JP3893068B2 - Solution concentration meter and concentration measuring method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a solution concentration meter and a concentration measurement method.
[0002]
[Prior art]
One of the methods for measuring the concentration of a plurality of components (inclusions) contained in a solution (hereinafter simply referred to as a concentration measurement method) is to transmit light from a light source through a solution and a reference sample (for example, the atmosphere). The sample spectrum and the reference spectrum are obtained, the absorbance spectrum is obtained from these spectra, and the concentration of a plurality of components contained in the solution to be measured is obtained by processing this absorbance spectrum using a method such as multivariate analysis. There is a way to ask.
[0003]
FIG. 6 is a diagram showing an example of the overall configuration of a solution concentration meter 30 conventionally used. In FIG. 6 , 2 is a light source such as a halogen lamp, 3 is a line through which the solution S to be measured flows, 4 is a flow cell formed on the line 3, 5 is a spectroscopic means for splitting light transmitted through the flow cell 4, and 6 is spectroscopic. The detector of the linear sensor on the plane which detects the light quantity of the transmitted light, 7 is the arithmetic processing part which inputs and calculates the light quantity detected by the detector 6, and 8 is a display part which displays a calculation result. .
[0004]
Therefore, the solution concentration meter 30 irradiates the measurement target solution S flowing in the line 3 with light, and the detector 6 detects the spectral spectrum (the light amount for each wavelength) of the transmitted light of the solution S. Next, the arithmetic processing unit 7 compares the spectral spectrum detected by the detector 6 with the spectral spectrum when transmitted through a comparative sample such as air, and calculates the absorbance spectrum due to the solution S from the amount of change, It is possible to obtain the concentration of the component contained in the solution S using this absorbance spectrum.
[0005]
However, when a chemical solution or the like is used as the measurement target solution S and the absorbance spectrum thereof is measured, if bubbles are included, excessive transmission or scattering of light occurs in the detector output signal due to the bubbles. In some cases, the absorbance spectrum was different from the target solution. As a result, an error may be included in the concentration value obtained by calculating the component concentration of the inclusion in the solution.
[0006]
[Problems to be solved by the invention]
However, in the conventional solution concentration meter described above, a large bubble removing device is used for removing bubbles, leading to an increase in manufacturing cost and the like. Furthermore, there is also a problem that the effect is small with respect to a solution (hereinafter, referred to as a solution S) such as a mixed solution of ammonia water, hydrogen peroxide solution, and water that foams due to a temperature change or the like.
[0007]
In view of this, the present applicant already disclosed in Japanese Patent Application Laid-Open No. 9-203706, when the total concentration of the components contained in the solution S is outside a predetermined range with respect to 100%, Has proposed a concentration analysis method characterized in that it is considered to be contaminated. As a result, the bubble can be determined more effectively, and the solution concentration can be measured more accurately.
[0008]
However, even if the concentration analysis method proposed in the above-mentioned patent is carried out, as shown in FIG. 7 , if the influence of bubbles mixed in the solution S is small, this may not be detected. That is, in the chemical solution that is the measurement target solution S, when the concentration of one component increases due to the influence of bubbles, the concentration of another component decreases, and the total becomes almost 100% as a whole. In some cases, such errors cannot be detected completely.
[0009]
In addition, the cause of abnormal values is not limited to bubbles, but other noises such as electromagnetic waves may suddenly cause abnormal measurement values. An abnormal value could not be determined.
[0010]
Further, as another method for attenuating abnormal values caused by bubbles, it is conceivable to perform a moving average process by accumulating some calculation results. However, there is a problem that even if the peak of the abnormal value can be suppressed by this, the effect remains. Furthermore, there is a problem that the longer the moving average process is, the worse the response becomes.
[0011]
The present invention has been made in consideration of such a situation, and even if bubbles in the solution to be measured are included, the influence of errors due to bubbles and other noises can be removed as reliably as possible. An object of the present invention is to provide a solution concentration meter and a concentration measurement method.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the solution concentration meter of the present invention comprises a light source for irradiating light to a solution to be measured, a detector for detecting a spectral spectrum of light transmitted through the solution, a detected spectrum and a comparative sample. In the solution concentration meter having an arithmetic processing unit that calculates the absorbance or light amount spectrum of the solution from the spectrum of the transmitted light and obtains the concentration of the component contained in the solution using the spectrum , the arithmetic processing unit is calculated this time. It was calculated the difference between the spectrum and the spectrum previously calculated, by comparing the average or variance of the absolute value of the difference with a predetermined threshold, to determine whether the spectrum that has been calculated this time is affected by bubbles Exclude the spectrum determined to be affected by bubbles and exclude the spectrum determined to be unaffected by bubbles. It is characterized by having a bubble effect removal function of calculating a degree.
[0013]
[0014]
[0015]
That is, in the present invention, the distortion of the absorbance or light amount spectrum caused by the bubbles is detected by taking the difference from the previous absorbance or light amount spectrum. Here, since the component concentration of the solution to be measured does not change abruptly in a short time, the average or dispersion of absolute values in the wavelength direction of the difference spectrum is due to noise such as bubbles, the size of which is It represents the magnitude of noise such as bubbles. Therefore, the solution concentration meter of the present invention is not affected by bubbles by removing the spectrum determined to be affected by bubbles and other noises (for example, thunder noise) from the component concentration calculation very easily and accurately. The concentration of the solution can be calculated using the determined spectrum . This can easily improve the accuracy of the solution concentration meter. Further, since it is possible to determine whether or not the calculated spectrum is affected by bubbles (or noise) at the moment when the amount of light is detected, high-speed response can be obtained.
[0016]
[0017]
[0018]
Furthermore, in the present invention, since the bubble effect removal function can be realized by a program that can be executed by the arithmetic processing unit, no special configuration is required for hardware, and the manufacturing cost can be reduced. Incidentally, the spectrum used for determination of the bubble effect, be used as it is output from the detector may be used that converts the output of the detector to the absorbance spectrum.
[0019]
[0020]
[0021]
[0022]
The concentration measurement method of the present invention detects a spectral spectrum of light transmitted through the measurement target solution in a state where the measurement target solution is irradiated with light, and detects the detected spectral spectrum and the spectral spectrum of light transmitted through the comparative sample. Calculate the absorbance or light intensity spectrum by the solution, calculate the difference between this calculated spectrum and the previously calculated spectrum , and compare the average or variance of the absolute value of this difference with a predetermined threshold value. spectrum to determine whether under the influence of air bubbles, spectrum is determined that the influence of bubbles by using the spectrum is determined not affected by air bubbles are excluded, the concentration of the solution It is characterized by calculating.
[0023]
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the solution concentration meter and the concentration measuring method of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing an overall configuration of a solution concentration meter 1 of the present invention. Since the hardware configuration shown in FIG. 1 is basically the same as that of FIG. 6 described in the conventional example, the same reference numerals are used to avoid redundant description.
[0025]
In FIG. 1, 9 is a storage unit such as a semiconductor memory that can be read and written by an arithmetic processing unit 7 (hereinafter referred to as CPU), 10 is an interface according to a predetermined standard such as EIA232 connected to the host computer 11, and the like. Is a D / A converter that converts the measured density value into an analog signal and outputs it, and 13 is a contact output section for various alarm signals that are output based on the measured density value and whether this contact output is necessary. A parallel input / output unit 14 having an input unit for inputting is an alarm buzzer.
[0026]
15 is a defoaming tank provided on the upstream side of the cell 4 in the line 3, and this defoaming tank 15 is formed from a sealed container 16 having an appropriate capacity according to characteristics such as a flow rate and viscosity of the solution S to be measured. Become. This detailed configuration is disclosed in Japanese Patent No. 3031834. Reference numeral 22 denotes a flow path throttle valve formed in the line 3 on the downstream side of the cell 4.
[0027]
The light source 2 is, for example, a halogen lamp, but the present invention does not limit the type of light source. That is, any light source can be used as long as it can strongly emit light having a wavelength absorbed by the measurement target component of the measurement target solution S. Moreover, although the cell 4 of this example shows the example which is a flow cell, what can accommodate the measuring object solution S and permeate | transmit the light from the light source 2 should just be used. Further, the spectroscope 5 is desirably a slit and a diffraction grating, but may be a diffraction lens.
[0028]
In this example, the detector 6 is a planar linear sensor that detects the amount of transmitted light spectrally separated by the spectroscope 5. That is, the amount of light of each wavelength separated by the spectroscope 5 for each wavelength can be detected continuously and at once by the detection elements in each part of the detector 6 and output as data divided into a plurality of channels. it can. However, the detector 6 may include a plurality of detectors that separately measure the amount of transmitted light for each wavelength.
[0029]
The system configuration shown in FIG. 1 does not limit the present invention. For example, the storage unit 9 described as a separate body from the CPU 7 may be built in the CPU 7. Similarly, the interface 10, the D / A converter 12, and the parallel input / output unit 13 may be built in the CPU 7.
[0030]
In this example, the solution concentration meter 1 can be used as an inline monitor by providing the display unit 8. However, the present invention does not limit that the solution concentration meter 1 has the display unit 8. That is, various output methods such as transmission of density data, storage and storage, and recording on recording paper can be considered for density output.
[0031]
The contents stored in the storage unit 9 include, for example, a concentration measurement program P for instructing the operation of the solution concentration meter 1, spectrum data Sp used as temporary storage by the concentration measurement program P, and integration of spectrum data Integrated data St (λ) used in the above, an average value Sa (λ) of spectrum data within a predetermined time, density data C ₁ calculated using this average value Sa (λ), and predetermined density data C ₁ These are the moving average data C ₂ within the time and the alarm setting data Ca for storing the alarm value of the concentration of each component.
[0032]
The host computer 11 is not limited to a single computer, and may be connected to a plurality of computers via a network. It goes without saying that various communication protocols can be selected.
[0033]
In addition, the solution concentration meter 1 shown in this example uses the defoaming tank 15, so that the measurement target solution S of the bubble wrap introduced into the sealed container 16 has only bubbles rising in the sealed container 16. The gas is separated into the phase G and the liquid phase, and the bubbles in the measurement target solution S are removed. As a result, the sample liquid at the bottom of the container in which almost no bubbles are mixed can be introduced into the flow cell 4.
[0034]
In the case of this example, it is possible to suppress foaming of the measurement target solution S in the cell 4 by constricting the flow path throttle valve 22 on the downstream side of the cell 4 and pressurizing the inside of the cell 4, The present invention does not limit this configuration.
[0035]
FIG. 2 is a diagram illustrating an example of the operation of the concentration measurement program P stored in the storage unit 9. Hereinafter, an example of the concentration measuring method of the present invention will be described with reference to FIGS.
[0036]
S1 is a step of calculating an absorbance spectrum by reading a light amount spectrum for each wavelength of transmitted light using the detector 6. Here, assuming that the light amount spectrum detected by the detector 6 is I (λ) and the light amount spectrum transmitted through the air is I 0 (λ), the calculation shown in the following equation (1) is performed, and the absorbance is obtained. A spectrum A (λ) is calculated.
A (λ) = log ₁₀ {I ₀ (λ) / I (λ)} Expression (1)
However, (lambda) has shown the wavelength.
[0037]
S2 is a step of calculating a difference spectrum by subtracting the absorbance spectrum data Sp detected and calculated last time from the absorbance spectrum A (λ) detected and calculated this time. That is, since the absorbance spectrum that has changed within a short minute from the previous light amount reading to the current light amount reading becomes a difference spectrum, the difference spectrum obtained here (that is, the difference in the shape of both spectra) is very small. Expected to be value. In particular, when the minute time is sufficiently short with respect to the flow rate of the solution S to be measured, the value appearing in the difference spectrum represents the size of a variable factor such as a bubble or other noise.
[0038]
S3 is a step of performing bubble determination using the difference spectrum obtained in step S2. That is, for example, the dispersion in the wavelength direction of the difference spectrum is obtained. Since this dispersion indicates how much bubbles and other noise influences are included in the absorbance spectrum detected and calculated this time, bubble determination can be performed based on the size of the dispersion. In the bubble determination in step S3, an average of absolute values of the difference spectrum may be obtained instead of the variance of the difference spectrum.
[0039]
If it is determined in step S3 that the value is within the allowable range (OK), the process proceeds to step S4. If it is determined that the value is outside the allowable range (NG), the process jumps to step S5.
[0040]
The permissible range may be set for each wavelength λ, and weighting based on the set value of the permissible range may be performed for each wavelength λ. In this case, it is possible to perform bubble determination in consideration of the influence of the bubbles on the concentration value for each wavelength, so that a more accurate concentration value can be obtained.
[0041]
S4 is a step of integrating the absorbance spectrum read this time into the integrated data St (λ). At the same time, the number of integration N ′ is counted.
[0042]
S5 is a step for determining whether or not the reading of the absorbance spectrum is completed. In this example, for example, 5 times are set. That is, the loop process formed by steps S1 to S4 is repeated five times, for example, so that the absorbance spectrum can be appropriately rounded. Needless to say, the present invention does not limit the number of loop processing iterations to five. Further, when the absorbance spectrum is not rounded, it is not necessary to perform a loop process.
[0043]
S6 is a process executed when the loop process of S1 to S5 is completed, and is a step of determining the number of times of integration N ′ with respect to the number of times of reading. In this example, if the number of readings is N, the determination r in step S6 is, for example, that the ratio r between the number of integrations N ′ and the number of readings N is within a range of 1/2 <r ≦ 1 (in this example, 3 as the optimum condition). / 4 ≦ r ≦ 1) is effective.
[0044]
S7 is a step for calculating density. The concentration calculation in step 7 is performed by, for example, dividing the integrated data St (λ) by the number of times of integration to obtain an average value Sa (λ) of the absorbance spectrum data, and further calculating the average value of the absorbance spectrum by a multivariate analysis method. The data is processed by a data processing method such as the above, and converted into each concentration data C ₁ of the measurement target component.
[0045]
S8 is a step of comparing the calculated density with the previously calculated density (such as moving average data C ₂ ), and obtains the deviation between the density C ₁ calculated this time and the currently displayed density C _2. When the difference exceeds a certain value (outside the predetermined range), it is determined that the concentration is suddenly changed. When the density changes gently (valid), the following step S9 is executed, and when it is determined that the density changes suddenly, the process jumps to step S12.
[0046]
S9 is a step of calculating the moving average data C ₂ using the measured value of the density data C ₁ within a predetermined time. Therefore, the moving average data C ₂ is rounded by using the obtained density measurement value C ₁ , so that the influence of noise is further reduced. It is desirable that this moving average time can be arbitrarily changed by a command from the host computer 11 or the like.
[0047]
On the other hand, if it is determined in step S6 that the number of integrations is small and the integration data St (λ) is invalid, the process of step S10 is executed.
In step S10, it is determined whether integration invalidation has occurred continuously for a predetermined number of times or more. If the integration invalidation is a single shot (that is, if the integration invalidation is less than the predetermined number), the process returns to step S1 and the light quantity reading process is performed again. If the integration invalidation continues even more than the predetermined number of times, the density The process proceeds to step S11 for calculating.
[0048]
Note that, in the process of step S10, when the integration invalidation has continuously occurred for a predetermined number of times or more, for example, an alarm is output using the buzzer 14 or the like, or an alarm display Da is performed using the display unit 8 or the like. In other words, if the integration invalidation continues continuously for a predetermined number of times or more, it is determined that some noise is mixed in or an abnormality such as an optical system or other failure, and this is output as an alarm and the concentration calculation step S11. Proceed to
[0049]
S12 is executed when it is determined in step S8 that the concentration has suddenly changed, and it is determined whether or not the concentration sudden change (that is, the concentration is invalid) continues. If it is determined that the invalidity of the density is single, the process returns to step S1 again to calculate the density. If it is determined that the invalidity of the density has continued for a predetermined number of times, the next step S13 is executed.
[0050]
That is, if the concentration suddenly changes continuously, the concentration value is not abnormal due to some unforeseen problem, but it is determined that the concentration has actually changed suddenly. Density value is set. That is, when the non-adopted density value occurs continuously up to a certain number of times, a moving average value (density) is calculated from the density value obtained at the last time. This makes it possible to accurately display the concentration that suddenly changes due to the exchange of chemicals.
[0051]
S13. A step of outputting as the concentration displayed Dc in the display unit 8, for example using a moving average data C ₂ calculated by the processing of step S1 to S12. The density output in the process of step S13 may include density value data output and recording in addition to the density display by the display unit 8. Moreover, outputting the alarm display Da and lighting the alarm lamp La by comparing the obtained density value with an appropriate value set in the alarm setting data Ca may be included.
[0052]
When the series of processes in steps S1 to S13 is completed, the process of jumping to step S1 once again and repeating the above process allows the concentration display Dc of each component of the measurement target solution S flowing on the line 3 to be continuously performed. The solution concentration meter 1 functions as an in-line concentration monitor that continuously outputs concentration values.
[0053]
When the measurement time and the density value are recorded on various recording media as the density output, it is possible to record all the calculated density values regardless of the determination in step S12.
[0054]
In the concentration measuring method described in detail above, the absorbance spectrum A detected and calculated by the detector in the processing shown in steps S1 to S5 is integrated, and the moving average of the concentration values is performed in the processing shown in steps S6 to S12. Therefore, the absorbance spectrum affected by bubbles and other noises can be easily and reliably removed from the concentration calculation on the software. Therefore, it is possible to provide a solution concentration meter that can measure the solution concentration without being affected by bubbles and noise without changing the hardware configuration, and can perform more accurate concentration measurement with almost no increase in manufacturing cost. .
[0055]
In addition, by accurately determining and discarding abnormal data including bubbles and other noises, it is possible to obtain a more accurate measurement value compared to simple integration and moving average processing. Furthermore, as shown in steps S3 to S5 described above, the determination of abnormal data is performed every time the light amount data is input from the detector 6, so that the responsiveness is very good and the abnormal data is eliminated. High-speed response is possible.
[0056]
3 to 5 are diagrams showing measured values measured in order to confirm the effect obtained by the present invention. FIG. 3 shows a bubble using a mixed solution (ammonia / hydrogen peroxide solution) in which bubbles are easily generated. An output example in the case where the concentration value of each component (NH ₃ , H ₂ O ₂ ) is output without eliminating abnormal data due to the above is shown. FIG. 4 shows an output example when the defoaming tank 15 and the flow restrictor 22 are provided in the line 3 to suppress the generation of bubbles and output the concentration value of the same component without eliminating abnormal data. ing. FIG. 5 shows an output example when the defoaming tank 15 and the flow path throttle valve 22 are provided in the line 3 and the concentration measurement program P for eliminating abnormal data is executed. In either case, the horizontal axis represents time, and the vertical axis represents concentration.
[0057]
As is apparent from a comparison of FIGS. 3 to 5, in the concentration meter 1 of the present invention, the influence of various noises as well as noise caused by bubbles can be almost completely eliminated by the concentration measurement program P that realizes the concentration measurement method. And accurate measurement values can be output.
[0058]
Further, particularly in the case of this example, by providing a defoaming tank 15 having a simple configuration upstream of the cell 4 on the line 3, bubbles are removed from the measurement target solution S flowing in the cell 4, and downstream of the cell 4. Since the flow restrictor 22 is provided on the side to prevent foaming in the cell 4, the influence of bubbles included in the spectrum of the transmitted light amount detected by the detector 6 is reduced. Therefore, the spectrum discarded by the concentration measurement program P can be reduced, and a more accurate measurement result can be obtained.
[0059]
In the case of this example, it is sufficient for the pressure adjusting means such as the defoaming tank 15 and the flow path throttle valve 22 to reduce the amount of bubbles in the cell 4, so that the bubbles are almost completely removed as in the prior art. Therefore, a large-scale defoaming device or a high-pressure pump is not required, and a high-precision solution concentration meter that is small in size and reduced in manufacturing cost can be provided. In addition, this invention does not limit the structure of the defoaming tank 15, It is possible to use the defoaming tank 15 of various shapes. Similarly, it goes without saying that the present invention is not limited to the provision of the flow restrictor 22. Furthermore, it is not necessary to provide the defoaming tank 15 or the flow restrictor 22.
[0060]
[0061]
[0062]
[0063]
[0064]
[0065]
[0066]
[0067]
[0068]
[0070]
[0071]
[0072]
[0073]
[0074]
In the example described above, an example in which the concentration of a plurality of components contained in a solution is detected is shown, but the present invention can also detect the concentration of a single component.
[0075]
Further, in each example described in detail above, the number of abnormal data discarded by the concentration measurement program P is reduced by removing bubbles to some extent from the solution to be measured by interposing the deaeration tank 15 in the line 3. Thus, the accuracy of the concentration measurement value and the response are improved, but the present invention does not limit this point.
[0076]
【The invention's effect】
As described above, according to the solution concentration meter and the concentration measurement method of the present invention, even when bubbles are included in the sample liquid used for measurement, the solution concentration can be adjusted without being affected by bubbles or other noise. It can be measured accurately. In particular, since abnormal data generated due to bubble contamination can be accurately identified by normal data and software processing, it is possible to reliably eliminate the influence of bubbles while reducing the manufacturing cost.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a preferred embodiment of a solution concentration meter according to the present invention.
FIG. 2 is a diagram for explaining an example of a concentration measuring method in the solution concentration meter.
FIG. 3 is a diagram showing a measurement result for comparison for verifying the effect of the present invention.
FIG. 4 is a diagram showing another comparison measurement result.
FIG. 5 is a diagram showing measurement results for verifying the effects of the present invention.
FIG. 6 is a configuration explanatory view showing a conventional example.
FIG. 7 is a diagram illustrating a problem of a conventional example.
[Explanation of symbols]
1 ... The solution densitometer, 2 ... light source, 6 ... detector, 7 ... arithmetic processing unit, a concentration of C ₁ ... solution, C ₂ ... moving average data, S ... test liquid, St ... integrated value of the spectrum, Sp ... Spectrum, Sa ... average spectrum.

Claims (2)

The light source that irradiates light to the solution to be measured, the detector that detects the spectral spectrum of the light that has passed through this solution, and the absorbance or light intensity spectrum of the solution is calculated from the detected spectrum and the spectrum of the light that has passed through the comparative sample. In the solution concentration meter having an arithmetic processing unit for obtaining the concentration of the component contained in the solution using this spectrum , the arithmetic processing unit calculates a difference between the spectrum calculated this time and the spectrum calculated last time, By comparing the average or variance of the difference with a predetermined threshold, it is determined whether the calculated spectrum is affected by bubbles, and the spectrum determined to be affected by bubbles is excluded. It has a bubble effect removal function that calculates the concentration of the solution using a spectrum determined not to be affected by bubbles. Solution concentration meter to be. Detects the spectrum of the light that has passed through the solution to be measured while irradiating the solution to be measured, and calculates the absorbance or light intensity spectrum of the solution from the detected spectrum and the spectrum of the light that has passed through the comparative sample. and, calculating a difference between the calculated spectrum and spectrum previously calculated, by comparing the average or variance of the absolute value of the difference with a predetermined threshold, the spectrum that has been calculated this time is affected by the bubbles A concentration determined by calculating whether the concentration of the solution is calculated using a spectrum determined not to be affected by bubbles, excluding the spectrum determined to be affected by bubbles. Measuring method.

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