JP4028284B2 - Substance measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a substance measurement apparatus using a microwave that measures a physical quantity such as a concentration of an object to be measured by measuring a difference in propagation time or phase delay of the microwave.
[0002]
[Prior art]
Conventionally, as an instrument for measuring the concentration of suspended solids in a liquid, an ultrasonic concentration meter that measures the attenuation rate of ultrasonic waves to obtain the concentration, a transmitted light attenuation rate using light, an increase rate of scattered light, etc. An optical densitometer or the like that obtains a concentration by measurement is often used.
[0003]
However, in the ultrasonic densitometer, there is a problem that when air bubbles are mixed in the liquid, the measurement error increases due to the large influence. Further, in the latter optical densitometer, if dirt is attached to the optical window through which light is incident or received, the influence is greatly affected, and the measurement error also increases.
[0004]
Therefore, recently, a microwave densitometer has been developed and put into practical use as a densitometer that is hardly affected by bubbles and dirt.
[0005]
FIG. 4 is a block diagram showing a control configuration of the microwave densitometer. In the figure, a microwave transmitting antenna 2 and a microwave receiving antenna 3 are disposed in a pipe 1 through which a fluid flows so as to face each other in the diameter direction.
[0006]
A microwave transmitter 5 is connected to the microwave transmission antenna 2 via a power splitter 4, and microwaves are supplied from the microwave transmitter 5. The microwave receiving antenna 3 is connected to the concentration calculation circuit 7 via the propagation time measurement circuit 6. Further, the output side of the power splitter 4 is connected to the input side of the propagation time measuring circuit 6.
[0007]
Therefore, the microwave passing path is transmitted from the microwave transmitting antenna 2 via the power splitter 4, propagates the fluid in the pipe 1, is received by the microwave receiving antenna 3, and is introduced into the propagation time measuring circuit 6. There are two systems: a first path and a second path introduced from the power splitter 4 to the propagation time measurement circuit 6.
[0008]
The concentration calculation circuit 7 that has received the output from the propagation time measurement circuit 6 determines the propagation from 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 time difference or phase difference.
[0009]
In this microwave densitometer, the phase delay θ2 of the microwave propagating in the measurement substance in the pipe 1 with respect to the microwave directly received from the microwave transmitter 5 via the power splitter 4, and the pipe 1 A reference fluid, for example, tap water that can be regarded as having a zero concentration, is filled in and a microwave phase delay θ1 when measured under the same conditions as the measurement target liquid is compared. Then, from the phase difference Δθ = (θ2−θ1), the concentration of the liquid to be measured is obtained using the calibration curve 8 shown in FIG.
[0010]
Specifically, the concentration X of the liquid to be measured is obtained by performing calculation according to the following equation (1).
[0011]
X = aΔθ + b (1)
Note that a is the slope of the calibration curve, b is the intercept of the calibration curve, and normally b = 0.
[0012]
Actually, when measuring the concentration with a microwave densitometer, the phase is measured in advance by passing pure water as a reference first, and then measured by comparing with the reference phase through the substance to be measured. Is done.
[0013]
Such a conventional microwave densitometer is not a method of measuring the attenuation rate of the microwave, but a method of measuring the phase difference, and the window part for receiving or receiving the microwave needs to be transparent. There is no. For this reason, it has the advantage that it is hardly affected by bubbles and dirt and the concentration can be measured continuously.
[0014]
In such a microwave densitometer, the propagation time for concentration calculation is the length of the transmission cable 9 and the reception cable 10 from the microwave oscillating unit 5, the size and material of the members constituting the cable, and the like. It also changes depending on. However, these effects can be eliminated by making initial adjustments for each device.
[0015]
[Problems to be solved by the invention]
However, in this microwave densitometer, the phase indication may change or the measurement may become unstable due to factors other than those described above during concentration measurement.
[0016]
One of the causes is that gas in the substance to be measured flowing in the pipe 1, that is, bubbles or the like are accumulated in a specific part of the pipe 1, and the microwave measured by the microwave propagating through this part interferes. There is a problem that a measurement error occurs.
[0017]
In addition, similar problems occur due to accumulation of a substance to be measured at the bottom of the pipe 1, for example, sedimentation of sludge, adhesion to the inner wall of the pipe 1, and the like.
[0018]
Furthermore, the diameter of the pipe 1 has been increased recently, and when the transmitting and receiving antennas are fixed to the pipe wall as in the past, the propagation of the microwave is increased when the diameter of the pipe is increased to 300 mm or more. The distance increases and decays. In particular, when the fluid inside the pipe has conductivity, the attenuation of the microwave is significant and the sensitivity is lowered.
[0019]
An object of the present invention is to provide a substance amount measuring apparatus that does not attenuate microwaves even when the pipe diameter is increased and is not easily affected by bubbles, precipitates, and deposits in the pipe.
[0020]
[Means for Solving the Problems]
A substance amount measuring apparatus according to the present invention is a substance that measures a physical quantity of a substance to be measured from a propagation time or a phase delay of the microwave transmitted through the substance to be measured that is transmitted between the transmitting antenna and the receiving antenna. A quantity measuring device, a pipe for flowing a substance to be measured, a microwave transmission antenna supported by a support member installed in the pipe and installed in the substance to be measured, and the transmission antenna Opposite, the first receiving antenna of the support member installed at a position not easily affected by bubbles and deposits generated in the pipe, and the transmitting antenna, and the bubbles or deposits on the inner wall of the pipe A second receiving antenna installed at a position relatively susceptible to influence, and the support member has a distance from the transmitting antenna to the first receiving antenna and a second receiving antenna. In a positional relationship in which the distance to the antenna are equal to each other, characterized in that supporting the transmission antenna and the first receive antenna.
[0025]
In these inventions, at least the transmission antenna of the transmission antenna and the reception antenna constituting the microwave propagation path is installed in the fluid of the substance to be measured in the pipe by the support member, so the distance from the reception antenna is shortened. It is possible to measure the physical quantity accurately, and to detect the occurrence of bubbles, deposits, etc. that are likely to occur on the inner wall of the pipe.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a substance amount measuring apparatus according to the present invention will be described in detail with reference to the drawings.
[0027]
FIG. 1 is a schematic diagram showing a cross-sectional configuration inside a pipe in the present embodiment. This substance amount measuring apparatus measures a physical quantity of a substance to be measured in which a suspended matter such as sludge, paper pulp or the like, a coffee, a starch or the like is mixed, for example, a suspended substance concentration.
[0028]
In the figure, in a pipe 11 through which a 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 support member 14 and arranged opposite to each other in the substance to be detected. A propagation path (hereinafter referred to as a first microwave propagation path) is formed. The support member 14 is provided so as to intersect with the flow direction of the substance to be measured, and is formed in a bar shape or a plate shape from a metal or a high-strength synthetic resin or ceramic. Each antenna 12 and 13 has a normal configuration, but a monopole antenna may be used. These antennas 12 and 13 are each covered with a protective member 15 to protect them from the substance to be measured.
[0029]
As the protective member 15, a synthetic resin member that is not easily affected by property changes by the substance to be measured is used. A synthetic resin member that is not easily affected by this property change is a member made of a heat-resistant material that does not thermally deform within the temperature range of the substance to be measured, and is strong when the substance to be measured is acidic or alkaline. It is a member made of an acid resistant or alkaline resistant material.
[0030]
The circuit shown in FIG. 4 is connected to the first microwave propagation path by the transmitting antenna 12 and the first receiving antenna 13. That is, a microwave transmitter 5 is connected to the transmission antenna 12 via the power splitter 4, and a microwave is supplied from the microwave transmitter 5. The reception antenna 13 is connected to the concentration calculation circuit 7 via the propagation time measurement circuit 6. Further, the output side of the power splitter 4 is connected to the input side of the propagation time measuring circuit 6.
[0031]
Then, the phase delay θ2 of the microwave propagating in the substance to be measured in the pipe 1 with respect to the microwave input directly from the microwave transmitter 5 to the propagation time measuring circuit 7 via the power splitter 4; 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, the calibration curve 8 shown in FIG. 5 is used from the phase difference Δθ = (θ2−θ1). Obtain the concentration of the solution to be measured.
[0032]
As described above, the transmitting antenna 12 and the first receiving antenna 13 constituting the first microwave propagation path are attached to the support member 14 and installed in the substance to be measured flowing in the pipe 11. And the receiving antenna 13 can be arbitrarily set to an optimum value without being affected by the pipe diameter of the pipe 1.
[0033]
That is, in the structure in which the transmitting antenna 2 and the receiving antenna 3 are attached to the inner wall of the conventional pipe 1 shown in FIG. 4, since the facing distance between the antennas 2 and 3 is determined by the diameter of the pipe, the diameter is larger than 300 mm. Then, the facing distance between the antennas 2 and 3 becomes long, and the microwave is attenuated and the sensitivity is lowered.
[0034]
On the other hand, in the above embodiment, the transmitting antenna 12 and the first receiving antenna 13 are attached to the support member 14, so that the facing distance between the antennas 12 and 13 is not affected by the diameter of the pipe. , Can be set arbitrarily to the optimum value. For this reason, sufficient measurement sensitivity is maintained and high measurement accuracy is obtained.
[0035]
In addition, depending on the substance to be measured, it is conceivable that bubble accumulation occurs in the pipe, or substances accumulate or adhere to the inner wall of the pipe 11 due to long-term use or the like, thereby affecting the measurement performance. However, since these generation sites in the pipe 11 can be assumed in advance, the transmission antenna 12 and the first reception antenna 13 attached to the support member 14 should be installed at arbitrary positions avoiding the assumed generation site. Thus, these effects can be eliminated.
[0036]
For example, the bubble pool is concentrated on the top of the inside of the pipe 11, and the deposit is generated at the bottom of the pipe 11. That is, most of them occur at the portion of the pipe 11 that is in contact with the upper and lower inner wall surfaces, so the transmitting antenna 12 and the first receiving antenna 13 attached to the support member 14 are installed in the substance to be measured near the center of the cross section in the pipe 11. By doing so, it is possible to obtain a good measurement result without being substantially affected by bubbles, deposits, and deposits generated in the pipe 11.
[0037]
Furthermore, since the transmitting antenna 12 and the receiving antenna 13 are covered with the protective member 15 that is not easily affected by the property change caused by the substance to be measured, even if it is installed in the substance to be measured, The life of each antenna 12, 13 is significantly increased.
[0038]
In this embodiment, another receiving antenna 17 (hereinafter referred to as a second receiving antenna) is provided with respect to the transmitting antenna 12 to form a second microwave propagation path. The circuit shown in FIG. 4 is also connected to the second microwave propagation path by the transmitting antenna 12 and the second receiving antenna 17, and the physical quantity of the substance to be measured can be measured.
[0039]
Further, the distance from the transmission antenna 12 to the second reception antenna 17 is set equal to the distance from the first reception antenna 13. In this way, calculation for concentration measurement is facilitated.
[0040]
However, unlike the above-described first microwave propagation path, the second microwave propagation path is formed at a position that is relatively susceptible to the influence of bubbles, deposits, and the like generated in the pipe 11.
[0041]
That is, the first receiving antenna 13 and the transmitting antenna 12 are installed in the detected substance that is hardly affected by bubbles and deposits by the support member 14, but the second receiving antenna 17 is, for example, And installed on the inner wall of the top where air 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 varies greatly due to interference from the bubble accumulation.
[0042]
In the embodiment thus configured, first, the propagation time of the microwave in the first propagation path from the transmitting antenna 12 to the receiving antenna 13 through the substance to be measured (fluid) flowing in the pipe 11 is measured. To do. Similarly, the propagation time of the microwave in the second propagation path from the transmitting antenna 12 to the receiving antenna 17 through the substance to be measured in the pipe 11 is measured.
[0043]
The physical quantity, for example, the concentration of the substance to be measured is calculated from the propagation times of the microwaves in the two propagation paths. At this time, when there is no bubble accumulation in the pipe 11, the calculated concentration values are almost equal.
[0044]
However, when bubbles are generated in the pipe 11, a bubble pool is 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 bubble pool. That is, the microwave received by the second receiving antenna 17 is obstructed by the bubble accumulation, and the propagation time is delayed.
[0045]
On the other hand, the first receiving antenna 13 is disposed near the center of the cross section in the pipe 11, and even if bubbles are generated in the pipe 11, there is almost no bubble accumulation around them. Therefore, the propagation time of the microwave received by the first receiving antenna 13 is normal.
[0046]
As a result, the propagation time through the second microwave propagation path varies significantly compared to the propagation time through the first microwave propagation path that is not affected by the bubble accumulation. It is possible to immediately detect that bubble accumulation has occurred in the pipe 11 due to the fluctuation of the propagation time.
[0047]
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 bubble accumulation.
[0048]
In the above embodiment, the second receiving antenna 17 is provided on the top inner wall of the pipe 11, but it may be attached to the same support member 14 together with the transmitting antenna 12 and the first receiving antenna 13.
[0049]
In the above embodiment, the second antenna 17 is provided on the top inner wall in the pipe 11 in order to detect bubble accumulation generated in the pipe 11. Two antennas 17 may be provided on the bottom inner wall of the pipe 11.
[0050]
With this configuration, when a deposit is generated in the pipe 11, the measurement result by the second microwave propagation path varies greatly, so that the occurrence of the deposit can be detected immediately.
[0051]
Next, the embodiment shown in FIGS. 2 and 3 will be described. In addition, the same code | symbol is attached | subjected to the part corresponding to FIG.
[0052]
Also in this embodiment, the microwave transmission antenna 12 is attached to 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 transmission antenna 12 is installed at the center of the cross section of the pipe 11.
[0053]
The support member 14 is formed of a metal or a high strength synthetic resin or ceramic into a rod shape or a plate shape, and the transmission antenna 12 is covered with a protection member 15 and protected from a substance to be measured.
[0054]
The first receiving antenna 13 that forms the first microwave propagation path and the second receiving antenna 17 that forms the second microwave propagation path with respect to the transmission antenna 12 are located at different positions on the inner wall of the pipe 11. Provided.
[0055]
The first microwave propagation path is formed at a position that is not easily affected by bubbles or deposits generated in the pipe 11. In other words, the first receiving antenna 13 is installed at the lower right in the figure in the lower part of the pipe 11 where no bubble accumulation occurs so that deposits are difficult to accumulate.
[0056]
On the other hand, the second microwave propagation path is formed at a position that is relatively easily affected by bubbles and deposits generated in the pipe 11. That is, as shown in FIG. 3, the second receiving antenna 17 is installed on the top inner wall of the pipe 11 in which bubbles are likely to accumulate.
[0057]
The circuit shown in FIG. 4 is connected to the first microwave propagation path formed by the transmission antenna 12 and the first reception antenna 13 and the second microwave propagation path formed by the second reception antenna 17, respectively. The physical quantity of the substance to be measured can be measured respectively. Further, the distance between the receiving antennas 13 and 17 with respect to the transmitting antenna 12 is set to be equal to each other because the transmitting antenna 12 is disposed at the center of the cross section of the pipe 11.
[0058]
In the above configuration, in measuring the concentration of the substance to be measured, first, the propagation time of the microwave 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 measured. To do. Similarly, the propagation time of the microwave in the second propagation path from the transmitting antenna 12 to the receiving antenna 17 through the substance to be measured in the pipe 11 is measured.
[0059]
The concentration of the substance to be measured is calculated from the microwave propagation times in the two propagation paths. At this time, when there is no bubble accumulation in the pipe 11, the calculated concentration values are almost equal.
[0060]
However, if air bubbles are generated in the pipe 11, as shown in FIG. 3, a bubble pool is generated in the pipe 11 immediately below the inner wall where the second antenna 17 is installed. For this reason, the microwave received by the second receiving antenna 17 is obstructed by the bubble accumulation, and the propagation time is delayed.
[0061]
On the other hand, since the first receiving antenna 13 is installed on the inner wall surface of the pipe 11 at an oblique lower portion, there is almost no bubble accumulation around the first receiving antenna 13. Moreover, even if deposition occurs, it is not covered with deposits. Therefore, the propagation time of the microwave received by the first receiving antenna 13 is normal.
[0062]
As a result, the propagation time by the second microwave propagation path varies significantly compared to the propagation time by the first microwave propagation path. Due to this change in propagation time, it is immediately detected that bubble accumulation has occurred in the pipe 11.
[0063]
Needless to say, the concentration of the substance to be measured can be accurately measured by the first receiving antenna 13 which is not affected by bubble accumulation or deposits.
[0064]
【The invention's effect】
According to the present invention, the propagation distance of microwaves can be maintained in an appropriate range even when the pipe diameter is increased, and when bubbles, precipitates, and deposits are generated in the pipe, these are immediately detected. Therefore, accurate and stable measurement is possible.
[Brief description of the 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 for explaining the operation of the embodiment of FIG. 2;
FIG. 4 is a block diagram showing a control configuration of a conventional microwave densitometer.
FIG. 5 is a graph showing a calibration curve.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Piping 12 Microwave transmission antenna 13, 17 Microwave reception antenna 14 Support member

Claims (1)

A substance amount measuring device for measuring a physical quantity of a substance to be measured from a propagation time or a phase delay of the microwave transmitted through the substance to be measured that is transmitted between the transmitting antenna and the receiving antenna,
Piping for flowing the substance to be measured;
A microwave transmission antenna supported by a support member installed in the pipe and installed in the substance to be measured;
A first receiving antenna that is opposed to the transmitting antenna and is installed at a position on the supporting member that is not easily affected by bubbles and deposits generated in the pipe;
A second receiving antenna that faces the transmitting antenna and is installed at a position on the inner wall of the pipe that is relatively susceptible to the influence of the bubbles or deposits;
The support member supports the transmission antenna and the first reception antenna in a positional relationship in which a distance from the transmission antenna to the first reception antenna and a distance from the second reception antenna are equal to each other. Characteristic substance amount measuring device.

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