JP4794931B2 - Measuring system - Google Patents

Description

  The present invention relates to the measurement of the flow velocity, water level, and flow rate of a fluid flowing in an open channel (for example, a sewer pipe).

  Several proposals have been made for a flow meter for measuring the flow rate in the open channel and a method for measuring the average flow velocity of the flowing water. The prior art will be described below.

In Patent Document 1 (Patent No. 2119012), a flow rate measurement device comprising a water level meter and a current meter installed at the bottom of a sewage pipe or the like is used to calculate the average flow velocity value of the running water and calculate the measured water level. A flow rate measurement method has been proposed in which the area is multiplied by this average flow velocity value to measure the flow rate flowing in the sewer pipe.
FIG. 10 shows the embodiment. The surface of the flowing water flowing from the right hand to the left hand in the sewer pipe 111 is shown at 112. The flow velocity sensor 101 is installed at a height S from the tube bottom by the sensor holder 115.
FIG. 11 shows the internal structure of the flow velocity sensor 101. This sensor has a truncated pyramid shape so that the tip does not disturb the flow. In the flow velocity sensor 101, a flow meter 102 and a water level meter 103 using electromagnetic induction are provided. The water level meter is composed of a diaphragm 103a that bends at a pressure corresponding to the level of running water and a strain gauge 103b that detects the deflection of the diaphragm. A preamplifier 104 amplifies the signal.

FIGS. 12A and 12B are cross-sectional views of the sewer pipe 111. As can be seen from this figure, the cross-sectional area of the flowing water can be obtained from the shape / dimension (for example, diameter D) of the pipe and the water level (H) of the flowing water.
Moreover, 113 in the figure has shown the example of the flow velocity distribution of in-pipe water. The flow velocity distribution shows various distributions depending on “pipe gradient”, “pipe roughness”, and the like. Here, the “roughness of the pipe” is a characteristic inherent in each sewer pipe in which the flow velocity changes due to various factors such as the smoothness of the inner wall of the pipe, the bending of the pipe, and the depression.
Further, the flow velocity and flow velocity distribution in the pipe are different depending on the height of the water surface 112 as shown in FIG. 12 (a) or FIG. 12 (b).

FIG.13 and FIG.14 is the figure (patent document 2) which showed the relationship between the flow velocity (horizontal axis) and the water level (vertical axis) corresponding to the characteristic of each pipe | tube. In FIG. 13, for example, when the water level in the pipe is 10 inches, the flow velocity at each water level is indicated by a curve with a symbol of 10. The curves 7, 5, 3, and 2 are lines representing the flow velocity at each water level when the water level is 7 inches to 2 inches. This data shows the relationship between water level and flow velocity in “low gradient / high roughness” pipes. In other words, it is the relationship between the water level and the flow velocity in a place where the slope of the pipe is low or where the “roughness of the pipe” is high.
The water level indicated by S on the vertical axis is the distance from the tube bottom at the position where the anemometer is installed. That is, in this example, the anemometer is provided at a location 1 inch from the tube bottom. The flow velocity actually measured by the anemometer is the flow velocity indicated by the □ mark on each curve.

FIG. 14 is a diagram showing the relationship between the water level and the flow velocity in the pipe characteristic “high gradient / low roughness” different from FIG. 13. That is, it is the relationship between the water level and the flow velocity at a place where the slope of the pipe is higher than that of the pipe of FIG.
For example, comparing both FIG. 13 and FIG. 14 with a line marked 10, in FIG. 13, the flow velocity near the water surface was approximately 3 feet / second, whereas in FIG. Seconds. That is, if the gradient of the pipe becomes high or the roughness of the pipe becomes low, the flow velocity flowing on the surface is greatly different even at the same water level.
The water level indicated by S on the vertical axis is a distance (1 inch) from the tube bottom at the position where the anemometer is installed as in FIG.
Also in FIG. 14, the flow velocity value input from the running water sensor 101 installed in the sewer pipe is the flow velocity indicated by the □ mark on each curve.

  On the other hand, as described above, in order to calculate the flow rate of the flowing water flowing in the pipe, it is obtained by multiplying the cross-sectional area of the flowing water by the average flow velocity. In order to obtain the average flow velocity from the measured flow velocity indicated by the arrow S in FIGS. 13 and 14, Patent Document 1 describes a technique for obtaining the additional coefficient α by a predetermined mathematical expression.

On the other hand, Patent Document 2 (Patent No. 3202992) proposes a self-calibrating flow meter that measures the flow rate of running water by converting the measured water level from the water level meter and the measured flow rate from the velocimeter to an average flow rate. Yes.
Specifically, by analyzing the relationship between the local flow velocity (measured by an anemometer) at a specific site, which varies depending on the dimensions, gradient, tube roughness, etc. of the specific tube, and the measured water level from the water level meter, the measured flow velocity Is a method for obtaining a flow coefficient for converting the flow rate into an average flow velocity.
The obtained flow coefficient is stored in the storage means, and a predetermined flow coefficient is selected from the installation location of the anemometer, the measured flow velocity value, and the measured water level value, the average flow velocity is calculated, and the flow rate is measured.
Japanese Patent No. 2119012 Japanese Patent No. 3202992

In the prior arts disclosed in Patent Documents 1 and 2, the flow velocity and the water level are both measured, and the average flow velocity is obtained from the measured flow velocity and water level.
However, the average flow velocity and the water level have a one-to-one correlation within the open channel where the pipe environment is constant, such as the pipe gradient and the state of the pipe wall. That is, the average flow rate does not increase while the water level remains constant, and if the average flow rate increases, the water level increases correspondingly.
Further, in a normal case, what can be measured is a flow velocity at a predetermined position where an anemometer is installed, and it is necessary to obtain an average flow velocity from this measured flow velocity. In fact, since the fluid flowing in the pipe has a predetermined flow velocity distribution, the correlation between the actually measured flow velocity and the average flow velocity is affected by the position of the flow velocity in the pipe where the anemometer measures. In other words, when the flow velocity distribution is known, the average flow velocity can be calculated from the measured flow velocity if the position of the anemometer is known.

Conventionally, it has been difficult to memorize the infinite piping environment, the correlation between the flow velocity and the water level according to the installation environment of the anemometer, the correlation between the measured flow velocity and the average flow velocity, and the like.
However, in recent years, accurate flow velocity distribution can be predicted by development of storage means and analysis technology, and it is also possible to store many correlation curves in a measuring instrument.
Therefore, if the piping environment and sensor installation environment are stored in the device in advance, and the correlation curve is selected after the piping and sensor are installed, accurate fluid conditions can be measured without using complicated measurement means and calculation means. .
An object of the present invention is to provide a measurement system that realizes accurate measurement with simple measurement means and calculation means. In addition, multiple correlation curves do not need to be set in the same way, and can be set in a way that suits each condition. Even if a part of a specific correlation curve is modified, The correction can prevent the adverse effect.

A first aspect of the present invention is a measurement system for measuring a flow velocity, a water level, and a flow rate of a fluid flowing through an open channel without blocking the flow of the fluid, a flow rate sensor installed in the open channel , and a pipe Means for storing a plurality of flow velocity-water level correlation curves according to the environment and the installation environment of the flow velocity sensor, and means for recognizing one flow velocity-water level correlation curve selected according to the piping environment and the installation environment of the flow velocity sensor A flow rate measurement value from the flow rate sensor and a means for obtaining a calculated water level from the selected flow rate-water level correlation curve, and the flow rate-water level correlation curve is obtained in advance from the shape, size, gradient, and pipe of the open channel. It is a measurement system characterized by roughness, a flow velocity-water level correlation curve obtained by simulation calculation from the installation position of the flow velocity sensor .

A second aspect of the invention, a water level sensor, means for comparing and means for calculating the difference between the actual measurement level and calculates water level measured by the water level sensor and a preset threshold value and the absolute value of the difference a measuring system, characterized in that it comprises, means for transmitting an alarm signal when the absolute value of the difference is greater than a threshold.

According to a third aspect of the present invention , there is provided a measurement system comprising: means for storing pipe dimensions; and means for calculating a flow rate from the pipe dimensions and the calculated water level.

According to a fourth aspect of the present invention, the flow velocity sensor is a force sensor that measures a drag force caused by a velocity pressure of flowing water.

According to a fifth aspect of the present invention, the force sensor calculates the difference in stress between the first and second pressure receiving portions facing each other in the flow direction of flowing water in the open channel and the first and second pressure receiving portions by FBG ( 1. A drag measurement device for flowing water comprising a load mechanism that transmits to a fiber Bragg grating, an FBG that detects a difference in stress transmitted from the load mechanism, and an airtight chamber that houses the load mechanism and the FBG. It is a measurement system characterized by being a sensor that transmits a resistance value due to pressure) as an optical signal.

A sixth aspect of the present invention is a measurement system characterized in that the flow velocity-water level correlation curve includes a conversion correction value from a measured drag measured by a force sensor.

  According to the present invention, an appropriate single flow velocity-water level correlation curve can be selected from a plurality of flow velocity-water level correlation curves stored in advance, so that the initial setting is simple. Further, since the water level can be calculated only by collating the flow velocity measurement value with the flow velocity-water level correlation curve, the calculation process is simple and contributes to the improvement of the calculation speed. Furthermore, since no other special measuring means is required, it contributes to cost reduction.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 shows an example of a measurement system for obtaining the fluid level from the flow velocity measurement value of the flow velocity sensor according to the first embodiment of the present invention.
FIG. 1 shows a situation in which flowing water flows from the left to the right in the sewage pipe 41. A flow velocity value is sent from a flow velocity sensor 1 installed at the bottom of the tube via a cable 31 to a measurement system (not shown) according to the present invention. As will be described later, the water level up to the water surface 42 is calculated from the actually measured flow velocity value from the flow velocity sensor.
30 is a water level meter installed in the vicinity of the flow velocity sensor. By further installing a water level gauge, it becomes possible to transmit a warning signal or the like of a water level abnormality.

  FIG. 2 is a diagram showing the relationship between the flow rate of flowing water flowing through the open channel and the water level. The horizontal axis represents the flow velocity (m / s), and the vertical axis represents the water level (m). Curves 1 to 9 show the relationship between the flow velocity and the water level in the piping environments S1 to S3 in each of the flow velocity sensor installation environments E1 to E3.

Here, the flow velocity sensor installation environment means an installation position of the flow velocity sensor in the pipe described above. That is, since the fluid in the pipe has a flow velocity distribution, depending on the installation position of the flow velocity sensor, when the measured flow velocity coincides with the average flow velocity, it may become faster when it is delayed by a predetermined amount.
Therefore, when the water level is obtained from the measured flow velocity, it is necessary to determine the correlation with the installation position of the flow velocity sensor in advance. This is realized by selecting a correlation curve according to the sensor installation environment from a plurality of correlation curves.

The water level also varies depending on the piping environment. The piping environment means, for example, the shape of the pipe, the roughness of the pipe (flow resistance), and the gradient. For example, even if the installation environment of the flow velocity sensor is the same E1,
When the piping environment is different, a correlation from S1 to S3 can be assumed. Obtaining the correlation between the measurement flow rate and the water level is realized by selecting any correlation curve from S1 to S3 according to the actual piping installation environment. As a result, for example, if the correlation curve 4 is selected, the water level H1 can be calculated from the flow velocity measurement value V1. Similarly, when the correlation curve 7 is selected, the water level H2 can be calculated from the flow velocity measurement value V1.

The setting method of the flow velocity sensor installation environment and the flow velocity-water level correlation curve will be described.
In general, the relationship between the flow rate and the water level of flowing water flowing through the open channel has different characteristics depending on the shape, size, roughness of the tube, and the gradient of the tube. However, if limited to a particular tube environment, there is a certain correlation between the flow velocity and the water level in that environment.

In the present invention, for example, a plurality of levels of flow velocity sensor installation environments are set, and the flow velocity-water level correlation curve in each is obtained in advance by simulation calculation using another computer.
Several methods are conceivable for the simulation calculation by other computers. For example, the flow velocity distribution of the channel cross section can be derived by the finite volume method, and the water level and the average flow velocity can be obtained. Here, the finite volume method is a method of solving the movement of the entire flow by dividing the fluid into minute regions and calculating the entry / exit and force of the object in each minute flow region.
Next, a method for selecting one correlation curve from a plurality of correlation curves will be described.
When selecting the correlation curve, the flow velocity and water level at a plurality of positions may be temporarily measured at the actual flow velocity sensor installation site, and calculation may be performed based on the gradient of the tube, the friction of the inner wall of the tube, and the like. Further, the shape of the tube, the roughness of the tube, and the gradient of the tube may be directly measured.

(Second Embodiment)
On the other hand, the actual water level can be obtained from the water level gauge 30 by further installing the water level gauge 30 in the vicinity of the flow velocity sensor 1 in FIG. This measured water level is compared with the calculated water level (H1), and if the difference is equal to or greater than a predetermined threshold, a “water level abnormality” alarm can be issued.
In general, when a drifting substance adheres to the flow rate sensor, the deposit becomes an obstacle and the drifting substance accumulates one after another. The flow of running water changes due to the accumulation of drifting material, causing an error in the measured flow velocity value, and an error in the flow rate calculated based on the flow velocity value.
Conventionally, there has been no choice but to visually inspect for the accumulation of dust drifting in sewage pipes. However, the measurement system according to the present invention can detect an abnormal water level fluctuation caused by the accumulation of dust, and can issue a “water level abnormality” alarm. In response to this warning, it becomes possible to remove accumulated dust, and a measurement system having a self-diagnosis function can be realized.

(Third embodiment)
The present invention can apply various types of flow velocity sensors such as an optical type, an electromagnetic type, and a rotary type.
In particular, by using a force sensor that measures the drag due to the velocity pressure of the flowing water, it is possible to realize a measurement system that is less susceptible to the contamination of the flowing water and drifting objects.
Hereinafter, embodiments of the present invention when a force sensor is employed as the flow velocity sensor will be described.
FIG. 3 is a side view of the force sensor 1 according to the third embodiment. A main force sensor is installed in running water such as a sewer pipe. The flowing water flows from the left to the right in the drawing. The first pressure receiving unit 2 receives the pressure P due to the velocity pressure of the flowing water. That is, the force sensor is a sensor that measures the drag indicated by the arrow F.
The force sensor is provided with a second pressure receiving portion 3 opposite to the first pressure receiving portion 2. As shown in FIG. 3, the first pressure receiving portion and the second pressure receiving portion are provided with the same area and the same inclination angle.

The force sensor 1 is provided with an FBG (fiber Bragg grating) 7 that detects stress and load mechanisms 6-1 and 6-2 that transmit stress to the FBG in the hermetic chamber 4.
Here, FBG (Fiber Bragg Grating) refers to an optical fiber having a diffraction grating structure (FBG) in which the refractive index of the core portion of the optical fiber is periodically changed. When the incident light of the optical fiber is transmitted through the FBG portion, a wavelength component called a Bragg wavelength is reflected by the FBG, and the remaining portion is transmitted. It is known that the amount of shift of the Bragg wavelength changes depending on strain and temperature, and the stress transmitted to the optical fiber is detected using the property.

On the other hand, the second pressure receiving portion 3 provided outside the hermetic chamber 4 receives a force (not shown) from right to left in FIG. The first pressure receiving unit 2 receives the same water pressure, but the force received by the first pressure receiving unit is a force obtained by adding water pressure and drag due to running water, and the force accompanying the water pressure is the force from the left to the right in FIG. Become.
Since the first pressure receiving portion 2 and the second pressure receiving portion 3 are provided with the same area and the same inclination angle, the horizontal force due to the water pressure is the same and opposite to each other.

Next, the load mechanism 6 that transmits stress to the FBG will be described.
On both sides of the hermetic chamber 4, for example, metal diaphragms 5 and 5 ′ are provided. The pressure received by the pressure receiving portions 2 and 3 is transmitted to the respective transmission shafts 6-1 and 6-2 through the diaphragms 5 and 5 ′. In FIG. 3, force is applied to the transmission shaft 6-1 from left to right, and force is applied to the transmission shaft 6-2 from right to left. As described above, the drag force of the flowing water + water pressure is applied to the transmission shaft 6-1 and the water pressure is applied to the transmission shaft 6-2. In addition, since the direction in which the force is applied is opposite, the force corresponding to the water pressure is offset.

  Therefore, only the force corresponding to the drag force of the flowing water is transmitted to the FBG mounting portion 9. As can be seen from FIG. 3, one end (left side) of the optical fiber is fixed, and the other end is fixed to the FBG attachment 9. Therefore, when the force indicated by the arrow B is applied to the FBG mounting portion 9, a Bragg wavelength shift corresponding to the drag force occurs in the optical signal in the optical fiber due to the effect of the FBG (fiber Bragg grating) described above. This wavelength shift is extremely small. For example, the wavelength shift generated by water pressure (4500 Pa) corresponding to a water level of 45 cm is 1 nm (nanometer).

A balance weight 11 is attached to a part of each of the transmission shafts 6-1 and 6-2.
The balance weight 11 is rotatably mounted around the fixed shaft 14. The balance weight 11 always has a downward force due to gravity. When the amount of running water increases and the drag F increases, the transmission shaft 6-1 moves to the right in FIG. Thereafter, the drag F decreases as the amount of running water decreases. Due to the gravity of the balance weight 11, a force for moving the transmission shaft 6-1 to the left side is generated. That is, the balance weight 11 has a transmission shaft return function.

On the other hand, the FBG has a temperature characteristic in which the amount of shift of the Bragg wavelength changes depending on the temperature. In order to measure accurate drag, it is necessary to correct by temperature.
Therefore, another FBG (fiber Bragg grating) 8 for detecting temperature is further provided in the hermetic chamber 4. The FBG 8 is not linked to the transmission shaft 6-1, and is attached to the FBG attachment portion 10 that is installed independently. Therefore, the FBG 8 has an independent function of detecting the temperature in the hermetic chamber without being affected by the stress applied to the pressure receiving unit 2 and the pressure receiving unit 3 at all.

  By using different wavelengths, for example, 1540 nm and 1537 nm, between the FBG that detects the applied stress and another FBG that detects the temperature, the change in wavelength due to temperature can be specified, and the applied stress Thus, the temperature component can be removed and temperature correction can be performed.

In the present embodiment, the force sensor and the calculation unit are connected by an optical cable, and therefore have the following features compared to a measurement system using a general current meter that is electrically connected.
(1) Supply of electric power to the flow velocity sensor is unnecessary.
(2) Since the connection is made with an optical fiber, it is not necessary to take measures against leakage in water.
(3) Fewer moving parts and a low failure rate.
(4) The distance limitation between the flow rate sensor and the flow rate system is less than that of electrical connection.
For example, according to this system, up to five force sensors can be installed within a line length of 15 km.

A hardware configuration example of the measurement system according to the present invention will be described with reference to FIG.
A CPU (arithmetic unit), a storage device, an input device, and an output device are connected to a bus for exchanging information. The storage device stores programs for realizing each means, opening shape / dimension data corresponding to each sensor installation position (that is, pipe dimensions), data of various correlation curves, and the like. A flow rate sensor, a water level gauge, and the like are connected to the input device. A flow indicator, an alarm device, etc. are connected to the output device.

  In addition, as shown in FIG. 5, the storage device stores, for example, a “flow velocity-water level correlation curve”, a “flow velocity-average flow velocity correlation curve”, and a “flow velocity-flow correlation curve” corresponding to a plurality of piping environments and sensor installation environments. You may let them. The fact that the water level is known means that if the pipe shape is known, the average flow velocity and flow rate can be calculated. However, if the correlation curve is stored in advance, the calculation can be omitted, so that quick calculation is possible. .

When a force sensor is applied as the flow rate sensor, it is preferable to store a “drag-water level correlation curve”, a “drag-average flow rate correlation curve”, a “drag-flow rate correlation curve”, and the like. By storing in advance the “drag-average flow rate correlation curve” that includes the correction value for conversion from drag to flow rate in the “flow velocity-water level correlation curve” described above, the calculation to convert from drag to flow rate can be omitted, resulting in quick calculation. This is because it becomes possible.
It is also possible to appropriately reflect corrections relating to conversion in the correlation curve in advance.

  As information of each correlation curve, for example, as shown in FIG. 6, equation n and parameter n are stored corresponding to the piping environment S1, the piping environment S2, and the piping environment S3, respectively. These pieces of information are mathematical formulas obtained in advance by simulation calculation using another computer as described above. In this example, the correlation curve is represented by mathematical formulas and parameters, but the correlation curve may be represented by tabular data composed of numerical values corresponding to each data.

FIG. 7 is a block diagram of a flow rate measurement function constituting a part of the measurement system according to the present invention. A portion surrounded by a one-dot chain line is a flow rate measuring function. A sensor number and a flow velocity value specifying the sensor sent from the flow velocity sensor are input via the input device in the hardware configuration diagram described above.
In this measurement system, the measured flow velocity value sent from the anemometer is captured by the flow velocity value capturing means, and stored in a predetermined location of the storage device. Also, from the input sensor number, the pipe shape / dimension data, that is, the pipe dimension is taken out from the storage device, and the corresponding sensor installation environment such as E2, the flow velocity-water level correlation curve in the piping environment S2, Equation 2, Select.
The calculated water level can be obtained by substituting the flow velocity value into Equation 2 and Parameter 2 above. Similarly, the average flow velocity can be obtained by substituting the flow velocity value into the formula and parameters of the flow velocity-average flow velocity correlation curve.
The cross-sectional area of the running water is obtained from the piping dimensions taken out from the storage device and the calculated water level obtained from the above. By multiplying the cross-sectional area by the average flow velocity, the flow rate is calculated, and this flow rate value is sent to the flow rate indicator via the output device.

FIG. 8 is a block diagram of the water level alarm function of the measurement system according to the present invention. A portion surrounded by a one-dot chain line is a water level alarm function of a part of the measurement system.
The measured flow velocity and the measured water level are input to the present system via the input device from the flow rate sensor and a water level meter installed in the vicinity of the flow rate sensor. A flow velocity-water level correlation curve is selected based on the sensor number sent from the flow velocity sensor. The calculated water level can be obtained by substituting the actually measured flow velocity value into the mathematical formula and parameters relating to the flow velocity-water level correlation curve.
The difference between the calculated water level and the actually measured water level is calculated, and the absolute value of this value is compared with the threshold value stored in advance in the storage device. As a result, when the difference between the calculated water level and the actually measured water level is larger than a predetermined threshold, it is determined that the water level is abnormal, and an alarm display signal is sent to the alarm device via the output device. A normal display signal may be sent when it is within the threshold value.

FIG. 9 is a block diagram of a flow rate measurement function when a force sensor is employed as the flow rate sensor. A portion surrounded by a one-dot chain line is a part of the flow rate measurement function of the measurement system.
A sensor number and a drag value specifying the sensor sent from the force sensor are input via the input device described above. A conversion device that converts an optical signal sent from the force sensor into a drag value may be provided outside the system.
Means for converting the optical signal into a drag value based on the velocity pressure of running water may be provided in the measurement system. In this case, it is necessary to convert the wavelength shift into a drag value in consideration of the temperature characteristic of the Bragg wavelength. Since the conversion method from the Bragg wavelength to the drag is known, the description is omitted here.

Take the piping dimensions from the entered sensor number and select the formula and parameters for the corresponding drag-water level correlation curve.
The calculated water level can be obtained by substituting the drag value into the above formula and parameters, as in the case of calculating based on the flow velocity value. Similarly, the average flow velocity can be obtained by substituting the drag value into the formula and parameters of the drag-average flow velocity correlation curve.

  From the pipe dimensions of the pipe and the calculated water level obtained from the above, the cross-sectional area of the running water is obtained. By multiplying the cross-sectional area by the average flow velocity, the flow rate is calculated, and this flow rate value is sent to the flow rate indicator via the output device.

FIG. 1 is a diagram for explaining an installation mode of a flow rate sensor and the like in the measurement system of the present invention. FIG. 2 is a schematic diagram showing a correlation curve between the flow velocity and the water level according to the present invention. FIG. 3 is a side view of a force sensor according to an embodiment of the present invention. FIG. 4 is a diagram showing a hardware configuration example of the present invention. FIG. 5 is a data configuration example of various correlation curves in the storage device. FIG. 6 is a configuration example of correlation curve data. FIG. 7 is a block diagram of the flow measurement function of the present invention. FIG. 8 is a block diagram of the abnormal water level detection and alarm function of the present invention. FIG. 9 is a block diagram of the flow rate measuring function by the force sensor of the present invention. FIG. 10 is an external view of the anemometer installed in the sewer. FIG. 11 is a schematic diagram of a flow velocity / water level meter according to the prior art. 12 (a) and 12 (b) are diagrams showing the flow velocity distribution of running water at each water level of the sewer pipe. FIG. 13 is a diagram showing the relationship between the flow rate and the water level in a low gradient and high roughness pipe. FIG. 14 is a diagram showing the relationship between the flow rate and the water level in a high gradient, low roughness pipe.

Explanation of symbols

1 Flow velocity sensor (force sensor)
2 1st pressure receiving part 3 2nd pressure receiving part 4 Airtight chamber 5 Diaphragm 5 'Diaphragm 6 Load mechanism 6-1 Transmission shaft 6-2 Transmission shaft 7 FBG
8 Another FBG
9 FBG mounting portion 10 Another FBG mounting portion 11 Balance weight 12 Rubber cover 13 Linear bush with shaft rotation prevention function 14 Fixed shaft 15 Length adjuster 17 Current plate 18 Fiber storage case 19 Balance weight fixing member 20 External cover 21 Transmission rod 22 Contact plate 30 Water level gauge 31 Cable 41 Sewer pipe 42 Water surface

101 Flow velocity sensor 102 Flow velocity meter 103 Water level meter 103a Diaphragm 103b Strain gauge 104 Preamplifier 111 Sewage pipe 112 Water surface 113 Flow velocity distribution 114 Turnbuckle 115 Sensor holder

Claims (6)

A measurement system that measures the flow velocity, water level, and flow rate of a fluid flowing through an open channel without blocking the fluid flow,
A flow rate sensor installed in the open channel ;
Means for storing a plurality of flow velocity-water level correlation curves according to the piping environment and the installation environment of the flow velocity sensor;
Means for recognizing one flow velocity-water level correlation curve selected according to the piping environment and the installation environment of the flow velocity sensor;
Means for obtaining a calculated water level from a flow velocity measurement from the flow velocity sensor and the selected flow velocity-water level correlation curve ;
The measurement characterized in that the flow velocity-water level correlation curve is a flow velocity-water level correlation curve obtained in advance by simulation calculation from the shape, size, gradient, pipe roughness of the open channel, and the installation position of the flow velocity sensor. system. A water level sensor,
Means for calculating a difference between the actual water level measured by the water level sensor and the calculated water level;
Means for comparing the absolute value of the difference with a preset threshold;
The measurement system according to claim 1, further comprising means for transmitting an alarm signal when the absolute value of the difference is larger than the threshold value. Means for storing piping dimensions;
Measurement system according to claim 1 or 2, characterized in that it comprises, means for calculating the flow rate from the calculated level with the pipe dimensions. The measurement system according to any one of claims 1 to 3 , wherein the flow rate sensor is a force sensor that measures a drag due to a velocity pressure of flowing water. The force sensor, first and second pressure receiving portions facing each other in the flow direction of flowing water in the open channel ;
A load mechanism for transmitting a difference in stress between the first pressure receiving portion and the second pressure receiving portion to an FBG (fiber Bragg grating);
The FBG for detecting a difference in the stress transmitted from the load mechanism;
A device for measuring the drag force of flowing water comprising an airtight chamber containing the load mechanism and the FBG ,
The measurement system according to claim 4 , wherein the measurement system is a sensor that transmits the difference (a drag value due to a velocity pressure of flowing water) as an optical signal. The measurement system according to claim 4 or 5 , wherein the flow velocity-water level correlation curve includes a conversion correction value from a measured drag measured by the force sensor.

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