JP2003215112A - Ultrasonic wave density meter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately measure the density and concentration of sludge without disturbing an interface between a liquid and the sludge. <P>SOLUTION: Since an ultrasonic wave transmission reception sensor 1 is fixed and installed at a prescribed position in supernatant water 2, so that the interface is not disturbed. The measurement principle uses that the ultrasonic wave pulse transmitted from a sensor 1 is reflected at the interface 4 between the supernatant water 2 and the sludge 3 and the amount of the diffusion and the amount of attenuation of the ultrasonic wave pulse until being received by a reception means 6 are proportional to the density. The depth to the interface is acquired from the propagation time of the ultrasonic wave pulse by an operating means 9. The density is acquired from the depth, a reception amplitude value measured by a measurement means 7 and the standard value of the reception amplitude value stored in a storage means 14 beforehand by an operating means 12. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic densitometer for measuring the density of sludge (hereinafter simply referred to as sludge density) at the interface between a liquid and sludge using ultrasonic waves, and measurement of both density and concentration. And an ultrasonic densitometer capable of

[0002]

2. Description of the Related Art A conventional example of an ultrasonic densitometer is shown in FIG. As shown in the figure, the ultrasonic densitometer includes an ultrasonic wave transmitter 1a.
And the ultrasonic wave receiving unit 1b are opposed to each other with a constant distance therebetween, and the attenuation of the ultrasonic wave by the sludge between the ultrasonic wave transmitting unit 1a and the ultrasonic wave receiving unit 1b has a constant proportional relationship with the sludge concentration. Is used to calculate the sludge concentration.

A conventional example of an optical densitometer is shown in FIG. As shown in the figure, the optical densitometer is provided with the light emitting element 22a and the light receiving element 22b facing each other on the side surface of the glass tube,
The sludge concentration is calculated by utilizing the fact that the attenuation amount of received light due to transmission and scattering has a constant proportional relationship with the sludge concentration.

[0004]

The ultrasonic densitometer shown in FIG. 5 (a) detects the position by moving the ultrasonic transmission / reception sensor 1 up and down by a person or a vertical drive mechanism.
There is a problem that the suspended matter floating in the liquid settles and disturbs the sludge interface formed. Further, since the optical densitometer shown in FIG. 5B also moves the optical sensor up and down to detect the position, the same problem occurs.

Therefore, an object of the present invention is to eliminate the possibility of disturbing the sludge interface and to enable accurate measurement.

[0006]

In order to solve such a problem, in the invention of claim 1, an ultrasonic pulse is fixedly installed at a predetermined position in the liquid and an ultrasonic pulse is transmitted toward sludge in the liquid. At least one ultrasonic transmission / reception device that receives a reflected pulse, an amplitude value measuring unit that measures an amplitude value of the reflected pulse, and a propagation time in a liquid from the start of transmission of the ultrasonic pulse to the reception thereof. Propagation time measurement means, depth calculation means for calculating the depth from the propagation time to the sludge interface, density calculation for calculating sludge density from the depth of the sludge interface, reception amplitude value and calibration value of reception amplitude value And means.

In the invention of claim 1, calibration value storage means for storing the calibration value of the received amplitude value can be provided (invention of claim 2), and in the invention of claim 2, the ultrasonic wave is used. An ultrasonic wave receiving means for receiving an ultrasonic wave pulse transmitted from a transmitting / receiving device at a constant distance, and a calibration value calculating means for calculating a calibration value based on the output from this ultrasonic wave receiving means are provided, and the calculated calibration value Can be stored in the calibration value storage means (the invention of claim 3).

In the invention of claim 3, a moving mechanism for moving the ultrasonic wave receiving means in the traveling direction of the ultrasonic pulse can be provided (invention of claim 4), and in the invention of claim 3 or 4, The ultrasonic wave receiving means may be a reflector (the invention of claim 5).

According to the first to fifth aspects of the invention, concentration calculating means for calculating the sludge concentration from the sludge weight for a certain amount of water can be provided based on the output from the density calculating means (the invention of the sixth aspect). ).

[0010]

1 is a block diagram showing a first embodiment of the present invention.

As shown in the figure, the ultrasonic densitometer according to the present invention mainly comprises an ultrasonic wave transmitting / receiving sensor 1, a converter 5 and a display device 10. The converter 5 is provided with transmission / reception means 6, amplitude value measurement means 7, propagation time measurement means 8, depth calculation means 9, density calculation means 12, concentration calculation means 13, calibration value storage means 14, and the like. There is. Reference numeral 2 indicates clear water, 3 indicates sludge, and 11 indicates a sedimentation basin.

The ultrasonic wave transmission / reception sensor 1 is fixed in the liquid of the supernatant water 2 and transmits a transmission signal to the sludge 3 and the sludge interface 4 at regular intervals, and ultrasonic waves are reflected waves reflected at the sludge interface. It is received by the transmission / reception sensor 1 and input to the converter 5, and the result is displayed on the display device 10 through various calculation means. Although only one ultrasonic transmission / reception sensor 1 is shown, a plurality of ultrasonic transmission / reception sensors 1 may be used.

In the above configuration, the reception signal input to the converter 5 is, for example, as shown in FIG. 2, the propagation time t in the liquid from the start of transmission of the ultrasonic pulse to the reception, and the reception amplitude value v. The received amplitude value v is measured by the amplitude value measuring means 7 which has passed through the transmitting / receiving means 6, the propagation time t is measured by the propagation time measuring means 8, and the depth is calculated by the depth calculating means 9. Is calculated. Here, the depth L is represented as half of the distance traveled while the ultrasonic wave is reflected back at the sludge interface 4 (reciprocates).

Depth L = C ₀ × t / 2 C ₀ : Sound velocity in liquid, t: Propagation time density calculation means 12 calculates the density based on the data from the depth calculation means 9 and the calibration value storage means 14. calculate. Hereinafter, how to obtain it will be described.

Generally, the acoustic impedance (ρ ₀ × C ₀ ) represented by the product of the density ρ _{0 of} the liquid (here, supernatant water) in which the ultrasonic wave propagates and the propagation velocity C ₀ , and the liquid in the sedimentation state of the suspended matter. If there is a difference in acoustic impedance, such as the acoustic impedance (ρ ₁ × C ₁ ) shown by the product of the density ρ _{1 of} (here, sludge) and the propagation velocity C ₁ , the boundary (sludge interface)
Reflection occurs at. The magnitude of the reflected wave is determined by the reflectance R ₁ .

From the above, the reception voltage V₁Is the reference distance
Diffusion damping coefficient from α₁(This is α ₁= As deep as kL
Is expressed as a function of L. k: constant) and sludge dispersal
Damping coefficient α due to disturbance and absorption₂And the reflectance R on the reflecting surface
₁And the voltage value (calibration value) V at the reference distance₀And with
Is expressed as

V ₁ = α ₁ × α ₂ × R ₁ × V ₀ = α ₁ α ₂ V ₀ (Z ₁ −Z ₀ ) / (Z ₁ + Z ₀ ) = α ₁ α ₂ V ₀ (ρ ₁ × C ₁ −ρ ₀ × C ₀ ) / (ρ ₁ × C ₁ + ρ ₀ × C ₀ ) When the acoustic impedance at the reflecting surface is calculated from the above equation, Z ₁ = ρ ₁ × C ₁ = ρ ₀ × C ₀ ( _{1 + V 1 / α 1 α} 2 V 0) / become _{(1-V 1 / α 1} α 2 V 0).

Since the sound velocity in sludge is constant or is proportional to the density, the density ρ ₁ can be calculated by the following equation.

Ρ ₁ = ρ ₀ (C ₀ / C ₁ ) (1 + V ₁ / α ₁ α ₂ V ₀ ) / (1-
V ₁ / α ₁ α ₂ V ₀ ) That is, the density at the interface between sludge or liquid and sludge is determined by depth L, reception voltage amplitude value V ₁ (proportional to reception amplitude value), and calibration voltage value V ₀ (reception It is proportional to the calibration value of the amplitude value). Note that C ₀ and C ₁ are treated as constant values here.

After the density calculation, the density calculation means 13 calculates the density. The concentration [mg / L] is calculated by the following formula as the sludge weight (mg) for a fixed amount (L) of water.

Concentration [mg / L] = (ρ ₁ [Kg / m ³ ] −ρ ₀ [Kg /
m ³ ]) × 10 ³ FIG. 3 is a block diagram showing the second embodiment of the present invention.

This is characterized in that a calibration value measuring means 15 and a calibration value calculating means 16 are added to those shown in FIG. The calibration value measuring means 15 is composed of an ultrasonic wave receiving device 15a and a moving mechanism 15b as shown in the figure, and the ultrasonic wave receiving device 15a is separated from the ultrasonic wave transmitting / receiving sensor 1 by a reference distance by the moving mechanism 15b in the calibration mode. The ultrasonic wave receiving device 15a receives the transmission signal from the ultrasonic wave transmission / reception sensor 1, and the amplitude value measuring means 7 is moved.
To the calibration value calculating means 16
The calibration value is obtained and stored in the calibration value storage means 14. While the one shown in FIG. 1 always stores a constant calibration value, the calibration value is updated each time here.

FIG. 4 is a block diagram showing a third embodiment of the present invention.

This is achieved by replacing the ultrasonic wave receiving device 15a of FIG. 3 with a reflection plate (made of, for example, stainless steel or Teflon (registered trademark)) 15c having a known sound velocity and density, and using this, a reference distance of a transmission signal. Since the amplitude value from is obtained and the calibration value is obtained, the details are omitted because it is the same as the case of FIG.

[0025]

According to the present invention, since the sludge density or concentration and the sludge interface depth can be measured without stirring the sludge interface, the measurement accuracy can be improved. Moreover, since a mechanism for moving up and down is not required, the structure is simple and the cost is reduced. Furthermore, since it is only necessary to add density calculation means, concentration calculation means, and calibration value storage means to the commercially available ultrasonic distance measurement type sludge interface meter, the configuration is simple and the cost can be reduced. .

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a propagation time and a reception amplitude value according to the present invention.

FIG. 3 is a configuration diagram showing a second embodiment of the present invention.

FIG. 4 is a configuration diagram showing a third embodiment of the present invention.

FIG. 5 is an explanatory diagram for explaining a conventional example.

[Explanation of symbols]

1 ... Ultrasonic wave transmitting / receiving sensor, 2 ... Clear water, 3 ... Sludge, 4 ...
Sludge interface, 5 ... Transducer, 6 ... Transmission / reception means, 7 ... Amplitude value measurement means, 8 ... Propagation time measurement means, 9 ... Depth calculation means,
10 ... Display means, 11 ... Sedimentation tank, 12 ... Density calculation means,
13 ... Concentration calculating means, 14 ... Calibration value storing means, 15 ... Calibration value measuring means, 16 ... Calibration value calculating means.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Akira Morita             1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa             Within Fuji Electric Co., Ltd. F term (reference) 2G047 AA02 BA03 BB01 BC02 BC03                       BC15 BC18 EA10 EA20 GF06                       GG20 GG33 GJ21

Claims (6)

[Claims] 1. An at least one ultrasonic transmitting / receiving device fixedly installed at a predetermined position in a liquid for transmitting an ultrasonic pulse toward sludge in the liquid and receiving a reflected pulse thereof, and an amplitude value of the reflected pulse. Amplitude value measuring means for measuring, the propagation time measuring means for measuring the propagation time in the liquid from the start of transmission of the ultrasonic pulse to the reception, and the depth for calculating the depth from the propagation time to the sludge interface Calculation means,
An ultrasonic density meter, comprising: a sludge interface depth, a reception amplitude value, and a density calculation means for calculating a sludge density from a calibration value of the reception amplitude value. 2. The ultrasonic density meter according to claim 1, further comprising a calibration value storage means for storing a calibration value of the reception amplitude value. 3. An ultrasonic wave receiving means for receiving an ultrasonic wave pulse transmitted from the ultrasonic wave transmitting / receiving device at a constant distance,
3. The ultrasonic wave according to claim 2, further comprising: a calibration value calculation means for calculating a calibration value based on the output from the ultrasonic wave reception means, and storing the calculated calibration value in the calibration value storage means. Density meter. 4. The ultrasonic density meter according to claim 3, further comprising a moving mechanism for moving the ultrasonic wave receiving means in a traveling direction of an ultrasonic wave pulse. 5. The ultrasonic density meter according to claim 3, wherein the ultrasonic wave receiving means is a reflecting plate. 6. Based on the output from the density computing means,
6. A concentration calculation means for calculating the sludge concentration from a certain amount of sludge weight for water is provided.
The ultrasonic density meter according to any one of 1.