Water quality analyzer

Abstract

To fulfill the need to correct increases or decreases in a detection signal due to staining.SOLUTION: Provided is a water quality analyzer for measuring a concentration of a measuring object substance contained in sample water, and the water quality analyzer comprises: a flow cell which has a wall part transmitting light and an internal space surrounded by the wall part and allows the sample water to pass through the internal space; a light source which emits light toward the flow cell; a concentration measuring part which, on the basis of light to be measured from the flow cell when emitting light source light from the light source to the flow cell, measures the concentration of the measuring object substance contained in the sample water, in the state of flowing the sample water to the flow cell; a stain detection part which, on the basis of a light quantity of the light to be measured from the flow cell, measures an optical attenuation due to stain of the flow cell in the state of flowing to the flow cell reference water with a known concentration of the measuring object substance; and a stain correction part which, on the basis of the optical attenuation due to the stain of the flow cell, corrects a measurement result of the concentration of the measuring object substance when flowing the sample water.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a water quality analyzer. [Background technology]

[0002] 2. Description of the Related Art Conventionally, water quality analyzers that analyze the quality of sample water are known (see, for example, Patent Documents 1 and 2). [Prior art document] [Patent documents] [Patent Document 1] Patent No. 6436266 [Patent Document 2] JP 2007-46978 A Summary of the Invention [Problem to be solved by the invention]

[0003] When dirt accumulates in the parts of a water quality analyzer through which sample water flows, the detection signal that indicates the concentration of a substance to be measured that is contained in the sample water fluctuates. [Means for solving the problem]

[0004] In a first aspect of the present invention, there is provided a water quality analysis device. The water quality analysis device may include a flow cell. Any of the above water quality analysis devices may include a light source. Any of the above water quality analysis devices may include a concentration measurement unit. Any of the above water quality analysis devices may include a dirt detection unit. Any of the above water quality analysis devices may include a dirt correction unit. In any of the above water quality analysis devices, the flow cell may have a wall portion that transmits light. In any of the above water quality analysis devices, the flow cell may be surrounded by the wall portion and have an internal space through which the sample water passes. In any of the above water quality analysis devices, the light source may irradiate light toward the flow cell. In any of the above water quality analysis devices, the concentration measurement unit may measure the concentration of a measurement target substance contained in the sample water based on the measured light from the flow cell when the light source irradiates the flow cell with light source light from the light source while the sample water is flowing through the flow cell. In any of the above water quality analysis devices, the dirt detection unit may detect the amount of light attenuation due to dirt on the flow cell based on the amount of measured light from the flow cell while reference water having a known concentration of the measurement target substance is flowing through the flow cell. In any of the water quality analyzers described above, the contamination correction section may correct the measurement result of the concentration of the measurement target substance when the sample water is allowed to flow, based on the amount of light attenuation caused by contamination of the flow cell.

[0005] In any of the above water quality analysis devices, the contamination correction unit may store the detected amount of light attenuation due to contamination of the flow cell, and correct the measurement result of the concentration of the substance to be measured using the stored amount of light attenuation until the next detection of the amount of light attenuation due to contamination of the flow cell.

[0006] Any of the above water quality analysis devices may further include a cleaning unit. In any of the above water quality analysis devices, the dirt detection unit may detect the amount of light attenuation by flowing reference water through the flow cell after cleaning the flow cell and before flowing the sample water.

[0007] Any of the water quality analysis devices described above may further include a light source light quantity monitor. In any of the water quality analysis devices described above, the light source light quantity monitor may detect the quantity of light from the light source light incident on the flow cell. In any of the water quality analysis devices described above, the dirt detection unit may detect the amount of light attenuation using the light quantity of the light source light when measuring the reference water.

[0008] In any of the water quality analyzers described above, the contamination corrector may hold a history of attenuation information corresponding to the amount of optical attenuation measured in the past, and may predict the amount of optical attenuation in the future.

[0009] In any of the water quality analysis devices described above, the contamination corrector may estimate a time when the predicted value of the amount of optical attenuation will exceed an allowable value.

[0010] Any of the above water quality analysis devices may further include a cleaning unit. In any of the above water quality analysis devices, the dirt detection unit may detect the amount of optical attenuation by flowing reference water through the flow cell after cleaning the flow cell and before flowing the sample water. In any of the above water quality analysis devices, the cleaning unit may change the cleaning method depending on the prediction of the amount of optical attenuation.

[0011] In any of the water quality analyzers described above, the cleaning section may select a cleaning method for the next cleaning depending on a change in the amount of optical attenuation before and after cleaning when the cleaning method is changed.

[0012] In any of the above water quality analyzers, the dirt detection unit may detect the amount of light attenuation using reference water multiple times between cleanings and the next cleaning, and predict a change in the amount of light attenuation between cleanings based on a rate of increase in the amount of light attenuation.In any of the above water quality analyzers, the dirt correction unit may correct the measurement result of the concentration of the target substance based on the prediction of the change in the amount of light attenuation.

[0013] In any of the above water quality analysis devices, when detecting the amount of light attenuation between cleanings, the flow rate of the reference water may be set to be lower than the flow rate of the sample water when measuring the concentration of the substance to be measured contained in the sample water.

[0014] In any of the water quality analyzers described above, when detecting the amount of light attenuation between cleaning operations, the flow rate of the reference water may be set to be equal to or lower than the flow rate of the cleaning water flowed during cleaning.

[0015] In any of the above water quality analysis devices, the cleaning unit may determine whether or not cleaning of the flow cell has been completed based on the detection result of the amount of optical attenuation, and if cleaning of the flow cell is not completed within a set period from the start of cleaning, the cleaning method in the cleaning unit may be changed.

[0016] In any of the water quality analyzers described above, the cleaning section may select a cleaning method for the flow cell based on a history of sample water that has been flowed through the flow cell in the past.

[0017] Any of the above water quality analysis devices may further include a transmitted light detection unit and a scattered light amount detection unit. In any of the above water quality analysis devices, the transmitted light detection unit may detect a transmitted light amount, which is the amount of transmitted light that has passed through the flow cell. In any of the above water quality analysis devices, the scattered light amount detection unit may detect a scattered light amount, which is the amount of light scattered from the reference water. In any of the above water quality analysis devices, the dirt detection unit may detect an amount of light attenuation due to dirt on the flow cell based on the transmitted light amount and the scattered light amount when the reference water is flowing through the flow cell.

[0018] The above summary of the invention does not list all of the necessary features of the present invention. Also, subcombinations of these features may also be inventions. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a diagram showing an example of a water quality analysis device 100 according to an embodiment of the present invention. [Diagram 2] FIG. 13 is a diagram for explaining correction of the measurement result of the concentration of a substance to be measured. [Diagram 3] FIG. 1 is a diagram showing an example of a water quality analysis device 100 according to another embodiment of the present invention. [Figure 4] FIG. 1 is a diagram showing an example of a water quality analysis device 100 according to another embodiment of the present invention. [Diagram 5] 5 is a flowchart showing an example of the operation of the water quality analyzer 100 in the embodiment of FIG. 4. [Figure 6] FIG. 1 is a diagram showing an example of a water quality analysis device 100 according to another embodiment of the present invention. [Figure 7] FIG. 13 is a diagram showing prediction of future optical attenuation based on past optical attenuation. [Figure 8] FIG. 1 is a diagram showing an example of a water quality analysis device 100 according to another embodiment of the present invention. [Figure 9] 13 is a diagram showing another embodiment when predicting a future amount of optical attenuation based on a past amount of optical attenuation. FIG. [Figure 10] FIG. 1 is a diagram showing an example of a water quality analysis device 100 according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The present invention will be described below through embodiments of the invention, but the following embodiments do not limit the scope of the invention according to the claims. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0021] FIG. 1 is a diagram showing an example of a water quality analyzer 100 according to an embodiment of the present invention. The water quality analyzer 100 measures the concentration of a measurement target substance contained in a water sample. The water quality analyzer 100 of this example includes a light source 10, a flow cell 20, a concentration measurement unit 36, a transmitted light detection optical system 70, a transmitted light detection signal processing unit 72, a dirt detection unit 40, and a dirt correction unit 42. The concentration measurement unit 36 ​​includes a concentration detection optical system 30 and a concentration detection signal processing unit 32. The concentration detection optical system 30 and the transmitted light detection optical system 70 are devices that detect the amount of received light using a light receiving element such as a CCD or a photodiode. In this specification, the amount of light is the total amount (lm / S) of a light flux passing through a specified surface within a specified unit time, but the light intensity (cd) may also be used as the amount of light. The concentration detection optical system 30 and the transmitted light detection optical system 70 output an electric signal according to the detected amount of light. The concentration detection signal processing unit 32 and the transmitted light detection signal processing unit 72 perform signal processing such as amplification or noise removal on the electric signal.

[0022] The light source 10 irradiates light 91 toward the flow cell 20. The flow cell 20 has a wall 22 and an internal space 24. At least a part of the wall 22 is formed of a material that transmits at least a part of the components of the light 91 irradiated by the light source 10. At least a part of the wall 22 is formed of, for example, glass. The wall 22 may have a window through which the light 91 enters or exits, and a support that supports the window. In this specification, the window through which the light 91 enters or exits may be described as the wall 22. The internal space 24 is surrounded by the wall 22. The sample water passes through the internal space 24. As an example, the wall 22 has a cylindrical shape. FIG. 1 shows a schematic cross section of the wall 22 and the internal space 24.

[0023] The concentration detection optical system 30 detects measurement light 92 from the flow cell 20. The concentration detection optical system 30 measures the amount of light at at least one wavelength of the measurement light 92. The measurement light 92 is light emitted from the flow cell 20 when light 91 is irradiated from the light source 10 in a state where sample water is present in the flow cell 20. The measurement light 92 may include fluorescence emitted from the measurement target substance contained in the sample water when the measurement target substance is irradiated with the light 91. In this case, the concentration detection optical system 30 may measure the amount of measurement light 92 at a wavelength different from that of the light 91.

[0024] The concentration detection signal processing unit 32 calculates the concentration of the measurement target substance contained in the sample water based on the measurement result in the concentration detection optical system 30. The sample water is, for example, tap water, sewage water, seawater, wastewater from factories, etc., but is not limited to these. When the sample water contains fluorescent substances such as polycyclic aromatic hydrocarbons (hereinafter referred to as PAHs), fluorescence (measurement light 92) with a wavelength specific to the substance is generated when the sample water is irradiated with ultraviolet light 91. Since the fluorescence intensity is proportional to the concentration of the fluorescent substance contained therein, the concentration of the fluorescent substance, which is the measurement target substance, can be accurately measured by measuring the light amount of the measurement light 92 at the wavelength. The concentration detection signal processing unit 32 outputs the measurement result to the dirt correction unit 42.

[0025] When dirt occurs on the wall 22 of the flow cell 20, the dirt attenuates the intensity of the light 91 or the measurement light 92. When the wall 22 is provided with the window portion described above, the dirt on the wall 22 refers to dirt on the window portion. The dirt on the wall 22 is, for example, foreign matter attached to the inner or outer surface of the wall 22. When the intensity of the light 91 or the measurement light 92 attenuates, an error occurs in the measurement result of the concentration of the substance to be measured. For this reason, it is preferable to be able to correct the effect of dirt occurring on the wall 22 of the flow cell 20.

[0026] The dirt detection unit 40 detects dirt on the wall portion 22. The dirt detection unit 40 may detect dirt on the wall portion 22 using a predetermined operation in the water quality analysis device 100 as a trigger. The dirt detection unit 40 may detect dirt on the wall portion 22 every time a set detection period elapses. The dirt detection unit 40 may detect dirt on the wall portion 22 in response to an instruction from a user or the like.

[0027] When the dirt detection unit 40 detects dirt on the wall 22, the light source 10 irradiates the flow cell 20 with light 91 having a predetermined wavelength component. When the water quality analysis device 100 detects dirt on the wall 22, the water quality analysis device 100 may flow reference water having a known concentration of the measurement target substance through the flow cell 20. The concentration of the measurement target substance in the reference water may be equal to or lower than the measurement limit or resolution of the concentration measurement unit 36. The turbidity of the reference water may be equal to or lower than 1 FNU. The wavelength of the light 91 when detecting dirt may be different from the wavelength of the light 91 when measuring the fluorescence of the measurement target substance. The light source 10 may have a light source unit that irradiates light 91 for detecting dirt and a light source unit that irradiates light 91 for detecting fluorescence.

[0028] The transmitted light detection optical system 70 detects transmitted light 94 that is transmitted through the flow cell 20 when light 91 enters the flow cell 20. The transmitted light detection optical system 70 may detect the light that travels straight through the inside of the flow cell 20 and exits as transmitted light 94. The wall 22 may be provided with a window through which the light 91 enters, a window through which the measurement light 92 exits, and a window through which the transmitted light 94 exits. The transmitted light detection optical system 70 detects the amount of transmitted light, which is the amount of transmitted light 94. The transmitted light detection optical system 70 may detect the amount of transmitted light at a set wavelength. The transmitted light detection optical system 70 outputs an electrical signal indicating the amount of transmitted light to the dirt detection unit 40. The transmitted light detection signal processing unit 72 may perform signal processing such as amplification or noise removal on the electrical signal. The transmitted light detection optical system 70 and the transmitted light detection signal processing unit 72 may be used to detect the concentration of the measurement target substance instead of the concentration measurement unit 36.

[0029] When dirt adheres to the wall portion 22, the dirt attenuates the intensity of light, and the amount of transmitted light 94 decreases. Therefore, the degree of dirt on the wall portion 22 can be estimated by detecting the extent to which the amount of transmitted light 94 has attenuated relative to the amount of light 91 emitted by the light source 10. In this example, the amount of attenuation of the amount of transmitted light 94 relative to the light 91 is referred to as the amount of light attenuation. The dirt detection unit 40 calculates the amount of light attenuation and outputs it to the dirt correction unit 42.

[0030] FIG. 2 is a diagram for explaining the correction of the measurement result of the concentration of the target substance. The dirt correction unit 42 performs the correction based on the amount of optical attenuation. The vertical axis of FIG. 2 indicates the concentration or the correction value for correcting the concentration. The horizontal axis indicates the time series. The water quality analyzer 100 measures the concentration of the target substance contained in the sample water from time 1 to time 5. A in the figure indicates the measurement result of the concentration of the target substance before correction by the amount of optical attenuation. In this example, the concentration of the target substance is calculated based on the amount of transmitted light 94. When the transmitted light 94 is attenuated by dirt on the flow cell 20, the concentration of the target substance in the measurement result before correction increases. Therefore, as time passes and dirt accumulates on the flow cell 20, the concentration of the target substance in the measurement result before correction increases. B in the figure indicates the amount of correction based on the amount of optical attenuation. The amount of correction based on the amount of optical attenuation is, for example, the difference between the measured amount of optical attenuation and the amount of optical attenuation at the time of calibration. For example, the amount of correction based on the amount of optical attenuation is calculated from the following formula. Correction amount due to optical attenuation = Measured optical attenuation - Optical attenuation at the time of calibration The amount of correction based on the amount of optical attenuation also increases in accordance with the amount of dirt adhering to the flow cell 20 over time.

[0031] C in the figure shows the concentration of the measured substance corrected before correction using the correction amount based on the optical attenuation. As an example, the correction is performed by subtracting the correction amount based on the optical attenuation from the concentration before correction. As an example, the correction is performed according to the following formula. Density after correction = Density before correction - correction amount due to light attenuation The concentration of the target substance before correction, which does not take into account the effect of dirt on the flow cell 20, increases with the accumulation of dirt on the flow cell 20, but by performing correction based on the amount of optical attenuation, the concentration after correction becomes almost constant. In other words, a result closer to the original concentration of the target substance can be obtained.

[0032] In this example, the case where the concentration of the target substance is calculated based on the transmitted light 94 has been described, but this correction can also be applied when the concentration of the target substance is calculated based on the measurement light 92. In this case, the amount of correction due to the amount of optical attenuation and the sign of addition / subtraction in the formula for the corrected concentration are determined based on the principle of generation of the measurement light 92.

[0033] Fig. 3 is a diagram showing an example of a water quality analyzer 100 according to another embodiment of the present invention. In addition to the configuration described in Fig. 1, the water quality analyzer 100 of this example includes a memory 46. The memory 46 stores the amount of light attenuation detected by the dirt detection unit 40. The dirt correction unit 42 may correct the measurement result of the concentration of the measurement target substance using the stored amount of light attenuation until the next detection of the amount of light attenuation due to dirt on the flow cell 20.

[0034] FIG. 4 is a diagram showing an example of a water quality analysis device 100 according to another embodiment of the present invention. The water quality analysis device 100 of this example includes a cleaning unit 50 in addition to any of the configurations described in FIG. 1 to FIG. 3. In FIG. 4, the cleaning unit 50 is added to the configuration shown in FIG. 1. The cleaning unit 50 cleans the flow cell 20. The cleaning unit 50 may clean the flow cell 20 by flowing clean water or a cleaning solution containing a chemical or the like into the internal space 24 of the flow cell 20, may clean the flow cell 20 using a cleaning solution with a different pH, may clean the flow cell 20 by sweeping the internal space 24 with a member such as a brush, or may clean the flow cell 20 by a combination of these.

[0035] FIG. 5 is a flowchart showing an example of the operation of the water quality analyzer 100 in the embodiment of FIG. 4. In the trigger step S200, the water quality analyzer 100 judges whether or not a predetermined cleaning trigger has been input. When a predetermined cleaning trigger has been input, the water quality analyzer 100 performs a cleaning process (S202 to S210) of the flow cell 20. The trigger signal may be input in response to an operation by a user or the like, may be input automatically in response to a change in the surrounding environment, may be input automatically every time a predetermined period of time has passed, or may be input in response to other factors. The water quality analyzer 100 may perform a measurement process (S212 to S220) of the sample water while a cleaning trigger is not input.

[0036] When a cleaning trigger is input, in a cleaning step S202, the cleaning unit 50 cleans the flow cell 20. After cleaning of the flow cell 20 is completed, in a reference water flow step S204, the water quality analyzer 100 flows reference water having a known concentration of a substance to be measured through the flow cell in order to acquire the amount of light attenuation. In a post-cleaning signal processing step S206, light 91 is incident from the light source 10 onto the flow cell 20 through which the reference water flows. The transmitted light detection optical system 70 detects transmitted light 94 that has passed through the cleaned flow cell 20. The transmitted light detection signal processing unit 72 may perform signal processing such as amplification or noise removal on the electrical signal output by the transmitted light detection optical system 70.

[0037] In a signal correction processing step S208, the transmitted light detection signal processing unit 72 performs an arbitrary correction process on the electrical signal output by the transmitted light detection optical system 70. The correction process includes, for example, a process of correcting a fluctuation in the amount of transmitted light 94 due to a fluctuation in the amount of light 91, or a process of correcting the nonlinearity of the magnitude of the electrical signal relative to the amount of light received by the transmitted light detection optical system 70.

[0038] In the optical attenuation amount acquisition step S210, the dirt detection unit 40 acquires the optical attenuation amount. In this example, the dirt detection unit 40 acquires the optical attenuation amount by flowing reference water into the flow cell 20 after the cleaning unit 50 has cleaned the flow cell 20. This makes it possible to acquire the optical attenuation amount due to dirt that cannot be completely removed by cleaning alone. The correction amount based on the optical attenuation amount in this example is calculated, for example, from the following formula. Correction amount due to optical attenuation = optical attenuation after cleaning - optical attenuation at the time of calibration The dirt detection unit 40 outputs the amount of light attenuation or the amount of correction based on the amount of light attenuation to the dirt correction unit 42.

[0039] After the cleaning is completed or if a predetermined cleaning trigger signal is not input, in sample water flow step S212, the water quality analyzer 100 flows the sample water through the flow cell 20. In measurement signal processing step S214, the concentration measurement unit 36 ​​detects the amount of measurement light 92 and measures the sample water. The concentration measurement unit 36 ​​outputs the measurement result to the contamination correction unit 42.

[0040] In the measurement light intensity correction process S216, the concentration detection signal processing unit 32 performs an arbitrary correction process on the electrical signal output by the concentration detection optical system 30. The correction process includes, for example, a process of correcting the fluctuation in the light intensity of the transmitted light 94 due to the fluctuation in the light intensity of the light 91, or a process of correcting the nonlinearity of the magnitude of the electrical signal relative to the amount of light received by the concentration detection optical system 30. In the light attenuation correction process step S218, the dirt correction unit 42 corrects the measurement result of the concentration of the measurement target substance using the light attenuation. Note that, although the dirt correction unit 42 in this example corrects the value converted into the concentration in advance in the light attenuation correction process step S218, it is also possible to obtain the detection signal before conversion to the concentration in the light attenuation correction process step S218, correct the detection signal, and then convert it into the concentration.

[0041] FIG. 6 is a diagram showing an example of a water quality analysis device 100 according to another embodiment of the present invention. In addition to any of the configurations described in FIG. 1 to FIG. 4, the water quality analysis device 100 of this example includes a light source light quantity monitor 60 and a correction processing unit 62. In addition to the configuration shown in FIG. 1, FIG. 6 includes a light source light quantity monitor 60 and a correction processing unit 62. The light source light quantity monitor 60 detects the light source light quantity of the light 91 before it enters the flow cell 20. The light source light quantity monitor 60 may receive branched light 93 obtained by branching a part of the light 91. The correction processing unit 62 performs signal processing such as amplification of the detection signal and noise removal. The light source light quantity is output to the dirt detection unit 40.

[0042] The dirt detection unit 40 of this example detects dirt on the wall 22 of the flow cell 20 based on the light source light amount and the transmitted light amount. The dirt detection unit 40 corrects the transmitted light amount with the light source light amount, and detects dirt on the wall 22 based on the correction result. For example, the dirt detection unit 40 corrects the transmitted light amount so that the smaller the light source light amount is, the larger the transmitted light amount is, and determines that the smaller the corrected transmitted light amount is, the larger the degree of dirt on the wall 22 is. As an example, the dirt detection unit 40 detects dirt on the wall 22 based on the light amount ratio between the light source light amount and the transmitted light amount (transmitted light amount / light source light amount). The dirt detection unit 40 determines that the smaller the light amount ratio is, the larger the degree of dirt is. In this way, by detecting dirt on the wall 22 using the light source light amount and the transmitted light amount, the influence of deterioration of the light source 10, etc. is reduced, and dirt on the wall 22 can be detected with high accuracy.

[0043] FIG. 7 is a diagram showing prediction of future light attenuation based on past light attenuation. The dirt correction unit 42 in this example holds a history of attenuation information of light attenuation measured in the past, and predicts future light attenuation. Circles in the figure indicate past measurement results. The dirt correction unit 42 may perform at least one of two types of prediction. One of the two types of prediction is prediction of light attenuation due to dirt that cannot be completely removed by cleaning. In this prediction, future light attenuation is predicted based on the light attenuation obtained after cleaning and before the sample water is run. The solid line in the figure represents this prediction. The dirt correction unit 42 may predict future light attenuation by approximating the transition of the measurement result immediately after cleaning with an approximation line 102 such as a straight line or a curve. The dirt correction unit 42 may store information about the approximation line 102 as attenuation information. Since this prediction is a prediction of light attenuation due to dirt that cannot be removed by cleaning, it is possible to make a prediction over the period of use regardless of whether or not future cleaning is performed.

[0044] The other prediction is a prediction of the amount of optical attenuation due to all dirt, including dirt that can be completely removed by cleaning. In this prediction, measurements are performed multiple times between cleanings, and the amount of optical attenuation in the future is predicted based on the changes in the amount of optical attenuation obtained there. The dashed line in the figure represents this prediction. The dirt correction unit 42 may predict the amount of optical attenuation in the future by approximating the progress of multiple measurement results between cleanings with an approximation line 104 such as a straight line or a curve. The dirt correction unit 42 may store information about the approximation line 104 as attenuation information. The dirt correction unit 42 may make a prediction based on attenuation information of the amount of optical attenuation between multiple past cleanings. Since this prediction includes the influence of dirt that can be completely removed by cleaning, the range of the prediction is the range from one cleaning to the next. The dirt correction unit 42 can apply the attenuation information from the past cleanings to any subsequent cleanings.

[0045] The dirt correction unit 42 may estimate the future amount of light attenuation by combining the attenuation information related to the approximation line 102 and the attenuation information related to the approximation line 104. For example, the dirt correction unit 42 estimates the amount of light attenuation immediately after cleaning that is performed at any timing in the future by using the approximation line 102. The dirt correction unit 42 may estimate the transition of the amount of light attenuation after cleaning when cleaning is performed at any timing by applying the approximation line 104 with the amount of light attenuation immediately after cleaning as a starting point.

[0046] In either case of prediction, the accuracy of prediction improves as the number of measurement points increases. The dirt correction unit 42 may change the approximation method of prediction in response to an increase in the number of measurement points. The change in the approximation method is, for example, a change in the order of the approximation formula.

[0047] The dirt correction unit 42 in this example may estimate the time when the predicted value of the light attenuation exceeds the allowable value. The allowable value may be a value previously determined by the user, or may be a value determined for each device. The predicted value may be calculated using either of the two types of predictions described above. The time when the allowable value is exceeded when the prediction of the light attenuation due to dirt that cannot be completely removed by cleaning is used corresponds to t1 in the figure, and the time when the allowable value is exceeded when the prediction of the light attenuation due to all dirt is used corresponds to t2 in the figure. By estimating the time when the allowable value is exceeded, the time for maintenance or the time when the usage limit is reached can be estimated.

[0048] The dirt correction unit 42 may successively correct the correction value of the optical attenuation in the subsequent measurements based on the predicted optical attenuation, thereby making it possible to make corrections taking into account the influence of dirt that accumulates after the measurement of the optical attenuation.

[0049] FIG. 8 is a diagram showing an example of a water quality analysis device 100 according to another embodiment of the present invention. The water quality analysis device 100 of this embodiment has the same configuration as the embodiment described in FIG. 4, but is different in that the cleaning unit 50 and the dirt correction unit 42 cooperate with each other. This embodiment may also be added to any of the configurations of FIG. 1 to FIG. 6. The cleaning unit 50 of this embodiment changes the cleaning method according to the prediction of the light attenuation described above. If it is predicted that the increase in dirt is greater than before, a cleaning method stronger than the previous cleaning method may be adopted. In addition, if the estimated time when the predicted value of the light attenuation exceeds the allowable value is closer to a predetermined reference time, a cleaning method stronger than the previous cleaning method may be adopted. As a cleaning method, the flow cell 20 may be cleaned by flowing a cleaning solution containing fresh water or chemicals into the internal space 24 of the flow cell 20, cleaning may be performed using a cleaning solution with a different pH, the flow cell 20 may be cleaned by sweeping the internal space 24 with a member such as a brush, or the flow cell 20 may be cleaned by a combination of these. When the cleaning method is changed, the cleaning unit 50 may select a cleaning method for the next cleaning depending on the change in the light attenuation before and after cleaning.

[0050] The cleaning unit 50 may determine whether or not cleaning of the flow cell 20 has been completed based on the detection result of the amount of optical attenuation. This determination is made, for example, based on whether or not the amount of optical attenuation falls below a predetermined value. The predetermined value may be a value specific to the device, or may be a value according to the type of sample water. If cleaning of the flow cell 20 does not end within a set period from the start of cleaning, the cleaning method may be changed. The cleaning unit 50 may also select a method for cleaning the flow cell 20 based on the history of sample water that has been flowed through the flow cell 20 in the past. The selection of a cleaning method based on the history of the sample water means, for example, selecting a type or pH of a cleaning solution that is known to be effective against dirt that adheres due to a certain sample water. The history of the sample water may include information indicating the type of dirt component contained in the sample water.

[0051] FIG. 9 is a diagram showing another embodiment when predicting the amount of light attenuation in the future based on the amount of light attenuation in the past. The dirt correction unit 42 in this embodiment calculates the rate of increase of the amount of light attenuation from the past history of the amount of light attenuation between cleaning and the next cleaning, and predicts the amount of light attenuation until the next cleaning based on the calculated rate. The amount of light attenuation includes the amount of light attenuation due to dirt that can be completely removed by cleaning and the amount of light attenuation due to dirt that cannot be completely removed. The dirt correction unit 42 corrects the measurement result of the concentration of the measurement target substance based on the prediction of the change in the amount of light attenuation. The dirt correction unit 42 may successively correct the correction value of the amount of light attenuation in the future measurement based on the prediction of the amount of light attenuation. This allows the correction to be made taking into account the influence of dirt that accumulates after the measurement of the amount of light attenuation. The timing of the next cleaning may also be determined based on the prediction of the change in the amount of light attenuation. This means that cleaning is performed when the prediction of the change in the amount of light attenuation exceeds an allowable value, for example.

[0052] When detecting the amount of optical attenuation between cleanings, the flow rate of the reference water flowing through the flow cell 20 may be set to be equal to or lower than the flow rate of the sample water when measuring the concentration of the substance to be measured. This makes it possible to prevent contaminants from being removed by the flow rate of the reference water, and allows for a more accurate prediction of the amount of optical attenuation. The flow rate of the reference water may be lower than the flow rate of the sample water, and may be 80% or less.

[0053] When detecting the amount of optical attenuation between cleanings, the flow rate of the reference water flowing through the flow cell 20 may be set to be equal to or lower than the flow rate of the cleaning water flowing during cleaning. This makes it possible to prevent dirt that was not removed by cleaning from being removed by the reference water, and allows for a more accurate prediction of the amount of optical attenuation. The flow rate of the reference water may be lower than the flow rate of the cleaning water, and may be 80% or less.

[0054] FIG. 10 is a diagram showing an example of a water quality analyzer 100 according to another embodiment of the present invention. The water quality analyzer 100 of this embodiment includes a scattered light amount detection unit 86 in addition to any of the configurations described in FIG. 1 to FIG. 8. In FIG. 10, the scattered light amount detection unit 86 is included in addition to the configuration of FIG. 1. The scattered light amount detection unit 86 includes a scattered light detection optical system 80 that detects scattered light 96 from the flow cell 20 and outputs an electric signal, and a scattered light signal processing unit 82 that performs signal processing such as amplification or noise removal on the electric signal. In this embodiment, the transmitted light detection optical system 70 and the transmitted light detection signal processing unit 72 are collectively referred to as a transmitted light detection unit 76. In this embodiment, the dirt detection unit 40 detects the amount of light attenuation based on the amount of transmitted light output from the transmitted light detection unit 76 and the amount of scattered light output from the scattered light amount detection unit 86 while reference water is flowing through the flow cell 20. By taking the amount of scattered light into consideration, the amount of light attenuation can be detected more accurately.

[0055] In each embodiment, not only the measurement light 92 but also the transmitted light 94 and the scattered light 96 may be corrected using the optical attenuation amount, thereby making it possible to measure the concentration of the substance to be measured more accurately.

[0056] Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It is clear to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the description of the claims that such modifications and improvements can also be included in the technical scope of the present invention.

[0057] It should be noted that the order of execution of each process, such as operations, procedures, steps, and stages, in the devices, systems, programs, and methods shown in the claims, specifications, and drawings is not specifically stated as "before," "prior to," etc., and may be realized in any order unless the output of a previous process is used in a later process. Even if the operational flow in the claims, specifications, and drawings is explained using "first," "next," etc. for convenience, it does not mean that it is essential to perform the process in this order. [Explanation of symbols]

[0058] 10 light source, 20 flow cell, 22 wall, 24 internal space, 30 concentration detection optical system, 32 concentration detection signal processing unit, 36 concentration measurement unit, 40 dirt detection unit, 42 dirt correction unit, 46 memory, 50 cleaning unit, 60 light source light intensity monitor, 62 correction processing unit, 70 transmitted light detection optical system, 72 transmitted light detection signal processing unit, 76 transmitted light detection unit, 80 scattered light detection optical system, 82 scattered light signal processing unit, 86 scattered light intensity detection unit, 91 light, 92 measurement light, 93 branched light, 94 transmitted light, 96 scattered light, 100 water quality analysis device, 102 approximation line, 104 approximation line

Claims

1. A water quality analyzer for measuring the concentration of a substance to be measured contained in sample water, comprising a wall portion that transmits light and an internal space surrounded by the wall portion, a flow cell through which the sample water passes through the internal space, a light source that irradiates light toward the flow cell, a concentration measurement unit that measures the concentration of the substance to be measured contained in the sample water based on the light to be measured from the flow cell when the sample water is flowing through the flow cell and the light source irradiates light source light to the flow cell, a contamination detection unit that detects the amount of light attenuation due to contamination of the flow cell based on the amount of the light to be measured from the flow cell in a state where reference water having a known concentration of the substance to be measured is flowing through the flow cell, and a contamination correction unit that corrects the measurement result of the concentration of the substance to be measured when the sample water is flowing based on the amount of light attenuation due to contamination of the flow cell. A water quality analyzer comprising the above components.

2. The contamination correction unit stores the detected amount of light attenuation due to contamination of the flow cell, and corrects the measurement result of the concentration of the substance to be measured using the stored amount of light attenuation until the next detection of the amount of light attenuation due to contamination of the flow cell. The water quality analyzer according to Claim 1.

3. The water quality analyzer further comprises a cleaning unit for cleaning the flow cell, and the contamination detection unit detects the amount of light attenuation by flowing the reference water through the flow cell after cleaning the flow cell and before flowing the sample water. The water quality analyzer according to Claim 1 or 2.

4. The water quality analyzer further comprises a light source light amount monitor for detecting the amount of light of the light source light incident on the flow cell, and the contamination detection unit detects the amount of light attenuation using the amount of the light of the light source light when measuring the reference water. The water quality analyzer according to Claim 1 or 2.

5. The contamination correction unit holds a history of attenuation information corresponding to the amount of light attenuation measured in the past and predicts the amount of light attenuation in the future. The water quality analyzer according to Claim 1.

6. The contamination correction unit estimates the time when the predicted value of the amount of light attenuation exceeds an allowable value. The water quality analyzer according to Claim 5.

7. The water quality analyzer further comprises a cleaning unit for cleaning the flow cell, the contamination detection unit detects the amount of light attenuation by flowing the reference water through the flow cell after cleaning the flow cell and before flowing the sample water, and the cleaning unit changes the cleaning method according to the prediction of the amount of light attenuation. The water quality analyzer according to Claim 5.

8. Select the cleaning method for the next cleaning according to the change in the light attenuation amount before and after cleaning when the cleaning method is changed The water quality analyzer according to claim 7

9. The stain detection unit detects the light attenuation amount using the reference water multiple times between one cleaning and the next cleaning, and based on the increasing speed of the light attenuation amount, predicts the change in the light attenuation amount until the next cleaning The stain correction unit corrects the measurement result of the concentration of the substance to be measured based on the prediction of the change in the light attenuation amount The water quality analyzer according to claim 3

10. When detecting the light attenuation amount between one cleaning and the next cleaning, set the flow rate of the reference water to be equal to or lower than the flow rate of the sample water when measuring the concentration of the substance to be measured contained in the sample water The water quality analyzer according to claim 9

11. When detecting the light attenuation amount between one cleaning and the next cleaning, set the flow rate of the reference water to be equal to or lower than the flow rate of the cleaning water flowing during cleaning The water quality analyzer according to claim 9

12. The cleaning unit determines whether the cleaning of the flow cell has ended based on the detection result of the light attenuation amount, and when the cleaning does not end within a set period from the start of the cleaning of the flow cell, change the cleaning method in the cleaning unit The water quality analyzer according to claim 3

13. The cleaning unit selects the cleaning method of the flow cell based on the history of the sample water that has flowed through the flow cell in the past The water quality analyzer according to claim 3

14. A transmitted light detection unit that detects the amount of transmitted light, which is the amount of light of the transmitted light that has passed through the flow cell, and A scattered light amount detection unit that detects the amount of scattered light, which is the amount of light of the scattered light from the reference water, are further provided, and The stain detection unit detects the light attenuation amount due to the stain of the flow cell based on the amount of transmitted light and the amount of scattered light in a state where the reference water is flowing through the flow cell The water quality analyzer according to claim 1 or 2

15. A water quality analyzer for measuring the concentration of a substance to be measured contained in sample water, comprising A wall portion having a light transmission portion, A light source that irradiates light toward the light transmission portion, and A concentration measurement unit that measures the concentration of the substance to be measured contained in the sample water based on the light to be measured from the light transmission portion when the sample water is flowing through the light transmission portion and the light source irradiates the light transmission portion with light from the light source ​ A contamination detection unit that detects the amount of light attenuation due to contamination of the light transmission part based on the amount of the light to be measured from the light transmission part in a state where a reference water with a known concentration of the substance to be measured is flowing through the light transmission part of the light; A contamination correction unit that corrects the measurement result of the concentration of the substance to be measured when the sample water is flowing based on the amount of light attenuation due to contamination of the light transmission part of the light; A water quality analyzer comprising the above.

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