Turbidity measuring method and turbidity meter

文档序号：1213956 发布日期：2020-09-04 浏览：24次中文

阅读说明：本技术 浊度测定方法及浊度计 (Turbidity measuring method and turbidity meter ) 是由清水光锹形武志后藤爱半田纱织于 2020-02-27 设计创作，主要内容包括：浊度测定方法包含下述步骤：照射出具有第一光谱(E1)的第一照射光(L1)；对基于第一照射光(L1)的第一被测定光(ML1)进行检测；照射出具有与第一光谱(E1)不同的第二光谱(E2)的第二照射光(L2)；对基于第二照射光(L2)的第二被测定光(ML2)进行检测；对被测定液的浊度进行计算；以及对与第一照射光(L1)相关联的浊度计算所涉及的第一参数及与第二照射光(L2)相关联的浊度计算所涉及的第二参数中的至少一者进行校正,以使得在对被测定液的浊度进行计算的步骤中计算出的浊度,与成为比较的基准的使用其他光源而测定出的被测定液的浊度对应。(The turbidity measuring method comprises the following steps: irradiating first irradiation light (L1) having a first spectrum (E1); detecting first light to be measured (ML1) based on the first irradiation light (L1); irradiating second irradiation light (L2) having a second spectrum (E2) different from the first spectrum (E1); detecting second light to be measured (ML2) based on the second irradiation light (L2); calculating the turbidity of the liquid to be measured; and correcting at least one of a first parameter relating to the calculation of the turbidity associated with the first irradiation light (L1) and a second parameter relating to the calculation of the turbidity associated with the second irradiation light (L2) so that the turbidity calculated in the step of calculating the turbidity of the liquid to be measured corresponds to the turbidity of the liquid to be measured using another light source as a reference for comparison.)

1. A turbidity measuring method for measuring the turbidity of a liquid to be measured,

the turbidity measuring method comprises the following steps:

irradiating the measurement liquid with first irradiation light having a first spectrum;

acquiring a detection signal of first measurement light based on the first irradiation light irradiated to the measurement liquid;

irradiating the measurement liquid with second irradiation light having a second spectrum different from the first spectrum;

acquiring a detection signal of second measurement light based on the second irradiation light irradiated to the measurement liquid;

calculating the turbidity of the measurement liquid based on the detection signals of the first measurement light and the second measurement light; and

at least one of a first parameter relating to calculation of turbidity associated with the first irradiation light and a second parameter relating to calculation of turbidity associated with the second irradiation light is corrected so that the turbidity calculated in the step of calculating the turbidity of the liquid to be measured corresponds to the turbidity of the liquid to be measured using another light source as a reference for comparison.

2. The turbidity assay method according to claim 1, wherein,

a first parameter relating to the turbidity calculation, including a first detection signal intensity of the first measured light detected,

a second parameter relating to the turbidity calculation, including a second detection signal intensity of the second measured light detected,

in the correcting step, at least one of the first detection signal strength and the second detection signal strength is corrected.

3. The turbidity assay method according to claim 2, wherein,

the step of irradiating the measurement liquid with the first irradiation light and the step of irradiating the measurement liquid with the second irradiation light are performed at different timings from each other.

4. The turbidity assay method according to claim 2 or 3, wherein,

the first measurement target light and the second measurement target light each include a transmitted light transmitted through the measurement target liquid and a scattered light scattered by the measurement target liquid.

5. The turbidity assay method according to claim 4, wherein,

in the step of calculating the turbidity of the measurement liquid, if a first detection signal intensity of first scattered light included in the first measurement light is represented by I_S1And setting a first detection signal intensity of first transmitted light included in the first measurement light to I_T1And a second detection signal intensity of second scattered light included in the second measurement target light is represented by I_S2And setting a second detection signal intensity of second transmitted light included in the second measurement light to I_T2The turbidity N is calculated by the following formula 1,

[ formula 1 ]

K is the sensitivity coefficient for turbidity calculation, I_S1(0)Is a first detected signal intensity, I, of the first scattered light obtained for a liquid with a turbidity of 0 DEG_T1(0)Is a first detection signal intensity, I, of the first transmitted light obtained for a liquid having a turbidity of 0 DEG_S2(0)Is a second detected signal intensity, I, of the second scattered light obtained for a liquid with a turbidity of 0 DEG_T2(0)The second detection signal intensity of the second transmitted light obtained for a liquid having a turbidity of 0 degrees is represented by α, which is a correction coefficient.

6. The turbidity assay method according to claim 1, wherein,

the first parameter involved in the turbidity calculation includes a first drive current of a first LED light source illuminating the first illumination light,

the second parameter involved in the turbidity calculation includes a second drive current of a second LED light source illuminating the second illumination light,

in the correcting, at least one of the first drive current and the second drive current is corrected.

7. The turbidity assay method according to any one of claims 1 to 6, wherein,

further comprising the steps of:

irradiating the measurement liquid with third irradiation light having a third spectrum; and

acquiring a detection signal of third measurement light based on the third irradiation light irradiated to the measurement liquid,

in the step of calculating the turbidity of the measurement liquid, the turbidity of the measurement liquid is calculated based on the detection signals of the first, second, and third measurement lights,

in the correcting step, a first parameter relating to calculation of turbidity associated with the first irradiation light, a second parameter relating to calculation of turbidity associated with the second irradiation light, and a third parameter relating to calculation of turbidity associated with the third irradiation light are corrected.

8. A turbidimeter for measuring the turbidity of a liquid to be measured,

the turbidimeter comprises:

a first light source unit that irradiates the measurement liquid with first irradiation light having a first spectrum;

a second light source unit that irradiates the measurement liquid with second irradiation light having a second spectrum different from the first spectrum;

a light receiving unit that acquires a detection signal of first measurement light based on the first irradiation light irradiated to the measurement liquid and a detection signal of second measurement light based on the second irradiation light irradiated to the measurement liquid; and

a control unit that calculates a turbidity of the liquid to be measured based on the detection signals of the first light to be measured and the second light to be measured,

the control unit corrects at least one of a first parameter relating to calculation of turbidity associated with the first irradiation light and a second parameter relating to calculation of turbidity associated with the second irradiation light so that the turbidity calculated by the control unit corresponds to the turbidity of the liquid to be measured using another light source as a reference for comparison.

9. The turbidimeter of claim 8,

the first parameter relating to the turbidity calculation includes a first detection signal intensity of the first measurement light detected by the light receiving unit,

a second parameter relating to the turbidity calculation, including a second detection signal intensity of the second measurement target light detected by the light receiving unit,

the control unit corrects at least one of the first detection signal intensity and the second detection signal intensity.

10. The turbidimeter of claim 9,

the control unit causes the first light source unit and the second light source unit to operate at different timings from each other, and causes the first irradiation light and the second irradiation light to irradiate at different timings from each other.

11. The turbidimeter of claim 9 or 10,

12. The turbidimeter of claim 11,

the control unit sets a first detection signal intensity of first scattered light included in the first light to be measured as I_S1And setting a first detection signal intensity of first transmitted light included in the first measurement light to I_T1And a second detection signal intensity of second scattered light included in the second measurement target light is represented by I_S2And setting a second detection signal intensity of second transmitted light included in the second measurement light to I_T2Then, the turbidity N is calculated by the following formula 2,

[ formula 2 ]

13. The turbidimeter of claim 8,

the first light source part includes a first LED light source,

the second light source part includes a second LED light source,

the first parameter involved in the turbidity calculation comprises a first drive current of the first LED light source,

the second parameter involved in the turbidity calculation comprises a second drive current of the second LED light source,

the control unit corrects at least one of the first drive current and the second drive current.

14. The turbidimeter of any of claims 8 to 13,

further comprising a third light source unit for irradiating the liquid to be measured with third irradiation light having a third spectrum,

the light receiving unit acquires a detection signal of third measurement light based on the third irradiation light irradiated to the measurement liquid,

the control part is used for controlling the operation of the motor,

correcting a first parameter involved in the calculation of the turbidity associated with the first illumination light, a second parameter involved in the calculation of the turbidity associated with the second illumination light, and a third parameter involved in the calculation of the turbidity associated with the third illumination light,

calculating the turbidity of the liquid to be measured based on the detection signals of the first, second, and third light to be measured.

Technical Field

The present invention relates to a turbidity measuring method and a turbidity meter.

Background

Conventionally, a technique related to a turbidity meter that measures a turbidity level of a liquid to be measured including, for example, water is known.

For example, patent document 1 discloses a turbidimeter capable of accurately measuring suspended matters in a measurement liquid over a wide range from a region of low concentration to a region of high concentration while ensuring linearity over the same unit length and detector arrangement.

Patent document 1: japanese patent laid-open publication No. 2006-329629

In a conventional turbidimeter, for example, a lamp light source that emits white light having a broad band of emission spectrum tends to be used as the light source. When the type of the light source is changed from the conventional turbidimeter as described above, the light source is simply replaced mechanically, and there is a possibility that the turbidity of the liquid to be measured by the conventional turbidimeter does not sufficiently correspond to the turbidity of the liquid to be measured by the turbidimeter after the replacement of the light source.

Disclosure of Invention

An object of the present invention is to provide a turbidity measuring method and a turbidity meter capable of calculating the turbidity of a liquid to be measured so as to correspond to the turbidity of the liquid to be measured using another light source of a conventional turbidity meter.

A turbidity measurement method according to some embodiments is a turbidity measurement method for measuring a turbidity of a measurement target liquid, the turbidity measurement method including: irradiating the measurement liquid with first irradiation light having a first spectrum; acquiring a detection signal of first measurement light based on the first irradiation light irradiated to the measurement liquid; irradiating the measurement liquid with second irradiation light having a second spectrum different from the first spectrum; acquiring a detection signal of second measurement light based on the second irradiation light irradiated to the measurement liquid; calculating the turbidity of the measurement liquid based on the detection signals of the first measurement light and the second measurement light; and correcting at least one of a first parameter relating to calculation of turbidity associated with the first irradiation light and a second parameter relating to calculation of turbidity associated with the second irradiation light so that the turbidity calculated in the step of calculating the turbidity of the liquid to be measured corresponds to the turbidity of the liquid to be measured using another light source as a reference for comparison. According to the turbidity measurement method described above, the turbidity of the liquid to be measured can be calculated so as to correspond to the turbidity of the liquid to be measured using another light source of the conventional turbidity meter. Therefore, even when the user changes the measurement device for measuring the turbidity of the liquid to be measured from, for example, a conventional turbidity meter using a light source to the turbidity meter according to the embodiment using an LED light source, the same measurement result can be obtained for the same liquid to be measured. Therefore, the convenience of the user when updating the measurement device to the turbidimeter according to the embodiment is improved.

In one embodiment, the first parameter relating to the turbidity calculation may include a first detection signal intensity of the first measured light that is detected, the second parameter relating to the turbidity calculation may include a second detection signal intensity of the second measured light that is detected, and at least one of the first detection signal intensity and the second detection signal intensity may be corrected in the correcting step. Thus, the turbidity measurement is performed in a state where detection information based on the detected detection signal is corrected by signal processing. Therefore, by the signal processing described above, the turbidity of the liquid to be measured can be calculated so as to correspond to the turbidity of the liquid to be measured using another light source.

In one embodiment, the step of irradiating the measurement liquid with the first irradiation light and the step of irradiating the measurement liquid with the second irradiation light may be performed at different timings from each other. This makes it possible to independently acquire detection signals of the first light to be measured and the second light to be measured. Therefore, the respective contributions to the detection signal are accurately calculated independently, and the accuracy of the turbidity calculation is improved.

In one embodiment, the first measurement target light and the second measurement target light may include transmitted light transmitted through the measurement target liquid and scattered light scattered by the measurement target liquid, respectively. Thus, the transmitted light/scattered light comparison method can be used, and the turbidity can be calculated with high accuracy over a wider range of turbidity than the case where only either of the transmitted light and the scattered light is used. In addition, even if the variation in the drive current due to the ambient temperature of the turbidimeter or the like differs between the first drive current value of the first LED light source that irradiates the first irradiation light and the second drive current value of the second LED light source that irradiates the second irradiation light, the influence on the turbidity measurement is minimized by adopting the transmitted light/scattered light comparison method.

In one embodiment, in the step of calculating the turbidity of the measurement liquid, if a first detection signal intensity of first scattered light included in the first measurement light is represented by I_S1And setting a first detection signal intensity of first transmitted light included in the first measurement light to I_T1And a second detection signal intensity of second scattered light included in the second measurement target light is represented by I_S2And setting a second detection signal intensity of second transmitted light included in the second measurement light to I_T2The turbidity N is calculated by the following formula 1,

[ formula 1 ]

K is the sensitivity coefficient for turbidity calculation, I_S1(0)Is a first detected signal intensity, I, of the first scattered light obtained for a liquid with a turbidity of 0 DEG_T1(0)Is a first detection signal intensity, I, of the first transmitted light obtained for a liquid having a turbidity of 0 DEG_S2(0)Is obtained for liquid with turbidity of 0 degreeOf the second scattered light, I_T2(0)The second detection signal intensity of the second transmitted light obtained for a liquid having a turbidity of 0 degrees, and α is a correction coefficient, and thus the turbidity of the liquid to be measured can be accurately calculated based on the detection signals of the first and second light to be measured.

In one embodiment, the first parameter related to the turbidity calculation may include a first drive current of a first LED light source that emits the first irradiation light, the second parameter related to the turbidity calculation may include a second drive current of a second LED light source that emits the second irradiation light, and at least one of the first drive current and the second drive current may be corrected in the correcting step. Thus, turbidity measurement is performed in a state where the emission spectrum is optically corrected based on the drive current of the LED light source. Therefore, by the optical processing described above, the turbidity of the liquid to be measured can be calculated so as to correspond to the turbidity of the liquid to be measured using another light source.

The method for measuring turbidity in one embodiment may further comprise the steps of: irradiating the measurement liquid with third irradiation light having a third spectrum; and acquiring a detection signal of third measurement light based on the third irradiation light irradiated to the measurement liquid, and in the step of calculating the turbidity of the measurement liquid, calculating the turbidity of the measurement liquid based on the detection signals of the first measurement light, the second measurement light, and the third measurement light, and in the step of correcting, a first parameter relating to calculation of the turbidity associated with the first irradiation light, a second parameter relating to calculation of the turbidity associated with the second irradiation light, and a third parameter relating to calculation of the turbidity associated with the third irradiation light are corrected. Thus, even when the turbidity of the liquid to be measured is measured using 3 light sources, the turbidity of the liquid to be measured can be calculated so as to correspond to the turbidity of the liquid to be measured using another light source of the conventional turbidity meter. Therefore, when the user changes the measurement device for measuring the turbidity of the liquid to be measured from, for example, a conventional turbidity meter using a light source to the turbidity meter according to the embodiment using an LED light source, the same measurement result can be obtained for the same liquid to be measured. Therefore, the convenience of the user who updates the measurement device to the turbidity meter according to the embodiment is improved.

A turbidity meter according to some embodiments is a turbidity meter for measuring a turbidity of a liquid to be measured, the turbidity meter including: a first light source unit that irradiates the measurement liquid with first irradiation light having a first spectrum; a second light source unit that irradiates the measurement liquid with second irradiation light having a second spectrum different from the first spectrum; a light receiving unit that acquires a detection signal of first measurement light based on the first irradiation light irradiated to the measurement liquid and a detection signal of second measurement light based on the second irradiation light irradiated to the measurement liquid; and a control unit that calculates a turbidity of the liquid to be measured based on the detection signals of the first light to be measured and the second light to be measured, wherein the control unit corrects at least one of a first parameter relating to calculation of a turbidity associated with the first irradiation light and a second parameter relating to calculation of a turbidity associated with the second irradiation light so that the turbidity calculated by the control unit corresponds to a turbidity of the liquid to be measured using another light source that is a reference for comparison. According to the turbidity meter as described above, the turbidity of the liquid to be measured can be calculated so as to correspond to the turbidity of the liquid to be measured using another light source of the conventional turbidity meter. Therefore, even when the user changes the measurement device for measuring the turbidity of the liquid to be measured from, for example, a conventional turbidity meter using a light source to the turbidity meter according to the embodiment using an LED light source, the same measurement result can be obtained for the same liquid to be measured. Therefore, the convenience of the user who updates the measurement device to the turbidity meter according to the embodiment is improved.

In one embodiment, the first parameter related to the turbidity calculation may include a first detection signal intensity of the first light to be measured detected by the light receiving unit, the second parameter related to the turbidity calculation may include a second detection signal intensity of the second light to be measured detected by the light receiving unit, and the control unit may correct at least one of the first detection signal intensity and the second detection signal intensity. Thus, the turbidimeter performs turbidity measurement while correcting detection information based on the detection signal detected by the light receiving unit by signal processing. Therefore, the control unit can calculate the turbidity of the liquid to be measured so as to correspond to the turbidity of the liquid to be measured using another light source by the signal processing described above.

In one embodiment, the control unit may operate the first light source unit and the second light source unit at different timings from each other, and cause the first irradiation light and the second irradiation light to be irradiated at different timings from each other. This makes it possible to independently acquire detection signals of the first light to be measured and the second light to be measured. Therefore, the control unit can accurately calculate the contributions to the detection signals independently, and the accuracy of the turbidity calculation can be improved.

In one embodiment, the first measurement target light and the second measurement target light may include transmitted light transmitted through the measurement target liquid and scattered light scattered by the measurement target liquid, respectively. Thus, the control unit can use the transmitted light/scattered light comparison method, and can calculate the turbidity in a wider range of turbidity with higher accuracy than the case of using only either one of the transmitted light and the scattered light. In addition, even if the variation in the drive current due to the ambient temperature of the turbidimeter or the like differs between the first drive current value of the first LED light source that irradiates the first irradiation light and the second drive current value of the second LED light source that irradiates the second irradiation light, the influence on the turbidity measurement is minimized by adopting the transmitted light/scattered light comparison method.

In one embodiment, the control unit may determine that the first scattering included in the first light to be measured is included in the first light to be measuredThe first detection signal intensity of light is set as I_S1And setting a first detection signal intensity of first transmitted light included in the first measurement light to I_T1And a second detection signal intensity of second scattered light included in the second measurement target light is represented by I_S2And setting a second detection signal intensity of second transmitted light included in the second measurement light to I_T2Then, the turbidity N is calculated by the following formula 2,

[ formula 2 ]

In one embodiment, the first light source unit may include a first LED light source, the second light source unit may include a second LED light source, the first parameter related to the turbidity calculation includes a first drive current of the first LED light source, the second parameter related to the turbidity calculation includes a second drive current of the second LED light source, and the control unit may correct at least one of the first drive current and the second drive current. Thus, the turbidimeter performs turbidity measurement in a state where the emission spectrum is optically corrected based on the drive current of the LED light source. Therefore, the control unit can calculate the turbidity of the liquid to be measured so as to correspond to the turbidity of the liquid to be measured using another light source by the optical processing described above.

The turbidity meter according to one embodiment may further include a third light source unit that irradiates third irradiation light having a third spectrum onto the liquid to be measured, wherein the light receiving unit acquires a detection signal of the third light to be measured based on the third irradiation light irradiated onto the liquid to be measured, and wherein the control unit corrects a first parameter related to calculation of turbidity associated with the first irradiation light, a second parameter related to calculation of turbidity associated with the second irradiation light, and a third parameter related to calculation of turbidity associated with the third irradiation light, and calculates the turbidity of the liquid to be measured based on the detection signals of the first light to be measured, the second light to be measured, and the third light to be measured. Thus, even when the turbidity of the liquid to be measured is measured using 3 light sources, the turbidity of the liquid to be measured can be calculated so as to correspond to the turbidity of the liquid to be measured using another light source of the conventional turbidity meter. Therefore, when the user changes the measurement device for measuring the turbidity of the liquid to be measured from, for example, a conventional turbidity meter using a light source to the turbidity meter according to the embodiment using an LED light source, the same measurement result can be obtained for the same liquid to be measured. Therefore, the convenience of the user in updating the measurement device to the turbidity meter according to the embodiment is improved.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide a turbidity measuring method and a turbidity meter capable of calculating the turbidity of a liquid to be measured so as to correspond to the turbidity of the liquid to be measured using another light source of the conventional turbidity meter.

Drawings

Fig. 1 is a front view showing an appearance of a turbidimeter according to an embodiment.

Fig. 2 is a block diagram showing an example of the configuration of the turbidimeter of fig. 1.

Fig. 3 is a schematic diagram showing an example of a cross section of the optical device of fig. 1.

Fig. 4 is a schematic diagram showing an example of the spectrum of the irradiation light irradiated by each light source.

Fig. 5 is a schematic diagram showing an example of a spectrum of irradiation light emitted from the light source unit of fig. 1.

FIG. 6 is a flowchart showing an example of a turbidity measuring method using the turbidity meter of FIG. 1.

Fig. 7 is a schematic view corresponding to fig. 3 showing a first modification of the turbidimeter according to the embodiment.

Fig. 8 is a schematic view corresponding to fig. 3 showing a second modification of the turbidimeter according to the embodiment.

Fig. 9 is a schematic view corresponding to fig. 3 showing a third modification of the turbidimeter according to the embodiment.

Fig. 10 is a schematic diagram showing an example of a cross section of a conventional turbidimeter using a lamp light source.

Description of the reference numerals

1 turbidimeter

2 optical device

21 measured liquid inlet

22 outlet for measured liquid

23 main body part

24 light source unit

241 first light source unit

242 second light source unit

243 third light source unit

25 light receiving part

251 transmission light detecting part

252 scattered light detection unit

26 condensing lens

27 liquid bath

3 treatment device

31 control part

32 storage part

33 input unit

34 display part

35 communication part

D1 first LED light source

D2 second LED light source

D3 third LED light source

E1 first Spectrum

E2 second Spectrum

E3 third Spectrum

L1 first illumination light

L2 second illumination light

L3 third illumination light

ML1 first measured light

ML2 second measured light

ML3 third measured light

S scattered light

S1 first scattered light

S2 second scattered light

S3 third scattered light

T transmitted light

T1 first transmission light

T2 second transmitted light

T3 third transmitted light

Detailed Description

The turbidity of the liquid to be measured by the turbidity meter is determined by the amount of turbid materials, which are particles present in the liquid to be measured. Several methods are known for determining the amount of turbid substances. For example, in a turbidimeter of the transmitted light/scattered light comparison system, absorption and scattering of irradiation light by a turbid substance in a liquid to be measured are used. When irradiation light is irradiated to a liquid to be measured containing a turbid substance, the transmitted light is weaker as the turbidity is larger due to the absorption of particles. On the other hand, the larger the turbidity, the stronger the scattered light due to scattering by the particles.

Since the light intensity of transmitted light changes logarithmically according to the lambertian beer law, the light intensity of transmitted light becomes very weak at high turbidity. Therefore, it is difficult to measure a liquid to be measured having a high turbidity by using the transmitted light alone. Although the scattered light is theoretically proportional to the turbidity, in actual measurement, the scattered light is affected by absorption in a liquid to be measured having a high turbidity. Therefore, the intensity of the detection signal associated with scattered light is not directly proportional to turbidity. Therefore, in the turbidity meter of the transmitted light/scattered light comparison system, a monotonically increasing relationship between a detection signal value and a turbidity value is created by using a value obtained by dividing the detection signal intensity of scattered light by the detection signal intensity of transmitted light.

A conventional turbidimeter, as shown in fig. 10 for example, includes a lamp light source, a condenser lens, a liquid tank, a transmitted light detector for detecting transmitted light, and a scattered light detector for detecting scattered light. The white light emitted from the lamp light source is collimated by the condenser lens. The white light that becomes parallel light is incident on the liquid tank. The two ends of the liquid groove are separated by transparent glass. For example, in fig. 10, a part of the parallel light is scattered by a turbid substance of the liquid to be measured flowing through the liquid tank from below to above. The scattered light is detected by a scattered light detector disposed at a subsequent stage of the liquid tank. The transmitted light that has passed without being scattered is similarly detected by a transmitted light detector disposed at a subsequent stage of the liquid tank. The turbidity N of the liquid to be measured is obtained by calculating the detected signal intensity of the transmitted light and the detected signal intensity of the scattered light by an arithmetic circuit or the like according to the following expression 3.

[ formula 3 ]

Here, I_TIndicating the intensity of a detection signal of transmitted light transmitted through a liquid to be measured I_SIndicating the detection signal intensity of scattered light scattered by the liquid to be measured. I is_T(0) Indicating the intensity of a detection signal of transmitted light transmitted through a liquid having a turbidity of 0 degree, I_S(0) The intensity of a detection signal indicating scattered light scattered by a liquid having a turbidity of 0 degrees is shown. c is a constant determined by the turbid material in the liquid to be measured and the shape and characteristics of the detection portion, and L is the optical path length of the liquid tank to be measured. As shown in equation 3, ratio I_S/I_TVaries as a function of turbidity N.

In a conventional turbidimeter, for example, a lamp light source that emits white light having a broad band of emission spectrum tends to be used as a light source. The light source of the lamp has the defects that the filament is easy to break and the service life is short. In addition, the lamp light source has a disadvantage that it consumes a large amount of electric power and easily generates heat, and therefore dew condensation is easily generated on the transparent glass of the liquid tank. If dew condensation occurs on the transparent glass in the liquid tank, the dew condensation may cause further scattering of light, and thus the measurement accuracy of the turbidity of the liquid to be measured may be lowered.

In order to solve the above-described problems, an led (light Emitting diode) light source may be used as the light source. As an example of a conventional LED used for a light source of a turbidimeter, a monochromatic LED is known. The spectrum of the irradiation light generated by the monochromatic LED light source as described above has a half-value width of several nm to several tens of nm, for example, in a visible region or a near infrared region of 1000nm or less. Here, the near-infrared region represents a predetermined wavelength region on the longer wavelength side than the visible region, and includes a wavelength region relatively close to the visible region among infrared regions described later. For example, the near infrared region includes a wavelength region of 780nm to 2000 nm. The wavelength band and the spectral intensity of the emission spectrum of the monochromatic LED light source are significantly different from those of the conventional lamp light source. For example, the spectrum of the illumination light generated by the lamp light source has a peak in the infrared region, unlike a monochromatic LED light source, and the wavelength band covers the entire visible region. Here, the infrared region represents a predetermined wavelength region on a longer wavelength side than the visible region, and includes, for example, a predetermined wavelength region having a wavelength longer than 780 nm.

As another example of conventional LEDs used as a light source of a turbidimeter, a white LED or a light-adjusting/color-mixing LED is known, which uses a fluorescent material or the like and makes the appearance of irradiation light close to sunlight, light of a fluorescent lamp, light of a lamp light source, or the like. The illumination light produced by these LED light sources can be seen in the human eye as similar to illumination light from a lamp light source. However, the emission spectrum of these LED light sources discontinuously has a plurality of peaks in the visible region, and is significantly different from the emission spectrum of a lamp light source in which the spectral intensity continuously changes in the visible region.

The conventional LED light source as described above has high versatility, but has a great difference from a lamp light source with respect to wavelength characteristics. Therefore, in the turbidity measurement of the liquid to be measured, the light source of the lamp may be replaced with the conventional LED light source, and the turbidity detection sensitivity may be reduced. That is, in a liquid to be measured other than the standard liquid, there is a possibility that the turbidity measured by the turbidity meter having the lamp light source and the turbidity measured by the turbidity meter having the LED light source may not match each other. This is because, if the wavelength characteristics of the light source used are different, the scattering angle distribution and the absorption characteristics of the turbid material contained in the liquid to be measured or the liquid to be measured itself may be different, and the detected scattered light intensity and transmitted light intensity may change. Here, the standard solution contains a liquid having a known turbidity value, which contains a prescribed turbidity standard substance specified in accordance with a prescribed turbidity standard.

In order to solve the above-described problems, it is an object of the present invention to provide a turbidity measuring method and a turbidity meter capable of calculating the turbidity of a liquid to be measured using an LED light source so as to correspond to the turbidity of the liquid to be measured using another light source, more specifically, a lighting light source in a conventional turbidity meter.

Hereinafter, an embodiment of the present invention will be mainly described with reference to the drawings.

Fig. 1 is a front view showing an appearance of a turbidimeter 1 according to an embodiment.

The turbidimeter 1 according to one embodiment is a turbidimeter of a transmitted light/scattered light comparison system, as an example. The turbidity meter 1 measures the turbidity of a liquid to be measured. The turbidimeter 1 includes, as large components, an optical device 2 and a processing device 3. The optical device 2 irradiates irradiation light to the liquid to be measured passing through the inside, and detects the transmitted light T and the scattered light S based on the irradiation light. The processing device 3 is connected to the optical device 2, and acquires a detection signal based on the transmitted light T and the scattered light S detected by the optical device 2 from the optical device 2. The processing device 3 executes a process of calculating the turbidity of the liquid to be measured based on the detection signal acquired from the optical device 2, or the like, or executes control of the optical device 2.

The optical device 2 includes: a measurement-target-liquid inlet 21 into which a measurement target liquid flowing from below in fig. 1 flows; and a measurement liquid outlet 22 for allowing the measurement liquid flowing into the optical device 2 from the measurement liquid inlet 21 to flow out to the outside. The optical device 2 includes a main body 23, a light source 24, and a light receiver 25. The body 23 includes a liquid tank for guiding the liquid to be measured flowing upward from below. The liquid tank of the body 23 is sandwiched between the light source unit 24 and the light receiving unit 25 in a direction intersecting the direction in which the liquid to be measured flows.

Fig. 2 is a block diagram showing an example of the configuration of the turbidimeter 1 of fig. 1.

The light source unit 24 included in the optical device 2 includes a first light source unit 241 and a second light source unit 242.

The first light source unit 241 irradiates the liquid to be measured with first irradiation light L1 having a first spectrum E1 described later. The first light source unit 241 has an arbitrary light source capable of emitting the first irradiation light L1. For example, the first light source portion 241 includes a first LED light source D1.

The second light source unit 242 irradiates the liquid to be measured with second irradiation light L2 having a second spectrum E2 described later, which is different from the first spectrum E1. The second light source unit 242 has an arbitrary light source capable of emitting the second irradiation light L2. For example, the second light source section 242 includes a second LED light source D2.

The light receiving unit 25 included in the optical device 2 acquires detection signals of the first light for measurement ML1 based on the first irradiation light L1 irradiated with respect to the liquid to be measured and the second light for measurement ML2 based on the second irradiation light L2 irradiated with respect to the liquid to be measured. The light receiving unit 25 outputs the detection current or the detection voltage as detection signals of the first light to be measured ML1 and the second light to be measured ML 2. The intensity of the output detection signal corresponds to the light intensity of the light to be measured detected by the light receiving unit 25. When the turbidimeter 1 is of the transmitted light/scattered light comparison method, the first measurement light ML1 includes the first transmitted light T1 transmitted through the measurement liquid and the first scattered light S1 scattered by the measurement liquid. Similarly, the second measurement light ML2 includes the second transmitted light T2 transmitted through the measurement liquid and the second scattered light S2 scattered by the measurement liquid.

The light receiving unit 25 includes a transmitted light detection unit 251 and a scattered light detection unit 252.

The transmitted light detector 251 detects the first transmitted light T1 based on the first irradiation light L1 and the second transmitted light T2 based on the second irradiation light L2. The transmitted light detection unit 251 includes any photodetector capable of detecting the first transmitted light T1 and the second transmitted light T2. For example, the transmitted light detection unit 251 includes a photodiode. The wavelength band of the photodiode constituting the transmitted light detection unit 251 includes the wavelength band of the spectrum of the first transmitted light T1 and the second transmitted light T2.

The scattered light detector 252 detects the first scattered light S1 based on the first irradiation light L1 and the second scattered light S2 based on the second irradiation light L2. The scattered light detector 252 includes an arbitrary photodetector capable of detecting the first scattered light S1 and the second scattered light S2. For example, the scattered light detection section 252 includes a photodiode. The wavelength band of the photodiode constituting the scattered light detection unit 252 includes the wavelength band of the spectrum of the first scattered light S1 and the second scattered light S2.

The processing device 3 includes a control unit 31, a storage unit 32, an input unit 33, a display unit 34, and a communication unit 35.

The control unit 31 includes 1 or more processors. For example, the control unit 31 includes a processor capable of performing processing related to the turbidimeter 1. The control unit 31 is connected to each of the components constituting the turbidity meter 1, and controls and manages the entire turbidity meter 1, as represented by each of the components. For example, the control unit 31 controls the driving current of the LED light sources included in the first light source unit 241 and the second light source unit 242. For example, the control unit 31 calculates the turbidity of the liquid to be measured based on the detection signals of the first light to be measured ML1 and the second light to be measured ML2 output from the optical device 2. In addition, the control unit 31 calculates parameters necessary for calculating the turbidity of the liquid to be measured, for example.

The storage unit 32 includes any storage devices such as hdd (hard Disk drive), ssd (solid State drive), EEPROM (Electrically Erasable Programmable Read-Only Memory), ROM (Read-Only Memory), and ram (random Access Memory), and stores information necessary for realizing the operation of the turbidimeter 1. The storage section 32 may function as a main storage, an auxiliary storage, or a cache memory. The storage unit 32 is not limited to being built in the turbidity meter 1, and may be an external storage device connected via a digital input/output port or the like, such as a USB. The storage unit 32 stores various information calculated by the control unit 31, for example. The storage unit 32 stores, for example, detection information based on detection signals of the first light to be measured ML1 and the second light to be measured ML2 output from the optical device 2.

The input unit 33 includes an arbitrary input interface that receives an input operation by the user of the turbidimeter 1. The input unit 33 receives an input operation by the user of the turbidimeter 1, and acquires input information input by the user. The input unit 33 outputs the acquired input information to the control unit 31. For example, the user inputs arbitrary information necessary for realizing the operation of the turbidity meter 1 using the input unit 33.

The display unit 34 includes an arbitrary output interface for outputting an image. The display unit 34 includes, for example, a liquid crystal display. The display unit 34 displays various information calculated by the control unit 31, for example, for the user of the turbidimeter 1. The display unit 34 displays, for example, a setting screen required for the user to input arbitrary information for realizing the operation of the turbidity meter 1 for the user.

The communication unit 35 includes an arbitrary communication interface corresponding to an arbitrary communication protocol by wire or wireless. The communication unit 35 can transmit various information calculated by the control unit 31 to any external device. The communication unit 35 may receive arbitrary information necessary for realizing the operation of the turbidimeter 1 from an arbitrary external device. For example, the communication unit 35 may receive a control signal for controlling the optical device 2 from any external device.

Fig. 3 is a schematic diagram showing an example of a cross section of the optical device 2 of fig. 1. The operation of the optical system of the turbidimeter 1 will be mainly described with reference to fig. 3.

The irradiation light emitted from the light source unit 24 including the first light source unit 241 and the second light source unit 242 is collimated by the condenser lens 26. The irradiation light as parallel light is incident on the liquid tank 27. The liquid bath 27 is partitioned at both ends by transparent glass. The liquid tank 27 is configured to flow the liquid to be measured, for example, from the lower side toward the upper side of the figure. The light receiving section 25 is disposed on the opposite side of the liquid tank 27 from the light source section 24.

The transmitted light T transmitted through the liquid to be measured in the liquid tank 27 is detected by, for example, a transmitted light detection unit 251 disposed to face the light source unit 24 with the liquid tank 27 interposed therebetween. Of the scattered light S scattered by the turbid substance of the liquid to be measured flowing in the liquid tank 27, the scattered light S having a predetermined angle with respect to the transmitted light T as the parallel light is detected by, for example, the scattered light detection units 252 disposed above and below the transmitted light detection unit 251. The number of photodetectors constituting the scattered light detection unit 252 is not limited to 2, and may be 1 or 3 or more. The control unit 31 detects the signal intensity I based on the transmitted light T detected by the light receiving unit 25_TAnd the intensity of the detection signal I of the scattered light S_SAccording to I_S/I_TThe turbidity N is calculated by performing the ratio calculation in this way.

Fig. 4 is a schematic diagram showing an example of the spectrum of the irradiation light irradiated by each light source. Referring to fig. 4, the emission spectra of the conventional lighting light source, the first LED light source D1 included in the first light source section 241, and the second LED light source D2 included in the second light source section 242 will be described by comparison.

In fig. 4, the emission spectrum of the conventional lighting source is shown by a solid line. In fig. 4, the emission spectrum of the conventional lamp light source includes a peak appearing in the infrared region, and the illustration of the corresponding emission spectrum on the longer wavelength side than the wavelength around 800nm is omitted. That is, fig. 4 illustrates only the emission spectrum of the conventional lighting source, which corresponds to the emission spectrum on the shorter wavelength side than the wavelength around 800 nm. In fig. 4, a first spectrum E1 of the first irradiation light L1 of the first LED light source D1 and a second spectrum E2 of the second irradiation light L2 of the second LED light source D2 are indicated by broken lines.

In the turbidimeter 1 according to the embodiment, the same wavelength characteristics as those of the conventional lamp light source are realized based on the first spectrum E1 of the first irradiation light L1 and the second spectrum E2 of the second irradiation light L2.

More specifically, the first spectrum E1 of the first irradiation light L1 irradiated by the first LED light source D1 substantially corresponds to the light emission spectrum of the lamp light source in the visible region. That is, first spectrum E1 rises from around wavelength 400nm, similarly to the emission spectrum of the lamp light source, and extends over substantially the entire visible region. As described above, the first LED light source D1 has the same wavelength characteristics as those of the lamp light source in the visible region. However, in the near infrared region of 780nm or more, the spectral intensity of the first spectrum E1 decreases, and the first LED light source D1 has a wavelength characteristic different from that of the lamp light source.

The second LED light source D2 compensates for the decrease in the spectral intensity in the near-infrared region of the first LED light source D1, and makes the spectral intensity of the light source unit 24 in this region correspond to the spectral intensity of the lighting light source. That is, the second spectrum E2 has a peak corresponding to the spectral intensity of the lamp light source in the near infrared region and extends with a predetermined half-value width. Further, the emission spectrum of the conventional lighting source also has a predetermined spectral intensity on the longer wavelength side than the region where the second spectrum E2 is spread. However, conventionally, a photodetector having sensitivity at a predetermined wavelength or less in the near infrared region is used, and the same photodetector is used in the light receiving unit 25, so that the influence on the turbidity measurement by the emission spectrum of the lamp light source can be ignored on the longer wavelength side than the predetermined wavelength.

The first LED light source D1 includes a phosphor and an excitation LED for exciting the phosphor so as to emit first irradiation light L1 having a first spectrum E1 as shown in fig. 4. In this case, the peak of the emission spectrum of the excitation LED appears in, for example, the ultraviolet region. Here, the ultraviolet region indicates a predetermined wavelength region on a shorter wavelength side than the visible region, and includes, for example, a predetermined wavelength region having a wavelength shorter than 380 nm. On the other hand, the spectral intensity of a conventional lighting source is substantially zero in the ultraviolet region. In the turbidimeter 1 according to the embodiment, in order to realize the same wavelength characteristics as those of the conventional lamp light source, the peak in the ultraviolet region as described above may be suppressed. Therefore, the first LED light source D1 may have any optical filter that is disposed on the optical path of the excitation LED and suppresses the peak of the excitation LED.

The first LED light source D1 may also have a plurality of single-color LEDs having emission wavelengths different from each other in a wavelength region over which the first spectrum E1 extends, in addition to or instead of an optical filter for suppressing peaks in the ultraviolet region. Accordingly, the spectral intensity of the first spectrum E1, which extends in the visible region, is added to the spectral intensities of the plurality of single-color LEDs, and accordingly, the spectral intensity is sufficiently larger than the spectral intensity of the excitation LED in the ultraviolet region. Therefore, the peak of the excitation LED in the ultraviolet region is relatively lowered with respect to the first spectrum E1. As a result, the peak of the excitation LED in the ultraviolet region is relatively suppressed.

The first LED light source D1 may have a structure related to a phosphor that improves excitation efficiency, i.e., energy efficiency, achieved by the excitation LED in addition to or instead of the above-described structure for suppressing a peak in the ultraviolet region. More specifically, the first LED light source D1 may have a phosphor optimized in at least one of type and optical density. For example, although the half width is slightly smaller than the first spectrum E1 shown in fig. 4, a phosphor having a sufficiently low peak value of the excitation LED may be selected as the phosphor of the first LED light source D1. For example, a phosphor having such an optical density that excitation light from the excitation LED is sufficiently absorbed in the phosphor may be selected as the phosphor of the first LED light source D1. As described above, since the first LED light source D1 has a phosphor with improved energy efficiency, the peak of the excitation LED in the ultraviolet region is relatively lowered with respect to the first spectrum E1. In addition, the excitation LED can be caused to emit light not in the ultraviolet region but in the visible region. Therefore, any optical filter for suppressing the peak of the exciting LED can be omitted.

The second LED light source D2 has a single-color LED that emits light in the near-infrared region in order to radiate second irradiation light L2 having a second spectrum E2 as shown in fig. 4. The structure for increasing the emission intensity from the light source unit 24 in the near infrared region is not limited to this. The light source unit 24 may include a phosphor of the first LED light source D1, to which a phosphor for increasing the emission intensity in the near infrared region is added, in addition to or instead of the single-color LED of the second LED light source D2. When the light source section 24 includes the phosphor as described above in place of the single-color LED included in the second LED light source D2, the first light source section 241 and the second light source section 242 share the phosphor.

For example, in the case where different LEDs are used between the first LED light source D1 and the second LED light source D2 as described above, the light intensity of the irradiation light is generally different for each LED. Therefore, in the turbidity measurement, the above-described difference between the first LED light source D1 and the second LED light source D2 needs to be considered.

Therefore, the control unit 31 corrects at least one of the first parameter relating to the calculation of the turbidity associated with the first irradiation light L1 and the second parameter relating to the calculation of the turbidity associated with the second irradiation light L2 so that the turbidity calculated by the control unit 31 using the light source unit 24 described above corresponds to the turbidity of the liquid to be measured using the light source of the lamp light which is another light source as a reference for comparison. Next, 2 examples of the above-described correction method will be described.

In the first example of the calibration method, the first parameter relating to the turbidity calculation includes the first detection signal intensity of the first light to be measured ML1 detected by the light receiving unit 25, and the second parameter relating to the turbidity calculation includes the second detection signal intensity of the second light to be measured ML2 detected by the light receiving unit 25. At this time, the control unit 31 corrects at least one of the first detection signal intensity and the second detection signal intensity so that the turbidity calculated by the control unit 31 corresponds to the turbidity of the liquid to be measured using the lamp light source. As described above, in the first example of the calibration method, the turbidimeter 1 can perform turbidity measurement in a state where detection information based on the detection signal detected by the light receiving unit 25 is calibrated by, for example, signal processing.

In the first example of the calibration method, the controller 31 operates the first LED light source D1 and the second LED light source D2 at different timings to cause the first irradiation light L1 and the second irradiation light L2 to irradiate at different timings to execute the signal processing described above. For example, the controller 31 alternately operates either the first LED light source D1 or the second LED light source D2 to alternately irradiate either the first irradiation light L1 or the second irradiation light L2. I represents a first detection signal intensity of the first scattered light S1 obtained when only the first LED light source D1 emits light with respect to the liquid to be measured_S1And the first detection signal intensity of the first transmitted light T1 is I_T1I represents a second detection signal intensity of the second scattered light S2 obtained when only the second LED light source D2 emits light with respect to the liquid to be measured_S2And the second detection signal intensity of the second transmitted light T2 is I_T2. At this time, the control unit 31 calculates the turbidity N based on the following expression 4.

[ formula 4 ]

In equation 4, K is a sensitivity coefficient for calculating turbidity, which indicates an inclination when the first light to be measured ML1 and the second light to be measured ML2 are measured at 2 known turbidities N using a liquid having a turbidity of 0 degrees and a standard liquid. The sensitivity coefficient being for dividing the ratio I_S/I_TThe sensitivity coefficient K can be calculated based on the actually measured detection signal intensities, the known turbidity N, and a correction coefficient α described later.

I_S1(0)A first detection signal intensity of the first scattered light S1 obtained when only the first LED light source D1 was turned on for a liquid having a turbidity of 0 degrees is shown. I is_T1(0)The first detection signal intensity of the first transmitted light T1 obtained when only the first LED light source D1 was turned on for a liquid having a turbidity of 0 degrees is shown.I_S2(0)And a second detection signal intensity of the second scattered light S2 obtained when only the second LED light source D2 was turned on for a liquid having a turbidity of 0 degrees. I is_T2(0)And a second detection signal intensity of the second transmitted light T2 obtained when only the second LED light source D2 is turned on for a liquid having a turbidity of 0 degrees.

α is a correction coefficient for the purpose of making the contribution ratio of the first LED light source D1 and the second LED light source D2 to the turbidity measurement closer to that of the conventional lighting light source. More specifically, the correction coefficient α is calculated in the following order for each group of the first LED light source D1 and the second LED light source D2.

Fig. 5 is a schematic diagram showing an example of a spectrum of the irradiation light emitted from the light source unit 24 in fig. 1. The calculation procedure of the correction coefficient α will be mainly described with reference to fig. 5. In the following first and second procedures for calculating the correction coefficient α, the controller 31 adjusts at least one of the first drive current and the second drive current so that the ratio of the first spectral intensity P1 at the first peak wavelength of the first spectrum E1 and the second spectral intensity P2 at the second peak wavelength of the second spectrum E2 is the same as the ratio of the spectral intensity a at the first peak wavelength and the spectral intensity B at the second peak wavelength in the emission spectrum of the lamp light source shown in fig. 4.

The control unit 31 obtains in advance, by an arbitrary method, a spectral intensity a at the first peak wavelength and a spectral intensity B at the second peak wavelength in the emission spectrum of the lamp light source serving as a reference, which are measured by, for example, a light spectrum analyzer or the like, which is another device different from the turbidimeter 1. In the first procedure of calculating the correction coefficient α, the control unit 31 calculates the ratio B/a based on the acquired spectral intensity A, B.

In the second procedure of calculating the correction coefficient α, the controller 31 obtains, by an arbitrary method, the first spectral intensity P1 and the second spectral intensity P2 measured by the optical spectrum analyzer or the like in a state where the first LED light source D1 and the second LED light source D2 are simultaneously emitting light. At this time, the controller 31 can independently adjust the first driving current of the first LED light source D1 and the second driving current of the second LED light source D2. The controller 31 adjusts the second drive current of the second LED light source D2, for example, and determines a drive current value at which the second spectral intensity P2 satisfies the following equation 5.

[ FORMULA 5 ]

The controller 31 stores the first driving current value C1 of the first LED light source D1 and the second driving current value C2 of the second LED light source D2 in the storage unit 32.

In the above-described specific example, it has been described that the controller 31 adjusts only the second drive current of the second LED light source D2 so that the ratio of the first spectral intensity P1 to the second spectral intensity P2 is the same as the ratio of the spectral intensity a to the spectral intensity B. At this time, the controller 31 may or may not adjust the first driving current of the first LED light source D1 so that the first spectral intensity P1 matches the spectral intensity a.

When the first drive current is adjusted, the absolute values of the first spectral intensity P1 and the second spectral intensity P2 match the corresponding spectral intensities in the emission spectrum of the lamp light source. Therefore, the turbidity meter 1 according to the embodiment can use the same detection circuit as that of the conventional turbidity meter using the lamp light source, and the compatibility between the conventional turbidity meter and the turbidity meter 1 according to the embodiment is improved.

Without adjusting the first drive current, the first spectral intensity P1 typically does not coincide with the spectral intensity a. In the above case, the control unit 31 is also according to I_S/I_TSince the ratio calculation is performed in this way, the influence of the difference between the absolute value of the emission spectrum of the light source unit 24 and the absolute value of the emission spectrum of the lamp light source is cancelled out between the denominator and the numerator. Therefore, even if there is a difference in absolute values between them, the measured turbidity sufficiently corresponds in each case.

In the third procedure of calculating the correction coefficient α, the controller 31 adjusts, for example, the first drive current of the first LED light source D1 and the second drive current of the second LED light source D2 independently of each other so that the ratio of the first drive current value C1 to the second drive current value C2 recorded in the storage unit 32 is the same ratio under factory conditions where the ambient environment such as temperature and humidity is always constant. In this case, the adjusted first and second driving currents may have the same values as the first and second driving current values C1 and C2, respectively, and the first and second driving current values C1 and C2 may have different values as long as the driving current and the light emission intensity of each LED light source are in a linear range.

The controller 31 causes the first LED light source D1 and the second LED light source D2 to independently emit light at different timings based on the adjusted first drive current and second drive current, respectively, with respect to the liquid tank 27 filled with the liquid having a turbidity of 0 degrees. The controller 31 controls the first detection signal intensity I of the first transmitted light T1 when the first LED light source D1 and the second LED light source D2 emit light_T1bAnd a second detection signal intensity I of the second transmitted light T2_T2bAnd stored in the storage unit 32.

In the 4 th order of calculating the correction coefficient α, the control unit 31 causes the first LED light source D1 and the second LED light source D2 attached to the turbidimeter 1 to independently emit light at different timings with arbitrary first and second drive currents according to the actual usage situation of the user, for example, at the time when the liquid tank 27 is filled with a liquid having a turbidity of 0 degree, the control unit 31 causes the first detection signal intensity I of the first transmitted light T1 to emit light when the first LED light source D1 and the second LED light source D2 emit light, respectively_T1iAnd a second detection signal intensity I of the second transmitted light T2_T2iAnd stored in the storage unit 32.

The control unit 31 calculates the correction coefficient α based on the following equation 6.

[ formula 6 ]

The control unit 31 stores the correction coefficient α calculated as described above in the storage unit 32. The controller 31 alternately operates either the first LED light source D1 or the second LED light source D2 at the first drive current and the second drive current set in accordance with the actual usage situation of the user. Thus, the control unit 31 can calculate the turbidity N of the liquid to be measured based on equation 4 using the correction coefficient α stored in advance in the storage unit 32. In this case, the turbidity meter 1 may not have a function for adjusting each driving current. Further, the correction coefficient α may be calculated in an initial correction stage before product shipment as described above, and then periodically updated by a user or the like.

By the processing realized by the control unit 31 as described above, at least one of the first detection signal intensity and the second detection signal intensity is corrected, and the turbidity of the liquid to be measured calculated by the control unit 31 corresponds to the turbidity measured by using the lamp light source.

The following mainly describes a second example of the correction method.

For example, the turbidimeter 1 may perform turbidity measurement in a state where the emission spectrum is optically corrected based on the drive current of the LED light source, instead of the first example of the correction method described above.

In the second example of the calibration method, the first parameter relating to the turbidity calculation includes the first drive current of the first LED light source D1, and the second parameter relating to the turbidity calculation includes the second drive current of the second LED light source D2. At this time, the control unit 31 corrects at least one of the first drive current and the second drive current so that the turbidity calculated by the control unit 31 corresponds to the turbidity of the liquid to be measured using the light source.

More specifically, the controller 31 corrects at least one of the first drive current and the second drive current so that the ratio of the first spectral intensity P1 at the first peak wavelength of the first spectrum E1 and the second spectral intensity P2 at the second peak wavelength of the second spectrum E2 shown in fig. 5 is the same as the ratio of the spectral intensity a at the first peak wavelength and the spectral intensity B at the second peak wavelength in the emission spectrum of the lamp light source shown in fig. 4.

More specifically, the controller 31 stores the first drive current value C1 of the first LED light source D1 and the second drive current value C2 of the second LED light source D2 in the storage unit 32 in the same order as the first and second orders of calculating the correction coefficient α described in the first example of the correction method.

The controller 31 causes the first LED light source D1 and the second LED light source D2 to emit light at the first drive current value C1 and the second drive current value C2 stored in the storage unit 32, respectively, for example, and calculates the turbidity of the liquid to be measured. At this time, the control unit 31 may calculate the turbidity N based on the following equation 7 when the correction coefficient α is set to 1 in equation 4, for example.

[ formula 7 ]

That is, the controller 31 may calculate the turbidity N by independently emitting the first LED light source D1 and the second LED light source D2 at different timings based on the first drive current value C1 and the second drive current value C2. The controller 31 may calculate the turbidity N by causing the first LED light source D1 and the second LED light source D2 to emit light at the same time based on the first drive current value C1 and the second drive current value C2. In this case, the controller 31 may use equation 3, for example, as in the conventional turbidity measurement using a lamp light source, and may use the ratio I of the detection signal intensities based on the transmitted light T and the scattered light S of the irradiation light_S/I_TThe turbidity N is calculated.

As described above, by causing the first LED light source D1 and the second LED light source D2 to emit light at different drive currents using the first drive current value C1 and the second drive current value C2, the control unit 31 can perform correction so that the light emission spectrum of the light source unit 24 sufficiently corresponds to the light emission spectrum of the lamp light source.

When the first irradiation light L1 and the second irradiation light L2 are simultaneously emitted from the light source unit 24, the spectrum of the entire irradiation light has a spectrum whose spectral intensity is continuously changed by combining the first spectrum E1 and the second spectrum E2, unlike the conventional white LED or light-adjusting/color-mixing LED that discontinuously has a plurality of peaks in the visible region.

With the above-described configuration of the light source unit 24, the correspondence between the emission spectrum of the light source unit 24 and the emission spectrum of the conventional lighting source becomes good. Thus, in the turbidity measurement using the LED, the light intensities of the transmitted light T transmitted through the liquid to be measured and the scattered light S scattered by the liquid to be measured in the predetermined wavelength range sufficiently correspond to the light intensity in the case of using the conventional lamp light source. Therefore, the turbidity of the liquid to be measured using both of them sufficiently corresponds to each other.

Fig. 6 is a flowchart showing an example of a turbidity measuring method using the turbidity meter 1 of fig. 1. An example of the flow of the turbidity measurement of the liquid to be measured performed by the control unit 31 of the turbidity meter 1 according to the first embodiment will be mainly described with reference to fig. 6.

In step S101, the controller 31 turns on the first LED light source D1 and irradiates the liquid to be measured with the first irradiation light L1 having the first spectrum E1.

In step S102, the control unit 31 detects the first light for measurement ML1 based on the first irradiation light L1 emitted to the liquid for measurement in step S101.

In step S103, the control unit 31 sets the first detection signal intensity I of the first scattered light S1 based on the first light to be measured ML1 detected in step S102_S1And a first detection signal intensity I of the first transmitted light T1_T1And stored in the storage unit 32.

In step S104, the controller 31 turns off the first LED light source D1 and turns off the first irradiation light L1.

In step S105, the controller 31 turns on the second LED light source D2 and irradiates the liquid to be measured with the second irradiation light L2 having the second spectrum E2 different from the first spectrum E1.

In step S106, the control unit 31 detects the second measurement light ML2 based on the second irradiation light L2 emitted to the measurement target liquid in step S105.

In step S107, the control unit 31 scatters the second measurement target light ML2 based on the second measurement target light ML2 detected in step S106Second detection signal intensity I of light S2_S2And a second detection signal intensity I of the second transmitted light T2_T2And stored in the storage unit 32.

In step S108, the controller 31 turns off the second LED light source D2 and turns off the second irradiation light L2.

In step S109, the control unit 31 controls the memory unit 32 based on I stored in step S103_S1And I_T1And I stored in the storage section 32 in step S107_S2And I_T2The turbidity N of the liquid to be measured is calculated using, for example, equation 4.

In step S110, the control unit 31 determines whether or not the number of data acquisitions has reached a predetermined value set by the user using the input unit 33, for example. If the control unit 31 determines that the number of data acquisitions has not reached the predetermined value, it executes the processing of step S101 to step S109 again. If the control unit 31 determines that the number of data acquisitions has reached the predetermined value, the process is terminated.

In the case of the first example of the above-described correction method, the control unit 31 calculates the correction coefficient α and stores it in the storage unit 32, for example, before step S101 in fig. 6. When calculating the turbidity N of the liquid to be measured in step S109, the control unit 31 corrects at least one of the first detection signal intensity and the second detection signal intensity based on the correction coefficient α stored in advance in the storage unit 32.

In the case of the second example based on the above-described correction method, for example, before step S101 in fig. 6, the control unit 31 determines the first drive current value C1 and the second drive current value C2, and corrects at least one of the corresponding first drive current and second drive current.

In the flow shown in FIG. 6, one cycle from step S101 to step S109 is, for example, about 1 to 2 seconds. The control unit 31 may average the turbidity N calculated for each cycle in step S109 over a range of a plurality of cycles.

In the turbidity meter 1 according to the embodiment, the control unit 31 corrects at least one of the first parameter relating to the calculation of the turbidity associated with the first irradiation light L1 and the second parameter relating to the calculation of the turbidity associated with the second irradiation light L2 so that the turbidity calculated by the control unit 31 corresponds to the turbidity of the liquid to be measured using another light source as a reference for comparison. According to the turbidity meter 1 of the above-described one embodiment, the turbidity of the liquid to be measured can be calculated so as to correspond to the turbidity of the liquid to be measured using another light source of the conventional turbidity meter. Therefore, even when the user changes the measurement device for measuring the turbidity of the liquid to be measured from, for example, a conventional turbidity meter using a light source to the turbidity meter 1 according to the embodiment using an LED light source, the same measurement result can be obtained for the same liquid to be measured. Therefore, the convenience of the user when updating the measurement device to the turbidimeter 1 according to the embodiment is improved.

It is obvious to those skilled in the art that the present invention can be implemented in other predetermined forms than the above-described embodiments without departing from the spirit or essential characteristics thereof. Therefore, the above description is illustrative, and not restrictive. The scope of the invention is defined not by the above description but by the claims. All changes, including variations within the scope and range of equivalents thereof, are encompassed by the present invention.

For example, the shape, arrangement, orientation, number, and the like of the above-described components are not limited to those illustrated in the above description and drawings. The shape, arrangement, orientation, number, and the like of each component may be arbitrarily configured if the functions thereof can be realized.

For example, each step and functions included in each step in the measurement method using the turbidimeter 1 can be rearranged in a logically non-contradictory manner, and the order of the steps can be changed, or a plurality of steps can be combined into 1 or divided.

For example, the present invention can be realized as a program describing the processing contents for realizing the functions of the turbidity meter 1 or a storage medium storing the program. These are intended to be included within the scope of the present invention.

In the first example of the correction method, the control unit 31 alternately irradiates either the first irradiation light L1 or the second irradiation light L2, but the control method implemented by the control unit 31 is not limited to this. For example, if the controller 31 can independently calculate the detection signal intensities based on the first irradiation light L1 and the second irradiation light L2 by optical processing, signal processing, or the like, the controller 31 may simultaneously irradiate the first irradiation light L1 and the second irradiation light L2. At this time, the control unit 31 may calculate the turbidity N based on the above equation 4.

In the above description, the turbidimeter 1 is a turbidimeter of the transmission light/scattered light comparison system as shown in fig. 3, but the turbidimeter is not limited thereto. Fig. 7 is a schematic diagram corresponding to fig. 3 showing a first modification of the turbidity meter 1 according to the embodiment. As shown in fig. 7, the turbidimeter 1 may be a transmission type turbidimeter that measures turbidity using only absorbance. Fig. 8 is a schematic diagram corresponding to fig. 3 showing a second modification of the turbidity meter 1 according to the embodiment. As shown in fig. 8, the turbidimeter 1 may be a scattered light type turbidimeter. Fig. 9 is a schematic diagram corresponding to fig. 3 showing a third modification of the turbidity meter 1 according to the embodiment. As shown in fig. 9, the turbidimeter 1 may be a surface scattering light type turbidimeter.

In the above, the second LED light source D2 has been described as having only 1 single-color LED emitting light in the near infrared region, but is not limited thereto. The light source unit 24 may include a plurality of monochromatic LEDs having different emission wavelengths in a region where the spectral intensity of the first spectrum E1 decreases, so that the spectrum of the irradiation light irradiated from the light source unit 24 more closely approximates the emission spectrum of the lamp light source.

For example, the light source unit 24 may further include a third light source unit 243 for irradiating the liquid to be measured with third irradiation light L3 having a third spectrum E3. The third light source unit 243 has an arbitrary light source capable of emitting third irradiation light L3. For example, the third light source section 243 includes a third LED light source D3. The third LED light source D3 may have 1 single color LED emitting light in the near infrared region.

At this time, the controller 31 operates the first LED light source D1, the second LED light source D2, and the third LED light source D3 at different timings from each other, and irradiates the third irradiation light L3 with the first irradiation light L1 and the second irradiation light L2 at different timings from each other. The light receiving unit 25 also acquires a detection signal of the third light for measurement ML3 based on the third irradiation light L3 irradiated to the liquid for measurement.

The controller 31 corrects the first parameter related to the calculation of the turbidity of the first irradiation light L1, the second parameter related to the calculation of the turbidity of the second irradiation light L2, and the third parameter related to the calculation of the turbidity of the third irradiation light L3 by the same method as the first and second examples of the correction method described above. The control unit 31 calculates the turbidity of the liquid to be measured based on the detection signals of the first, second, and third light to be measured ML1, ML2, and ML 3. Here, in the first example of the calibration method, the third parameter relating to the turbidity calculation includes the third detection signal intensity of the third light ML3 to be measured detected by the light receiving unit 25. In a second example of the correction method, the third parameter relating to the turbidity calculation includes the third drive current of the third LED light source D3.

For example, a first example of the above-described correction method in the case of using 3 light sources will be described. I represents a third detection signal intensity of the third scattered light S3 obtained when the liquid to be measured is irradiated with only the third irradiation light L3_S3And the third detection signal intensity of the third transmitted light T3 is I_T3. At this time, the control unit 31 calculates the turbidity N based on the following formula 8 instead of the formula 4.

[ formula 8 ]

In formula 8, I_S3(0)A third detection signal intensity of the third scattered light S3 obtained when only the third irradiation light L3 was irradiated to the liquid with the turbidity of 0 degrees. I is_T3(0)And a third detection signal intensity of the third transmitted light T3 obtained when only the third irradiation light L3 was irradiated to the liquid with the turbidity of 0 degrees.

α₁、α₂And α₃The correction coefficient α is a correction coefficient for making the contribution ratio of the first LED light source D1, the second LED light source D2, and the third LED light source D3 to the turbidity measurement closer to that of the conventional lighting source₁、α₂And α₃The correction coefficient α is calculated by the same method as the calculation method based on the order of calculating the correction coefficient α described in the first example of the correction method described above₁、α₂And α₃The spectral intensity ratio of 2 pairs of light sources out of 3 light sources is calculated, and the control unit 31 corrects the correction factor α₁、α₂And α₃Let any one of 1 s be 1, and determine pairs with other 2 light sources with the emission intensity of the corresponding light source as a reference, for example, the control unit 31 sets α₁When 1, the first LED light source D1 and the second LED light source D2 are determined as a pair, and the controller 31 calculates α based on the spectral intensity ratio of these light sources₂Similarly, the control unit 31 is set to α₁When 1, the first LED light source D1 and the third LED light source D3 are determined as a pair, and the controller 31 calculates α based on the spectral intensity ratio of these light sources₃。

In the above description, the scattered light S detected by the transmitted light detector 251 is sufficiently weak with respect to the transmitted light T, and the contribution of the scattered light S in the term of the detection signal intensity with respect to the transmitted light T is ignored as in the formula 4, but the method of calculating the turbidity N is not limited to this. For example, the control unit 31 may calculate the turbidity N by including the contribution of the scattered light S in the term of the detection signal intensity of the transmitted light T as shown in the following expression 9.

[ formula 9 ]

In equation 9, β is a constant determined by the shape and characteristics of the detection unit. Equation 9 shows that the component of the scattered light S is added to the detection signal intensity of the transmitted light T at a constant β ratio. In a turbidimeter, a part of the detection signal intensity of the scattered light S may be added to the detection signal intensity of the transmitted light T at a predetermined ratio, whereby good linearity can be obtained. In the turbidimeter as described above, the lamp light source can be replaced with 2 or more LED light sources by the above equation 9. By calculating the turbidity N using equation 9, the control unit 31 can obtain good linearity even in a wide range from a low turbidity to a high turbidity when a plurality of LED light sources are used. Conventionally, since the modes of change of the transmitted light T and the scattered light S are different between the low haze region and the high haze region, linearity in each region is optimized by adjusting the optical system. However, the control unit 31 can obtain good linearity over a wide range from low turbidity to high turbidity by calculating the turbidity N using the formula 9 through the same optical system.

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