Device for long-term calibration of seawater salinity sensor and calibration method

Abstract

The invention belongs to the technical field of seawater salinity sensor calibration, and provides a device for long-term calibration of a seawater salinity sensor and a calibration method.The device comprises a rotary valve, a pressure-bearing bag body and a sensor placement cabin, the sensor placement cabin is arranged in the pressure-bearing bag body, and a test sensor and a reference sensor are installed in the sensor placement cabin; a watertight joint is correspondingly arranged above the sensor placement cabin, the watertight joint is fixed at the top of the pressure-bearing bag body, and the test sensor and the reference sensor are connected with a power supply device and a computer through the watertight joint; a rotary valve is further arranged at the top of the pressure-bearing bag body, and the top end of the rotary valve is connected with the liquid injection / exhaust port; a plurality of heat conduction windows and observation windows are formed in the outer surface of the pressure-bearing bag body, a mounting opening is formed in the outer wall of the side, close to the sensor placement cabin, of the pressure-bearing bag body, and the mounting opening is connected with a sealing device. According to the invention, the problems of high measurement cost and easy volatilization of seawater when the sensor is calibrated through a large water tank can be solved.

Description

Technical Field

[0001] The 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] At present, there are many methods for measuring seawater salinity. Among them, remote sensing satellite measurement can estimate salinity by scanning a large area, but the error is large; fiber optic measurement infers salinity through the change of light properties in media such as seawater, but in the actual marine environment, it is affected by aquatic organisms, sea wave bubbles and foam, and the accuracy is limited; the density method is mostly operated in the laboratory and it is difficult to measure continuously in the sea; the traditional chemical method is cumbersome to operate, and with the growing demand for in-situ testing, it is difficult to meet the needs. Salinity measuring instruments that are simple to operate, fast to measure, and portable are becoming more and more widely used in marine environmental monitoring. However, salinity sensors will have problems such as data drift during long-term operation, so they need to be calibrated regularly. The routine operation of sensor calibration is to fill a large water tank with seawater, control the temperature of the water tank to be uniform and stir it to make its temperature and salinity uniform, and then compare the sensor with a solution or seawater of known conductivity to determine the accuracy of the measured value. Although the conventional calibration process can meet the accuracy of sensor measurement values ​​in laboratory environments to a certain extent, it is difficult to consider the impact of pressure changes caused by water depth on salinity measurement. In addition, the composition and concentration of seawater inside the tank are constantly changing during long-term operation, which can easily lead to additional errors in the calibration process. In addition, although the standard seawater solution has the advantages of fixed salinity, high accuracy, and can save time for complex seawater configuration, it has volatilization problems, which leads to changes in salinity and reduced accuracy. For sensors that need to be calibrated frequently, the cost of frequent use is too high. Summary of the invention

[0003] In order to solve the deficiencies in the prior art, the device for long-term calibration of a seawater salinity sensor provided by the present invention has good sealing performance, can prevent seawater from volatilizing and changes in composition and concentration, and the device is small in size and can be used in a small test environment, thereby improving the applicability of the device; 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 salinity sensor, thereby improving the calibration accuracy of the sensor.

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

[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, wherein a watertight joint is correspondingly provided above the sensor placement cabin, wherein the watertight joint is fixed to the top of the pressure-bearing bladder, wherein the test sensor and the reference sensor are connected to a power supply device and a computer via the watertight joint; wherein a rotary valve is further provided on the top of the pressure-bearing bladder, wherein the top of the rotary valve is connected to an injection / exhaust port; wherein a plurality of heat-conducting windows and observation windows are provided on the outer surface of the pressure-bearing bladder, wherein an installation port is provided on the outer wall of the pressure-bearing bladder close to the sensor placement cabin, wherein the installation port is connected to a sealing device, wherein the sealing device can be opened and closed, and wherein the test sensor and the reference sensor are placed in the sensor placement cabin via the installation port and the sealing device thereon.

[0006] Furthermore, the top of the rotary valve is connected to the injection / exhaust port via a flange, and 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 is snapped with the female buckle, thereby locking the sealing cover and the fixing ring.

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

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

[0010] On the other hand, the present invention provides a long-term calibration method for a seawater salinity sensor, which is implemented based on the device for long-term calibration of a seawater salinity sensor, and includes the following steps: S1: Place the test sensor and the reference sensor in the sensor placement cabin through the installation port, and connect them to the watertight joints respectively, close the sealing device, inject the seawater with known salinity that has been exhausted and sterilized into the device for long-term calibration of the seawater salinity sensor, so that the liquid level rises above the rotary valve, and after the residual gas in the device is removed, close the rotary valve to make the inside of the device filled with seawater; 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 operation 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; 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, control the pressure inside the pressure tank to be constant at each set pressure point, and measure the pressure fluctuation ΔP of the reference sensor. 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 values ​​of the test sensor are 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; S4: placing the calibrated test sensor and reference sensor into the device for long-term calibration of seawater salinity sensor at fixed intervals, filling with seawater of known salinity, keeping the device airtight, and immersing the device in the liquid inside the thermostatic bath, controlling the temperature value of the thermostatic bath to decrease step by step within the calibration temperature range, determining the difference in temperature and conductivity values ​​between the test sensor and the reference sensor at different temperatures, 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 sensor at fixed intervals, filling 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, determining the difference in pressure indication of the test sensor and the reference sensor, 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, repeat S1-S3 to recalibrate the test sensor.

[0011] The beneficial effects of the present invention are as follows: 1. The method for long-term calibration of seawater salinity sensor provided by the present invention can calibrate the temperature, conductivity and pressure of the sensor, improve the accuracy and stability of salinity sensor calibration, and reduce the error caused by water depth change and seawater volatilization; 2. The device for long-term calibration of seawater salinity sensor 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; 3. The size design of the device for long-term calibration of seawater salinity sensor provided by the present invention is suitable for small test environment, making the calibration process more flexible and convenient, reducing the calibration cost and improving the economic benefits of the laboratory. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a front view of a device for long-term calibration of a seawater salinity sensor provided by the present invention.

[0013] 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.

[0014] Figure 3 It is a schematic diagram of the structure of the sealing device provided by the present invention.

[0015] In the figure: 1- filling / exhaust port; 2-rotating 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

[0016] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only embodiments of a part of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0017] 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 the watertight joint 3 is fixed on the top of the pressure-bearing bladder 5. The test sensor and the reference sensor are connected to a power supply device and a computer through the watertight joint 3.

[0018] 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 is a rotary ball valve with a through hole diameter of 2-6 cm, which can withstand unidirectional pressure.

[0019] 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 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 mounting port 8 and the sealing device thereon.

[0020] The sealing device includes a sealing cover 9 and a fixing ring 10. The fixing ring 10 is welded to the pressure-bearing bladder 5. The diameter of the central through hole of the fixing ring 10 is adapted to the diameter of the mounting opening 8. A sealant may also be applied to the connection between the fixing ring 10 and the mounting opening 8 to further enhance the sealing performance.

[0021] 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 is snapped with the female buckle 14, thereby locking the sealing cover 9 and the fixing ring 10.

[0022] 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 engages with the groove 12 to improve the sealing performance of the pressure-bearing bladder 5 .

[0023] The pressure-bearing bladder 5 is made of one or more layered structures of polyurethane material, nitrile rubber, and fluorosilicone rubber by extrusion and compounding, with a thickness of 0-5.0 mm and a pressure resistance range of 0-60 MPa.

[0024] The heat-conducting window 7 is 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 window 7 is connected to the pressure bladder 5 by 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.

[0025] The observation window 4 is made of high-strength and high-transparency borosilicate glass, which can conveniently check the installation position and probe status of the sensor inside the pressure bladder 5.

[0026] The invention also provides a method for long-term calibration of a seawater salinity sensor, comprising the following steps.

[0027] S1: Place the test sensor and the reference sensor in the sensor placement cabin 6 through the installation port 8, and connect them to the watertight joint 3 respectively, close the sealing device, inject the vented and sterilized seawater of known salinity into the device for calibrating the seawater salinity sensor, so that the liquid level rises to above the rotary valve 2, and after removing the residual gas inside the device, close the rotary valve 2 to make the inside of the device filled with seawater.

[0028] 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 it 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.

[0029] 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 insulation time.

[0030] 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 it is less than ±0.005℃ / 15min, record 5 groups of pressure measurement values ​​of test sensors and reference sensors, and take the average value of the 5 groups of pressure measurement values ​​as the pressure measurement value corresponding to the test sensor and reference sensor at the set pressure point, and 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. The pressure measurement value of the test sensor is calibrated by regressing the pressure measurement value corresponding to each set pressure point in the calibration pressure range.

[0031] 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.

[0032] 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.

[0033] 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 sensor 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 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 thereby determining the data drift of the temperature indication and conductivity indication of the test sensor over time.

[0034] 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.

[0035] 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 relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within 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: The pressure-bearing bladder (5) is provided with a sensor placement cabin (6), 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 bladder (5), and the test sensor and the reference sensor are connected to a power supply device and a computer via the watertight joint (3); The top of the pressure-bearing bladder (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 outer surface of the pressure-bearing sac (5) is provided with a plurality of heat-conducting windows (7) and observation windows (4); the outer wall of the pressure-bearing sac (5) on a side close to the sensor placement cabin (6) is provided with a mounting opening (8); the mounting 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 mounting 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 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 bladder (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 hingedly connected to one end of the fixing ring (10); the other end of the sealing cover (9) is provided with a male buckle (13); 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) engages with the groove (10), thereby improving the sealing performance of the pressure-bearing bladder (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) is made of one or more layered structures of polyurethane material, nitrile rubber, and fluorosilicone rubber by extrusion and composite, with 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) by using a cold vulcanization process.

6. A long-term calibration method for a seawater salinity sensor, implemented based on a 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: placing the test sensor and the reference sensor in the sensor placement cabin (6) through the installation port (8), and connecting them to the watertight joints (3) respectively, closing the sealing device, injecting the seawater of known salinity that has been exhausted and sterilized into the device for long-term calibration of the seawater salinity sensor, so that the liquid level rises to a level higher than the rotary valve (2), and after removing the residual gas in the device, closing the rotary valve (2) so that the inside of the device is filled with seawater; 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 operation 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; 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, control the pressure inside the pressure tank to be constant at each set pressure point, and measure the pressure fluctuation ΔP of the reference sensor. 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 values ​​of the test sensor are 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; S4: placing the calibrated test sensor and reference sensor into the device for long-term calibration of seawater salinity sensor at fixed intervals, filling with seawater of known salinity, keeping the device airtight, and immersing the device in the liquid inside the thermostatic bath, controlling the temperature value of the thermostatic bath to decrease step by step within the calibration temperature range, determining the difference in temperature and conductivity values ​​between the test sensor and the reference sensor at different temperatures, 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 sensor at fixed intervals, filling 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, determining the difference in pressure indication of the test sensor and the reference sensor, 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, repeat S1-S3 to recalibrate the test sensor.

Images