WO2022239641A1 - 水質センサ及び水中の物質濃度測定方法 - Google Patents
水質センサ及び水中の物質濃度測定方法 Download PDFInfo
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- WO2022239641A1 WO2022239641A1 PCT/JP2022/018880 JP2022018880W WO2022239641A1 WO 2022239641 A1 WO2022239641 A1 WO 2022239641A1 JP 2022018880 W JP2022018880 W JP 2022018880W WO 2022239641 A1 WO2022239641 A1 WO 2022239641A1
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 64
- 239000000126 substance Substances 0.000 title claims description 35
- 238000000034 method Methods 0.000 title claims description 33
- 230000003287 optical effect Effects 0.000 claims abstract description 89
- 238000005259 measurement Methods 0.000 claims abstract description 74
- 239000007788 liquid Substances 0.000 claims abstract description 12
- 230000005540 biological transmission Effects 0.000 claims description 70
- -1 nitrate ions Chemical class 0.000 claims description 49
- 238000002835 absorbance Methods 0.000 claims description 42
- 238000001514 detection method Methods 0.000 claims description 32
- 229910002651 NO3 Inorganic materials 0.000 claims description 16
- 238000002834 transmittance Methods 0.000 claims description 14
- 238000004364 calculation method Methods 0.000 claims description 13
- 238000000638 solvent extraction Methods 0.000 claims description 4
- 230000001678 irradiating effect Effects 0.000 claims description 3
- 230000003595 spectral effect Effects 0.000 claims description 2
- 239000000243 solution Substances 0.000 description 7
- 230000000694 effects Effects 0.000 description 5
- 238000010586 diagram Methods 0.000 description 3
- 238000009434 installation Methods 0.000 description 3
- 238000011900 installation process Methods 0.000 description 3
- 238000004891 communication Methods 0.000 description 2
- 238000005192 partition Methods 0.000 description 2
- 229910052594 sapphire Inorganic materials 0.000 description 2
- 239000010980 sapphire Substances 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000000862 absorption spectrum Methods 0.000 description 1
- 239000013505 freshwater Substances 0.000 description 1
- 230000031700 light absorption Effects 0.000 description 1
- 238000012886 linear function Methods 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000013535 sea water Substances 0.000 description 1
- 239000012086 standard solution Substances 0.000 description 1
- 238000013519 translation Methods 0.000 description 1
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/18—Water
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N21/3577—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing liquids, e.g. polluted water
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/47—Scattering, i.e. diffuse reflection
- G01N21/49—Scattering, i.e. diffuse reflection within a body or fluid
- G01N21/53—Scattering, i.e. diffuse reflection within a body or fluid within a flowing fluid, e.g. smoke
- G01N21/534—Scattering, i.e. diffuse reflection within a body or fluid within a flowing fluid, e.g. smoke by measuring transmission alone, i.e. determining opacity
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2201/00—Features of devices classified in G01N21/00
- G01N2201/06—Illumination; Optics
- G01N2201/066—Modifiable path; multiple paths in one sample
- G01N2201/0662—Comparing measurements on two or more paths in one sample
Definitions
- the present disclosure relates to a water quality sensor and a method for measuring substance concentration in water.
- Patent Documents 1 and 2 disclose a technique of calculating the absorbance of a specific substance in a solution based on the Beer-Lambert law and using the calculated absorbance to specify the concentration of the specific substance in the solution. disclosed.
- the absorbance is obtained as follows.
- light emitted from a light-emitting diode passes through a beam splitter.
- a beamsplitter splits a portion of the light onto a reference photodetector and the remaining light is directed through a window into the solution in the flow cell.
- Light passing through the solution is detected by a photodetector.
- the absorbance A is expressed by the following formula (X), where I0 is the intensity of light before entering a medium and I1 is the intensity of light after passing through the medium.
- I1 the intensity of light after passing through the medium.
- A -log(I1/I0)
- Formula (X) Therefore, in equation (X), the absorbance A is obtained by substituting the intensity of light detected by the reference photodetector for I0 and the intensity of light detected by the photodetector for I1.
- the intensity of light detected by the control photodetector is affected not only by the substance to be measured in the solution, but also by the turbidity of the solution.
- the intensity of light detected by the photodetector without passing through the solution is unaffected by turbidity. Therefore, when the absorbance is detected based on the detection values of the control photodetector and the photodetector, errors due to thermal and power fluctuations of the light source, decrease in light intensity, or turbidity may occur. Concerned.
- the present disclosure provides a technique that can measure the concentration of specific substances in water while suppressing the effects of errors caused by thermal and power fluctuations of the light source, reduction in light intensity, or turbidity.
- a water quality sensor of the present invention includes a light source, a beam splitter, a first detector, a second detector, and a measurement space.
- the beam splitter splits the light emitted from the light source into transmitted light and reflected light.
- the first detector detects the transmitted light.
- the second detector detects the reflected light.
- the measuring space is filled with a liquid sample.
- the water quality sensor identifies the concentration of the specific substance in the sample from the detection result of the first detector and the detection result of the second detector.
- a portion of the optical path from the light source to the first detector that passes through the measurement space is defined as a first optical path.
- a portion of the optical path from the light source to the second detector that passes through the measurement space is defined as a second optical path.
- the optical path length of the second optical path is different from the optical path length of the first optical path.
- IC1 is the amount of light detected by the first detector when the measurement space is filled with the sample
- IC2 is the amount of light detected by the second detector when the measurement space is filled with the sample.
- D be the spectroscopic intensity, which is the value obtained by dividing the transmittance of the beam splitter by the reflectance.
- the absorbance AC1 of the light detected by the first detector is represented by the following formula (1)
- the absorbance AC2 of the light detected by the second detector is represented by the following formula ( 2).
- AC1 -log(IC1/I0) Expression (1)
- AC2 -log(IC2/D ⁇ I0) Expression (2)
- the following formula (3) is obtained from the formulas (1) and (2).
- the optical path length of the second optical path is N times the optical path length of the first optical path, the following formula (4) holds.
- the following formula (A) is obtained from the formulas (3) and (4).
- the water quality sensor may include a first transmission window, a second transmission window, and a mirror.
- the first transmissive window may partition between the light source and the measurement space.
- the second transmission window may be provided on a side opposite to the first transmission window across the measurement space, and partition the measurement space and the beam splitter.
- the mirror may reflect the reflected light split by the beam splitter toward the second detector.
- the light source, the first transmissive window, and the second transmissive window are arranged in a positional relationship such that the light emitted from the light source is perpendicularly incident on the surfaces of the first transmissive window and the second transmissive window. good too.
- the reflected light reflected by the mirror enters perpendicularly to the surfaces of the first transmission window and the second transmission window. You may arrange
- the water quality sensor may measure the concentration of nitrate ions, nitrite ions, or ammonium ions.
- the concentration of nitrate ions, nitrite ions, or ammonium ions can be measured.
- the water quality sensor may include a filter that prevents foreign matter from entering the measurement space.
- the inside of the measurement space can be filled with the sample while the intrusion of foreign matter is suppressed by the filter.
- the method for measuring concentration of substances in water of the present invention includes an installation step, an irradiation step, a division step, a first detection step, a second detection step, a calculation step, and an identification step.
- the installation step the measurement space is filled with the liquid sample.
- the irradiation step light is irradiated from a light source.
- the beam splitter splits the light emitted from the light source into transmitted light and reflected light.
- the transmitted light is detected by a first detector.
- the reflected light is detected by a second detector.
- a portion of the optical path from the light source to the first detector that passes through the measurement space is defined as a first optical path.
- a portion of the optical path from the light source to the second detector that passes through the measurement space is defined as a second optical path.
- the calculation step calculates the absorbance AC1 obtained from the following formula (A).
- IC1 is the amount of transmitted light detected in the first detection step
- IC2 is the amount of reflected light detected in the second detection step
- D be the luminous intensity
- N the ratio of the optical path length of the second optical path to the optical path length of the first optical path.
- AC1 [ ⁇ -log(IC2/IC1) ⁇ +logD]/(N-1) Formula (A)
- the absorbance AC1 calculated in the calculation step is used to identify the concentration of the specific substance in the sample.
- the absorbance AC1 of the light detected by the first detector can be obtained by substituting the light intensity IC2 of the reflected light into the formula (A). That is, according to this configuration, the absorbance AC1 can be obtained without using the light amount I0. Therefore, the absorbance AC1 can be obtained by eliminating the influence of the error caused by the turbidity of the sample before and after the light is incident on the sample. Then, using this absorbance AC1, the concentration of the specific substance can be specified. Therefore, according to this configuration, it is possible to measure the concentration of a specific substance in water while suppressing the effects of errors caused by thermal and electric power fluctuations of the light source, reduction in the amount of light, or turbidity.
- the irradiation step is applied to the surface of the first transmission window partitioning the light source and the measurement space and the surface of the second transmission window partitioning the measurement space and the beam splitter.
- the light emitted from the light source may be vertically incident.
- the method for measuring substance concentration in water may include a reflection step. In the reflecting step, the reflected light split by the beam splitter is reflected by a mirror toward the second detector, and the reflected light reflected by the mirror is transmitted through the first transmission window and the second transmission window. may be incident perpendicular to the plane of
- the identifying step may identify the concentration of nitrate ions, nitrite ions, or ammonium ions in the sample using the absorbance AC1 calculated in the calculating step.
- the concentration of nitrate ions, nitrite ions, or ammonium ions can be specified.
- the present invention it is possible to measure the concentration of a specific substance in water while suppressing the effects of errors caused by thermal and power fluctuations of the light source, reduction in light intensity, or turbidity.
- FIG. 1 is a configuration diagram conceptually illustrating the water quality sensor of the first embodiment.
- FIG. 2 is a configuration diagram schematically illustrating the cell portion of the water quality sensor of the first embodiment.
- FIG. 3 is a graph of absorption spectra. 4 is a partially enlarged view of FIG. 3.
- FIG. 5 is a flow chart illustrating the flow of identifying the concentration of a specific substance.
- FIG. 6 is a configuration diagram schematically illustrating the cell portion of the water quality sensor of the second embodiment.
- the water quality sensor 1 shown in FIG. 1 is a sensor that specifies the concentration of a specific substance contained in a liquid sample.
- a liquid sample is, for example, fresh water or seawater, and is a concept that includes liquids other than water.
- the liquid sample preferably has a certain degree of transparency.
- the turbidity measured by the scattered light method or the transmitted light method preferably has a degree of formazine of 0 degree or more and 500 degrees or less.
- the specific substance may be any light-absorbing substance, such as nitrate ions, nitrite ions, and ammonium ions.
- the water quality sensor 1 identifies the concentration of a specific substance using the absorbance of the specific substance.
- the water quality sensor 1 includes a sensor body 10, a signal cable 70, and an arithmetic device 80.
- the sensor body 10 has a waterproof structure.
- the sensor main body 10 has a form extending in one direction.
- a signal cable 70 is connected to the base end side of the sensor main body 10 .
- the sensor main body 10 has a connector portion 11, a body portion 12, and a cell portion 13 from the proximal side to the distal side.
- a signal cable 70 is connected to the base end side of the connector portion 11 , and the base end side of the body portion 12 is connected to the distal end side of the connector portion 11 .
- the body part 12 has a cylindrical body 12A.
- the body part 12 has an operational amplifier, an AD converter, an MPU, a voltage converter, etc. (not shown) inside the cylindrical body 12A.
- a cell portion 13 is connected to the tip side of the cylindrical body 12A.
- the cell part 13 is provided on the tip side of the water quality sensor 1 .
- the cell portion 13 includes a first tubular portion 21 , a second tubular portion 22 , a connecting portion 23 , and a measurement space 24 .
- the first cylindrical portion 21 and the second cylindrical portion 22 are formed in a cylindrical shape coaxial with the water quality sensor 1 and are spaced apart from each other in the extending direction of the water quality sensor 1 .
- the first tubular portion 21 is arranged on the proximal end side, and the second tubular portion 22 is arranged on the distal end side.
- the first tubular portion 21 and the second tubular portion 22 are connected by a pair of connecting portions 23 .
- a measurement space 24 is formed between the first tubular portion 21 and the second tubular portion 22 .
- the measurement space 24 continues to the outside of the water quality sensor 1 .
- the cell part 13 includes a space forming part 24A that forms a space 24 for measurement.
- the measurement space 24 is formed surrounded by the first cylindrical portion 21 , the second cylindrical portion 22 and the connecting portion 23 .
- the cell section 13 includes a connection space 25 and a filter 26, as shown in FIG.
- the connection spaces 25 are spaces arranged on the left and right sides of the measurement space 24 in FIG. 2 and connect the measurement space 24 to the outside of the water quality sensor 1 .
- the filter 26 is provided in the connection space 25 and has a function of preventing foreign matter from entering the measurement space 24 from the outside of the water quality sensor 1 .
- the filters 26 are provided in pairs on both sides (left and right sides in FIG. 2) of the measurement space 24 .
- the cell section 13 includes a light source 31 , a transmission window 32 , a beam splitter 33 , a first detector 34 and a second detector 35 .
- the light source 31 has a function of emitting light having directivity.
- the light source 31 has, for example, an LED.
- the light source 31 is mounted to irradiate light of a wavelength corresponding to an object whose concentration is to be specified.
- Figures 3 and 4 disclose graphs showing the relationship between wavelength and absorbance.
- G1 corresponds to nitrite ions
- G2 corresponds to nitrate ions
- G3 corresponds to ammonium ions.
- the first wavelength band In the wavelength band of 350 nm or more and 400 nm or less (hereinafter referred to as the first wavelength band), only nitrite ions have light absorption properties. Therefore, when trying to identify the concentration of nitrite ions, an LED that emits light in the first wavelength band is mounted.
- Nitrate ions and nitrite ions have light absorbing properties in a wavelength band of 260 nm or more and 350 nm or less (hereinafter referred to as a second wavelength band). Therefore, when trying to specify the concentration of nitrate ions, an LED that emits light in the first wavelength band and an LED that emits light in the second wavelength band are mounted. Further, as shown in FIG.
- nitrate ions, nitrite ions, and ammonium ions have absorption characteristics in a wavelength band of 940 nm or more and 1000 nm or less (hereinafter referred to as the third wavelength band). Therefore, when trying to specify the concentration of ammonium ions, an LED that emits light in the first wavelength band, an LED that emits light in the second wavelength band, and an LED that emits light in the third wavelength band is installed.
- an LED that emits light in a first wavelength band, an LED that emits light in a second wavelength band, and an LED that emits light in a third wavelength band are mounted will be described.
- the LED that emits light in the third wavelength band only needs to be installed.
- the light source 31 is arranged on the proximal end side of the measurement space 24 and irradiates the measurement space 24 with light.
- the transmission window 32 is a window through which the light emitted from the light source 31 is transmitted.
- the transmissive window 32 is, for example, a sapphire window.
- the transmission window 32 has a plate shape.
- the transmission window 32 is arranged inside the first cylindrical portion 21 .
- the beam splitter 33 has a function of splitting the light emitted from the light source 31 into transmitted light and reflected light.
- the transmittance TR and reflectance RR of the beam splitter 33 may or may not be the same. That is, the spectroscopic intensity D, which is the value obtained by dividing the transmittance TR of the beam splitter 33 by the reflectance RR (TR/RR), may be 1 or may not be 1.
- the beam splitter 33 is arranged inside the second cylindrical portion 22 .
- the beam splitter 33 is arranged on the opposite side of the transmission window 32 across the measurement space 24 .
- the first detector 34 and the second detector 35 are elements that convert light into electrical signals, and are configured as photodiodes, for example.
- the light source 31, transmission window 32, measurement space 24, beam splitter 33 and first detector 34 are arranged in order on a straight line. Therefore, the light emitted from the light source 31 passes through the transmission window 32, the measurement space 24 and the beam splitter 33 in order. The transmitted light that has passed through the beam splitter 33 is detected by the first detector 34 .
- the second detector 35 is arranged on the same side as the light source 31 (specifically, the base end side) with respect to the measurement space 24 . Reflected light reflected by the beam splitter 33 passes through the transmission window 32 and is detected by the second detector 35 .
- the portion of the optical path from the light source 31 to the first detector 34 that passes through the measurement space 24 is defined as a first optical path L1.
- a portion of the optical path from the light source 31 to the second detector 35 that passes through the measurement space 24 is defined as a second optical path L2.
- the first detector 34 and the second detector 35 are arranged such that the optical path length of the second optical path L2 is different from the optical path length of the first optical path L1.
- the optical path length of the second optical path L2 is set to be twice the optical path length of the first optical path L1.
- Signals indicating detection results by the first detector 34 and the second detector 35 are amplified by the operational amplifier of the body part 12 and input to the arithmetic device 80 through the signal cable 70 .
- the computing device 80 is connected to the sensor body 10 via the signal cable 70 and can receive the detection results of the first detector 34 and the second detector 35 in the sensor body 10 .
- Arithmetic device 80 has a power supply unit 81 , a computation unit 82 , and a communication unit 83 .
- the power supply unit 81 may be a battery, or may be a power supply circuit that supplies power supplied from an external power supply to each device.
- the calculation unit 82 is configured with, for example, an MPU.
- the calculation unit 82 calculates the absorbance of the specific substance based on the detection results of the first detector 34 and the second detector 35, and specifies the concentration of the specific substance based on the calculated absorbance.
- the communication unit 83 can communicate with an external device such as the terminal device 90 .
- the terminal device 90 is a mobile terminal, a personal computer, or the like.
- FIG. 5 The method for measuring the concentration of substances in water includes, as shown in FIG. 5, an installation process, an irradiation process, a division process, a first detection process, a second detection process, a calculation process, and an identification process.
- the installation process is a process for filling the measurement space 24 with a liquid sample.
- the sensor body 10 of the water quality sensor 1 is directly put into the liquid sample.
- the sample enters the measurement space 24 and fills the measurement space 24 with the sample.
- the irradiation step is a step of irradiating light from the light source 31 .
- the light source 31 emits light according to the instruction from the arithmetic device 80 .
- the measurement start condition is, for example, that a preset time condition is satisfied, or that a start operation is performed using an operation unit (not shown).
- the light source 31 sequentially emits light in a first wavelength band, a second wavelength band and a third wavelength band.
- the splitting step is a step of splitting the light emitted from the light source 31 into transmitted light and reflected light by the beam splitter 33 .
- the first detection step is a step of detecting transmitted light with the first detector 34 .
- the first detector 34 detects the transmitted light and outputs a signal indicating the detection result.
- the second detection process is a process of detecting reflected light with the second detector 35 .
- the second detector 35 detects the reflected light and outputs a signal indicating the detection result.
- the calculation step is a step executed by the calculation device 80, and is a step of calculating the absorbance AC1 obtained from the following formula (A).
- AC1 [ ⁇ -log(IC2/IC1) ⁇ +logD]/(N-1) Formula (A)
- IC1 is the amount of transmitted light detected in the first detection step. That is, IC1 is the amount of light detected by the first detector 34 when the measurement space 24 is filled with the sample.
- IC2 is the amount of reflected light detected in the second detection step. That is, IC2 is the amount of light detected by the second detector 35 when the measurement space 24 is filled with the sample.
- Formula (A) is derived as follows. Let I0 be the amount of light before entering the sample or the amount of light detected by the first detector 34 and the second detector 35 when the measurement space 24 is filled with the standard solution. In this case, from the Beer-Lambert law, the absorbance AC1 of the light detected by the first detector 34 is expressed by the following formula (1), and the absorbance AC2 of the light detected by the second detector 35 is expressed by the following formula: It is represented by Formula (2).
- AC1 -log(IC1/I0) Expression (1)
- AC2 -log(IC2/D ⁇ I0) Expression (2)
- the following formula (3) is obtained from the formulas (1) and (2).
- the optical path length of the second optical path L2 is N times the optical path length of the first optical path L1
- the following formula (4) holds.
- the following formula (A) is obtained from the formulas (3) and (4).
- AC1 [ ⁇ -log(IC2/IC1) ⁇ +logD]/(N-1) Formula (A)
- the first detector 34 It is possible to obtain the absorbance AC1 of the light detected at . That is, according to the water quality sensor 1, the absorbance AC1 of the light detected by the first detector 34 can be obtained without using the light intensity I0. Therefore, the absorbance AC1 can be obtained by eliminating the influence of the error caused by the turbidity of the sample before and after the light is incident on the sample.
- the absorbance AC1 is calculated using the above formula (A) for each of the first wavelength band, the second wavelength band, and the third wavelength band.
- the identification step is a step executed by the computing device 80, and is a step of identifying the substance concentration in the sample using the absorbance AC1 calculated in the computing step.
- a known method can be adopted as a specific method for specifying the substance concentration in the sample.
- correspondence data indicating the correspondence between absorbance and concentration is stored in advance, and the concentration is specified based on this correspondence data and the absorbance AC1 calculated in the calculation step.
- the correspondence data may be an arithmetic expression such as a linear function, or may be a table.
- the concentration of nitrite ions is identified based on the absorbance AC1 corresponding to the first wavelength band. Furthermore, by specifying the concentration containing both nitrate ions and nitrite ions based on the absorbance AC1 corresponding to the second wavelength band, and subtracting the concentration of nitrite ions from the concentration containing both, Identify concentration. Furthermore, based on the absorbance AC1 corresponding to the third wavelength band, the concentrations containing the three types of nitrate ions, nitrite ions, and ammonium ions are specified, and the concentrations of the nitrate ions and the nitrite ions are determined from the concentrations containing the three types. Subtraction determines the concentration of ammonium ions.
- the absorbance AC1 can be obtained by eliminating the influence of the error caused by the turbidity of the sample before and after it is incident on the sample. Then, the concentration can be specified using this absorbance AC1. Therefore, it is possible to measure the concentration of substances in water while suppressing the effects of errors caused by thermal and electric power fluctuations of the light source, reduction in the amount of light, or turbidity.
- concentrations of nitrate ions, nitrite ions, and ammonium ions can be measured.
- a water quality sensor 201 according to a second embodiment differs from the water quality sensor 1 according to the first embodiment in the configuration of the cell portion, but is common in other respects.
- symbol is attached
- FIG. 6 shows the cell part 213 of the water quality sensor 201 of the second embodiment.
- the cell part 213 is provided on the tip side of the water quality sensor 201 .
- the cell portion 213 includes a first tubular portion 21 , a second tubular portion 22 , a connecting portion 23 , a measurement space 24 , a connection space 25 and a filter 26 .
- the measurement space 24 continues to the outside of the water quality sensor 201 .
- the cell section 213 includes a space forming section 24A that forms the measurement space 24 .
- the connection spaces 25 are spaces arranged on the left and right sides of the measurement space 24 in FIG. 6 and connect the measurement space 24 to the outside of the water quality sensor 201 .
- the filter 26 is provided in the connection space 25 and has a function of preventing foreign matter from entering the measurement space 24 from the outside of the water quality sensor 201 .
- the filters 26 are provided in pairs on both sides of the measurement space 24 (left and right sides in FIG. 6).
- the cell section 213 includes a light source 31 , a first transmission window 241 , a second transmission window 242 , a beam splitter 243 , a mirror 244 , a first detector 34 and a second detector 35 .
- the first transmission window 241 and the second transmission window 242 are windows through which the light emitted from the light source 31 is transmitted.
- the first transmission window 241 and the second transmission window 242 are, for example, sapphire windows.
- the first transmission window 241 and the second transmission window 242 are plate-shaped.
- the first transmission window 241 is arranged inside the first cylindrical portion 21 .
- a first transmission window 241 separates the light source 31 and the measurement space 24 .
- the second transmission window 242 is arranged inside the second cylindrical portion 22 .
- the second transmission window 242 is provided on the opposite side of the measurement space 24 from the first transmission window 241 .
- a second transmission window 242 separates the measurement space 24 and the beam splitter 243 .
- the beam splitter 243 has a function of splitting the light emitted from the light source 31 into transmitted light and reflected light.
- the transmittance TR and reflectance RR of the beam splitter 243 may or may not be the same. That is, the spectroscopic intensity D, which is the value obtained by dividing the transmittance TR of the beam splitter 243 by the reflectance RR (TR/RR), may be 1 or may not be 1.
- the mirror 244 reflects the reflected light split by the beam splitter 243 toward the reflecting measurement space 24 .
- the mirror 244 is arranged on the same side as the beam splitter 243 (specifically, the tip side) with respect to the measurement space 24 .
- the light source 31, the first transmission window 241, the measurement space 24, the second transmission window 242, the beam splitter 243, and the first detector 34 are arranged in order on a straight line. Therefore, the light emitted from the light source 31 passes through the first transmission window 241, the measurement space 24, the second transmission window 242, and the beam splitter 243 in order.
- the transmitted light that has passed through the beam splitter 243 is detected by the first detector 34 .
- the second detector 35 is arranged on the same side as the light source 31 (specifically, the base end side) with respect to the measurement space 24 .
- the reflected light reflected by the beam splitter 243 is reflected by the mirror 244 .
- the mirror 244, the second transmission window 242, the measurement space 24, the first transmission window 241, and the second detector 35 are arranged in order on a straight line.
- the reflected light reflected by the mirror 244 passes through the second transmission window 242 , the measurement space 24 and the first transmission window 241 in order, and is detected by the second detector 35 .
- the first transmissive window 241 has a first surface 241A facing the light source 31 and a second surface 241B opposite to the first surface 241A.
- the second surface 241B faces the second transmissive window 242 .
- the second transmissive window 242 has a third surface 242A facing the second surface 241B of the first transmissive window 241, and a fourth surface 242B opposite to the third surface 242A.
- the fourth surface 242B faces the beam splitter 243 side.
- the light source 31, the first transmissive window 241, and the second transmissive window 242 are configured so that the light emitted from the light source 31 is perpendicular to the first surface 241A of the first transmissive window 241 and the third surface 242A of the second transmissive window 242. are arranged in a positional relationship in which they are incident on the The beam splitter 243 , the mirror 244 , the first transmission window 241 and the second transmission window 242 allow the light reflected by the mirror 244 to pass through the second surface 241 B of the first transmission window 241 and the fourth surface 242 B of the second transmission window 242 .
- the portion of the optical path from the light source 31 to the first detector 34 that passes through the measurement space 24 is defined as a first optical path L21.
- a portion of the optical path from the light source 31 to the second detector 35 that passes through the measurement space 24 is defined as a second optical path L22.
- the first detector 34 and the second detector 35 are arranged such that the optical path length of the second optical path L22 is different from the optical path length of the first optical path L21.
- the optical path length of the second optical path L22 is set to be twice the optical path length of the first optical path L21.
- the following description relates to a method for measuring substance concentrations in water using the water quality sensor 201.
- FIG. The method for measuring the concentration of substances in water includes a reflection process in addition to the installation process, the irradiation process, the division process, the first detection process, the second detection process, the calculation process, and the identification process described in the first embodiment.
- the light emitted from the light source 31 is vertically incident on the first surface 241A of the first transmissive window 241 and the third surface 242A of the second transmissive window 242 .
- the reflected light split by the beam splitter 243 is reflected by the mirror 244, and the reflected light reflected by the mirror 244 is transmitted to the second surface 241B of the first transmission window 241 and the fourth surface 242B of the second transmission window 242. incident perpendicular to the
- the water quality sensor 201 of the second embodiment it is possible to suppress a decrease in transmittance when the light emitted from the light source 31 is transmitted through the first transmission window 241 and the second transmission window 242 . Moreover, according to this configuration, it is possible to suppress a decrease in transmittance when the reflected light reflected by the mirror 244 is transmitted through the first transmission window 241 and the second transmission window 242 .
- the optical path length of the second optical path is twice the optical path length of the first optical path.
- the water quality sensor is configured to include a filter, but may be configured to not include a filter.
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Abstract
Description
特許文献1では、発光ダイオードから照射された光が、ビームスプリッタを通過する。ビームスプリッタは、光の一部を分岐して対照光検出器に向け、残りの光は窓を通してフローセル内の溶液に導かれる。溶液を通過した光は、光検出器で検出される。
ランベルト・ベールの法則によれば、媒質に入射する前の光の強度をI0、媒質を透過した後の光の強度をI1としたとき、吸光度Aは下記式(X)で表される。
A=-log(I1/I0)・・・式(X)
よって、式(X)において、対照光検出器が検出した光の強度をI0に代入し、光検出器が検出した光の強度をI1に代入することで、吸光度Aが求められる。
AC1=-log(IC1/I0)・・・式(1)
AC2=-log(IC2/D・I0)・・・式(2)
式(1)、式(2)から下記式(3)が求められる。
AC2-AC1
={-log(IC2/D・I0)}-{-log(IC1/I0)}
=-log(IC2/IC1)+logD・・・式(3)
他方、第2光路の光路長が第1光路の光路長のN倍である場合、下記式(4)が成り立つ。
AC2-AC1
=N・AC1-AC1
=(N―1)・AC1・・・式(4)
式(3)と式(4)から下記式(A)が求められる。
AC1=[{-log(IC2/IC1)}+logD]/(N―1)・・・式(A)
よって、予め把握しておいた分光度D、及び光路長の比Nと、水質センサで検出された光量IC1及び光量IC2を式(A)に代入することで、第1検出器で検出される光の吸光度AC1を求めることができる。つまり、この水質センサによれば、光量I0を用いることなく吸光度AC1を求めることができる。このため、サンプルに入射する前と後とでサンプルの濁度に起因して生じる誤差の影響を排除して、吸光度AC1を求めることができる。そして、この吸光度AC1を用いて特定物質の濃度を特定することができる。従って、この構成によれば、光源の熱的・電力的な揺らぎ、光量の低下、または濁度に起因した誤差の影響を抑制しつつ、水中の特定物質の濃度を測定し得る。
AC1=[{-log(IC2/IC1)}+logD]/(N―1)・・・式(A)
上記特定工程では、上記演算工程で算出された吸光度AC1を用いて上記サンプル内の特定物質の濃度を特定する。
1-1.水質センサ1の構成
図1に示す水質センサ1は、液体のサンプルに含まれる特定物質の濃度を特定するセンサである。液体のサンプルは、例えば淡水や海水などであり、水以外の液体も含む概念である。液体のサンプルは、ある程度の透明度を有することが好ましく、例えば、散乱光法、又は、透過光法にて測定した濁度がホルマジン度で0度以上且つ500度以下であることが好ましい。特定物質は、吸光物質であればよく、例えば、硝酸イオン、亜硝酸イオン、アンモニウムイオンなどである。水質センサ1は、特定物質の吸光度を利用して特定物質の濃度を特定するものである。
水中の物質濃度測定方法は、図5に示すように、設置工程と、照射工程と、分割工程と、第1検出工程と、第2検出工程と、演算工程と、特定工程とを含む。
AC1=[{-log(IC2/IC1)}+logD]/(N―1)・・・式(A)
なお、IC1は、第1検出工程で検出した透過光の光量である。つまり、IC1は、測定用空間24がサンプルで満たされた状態で第1検出器34が検出する光量である。IC2は、第2検出工程で検出した反射光の光量である。つまり、IC2は、測定用空間24がサンプルで満たされた状態で第2検出器35が検出する光量である。Dは、ビームスプリッタ33の透過率TRを反射率RRで割った値である分光度である。つまり、D=TR/RRである。Nは、第1光路L1の光路長に対する第2光路L2の光路長の割合である。つまり、N=L2/L1である。但し、Nは1以外である。
サンプルに入射する前の光の光量、あるいは、仮に測定用空間24が標準液で満たされた状態で第1検出器34及び第2検出器35が検出する光量をI0とする。この場合、ランベルト・ベールの法則より、第1検出器34で検出される光の吸光度AC1は、下記式(1)で表され、第2検出器35で検出される光の吸光度AC2は、下記式(2)で表される。
AC1=-log(IC1/I0)・・・式(1)
AC2=-log(IC2/D・I0)・・・式(2)
式(1)、式(2)から下記式(3)が求められる。
AC2-AC1
={-log(IC2/D・I0)}-{-log(IC1/I0)}
=-log(IC2/IC1)+logD・・・式(3)
他方、第2光路L2の光路長が第1光路L1の光路長のN倍である場合、下記式(4)が成り立つ。
AC2-AC1
=N・AC1-AC1
=(N―1)・AC1・・・式(4)
式(3)と式(4)から下記式(A)が求められる。
AC1=[{-log(IC2/IC1)}+logD]/(N―1)・・・式(A)
第2実施形態の水質センサ201は、セル部の構成が第1実施形態の水質センサ1とは異なり、その他の点で共通する。以下では、第1実施形態と同じ構成について同じ符号を付し、詳しい説明を省略する。
水中の物質濃度測定方法は、第1実施形態で説明した設置工程、照射工程、分割工程、第1検出工程、第2検出工程、演算工程、及び特定工程に加え、反射工程を含む。
本発明は上記記述及び図面によって説明した実施形態に限定されるものではなく、例えば次のような実施形態も本発明の技術的範囲に含まれる。また、上述した実施形態や後述する実施形態の様々な特徴は、矛盾しない組み合わせであればどのように組み合わされてもよい。
24…測定用空間
26…フィルタ
31…光源
33…ビームスプリッタ
34…第1検出器
35…第2検出器
201…水質センサ
241…第1透過窓
242…第2透過窓
243…ビームスプリッタ
244…ミラー
AC1…第1検出器で検出される光の吸光度
D…分光度
IC1…第1検出器が検出する光の光量
IC2…第2検出器が検出する光の光量
L1…第1光路
L2…第2光路
N…第1光路の光路長に対する第2光路の光路長の割合
Claims (8)
- 光源と、
前記光源から照射される光を透過光と反射光に分割するビームスプリッタと、
前記透過光を検出する第1検出器と、
前記反射光を検出する第2検出器と、
液体のサンプルで満たされる測定用空間と、
を備え、
前記第1検出器での検出結果と前記第2検出器での検出結果から前記サンプルの特定物質の濃度を特定する水質センサであって、
前記光が前記光源から前記第1検出器に至るまでの光路のうち前記測定用空間内を通る部分を第1光路とし、
前記光が前記光源から前記第2検出器に至るまでの光路のうち前記測定用空間内を通る部分を第2光路とするとき、
前記第2光路の光路長が前記第1光路の光路長と異なる水質センサ。 - 前記光源と前記測定用空間との間を仕切る第1透過窓と、
前記測定用空間を挟んで前記第1透過窓側とは反対側に設けられ、前記測定用空間と前記ビームスプリッタとの間を仕切る第2透過窓と、
前記ビームスプリッタで分割された前記反射光を前記第2検出器に向けて反射させるミラーと、を備え、
前記光源、前記第1透過窓及び前記第2透過窓は、前記光源から照射された光が前記第1透過窓及び前記第2透過窓の面に対して垂直に入射する位置関係で配置され、
前記ビームスプリッタ、前記ミラー、前記第1透過窓及び前記第2透過窓は、前記ミラーで反射された前記反射光が前記第1透過窓及び前記第2透過窓の面に対して垂直に入射する位置関係で配置される請求項1に記載の水質センサ。 - 硝酸イオン、亜硝酸イオン、又はアンモニウムイオンの濃度を測定対象とする請求項1又は請求項2に記載の水質センサ。
- 前記測定用空間に異物が侵入することを抑制するフィルタを備える請求項3に記載の水質センサ。
- 前記測定用空間に異物が侵入することを抑制するフィルタを備える請求項1又は請求項2に記載の水質センサ。
- 測定用空間内が液体のサンプルで満たされるようにする設置工程と、
光源から光を照射させる照射工程と、
前記光源から照射された光をビームスプリッタによって透過光と反射光に分割する分割工程と、
第1検出器によって前記透過光を検出する第1検出工程と、
第2検出器によって前記反射光を検出する第2検出工程と、
を含み、
前記光が前記光源から前記第1検出器に至るまでの光路のうち前記測定用空間内を通る部分を第1光路とし、
前記光が前記光源から前記第2検出器に至るまでの光路のうち前記測定用空間内を通る部分を第2光路とするとき、
前記第1検出工程で検出した前記透過光の光量をIC1、前記第2検出工程で検出した前記反射光の光量をIC2、前記ビームスプリッタの透過率を反射率で割った値である分光度をD、前記第1光路の光路長に対する前記第2光路の光路長の割合をNとし、下記式(A)から求められる吸光度AC1を算出する演算工程と、
前記演算工程で算出された吸光度AC1を用いて前記サンプル内の特定物質の濃度を特定する特定工程と、を含む水中の物質濃度測定方法。
AC1=[{-log(IC2/IC1)}+logD]/(N―1)・・・式(A) - 前記照射工程は、前記光源と前記測定用空間との間を仕切る第1透過窓の面と、前記測定用空間と前記ビームスプリッタとの間を仕切る第2透過窓の面とに対して、前記光源から照射される光を垂直に入射させ、
更に、前記ビームスプリッタで分割された前記反射光をミラーによって前記第2検出器に向けて反射させ、前記ミラーによって反射された前記反射光を前記第1透過窓及び前記第2透過窓の面に対して垂直に入射させる反射工程を含む請求項6に記載の水中の物質濃度測定方法。 - 前記特定工程は、前記演算工程で算出された吸光度AC1を用いて前記サンプル内の硝酸イオン、亜硝酸イオン、又はアンモニウムイオンの濃度を特定する請求項6又は請求項7に記載の水中の物質濃度測定方法。
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