Solution concentration measuring instrument and method based on white light interference and compensation plate rotation method

Abstract

The present invention provides a solution concentration measuring instrument and method based on white light interference and compensation plate rotation method. The solution concentration measuring instrument includes a white light source, a convex lens, a beam splitter, a compensation plate, a first reflector, a sample pipe, a second reflector and a color camera; the sample pipe is placed in a measurement light path, and a solution to be measured is stored in the sample pipe; the convex lens, the beam splitter, the compensation plate and the first reflector constitute one measurement light path, and the convex lens, the beam splitter, the sample pipe and the second reflector constitute another measurement light path; the convex lens is used to straighten the white light source into a parallel light beam, and the beam splitter is used to split the light beam into two beams that pass through different paths and then merge to form interference fringes; the color camera is used to image the interference fringes; the compensation plate is rotatable by a motor, and the imaging position of the interference fringes on the color camera is adjusted by rotating the compensation plate; the motor includes an encoder, and the encoder is used to read the rotation angle of the compensation plate.

Description

Technical Field

[0001] The present invention relates to the field of optical measurement technology, in particular to a solution concentration measuring instrument and method based on white light interference and compensation plate rotation method. Background Art

[0002] Traditional methods for measuring solution concentration have significant defects. Handheld refractometers have low accuracy, are significantly affected by ambient temperature, and require frequent calibration. Although fully automatic refractometers improve accuracy, they are expensive and cannot be continuously monitored, making them unsuitable for dynamic production processes. The conductivity method can only measure the concentration of ionic solutions and is completely ineffective for non-conductive substances (such as sugars and alcohols). The measurement results are significantly affected by temperature and require constant temperature control, which increases the complexity of the system. White light interferometry technology can achieve high-precision solution concentration measurement by detecting the offset or spectral phase change of the zero-order fringes of white light interference. It has advantages such as zero coherence length and wide spectral response, but it has not yet been widely used in the field of solution concentration detection. Based on the principle of white light interferometry, the present invention proposes a new solution concentration measuring instrument to address the shortcomings of the existing technology. Summary of the Invention

[0003] The main technical problem to be solved by the present invention is to provide a solution concentration measuring instrument and measurement method based on the principle of white light interferometry and compensation plate rotation method, which detects the change of the refractive index of the solution with high precision in a non-contact manner and then infers its concentration.

[0004] In order to solve the above technical problems, the present invention provides a solution concentration measuring instrument based on white light interferometry and compensation plate rotation method, including a white light source, a convex lens, a beam splitter, a compensation plate, a first reflector, a sample pipe, a second reflector and a color camera;

[0005] The convex lens, beam splitter, compensation plate, first reflector, and second reflector constitute a measuring light path, the sample pipe is placed in the measuring light path, and the sample pipe contains a solution to be measured; the convex lens, beam splitter, compensation plate, and first reflector constitute one measuring light path, and the convex lens, beam splitter, sample pipe, and second reflector constitute another measuring light path;

[0006] The convex lens is used to align the white light source into a parallel beam, and the beam splitter is used to split the light beam into two beams that pass through different paths and then merge to form interference fringes; the color camera is used to image the interference fringes;

[0007] The compensation plate is rotatable by a motor, and the imaging position of the interference fringes on the color camera is adjusted by rotating the compensation plate; the motor includes an encoder, and the encoder is used to read the rotation angle of the compensation plate.

[0008] In a preferred embodiment, the solution concentration measuring instrument further includes a temperature sensor and a pressure sensor, and the temperature sensor and the pressure sensor are disposed on the sample pipe.

[0009] In a preferred embodiment, the temperature sensor includes a thermistor, which is placed in the solution to be tested and is used to detect changes in the solution temperature.

[0010] In a preferred embodiment, a pressure balancing device is installed on the sample pipe, and the pressure balancing device is used to adjust the air pressure or hydraulic pressure in the sample pipe. The pressure balancing device is electrically connected to the pressure sensor.

[0011] In a preferred embodiment, the pressure balancing device includes a pressure regulating valve or a pressure stabilizer.

[0012] In a preferred embodiment, the encoder adopts a high-precision absolute value encoder, and the resolution of the encoder is greater than or equal to 16 bits.

[0013] In a preferred embodiment, the sample channel is a closed flow channel made of a light-transmitting material.

[0014] In order to solve the above technical problems, the present invention also provides a solution concentration measurement method based on white light interferometry and compensation plate rotation method, including the solution concentration measuring instrument based on white light interferometry and compensation plate rotation method, comprising the following steps:

[0015] Step A: A white light source provides white light, which is collimated by a convex lens to form parallel light, and the parallel light is then split into a first light beam and a second light beam by a beam splitter;

[0016] Step B: The first light beam passes through the rotatable compensation plate and the first reflector in sequence, and is then reflected by the first reflector to the beam splitter; the second light beam passes through the sample tube and the second reflector in sequence, and is then reflected by the second reflector to the beam splitter; the first light beam and the second light beam are combined into one beam by the beam splitter and then emitted to the color camera, forming an interference light path;

[0017] Step C, driving the compensation plate to rotate by a motor, adjusting the incident angle of the first light beam by rotating the compensation plate, changing the compensation optical path, and causing the first light beam and the second light beam to form white light interference fringes;

[0018] Step D: reading the rotation angle of the compensation plate in real time through an encoder, and calculating the change in optical path difference by combining Snell's law and a second-order mathematical model of Taylor expansion;

[0019] Step E: inverting the solution concentration based on the correlation between the optical path difference and the refractive index of the solution.

[0020] In a preferred embodiment, in step D, the steps for calculating the optical path difference variation are as follows:

[0021] Assume that the initial tilt angle of the compensation plate is , refractive index ,thickness ; According to Snell's law, the initial refraction angle satisfy: ;

[0022] When the compensation plate rotates an additional angle around the initial tilt direction When the total incident angle becomes , rotate clockwise to , counterclockwise rotation is , corresponding to the total refraction angle satisfy: ;

[0023] Under the small angle approximation (Δθ≪1 rad), Taylor expansion is performed on the left side and the linear terms are retained: ;

[0024] Assume that the refraction angle deviation is ,Right now , substituting into Snell's law, we get: ;

[0025] Combined with initial conditions , which is finally simplified to:

[0026]

[0027] ;

[0028] The optical path of the compensation plate when not rotated is: ;

[0029] Clockwise rotation hour: ;

[0030] Counterclockwise rotation hour: ;

[0031] Expand Second-order terms: ;

[0032] The change in optical path difference is: ;

[0033] Change in solution refractive index The optical path difference caused by: ;

[0034] Equilibrium conditions The solution is:

[0035] .

[0036] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0037] 1. Solution concentration measurement using white light interferometry and compensation plate rotation: A convex lens, beam splitter, compensation plate, first reflector, and second reflector form a measurement optical path. A sample tube containing the solution to be measured is placed in the measurement optical path. The convex lens, beam splitter, compensation plate, and first reflector form one measurement optical path, while the convex lens, beam splitter, sample tube, and second reflector form another measurement optical path. Changes in the solution's refractive index cause changes in the optical path difference. Rotating the compensation plate changes the compensation optical path, and the solution concentration is inverted based on the rotation angle.

[0038] 2. High-precision rotation compensation technology: An encoder-driven rotatable compensation plate replaces the traditional translation device. Combined with a 16-bit resolution encoder, it achieves micro-angle adjustment (accuracy up to 0.0055°) without mechanical wear, significantly improving optical path compensation accuracy.

[0039] 3. Nonlinear compensation model: Based on Snell's law, a second-order Taylor expansion model of the compensation plate rotation angle and optical path difference is derived to solve the nonlinear error problem during large-angle rotation;

[0040] 4. Dynamic compensation of environmental parameters: Temperature and pressure sensors are set up to monitor environmental parameters in real time and compensate for the effects of temperature and pressure on measurement through algorithms. The integrated temperature and pressure sensors eliminate environmental interference in real time through preset temperature-refractive index and pressure-refractive index compensation formulas. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A schematic structural diagram of a solution concentration measuring instrument in a preferred embodiment of the present invention;

[0042] Figure 2 Schematic diagram of imaging of interference fringes on a color camera in a preferred embodiment of the present invention;

[0043] Figure 3 is a graph showing the relationship between alcohol concentration and refractive index in a preferred embodiment of the present invention;

[0044] Figure 4 This is a mathematical model diagram of the compensation plate rotation angle and refractive index change value in the preferred embodiment of the present invention;

[0045] Figure 5 A graph showing the relationship between alcohol concentration and rotation angle in a preferred embodiment of the present invention;

[0046] Figure 6 This is a temperature-refractive index compensation curve diagram in a preferred embodiment of the present invention;

[0047] Figure 7This is a pressure-refractive index compensation curve diagram in a preferred embodiment of the present invention;

[0048] Explanation of the accompanying drawings: 1. Sample pipe; 2. Pressure sensor; 3. White light source; 4. Convex lens; 5. Beam splitter; 6. Color camera; 7. Compensation plate; 8. First reflector; 9. Temperature sensor; 10. Motor; 11. Second reflector. DETAILED DESCRIPTION

[0049] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0050] In the description of the present invention, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0051] In the description of the present invention, it should be noted that, unless otherwise clearly stipulated and limited, the terms "installed", "provided with", "set / connected", "connected", etc. should be understood in a broad sense. For example, "connection" can be a wall-mounted connection, a detachable connection, or an integral connection. It can be a mechanical connection or an electrical connection. It can be a direct connection or an indirect connection through an intermediate medium. It can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0052] refer to Figure 1, this embodiment provides a solution concentration measuring instrument based on white light interference and compensation plate 7 rotation method, including a white light source 3, a convex lens 4, a beam splitter 5, a compensation plate 7, a first reflector 8, a sample pipe 1, a second reflector 11 and a color camera 6; the convex lens 4, the beam splitter 5, the compensation plate 7, the first reflector 8, the second reflector 11 constitute a measurement light path, the sample pipe 1 is placed in the measurement light path, and the sample pipe 1 contains a solution to be measured; the convex lens 4, the beam splitter 5, the compensation plate 7, the first reflector 8 constitute one measurement light path, and the convex lens 4, the beam splitter 5, the sample pipe, and the second reflector 11 constitute another measurement light path; the convex lens 4 is used to straighten the white light source 3 into a parallel light beam, the beam splitter 5 is used to split the light beam into two beams that pass through different paths and then merge to form interference fringes; the color camera 6 is used to image the interference fringes (such as Figure 2 The compensation plate 7 is rotatably driven by a motor 10. The compensation plate 7 is rotated to adjust the imaging position of the interference fringes on the color camera 6 to ensure that the two light beams have a fixed optical path difference and the central wavelength has a zero optical path difference. The motor 10 includes an encoder for reading the rotation angle of the compensation plate 7.

[0053] This device measures solution concentration by rotating a compensating plate 7 to change the compensation optical path until the colored fringes reappear at the original pixel position on the CMOS camera target surface. Specifically, a white light source 3 is used to provide white light, and a convex lens 4 is used to calibrate the white light into a parallel beam to ensure beam uniformity. A beam splitter 5 is used to split the parallel beam into two beams, which then pass through different paths and then merge to form interference fringes. The compensating plate 7 is driven to rotate by a motor 10 to adjust the optical path difference and restore the interference fringes to their initial position. A first reflector 8 and a second reflector 11 reflect the two beams separately, causing them to pass through different paths and then merge again. A sample tube 1 is used to contain the solution to be tested, affecting the optical path of one of the beams. A color camera 6 is used to capture images of the interference fringes and record the changes in the fringes' position. Due to the mutual interference of the two beams, interference fringes are observed on the photosensitive surface of the color camera 6. The refractive index of a solution typically changes with changes in its concentration. When the light beam passes through the solution to be tested, the change in the refractive index of the solution will cause the length of the light propagation path in it to change, thereby causing a change in the optical path difference. Through the cooperation of the motor 10 and the encoder, the motor 10 drives the compensation plate 7 to rotate, and the encoder reads the rotation angle to calculate the change in the optical path difference.

[0054] Assume the diameter of the pipe is R and the refractive index is n. The optical path length of light in the solution is nd. If the refractive index changes by Δn, the optical path difference will change accordingly by Δnd. For one round trip, the total optical path difference is 2Δnd. The zero-order fringe corresponds to the position where the optical path difference is zero. For white light, the zero-order fringe remains white, flanked by colored fringes. When the optical path difference changes, the zero-order fringe shifts accordingly.

[0055] By rotating the compensation plate 7 to change the compensation optical path, the colored stripes reappear at the original pixel position on the CMOS camera target surface, overlapping with the white stripes. There is a certain relationship between the rotation angle and the change in the optical path difference. By reading the rotation angle of the encoder, the change in the optical path difference can be calculated, and then the concentration of the solution can be inverted based on the relationship between the optical path difference and the refractive index and the relationship between the refractive index and the concentration.

[0056] The white light interferometry and compensation plate 7 rotation method can achieve high-precision solution concentration measurement without direct contact with the solution, making it suitable for applications with special sample requirements. The rotation of the compensation plate 7 allows for real-time observation of changes in interference fringes, facilitating dynamic measurement.

[0057] To mitigate environmental influences on concentration measurements, in this embodiment, the solution concentration meter also includes a temperature sensor 9 and a pressure sensor 2, which are disposed on the sample pipe 1. By measuring changes in solution temperature and pressure, these sensors provide environmental compensation for the measurement results, improving measurement accuracy. Simultaneously, these sensors monitor both solution temperature and pressure, providing more comprehensive experimental data.

[0058] Specifically, the temperature sensor 9 includes a thermistor, which is placed in the solution to be measured and is used to detect changes in the solution temperature. The thermistor can accurately measure changes in the solution temperature and provide high-precision temperature data.

[0059] A pressure balancing device is installed on the sample pipe 1. The pressure balancing device is used to adjust the air pressure or hydraulic pressure within the sample pipe 1. By adjusting the air pressure or hydraulic pressure within the sample pipe 1 by the pressure balancing device, the stability of the measurement environment is ensured. The pressure balancing device is electrically connected to the pressure sensor 2 and can adjust the pressure in real time based on the feedback from the pressure sensor 2.

[0060] The pressure balancing device includes a pressure regulating valve or a pressure stabilizer. Both the pressure regulating valve and the pressure stabilizer are existing devices and will not be described in detail here. The pressure regulating valve or the pressure stabilizer can accurately regulate and stabilize the pressure in the sample pipe 1. Selecting an appropriate device based on specific needs ensures accurate pressure regulation.

[0061] To achieve high-precision measurements, the encoder uses a high-precision absolute encoder with a resolution of 16 bits or greater. Conventional optical path compensation often uses a mirror translation or tilt mechanism, which suffers from large mechanical errors and slow response speeds. In this embodiment, the combination of a rotating compensation plate 7 and an encoder enables high-precision adjustment without mechanical wear. The compensation plate 7 is attached to an absolute encoder with n-bit resolution, such as a 16-bit encoder, achieving a resolution of 1 in 65,536, corresponding to an angular resolution of 0.0055°.

[0062] The sample channel 1 is a closed flow channel made of a light-transmitting material. This allows for easy passage of light, ensuring measurement accuracy. The closed flow channel design prevents solution leakage, ensuring a safe and stable measurement environment.

[0063] This embodiment also provides a solution concentration measurement method based on white light interferometry and the compensation plate 7 rotation method, including the solution concentration measuring instrument based on the white light interferometry and the compensation plate 7 rotation method, comprising the following steps:

[0064] Step A: The white light source 3 provides white light, which is collimated by the convex lens 4 to form parallel light, and the parallel light is then split into a first light beam and a second light beam by the beam splitter 5;

[0065] Step B: The first light beam passes through the rotatable compensation plate 7 and the first reflector 8 in sequence, and is then reflected by the first reflector 8 to the convex lens 4 of the beam splitter 5; the second light beam passes through the sample tube 1 and the second reflector 11 in sequence, and is then reflected by the second reflector 11 to the convex lens 4 of the beam splitter 5; the first and second light beams are combined into one beam by the beam splitter 5 and then emitted to the color camera 6, forming an interference light path;

[0066] Step C: driving the compensation plate 7 to rotate by the motor 10, adjusting the incident angle of the first light beam by rotating the compensation plate 7, changing the compensation optical path, so that the first light beam and the second light beam form white light interference fringes;

[0067] Step D: reading the rotation angle of the compensation plate 7 in real time through an encoder, and calculating the change in optical path difference by combining Snell's law and a second-order mathematical model of Taylor expansion;

[0068] Step E: inverting the solution concentration based on the correlation between the optical path difference and the refractive index of the solution.

[0069] The measurement is carried out with alcohol as the solution, according to the relationship between alcohol concentration and refractive index (such as Figure 3 ), in step D, the steps for calculating the optical path difference variation are as follows:

[0070] Assume that the initial tilt angle of the compensation plate 7 is , refractive index ,thickness ; According to Snell's law, the initial refraction angle satisfy: ;

[0071] When the compensation plate 7 rotates an additional angle around the initial tilt direction When the total incident angle becomes , rotate clockwise to , counterclockwise rotation is , corresponding to the total refraction angle satisfy: ;

[0072] Under the small angle approximation (Δθ≪1 rad), Taylor expansion is performed on the left side and the linear terms are retained: ;

[0073] Assume that the refraction angle deviation is ,Right now , substituting into Snell's law, we get: ;

[0074] Combined with initial conditions , which is finally simplified to:

[0075]

[0076] ;

[0077] The optical path of the compensation plate 7 when not rotated is: ;

[0078] Clockwise rotation hour: ;

[0079] Counterclockwise rotation hour: ;

[0080] Expand To the second-order term: ;

[0081] The change in optical path difference is: ;

[0082] Change in solution refractive index The optical path difference caused by: ;

[0083] Equilibrium conditions The solution is:

[0084] .

[0085] like Figure 4 , assuming that the initial inclination of the compensation plate 7 is The thickness t of the compensation plate 7 is 2 mm, the diameter d of the pipe is 1 cm, the compensation plate 7 is made of glass with a refractive index of 1.5, and the relationship between the alcohol concentration and the rotation angle is derived according to the calculation of the optical path difference change in step D (as shown in FIG. Figure 5 ), when detected =0.1°, the data processing unit calculates =0.0023, corresponding to an increase of 5.7% in alcohol concentration.

[0086] In the embodiment, dynamic compensation of environmental parameters is also performed, and temperature and pressure compensation is performed on the solution concentration measurement by setting the temperature sensor 9 and the pressure sensor 2. The temperature sensor 9 and the pressure sensor 2 monitor the solution environmental parameters in real time and compensate the influence of temperature and pressure on the refractive index through the algorithm. The temperature sensor 9 and the pressure sensor 2 compensate for the influence of temperature and pressure on the solution. Figure 5 、 Figure 6 .

[0087] like Figure 5 Temperature compensation involves adding a temperature compensation element, such as a thermistor, to the solution concentration meter and using it in conjunction with the sensor. The resistance of the thermistor changes with temperature. By measuring the change in the thermistor's resistance, the temperature change can be determined. Based on the pre-established temperature compensation model, the measured refractive index of the solution can be compensated in real time. The calculation formula is as follows:

[0088] ;

[0089] Where T is the temperature, is the pressure value, is the salinity parameter, is the wavelength of the light source.

[0090] like Figure 6 Pressure compensation is to add a pressure balancing device, such as installing a gas pressure regulating valve or a liquid pressure stabilizer, to keep the pressure in the measurement environment relatively stable and reduce the impact of pressure changes on the solution refractive index measurement. The calculation formula is as follows:

[0091] ;

[0092] Where T is the temperature, is the pressure value, is the salinity parameter, is the wavelength of the light source.

[0093] The above is only a preferred specific embodiment of the present invention, but the design concept of the present invention is not limited to this. Any technician familiar with this technical field who uses this concept to make non-substantial changes to the present invention within the technical scope disclosed by the present invention shall be deemed to infringe the scope of protection of the present invention.

Claims

1. A method for measuring solution concentration based on white light interferometry and compensation plate rotation, characterized in that: The solution concentration measurement method comprises the following steps: Step A: A white light source provides white light, which is collimated by a convex lens to form parallel light, and the parallel light is then split into a first light beam and a second light beam by a beam splitter; Step B: The first light beam passes through the rotatable compensation plate and the first reflector in sequence, and is then reflected by the first reflector to the beam splitter; the second light beam passes through the sample tube and the second reflector in sequence, and is then reflected by the second reflector to the beam splitter; the first and second light beams are combined into one beam by the beam splitter and then emitted to the color camera, forming an interference light path; Step C, driving the compensation plate to rotate by a motor, adjusting the incident angle of the first light beam by rotating the compensation plate, changing the compensation optical path, so that the first light beam and the second light beam form white light interference fringes; Step D: Read the rotation angle of the compensation plate in real time through an encoder, and calculate the change in optical path difference by combining Snell's law and a second-order mathematical model of Taylor expansion; Step E: inverting the solution concentration based on the correlation between the optical path difference and the refractive index of the solution; In step D, the steps for calculating the optical path difference variation are as follows: Assume that the initial tilt angle of the compensation plate is θ0, and the refractive index n c , thickness t; According to Snell's law, the initial refraction angle θ′0 satisfies: sinθ0=n c sinθ′0; When the compensation plate is rotated by an additional angle Δθ around the initial tilt direction, the total incident angle becomes θ total =θ0±Δθ, clockwise rotation is +Δθ, counterclockwise rotation is -Δθ, corresponding to the total refraction angle θ′ total Satisfies: sin(θ0±Δθ)=n c sinθ′ total ; Under Δθ<<1rad, perform Taylor expansion on the left side and retain the linear terms: sin(θ0±Δθ)≈sinθ0±cosθ0·Δθ; Assume that the refraction angle deviation is δθ′, that is, θ′ total =θ′0±δθ′, and substituting into Snell’s law, we get: Combined with initial conditions Finally it simplifies to: The optical path of the compensation plate when not rotated is: When rotating clockwise +Δθ: When rotating -Δθ counterclockwise: Expand To the second-order term: The change in optical path difference is: Optical path difference caused by the change in the refractive index of the solution Δn: ΔL solution =Δn·d; Equilibrium condition ΔL comp =ΔL solution The solution is:

2. The method for measuring solution concentration based on white light interferometry and compensation plate rotation method according to claim 1, characterized in that: A solution concentration measuring instrument based on white light interference and compensation plate rotation method includes a white light source, a convex lens, a beam splitter, a compensation plate, a first reflector, a sample pipe, a second reflector and a color camera; The convex lens, beam splitter, compensation plate, first reflector, and second reflector constitute a measuring light path, the sample pipe is placed in the measuring light path, and the sample pipe contains a solution to be measured; the convex lens, beam splitter, compensation plate, and first reflector constitute one measuring light path, and the convex lens, beam splitter, measuring pipe, and second reflector constitute another measuring light path; The convex lens is used to align the white light source into a parallel beam, and the beam splitter is used to split the light beam into two beams that pass through different paths and then merge to form interference fringes; the color camera is used to image the interference fringes; The compensation plate is rotatable by a motor, and the imaging position of the interference fringes on the color camera is adjusted by rotating the compensation plate; The motor includes an encoder, and the encoder is used to read the rotation angle of the compensation plate.

3. The method for measuring solution concentration based on white light interferometry and compensation plate rotation method according to claim 2, characterized in that: The solution concentration measuring instrument further comprises a temperature sensor and a pressure sensor, and the temperature sensor and the pressure sensor are arranged on the sample pipe.

4. The method for measuring solution concentration based on white light interferometry and compensation plate rotation method according to claim 3, characterized in that: The temperature sensor includes a thermistor, which is placed in the solution to be tested and is used to detect changes in the solution temperature.

5. The method for measuring solution concentration based on white light interferometry and compensation plate rotation method according to claim 3, characterized in that: A pressure balancing device is installed on the sample pipeline, and the pressure balancing device is used to adjust the air pressure or hydraulic pressure in the sample pipeline. The pressure balancing device is electrically connected to the pressure sensor.

6. The method for measuring solution concentration based on white light interferometry and compensation plate rotation method according to claim 5, characterized in that: The pressure balancing device includes a pressure regulating valve or a pressure stabilizer.

7. The method for measuring solution concentration based on white light interferometry and compensation plate rotation method according to claim 2, characterized in that: The encoder adopts a high-precision absolute value encoder, and the resolution of the encoder is greater than or equal to 16 bits.

8. The method for measuring solution concentration based on white light interferometry and compensation plate rotation method according to claim 2, characterized in that: The sample pipe is a closed flow channel made of light-transmitting material.

Images