JPH048746B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an apparatus for measuring the concentration of a solution using ultrasonic waves, which measures the concentration of a solution using the propagation velocity of ultrasonic waves in the solution and the temperature of the solution. It is known that the propagation speed of ultrasonic waves in a solution depends on the concentration of the solution, the temperature of the solution, and the like. Therefore, the concentration of the solution can be determined by knowing the temperature (T) of the solution and the propagation velocity (V) of the ultrasonic waves in the solution. However, although various measurements based on the aforementioned principles are possible in the laboratory, they are not often used in industrial processes. It is thought that the reason why it is not used in industrial processes is as follows. Even if a large number of N-V curves are prepared for each solution temperature (T), only approximate values can be obtained because the temperature of solutions in industrial processes is rarely kept constant. There is. It takes time to calculate using measured values. High accuracy cannot be obtained. SUMMARY OF THE INVENTION An object of the present invention is to provide an apparatus for measuring the concentration of a solution or the like using ultrasonic waves, which solves all of the above-mentioned difficulties. In order to achieve the above object, the ultrasonic concentration measuring device according to the present invention includes an ultrasonic wave transmitter supported in a solution to be measured, and an ultrasonic wave transmitter supported at a constant propagation distance with respect to the wave transmitter. A sonic wave receiver, an ultrasonic circuit that drives the transmitter and amplifies the received wave, a velocity calculation circuit that calculates the propagation velocity (V) from the propagation time and the propagation distance, and a temperature (T) in the solution to be measured. The relationship between the temperature sensor to detect, the temperature in the solution (T), the propagation velocity of ultrasonic waves (V), and the concentration N of the solution N=F(T,
a memory circuit in which a function indicating V) is stored; a concentration calculation circuit that calculates the concentration N by referring to the F(T, V) from the output (T) of the temperature sensor and the speed calculation circuit output (V); In an ultrasonic concentration measuring device configured with an output device that outputs the output of the arithmetic circuit, the function N=F(T, V) is a multidimensional polynomial N= 〓ai ^(ijk)・T ^j・V ^k (where i , j, and k are zero or positive integers), and a constant ai is stored in the storage circuit. The apparatus according to the present invention will be explained in more detail below with reference to the drawings and the like. FIG. 1 is a block diagram showing an embodiment of the apparatus according to the invention. An ultrasonic transducer 2 and a temperature sensor 4 are received in the solution to be measured 1 . An embodiment of the ultrasonic transducer will be described with reference to FIGS. 8A, 8B, and 8C. The ultrasonic sensor main body 23 is connected to the cable 21 by a plug 22, and is connected to a sing-around circuit 3 of an ultrasonic circuit to be described later. A vibrator 27 is provided at the center of the lower end surface of the main body 23 as shown in FIG. 8B. This vibrator 27 serves both as a transmitting vibrator and a receiving vibrator. The reflection plate 25 is fixed by four support rods 24, and the ultrasonic waves sent out from the transducer 27 are reflected by the reflection plate 25 and received by the transducer 27. Note that 26 is a set screw. The temperature sensor 4 is a thermocouple made of platinum. As shown in FIG. 9, the platinum wire temperature sensing parts 43 and 43
A cable 41 connects the temperature sensing section 43 to the thermometer side section 5. The ultrasonic circuit is composed of a known single-around section 3. The sing-around method transmits an ultrasonic burst, receives a reflected wave, then transmits again τ ₀ seconds after receiving the reflected wave, and then transmits again τ ₀ seconds after receiving the reflected wave. This method measures velocity (V). FIG. 10A shows the transmitted wave, and FIG. 10B shows the received wave. If the time from an arbitrary transmission point until (n+1) transmissions are performed is T (see Figure 10C), and the data is P=T/n obtained by calculation, the propagation velocity V is It is given by the following formula. V=
2L ₀ /(P-τ ₀ ) where L ₀ is the oscillator 2
7 and the distance to the reflecting plate 25. This calculation is performed by a central processing unit 8, which will be described later. In the device according to the present invention, ROM1, which is a storage circuit,
Function F (T, V) to calculate the concentration N of the solution from the temperature in the solution (T) and the propagation velocity of the ultrasonic wave (V).
As an example, constants of multi-dimensional polynomials are stored. This multidimensional polynomial is generally N=Σai・T ^j・V ^k (i,
j, k: 0...n). This multidimensional polynomial is determined for each solution. The method for determining the constant ai described above will be briefly described using the NaCl solution as an example. First, it is determined how many orders of the multidimensional polynomial are to be used. Generally, the coefficients of higher order terms are small, so the number of order terms to be used is determined by the measurement accuracy requirements. For the Nacl solution, a multidimensional polynomial including an unknown constant is set as shown below. N=a ₀ +a ₁ T+a ₂ V+a ₃ T ² +a ₄ TV+a ₅ V ² +a ₆ T ² V+a ₇ TV ² +a ₈ T ² V ² ...(1) Molar concentration of Nacl, 0.0, 1.0, 2.0, 3.0, 4.0 and temperatures of 10°C, 20°C, 25°C, 30°C, 40°C, 45°C, and 50°C, Attached Table 1 shown at the end of the detailed description of the invention
The propagation velocity V of ultrasonic waves in the NaCl solution is measured using the nine combinations shown below. The measurements of each temperature and velocity V can be performed using a part of the apparatus according to the present invention, as will be described later. By substituting N, T, and V shown in Attached Table 1 into Equation (1) above and solving a 9-element simultaneous equation with a ₀ , a ₁ ... a ₈ as unknowns, each coefficient ai is calculated as shown in Attached Table 2.
can be determined. This AI is not illustrated
By writing information into the ROM 10 shown in FIG. 1 using a ROM writer, a memory circuit in which ai is stored is configured. The ROM writer section calculates and verifies each coefficient AI from each Ni, Vi, and Ti (the above AI is not used for calculation).
Ni, Vi, Ti) and only if each ai is appropriate
Stored in ROM. The circuit portion indicated by 7 in FIG. 1 is an interface circuit, and the output from the temperature measuring section 5 mentioned above is connected to the interface 7 via an A/D converter 6. The aforementioned sing-around part 3
Also, signals are exchanged with other parts via this interface 7. The function setting device 13 connected to the interface 7 is a setting device for setting the operation of this device, and has a function of counting and displaying only the temperature T, a function of measuring and displaying only the speed of sound V, and the present invention by using these measured values. The function of calculating and displaying the concentration N, which is the original purpose of the device, is set. The constants L ₀ and τ ₀ necessary for determining the speed of sound (V) described above are input by the L ₀ setter 11 and the τ ₀ setter 12 connected to the interface 7, respectively. The central processing unit 8 is a central processing unit that executes instructions for executing functions set by the function setter 13 and arithmetic processing to be described later.
The RAM 9 is a temporary storage device that temporarily stores calculation results required during the calculation process. measured value,
The calculation results are input to the output buffer 14 via the interface 7, and the display specified by the function setter 13 is displayed on the display 17. Note that from the output buffer 14 to the output circuit 18, a digital output and D/A converter 15,
These outputs, which can be taken out as analog outputs via the level shift section 16, can be used as automatic control of the solution to be measured and other control information. The display 17 and the output circuit 18 form the output device of the device. Next, the operation and calculation process of the apparatus of the embodiment will be explained in detail with reference to FIGS. 2 to 7. FIG. 2 is a general flow chart of the apparatus of the embodiment. Turn on the power and
A function to be executed by this device is set by a function setter 13. When setting the sound velocity (V) or concentration (N), L ₀ and τ ₀ are set using the setting devices 11 and 12 described above. When started (100) in this state, initialization (200) is performed as shown in FIG. The initialization (200) step is the third
As shown in detail in the figure, stack pointer setting (201), input/output port setting (202), and work area clearing (203) are performed. Next, variable setting (300) is performed. In the variable setting step (300), as _shown in _FIG . Counting (303) of ×L ₀ values is performed. Next, depending on which function is set, either a temperature (T) processing subroutine, a sound velocity (V) processing subroutine, or a concentration (N) processing routine is executed. The temperature (T) processing subroutine (500) inputs digitized temperature information from the A/D converter 6 shown in FIG. 1 (502) and stores it in the memory buffer (503).
This routine is repeatedly executed to constantly provide the latest temperature (T) information to the memory buffer. The sound velocity V processing subroutine (600) inputs data P (corresponding to 1/n of the pulse width T in FIG. 10) to the calculation unit (602), and inputs L ₀ , τ previously input to the memory buffer. The procedure of calculating the value of 2L ₀ /(P-τ ₀ ) using ₀ (603) and storing the result in the memory buffer (604) is repeatedly executed. The concentration (N) processing routine (700) is shown in FIG. In this routine, the speed of sound (V)
A processing subroutine (600) and a temperature processing subroutine (500) are used. First, the sound velocity (V) obtained by executing the sound velocity (V) processing subroutine (600)
Convert the value from decimal to hexadecimal (701). Furthermore, the value of temperature T obtained by executing the temperature processing subroutine (500) is converted from decimal to hexadecimal. (702). Next, the concentration N is calculated from the converted V, T and the constant ai stored in the ROM 10 (703). Then convert the concentration value to hexadecimal (704)
The result is stored in the memory buffer area.
(V), (T), (N) obtained in this way are
Display according to specified function (800)
is performed on the display 17. Regarding the NaCl aqueous solution mentioned above, the concentration NiM was measured by the measuring device at various temperatures for several types of solutions with molar concentrations of Ni already known, and is shown in Attached Table 3 together with the actually measured velocity (V). From Attached Table 3, it can be seen that Ni and NiM are completely consistent. As described above, the device according to the present invention can display or output the concentration of the solution to be measured in real time and can obtain high accuracy, so it can be well applied to industrial processes. Using the aforementioned multi-degree polynomial of zero or a positive integer, the density can be determined by a simple operation of inserting V and T into the multi-degree polynomial separately without performing division or the like. Furthermore, if the ai is prepared for each solute, the concentration of the corresponding solution can be measured. It is given as a solution to the simultaneous equations of ai and can be easily and rationally determined. Although the above-mentioned apparatus has been described in detail for the case where the solution to be measured is a NaCl aqueous solution, it is possible to measure the concentration of the following various solutions. (a) Various aqueous solutions (b) Various non-aqueous solutions, such as alcoholic solutions of amines (c) Oils and fats, such as corn oil, olive oil,
It is also possible to measure the concentration (for example, expressed in weight %) of a slurry. Therefore, the device according to the invention can be widely applied to inorganic and organic plants, food processing factories, etc.

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【table】 [Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the apparatus according to the present invention, FIGS. 2, 3, 4, 5, and 6.
7 and 7 are flowcharts for explaining the operation of the device, FIG. 8A, FIG. 8B and FIG. The figure shows an embodiment of the temperature sensor, and FIG. 10 is a graph for explaining the sing-around method. 1... Solution to be measured, 2... Ultrasonic transducer, 3
... Sing-around part, 4 ... Temperature sensor, 5
... Temperature measurement section, 6 ... A/D converter, 7 ... Interface, 8 ... Central processing unit, 9 ...
RAM, 10...ROM, 11...L ₀ setting device, 1
2...τ ₀ setting device, 13... Function setting device, 14... Output buffer, 15... D/A converter, 16... Level shift, 17... Display section, 1
8...Output circuit.

Claims (1)

[Scope of Claims] 1. An ultrasonic wave transmitter supported in a solution to be measured, an ultrasonic wave receiver supported while maintaining a fixed propagation distance with respect to the wave transmitter, and an ultrasonic wave receiver supported in a solution to be measured; an ultrasonic circuit that drives and amplifies the received wave; a speed calculation circuit that calculates the propagation velocity (V) from the propagation time and the propagation distance;
A temperature sensor that detects the temperature (T) in the solution to be measured, a function that indicates the relationship N = F (T, V) between the temperature (T) in the solution, the propagation velocity of ultrasonic waves (V), and the concentration N of the solution. a memory circuit in which is stored, a concentration calculation circuit that calculates the concentration N by referring to the F (T, V) from the output (T) of the temperature sensor and the speed calculation circuit output (V), and an output of the calculation circuit. In ^an ultrasonic ^{concentration} measurement device configured with ^an output device that outputs , zero or a positive integer), and a constant ai is stored in the storage circuit. 2 When the measurement target is a NaCl solution, the multidimensional polynomial is N=a ₀ +a ₁ T+a ₂ V+a ₃ T ² +a ₄ TV+
The ultrasonic concentration measuring device according to claim 1, wherein a ₅ V ² + a ₆ T ² V + a ₇ TV ² + a ₈ T ² V ² . 3. The ultrasonic concentration measuring device according to claim 1, wherein the ultrasonic circuit is a single-around circuit.