opened and closed; the test sensor and the reference sensor are placed in the sensor placement cabin (6) through the installation opening (8) and the sealing device thereon.

2. The device for long-term calibration of a seawater salinity sensor according to claim 1, characterized in that: The top end of the rotary valve (2) is connected to the liquid injection / exhaust port (1) via a flange. The rotary valve (2) is a rotary ball valve with a through hole diameter of 2-6 cm, which can withstand unidirectional pressure.

3. The device for long-term calibration of a seawater salinity sensor according to claim 1, characterized in that: The sealing device comprises a sealing cover (9) and a fixing ring (10), wherein the fixing ring (10) is fixedly connected to the pressure-bearing sac (5), and the diameter of the central through hole of the fixing ring (10) is adapted to the diameter of the mounting opening (8); The sealing device further comprises a snap-fit ​​structure, which comprises a male buckle (13) and a female buckle (14). One end of the sealing cover (9) is hinged to one end of the fixing ring (10). The other end of the sealing cover (9) is provided with a male buckle (13), and the other end of the fixing ring (10) is provided with a female buckle (14). When the sealing cover (9) is closed, the male buckle (13) and the female buckle (14) are snap-fitted, thereby locking the sealing cover (9) and the fixing ring (10).

4. The device for long-term calibration of a seawater salinity sensor according to claim 3, characterized in that: The fixing ring (10) is provided with a groove (12), and the sealing cover (9) is provided with a sealing protrusion (11). The height of the sealing protrusion (11) is not less than the depth of the groove (12). When the sealing cover (9) is closed, the sealing protrusion (11) is engaged with the groove (12), thereby improving the sealing performance of the pressure-bearing sac (5).

5. The device for long-term calibration of a seawater salinity sensor according to claim 1, characterized in that: The pressure-bearing bladder (5) has a thickness of 0-5.0 mm and a pressure resistance range of 0-60 MPa; The heat-conducting windows (7) are made of corrosion-resistant heat-conducting titanium alloy, the number of which is 1-10, and the thickness is 0.2-1.5 cm. The heat-conducting windows (7) are connected to the pressure-bearing bladder (5) using a cold vulcanization process.

6. A long-term calibration method for a seawater salinity sensor, implemented based on the device for long-term calibration of a seawater salinity sensor according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1: Place the test sensor and the reference sensor in the sensor placement chamber (6) through the installation port (8), and connect them to the watertight joint (3) respectively. Close the sealing device, inject the degassed and sterilized seawater of known salinity into the device for long-term calibration of the seawater salinity sensor, so that the liquid level rises to above the rotary valve (2). After removing the residual gas in the device, close the rotary valve (2) to make the device filled with seawater. S2: Immerse the device for long-term calibration of the seawater salinity sensor in the liquid inside the thermostatic bath, control the temperature value of the thermostatic bath to decrease step by step within the calibration temperature range, and keep the thermostatic bath warm at each set temperature point. When the temperature fluctuation ΔTf of the reference sensor is less than the set temperature fluctuation value, record the temperature and conductivity measurement values ​​of the test sensor and the reference sensor corresponding to the set temperature point, and then enter the thermostatic bath insulation and sensor data recording operation at the next set temperature point until the recording of the entire calibration temperature range is completed. By regressing the temperature and conductivity measurement values ​​of the test sensor and the reference sensor corresponding to each set temperature point within the calibration temperature range, the temperature and conductivity measurement values ​​of the test sensor are calibrated. S3: placing the device for long-term calibration of the seawater salinity sensor in a pressure tank, controlling the internal pressure of the pressure tank to decrease step by step in the calibration pressure range, controlling the pressure in the pressure tank to be constant at each set pressure point, and waiting for the pressure fluctuation ΔPf of the reference sensor to be less than the set pressure fluctuation value, recording the pressure measurement values ​​of the test sensor and the reference sensor corresponding to the set pressure point, and then entering the constant pressure and sensor data recording operation of the next set pressure point until the recording of the entire calibration pressure range is completed, and realizing the calibration of the pressure measurement value of the test sensor by regressing the pressure measurement values ​​of the test sensor and the reference sensor corresponding to each set pressure point in the calibration pressure range; S4: placing the calibrated test sensor and reference sensor into the device for long-term calibration of seawater salinity sensors at fixed intervals, filling the device with seawater of known salinity, keeping the device airtight, and immersing the device in the liquid inside a constant temperature bath, controlling the temperature value of the constant temperature bath to decrease step by step within a calibration temperature range, determining the difference in temperature and conductivity values ​​between the test sensor and the reference sensor at different temperatures, and thereby determining the data drift of the temperature indication and conductivity indication of the test sensor over time; placing the calibrated test sensor and reference sensor into the device for long-term calibration of seawater salinity sensors at fixed intervals, filling the device with seawater of known salinity, keeping the device airtight, and placing the device into a pressure tank, controlling the pressure of the pressure tank to decrease step by step within the calibration pressure range, and determining the difference in pressure indication of the test sensor and the reference sensor, and thereby determining the data drift of the pressure value of the test sensor over time; if the data drift range of the test sensor exceeds the set range, repeating S1-S3 to recalibrate the test sensor.

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