CN111812049B - A transmission reference method and device for measuring water quality by spectrophotometry - Google Patents

Abstract

The invention provides a transmission reference mode and a transmission reference device for measuring water quality by a spectrophotometry, comprising a shell, a lower fixed plate, a first high-pressure valve, a cuvette, a second high-pressure valve, an upper fixed plate, a compression bolt, a spring, a light-emitting unit and a light-receiving unit, wherein the lower fixed plate is arranged on the shell; the lower fixing plate is provided with a liquid inlet and a liquid outlet; the light emitting unit emits light rays to penetrate through the cuvette and then is received by the light receiving unit. The transmission reference mode adopts a rear reference mode, so that the influence of the replacement of the colorimetric pool, the LED lamp, the slight displacement of the colorimetric pool or the light attenuation on the measurement result is reduced, recalibration is not needed, and the maintenance amount is reduced.

Description

A transmission reference method and device for measuring water quality by spectrophotometry

Technical Field

The invention relates to the technical field of measuring water bodies by using spectrophotometry, in particular to a transmission reference method and device for measuring water quality by using spectrophotometry.

Background Art

A spectroscope is a scientific instrument that decomposes complex light into spectral lines. It is composed of prisms or diffraction gratings, etc., and can be used to measure the light reflected from the surface of an object. The seven colors of sunlight are the part that the naked eye can separate, but if the sunlight is decomposed by a spectroscope and arranged by wavelength, visible light only occupies a very small range in the spectrum, and the rest are spectra that the naked eye cannot distinguish, such as infrared, microwaves, ultraviolet, X-rays, etc. By capturing light information with a spectrometer, developing it with photographic film, or displaying and analyzing it with a computerized automatic numerical display instrument, it is possible to determine what elements are contained in an object. This technology is widely used in the detection of air pollution, water pollution, food hygiene, metal industry, etc.

When the instruments on the market use spectrophotometry to measure water bodies, most of them do not use references or use spectroscopic incident references to correct the light source data of the spectrophotometer; among them, the spectroscopic incident reference is used to measure and compensate the light attenuation of the light source before the incident, that is, before the light enters the cuvette, the light attenuation is received and measured by the light receiving unit. However, due to the scaling of the cuvette, although the cuvette is cleaned before each measurement, some scaling cannot be cleaned off. Therefore, the existing correction method using spectroscopic incident reference does not take into account the contamination error of the cuvette, the light attenuation of the light passing through the cuvette, and the error of the displacement change of the cuvette. Such devices and practices on the market have large errors, resulting in large errors in the measurement results.

Summary of the invention

The technical problem to be solved by the present invention is to provide a transmission reference method and device for measuring water quality by spectrophotometry, reduce the influence of colorimetric dish, LED lamp displacement, light decay or pollution on the measurement result, and improve the measurement accuracy.

The present invention is achieved in the following way: a device for measuring water quality by spectrophotometry, comprising:

A shell, wherein the upper and lower ends of the shell are open;

A lower fixing plate, the lower fixing plate is provided with a liquid inlet and outlet; the lower fixing plate is fixedly connected to the lower end of the shell;

The first high-pressure valve; the bottom end of the cuvette is airtightly embedded in the first high-pressure valve and communicates with the first high-pressure valve; the first high-pressure valve is also fixedly connected to the shell; the liquid inlet and outlet of the first high-pressure valve are communicated with the body flow pipeline outside the shell;

A cuvette, wherein the upper and lower ends of the cuvette are open; the cuvette is placed in the housing, and the bottom end of the cuvette is airtightly embedded between the first high-pressure valve and the second high-pressure valve, and is in communication with the first high-pressure valve and the second high-pressure valve;

A second high-pressure valve, the top of the cuvette is airtightly embedded under the second high-pressure valve and communicates with the second high-pressure valve; the second high-pressure valve is also fixedly connected to the housing; the second inlet and outlet of the second high-pressure valve are communicated with the external space of the housing;

An upper fixing plate, wherein the upper fixing plate is provided with vertical screw holes; the upper fixing plate is fixedly connected to the top opening of the shell;

A clamping bolt, which is locked into the screw hole and supports the top end of the second high-pressure valve;

A spring, wherein the spring is sleeved on the clamping bolt, and the upper end of the spring abuts against the upper fixing plate, and the lower end of the spring abuts against the second high-pressure valve;

A light emitting unit, the light emitting unit is detachably connected to the left side of the housing, and emits light in a direction toward the cuvette;

A light receiving unit, the light receiving unit is detachably connected to the right side surface of the housing and is arranged facing the light emitting unit;

Wherein, the direction of the light path is: the light emitted by the light emitting unit penetrates the cuvette and is then received by the light receiving unit.

Furthermore, it also includes

A left lamp holder, a first through hole is provided on the left side of the shell; the left lamp holder is fixedly connected to the shell and embedded in the first through hole;

An emitting PCB board, the light-emitting unit is connected to the emitting PCB board; the emitting PCB board is also fixedly connected to the left lamp holder.

Furthermore, it also includes

Right lamp holder, a second through hole is provided on the right side surface of the shell; the right lamp holder is fixedly connected to the shell and embedded in the second through hole;

Receiving PCB board; the light receiving unit is connected to the receiving PCB board; the receiving PCB board is fixedly connected to the right lamp holder.

Furthermore, a resistance wire is wound around the outside of the cuvette.

Furthermore, it also includes an MCU, and the MCU is connected to the transmitting PCB board, the receiving PCB board and the resistance wire respectively.

The present invention also provides a transmission reference method for measuring water quality by spectrophotometry, including a reference value measurement process, a measured sample measurement process, and an error value measurement and compensation process:

(1) The benchmark value measurement process includes the following steps:

Step S11, first clean the cuvette, and then inject the sample solution M into the cuvette;

Step S12, the light emitting unit emits light to illuminate the cuvette, the light penetrates the sample solution M in the cuvette, and then is received by the light receiving unit to obtain a transmittance T1;

Step S13, calculating the reference concentration of the sample solution M according to the data received by the light receiving unit;

(2) The measurement process of the sample to be measured includes the following steps:

Step S21, first clean the cuvette, and then inject the solution N to be tested into the cuvette;

Step S22, the light emitting unit emits light to illuminate the cuvette, the light penetrates the solution N in the cuvette, and then is received by the light receiving unit to obtain a transmittance T2;

Step S23, calculating the preliminary concentration of the solution N to be tested according to the data received by the light receiving unit;

(3) The error value measurement and compensation process includes the following steps:

Step S31, first clean the cuvette, and then inject the sample solution M into the cuvette;

Step S32, the light emitting unit emits light to illuminate the cuvette, the light penetrates the sample solution M in the cuvette, and then is received by the light receiving unit to obtain a transmittance T3;

Step S33, calculating the reference concentration of the sample solution M according to the data received by the light receiving unit;

Step S34, comparing the reference concentration of the sample solution M with the benchmark concentration to obtain an error value;

Step S35: Compensate the error value to the preliminary concentration of the solution N to obtain the final concentration value of the solution N to be tested.

Furthermore, the base concentration, reference concentration of the sample solution M or the preliminary concentration of the sample solution N to be tested is calculated as follows:

Substitute the transmittance into the absorbance calculation formula A=-lgT, where T is the transmittance, and calculate the absorbance A;

Substitute the absorbance A into the Lambert-Beer law expression: A = abc; where a is the absorption coefficient, in units of L/(g·cm); b is the cuvette thickness, in units of cm; c is the solution concentration; A is the absorbance; calculate the solution concentration c, in units of g/L;

By plotting the absorbance A against the solution concentration c, the calibration curve of the photometric analysis is obtained, and finally the water sample value of the liquid to be tested is calculated.

Furthermore, in step S34, the error value=reference concentration of the sample solution M/base concentration.

Furthermore, in step S35, the final concentration value of the solution N to be tested = the initial concentration of the solution N to be tested * the error value.

The present invention has the following advantages: a transmission reference method and device for measuring water quality by spectrophotometry, comprising a housing, a lower fixing plate, a first high-pressure valve, a cuvette, a second high-pressure valve, an upper fixing plate, a clamping bolt, a spring, a light-emitting unit and a light-receiving unit; the lower fixing plate is provided with a liquid inlet and outlet; the light-emitting unit emits light that penetrates the cuvette and is then received by the light-receiving unit. The transmission reference method adopts a post-reference method to reduce the influence of the replacement of the cuvette, the LED lamp, the slight displacement of the cuvette or the light decay on the measurement result, so that recalibration is not required, and the maintenance amount is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further described below in conjunction with embodiments with reference to the accompanying drawings.

FIG. 1 is a left side view of the device according to the present invention.

FIG. 2 is a front view of the device according to the present invention.

FIG. 3 is a top view of the device according to the present invention.

FIG. 4 is a cross-sectional view taken along line E-E in FIG. 3 .

FIG. 5 is a schematic diagram of the internal structure of the cuvette of the present invention wound with a resistance wire.

FIG. 6 is a schematic structural diagram of the transmitting PCB board according to the present invention.

FIG. 7 is a schematic structural diagram of a receiving PCB board according to the present invention.

FIG. 8 is a flow chart of the reference method of the present invention.

9 to 20 are circuit diagrams of the present invention.

Description of reference numerals:

Shell 1, first through hole 11, second through hole 12;

Lower fixed plate 2, liquid inlet and outlet 21;

A first high-pressure valve 3; a first inlet and outlet 31, a first inlet and outlet 32, and a second inlet and outlet 33;

Cuvette 4, resistance wire 41;

Second high pressure valve 5; second inlet and outlet 34

Upper fixing plate 6, screw hole 61;

Tighten bolt 7;

Spring 8;

Light emitting unit 9;

A light receiving unit 10;

Left lamp holder 20;

Transmitting PCB board 30;

Right lamp holder 40;

Receiving PCB board 50;

Screw 60;

Sealing ring 70;

Liquid 80.

DETAILED DESCRIPTION

The overall concept of the present invention is as follows:

(1) Provide a new device for measuring water quality by spectrophotometry;

(2) The water sample value of the liquid to be tested is measured by using a transmission reference method, that is, a post-reference method, so that when the device replaces the cuvette 4 or the light-emitting unit 9 has a slight displacement or light decay, the measurement result will not be greatly affected. The specific principle is: first use a sample solution M to measure and measure its reference concentration. Each time the solution N to be tested is measured in the future, the solution N to be tested is measured once to obtain a preliminary concentration, and then the reference concentration of the sample solution M is measured again. Then, the reference concentration of the sample solution M measured this time is compared with the reference concentration of the initial measurement, so that the error value caused by the contamination or replacement of the cuvette 4 during the two sample solution M measurements or the light decay of the light source 9 is taken into account, thereby improving the measurement accuracy, comparing the error values of the two measurements, and compensating the error value to the preliminary concentration of the solution N to be tested, so as to obtain the final concentration.

Please refer to Figures 1 to 20. Figures 9 to 20 form a complete circuit diagram.

A device for measuring water quality by spectrophotometry of the present invention comprises:

A housing 1, wherein the upper and lower ends of the housing 1 are open;

A lower fixing plate 2, wherein the lower fixing plate 2 is provided with a liquid inlet and outlet 21; the lower fixing plate 2 is fixedly connected to the lower end of the housing 1;

A first high-pressure valve 3; the first high-pressure valve 3 comprises a first inlet and outlet 31, a first exhaust port, and a second inlet and outlet 32; the first high-pressure valve 3 is fixedly connected to the lower fixing plate 2 and is located in the housing 1, and the first high-pressure valve 3 is connected to the liquid inlet and outlet 21 in an airtight manner;

A cuvette 4, wherein the cuvette 4 is open at both ends; the cuvette 4 is placed in the housing 1, and the bottom end of the cuvette 4 is airtightly embedded in the first high-pressure valve 3 and communicated with the first high-pressure valve 3; in a specific embodiment, a sealing ring 70 is further provided at the connection between the lower end of the cuvette 4 and the first high-pressure valve 3; a sealing ring 70 is also provided at the connection between the upper end of the cuvette 4 and the second high-pressure valve 5; a resistance wire is wound around the outside of the cuvette, and the resistance wire is used to heat the liquid in the cuvette to eliminate impurities in the liquid;

The top of the cuvette 4 is open and airtightly embedded under the second high-pressure valve 5, and is in communication with the second high-pressure valve 5; the second high-pressure valve 5 is also fixedly connected to the housing 1; the air outlet of the second high-pressure valve 5 is in communication with the external space of the housing 1;

An upper fixing plate 6, wherein the upper fixing plate 6 is provided with a vertical screw hole 61; the upper fixing plate 6 is fixedly connected to the top opening of the housing 1;

A clamping bolt 7, wherein the clamping bolt 7 is locked into the screw hole 61 and supports the top end of the second high-pressure valve 5;

A spring 8, wherein the spring 8 is sleeved on the clamping bolt 7, and the upper end of the spring 8 abuts against the upper fixing plate 6, and the lower end of the spring 8 abuts against the second high-pressure valve 5;

A light emitting unit 9, wherein the light emitting unit 9 is detachably connected to the left side surface of the housing 1, and emits light in a direction toward the cuvette 4;

A light receiving unit 10, the light receiving unit 10 is detachably connected to the right side of the housing 1 and arranged facing the light emitting unit 9;

The light emitting unit 9 emits light that penetrates the cuvette 4 and is then received by the light receiving unit 10 .

Working principle: liquid is injected into the cuvette 4 through the liquid inlet and outlet 21; the light emitting unit 9 emits emission light, which penetrates the cuvette 4 and the liquid inside it, and is then received by the light receiving unit 10. Since the liquid in the cuvette 4 absorbs light of a specific wavelength in the emission light, the photometric value received by the light receiving unit 10 changes.

The device described in the present invention does not need to set a sensor at the outlet of the light-emitting unit 9 to correct the incident light. Instead, a reference coefficient is measured by injecting the liquid to be tested into the cuvette 4, and another reference coefficient is measured by injecting a reference liquid, such as pure water, into the cuvette 4. The two coefficients are compared to obtain the absorbance through calculation, and finally the water sample value of the liquid to be tested, that is, the concentration of a certain component, is calculated by bringing it into the range curve.

Also includes

The left lamp holder 20 is used to fix the transmitting PCB board 30, and the transmitting PCB board 30 is connected to the light-emitting unit 9, the light-emitting unit 9 is fixed and then electrically connected to the MCU. In a specific embodiment, the light-emitting unit 9 adopts an LED lamp. Since different substances have different absorption degrees for light of different wavelengths, therefore, corresponding to the measurement of liquid concentrations of different substances, different LED lamps need to be replaced to emit light of different wavelengths to meet the measurement of liquid concentrations of different substances; a first through hole 11 is provided on the left side surface of the shell 1; the left lamp holder 20 is fixedly connected to the shell 1. In a specific implementation, the left lamp holder 20 and the shell 1 are fixed by screws 60 and embedded in the first through hole 11.

It also includes an emission PCB board 30, and the light emitting unit 9 is connected to the emission PCB board 30; the emission PCB board 30 is fixedly connected to the left lamp holder 20, and in a specific embodiment, the two are connected by screws 60. The emission PCB 30 is used to fix the light emitting unit 9 and electrically connect the light emitting unit 9 and the MCU, and can be fixed by welding. In other embodiments, the emission PCB board 30 can be directly replaced by a wire.

Also includes

The right lamp holder 40 has a second through hole 12 on the right side surface of the housing 1 ; the right lamp holder 40 is fixedly connected to the housing 1 . In a specific embodiment, the two are fastened by screws 60 and embedded in the second through hole 12 .

The receiving PCB board 50; the light receiving unit 10 is connected to the receiving PCB board 50; the receiving PCB board 50 is fixedly connected to the right lamp holder 40. In a specific embodiment, the two are also fastened by screws 60. The receiving PCB board 50 fixes the light receiving unit 10, which can be fixed by welding, and at the same time, the light receiving unit 10 and the MCU are electrically connected to play a switching role. In other embodiments, the PCB board 50 can also be directly replaced by a wire.

The cuvette 4 is also wrapped with a resistance wire 41, through which the cuvette 4 can be heated, thereby heating the liquid in the cuvette 4 for catalysis. The purpose of setting the resistance wire 41 is to directly prepare the solution to be tested in the cuvette 4, that is, inject the constituent liquid of the solution to be tested into the cuvette 4, and then control the resistance wire 41 to reach a predetermined temperature to perform a catalytic reaction, thereby directly obtaining the solution to be tested without preparing the solution to be tested in advance. During the heating process of the resistance wire 41, the cuvette is sealed by the first high-pressure valve 3 and the second high-pressure valve 5 to ensure the high temperature and high pressure required in the catalytic reaction.

The MCU is also included, and the MCU is connected to the transmitting PCB board 30, the receiving PCB board 50 and the resistance wire 41 respectively. The MCU controls the light emitting unit 9 to emit light; the MCU controls the resistance wire 41 to work; the MCU receives the data measured by the light receiving unit 9, and processes the data to finally obtain the measured value. In a specific implementation, the first high-pressure valve 3 and the second high-pressure valve 5 are also connected to the MCU and controlled by the MCU.

The present invention also provides a transmission reference method for measuring water quality by spectrophotometry, including a reference value measurement process, a measured sample measurement process, and an error value measurement and compensation process:

(1) The benchmark value measurement process includes the following steps:

Step S11, first clean the cuvette 4, and then inject the sample solution M into the cuvette 4;

Step S12, the light emitting unit 9 emits light to illuminate the cuvette 4, the light penetrates the sample solution M in the cuvette 4, and then is received by the light receiving unit 10, and the transmittance T1 is obtained;

Step S13, calculating the reference concentration of the sample solution M according to the data received by the light receiving unit 10;

(2) The measurement process of the sample to be measured includes the following steps:

Step S21, first clean the cuvette, and then inject the solution N to be tested into the cuvette;

Step S22, the light emitting unit emits light to illuminate the cuvette, the light penetrates the solution N in the cuvette, and then is received by the light receiving unit to obtain a transmittance T2;

Step S23, calculating the preliminary concentration of the solution N to be tested according to the data received by the light receiving unit;

(3) The error value measurement and compensation process includes the following steps:

Step S31, first clean the cuvette, and then inject the sample solution M into the cuvette;

Step S32, the light emitting unit emits light to illuminate the cuvette, the light penetrates the sample solution M in the cuvette, and then is received by the light receiving unit to obtain a transmittance T3;

Step S33, calculating the reference concentration of the sample solution M according to the data received by the light receiving unit;

Step S34, comparing the reference concentration of the sample solution M with the benchmark concentration to obtain an error value;

Step S35: Compensate the error value to the preliminary concentration of the solution N to obtain the final concentration value of the solution N to be tested.

Calculation method for the base concentration, reference concentration of sample solution M or the preliminary concentration of the sample solution N to be tested:

Substitute the transmittance into the absorbance calculation formula A=-lgT, where T is the transmittance, and calculate the absorbance A;

Substitute the absorbance A into the Lambert-Beer law expression: A = abc; where a is the absorption coefficient, in units of L/(g·cm); b is the cuvette thickness, in units of cm; c is the solution concentration; A is the absorbance; calculate the solution concentration c, in units of g/L;

By plotting the absorbance A against the solution concentration c, the calibration curve of the photometric analysis is obtained, and finally the water sample value of the liquid to be tested is calculated.

In the step S34, the error value = the reference concentration of the sample solution M / the base concentration.

In step S35, the final concentration value of the solution N to be tested = the initial concentration of the solution N to be tested * the error value. That is, the reference concentration of the sample solution M / the benchmark concentration = the final concentration value of the solution N to be tested / the initial concentration of the solution N to be tested.

Specific embodiment:

The light emitting unit 9 uses an LED lamp. In the embodiment shown in the drawings, there are two LED lamps corresponding to two wavelengths of light, which can be used to measure solutions of two solutes. The LED lamps can be replaced as needed to detect solutions of corresponding solutes.

The measuring equipment includes:

The device described;

A host computer, which is connected to the MCU respectively, and the MCU displays the calculated results. In a specific implementation, the host computer can be a computer or a display screen;

The sample solution M was purified water.

The transmission reference method comprises the following steps:

First, the cuvette 4 is cleaned, wherein the washing liquid after cleaning is discharged from the liquid inlet and outlet 21; then, pure water is injected into the cuvette 4 from the liquid inlet and outlet 21;

The MCU controls the LED light to send a signal according to a predetermined program. After penetrating the pure water in the cuvette 4, the signal is received by the light receiving unit 10. The light receiving unit 10 receives the photometric value T1 of the light blocked by the cuvette 4 and feeds it back to the MCU. The MCU records the reference concentration of the pure water.

When measuring the measured liquid N, the cuvette 4 is cleaned and then the measured liquid N is injected into the cuvette 4; in this step, the measured liquid N can also be injected into the cuvette 4 as its raw material liquid, and then the MCU controls the resistance wire 41 to be energized and heated to a predetermined temperature according to a preset program. In a specific implementation, the heating time of the resistance wire 41 can be preset to control the heating temperature;

The MCU controls the LED light to send a signal according to a predetermined program. After penetrating the measured liquid N in the cuvette 4, the signal is received by the light receiving unit 10. The light receiving unit 10 receives the photometric value T2 of the light blocked by the cuvette 4 and feeds it back to the MCU. The MCU records the preliminary concentration of the measured liquid N.

Clean the cuvette 4 and then inject pure water into the cuvette 4;

The MCU controls the LED lamp to send a signal according to a predetermined program. After penetrating the pure water in the cuvette 4, the signal is received by the light receiving unit 10. The light receiving unit 10 receives the photometric value T3 of the light blocked by the cuvette 4 and feeds it back to the MCU. The MCU records the reference concentration of the pure water. The reference concentration takes into account the light decay of the LED lamp and the error caused by the degree of contamination of the cuvette 4 and the displacement change during the two pure water measurements, thereby improving the measurement accuracy.

MCU substitutes T1, T2, and T3 into the absorbance formula A=-lgT, where T is the transmittance, and calculates the corresponding absorbances A1, A2, and A3;

Then substitute A1, A2, and A3 into the Lambert-Beer law expression: A=abc; where a is the absorption coefficient, in units of L/(g·cm); b is the cuvette thickness, in units of cm; c is the solution concentration; and A is the absorbance. Calculate the corresponding concentrations c1, c2, and c3, in units of g/L.

Then calculate the error value = c1/c3; finally calculate, the final concentration value of the measured solution N = c2*error value. Or directly calculate according to: c1/c3 = final concentration value of the measured solution N/c2.

Finally, the MCU sends the result to the host computer for display.

In a specific implementation, the circuit diagram is shown in FIG9 , and the specific signal processing and transmission principle between the device, MCU, and host computer is as follows:

The voltage signal processed by the light receiving unit 10 is collected by the MCU and converted into a digital signal;

MCU reads data, performs algorithm filtering and formula calculations;

Finally, a high-precision display value is obtained;

The calculated value is converted into a digital signal by the MCU and transmitted to the host computer via the modbus-RTU protocol using a 485 signal.

Although the specific implementation modes of the present invention are described above, those skilled in the art should understand that the specific implementation modes described are only illustrative and are not intended to limit the scope of the present invention. Equivalent modifications and changes made by those skilled in the art in accordance with the spirit of the present invention should be included in the scope of protection of the claims of the present invention.

Claims (6)

1. A device for measuring water quality by spectrophotometry, characterized in that it comprises: A shell, wherein the upper and lower ends of the shell are open; A lower fixing plate, the lower fixing plate is provided with a liquid inlet and outlet; the lower fixing plate is fixedly connected to the lower end of the shell; A cuvette, wherein the upper and lower ends of the cuvette are open; the cuvette is placed in the housing; The first high-pressure valve; the bottom open end of the cuvette is airtightly embedded in the first high-pressure valve and communicates with the first high-pressure valve; a sealing ring is provided at the connection between the lower open end of the cuvette and the first high-pressure valve; the first high-pressure valve is also fixedly connected to the housing; the liquid inlet and outlet of the first high-pressure valve are communicated with the external flow pipeline of the housing; The bottom end of the cuvette is open and airtightly embedded between the first high-pressure valve and the second high-pressure valve, and is in communication with the first high-pressure valve and the second high-pressure valve; A second high-pressure valve, the top opening of the cuvette is airtightly embedded under the second high-pressure valve and communicates with the second high-pressure valve; a sealing ring is also provided at the connection between the upper opening of the cuvette and the second high-pressure valve; the second high-pressure valve is also fixedly connected to the housing; the second inlet and outlet of the second high-pressure valve are communicated with the external space of the housing; An upper fixing plate, wherein the upper fixing plate is provided with vertical screw holes; the upper fixing plate is fixedly connected to the top opening of the shell; A clamping bolt, which is locked into the screw hole and supports the top end of the second high-pressure valve; A spring, wherein the spring is sleeved on the clamping bolt, and the upper end of the spring abuts against the upper fixing plate, and the lower end of the spring abuts against the second high-pressure valve; A light emitting unit, the light emitting unit is detachably connected to the left side of the housing, and emits light in a direction toward the cuvette; A light receiving unit, the light receiving unit is detachably connected to the right side surface of the housing and is arranged facing the light emitting unit; Wherein, the direction of the light path is: the light emitted by the light emitting unit penetrates the cuvette and is then received by the light receiving unit. 2. A device for measuring water quality by spectrophotometry according to claim 1, characterized in that: it also includes a left lamp holder, a first through hole is provided on the left side surface of the housing; the left lamp holder is fixedly connected to the housing and embedded in the first through hole; An emitting PCB board, the light-emitting unit is connected to the emitting PCB board; the emitting PCB board is also fixedly connected to the left lamp holder. 3. A device for measuring water quality by spectrophotometry according to claim 2, characterized in that: it also includes a right lamp holder, a second through hole is provided on the right side surface of the housing; the right lamp holder is fixedly connected to the housing and embedded in the second through hole; Receiving PCB board; the light receiving unit is connected to the receiving PCB board; the receiving PCB board is fixedly connected to the right lamp holder. 4. The device for measuring water quality by spectrophotometry according to claim 3, characterized in that a resistance wire is wound around the outside of the cuvette. 5. The device for measuring water quality by spectrophotometry according to claim 4, characterized in that it also includes an MCU, and the MCU is respectively connected to the transmitting PCB board, the receiving PCB board and the resistance wire. 6. A transmission reference method for measuring water quality by spectrophotometry using the device according to any one of claims 1 to 5, characterized in that it includes a reference value measurement process, a sample measurement process, and an error value measurement and compensation process: (1) The benchmark measurement process includes the following steps: Step S11, first clean the cuvette, and then inject the sample solution M into the cuvette; Step S12, the light emitting unit emits light to illuminate the cuvette, the light penetrates the sample solution M in the cuvette, and then is received by the light receiving unit to obtain a transmittance T1; Step S13, calculating the reference concentration of the sample solution M according to the data received by the light receiving unit; (2) The measurement process of the sample to be measured includes the following steps: Step S21, first clean the cuvette, and then inject the test solution N into the cuvette; Step S22, the light emitting unit emits light to illuminate the cuvette, the light penetrates the solution N in the cuvette, and then is received by the light receiving unit to obtain a transmittance T2; Step S23, calculating the preliminary concentration of the solution N to be tested according to the data received by the light receiving unit; (3) The error value measurement and compensation process includes the following steps: Step S31, first clean the cuvette, and then inject the sample solution M into the cuvette; Step S32, the light emitting unit emits light to illuminate the cuvette, the light penetrates the sample solution M in the cuvette, and then is received by the light receiving unit to obtain a transmittance T3; Step S33, calculating the reference concentration of the sample solution M according to the data received by the light receiving unit; Step S34, comparing the reference concentration of the sample solution M with the benchmark concentration to obtain an error value, where the error value = reference concentration of the sample solution M / benchmark concentration; Step S35, compensating the error value to the preliminary concentration of the solution N to be tested, and obtaining the final concentration value of the solution N to be tested, where the final concentration value of the solution N to be tested = preliminary concentration of the solution N to be tested * error value.