JPH07209228A - Concentration meter - Google Patents

Abstract

PURPOSE:To provide a small-sized concentration meter excellent in withstand voltage, corrosion resistance and heat resistance. CONSTITUTION:The concentration meter comprises a detection sensor 6 having a coil 11 loaded to the forward end part immersed into an electrolyte aqueous solution and a connecting wire 7 connected with the coil 11 and being led out to the rear end part, and a high frequency oscillation circuit 13 connected with the led-out end of the connecting wire 7 and employing the coil 11 as an oscillation element. When the sensor 6 is immersed into an electrolyte aqueous solution, the variation in the oscillating state of the high frequency oscillation circuit 13 is detected 14 to 20 thus measuring the concentration of electrolyte aqueous solution. In the detection sensor 6, the coil 11 and the connecting wire 7 are integrally formed out of a material having at least corrosion resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid concentration meter, and more particularly to a concentration meter for measuring the concentration of an aqueous electrolyte solution containing ions.

[0002]

2. Description of the Related Art In the industrial fields such as chemical industry, food manufacturing, semiconductor manufacturing, etc., an aqueous solution of an electrolyte such as caustic soda and hydrochloric acid is used for a chemical treatment or a cleaning, and the concentration is within a predetermined concentration or within a predetermined concentration range. Is used. Also, in air-conditioning equipment such as buildings and factories, especially in absorption refrigerators, Li
An absorbing solution consisting of an aqueous electrolyte solution such as Br has been used. As these electrolyte aqueous solutions, 0.1 wt%
It is necessary to use a relatively high concentration of several wt% or several tens of wt%, and there is something that requires caution in handling, such as being dangerous to the human body due to its strong chemical reaction with acids and alkalis. In many cases, as in the case of treatment in a mass production plant or air conditioning equipment, it is necessary to continuously supply an electrolyte aqueous solution having a predetermined concentration at such a high concentration for a long time.

To continuously control the concentration of such a high-concentration electrolyte solution, a technique such as titration takes too much time and labor, and moreover, a production control system or an automatic air-conditioning system using a recent computer is required. Since there is a need to adapt it, there is a demand for an online concentration measuring means. A so-called electromagnetic densitometer has been conventionally used as a densitometer in such a high concentration range. The electromagnetic densitometer measures conductivity by immersing a superposed annular transformer for transmission and detection in a sample solution and utilizing electromagnetic induction current flowing in the solution passing through the through hole. The concentration measurable range is several tens wt%.
There is also, and online concentration measurement is possible,
There is a problem that it is large in size, difficult to handle, and expensive.

[0004] Therefore, the applicant of the present invention, in order to obtain a concentration meter that is capable of online concentration measurement, is small and easy to handle, and is inexpensive, A coil and a high-frequency oscillation circuit including the coil as an oscillating element are attached to the detection end of a concentration detector immersed in a sample, and the oscillation state of the high-frequency oscillation circuit changes when the detector is immersed in the sample solution. It proposes a new densitometer configured to measure the concentration of a sample liquid by detecting (see International Application PCT / JP93 / 01816 based on Japanese Patent Application No. 4-334619).
issue).

In the densitometer according to this proposal, when the detection end portion is immersed in the electrolyte aqueous solution to be measured, the electroconductive electrolyte aqueous solution is electromagnetically coupled with the coil to oscillate the oscillation circuit in the detector. It utilizes the fact that the conditions are affected and that the current supplied to the oscillation circuit changes in accordance with the electrical conductivity of the aqueous electrolyte solution and thus the concentration. Then, in order to enhance the measurement sensitivity without being affected by disturbance or noise, the detection end portion is configured to incorporate a coil and a high frequency oscillation circuit.

As a result, it is small and inexpensive and can be applied to online measurement. In addition, the metal electrode is not exposed at the detection end, and the measurement portion is penetrated unlike the conventional electromagnetic densitometer. Since there were no holes, it was possible to obtain a densitometer that had an extremely simple shape and was easy to handle. Also,
By forming the detector including the detection end into a tubular shape and using a heat-resistant material for the tubular body, it is possible to measure the concentration of a relatively high temperature sample liquid from several tens of degrees to approximately 140 degrees. It is also possible to use it continuously for a long time.

[0007]

In practical use of the densitometer according to the above-mentioned proposal, for example, when an aqueous electrolyte solution is sealed under a vacuum in a relatively thin pipe like an absorption solution in an absorption refrigerator, A relatively small-sized facility may be used as in the semiconductor manufacturing process, and there is a demand for a more compact densitometer with excellent pressure resistance. In addition, since the electrolyte aqueous solution to be measured is generally highly corrosive and is often used at relatively high temperatures, it is further excellent in corrosion resistance and heat resistance in order to enhance the durability and reliability of equipment. A densitometer is needed.

Therefore, the present invention is to further improve the densitometer according to the above proposal, and to provide a densitometer that is smaller in size, excellent in pressure resistance, and has higher corrosion resistance and heat resistance. And

[0009]

The densitometer according to the present invention comprises:
A coil attached to the coil that is attached to the tip and the coil that is connected to the coil that is immersed in the electrolyte aqueous solution, and that has a built-in connection line for pulling out to the rear end, and the coil that is connected to the extraction end of the connection line. And a high-frequency oscillation circuit that uses as an oscillating element, and is configured to measure the concentration of the aqueous electrolyte solution by detecting a change in the oscillation state of the high-frequency oscillation circuit when the detection sensor is immersed in the aqueous electrolyte solution. It

The detecting sensor is formed by integrating the coil and the connecting wire with at least a material having corrosion resistance. In the densitometer according to the present invention, a coil of a flat plate type can be used, and the coil is disposed parallel to the liquid contact surface at the tip of the detection sensor immersed in the aqueous electrolyte solution, or Are arranged parallel to the length direction of the sensor. In the latter case, the detection sensor can be formed by integrating the flat-plate spiral coil and the connecting wire into a flat plate by using at least a material having corrosion resistance. A ring-shaped coil can be used instead of the flat-plate spiral coil. Further, the connecting wire may be a coaxial cable or may be two wires arranged side by side.

[0011]

According to the above structure, since the detection sensor has only the coil and the connecting wire built therein, it can be formed in a small size, and since it does not have any built-in circuit element such as an oscillation circuit, it has a high temperature. It is possible to measure the electrolyte aqueous solution. Further, in addition to corrosion resistance, it can be integrated with a material having high heat resistance and high pressure resistance, and a detection sensor having excellent corrosion resistance, heat resistance, and pressure resistance can be obtained.

[0012]

EXAMPLES Examples of the densitometer according to the present invention will be described below. FIG. 1 is a schematic configuration diagram showing the appearance of a densitometer that is 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 concentration detection sensor, 7
Is a coaxial cable, 8 is an electrolyte aqueous solution to be measured, and 10 is a densitometer main body. The zero adjustment volume 5 is for zero point adjustment performed by placing the sensor 6 in the air before measurement, and the span volume 4 is for span adjustment performed using a calibration plate or a standard solution after zero point adjustment. It is for.

FIG. 2 is a block diagram showing the circuit configuration of a signal processing circuit for density detection in this embodiment. In the figure, 6 and 7 are the sensor and the coaxial cable in FIG. 1, respectively, 11 is an oscillation coil arranged inside the tip of the sensor 6, and 13 is, for example, several MH.
An oscillation circuit having an oscillation frequency on the order of z to several tens of MHz, 14 is a detection circuit for detecting the oscillation state of the oscillation circuit 13, 15 is a comparison circuit for comparing the detected voltage signal with the reference voltage ref, and 16 is a detection circuit. A stabilized DC power supply that supplies a DC power supply to the circuit 14 and a reference voltage to the comparison circuit 15, 17 is a zero-adjustment volume (5 in FIG. 1) for adjusting the reference voltage, and 18 is a comparison. A span volume (4 in FIG. 1) for adjusting the resulting signal level to perform span adjustment, 19 is a DC amplifier, and 20 is a meter for displaying the measurement result. The coaxial cable 7 forms a connection line for high-frequency coupling between the coil 11 and the oscillator circuit 13.
Reference numeral 2 is an impedance matching device between the coil 11 and the coaxial cable 7, which is provided as necessary.

In use, when the sensor 6 containing the coil 11 is immersed in the electrolyte aqueous solution 8 to be measured, the liquid approaches the coil 11 arranged at the wetted portion at the tip of the sensor, and the conductivity of the liquid 8 Based on coaxial cable 7
Then, the degree of contribution to the oscillation of the coil 11 changes, and as a result, the oscillation state of the oscillation circuit 13 changes. This change in the oscillation state of the oscillation circuit 13 causes a change in the power supply current supplied from the stabilized DC power supply 16, and the current change is detected by the detection circuit 14 as a voltage. The detected voltage is supplied to a comparison circuit 15 including, for example, a differential amplifier, and is compared there with a reference voltage ref that is separately supplied from the stabilized DC power supply 16. Since the reference voltage is set to a voltage indicating zero by the zero point adjustment in the air described above, the comparison circuit 15 detects the change in the oscillation state due to only the presence of the liquid 8. The comparison result is supplied to the meter 20 through the span volume 18 and the DC amplifier 19 which are span-adjusted to a predetermined level and have a predetermined gain, and the concentration of the liquid 8 is displayed.

The circuit form of the oscillation circuit 11 may be any type such as Colpitts type or Hartley type as long as it can oscillate at a high frequency of several MHz to several tens of MHz. If it is necessary to detect the temperature of the electrolyte aqueous solution 8 to be measured, the temperature sensor can be incorporated in the sensor 6. FIG. 3 is a conceptual configuration diagram showing two configuration examples of the densitometer according to the present invention, and the reference numerals in the figure indicate the same components as those in FIGS. 1 and 2. 3A shows a first configuration example in which the oscillating circuit 13 to the meter 20 in FIG. 2 are incorporated in the densitometer main body 10, and this configuration example is the sensor 6
It can be adopted when the densitometer main body 10 and the densitometer main body 10 can be arranged relatively close to each other. The distance between the sensor 6 and the densitometer body 10, that is, the coil 11 and the oscillating circuit 13 is 1 to 2 m. If the distance is further than that, the oscillation is stopped, the sensitivity is lowered, and the induction around the coaxial cable is performed. Noise cannot be ignored.

FIG. 3B shows a second configuration example in which the oscillator circuit 13 is separated from the densitometer main body 10 and the densitometer main body 10 can be arranged at a relatively distant position.
In this configuration example, the oscillator circuit 13 is arranged at an appropriate position within the range of 1 to 2 m from the rear end of the sensor 6 as described above, but the densitometer main body 10 has the ordinary shielded wire 21.
Can be placed in a distant position using
Since the shielded wire 21 only needs to transmit the DC component, it is hardly affected by noise.

The structure of the detection coil provided in the sensor of the densitometer according to the present invention may be any structure and shape as long as it can be electromagnetically coupled with the electrolyte aqueous solution to be measured. From the viewpoint of downsizing the sensor and improving the measurement sensitivity, a spiral or annular sensor is preferable. FIG. 4 is a conceptual configuration diagram showing a specific example of the coil structure in the preferred embodiment of the densitometer according to the present invention. FIG. 4A shows an arrangement example of the spiral coil in the sensor. The spiral coil 11 is arranged so as to face the liquid contact surface at the tip of the sensor 6, and the sensor 6 is shown by a dotted line. It becomes a cylindrical shape. Since the coil of this example can face and approach the aqueous electrolyte solution to be measured and can approach, the electromagnetic coupling between the two can be improved and the measurement accuracy can be improved.

FIG. 4B shows another arrangement example.
The spiral coil 11 is arranged parallel to the length direction of the sensor 6 ', and the sensor 6'can be formed in a flat plate shape as shown by a dotted line. Since the coil of this example can face and approach the electrolytic solution to be measured on both sides of the coil, the electromagnetic coupling between the two can be further improved, and the measurement accuracy can be further improved.

FIGS. 4C and 4D show winding modes of the spiral coil, which are a tightly wound coil and a coarsely coiled coil, respectively. As described above, the oscillation frequency of the oscillation circuit is a high frequency of several MHz to several tens of MHz, and the winding mode of the coil greatly affects the oscillation condition. That is, in the case of the densely wound coil shown in FIG. 4C, if the number of windings is increased and the coil diameter is increased, the detection sensitivity is rather lowered.
However, such a coil tightly wound has a wide measurement range because the concentration vs. detection output characteristics of the sample liquid is unlikely to be saturated. Therefore, it is preferable to apply such a densely wound coil to a sensor in which the coil diameter needs to be reduced and the coil needs to be elongated. Further, as shown in FIG. 4 (B), when the coil winding density is made coarser uniformly, the detection sensitivity is improved, but the concentration of the sample liquid versus the detection output characteristic is easily saturated. , The measuring range becomes narrow. Therefore, these coarsely wound coils can be used for high-sensitivity measurement by increasing the coil diameter for a sample liquid having a relatively low concentration.

FIGS. 4 (E) and 4 (F) show a concrete example of a ring-shaped coil as a modified example of the coil.
Each of the ring-shaped coil portions has a flat plate type and a tubular shape. The coil of this example can be used in place of the above-mentioned spiral coil, and when compared with the spiral coil, the coil is equivalent to or more than that roughly wound as shown in FIG. 4 (D). It has the advantages of having detection sensitivity and facilitating the manufacture of the coil.

FIG. 5 is a conceptual configuration diagram showing the structure of a specific example of the sensor in the densitometer according to the present invention. For example, a coil as shown in FIG. It shows the case where they are arranged. In this example, the sensor 6 is integrally formed in a cylindrical shape by surrounding the coil and the coaxial cable 7 with vinyl chloride, epoxy resin, or the like by a mold, for example, and has a small diameter of 20 mmφ and a length of 20 to 100 mm. Sensor is obtained. Further, since it is surrounded by a resin or the like, it is possible to obtain the corrosion resistance, heat resistance, and pressure resistance necessary for continuous measurement for a long time in an electrolyte aqueous solution of relatively high temperature and / or high pressure.

The structure of the mounting portion of the sensor 6 is shown in FIG. 5 (A), for example, in the mounting portion provided in the middle of the pipe in order to measure the concentration of the electrolyte aqueous solution flowing in the pipe. An example is shown in which a threaded portion 62 having a taper is formed so as to be mounted while sealing the inside. Further, FIG. 5B shows a flange portion for sealing the inside of the tank and also supporting the sensor itself in order to measure the concentration of the electrolyte aqueous solution in the tank or the like by mounting it on the upper portion or the side portion of the tank. An example in which 63 is provided is shown. At the rear end of the sensor 6, a cylindrical rear end 61 (which may be formed in a flat plate shape) is provided at the rear end of the sensor 6 to facilitate the protection and handling of the coaxial cable 7, if necessary. It is provided as an extension.

FIG. 6 is a conceptual block diagram showing the structure of another specific example of the sensor in the densitometer according to the present invention. For example, a coil as shown in FIG. It shows a case where they are arranged in parallel with. Also in this example, as in the example of FIG. 5, the coil 6 and the coaxial cable 7 are surrounded by a resin or the like and integrated to form a sensor 6 ′, for example, a width of 20 mm and a length of 20 to 20 mm.
It is possible to obtain a sensor 6 ′ having a flat plate shape of 100 mm and a small size. Since the sensor 6'of the present example is also surrounded by the resin or the like, it is possible to obtain the corrosion resistance, heat resistance, and pressure resistance necessary for continuous measurement for a long time with respect to an electrolyte aqueous solution of relatively high temperature and / or high pressure. As a structure of the mounting portion, an example in which a tapered screw portion 62 is formed is shown in FIG. 6 (A), and a flange portion 63 is provided in FIG. 6 (B). An example is given. A cylindrical or flat plate-shaped rear end portion 61 is extendedly provided at the rear end of the sensor 6, if necessary.

In the preferred embodiment of the densitometer of the present invention described above, the coil and the oscillating circuit are connected by a coaxial cable. However, if both are arranged with a relatively short distance, the coaxial cable is connected. The sensor can be formed without using. FIG. 7 is a conceptual configuration diagram showing a modified example of the sensor in the densitometer according to the present invention for forming such a simple sensor. In this modification,
Connection wire portion 71 that connects the coil 11 and the oscillation circuit 13
However, for example, two 1 mmφ enameled wires are formed side by side by bonding or the like over the entire wire, so to speak, two parallel wires are formed. As the enamel wire, various kinds of wire such as a conventional oil-based enamel copper wire and formal copper wire as well as a synthetic enamel copper wire having high heat resistance can be used.

FIGS. 7A and 7B show the structure of a sensor having a coil arrangement similar to that of FIGS. 4A and 4B, for example, the coil 11 and the connecting wire portion 7.
1 and the oscillation circuit 13 are integrally surrounded and fixed by a resin or the like as in the case of FIG. 4, and are formed into a cylindrical sensor and a flat sensor, respectively. Although not shown in particular, as shown in FIG. 5 or 6, a sensor mounting screw or flange can be provided on the outside of the sensor integrally formed of resin. In that case,
The oscillation circuit 13 can be embedded in the rear end portion 61 shown in FIG. 5 or FIG. 6, for example.

In this modification, the distance between the coil and the oscillation circuit is 1 although there is a slight decrease in sensitivity as compared with the case where the connecting wire portion 71 is formed of a coaxial cable.
In the range of 00 to 500 mm, almost the same measurement sensitivity can be obtained, and the impedance matching device between the coil and the oscillation circuit shown in FIG. 2 is unnecessary or the impedance mismatch between them is not required. The loss due to matching can be eliminated, and the sensor manufacturing can be simplified and the cost can be reduced.

A specific example of the sensor in the above-described densitometer according to the present invention is as shown in FIGS.
Although integrally formed of vinyl chloride or epoxy resin, the sensor in the densitometer according to the present invention includes a coil, a coaxial cable or a connecting wire such as the above-mentioned parallel two wires, and a temperature sensor if necessary. However, it can be easily sealed with, for example, glass or ceramics. By using such a material having high corrosion resistance, heat resistance, and pressure resistance, a sensor having more excellent corrosion resistance, heat resistance, and pressure resistance can be obtained. For example, if the above-mentioned parallel two wires that are not covered with a flexible resin are used as the connecting wires and integrally formed of such a material having high heat resistance, the heat resistance limit can be increased to about 200 ° C.

FIG. 8 is a characteristic diagram showing an example of measurement by the densitometer of the present invention, showing the results of measurement over various electrolyte aqueous solutions. As is clear from this characteristic diagram, a maximum point appears in most of the electrolyte aqueous solution in the intermediate concentration range, and it varies depending on the type of solution, but it is almost 0.
It shows a characteristic that monotonically increases or decreases in the low concentration range of 10 to several wt% and the relatively high concentration range of 20 to 90 wt%, and effective concentration measurement is possible in this range.

From the above detailed description, it is apparent that the densitometer according to the present invention described in the claims has the following embodiments. 1. The densitometer according to the claims, wherein the coil has a flat-plate spiral shape. 2. Item 1. 2. The densitometer according to claim 1, wherein the flat spiral coil is arranged parallel to the liquid contact surface at the tip of the detection sensor immersed in the aqueous electrolyte solution. 3. Item 1. The densitometer according to claim 1, wherein the flat spiral coil is arranged in parallel with the length direction of the detection sensor. 4. Item 3 above. 2. The densitometer according to claim 1, wherein the flat-plate spiral coil and the connecting wire are integrated into a flat plate by at least a material having corrosion resistance to form a detection sensor. 5. The densitometer according to claim 1, wherein the coil has a ring shape. 6. Claims and the preceding clause 1. Through 5. The densitometer according to paragraph 1, wherein the connecting wire is a coaxial cable. 7. Claims and the preceding clause 1. Through 5. The densitometer according to claim 1, wherein the connecting wire is formed by arranging two conducting wires in parallel.

[0030]

As described above, according to the present invention,
It is extremely small and has a structure with good pressure resistance.
It is also possible to obtain an inexpensive densitometer that is excellent in corrosion resistance and heat resistance, is easy to handle with an extremely simple shape, and has the advantage of enabling online measurement.

If a material having high heat resistance is used as the material surrounding the sensor, it is possible to measure the concentration of the electrolyte aqueous solution at a relatively high temperature up to about 200 ° C., and further, it is possible to continuously use it for a long time. .

[Brief description of drawings]

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

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

FIG. 3 is a conceptual configuration diagram showing two configuration examples of the densitometer according to the present invention.

FIG. 4 is a conceptual configuration diagram showing a specific example of a coil structure in a preferred embodiment of the densitometer according to the present invention.

FIG. 5 is a conceptual configuration diagram showing a structure of a specific example of a sensor in the densitometer according to the present invention.

FIG. 6 is a conceptual configuration diagram showing the structure of another specific example of the sensor in the densitometer according to the present invention.

FIG. 7 is a conceptual configuration diagram showing a modified example of the sensor in the densitometer according to the present invention.

FIG. 8 is a characteristic diagram showing an example of measurement by the densitometer of the present invention.

[Explanation of Codes] 1 ... Meter 2 ... Power lamp 3 ... Power switch 4, 18 ... Span volume 5, 17 ... Zero adjustment volume 6, 6 '... Sensor 7 ... Coaxial cable 8 ... Electrolyte aqueous solution to be measured 10 ... Concentration meter Main body 11 ... Oscillation coil 12 ... Impedance matching device 13 ... Oscillation circuit 14 ... Detection circuit 15 ... Comparison circuit 16 ... Stabilizing DC power supply 19 ... DC amplifier 20 ... Meter 61 ... Rear end 62 ... Tapered screw 63 ... Flange 71 ... Connection line

Claims (2)

[Claims] 1. A coil attached to a front end portion immersed in an aqueous electrolyte solution, a detection sensor which is connected to the coil and has a built-in connecting wire for pulling out at a rear end portion, and a lead wire for the connecting wire. A high frequency oscillation circuit connected to the end and using the coil as an oscillation element; and by detecting a change in the oscillation state of the high frequency oscillation circuit when the detection sensor is immersed in an aqueous electrolyte solution. A densitometer for measuring the concentration of the aqueous electrolyte solution. 2. The densitometer according to claim 1, wherein the coil and the connecting wire are integrated by at least a material having corrosion resistance to form a detection sensor.