Concentration measurement device and method

Abstract

The invention provides a concentration measuring device and a concentration measuring method. Even if the liquid temperature is unknown, the concentration can be measured by using the measured absorbance of pure water. An estimation circuit (103) estimates an estimated value of the liquid temperature on the basis of the absorbance of the pure water measured by the spectrophotometer (102) using a liquid temperature estimation regression formula indicating the correlation between the absorbance of the pure water at a predetermined measurement wavelength and the liquid temperature of the pure water at the time of measurement of the absorbance of the pure water. A concentration calculation circuit (104) determines the concentration of a component in the solution from the absorbance of the solution measured by the spectrophotometer (102) using a concentration regression formula corrected by the estimation value estimated by the estimation circuit (103). The concentration calculation circuit (104) corrects the constant term of the concentration regression formula by using the estimated value estimated by the estimation circuit (103), and determines the component concentration using the concentration regression formula in which the constant term has been corrected.

Description

Technical Field

[0001] The invention relates to a concentration measuring device and method. Background Art

[0002] There is a known technology for measuring the concentration of chemical solutions such as semiconductor cleaning solutions by using light absorption (Patent Document 1). The measurement technology uses the transmitted light intensity (spectrum) of pure water near room temperature as a reference, and measures the concentration of the chemical solution according to the change in light intensity (absorbance) of the measured chemical solution relative to the spectrum reference. It is not easy to measure the transmitted light intensity of pure water at any time at the production site. The concentration measurement at the production site is implemented by a concentration measuring device installed in a container containing the chemical solution. Therefore, the measurement of the transmitted light intensity (reference spectrum) of pure water as a reference is implemented by discharging the chemical solution contained in the container, cleaning the container, and then containing pure water in the container. In this way, in order to obtain the reference spectrum, it is necessary to stop production and other complicated operations.

[0003] On the other hand, if the same reference spectrum is always used in the absorbance measurement, accurate measurement cannot be performed due to the time-dependent change of the light source in the concentration measuring device or the deviation of the installation position of the concentration measuring device. Therefore, usually, the reference spectrum is re-acquired regularly (for example, once every two or three years), and in the measurement of the concentration of the drug solution during production, the absorbance measurement of the reference spectrum that has been regularly measured and updated is used to perform the measurement of the drug solution concentration.

[0004] [Prior art literature]

[0005] [Patent Document]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2005-331386 Summary of the invention

[0007] [Problems to be solved by the invention]

[0008] In the concentration measurement using light absorption (absorbance), it is necessary to obtain the liquid temperature at the time of the reference spectrum, but in the liquid container provided with the concentration measurement device, the liquid temperature is often not measured or controlled. Therefore, a method for performing concentration measurement by absorbance measurement using the measured transmitted light intensity of pure water is required even if the liquid temperature is unknown.

[0009] The present invention is made to solve the above-mentioned problems, and an object of the present invention is to estimate the liquid temperature from the measured absorbance of pure water and to perform concentration measurement by correcting the concentration regression formula even if the liquid temperature is unknown.

[0010] [Technical means to solve the problem]

[0011] The concentration measuring device of the present invention includes: a storage circuit, configured to store a concentration regression formula and a liquid temperature estimation regression formula, wherein the concentration regression formula calculates the concentration of a component in a solution based on the absorbance of the solution as a concentration measurement object, and the liquid temperature estimation regression formula represents the correlation between the absorbance of pure water and the liquid temperature of pure water when the absorbance of pure water is measured; an absorbance meter, which measures the absorbance of the solution and pure water respectively; an estimation circuit, configured to use the liquid temperature estimation regression formula, and estimate the estimated value of the liquid temperature based on the absorbance of pure water measured by the absorbance meter; and a concentration calculation circuit, configured to use the concentration regression formula corrected by the estimated value, and calculate the concentration of the component in the solution based on the absorbance of the solution measured by the absorbance meter.

[0012] In one structural example of the concentration measurement device, the concentration calculation circuit corrects the constant term of the concentration regression formula using the estimated value.

[0013] The concentration measurement method of the present invention includes: a first step of measuring the absorbance of pure water; a second step of using a liquid temperature estimation regression formula that represents the correlation between the measured absorbance of pure water and the liquid temperature of pure water when the absorbance of pure water is measured, and estimating an estimated value of the liquid temperature based on the absorbance measured in the first step; a third step of measuring the absorbance of a solution that is an object of concentration measurement; and a fourth step of using the estimated value to correct a concentration regression formula that calculates the concentration of a component in the solution based on the measured absorbance of the solution, and using the corrected concentration regression formula to calculate the concentration of the component in the solution based on the absorbance measured in the third step.

[0014] In one structural example of the concentration measurement method, in the fourth step, the constant term of the concentration regression formula is corrected using the estimated value.

[0015] [Effects of the Invention]

[0016] As described above, according to the present invention, even if the liquid temperature is unknown, the liquid temperature can be estimated from the measured absorbance of pure water, and the concentration can be measured using the estimated liquid temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural diagram showing the structure of a concentration measurement device according to an embodiment of the present invention.

[0018] Figure 2 It is a structural diagram showing a part of the structure of the concentration measuring device according to the embodiment of the present invention.

[0019] Figure 3 This is a flowchart illustrating a concentration measurement method according to an embodiment of the present invention.

[0020] Figure 4This is a characteristic diagram showing the correlation between the absorbance of pure water and the liquid temperature.

[0021] [Explanation of Symbols]

[0022] 101: Storage Circuit

[0023] 102: Absorbance meter

[0024] 103: Estimation Circuit

[0025] 104: Concentration calculation circuit DETAILED DESCRIPTION

[0026] Below, refer to Figure 1 A concentration measuring device according to an embodiment of the present invention is described. The concentration measuring device includes a storage circuit 101 , an absorbance meter 102 , an estimation circuit 103 , and a concentration calculation circuit 104 .

[0027] The storage circuit 101 stores a concentration regression formula for calculating the concentration of a component in a solution based on the absorbance of the solution as a concentration measurement object, and a liquid temperature estimation regression formula for expressing the correlation between the absorbance of pure water and the liquid temperature of pure water when measuring the absorbance of pure water. The measurement wavelength in the measurement of absorbance can be appropriately set.

[0028] The absorbance meter 102 measures the absorbance of the solution and pure water respectively. Figure 2 As shown, the absorbance meter 102 includes a light source 121 , a spectrometer 122 , a light source control circuit 123 , a spectroscopic control circuit 124 , a light receiving control circuit 125 , and a controller 126 .

[0029] The light source 121 emits light having a measurement wavelength corresponding to a component (solute) of the solution to be measured. The spectrometer 122 performs spectroscopic analysis on the received light. The spectrometer 122 can be, for example, a grating type or a Fabry-Perot type. The light emitted from the light source 121 is received by the spectrometer 122 through the solution to be measured for the component concentration.

[0030] The light source control circuit 123 controls the lighting of the light source 121 according to the control from the controller 126. For example, the light source control circuit 123 controls the light source 121 to emit light of a predetermined wavelength band at a predetermined intensity.

[0031] The spectroscopic control circuit 124 controls the spectrometer 122 according to the control from the controller 126. For example, the spectroscopic control circuit 124 controls the voltage applied between two mirrors included in the Fabry-Perot spectrometer 122 to appropriately control the wavelength of light received by the light receiving element.

[0032] The light receiving control circuit 125 measures the intensity of the light after the spectroscope (transmitted light intensity) according to the control from the controller 126. For example, when the light receiving control circuit 125 receives an electrical signal indicating the intensity of the light measured by the spectroscope 122, it converts the received electrical signal into a numerical value indicating the intensity of the light and outputs the converted numerical value.

[0033] The controller 126 controls the light source 121 and the spectrometer 122 , acquires the intensity of the transmitted light of the measurement wavelength obtained by the spectrometer 122 through the solution to be measured and calculates the absorbance.

[0034] For example, the controller 126 obtains the transmitted light intensity of the measurement wavelength corresponding to the measurement target component from the light that has passed through the solution as the measurement target. For example, when the measurement target components are ammonia and hydrogen peroxide, the controller 126 selects the measurement wavelength corresponding to ammonia and the measurement wavelength corresponding to hydrogen peroxide, and controls the light source control circuit 123 to light the light source 121, thereby emitting light of the wavelength band including the measurement wavelength.

[0035] In addition, the controller 126 controls the spectroscopic control circuit 124 to spectroscopically separate the light of the measurement wavelength from the light received by the spectrometer 122 via the solution as the measurement object. In addition, the controller 126 obtains the intensity of the light of the measurement wavelength (transmitted light intensity) measured by the spectrometer 122 via the light receiving control circuit 125. For example, after measuring the light intensity of the measurement wavelength corresponding to ammonia, the controller 126 measures the transmitted light intensity of the measurement wavelength corresponding to hydrogen peroxide. In addition, the controller 126 obtains the measured transmitted light intensity at each measurement wavelength to obtain the absorbance.

[0036] The controller 126 is a computer device including a central processing unit (CPU), a main storage device, an external storage device, etc. The CPU is operated (executed) by the program developed in the main storage device, thereby realizing the above-mentioned functions. The program is a program for causing the computer to execute the above-mentioned control functions. In addition, the controller 126 can also include a programmable logic device (PLD) such as a field-programmable gate array (FPGA).

[0037] The estimation circuit 103 uses a liquid temperature estimation regression formula that represents the correlation between the absorbance of pure water at a predetermined measurement wavelength and the liquid temperature of pure water when the absorbance of pure water is measured, and estimates the estimated value of the liquid temperature based on the absorbance of pure water measured by the absorbance meter 102. The concentration calculation circuit 104 uses a concentration regression formula that is corrected using the estimated value estimated by the estimation circuit 103, and calculates the concentration of the component in the solution based on the absorbance of the solution measured by the absorbance meter 102. The concentration calculation circuit 104 corrects the constant term of the concentration regression formula using the estimated value estimated by the estimation circuit 103, and calculates the component concentration using the concentration regression formula with the corrected constant term.

[0038] The estimation circuit 103 and the concentration calculation circuit 104 can be set as a computer device including a CPU, a main storage device, an external storage device, etc. The functions are realized by running the CPU (executing the program) through the program expanded in the main storage device. The program is a program for causing the computer to execute the control functions. In addition, the estimation circuit 103 and the concentration calculation circuit 104 can also include a programmable logic device (PLD) such as a field-programmable gate array (FPGA).

[0039] Next, refer to Figure 3 A concentration measurement method according to an embodiment of the present invention will be described.

[0040] First, in the first step S101, the absorbance of pure water is measured by the absorbance meter 102. The measurement wavelength in the measurement of the absorbance of pure water can be set appropriately.

[0041] Next, in the second step S102, the estimation circuit 103 uses a liquid temperature estimation regression formula that represents the correlation between the measured absorbance of pure water and the liquid temperature of pure water when the absorbance of pure water is measured, and estimates the estimated value of the liquid temperature (liquid temperature estimated value) based on the absorbance measured in the first step S101.

[0042] Next, in the third step S103, the absorbance meter 102 measures the absorbance of the solution as the object of concentration measurement. The measurement wavelength in the measurement of the absorbance of the solution can be appropriately set. Next, in the fourth step S104, the concentration calculation circuit 104 uses the estimated value of the liquid temperature obtained in the second step S102 to correct the concentration regression formula for calculating the concentration of the component in the solution based on the measured absorbance of the solution, and uses the corrected concentration regression formula to calculate the concentration of the component in the solution based on the absorbance measured in the third step. In the fourth step S104, the constant term of the concentration regression formula is corrected using the estimated value of the liquid temperature estimated by the estimation circuit 103, and the concentration of the component is calculated using the concentration regression formula with the corrected constant term.

[0043] As described above, according to the embodiment, since the liquid temperature is estimated from the measured absorbance of pure water, even if the liquid temperature is unknown, the concentration can be measured by estimating the liquid temperature from the measured absorbance of pure water and correcting the concentration regression formula.

[0044] The following is a more detailed description. 3 ) and hydrogen peroxide (H 2 O 2 ) is described as an example. In the measurement, for example, wavelength 1, wavelength 2, and wavelength 3, which are different in wavelength, are used to measure the intensity of the transmitted light. In the following, for the sake of simplicity, the wavelength 1, wavelength 2, and wavelength 3 are described, but in the present invention, the measurement wavelength is not limited to three wavelengths.

[0045] The concentration regression formula for each concentration C can be obtained by using the absorbance A measured using wavelength 1. 1 , Absorbance A based on measurement using wavelength 2 2 , and the absorbance A based on the measurement using wavelength 3 3 , and the regression coefficient b 0 , regression coefficient b 1 , regression coefficient b 2 , regression coefficient b 3 , and let C = b 1 A 1 +b 2 A 2 +b 3 A 3 +b 0 Here, each absorbance is the light intensity I of the solution to be measured divided by the light intensity I of pure water. 0The value obtained by multiplying the common logarithm of the value by -1 can be used to calculate the concentration regression formula of the concentration C using the light intensity I of the solution and the light intensity I of pure water. 0 , and is expressed using the following formula (1).

[0046]

[0047] Furthermore, due to the time-dependent change of the light source used in the measurement of the transmitted light intensity, or the deviation of the installation position of the light source or the spectrometer, even if the same concentration measuring device is used, the measured transmitted light intensity I of pure water may vary. 0 Therefore, even if the concentration of the component in the solution to be measured is constant, there will be problems such as different measurement results due to different measurement periods. In order to solve this problem, it is necessary to regularly measure the transmitted light intensity I of pure water. 0 . The intensity of light transmitted through pure water is I 0 According to the temperature T during measurement 0 (℃), as shown in formula (2), the concentration C can be expressed as temperature T 0 function of °C.

[0048]

[0049] As mentioned above, in the concentration regression formula for calculating the concentration, the transmitted light intensity I of pure water is 0 According to the temperature T during measurement 0 Therefore, when the liquid temperature in the measurement of the transmission intensity of pure water is different between the initial measurement and the re-measurement, only the transmission intensity I of the pure water is re-measured. 0 And updated to the transmitted light intensity I' 0 In order to use the measured light intensity I' of pure water 0 To obtain the concentration C', as shown in Formula (3), a concentration regression formula is used in which a constant term β(T) that changes according to temperature is added.

[0050]

[0051] However, in the chemical solution container provided with the concentration measuring device, the liquid temperature is often not measured or controlled, so the constant term β(T) that changes according to the temperature may not be defined.

[0052] On the other hand, in the case of the absorbance of pure water and the liquid temperature, Figure 4 There is a correlation as shown. In addition, Figure 4 The values ​​shown in the graph are the measurement wavelengths, which are represented by λ1, λ2, and λ3. Based on the correlation between the absorbance of pure water at the measurement wavelength and the liquid temperature T of pure water when the absorbance of pure water is measured, as shown in the following formula (4), the regression coefficient B is used.0 , regression coefficient B 1 , regression coefficient B 2 , regression coefficient B 3 , from which a regression formula for estimating liquid temperature can be made.

[0053]

[0054] Formula (4) can use the absorbance A 1 , absorbance A 2 , and absorbance A 3 And let "T = B 1 A 1 +B 2 A 2 +B 3 A 3 +B 0 …(5)”. By using the absorbance A of pure water measured during the actual concentration measurement 1 , absorbance A 2 , and absorbance A 3 Substituting into formula (5), the actual temperature of pure water during measurement can be obtained as T = T 0 '℃. By using the liquid temperature thus obtained, the constant term β(T) is corrected to the constant term β(T 0 ') can be used to calculate the exact concentration C'.

[0055] As described above, according to the present invention, even if the liquid temperature is unknown, the concentration can be measured using the measured absorbance of pure water, wherein the liquid temperature is estimated by using a liquid temperature estimation regression formula that represents the absorbance of pure water and the correlation between the liquid temperature of pure water when the absorbance of pure water is measured, and estimating the liquid temperature based on the measured absorbance of pure water.

[0056] In addition, it is obvious that the present invention is not limited to the above-described embodiments, and many modifications and combinations can be implemented by those skilled in the art within the technical concept of the present invention.

Claims

1. A concentration measuring device, comprising: a storage circuit configured to store a concentration regression formula for calculating the concentration of a component in the solution based on the absorbance of the solution as a concentration measurement object, and a liquid temperature estimation regression formula for storing the concentration regression formula, the concentration regression formula for calculating the concentration of a component in the solution based on the absorbance of the solution as a concentration measurement object, and the liquid temperature estimation regression formula for expressing the correlation between the absorbance of pure water and the liquid temperature of pure water when the absorbance of pure water is measured; An absorbance meter is used to measure the absorbance of the solution and pure water respectively; an estimation circuit configured to estimate an estimated value of the liquid temperature based on the absorbance of the pure water measured by the absorbance meter using the liquid temperature estimation regression formula; as well as The concentration calculation circuit is configured to use the concentration regression formula corrected by the estimated value to obtain the concentration of the component in the solution from the absorbance of the solution measured by the absorbance meter.

2. The concentration measuring device according to claim 1, wherein: The concentration calculation circuit corrects the constant term of the concentration regression formula using the estimated value.

3. A concentration measurement method, comprising: The first step is to measure the absorbance of pure water; A second step is to use a liquid temperature estimation regression formula that represents the correlation between the measured absorbance of pure water and the liquid temperature of pure water when the absorbance of pure water is measured, and to estimate an estimated value of the liquid temperature based on the absorbance measured in the first step; The third step is to measure the absorbance of the solution to be measured; as well as In the fourth step, the estimated value is used to correct the concentration regression formula for calculating the concentration of the component in the solution based on the measured absorbance of the solution, and the corrected concentration regression formula is used to calculate the concentration of the component in the solution based on the absorbance measured in the third step.

4. The concentration measurement method according to claim 3, wherein: In the fourth step, the estimated value is used to correct the constant term of the concentration regression formula.

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