JPH07190927A - Concentration measuring apparatus for suspension - Google Patents

Abstract

PURPOSE:To realize accurate measurement over a wide range from an ultra low concentration to a high concentration in an apparatus for measuring the concentration of a suspension in which a light beam is projected from an infrared LED into a water to be inspected through a detector section, the light scattered by the suspended solids in the water is received by light receiving elements for N and F disposed at two points separated differently from the infrared LED, and the concentration is measured based on an amplified signal. CONSTITUTION:Signals IN, IF are integrated, respectively, by integrating circuits 21a and 21b to obtain integrated values JN, JF. The time to required for the integrated value JN to reach a set value A0, is determined by a comparison circuit 22 and a time measuring circuit 23 and an operation Z=Ao<2>/JFto.t0 is performed at an operating circuit 24.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention measures the concentration of suspended substances in liquid such as MLSS (concentration of suspended solids in activated sludge), surplus sludge, return sludge, concentrated sludge, etc. during the treatment process by the activated sludge method of sewage. Regarding the device.

[0002]

2. Description of the Related Art A conventional suspension concentration measuring apparatus is, for example, the apparatus of Japanese Patent Application No. 62-324522 shown in FIG. This apparatus has a bundled optical fiber body 1 installed in a scattered light comparison type detection unit immersed in a test liquid to be measured, and a light source optical fiber 2 having a circular cross section arranged in the center thereof. An optical fiber 4 for N close to a light source (infrared light emitting diode 3) having an annular cross section is concentrically arranged so as to surround the outer periphery, and further, scattered light intensity obtained through the optical fiber 4 for N is formed. The squared I _N output is divided by the scattered light intensity I _F obtained through the F optical fiber 5 to obtain an output proportional to the sludge concentration.

In FIG. 3, reference numeral 1a designates the optical fiber body 1.
End face, 6 is the detector part, 7 is suspended particles, 8 is water detection, 9
Is a head for detection, 10 is a spacer, 11a, 11b, 11
Reference numerals c denote light receiving elements for N, F, and light sources, respectively.
The signal photoelectrically converted by the light source light-receiving element 11c is amplified by the amplifier 12c and then compared with a reference value in the comparison circuit section 13 to generate a light amount control signal of the light source. The light source drive circuit section 14 sends electric power appropriately controlled based on the light amount control signal to the infrared light emitting diode 3 to drive the infrared light emitting diode 3 so that the infrared light emitting diode 3 emits light with an appropriate light amount so that the light source intensity does not vary.

The N light receiving element 11a and the F light receiving element 1
The signals photoelectrically converted by 1b are amplifiers 12a and 12b.
After being amplified by, the arithmetic circuit 1 outputs the scattered light intensities I _N and I _F.
Input to 5. The arithmetic circuit 15 performs an operation of I _N ² / I _F to obtain an output proportional to the sludge concentration. This arithmetic circuit 1
The calculation result Z of 5 is output after being changed to a required output signal by the output circuit 16.

The output of the suspension concentration of I _N and I _F is shown in FIG.
become that way. When this is expressed by an equation, I _N = I ₀ · S · exp (−β _N · S) I _F = I ₀ · S · exp (−β _F · S) where I ₀ is the light source intensity and S is the suspension. Density, β _N , and β _F are constants determined by the positional relationship with the light source, color, and so on. Where I _N ² / I _F = I ₀ · S · exp (β _F −2β _N ).
・ S becomes S, and by setting β _F -2β _N = 0, I _N ² / I
_F = I ₀ · S, and the calculation result and the suspension concentration have a proportional relationship.

The apparatus shown in FIG. 3 has a configuration of β _F -2 β _N = 0 (β _N , β _F
Represents the distance between each light receiving element 11a, 11b and the infrared light emitting diode 3 and the color constant of the sludge), and the infrared light emitting diode 3 and each light receiving element 11a, 1
By deciding the arrangement of 1b, performing the arithmetic processing of I _N ² / I _F , and realizing the optical arrangement using the optical fiber,
As shown in FIG. 4, the calculation result Z proportional to the sludge concentration is obtained, and the sludge concentration can be measured with high accuracy.

In the measuring method of FIG. 3, the scattered light intensity I _F becomes 0 when the sludge concentration is 0, and the calculation result of I _N ² / I _F diverges. In order to prevent this, in the extremely small range of the scattered light intensity I as shown by I ₀ in FIG. 5, the scattered light intensity I _F is calculated as a constant value (Japanese Patent Application No. 63-164634).
The method described in 1) was used.

[0008]

In the apparatus of FIG. 3,
When the color of the suspended substance becomes close to black and the amount of scattered light decreases, the output (I _N , I _F ) of each light receiving unit becomes I _N ′, I _F ′ in FIG.
As shown in. Therefore, the above-described method of calculating I _F as a constant value makes it impossible to measure I _F ′ in which the scattered light intensity I is I ₀ or less.

[0009] While the amount of scattered light color of the thus suspension is close to black is reduced measurement becomes difficult, as a countermeasure in the conventional apparatus, or to increase the amount of light emission, increasing the gain of the I _F However, there is a limit to the implementation of these methods due to the circuit configuration.

The present invention has been made in view of the above points, and an object thereof is to provide a suspension concentration measuring apparatus capable of performing measurement in a stable operation even when the amount of scattered light is reduced and simplifying arithmetic processing. To provide.

[0011]

According to the present invention, there are provided (1) a light source for projecting a light beam into a test water and a point separated by a predetermined distance from the light source so as to receive light scattered by a suspended matter in the test water. A first light receiver installed, a second light receiver installed at a point farther from the light source than the predetermined distance, and a first light amplifier that amplifies light reception signals of the first and second light receivers, respectively. , Second
Any one of the first and second integrator circuits for integrating the output I _N of the first amplifier and the output I _F of the second amplifier, respectively. A time measuring circuit for obtaining the time until the integrated value of one of the integrating circuits reaches a predetermined integral set value, the time, the integral set value, and the integration of the other one when the integral set value is reached. Based on the integrated value of the circuit, an arithmetic circuit for performing a predetermined operation of the scattered light comparison method, characterized in that,
(2) The time measuring circuit is the integrated value J of the first integrating circuit.
A circuit for obtaining a time t ₀ until _N reaches an integration set value A ₀ , wherein the arithmetic circuit is a square of the A ₀ and is a _value of a second integration circuit of the second integration circuit when the A ₀ is reached. characterized by a circuit for performing an operation of dividing by the product of the integrated value J _F-to and t _0, (3) the time measuring circuit, the integrated value J _F of the second integrating circuit integrating a set value B ₀ A circuit for obtaining a time t ₀ until reaching, wherein the arithmetic circuit squares an integral value J _N to of the first integrator circuit when reaching the B ₀ , and the obtained values are B ₀ and t _0. It is characterized in that it is a circuit that performs an operation of dividing by the product of.

[0012]

[Action]

(1) In the invention described in claims 1 and 2, when the integral value J _N of the first integrator circuit reaches the set value A ₀ , the following equation is established.

[0013]

[Equation 1]

[0014]

[Equation 2]

(However, t ₀ is the time when J _N becomes A ₀ ) Here, considering that the time of t ₀ is much shorter than the time when the sludge concentration of the measurement object changes,

[0016]

[Equation 3]

[0017]

[Equation 4]

Can be considered as When this is applied to the calculation formula Z = I _N ² / I _F of the scattered light comparison system, Z = I _N ² / I _F = (A ₀ / t ₀ ) ² / (J _F to / t ₀ ) = A
₀ ² / t ₀ · J _F to ... (5) By calculating this equation (5), A _o
By appropriately selecting the value of, even if the amount of scattered light is small because the color of the suspended substance becomes close to black, it is possible to reliably perform measurement. Further, in the equation (5), it is not necessary to square the detection signal I _N , so the calculation is simplified.

(2) In the invention described in claims 1 and 3, when the integrated value J _F of the second integrating circuit reaches the set value B ₀ , the following equation is established.

[0020]

[Equation 5]

[0021]

[Equation 6]

(However, t ₀ is the time when J _F becomes B ₀ ) Here, considering that the time of t ₀ is much shorter than the time when the sludge concentration of the measurement object changes,

[0023]

[Equation 7]

[0024]

[Equation 8]

Can be thought of as When this is applied to the arithmetic expression Z = I _N ² / I _F of the scattered light comparison system, Z = I _N ² / I _F = (J _N to / t ₀ ) ² / (B ₀ / t ₀ ) = J
_N to ² / B ₀ t ₀ (10) By calculating this equation (10), B
By properly selecting the _o value, it is possible to reliably perform measurement even when the color of the suspended substance is close to black and the amount of scattered light is small.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the same parts as those in FIG. 3 are designated by the same reference numerals and the description thereof will be omitted. The amplifiers 12a, 1
The output signals I _N and I _F of 2b are integrated by integrating circuits 21a and 21b, respectively, and the integrated values

[0027]

[Equation 9]

[0028]

[Equation 10]

Is required.

Reference numeral 22 is a comparison operation circuit for comparing the integrated value J _N with a set value A ₀ set from the outside. 23 is the time when the comparison results of the comparison operation circuit become equal, that is,

[0031]

[Equation 11]

The time measuring circuit outputs the time t as t _{0 at} the time when the time becomes and at the same time outputs a reset signal to the integrating circuits 21a and 21b. 24 is A ₀ ² / J _F t
This is an arithmetic circuit that performs an arithmetic operation of o · t ₀ . The calculation result Z of the calculation circuit 24 is output by the output circuit 25 after being replaced by the required output signal Z '. The output circuit 25 outputs the previous value until the next calculation result is obtained, and updates the value each time the calculation result is obtained.

The structure of the detector section 6 and a part of the light of the infrared light emitting diode 3 are received by the light receiving element 11c for the light source, and the amount of light received is constant by the amplifier 12c, the comparison circuit section 13 and the light source drive circuit section 14. The control part is configured the same as in FIG.

In the apparatus configured as described above, the signals I _N and I _F input to the integrating circuits 21a and 21b are as shown in FIG.
Each is integrated as shown in. J _N to, J _F to in FIG.
Is an integral value when the above expression (13) is satisfied, and is expressed by the following expression.

[0035]

[Equation 12]

[0036]

[Equation 13]

Considering that the time t ₀ is much shorter than the time when the sludge concentration to be measured changes,

[0038]

[Equation 14]

[0039]

[Equation 15]

Can be considered as When this is applied to the calculation formula Z = I _N ² / I _F of the scattered light comparison system, Z = I _N ² / I _F = (A ₀ / t ₀ ) ² / (J _F to / t ₀ ) = A
₀ ² / t ₀ J _F to ... (5) Therefore, by calculating the equation (5) by the arithmetic circuit 24, the measurement result can be stably obtained over all the concentration regions including the extremely low concentration region.

In the above method, the calculation output cycle t ₀ changes depending on the value of I _N ′ in FIG. 5, but it is effective when the time for changing the concentration of the measurement object is longer than t ₀ .

In the above embodiment, the integral set value A ₀ is set as in equation (1) to determine the end point of the integration, but conversely, the end point of the integration may be determined on the _IF side. That is,

[0043]

[Equation 16]

Integral values J _F to, J _N to when satisfying
To

[0045]

[Equation 17]

[0046]

[Equation 18]

Then, considering that t ₀ is much shorter than the sludge concentration change time in the same manner as described above,

[0048]

[Formula 19]

[0049]

[Equation 20]

It can be This was applied to a computing equation Z = I _N ² / I _F of a conventional scattered light comparison ^{_{method, Z = I N 2 / I}} F = (J N to / t 0) 2 / (B 0 / t 0) = J
Obtaining a measurement result of the sludge concentration to calculate the ^{_{N to 2 / B 0 t 0}} ... (10) becomes operational expression.

In this case, the circuit of FIG. 1 is partly modified so that the output J _F of the integrating circuit 21b and the integral set value B ₀ are compared and calculated 22.
And the time t ₀ until J _F reaches B ₀ is calculated by the time measuring circuit 23, and the calculation formula (10) (Z = J
_{If N} to ² / B ₀ · t ₀ ) is configured to be calculated and output by the arithmetic circuit 24, it can be easily implemented.

In general, since I _N > I _F , the equation (3) is more accurately required for measuring t ₀ than the equation (6). Further, various calculations of the circuit of FIG. 1 may be realized by software processing by a computer.

[0053]

As described above, according to the first, second and third aspects of the present invention, the first and the second of integrating outputs I _N and I _{F of the} amplifier, respectively.
A second integrator circuit, a time measuring circuit for determining a time required for the integrated value of one of the first and second integrator circuits to reach a predetermined integral set value, and the time. Since an integration setting value and an operation circuit for performing a predetermined operation of the scattered light comparison method based on the integration value of the other integration circuit when the integration setting value is reached are provided,
Even if the color of the suspension is close to black and the amount of scattered light is extremely reduced, the measurement can be sufficiently performed. Therefore, accurate measurement can be expected in a wide range from extremely low concentration to high concentration.

According to the first and second aspects of the present invention, it is not necessary to perform the square calculation of the detection signal (calculation for obtaining I _N ² / I _F ) as in the conventional case, and the calculation is greatly simplified. It Therefore, the calculation processing speed is increased.

[Brief description of drawings]

FIG. 1 is an overall schematic configuration diagram showing an embodiment of the present invention.

FIG. 2 is an integrated waveform diagram for explaining the operation of an integrator circuit, which is a main part of the embodiment.

FIG. 3 is an overall schematic configuration diagram showing an example of a conventional suspension concentration detecting device.

FIG. 4 is a characteristic diagram showing the relationship between SS concentration and calculation results.

FIG. 5 is a characteristic diagram showing the relationship between SS concentration and scattered light intensity.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Bundled optical fiber body 2 ... Light source optical fiber 3 ... Infrared light emitting diode 4 ... N optical fiber 5 ... F optical fiber 6 ... Detector part 11a ... N light receiving element 11b ... F light receiving element 11c ... Light source Light receiving elements 12a, 12b ... Amplifier 13 ... Comparison circuit section 14 ... Light source drive circuit section 21a, 21b ... Integrating circuit 22 ... Comparison arithmetic circuit 23 ... Time measuring circuit 24 ... Arithmetic circuit 25 ... Output circuit

Claims (3)

[Claims] 1. A light source for projecting a light beam into the test water, a first light receiver installed at a point separated from the light source by a predetermined distance so as to receive light scattered by suspended matter in the test water, and the light source. The second installed at a point where the distance from
And light receiver, wherein the first, the first amplifying each received light signal of the second photodetector, a second amplifier, and an output I _F output I _N and a second amplifier of the first amplifier First to integrate each,
A second integrator circuit, a time measuring circuit for determining a time required for the integrated value of one of the first and second integrator circuits to reach a predetermined integral set value, and the time. It is characterized by further comprising an arithmetic circuit for performing a predetermined arithmetic operation of the scattered light comparison method based on an integral set value and an integral value of the other one of the integral circuits when the integral set value is reached. Suspension concentration measuring device. 2. The time measuring circuit is a circuit for obtaining a time t ₀ until the integrated value J _N of the first integrating circuit reaches an integral set value A ₀ , and the arithmetic circuit is the A _0. The suspension circuit according to claim 1, wherein the circuit is a circuit that performs an operation of dividing a _squared value by a product of the integral values J _Ft0 and t ₀ of the second integrator circuit when reaching A _0. Suspended substance concentration measuring device. 3. The time measuring circuit is a circuit for obtaining a time t ₀ until the integral value J _F of the second integrating circuit reaches an integral set value B ₀ , and the arithmetic circuit is the B _0. 2. The _suspension circuit according to claim 1, wherein the circuit is a circuit for performing an operation of dividing a square of an integral value J _Nt0 of the first integrator circuit when the value of is reached by the product of B ₀ and t _0. Suspended substance concentration measuring device.