JP4304197B2 - Substance measuring device - Google Patents

Description

  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.

  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.

  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.

  Therefore, recently, a microwave densitometer has been developed and put into practical use as a densitometer that is hardly affected by bubbles and dirt.

  FIG. 3 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.

  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.

  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.

  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.

  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.

  Specifically, the concentration X of the liquid to be measured is obtained by performing calculation according to the following equation (1).

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.

  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.

  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.

  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.

  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.

  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.

  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.

  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.

  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.

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 transmitting antenna supported in a supporting member installed in the pipe and installed in the substance to be measured, and a transmission antenna A first receiving antenna and a second receiving antenna which are installed on the inner wall of the pipe so as to be able to receive the transmitted microwaves, and one of the first receiving antenna and the second receiving antenna is provided; Place the other location in the pipe where microwaves are likely to be generated, and the other location in the pipe where microwaves and deposits are less likely to be generated. Further, the distance from the transmitting antenna to the first receiving antenna and the distance from the second receiving antenna are set to be equal to each other.

  In the present invention, among the transmitting antenna and the receiving antenna constituting the microwave propagation path, the transmitting antenna is installed in the fluid of the substance to be measured in the pipe by the support member, so that the distance from the receiving antenna is shortened. In addition, the influence of bubbles and deposits that are likely to occur on the inner wall of the pipe is reduced, and the physical quantity can be measured accurately.

  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 even if bubbles, precipitates, and deposits are generated in the pipe, they are affected by these. Difficult, accurate and stable measurement is possible.

  Hereinafter, an embodiment of a substance amount measuring apparatus according to the present invention will be described in detail with reference to the drawings.

  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. In the embodiment of FIG. 1, in such a pipe 11 through which a substance to be measured flows, a microwave transmission antenna 12 and a reception antenna 13 are arranged to face each other in the substance to be detected to form a microwave propagation path. .

  Here, the transmitting antenna 12 is attached to a support member 14 provided so as to intersect with the flow direction of the substance to be measured, and is disposed in the substance to be treated, for example, at the center of the cross section of the pipe 11 as illustrated. ing. The support member 14 is formed in a rod shape or a plate shape from a metal or high strength synthetic resin or ceramic.

  On the other hand, the receiving antenna 13 is attached to the inner wall of the pipe 11. The position of the inner wall to which the receiving antenna 13 is attached may be, for example, a portion of the pipe 11 that is inclined downward in the figure, in which bubble accumulation and deposits are unlikely to occur. That is, depending on the substance to be measured, bubble accumulation occurs in the pipe, or the substance accumulates or adheres to the inner wall of the pipe 11 due to long-term use. These may affect measurement performance. Since these generation sites in the pipe 11 can be assumed in advance, the reception antenna 13 is installed at an arbitrary position avoiding the assumed generation site with respect to the transmission antenna 12 attached to the support member 14. This can eliminate these effects.

  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 are generated in a portion in contact with the upper and lower inner wall surfaces of the pipe 11, so that the receiving antenna 13 may be installed in the lower portion of the pipe 11 in the drawing as described above, for example. If installed in this way, good measurement results can be obtained without being substantially affected by bubbles, deposits, and deposits generated in the pipe 11.

  Each antenna 12 and 13 has a normal configuration, but a monopole antenna may be used.

  Here, the transmitting antenna 12 is covered with a protective member 15 to protect it from the substance to be measured. 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.

  The circuit shown in FIG. 3 is connected to the microwave propagation path by the transmitting antenna 12 and the 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.

  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. 4 is used from the phase difference Δθ = (θ2−θ1). Obtain the concentration of the solution to be measured.

  In this embodiment, the transmitting antenna 12 constituting the first microwave propagation path is installed in the substance to be measured flowing in the pipe 11 and the receiving antenna 13 is installed on the inner wall of the pipe 11. The facing distance between the antenna 12 and the receiving antenna 13 can be arbitrarily set to an optimum value without being influenced by the pipe diameter of the pipe 11.

  That is, in the structure shown in FIG. 3 where the transmitting antenna 2 and the receiving antenna 3 are both mounted on the inner wall of the conventional pipe 1 so as to face each other, the facing distance between the antennas 2 and 3 is determined by the diameter of the pipe. For this reason, when the diameter is increased to 300 mm or more, the facing distance between the antennas 2 and 3 becomes longer, the microwaves are attenuated, and the sensitivity is lowered.

  On the other hand, in the above embodiment, the transmitting antenna 12 is attached to the support member 14 and installed in the substance to be measured, so that the facing distance between the antennas 12 and 13 is not affected by the diameter of the pipe. It can be set arbitrarily to the optimum value. For this reason, sufficient measurement sensitivity is maintained and high measurement accuracy is obtained.

  In addition, as described above, the receiving antenna 13 is installed in a portion of the pipe 11 that is obliquely below the figure, for example, so that the receiving antenna 13 is hardly affected by bubbles, deposits, and deposits generated in the pipe 11. Measurement results can be obtained.

  In this embodiment, another receiving antenna 17 (hereinafter, the receiving antenna 13 is referred to as a first antenna and the receiving antenna 17 is referred to as a second receiving antenna) is provided with respect to the transmitting antenna 12. Two microwave propagation paths are formed. The circuit shown in FIG. 3 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.

  However, this second microwave propagation path is different from the first microwave propagation path composed of the transmission antenna 12 and the first reception antenna 13 described above, and is affected by bubbles or deposits generated in the pipe 11. It is formed at a relatively easy position.

  In other words, the first receiving antenna 13 is installed in a portion of the pipe 11 that is hardly affected by bubbles and deposits, but the second receiving antenna 17 is, for example, in the pipe 11. Installed on the top inner wall where the generated bubbles 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.

  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.

  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.

  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.

  However, when air bubbles are generated in the pipe 11, as shown in FIG. 2, 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. Influenced by accumulation. That is, the microwave received by the second receiving antenna 17 is obstructed by the bubble accumulation, and the propagation time is delayed.

  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.

  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.

  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.

  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.

  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.

It is a schematic diagram which shows one Embodiment of the substance amount measuring apparatus by this invention. It is a schematic diagram explaining the operation | movement of embodiment of FIG. It is a block diagram which shows the control structure of the conventional microwave type densitometer. It is the graph which showed the 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 transmitting antenna supported by a support member installed in the pipe and installed in the substance to be measured;
A first receiving antenna and a second receiving antenna installed on the inner wall of the pipe so as to be able to receive the microwave transmitted from the transmitting antenna;
One of the first receiving antenna and the second receiving antenna is located at a position where a microwave propagation path is likely to be generated in the pipe, and the other is a microwave in which bubbles and deposits are not easily generated in the pipe. The substance amount measuring apparatus , wherein the distance from the transmitting antenna to the first receiving antenna and the distance from the second receiving antenna are set to be equal to each other .

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