JP2005181120A - Concentration measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a concentration measuring apparatus, capable of easily, precisely, and exactly measuring concentrations by enabling the selection of an arithmetic expression most appropriate for measuring the concentration of suspended solid components, in a liquid to be measured. <P>SOLUTION: The concentration of the suspended solid components, in the liquid to be measured, is measured by receiving the diffused and reflected light of light emitted into the liquid to be measured at lease at two light-receiving parts and performing computations through the use of an arithmetic expression using both light reception signals, one as a concentration detection main signal and the other as a correction signal. A plurality of types of arithmetic expressions are previously stored, and an arithmetic expression to be used is selected from among the plurality of types of arithmetic expressions, according to the liquid to be measured which is to be the object of the measurement. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an apparatus for measuring the concentration of sludge generated from facilities such as clean water, sewage, human waste, and wastewater treatment, and the concentration of suspended solids in the treatment process, and in particular, it is turbid by diffuse reflection using light. The present invention relates to a concentration measuring apparatus configured to measure the concentration of a quality component.

Conventionally, an ultrasonic method, an infrared method, a microwave method, a dry weight method, and the like are known as devices for measuring the concentration of turbid components in a liquid to be measured. In these measurement methods, there is a problem that the output value becomes unstable except for the dry weight method when the properties of the turbid component to be measured are changed or there are fluctuations in the concentration. If unstable concentration information is transmitted to and input to peripheral equipment or control equipment, it may cause malfunction in the monitoring system or processing system. Therefore, Patent Document 1 and Patent Document 2 measure the concentration of turbid components in the liquid to be measured by emitting light, particularly laser light, toward the liquid to be measured and receiving the diffuse reflection light. A concentration measuring apparatus has been proposed. In these concentration measuring apparatuses, the concentration output value is actually obtained basically as concentration output value = (concentration measurement value × correction coefficient) −compensation signal value (for example, temperature compensation signal value). . However, these patent documents do not describe the specific method of calculating the concentration measurement value and the correction coefficient in detail, and in actual measurement, properties and concentrations vary with a fixed arithmetic expression. It is difficult to accurately calculate the turbid component in the liquid to be measured. In addition, in order to ensure the accuracy of the arithmetic expression, the zero point adjustment of the device output is performed periodically or when the type of the liquid to be measured changes greatly, and there is a problem that the measurement is not convenient. It is left.
JP 2002-98637 A JP 2002-243640 A

  Accordingly, an object of the present invention is to provide a concentration measuring apparatus configured to obtain at least two systems of received light signals of a density measurement signal and a correction signal in the density measurement of the diffuse reflection light system of the optical system as described above. When calculating the concentration using both received light signals, the calculation formula that is most suitable for measuring the concentration of turbid components in the liquid to be measured can be selected so that the concentration can be measured easily and accurately with high accuracy. The object is to provide a concentration measuring device.

  In order to solve the above-described problem, the concentration measuring apparatus according to the present invention is configured so that the concentration of the turbid component of the liquid to be measured is diffused and reflected by the light emitted toward the liquid to be measured by at least two light receiving units. Received light, measured by calculating with one light-receiving signal as the density detection main signal and the other light-receiving signal as its correction signal, using the two light-receiving signals, and previously stored multiple types of equations The calculation formula to be used is selected from the plural types of calculation formulas according to the measured liquid to be measured.

  In this concentration measuring apparatus, the measurement results of the above-described plural types of arithmetic expressions are each obtained by a method specified in JIS or the like separately performed on the liquid to be measured (for example, a method defined in JIS or a sewage test method). It is preferable that a correlation (for example, a correlation coefficient) is obtained. That is, the arithmetic expression is established as a form that can be used for actual use by constructing the following database.

  For the concentration measurement, for example, at least two types of received light signals are received as described above at a certain concentration of the liquid to be measured, and at least two types of the signal values and the same at least in a plurality of liquids to be measured having different concentrations. The signal is received and the value is recorded (preferably, there are preferably signal value groups at five or more concentrations as a whole). The turbid component concentration of each liquid to be measured is separately measured by a method defined in JIS or the sewage test method. A database in which a combination of at least two kinds of signals recorded in advance and a separately determined turbidity component concentration is set as one set can be created, and similar combinations with different concentrations and liquids to be measured are completed, and a set of databases is created. Based on this database, apply the following multiple regression formulas, optical system theoretical formulas, or empirical formulas obtained from experience or experiments, and select the appropriate formula to express the concentration of the solution to be measured. To do.

  It is preferable that the plurality of types of arithmetic expressions include at least a multiple regression expression that performs arithmetic processing on the both received light signals by a multiple regression calculation method. By using the multiple regression equation, as will be described later, the calculation equation has high linearity over a wide concentration range, and the concentration to be measured can be calculated with high accuracy in a desirable form.

  The plurality of types of arithmetic expressions may include at least a theoretical expression of the optical system or a correction expression thereof. Furthermore, at least an empirical formula obtained by experiment can be included.

  In the present invention, the concentration of the turbid component of the liquid to be measured is received by at least two light receiving portions of diffusely reflected light emitted toward the liquid to be measured, and one of the received light signals is a concentration detection main signal. A concentration measuring apparatus is provided that performs measurement by using the other received light signal as a correction signal and calculating by a multiple regression equation using both received light signals. A plurality of multiple regression equations can be prepared.

  Also in this concentration measuring apparatus, it is preferable that the correlation between the calculation result by the multiple regression equation and the measurement result by a method prescribed in JIS or the like separately performed on the solution to be measured is obtained.

  In the present invention, the concentration of the turbid component in the liquid to be measured is received by at least two light receiving portions of the diffuse reflected light of the light emitted toward the liquid to be measured, and one of the light reception signals is detected as a concentration detection main component. Provided is a concentration measuring apparatus characterized in that a signal and the other received light signal are used as correction signals and measurement is performed by using both received light signals and calculating according to a theoretical equation of the optical system or a correction equation thereof. A plurality of theoretical formulas or correction formulas for the optical system can be prepared.

  Also in this concentration measuring apparatus, the correlation between the calculation result by the theoretical formula of the optical system or its correction formula and the measurement result by the method prescribed in JIS or the like separately performed on the liquid to be measured is required. Is preferred.

  Further, according to the present invention, the concentration of the turbid component of the liquid to be measured is received by at least two light receiving portions of the diffuse reflected light of the light emitted toward the liquid to be measured, and one of the light reception signals is detected as a concentration detection main component. There is provided a concentration measuring apparatus characterized in that a signal and the other received light signal are used as correction signals, and the both received light signals are used for calculation by an empirical formula obtained through experiments. A plurality of empirical formulas obtained by experiments can be prepared.

  Also in this concentration measuring apparatus, it is preferable that the correlation between the calculation result by the above empirical formula and the measurement result by a method prescribed in JIS or the like separately performed on the liquid to be measured is obtained.

  According to the concentration measuring apparatus of the present invention, in an apparatus that obtains at least two types of received light signals using an optical diffuse reflection method, highly accurate concentration measurement can be performed over a wide measurement range from low concentration to high concentration. It becomes possible. In addition, an arithmetic expression with high linearity that passes through the zero point or the vicinity thereof is established, and the density can be accurately and accurately calculated by the arithmetic expression. As a result, the measurement accuracy of the apparatus can be dramatically improved, and zero-point calibration, that is, it can be freed from troublesome work such as removing the device, immersing in fresh water, and adjusting the zero point by dial adjustment. Furthermore, when the concentration measuring apparatus according to the present invention is used, past data can be stored in a PC (personal computer). Even when the concentration and properties of turbid components change, such as when the processing method is different, new data is added to the past data and recalculated to learn the past and update the formulas that were established sequentially It is also possible to perform concentration measurement using an optimal arithmetic expression at all times.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
First, the basic mechanical configuration of the concentration measuring apparatus according to the present invention will be described. As shown in FIG. 1, a densitometer 1 having a light receiving element is connected to a pipe 4 containing, for example, sludge particles 2 as a turbid component and flowing a sludge 3 as a liquid to be measured. Irradiation light 5 such as laser light is emitted toward the sludge 3 in the pipe 4, and the reflected reflected light 6 is received, and the received light signal is sent to the converter 8 via the dedicated cable 7 or the like. For example, as shown in FIG. 2, the signal from the converter 8 is sent to a computer 10 (for example, a personal computer PC) via a communication cable 9, and the computer 10 calculates the concentration using various arithmetic expressions as described later. , Output measurement data. The arithmetic expression is preferably incorporated as, for example, the CD software 11 so that it can be updated as necessary.

  The densitometer 1 can be configured as a densitometer 1 using a laser beam as shown in FIG. 3, for example. The densitometer 1 includes a laser diode driving circuit 12, a laser diode 13, an irradiation light side optical fiber 15 that guides the irradiation light 14 emitted from the laser diode 13, and a liquid contact glass 16 that forms a measurement surface (sensor surface). A reflected light side optical fiber 18 that receives and guides the diffuse reflected light 17 from the measured sludge particles 2 as described above, a photodiode 19 that converts the reflected light that has been guided into a received light signal that is an electrical signal, An amplification circuit 20 that amplifies the received light signal to a signal suitable for signal processing, a power supply / output unit 21 that supplies the pulsed power necessary for the laser diode driving circuit 12 and outputs a signal from the amplification circuit 20, and A connector portion 22 is provided.

  On the sensor surface of the liquid contact glass 16 of the densitometer 1 having such a basic configuration, for example, as shown in FIG. 4, a light emitting optical fiber end surface 23 and a light receiving optical fiber end surface 24 (light receiving) are provided at the center. And the optical fiber No. 1 end face) are randomly arranged to form the random portion 25. A light reception signal of diffuse reflected light received by the light receiving optical fiber end face 24 in the random portion 25 is used as a density detection main signal. Around the random portion 25 on the sensor surface, another light receiving optical fiber end surface 26 (end surface of the light receiving optical fiber No. 2) is annularly arranged to form a correcting portion 27. A light reception signal of diffusely reflected light received by the light receiving optical fiber end face 26 of the correction unit 27 is used as a light reception signal for correction of detection density. These two types of received light signals are used for density calculation by an arithmetic expression described later.

  Next, concentration calculation using the calculation formula in the present invention and concentration measurement by the calculation will be described. Table 1 shows light reception signals (light reception signals in the random section 25 [denoted as “random signals”) and light reception signals in the correction section 27 [denoted as “correction signals” in the concentration measurement of sludge as described above. ]) And the analytical concentration (expressed as “analyzed value”) measured by the method defined in JIS or the sewage test method separately conducted. In Table 1, the value of the signal is shown as a voltage value (volt (V)), but it may be a current value or a resistance value depending on the form of the densitometer.

  First, the concentration estimation value is obtained using the multiple regression calculation method with the analysis value shown in Table 1 as a dependent variable and the two types of signals of a random signal and a correction signal as dependent variables. FIG. 5 shows a relationship diagram by the PC software for illustrating the calculation formula and the calculation result.

The sludge concentration estimation formula obtained here is
Y = 1.4721 (M) −1.7455 (S) −0.975 (correlation coefficient r: 0.9951) (1)
It becomes. By writing the concentration estimation formula obtained here in the ROM of the concentration measuring device, the concentration measurement by the concentration measuring device becomes possible. here,
Y: Calculated density M: Random signal S: Correction signal r: Correlation coefficient representing the degree of correlation with the analysis value.

  As shown in FIG. 5, in the concentration estimation calculation formula based on the multiple regression calculation formula, an expression that passes substantially through the origin is obtained, a linear relationship is obtained in a wide range from low concentration to high concentration, and the correlation coefficient is also high. It can be seen that highly reliable and highly accurate measurement data can be obtained. In this way, when using the concentration estimation calculation formula based on the multiple regression calculation formula, since it substantially passes through the origin, the “zero-point calibration” operation that has been performed at a constant frequency with a conventional densitometer becomes unnecessary. As a result, there is an effect that the maintenance of the apparatus becomes easy.

In the present invention, the density can also be calculated by a theoretical formula of the optical system or its correction formula. The calculation method based on the theoretical formula of the optical system is performed as follows.
I = α · I ₀ · S · exp (−β · L · S)
M ² = α _R I ₀ ² · S ² · exp (−β · 2L _R · S)
S = α _C · I ₀ · S • exp (−β · L _C · S)
Here, if 2L _R = L _C ,
(2α _R · I ₀ ² · S ² ) / (α _C · I ₀ · S) = a · I ₀ · S
It becomes. here,
I: scattered light quantity I ₀ : irradiation light quantity S: sludge concentration α: optical system constant β: constant depending on properties such as sludge color L: optical path length subscript R from light irradiation part to light receiving part R: random part 25
Subscript C: Correction unit 27
Respectively. That is, in the theoretical formula of the optical system, it is said that M ² / S is proportional to the concentration.

When this optical system theoretical formula is applied and calculation is performed using the data in Table 1, the result is as shown in FIG. The concentration estimation formula obtained here is
Y = 0.1968 (M ² /S)−0.5560 (correlation coefficient r: 0.9748) (2)
It is. When this is compared with the previous equation (1), the correlation coefficient is 0.9 or more, which seems to be relatively correlated, but there are two practical disadvantages. First, the concentration estimation calculation formula does not pass through the origin “0 point”. In other words, if it is desired to measure the concentration of a suspended solid that does not pass through the “0” point, it is necessary to separately prepare a concentration estimation calculation formula in the vicinity of the concentration range and use it separately depending on the concentration range. The second point looks like the relational expression of FIG. 6 looks linear, but as shown in FIG. 6, it is actually a curved relational expression. That is, what is actually expressed by a quadratic curve equation is forcibly expressed by a linear equation. This displays an estimated value far from the actual density in the high density range or the low density range, that is, causes a measurement error.

Therefore, in the case where measurement in such a high density range or low density range is also required, FIG. 6 can provide a correction method for the arithmetic expression of the optical system theoretical formula. For example, the linearity can be improved by adding a calculation correction term of c such as (S + c) to the denominator of the equation represented by (M ² / S). FIG. 7 shows an example of a relational expression considering this calculation correction term.

The concentration estimation formula obtained here is
Y = 0.4414 (M ² /(S+1.0))−0.0961 (correlation coefficient r: 0.9995) (3)
When the calculation correction term c = 1.0, the correlation coefficient is substantially the same as the multiple regression calculation formula, and the linearity of the relational formula is also improved. However, the relational expression does not pass through the origin, and it has not been improved until the zero point calibration is unnecessary. Furthermore, the calculation correction term must be obtained by trial and error, and it is difficult to reach the most appropriate calculation correction term unless it is familiar with the use of the PC.

  Therefore, considering the above arithmetic expressions comprehensively, it can be said that the calculation and measurement by the multiple regression equation are most preferable from the viewpoint of convenience of handling, measurement accuracy, and elimination of zero point calibration.

  In addition to the above-described arithmetic expressions, it is also possible to incorporate empirical expressions obtained by experiments or the like. For example, if multiple empirical formulas are incorporated according to the type and properties of the liquid to be measured, concentration measurement with extremely high accuracy can be achieved if the correspondence between the type and characteristics of the liquid to be measured and the empirical formula to be used is taken appropriately. Is possible.

  In actual measurement, incorporate multiple arithmetic expressions as described above, or multiple multiple types of arithmetic expressions, and select the type and properties of the liquid to be measured from the multiple types of arithmetic expressions. An arithmetic expression to be used may be selected accordingly. In this way, it is possible to perform optimum concentration measurement according to the situation at that time with high accuracy.

  For example, various arithmetic expressions as shown in Table 2 can be stored, an optimal expression can be selected from these, and the coefficient can be written in the converter. In addition, the type and properties of the liquid to be measured are limited to a narrow range, and when the optimal calculation formula is known in advance, multiple regression calculation formulas, calculation formulas based on optical system theoretical formulas, and empirical formulas Thus, the concentration measurement can be performed using only one optimal arithmetic expression.

  The concentration measuring device according to the present invention can be applied to the concentration measurement of turbid components in any liquid to be measured, and is particularly suitable when highly accurate measurement is required over a wide concentration range and ease of maintenance is required. is there.

It is a schematic perspective view which shows an example of the mechanical basic composition of the density | concentration measuring apparatus which concerns on this invention. FIG. 2 is a schematic device system diagram of the concentration measuring apparatus of FIG. 1. It is a schematic sectional drawing which shows an example of a structure of the concentration meter part of the concentration measuring apparatus of FIG. It is a schematic front view which shows the example of arrangement | positioning of the optical fiber in the sensor surface of the densitometer of FIG. It is a graph which shows a density | concentration characteristic line at the time of using a multiple regression equation as a computing equation in the density | concentration measuring apparatus which concerns on this invention, a computed concentration is shown on a horizontal axis | shaft and an analytical concentration is shown on a vertical axis | shaft. It is a graph which shows a density | concentration characteristic line at the time of using an optical system theoretical formula as a computing equation in the density | concentration measuring apparatus which concerns on this invention, a computed density | concentration is shown on a horizontal axis and an analytical density | concentration is shown on a vertical axis | shaft. FIG. 4 is a graph showing density characteristic lines when a correction formula of an optical system theoretical formula is used as an arithmetic expression in the concentration measuring apparatus according to the present invention, where the horizontal axis indicates the calculated density and the vertical axis indicates the analytical concentration.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Densitometer 2 Sludge particle | grains as turbid component 3 Sludge as liquid to be measured 4 Piping 5 Irradiation light 6 Reflected light 7 Dedicated cable 8 Converter 9 Communication cable 10 Computer (personal computer PC)
DESCRIPTION OF SYMBOLS 11 CD software 12 Laser diode drive circuit 13 Laser diode 14 Irradiation light 15 Irradiation light side optical fiber 16 Liquid contact glass 17 which forms a measurement surface (sensor surface) Reflected light 18 Reflected light side optical fiber 19 Photodiode 20 Amplifying circuit 21 Power supply / Output unit 22 Connector unit 23 Light-emitting optical fiber end surface 24 Light-receiving optical fiber end surface (for concentration detection main signal)
25 Random part 26 Receiving optical fiber end face (for correction signal)
27 Correction part

Claims (11)

  The concentration of the turbid component of the liquid to be measured is measured by at least two light-receiving units that receive diffusely reflected light emitted toward the liquid to be measured. One light reception signal is the concentration detection main signal and the other light reception signal. As a correction signal, and a plurality of types of arithmetic expressions are stored in advance, and a target to be measured is selected from the plurality of types of arithmetic expressions. A concentration measuring device, wherein an arithmetic expression to be used is selected according to a measuring solution.   The concentration measuring apparatus according to claim 1, wherein each of the plurality of arithmetic expressions is correlated with a measurement result obtained by a method prescribed in JIS or the like separately performed on the liquid to be measured.   The concentration measuring apparatus according to claim 1 or 2, wherein the plurality of types of arithmetic expressions include at least a multiple regression expression for performing arithmetic processing on the both received light signals by a multiple regression calculation method.   The concentration measuring apparatus according to claim 1, wherein the plurality of types of arithmetic expressions include at least a theoretical expression of the optical system or a correction expression thereof.   The concentration measuring apparatus according to claim 1, wherein the plurality of types of arithmetic expressions include at least an empirical expression obtained by an experiment.   The concentration of the turbid component of the liquid to be measured is measured by at least two light-receiving units that receive diffusely reflected light emitted toward the liquid to be measured. One light reception signal is the concentration detection main signal and the other light reception signal. A concentration measuring apparatus characterized in that measurement is carried out by calculating a multiple regression equation using both received light signals as a correction signal.   The concentration measurement apparatus according to claim 6, wherein a correlation between a calculation result obtained by the multiple regression equation and a measurement result obtained by a method prescribed in JIS or the like separately performed on the solution to be measured is obtained.   The concentration of the turbid component of the liquid to be measured is measured by at least two light-receiving units that receive diffusely reflected light emitted toward the liquid to be measured. One light reception signal is the concentration detection main signal and the other light reception signal. As a correction signal, and using both received light signals, the density is measured by calculating according to a theoretical formula of the optical system or a correction formula thereof.   9. The concentration measurement according to claim 8, wherein a correlation between a calculation result based on a theoretical formula of the optical system or a correction formula thereof and a measurement result according to a method prescribed in JIS or the like separately performed on the liquid to be measured is obtained. apparatus.   The concentration of the turbid component of the liquid to be measured is measured by at least two light-receiving units that receive diffusely reflected light emitted toward the liquid to be measured. One light reception signal is the concentration detection main signal and the other light reception signal. A concentration measuring apparatus characterized in that, by using both received light signals as a correction signal, measurement is performed by an empirical formula obtained through experiments.   The concentration measuring apparatus according to claim 10, wherein a correlation between a calculation result based on the empirical formula and a measurement result according to a method prescribed in JIS or the like separately performed on the liquid to be measured is obtained.

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