JP2001074526A - Flow measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dispense with installation of a weir and to prevent a foreign substance from accumulating by detecting water pressure at a high pressure side pressure receiving part provided facing to the upstream direction and a low pressure side pressure receiving part provided facing to the downstream direction, and obtaining a flow rate based on the differential pressure, and flow speed and water level computed from the static pressure at the same point. SOLUTION: A differential pressure detector 1 is constituted by arranging two water pressure detecting elements on the surface and back in parallel, one detecting element is faced to the upstream direction as a high pressure side pressure receiving part 2, the other is faced to the downstream direction as a low pressure side pressure receiving part 3, and the respective ones are vertically installed on the bottom of the water passage. Both pressure receiving parts 2, 3 detect water pressures, and the differential pressure signals is applied to a converter 5 through a cable 4. At this time the detector 1 detects static pressure of the provided position by a static pressure sensor 1a to send to the converter 5. The converter 5 computes flow speed and water level up to the water surface from the differential pressure signal and the static pressure signal, and further computes the flow based on the water level, the flow speed, and the breadth of a water passage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate measuring device suitable for measuring the flow rate of an open channel such as a water discharge channel.

[0002]

2. Description of the Related Art FIG. 10 shows a conventional flow measuring device of this type, for example. This is called a weir type flow meter, in which a weir 20 of a predetermined height is installed, a level meter 21 is immersed in the water on the upstream side, and the difference between the water surface obtained by the level meter 21 and the upper surface of the weir 20, that is, And the flow rate Q is calculated based on the water level h above the weir 20.

[0003]

The conventional flow rate measuring device shown in FIG. 10 has a problem that the weir 20 must be installed and the cost increases accordingly. In addition, there is a problem that foreign matter is deposited on the weir 20.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems.
It is an object of the present invention to provide a flow measuring device which can eliminate a weir and prevent the accumulation of foreign matter beforehand.

[0005]

The invention according to claim 1 is
In a flow rate measuring device that measures the flow rate of an open channel such as a water discharge channel, a high pressure side pressure receiving unit and a high pressure side pressure receiving unit are integrally mounted with two water pressure detection elements so as to respectively detect water pressure on a surface in a front side and a back side. A low pressure side pressure receiving part is formed, the high pressure side receiving part is installed in the water with the high pressure side receiving part facing the upstream of the flow of water, and the low pressure side pressure receiving part is installed in the water facing the downstream direction of the water flow. Differential pressure detector that detects the difference between the differential pressure and the water pressure detected by the low pressure side pressure receiving unit, a static pressure sensor that detects the static pressure at the position where the differential pressure detector is installed, and a differential pressure signal of the differential pressure detector And convert the static pressure signal of the static pressure sensor into a digital signal, calculate the flow velocity and water level based on the converted differential pressure signal and static pressure signal, and calculate the flow rate based on the calculated flow velocity and water level. And a container.

According to a second aspect of the present invention, in the flow rate measuring device according to the first aspect, the differential pressure detector, the static pressure sensor, and the converter are integrally sealed and immersed in water, and the ground is connected via a cable. It is characterized by being transmitted to a device.

According to a third aspect of the present invention, in the flow rate measuring device according to the first aspect, the differential pressure detector and the static pressure sensor are fixed near the bottom of the water channel.

According to a fourth aspect of the present invention, in the flow rate measuring device according to the first aspect, the distal end portion is submerged in water, the proximal end portion is projected from the water surface, and the proximal end portion is fixed to a ground fixing member. A fixed rod-shaped member is provided, and a differential pressure detector and a static pressure sensor are fixed to the tip of the rod-shaped member.

According to a fifth aspect of the present invention, in the flow rate measuring device according to any one of the first to fourth aspects, a hood is provided on each of the high pressure side pressure receiving portion and the low pressure side pressure receiving portion. It is.

According to a sixth aspect of the present invention, in the flow rate measuring device according to any one of the first to fifth aspects, when the flow rate obtained by the calculation is equal to or less than a predetermined threshold value, the detected value is invalidated. It is characterized by doing.

According to a seventh aspect of the present invention, there is provided the flow rate measuring apparatus according to any one of the first to sixth aspects, wherein a means for integrating and storing the flow rate obtained by the calculation at regular time intervals is provided. Display means for displaying the unit time flow rate and the stored integrated flow rate.

According to an eighth aspect of the present invention, in the flow rate measuring device according to the seventh aspect, when the flow rate obtained by the calculation becomes a negative value, a sign indicating that the flow has been reversed is displayed, The present invention is characterized in that the current unit time flow rate is subtracted from the previous integrated flow rate.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on preferred embodiments shown in the drawings. FIG. 1 is a schematic configuration diagram of a first embodiment of a flow measurement device according to the present invention.
In the figure, reference numeral 1 denotes a differential pressure detector, which has an envelope formed by making full use of welding or the like so that it can be installed in water.
Two water pressure detecting elements are integrally mounted therein. These water pressure detecting elements are arranged in parallel to the surfaces having a front side and a back side with respect to each other, and one of them forms the high pressure side pressure receiving portion 2 and the other forms the low pressure side pressure receiving portion 3.
Then, the high-pressure side pressure-receiving portion 2 is directed to the upstream direction of the water flow with its surface vertical, and the low-pressure side pressure-receiving portion 3 is directed to the downstream direction of the water flow with its surface vertical, to the bottom of the water channel. is set up. The differential pressure detector 1 detects a difference between the water pressure detected by the high pressure side pressure receiving unit 2 and the water pressure detected by the low pressure side pressure receiving unit 3, and outputs an analog signal corresponding to the differential pressure via a cable 4. The signal is applied to the converter 5. Further, the differential pressure detector 1 has a built-in static pressure sensor 1a for detecting a static pressure at a position where the differential pressure detector is installed.

The converter 5 is a microprocessor (MPU)
, And receives the supply of operating power from the power supply 6, converts each analog signal of the differential pressure detector 1 and the static pressure sensor 1a into a digital signal, and converts the converted hydraulic pressure difference signal and the static pressure signal. And the water level is calculated based on the calculated flow rate and water level, and the flow rate is calculated based on the calculated flow rate and water level.

The operation of the first embodiment configured as described above will be described below. The differential pressure detector 1 is a high pressure side pressure receiving section 2
And the surface of the low pressure side pressure receiving part 3 is set to be vertical. Therefore, if there is no flow in the channel,
High pressure side pressure receiving portion 2 and the water head pressure to the low pressure side pressure receiving portion 3 of the differential pressure detector 1, i.e., the static pressure P _L is the differential pressure acts equally is zero. If there is a flow, a pressure corresponding to the magnitude of the flow is applied to the high pressure side pressure receiving unit 2, that is, the dynamic pressure P _D
Acts, and the total pressure _PT applied to the high-pressure side pressure receiving section 2 is P _L +
The P _D. On the other hand, the low pressure side pressure receiving section 3 has a static pressure P _L
Only joins. Therefore, the differential pressure detector 1 applies a differential pressure signal corresponding to the dynamic pressure P _D to the converter 5. Further, the static pressure sensor 1 a detects the static pressure P _L and applies it to the converter 5.

The converter 5 converts the static pressure P _L applied from the static pressure P _L and the static pressure sensor 1a applied from the differential pressure detector 1 into digital values, subsequently, calculates the flow velocity v by the following formula .

(Equation 1) Here, g: gravity acceleration γ: specific gravity of water.

The converter 5 is a static pressure sensor 1 according to the following equation.
The water level h from a to the water surface is determined by the following equation.

H = P _L / γ (2) In this case, assuming that the width of the channel is B as shown in FIG. 2, the converter 5 calculates the flow rate Q by the following equation. Q = v · h · B (3)

The converter 5 equipped with a microprocessor performs the above calculation using a calculation formula set in advance in memory. In particular, the width B of the water channel can be changed at any time according to the application. The result of the calculation is converted into an analog signal and transmitted to a monitoring device or the like as a DC signal of 4 to 20 mA.

Thus, according to the first embodiment, when measuring the flow rate of an open channel such as a spillway, a flow rate measuring device which obviates the need for a weir and can prevent the accumulation of foreign matter beforehand is obtained. Can be

In the above embodiment, the flow rate signal is transmitted as an analog signal to a monitoring station or the like. However, it is of course possible to transmit the flow rate signal as a digital signal.

In the above embodiment, the static pressure sensor 1a
Is used, but a low-pressure receiving portion directed in the downstream direction of the flow can be used instead of the static pressure sensor.

FIG. 3 is a sectional view showing the configuration of a second embodiment of the flow measuring device according to the present invention. In the drawing, the same elements as those in FIG. I do. In the embodiment shown in FIG. 1, only the differential pressure detector 1 is submerged in water,
Although connected to the converter 5 on the ground by the cable 4 derived from the differential pressure detector 1, in the embodiment shown in FIG. 3, the differential pressure detector 1 and the converter 5 are integrated, and this integrated structure is used. The body is placed underwater and transmitted via a cable 4 to a housing 7 provided at a monitoring station on the ground, for example. In this case, a sensor unit 9 such as a gravity balance type, an electric resistance type, or a differential transformer mounted between the high pressure side pressure receiving unit 2 and the low pressure side pressure receiving unit 3 so as to respond to the pressure difference therebetween.
Is arranged. The sensor unit 9 and the converter 5
Are internally wired and the cable 4 led out of the converter 5
The housing for accommodating them is sealed with a confidential seal portion 7 such as packing or resin.

The characteristic of this flow rate measuring device is that the sensor section 9 and the converter 5 are maintained at substantially the same temperature, so that a temperature error can be suppressed low and a weak signal from each pressure sensor is transmitted. Since it is not necessary to route the wires, noise resistance performance can be improved.

FIG. 4 shows an example of installation of the flow rate measuring device having the structure shown in FIG. Here, it is fixed to the vicinity of the bottom of the water channel using the fixing fitting 10. As described above, this fixation causes the high pressure side pressure receiving portion 2 to be directed in the upstream direction of the water flow, and the low pressure side pressure receiving portion 3 to be directed in the downstream direction of the water flow. As a result, the standard of the water level h is determined, and stable measurement is always possible.

FIG. 5 is a schematic configuration diagram of a third embodiment of the flow measuring device according to the present invention. In this embodiment, the differential pressure detector 1 is attached to the tip of a rod-shaped member 11, and the differential pressure detector 1 is submerged by the rod-shaped member 11.
Is fixed to the ground using a clamp 12. By adopting such a fixing method, there is an advantage that installation and removal of the differential pressure detector 1 are facilitated, and maintenance is significantly facilitated.

FIG. 6 is a schematic configuration diagram of a fourth embodiment of the flow measuring device according to the present invention. In this embodiment, a tubular high pressure side hood 13 is provided on the high pressure side pressure receiving surface of the differential pressure detector 1, and a tubular low pressure side hood 14 is provided on the low pressure side pressure receiving surface. With such a configuration, the pressure due to the flow impinging on the pressure receiving surface is made uniform, and measurement can be performed without being affected by eddies or the like generated near the differential pressure detector 1.

FIG. 7 is a graph showing the relationship between the dynamic pressure P _D and the speed v, and the following relationship is established between them.

(Equation 2)

However, the relationship of the equation (4) holds relatively stable if the flow velocity v exceeds a predetermined value, but the signal of the velocity v tends to become unstable in a low speed region below that. For this reason, it is necessary to set the flow rate signal in the low flow rate range to zero below a certain value, or to perform processing for giving the following relationship.

(Equation 3)

Accordingly, by providing the converter 5 with a processing function for a low flow rate value, that is, a low cut processing function, the flow rate measurement accuracy can be improved.

FIGS. 8A and 8B are a block diagram and a side view, respectively, showing the configuration of a fifth embodiment of the flow measuring device according to the present invention. In this embodiment, the converter 5 has an LCD display 5.
5, the unit time flow rate and the integrated flow rate are selectively displayed on the LCD display 55 at any time by setting. In this case, the converter 5 includes an MPU 51, an AD converter 52, a memory 53, a DA converter 54, and an LCD display 55. Then, the AD converter 52 converts the analog differential pressure signal output from the differential pressure detector 1 into a digital signal and adds the digital signal to the MPU 51. The MPU 51 temporarily stores this signal in the memory 53, and subsequently, the above (1) to (5)
The unit time flow rate is obtained by executing the processing of the equation (3), and the value is stored in the memory 53. DA converter 54 is an MPU
The unit time flow rate is converted into an analog signal according to the instruction of 51 and output. Further, the MPU 51 integrates the unit time flow rate stored in the memory 53 at regular intervals to obtain a total flow rate up to the present, that is, an integrated flow rate. Here, according to the setting state of the external setting means (not shown), the MPU 51
Displays the unit time flow rate on the LCD display 55, displays the integrated flow rate, or displays both of them. This makes it possible to measure and monitor not only the unit time flow rate but also the integrated flow rate.

Each of the above embodiments is based on the premise that the direction of the flow of water is constant. However, there are waterways where the flow of water is reversed. In this case, the differential pressure detector 1 outputs a negative differential pressure signal, and the correct integrated flow rate can be obtained by subtracting the unit time flow rate accordingly. FIG. 9 is a functional block diagram showing the configuration of a sixth embodiment of the flow measuring device according to the present invention having these functions in a flowchart. Hereinafter, the operation of the converter 5 will be described with reference to FIG.

First, at step 101, it is determined whether the differential pressure signal is positive or negative. If positive, the flow rate calculation is executed at step 102, and the flow rate signal is transmitted at step 103. Then, the unit time flow rate is stored in the memory 5 in step 104.
3 and the integrated flow rate is obtained. And step 1
At 05, the unit time flow rate and the integrated flow rate are displayed on the LCD 55.
To be displayed.

Next, when it is determined in step 101 that the differential pressure signal is negative, the absolute value is obtained in step 106, and then the flow rate calculation is executed in step 107, and in step 108 Transmit the flow signal. And
The actual flow rate is obtained by subtracting the unit time flow rate from the integrated flow rate stored in the memory 53 in step 109, and the unit time flow rate and the flow rate in step 110 together with the sign that the direction of the water flow has been reversed. The actual flow rate is displayed on the LCD display 55.

Thus, according to the sixth embodiment, it is possible to calculate and display the unit time flow rate, the integrated flow rate, and the actual flow rate of a water channel in which water may flow backward.

[0036]

As is apparent from the above description, according to the present invention, when measuring the flow rate of an open channel such as a water channel, a weir is not required, and the accumulation of foreign matter can be prevented beforehand. A flow measurement device can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a first embodiment of a flow measurement device according to the present invention.

FIG. 2 is a sectional view of a water channel to which the first embodiment shown in FIG. 1 is applied;

FIG. 3 is a sectional view showing a configuration of a second embodiment of the flow measuring device according to the present invention.

FIG. 4 is an installation example of a flow measuring device having the configuration shown in FIG.

FIG. 5 is a schematic configuration diagram of a third embodiment of the flow measurement device according to the present invention.

FIG. 6 is a schematic configuration diagram of a fourth embodiment of the flow measurement device according to the present invention.

FIG. 7 is a diagram showing the relationship between the dynamic pressure and speed of flowing water for explaining the operation of each of the above embodiments.

FIG. 8 is a block diagram and a side view showing a configuration of a fifth embodiment of a flow measurement device according to the present invention.

FIG. 9 is a functional block diagram showing a configuration of a sixth embodiment of the flow measuring device according to the present invention in a flowchart.

FIG. 10 is a schematic configuration diagram of a conventional flow measurement device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Differential pressure detector 1a Static pressure sensor 2 High pressure side pressure receiving part 3 Low voltage side pressure receiving part 4 Cable 5 Transducer 6 Power supply 7 Housing 8 Security seal part 9 Sensor part 10 Fixture 11 Bar-shaped member 12 Clamp 13 High pressure side hood 14 Low pressure side Hood 51 MPU 55 LCD display

Claims (8)

[Claims] 1. A flow rate measuring device for measuring a flow rate of an open channel such as a water discharge channel, wherein two water pressure detecting elements are integrally mounted so as to detect a water pressure on a surface having a relationship between a front side and a back side. Forming a high pressure side pressure receiving part and a low pressure side pressure receiving part, the high pressure side receiving part is oriented in the upstream direction of the flow of water, and the low pressure side pressure receiving part is installed in the water in a downstream direction of the water flow, A differential pressure detector for detecting a difference between a hydraulic pressure detected by a side pressure receiving portion and a hydraulic pressure detected by the low pressure side pressure receiving portion; and a static pressure sensor for detecting a static pressure at a position where the differential pressure detector is installed. Convert the differential pressure signal of the differential pressure detector and the static pressure signal of the static pressure sensor into digital signals, calculate the flow velocity and water level based on the converted differential pressure signal and static pressure signal, and calculate A converter that calculates the flow rate based on the flow velocity and water level A flow measuring device, comprising: 2. The method according to claim 1, wherein the differential pressure detector, the static pressure sensor and the converter are integrally sealed and immersed in water, and a flow signal is transmitted to a device on the ground via a cable. The flow measurement device as described. 3. The flow measuring device according to claim 1, wherein the differential pressure detector and the static pressure sensor are fixed near the bottom of the water channel. 4. A rod-shaped member having a distal end portion submerged in water, a proximal end portion protruding from the water surface, and having the proximal end portion fixed to a fixed member on the ground. The flow rate measuring device according to claim 1, wherein the differential pressure detector and the static pressure sensor are fixed. 5. The flow measuring device according to claim 1, wherein a hood is provided on each of the high pressure side pressure receiving portion and the low pressure side pressure receiving portion. 6. The flow rate measuring apparatus according to claim 1, wherein the detected value is invalidated when the flow rate obtained by the calculation is equal to or less than a predetermined threshold value. 7. A system comprising: means for accumulating and storing a flow rate obtained by calculation at regular intervals; and display means for displaying a unit time flow rate of the calculated flow rate and a stored integrated flow rate. The flow measurement device according to claim 1. 8. When the flow rate obtained by the calculation becomes a negative value, a sign indicating that the flow has been reversed is displayed, and the current unit time flow rate is subtracted from the previous integrated flow rate. The flow rate measuring device according to claim 7.