JP2003307502A - Substance quantity measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substance quantity measuring device causing no attenuation of a microwave even for a pipe with a large diameter, and being little affected by bubble, deposit and sticking matter in the pipe. <P>SOLUTION: Since at least a transmission antenna 12 is arranged in fluid by a measuring object substance in the pipe 11 by a support member 14 among the transmission antenna 12 and receiving antennas 13 and 17 for constituting a microwave propagation passage, a distance from the receiving antennas 13 and 17 can be shortened, and influence such as bubble reservoir and deposit easily generated in an inner wall part of the pipe 11 is reduced so that a physical quantity can be accurately measured. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave substance amount measuring apparatus for measuring a physical amount such as a concentration of an object to be measured by measuring a difference in propagation time or a phase delay of microwaves.

[0002]

2. Description of the Related Art Conventionally, as an instrument for measuring the concentration of a suspended substance in a liquid, an ultrasonic densitometer for determining the concentration by measuring the attenuation factor of an ultrasonic wave, or a transmitted light attenuation factor or scattering using light Optical densitometers and the like are often used to determine the density by measuring the rate of increase in light.

However, the ultrasonic densitometer has a problem that when air bubbles are mixed in the liquid, the influence of the air bubbles greatly affects the measurement error. Further, in the latter optical densitometer, when dirt adheres to the optical window that receives or receives light, the dirt is greatly affected and the measurement error also increases.

Therefore, recently, a microwave type densitometer has been developed as a densitometer which is hardly affected by bubbles and dirt.
It is becoming practical.

FIG. 5 is a block diagram showing the control arrangement of this microwave densitometer. In the figure, a microwave transmitting antenna 2 and a microwave receiving antenna 3 are arranged in a pipe 1 through which a fluid flows so as to face each other in a diametrical direction.

A microwave transmitter 5 is connected to the microwave transmitting antenna 2 via a power splitter 4, and a microwave is supplied from the microwave transmitter 5. Further, the microwave receiving antenna 3 is connected to the concentration calculating circuit 7 via the propagation time measuring circuit 6. Further, the output side of the power splitter 4 is connected to the input side of the propagation time measuring circuit 6.

Therefore, the microwave passage is transmitted from the microwave transmitting antenna 2 through the power splitter 4, propagates through the fluid in the pipe 1 and is received by the microwave receiving antenna 3, and is transmitted to the propagation time measuring circuit 6. There are two systems, the first route introduced and the second route introduced from the power splitter 4 to the propagation time measuring circuit 6.

The concentration calculation circuit 7, which receives the output from the propagation time measuring circuit 6, calculates the propagation time or phase delay of the microwave from the first path and the propagation time or phase delay of the microwave from the second path. , Find the difference in their propagation times or the phase difference.

In this microwave densitometer, the phase delay θ2 of the microwave propagating through the substance to be measured in the pipe 1 with respect to the microwave directly received from the microwave oscillator 5 via the power splitter 4 is obtained. A comparison is made with the phase delay θ1 of the microwave when the pipe 1 is filled with a reference fluid, for example, tap water that can be regarded as having a zero concentration and measured under the same conditions as the liquid to be measured. Then, the phase difference Δθ = (θ2
From -θ1), the concentration of the liquid to be measured is obtained using the calibration curve 8 shown in FIG.

Specifically, the concentration X of the liquid to be measured can be calculated by the following equation (1).

X = aΔθ + b (1) where a is the slope of the calibration curve, b is the intercept of the calibration curve, and usually b = 0.

Further, in actuality, in the concentration measurement by a microwave type densitometer, pure water as a reference is first passed through to measure the phase in advance, and then the measured substance is compared with the above reference phase. It is measured by

Such a conventional microwave densitometer is
This is not a method of measuring the attenuation rate of microwaves but a method of measuring a phase difference, and it is not necessary that the window portion that receives or receives microwaves be transparent. Therefore, it has an advantage that it is not easily affected by bubbles and dirt and that the concentration can be continuously measured.

In such a microwave densitometer,
The propagation time for calculating the concentration also changes depending on the lengths of the transmission cable 9 and the reception cable 10 from the microwave oscillating unit 5, the size and material of the members forming the cable, and the like. However, it is possible to eliminate the influence on the measurement by making an initial adjustment for each device.

[0015]

However, in this microwave densitometer, when measuring the concentration, there are cases where the indication of the phase changes or the measurement becomes unstable due to factors other than the above.

One of the causes is that the gas in the substance to be measured flowing in the pipe 1, that is, bubbles or the like is accumulated in a specific portion of the pipe 1 and the microwave measured by the microwave propagating in this portion is generated. There is a problem of being interfered with and causing a measurement error.

The same problem also occurs due to the accumulation of the substance to be measured at the bottom of the pipe 1, for example, the sludge settling, the adhesion to the inner wall of the pipe 1, and the like.

Further, recently, the diameter of the pipe 1 is becoming larger, and when the transmitting and receiving antennas are fixed to the wall surface of the pipe as in the conventional case, if the diameter of the pipe becomes larger than 300 mm, the micro The propagation distance of the wave becomes long and attenuates. In particular, when the fluid inside the pipe has conductivity, the microwave is significantly attenuated and the sensitivity is lowered.

It is an object of the present invention to provide a substance amount measuring apparatus in which microwaves are not attenuated even when the diameter of the pipe is increased, and which is not easily affected by bubbles, precipitates and deposits in the pipe.

[0020]

A substance amount measuring device according to the present invention as set forth in claim 1 transmits a microwave from a transmitting antenna and transmits a microwave from a substance to be measured located between the transmitting antenna and the receiving antenna. A physical quantity of a substance to be measured is measured from a propagation time or a phase delay, which is supported by a pipe for flowing the substance to be measured and a supporting member installed in the pipe, and which is predetermined in the substance to be measured. It is characterized by comprising a microwave transmitting antenna and a microwave transmitting antenna which are arranged to face each other while keeping a distance.

According to a second aspect of the present invention, there is provided a microwave transmitting antenna which is supported by a pipe for flowing a substance to be measured and a support member installed in the pipe and which is installed in the substance to be measured. And a microwave receiving antenna attached to the inner wall of the pipe.

According to a third aspect of the present invention, there is provided a microwave transmitting antenna which is supported by a pipe for flowing a substance to be measured and a support member installed in the pipe and which is installed in the substance to be measured. And a first receiving antenna that is installed at a position facing the microwave transmitting antenna and is not easily affected by bubbles or deposits generated in the pipe, and facing the transmitting antenna, and is affected by the bubbles or deposits. And a second receiving antenna installed at a position relatively easy to receive.

The present invention according to claim 4 is characterized in that the first and second receiving antennas are attached to the supporting member together with the transmitting antennas.

The present invention according to claim 5 is characterized in that the first receiving antenna is attached to the support member together with the transmitting antenna, and the second receiving antenna is attached to the inner wall of the pipe.

The present invention according to claim 6 is characterized in that the first and second receiving antennas are mounted at different positions on the inner wall of the pipe.

The present invention according to claim 7 is characterized in that the distance between the transmitting antenna and the first and second receiving antennas is the same.

According to the present invention of claim 8, the supporting member is formed of metal, synthetic resin having high strength, ceramic or the like.

In these inventions, at least the transmitting antenna among the transmitting antenna and the receiving antenna which constitute the microwave propagation path is installed in the fluid of the substance to be measured in the pipe by the supporting member, so that the receiving antenna The distance can be shortened, and the influence of bubbles, deposits, etc., which are likely to occur on the inner wall of the pipe, is reduced, and the physical quantity can be measured accurately.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a substance amount measuring apparatus according to the present invention will be described below with reference to FIG.

FIG. 1 is a schematic diagram showing a cross-sectional structure of the inside of the pipe in the present embodiment. This substance amount measuring device,
The physical quantity of the substance to be measured, for example, the concentration of the suspended matter, which is mixed with the suspended matter such as fibrous substances such as sludge and paper pulp, coffee, and starch, is measured.

In the figure, a transmission antenna 12 forming a microwave propagation path is formed in a pipe 11 through which a substance to be detected flows.
Also, a state in which the receiving antenna 13 is arranged so as to face each other is shown. A monopole antenna is used as the transmitting antenna 12 and the receiving antenna 13. Each of these antennas 12 and 13 is attached to a support member 14 provided inside the pipe 11 so as to intersect the flow direction of the substance to be measured. The support member 14 is formed of a metal, a synthetic resin having high strength, or a ceramic in a rod shape or a plate shape.

Transmitting antenna 12 and receiving antenna 13
Are covered with a protective member 15 and are protected from the flow of the substance to be measured. As the protective member 15, a synthetic resin member that is not easily affected by the property change due to the substance to be measured is used. The synthetic resin member that is not easily affected by this property change is a member made of a heat resistant material that is not thermally deformed in the temperature range of the measured substance, and when the measured substance is acidic or alkaline, it is strong. A member made of an acid-resistant or alkali-resistant material.

The circuit configurations for the transmitting antenna 12 and the receiving antenna 13 are basically the same as those shown in FIG. That is, the microwave antenna 5 is connected to the transmitting antenna 12 via the power splitter 4, and the microwave is supplied from the microwave oscillator 5. The receiving antenna 13 is also connected to the concentration calculating circuit 7 via the propagation time measuring circuit 6. Further, the output side of the power splitter 4 is connected to the input side of the propagation time measuring circuit 6.

Then, the phase delay of the microwave propagating through the substance to be measured in the pipe 1 with respect to the microwave input directly from the microwave oscillator 5 to the propagation time measuring circuit 7 via the power splitter 4. θ2 is compared with the phase delay θ1 of the microwave when the pipe 1 is filled with the reference fluid and measured under the same conditions, and the phase difference Δθ = (θ2--
From θ1), the concentration of the liquid to be measured is obtained using the calibration curve 8 shown in FIG.

Here, in the above-mentioned embodiment, the transmitting antenna 12 and the receiving antenna 1 which constitute the microwave propagation path.
Since 3 is attached to the support member 14 and installed in the substance to be measured flowing in the pipe 11, the facing distance between the transmitting antenna 12 and the receiving antenna 13 can be arbitrarily set to an optimum value.

That is, in the structure shown in FIG. 5 in which the transmitting antenna 2 and the receiving antenna 3 are attached to the inner wall of the conventional pipe 1, the facing distance between the antennas 2 and 3 is determined by the diameter of the pipe, and therefore the diameter is 300 mm. When it is larger than the above, the facing distance between the antennas 2 and 3 becomes long, the microwave is attenuated, and the sensitivity is lowered.

On the other hand, in the above embodiment, the transmitting antenna 12 and the receiving antenna 13 are attached to the supporting member 14, so that the facing distance between the antennas 12 and 13 is not affected by the diameter of the pipe. , Can be arbitrarily set to the optimum value. Therefore, sufficient measurement sensitivity can be maintained and high measurement accuracy can be obtained.

Further, it is considered that depending on the substance to be measured, air bubbles may be generated in the pipe, or the substance may be deposited or adhered to the inner wall of the pipe 11 due to long-term use or the like, which may affect the measurement performance. To be However, since these generation sites in the pipe 11 can be assumed in advance, the support member 14
These influences can be eliminated by installing the transmitting antenna 12 and the receiving antenna 13 attached to the above-mentioned apparatus at arbitrary positions avoiding the assumed generation site.

For example, the bubble pool is concentrated on the top of the pipe 11, and the deposit is generated on the bottom of the pipe 12. That is, since most of them are generated in the portions in contact with the upper and lower inner wall surfaces of the pipe 11, if the transmitting antenna 12 and the receiving antenna 13 attached to the supporting member 14 are installed in the substance to be measured near the center of the cross section in the pipe 12, A good measurement result can be obtained with almost no influence of air bubbles, deposits, and adherents generated in the pipe 12.

Further, since the transmitting antenna 12 and the receiving antenna 13 are covered with the protective member 15 which is not easily affected by the property change due to the substance to be measured, even if the substance to be measured is installed in the substance to be measured. The antennas 12 and 13 are reliably protected from damage and the life of each antenna 12 and 13 is significantly extended.

In the above embodiment, the transmitting antenna 12 and the receiving antenna 13 forming the microwave propagation path are attached to the supporting member 14, respectively. However, only the transmitting antenna 12 is attached to the supporting member, and the receiving antenna 13 is
It may be attached to the inner wall of the pipe 11. At this time, the position of the inner wall to which the receiving antenna 13 is attached may be, for example, an obliquely lower portion where it is difficult for bubble accumulation and deposits to occur.

Even with this configuration, the antennas 12 and 1
The facing distance between the three is not affected by the diameter of the pipe,
Since it can be arbitrarily set to the optimum value, sufficient measurement sensitivity can be maintained and high measurement accuracy can be obtained. Further, it is possible to obtain a good measurement result without being substantially affected by bubbles, deposits, and adhered substances generated in the pipe 12.

Next, the embodiment shown in FIG. 2 will be described.
The parts corresponding to those in FIG. 1 are designated by the same reference numerals.

Also in this embodiment, as in the case of FIG.
In a pipe 11 through which the substance to be measured flows, a transmitting antenna 12 and a receiving antenna (hereinafter, referred to as a first receiving antenna) 13 are attached to a supporting member 14 and are arranged to face each other in the substance to be detected, and a microwave propagation path ( Hereinafter, the first microwave propagation path) is formed. The support member 14 is also formed in a rod shape or a plate shape from metal, high-strength synthetic resin, or ceramic. The antennas 12 and 13 are not monopole antennas as shown in FIG. 1 but have a normal structure. However, as in the case of FIG.
Each is covered with a protective member 15 to protect it from the substance to be measured.

The first microwave propagation path formed by the transmitting antenna 12 and the first receiving antenna 13 is shown in FIG.
The circuit shown by is connected, and the physical quantity of the substance to be measured can be measured. In this case, similar to the device of FIG. 1, a high measurement accuracy can be obtained without being affected by the diameter of the pipe 11, and almost no influence of bubbles, deposits, and adhered substances generated in the pipe 11 is obtained. Good measurement results are obtained.

In this embodiment, in addition to the transmitting antenna 12, another receiving antenna 17 (hereinafter,
A second receiving antenna) is provided to form a second microwave propagation path. These transmitting antenna 12 and the second
The circuit shown in FIG. 5 is also connected to the second microwave propagation path by the receiving antenna 17 of FIG. 5, and the physical quantity of the substance to be measured can be measured.

The distance between the transmitting antenna 12 and the second receiving antenna 17 is set equal to the distance between the transmitting antenna 12 and the first receiving antenna 13. In this way, the calculation for measuring the concentration becomes easy.

However, this second microwave propagation path is
Unlike the first microwave propagation path described above, the piping 1
It is formed at a position relatively susceptible to the influence of air bubbles, deposits, etc. generated inside 1.

That is, the first receiving antenna 13 is installed together with the transmitting antenna 12 by the support member 14 in the substance to be detected which is hardly affected by bubbles and deposits, but the second receiving antenna 17 is provided. Is installed on the inner wall of the top where bubbles generated in the pipe 11 gather. Therefore, when bubbles are generated in the pipe 11, the measurement result by the second microwave propagation path is greatly changed due to the interference due to the bubble pool.

In this embodiment thus configured, first, the first microwave propagation path, that is, the substance to be measured (fluid) flowing in the pipe 11 from the transmitting antenna 12 to the receiving antenna 13 is reached. The propagation time of the microwave in the propagation path 1 is measured. Similarly, the second microwave propagation path, that is, the second microwave from the transmitting antenna 12 to the receiving antenna 17 through the substance to be measured in the pipe 11.
The propagation time of the microwave in the propagation path of is measured.

From the propagation times of the microwaves in these two propagation paths, the physical quantity of the substance to be measured, for example, the concentration, is calculated. At this time, when there is no bubble accumulation in the pipe 11, the calculated concentration values are almost equal.

However, when air bubbles are generated in the pipe 11, air bubbles are generated at the top of the pipe 11, that is, immediately below the inner wall where the second antenna 17 is installed, and the second receiving antenna 17 is affected by the air bubbles. Receive. That is, the microwave received by the second receiving antenna 17 is obstructed by the bubble reservoir and the propagation time thereof is delayed.

On the other hand, the first receiving antenna 13 is connected to the pipe 1
It is arranged near the center of the cross section in 1, and even if bubbles are generated in the pipe 11, there is almost no accumulation of bubbles around it. Therefore, the propagation time of the microwave received by the first receiving antenna 13 is normal.

As a result, the propagation time of the second microwave propagation path fluctuates significantly as compared with the propagation time of the first microwave propagation path which is not affected by the bubble accumulation. Due to this change in the propagation time, the bubble pool is
The occurrence within 1 can be immediately detected.

At this time, the concentration of the substance to be measured can be accurately measured by the first receiving antenna 13 which is not affected by the accumulation of bubbles.

In the above embodiment, the second receiving antenna 17 is provided on the inner wall of the top of the pipe 11, but it may be attached to the same supporting member 14 together with the transmitting antenna 12 and the first receiving antenna 13.

Further, in the above embodiment, the second antenna 1 is used in order to detect the bubble accumulation generated inside the pipe 11.
Although 7 is provided on the inner wall of the top of the pipe 11, the second antenna 17 may be provided on the inner wall of the bottom of the pipe 11 when the generation of deposits is detected.

According to this structure, when a deposit is generated in the pipe 11, the measurement result by the second microwave propagation path changes greatly, so that the occurrence of the deposit can be immediately detected.

Next, the embodiment shown in FIGS. 3 to 4 will be described. The parts corresponding to those in FIGS. 1 and 2 are designated by the same reference numerals.

Also in this embodiment, the microwave transmitting antenna 12 has the support member 14 in the pipe 11.
And is installed in the substance to be measured in the pipe 11. In this embodiment, the transmitting antenna 12 is installed at the center of the cross section of the pipe 11.

The support member 14 is made of metal, synthetic resin or ceramic having high strength, and is formed in a rod shape or a plate shape.
It is covered with and is protected from the substance to be measured.

With respect to this transmitting antenna 12, a first receiving antenna 13 forming a first microwave propagation path,
The second receiving antennas 17 forming the second microwave propagation path are provided at different positions on the inner wall of the pipe 11.

The first microwave propagation path is formed at a position where it is unlikely to be affected by bubbles and deposits generated in the pipe 11. That is, the first receiving antenna 13 is installed in the lower portion of the pipe 11 where bubble accumulation does not occur and in the diagonally lower right in the figure where deposits are hard to deposit.

On the other hand, the second microwave propagation path is formed at a position relatively susceptible to the influence of bubbles and deposits generated in the pipe 11. That is, as shown in FIG. 4, the second receiving antenna 17 is installed on the inner wall of the top of the pipe 11 where the bubble reservoir 18 is likely to occur.

The first microwave propagation path by the transmitting antenna 12 and the first receiving antenna 13 and the second microwave propagation path
The circuits shown in FIG. 5 are connected to the second microwave propagation paths formed by the receiving antenna 17 and the physical quantity of the substance to be measured, respectively. Also, both receiving antennas 13 and 1 with respect to the transmitting antenna 12
The transmission antenna 12 is located at the center of the cross section of the pipe 11, and thus the distance to 7 is set equal to each other.

In the above structure, in measuring the concentration of the substance to be measured, first, the propagation of microwaves in the first propagation path from the transmitting antenna 12 through the substance to be measured flowing in the pipe 11 to the receiving antenna 13 is conducted. Measure time. Similarly, the propagation time of the microwave in the second propagation path from the transmitting antenna 12 through the substance to be measured in the pipe 11 to the receiving antenna 17 is measured.

The concentration of the substance to be measured is calculated from the propagation times of the microwaves in these two propagation paths.
At this time, when there is no bubble accumulation in the pipe 11, the calculated concentration values are almost equal.

However, when bubbles are generated in the pipe 11, as shown in FIG. 4, a bubble pool 18 is formed in the pipe 11 immediately below the inner wall on which the second antenna 17 is installed. Therefore, the microwave received by the second receiving antenna 17 is obstructed by the bubble reservoir, and the propagation time thereof is delayed.

On the other hand, the first receiving antenna 13 is connected to the pipe 1
Since it is installed on the inner wall surface of the diagonally lower part of 1, there is almost no bubble accumulation around it. Further, even if the accumulation occurs, it is not covered with the deposit. Therefore, the propagation time of the microwave received by the first receiving antenna 13 is normal.

As a result, the propagation time of the second microwave propagation path fluctuates significantly as compared with the propagation time of the first microwave propagation path. Due to this change in propagation time, it is immediately detected that a bubble pool has occurred in the pipe 11.

Of course, the concentration of the substance to be measured is not affected by the bubble pool 18 or the deposits.
3 allows accurate measurement.

[0072]

According to the present invention, the microwave propagation distance can be kept within an appropriate range even if the diameter of the pipe is increased.
In addition, even if air bubbles, precipitates, or deposits occur in the pipe,
It is difficult to be affected by these, and accurate and stable measurement is possible.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of a substance amount measuring apparatus according to the present invention.

FIG. 2 is a schematic diagram showing another embodiment of the present invention.

FIG. 3 is a schematic diagram showing still another embodiment of the present invention.

FIG. 4 is a schematic diagram illustrating the operation of the embodiment of FIG.

FIG. 5 is a block diagram showing a control configuration of a conventional microwave densitometer.

FIG. 6 is a graph showing a calibration curve.

[Explanation of symbols]

11 piping 12 microwave transmitting antenna 13,17 Microwave receiving antenna 14 Support members 18 Bubble puddle

Claims (8)

[Claims] 1. A microwave is transmitted from a transmitting antenna,
A substance quantity measuring device for measuring a physical quantity of a measured substance from a propagation time or a phase delay of a microwave propagating through the measured substance, which is located between a receiving antenna and a pipe for flowing the measured substance, 1. A substance amount measuring apparatus, comprising: a microwave transmitting antenna and a receiving antenna, which are supported by a supporting member installed in a pipe and are arranged to face each other in the substance to be measured with a predetermined distance therebetween. 2. A microwave is transmitted from a transmitting antenna,
A substance quantity measuring device for measuring a physical quantity of a measured substance from a propagation time or a phase delay of a microwave propagating through the measured substance, which is located between a receiving antenna and a pipe for flowing the measured substance, A microwave transmitting antenna, which is supported by a supporting member installed in a pipe and is installed in the substance to be measured, and a microwave receiving antenna, which is attached to an inner wall of the pipe. Quantity measuring device. 3. A microwave is transmitted from a transmitting antenna,
A substance quantity measuring device for measuring a physical quantity of a measured substance from a propagation time or a phase delay of a microwave propagating through the measured substance, which is located between a receiving antenna and a pipe for flowing the measured substance, A microwave transmitting antenna that is supported by a supporting member that is installed in the pipe and that is installed in the substance to be measured, and is opposed to the microwave transmitting antenna and is not easily affected by bubbles or deposits generated in the pipe. A first receiving antenna installed at a position, and a second receiving antenna installed at a position facing the transmitting antenna and relatively easily affected by the bubbles or the deposits, Measuring device for substance quantity. 4. The substance amount measuring device according to claim 3, wherein the first receiving antenna is attached to the supporting member together with the transmitting antenna, and the second receiving antenna is attached to the inner wall of the pipe. 5. The substance amount measuring apparatus according to claim 3, wherein the first and second receiving antennas are attached to the supporting member together with the transmitting antenna. 6. The substance amount measuring device according to claim 3, wherein the first and second receiving antennas are attached to the inner wall of the pipe at different positions from each other. 7. The substance amount measuring apparatus according to claim 3, wherein the microwave transmitting antenna and the first and second receiving antennas have the same distance from each other. 8. The amount of substance according to claim 1, wherein the support member is formed of metal, high strength synthetic resin, ceramic or the like. measuring device.