WO1994014056A1

WO1994014056A1 - Densitometer

Info

Publication number: WO1994014056A1
Application number: PCT/JP1993/001816
Authority: WO
Inventors: Takaaki Matsumura
Original assignee: Etex Co., Ltd.
Priority date: 1992-12-15
Filing date: 1993-12-15
Publication date: 1994-06-23
Also published as: TW295621B; AU5714594A

Abstract

This densitometer is small, easy to handle, and inexpensive. It is also capable of measuring concentration on-line. On the detecting tip of a concentration detector (6) which is dipped in a sample solution, an electrolytic aqueous solution, there are installed a coil (12), and a high frequency oscillating circuit (11) using the coil as an element of oscillation. The concentration of the sample solution is measured by detecting the changes of the oscillating state of the high frequency oscillating circuit when the detecting tip is dipped in the sample solution.

Description

Description Densitometer

, Technical field

The present invention relates to a liquid concentration meter, particularly to a concentration meter for measuring the concentration of an aqueous electrolyte solution containing ions. Background art

In the chemical industry, food manufacturing, semiconductor manufacturing, and other industrial fields, aqueous solutions of electrolytes such as caustic soda NaΟ and hydrochloric acid are used for chemical treatment and cleaning. Is used. These electrolyte aqueous solutions are required to have a relatively high concentration of 0.1 wt% to several wt% or several tens wt%, and have a strong chemical reaction of acids, alkalis, etc. There are many things that need to be handled with care, such as danger, and it is also necessary to supply a specified concentration at such a high concentration over a long period of time, as in a mass production factory. I have.

In order to continuously control the concentration of such a high-concentration electrolyte solution, methods such as titration require too much time and effort, and must be adapted to recent computer-based production management systems. Therefore, there is a need for an online concentration measurement method.

The densitometer therefor, there is a conductivity meter at concentrations ranging from ppm order to about LWT%, conductivity meter, no current flows polarization with a concentration of over about 1 1% or ⁴ is generated From that, on

However, it is not enough to measure the concentration of a high-concentration aqueous electrolyte solution as described above.

Therefore, in such a high concentration range, a so-called electromagnetic concentration meter is used. Used. An electromagnetic densitometer measures conductivity by immersing a transformer consisting of two superimposed annular coils for transmission and detection in a sample solution and using the electromagnetic induction current flowing in the solution passing through the through-hole. Although the concentration measurement range is up to several tens of Wt%, and online concentration measurement is possible, there is a problem that it is large, unwieldy, and expensive. .

SUMMARY OF THE INVENTION An object of the present invention is to provide an inexpensive densitometer that is capable of on-line concentration measurement, and that is small, easy to handle, and inexpensive to solve the above-mentioned problems of the prior art. . Disclosure of the invention

In the concentration meter according to the present invention, a coil and a high-frequency oscillation circuit including the coil as an oscillating element are mounted on a detection end of a concentration detector immersed in a sample solution which is an aqueous electrolyte solution, and the detector is provided in the sample solution. It is configured to measure the concentration of the sample liquid by detecting a change in the oscillation state of the high-frequency oscillation circuit when immersed in the sample.

Further, the concentration meter according to the present invention is configured such that the coil is formed in a flat spiral shape, and is integrated with a high-frequency oscillation circuit by a resin to form a detection end of a concentration detector immersed in a sample solution. You. The flat spiral coil is placed parallel to the end face of the detection end of the concentration detector immersed in the sample liquid, or the detection end of the concentration detector immersed in the sample liquid. It is arranged so as to protrude vertically from the end face. Further, the flat spiral coil is formed by being densely wound or coarsely wound depending on the purpose of use.

Since the concentration meter according to the present invention is configured as described above, if the detection end is immersed in the aqueous electrolyte solution to be measured, the conductive aqueous electrolyte solution is electromagnetically coupled to the coil and the detector is connected to the detector. Oscillation circuit inside Since this influences the oscillation conditions, the current supplied to the oscillation circuit changes according to the conductivity of the aqueous electrolyte solution and thus the concentration. Since the electrolyte aqueous solution around the detection end is considered to affect the volume, the detector is immersed to a predetermined depth, and the liquid exists within a predetermined distance around the detection end. If the conductor such as metal is kept away from the range, the influence of the aqueous electrolyte solution on the oscillation conditions of the oscillation circuit is stabilized, and the accuracy of the concentration measurement can be improved.

In addition, by forming the coil in a flat spiral shape and arranging it at the detection end, the facing area between the coil and the sample solution increases, and high-accuracy concentration measurement becomes possible. Even if the coil is formed in a ring shape, the same operation and effect as those of a flat spiral coil can be achieved.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic configuration diagram showing an appearance of an embodiment of a densitometer according to the present invention.

FIG. 2 is a block diagram showing a circuit configuration of a signal processing circuit for density detection in an embodiment of the densitometer according to the present invention.

FIG. 3 is a conceptual structure diagram showing a structure of a sensor according to the embodiment of the present invention.

FIGS. 4A and 4B are an internal structural view and an external perspective view, respectively, showing an enlarged tip portion for illustrating the configuration of another embodiment of the sensor in the densitometer according to the present invention.

FIGS. 5A and 5B are an internal structure diagram and an external perspective view, respectively, showing an enlarged tip portion for illustrating the configuration of still another embodiment of the sensor in the densitometer according to the present invention.

Figures 6A and 6B are shown in Figure 4A or Figure 5A, respectively. FIG. 4 is an explanatory diagram for explaining a winding state of a sensor oscillation coil in the concentration meter according to the present invention.

7A and 7B are explanatory diagrams each showing a modified example of the sensor oscillation coil in the concentration meter according to the present invention.

8A and 8B are perspective views showing a modification of the sensor according to the embodiment of the present invention.

FIG. 9 is a perspective view showing a modification of the pointing / adjusting unit.

10A to 10E are characteristic diagrams showing measurement examples using the densitometer of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the densitometer according to the present invention will be described.

FIG. 1 is a schematic configuration diagram showing the appearance of a densitometer according to an embodiment of the present invention. In the figure, 1 is a meter, 2 is a power lamp, 3 is a power switch, 4 is a span volume, 5 is a zero-adjustment volume, 6 is a sensor as a concentration detector, 7 is a lead wire, and 8 is a measurement. The aqueous electrolyte solution to be used, such as hydrochloric acid or cassette.

In the measurement, first, the zero point is adjusted using the zero adjustment volume 5 in the air. Next, the sensor 6 is immersed or pressed against a standard solution having a standard conductivity or a calibration plate, and span adjustment is performed using a span volume unit 4. After calibration, set the sensor 6 in the aqueous electrolyte solution 8 to be measured. In this case, the sensor 6 is immersed in the electrolyte aqueous solution 8 at a depth of, for example, 4 O mm or more, and the liquid exists within a range of, for example, 30 to 40 mm around the tip thereof, and Dip so that a conductor such as metal does not come close to the area.

FIG. 2 is a block diagram showing a circuit configuration of a signal processing circuit for density detection in the present embodiment, where 11 denotes, for example, several MHz to several tens of MHz. An oscillation circuit having an oscillation frequency on the order of z, 12 is a coil, which is a circuit element of the oscillation circuit, is disposed inside the tip of the sensor 6, and 13 and 13 'are for power supply. And a lead line for transmitting a measurement signal, 14 is a detection circuit for detecting the oscillation state of the oscillation circuit 11, 15 is a comparison circuit for comparing the detected voltage signal with the reference voltage ref, 1

6 is a stabilized DC power supply that supplies a DC power supply to the detection circuit 14 and a reference voltage to the comparison circuit 15, and 17 is a zero-adjustment volume for adjusting the reference voltage to perform zero adjustment (Fig. 1 5) and 18 are span volumes (4 in Fig. 1) for adjusting the signal level of the comparison result to perform span adjustment, 19 is a DC amplifier, and 20 is for displaying the measurement results. It's a night.

As described in Fig. 1, when the sensor 6 incorporating the oscillation circuit 11 is immersed in the aqueous electrolyte solution 8 to be measured, the liquid approaches the coil 12 arranged at the liquid contact part at the sensor tip, The degree of contribution to the oscillation of the coil 12 changes based on the conductivity of the liquid 8, and as a result, the oscillation state of the oscillation circuit 1 changes. This change in the oscillation state causes a change in the power supply current supplied from the stabilized DC power supply 16 via the lead wires 13 and 13 ', and the change in the current is detected as a voltage by the detection circuit 14 Is done. The detection voltage is, for example, a comparison circuit composed of a differential amplifier.

15, where it is compared with a reference voltage r e f supplied separately from the stabilized DC power supply 16. Since this reference voltage is set to a voltage indicating zero by the above-mentioned zero adjustment in the air, the change in the oscillation state due to only the presence of the liquid 8 is detected by the comparison circuit 15. Become. The comparison result is sent to a meter 20 via a span volume 18 having a predetermined gain and a DC amplifier 19 having a predetermined level, and the concentration of the liquid 8 is displayed.

The circuit form of the oscillation circuit 11 is from several MHz to several tens M As long as oscillation at a high frequency of Hz is possible, any type such as a Colpitts type or a tray type may be used, and the temperature of the electrolyte aqueous solution 8 to be measured is not only room temperature but also 100%. Some of them reach several tens of degrees, and it is necessary to perform temperature compensation to ensure the measurement accuracy. Therefore, the oscillation circuit 11 is well known to other circuits as well. Temperature compensation circuit is attached.

FIG. 3 is a conceptual structural diagram showing a configuration of one embodiment of the sensor 6 in the concentration meter according to the present invention. Reference numeral 61 denotes, for example, a cylindrical body of vinyl chloride, and an oscillation circuit 11 is housed at the tip, that is, at the detection end, so that the oscillation coil 12 is located at the tip of the cylinder. Numeral 62 denotes a liquid-contacting part made of a front plate of vinyl chloride of the same material adhered to the tip of the cylindrical body 61, so that the inside of the cylindrical body 61 is sealed at least in a liquid-tight manner. It is sealed. 63 is a cable fixing device for fixing a shielded wire, and 64 is a shielded wire. The cylindrical body 61 has a diameter of about 20 to 40 O mm and a length of 200 to 100 O mm, and the tip is immersed in an aqueous electrolyte solution 8 to be measured. The rear end is gripped by the operator or attached to a holder for continuous measurement. In practice, the lead wires 13 and 13 ′ are formed by a shield wire that is continuous with the shield wire 64, and are fixed to the rear end of the sensor 6 by the cable fixture 63, and Even if an external force is applied to the wire 6 4, it is prevented from affecting the inside.

Although not shown in the above-described embodiment, in order to compensate for a change in the concentration value due to a change in the oscillation state of the oscillation circuit 11 due to the temperature of the electrolyte aqueous solution 8, the oscillation circuit 11 A temperature sensor is provided in close proximity to the sensor, and its detection output is taken out via a shielded wire 64 and transmitted to the comparison circuit 15 to increase the measurement accuracy by adjusting the concentration value to compensate. be able to. The oscillation circuit 11 is made of, for example, a compact printed circuit or an integrated circuit, and is further strengthened by being molded into the cylindrical body 61 with epoxy casting resin or the like. If fixed to, it is possible to prevent the relative state of the circuit elements from changing due to vibration or the like and the oscillation state from changing, thereby preventing the measurement accuracy from lowering. Needless to say, the oscillation coil 12 may have any shape and structure as long as the coil 12 can be electromagnetically coupled to the electrolyte aqueous solution 8 to be measured.

FIGS. 4A and 4B are an internal structural view and an external perspective view, respectively, showing an enlarged tip portion for illustrating the configuration of another embodiment of the sensor 6 in the densitometer according to the present invention. In the figure, 1 1 ′ and 1 2 ′ are an oscillation circuit and a coil equivalent to the oscillation circuit 11 and the coil 12 constituting the detection end in FIGS. 2 and 3, respectively. The oscillating circuit 11 'is composed of, for example, a compact printed circuit board or an integrated circuit in the form of a flat plate, and the coil 12' is, for example, a flat spiral having an outermost diameter of about 10 to 3 O mm. As shown in FIG. 4A, the coil is formed at one end of the plate-like oscillation circuit 11 ′, in parallel with the edge thereof, and with respect to the plate surface of the oscillation circuit 11 ′. They are joined with orthogonal directions. As shown in FIG. 4B, the oscillation circuit 11 ′ and the coil 12 ′ are molded and integrated with an epoxy casting resin 65 or the like to constitute a detection end of the sensor 6. In this case, the flat spiral coil 12 ′ is disposed so as to face the surface of the liquid contact portion 62 of the sensor 6.

The sensor 6 of the present embodiment configured as described above has a wide area and a very close proximity between the oscillation coil 12 ′ and the sample solution which is the aqueous electrolyte solution 8 (FIG. 1) to be measured. Since they face each other, the electromagnetic coupling between them is good, and the accuracy of the concentration measurement is therefore high. Can be increased.

FIGS. 5A and 5B are an internal structural view and an external perspective view, respectively, showing an enlarged tip portion for showing the configuration of still another embodiment of the sensor 6 in the densitometer according to the present invention. In the figure, reference numerals 1 1 "and 1 2" denote oscillation circuits and coils equivalent to the oscillation circuit 11 and the coil 12 constituting the detection end in FIGS. 2 and 3, respectively. As in the other embodiments described above, the oscillating circuit 11 "is formed, for example, in a flat plate shape from a compact printed circuit or an integrated circuit, and the coil 12" is formed, for example, from 10 to 10 mm in outermost diameter. It is formed into a flat spiral coil of about 3 Omm, and as shown in Fig. 5A, is connected to one end of the flat oscillation circuit 11 "so as to be parallel to the plate surface. The oscillation circuit 11 "and the coil 12" are molded by epoxy casting resin 6 or the like to form the detection end of the sensor 6 as shown in Fig. 5B. In this case, the plate-shaped spiral coil 12 "is molded and integrated so as to protrude from the end face of the cylindrical sensor 6, thereby forming a liquid contact part 6 2 '.

When the detection end of the sensor 6 configured as described above is immersed in the sample solution, the sample solution is the electrolyte solution to be measured 8 ( (Fig. 1) is present and faces the aqueous electrolyte solution 8 in a wider area and closer to those of the other embodiments described above. Is further improved, so that a more accurate concentration measurement can be performed.

The flat spiral coil 12 or 12 "shown in FIGS. 4A and 5A described above is formed by spirally winding a single conductive wire. It can also be formed by printing and wiring on a printed board using technology. Alternatively, for 1-2 ", a flat plate is preferable, and a plate with a distorted surface distorts the oscillation waveform to generate harmonics, which causes a reduction in detection sensitivity.

FIGS. 6A and 6B are explanatory diagrams for explaining the winding mode of the flat spiral coil 12 ′ or 12 ″ shown in FIG. 4A or 5A, respectively. There are two types of spiral coil windings, as shown in FIG. 6A and densely wound as shown in FIG. 6A and coarsely wound as shown in FIG. 6B. As described above, since the oscillation frequency of this sensor is a high frequency of several MHz to several tens of MHz as described above, the capacitance component that determines the oscillation frequency is determined by the oscillation circuit 1 1 ′ (1 1 ) And the positional relationship between it and the oscillating coil 12 '(1 2 ") are greatly restricted, and in practice, it cannot be reduced below a certain range. However, there are circumstances in which they can only have a limited range of values.

For this reason, in the case of the densely wound coil shown in FIG. 6A, increasing the number of windings and increasing the coil diameter will rather decrease the detection sensitivity. However, such a tightly wound coil has a wide measurement range since the concentration-to-detection output characteristics of the sample liquid are not easily saturated. Therefore, such a densely wound coil is preferably applied to a sensor having a small coil diameter, for example, a diameter of about 9 mm, and which needs to be elongated. Also, as shown in Fig. 6B, if the coil winding density is made coarser uniformly, the detection sensitivity is improved, but the concentration vs. detection output characteristics of the sample liquid easily saturates, and the The fixed range becomes narrow. Therefore, these coarsely wound coils can be used for a sample solution having a relatively low concentration and by increasing the coil diameter, thereby enabling highly sensitive measurement.

FIGS. 7A and 7B show a sensor for a densitometer according to the present invention. It is explanatory drawing which shows the modification of a vibration coil. The coil of this modification is formed in a ring shape, and the ring-shaped coil portion can be formed in a flat plate shape (FIG. 7A) or a tubular shape (FIG. 7B). Compared to the flat spiral coil shown in Figs. 4A and 5A, the coil of this example is equivalent to or more than the roughly wound coil shown in Fig. 6B. It has the advantage of high detection sensitivity and easy coil fabrication.

In each of the above-described embodiments, the cylindrical body 61 and the liquid contact part 62 are formed, for example, by molding and covering or surrounding with vinyl chloride, epoxy resin, or the like. For time-course measurement, a more heat-resistant material can be used. ₍ Also, the structure of the rear end of the sensor 6 is shown in a cylindrical shape (Fig. 1). Depending on the measurement target or measurement location, deformations are required, for example, as shown in Figures 8A and 8B. The structure used for measurement attached to the side is shown, and a flange 68 is provided at the rear of the sensor 6 to seal the inside of the tank and also support the sensor itself. B, in the middle of the piping The structure used to measure the concentration of the sample solution flowing in the pipe is shown. For example, as shown in FIG. A screw portion 69 is formed by attaching a screw.

In addition, the outer shape of the measuring instrument, which is the indicating / adjusting unit in which the meter 1 is mounted in the concentration meter of the present invention, is shown in FIG. Fig. 9 shows a case where a meter 1 and adjustment knobs 45 are arranged, but as shown in Fig. 9, it is intended to be attached to a control panel in an operation control room or the like in the manufacturing process. :.

The front panel 10 of the measuring instrument box 9 is formed in a shape that protrudes in a flange shape, and the front panel 10 is provided with an integral mounting member.Instruction on the control panel surface The structure can be as follows.

10A to 10E are characteristic diagrams showing measurement examples using the densitometer of the present invention. Fig. 1 OA shows the results of a wide range of measurements for various aqueous electrolyte solutions, and the maximum point appears in the middle concentration range for most of the sample solutions. It is shown that each of the sample liquids has a characteristic that monotonically increases in the range of 0 to 10 several wt%. Fig. 10B Fig. 10C, Fig. 10D and Fig. 10E show the characteristics of NaC1, HC1, ZnC12 and NaOH in the dilute concentration range, respectively. Is enlarged. Industrial applicability

As described above, according to the present invention, a compact, inexpensive densitometer capable of online measurement can be obtained. In addition, the metal electrode is not exposed at the detection end, and However, since there is no through hole in the measurement part like an electromagnetic densitometer, it has a very simple shape and is easy to handle.

Also, if heat-resistant materials are used for the liquid contact part and the cylindrical body, it is possible to measure the concentration of the sample liquid at a relatively high temperature from several tens of degrees to about 140 degrees. Continuous use is also possible.

Claims

The scope of the claims

1. A coil and a high-frequency oscillation circuit including the coil as an oscillating element are attached to the detection end of the concentration detector immersed in the sample solution which is an aqueous electrolyte solution, and the detector is immersed in the sample solution. A concentration meter that measures the concentration of the sample liquid by detecting a change in the oscillation state of the high-frequency oscillation circuit when the oscillation occurs.

2. In the densitometer according to claim 1,

A densitometer characterized in that at least a coil and a high-frequency oscillation circuit are integrated with a resin to form a detection end of a concentration detector immersed in a sample solution.

3. The densitometer according to claim 1 or 2, wherein the coil has a flat spiral shape.

4. The densitometer according to claim 3,

A densitometer characterized in that a flat spiral coil is disposed parallel to an end face of a detection end of a concentration detector immersed in a sample liquid.

5. The densitometer according to claim 3,

A densitometer characterized in that a flat spiral coil is disposed so as to protrude vertically from an end face of a detection end of a concentration detector immersed in a sample liquid.

6. The densitometer according to claim 1 or 2, wherein the coil has a ring shape.

7. The concentration meter according to any one of claims 1 to 6, wherein the concentration detector further includes a mounting member for sealing the inside of the device while attaching the device to the device containing the sample liquid. A densitometer that specializes in this.

8. The densitometer according to any one of claims 1 to 7, wherein Instructions for concentration measurement and instructions for adjustment · A box accommodating the adjustment unit, and a mounting member integrally formed on the front surface of the box for attaching the instruction · adjustment unit. Densitometer.