JPS63234112A - Flow rate measuring method for drainage channel - Google Patents

Abstract

PURPOSE:To collect necessary data when they are necessary by making a display normally at 2nd long time intervals although a flow rate is measure at 1st short time intervals. CONSTITUTION:The output of an analog board 5 is digitized by an A/D converter 10-1 and inputted to a CPU 10-4, which calculates flow rate at respective points of time from respective data on the flow velocity and the depth of water and specified channel data by using the output of a setting circuit 10-2 and records them in a memory circuit 15. Consequently, the flow rate is measured at intervals of, for example, one second and this value is regarded as 1st data. The 1st data measured at the current point is compared with the last 1st data and recorded and displayed unless the value increases by more than a constant value. If this value increases, only the 1st data at the point is employed at intervals of, for example, one hour and recorded and displayed as 2nd data, and when an abnormal increase in the 1st data continues, the 1st data are all recorded and displayed. Therefore, when water increases abruptly, switching to real-time recording is performed nearly automatically.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a flow rate measurement method when there is a sudden increase in water level when measuring the flow rate in an open channel or culvert where a weir or flume cannot be installed.

(Conventional technology and its problems) In measuring the flow rate in sewers, the water depth is measured over time, the cross-sectional area of the flowing water is determined geometrically from the water depth, and the flow velocity is determined using, for example, Manning's average flow velocity formula 7 % (1): : The following calculation formula was used.

Therefore, the flow rate is obtained as the product of the above-mentioned flowing water cross-sectional area and the average flow velocity, but when using the average flow velocity formula, the roughness coefficient n1 of the pipe bottom slope I is a uniform value in an actual pipe. However, the roughness coefficient n changes depending on the contents flowing inside the pipe or the degree of deterioration, and the pipe bottom slope I also generally differs from the designed slope due to poor construction or local subsidence.

However, it is impossible to set these appropriate values by on-site measurements, and the average flow velocity determined will have a large error. In fact, it has long been a problem that there is a large gap between the actual flow rate and the measured flow rate.

Furthermore, other methods, such as measuring water depth and current velocity separately,
Methods of determining the flow rate as the product of these values, such as using a flow rate needle such as an ultrasonic flow rate needle, require time and effort to install the sensor, the installation location is limited, and errors may occur in the flow rate depending on atmospheric conditions. There was a problem.

Furthermore, the conventional sampling method for measuring flow rate was to perform sampling at fixed time intervals and record the entire flow rate.

Therefore, since the above-mentioned fixed time interval has a limit on the data recording ability, carrying out the recording at short time intervals will result in an excessive amount of data, making data processing difficult.

However, in order to analyze runoff and determine the flow capacity of pipeline networks during floods, it is necessary to record detailed data on flow rate fluctuations.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a flow rate measurement method that can record necessary data when necessary.

(Means for solving the problem) In order to achieve the above-mentioned purpose, the detector 1 detects data on flow velocity and water depth, calculates the flow rate at a first time interval, and uses this flow rate data as the immediately preceding flow rate data. If the comparison value increases, remains unchanged, or decreases by less than a certain value, record only the flow rate data at the time when the two liquids were poured in a second time interval that is larger than the first time interval, and record the other flow rate data. The flow rate data is skipped, and if the comparison value is larger than the immediately preceding flow rate data by a certain value or more, all subsequent flow rate data are continuously recorded, and the flow rate data during this continuous recording is the same as the immediately preceding flow rate data. Continuous recording is continued until the comparison value becomes less than the comparison value before the start of continuous recording, and after the comparison value during continuous recording decreases and the continuous recording is ended, the recording time interval is changed to the second one again. The time interval shall be .

(Function) As mentioned above, the flow rate is measured at the short first time interval, but during normal times it is displayed at the long second time interval, and when the water is abnormally high, it is displayed at the first time interval. Displays detailed flow rate changes only as long as necessary.

(Example) First, a measuring device used in the flow rate measuring method of the present invention will be described. Figure 1 is a block diagram of the entire device, including a detector 1 that is immersed in water, a measuring device main body 4, and a display device 1.
It consists of 7. As shown in the second diagram, the circuit configuration of the detector 1 uses an electromagnetic current meter as the flow velocity sensor 2, so there are measurement electrodes 2-1.2 on both sides of the detector 1.
-2 is provided, and the detected voltage is amplified by a preamplifier 2-3 and outputted as flow velocity analog data from an output terminal 2-4.

In addition, an electromagnet 2- for generating a magnetic field as an electromagnetic flow needle
5 is provided, and is excited from the measuring device main body 4 through the input terminals 2-6. As the water pressure sensor 3, a pressure/voltage conversion element such as a semiconductor strain gauge is used as the water pressure detection section 3-1, and this voltage output is amplified by a preamplifier 3-2 and output as water depth analog data to the terminal 3. -Output from 3.

The measuring device main body 4 is provided with an analog board 5, a memory circuit 15, and a CPU board 10. The analog board 5 inputs the flow velocity data from the detector 1 to the sample and hold circuit 6 as shown in the circuit block diagram shown in FIG.

Separately, the output from the timing circuit is also input, and the continuously input flow velocity data is divided into fixed time intervals and input into the time constant circuit 8.

The time constant circuit 8 provides a constant time constant and outputs it to the CPU board 10 as a flow velocity signal via the amplifier 9.

The water depth data is transmitted to the CP as a water depth signal via the amplifier 11.
input to the u-board 10.

Note that the output of the timing circuit 7 is sent to the drive circuit 12.
is also input, and the electromagnet 2-5 of the flow velocity sensor 2 is excited in synchronization with the division of the flow velocity data at fixed time intervals.

On the other hand, the CPU board 10 has an A/D converter 10-1.
It consists of a setting circuit 1O-2, a clock 1O-3, and a CPU 10-4, and from the setting circuit 10-2, data such as specified waterway shape data, waterway size, etc. are sent from among the already registered data. is input. Incidentally, if an intermediate value of the above numerical values is required, it is also possible to input the numerical value from the setting input terminal instead of the output of the setting circuit 10-2.

The CPU 10-4 inputs the output of the analog board 5 after being digitized by the A/D converter 10-1, and the output of the setting circuit 10-2 inputs the measured flow velocity and water depth data and the data of the specified waterway. Based on the data, the flow rate at each time point is calculated using equation (1) and recorded in the memory circuit 15.

In the above recording, not all data is recorded, but selective recording is performed using a certain method. This recording method will be explained.

FIG. 5 is a flow chart of the operation of the CPU board 10 to perform the above display. First, the operation is started, and the first step is to measure the flow rate at first time intervals, for example, at intervals of one second (hereinafter, this data will be referred to as first data).

Second step: Compare the first data measured at the current moment with the first data immediately before this first data.

Third step: Determine whether the comparison value in the second step has increased beyond a certain value. If the determination result is NO, the process moves to the fourth step, and if the result is YES, the process moves to the seventh step.

Fourth step: At a second time interval, for example, one hour interval, only the first data at that time is adopted (hereinafter, this data will be referred to as second data).

Fifth step: Record the second data.

Sixth step: Display the second data recorded in the fifth step.

Seventh step: If the zero determination result of determining whether or not the abnormal increase in the first data continues is NO, the process moves to the fourth step and the subsequent operation is returned to normal operation.

If the determination result is YES, the process moves to the eighth step.

Eighth step: Record all the first data.

Ninth step: Display the first data recorded in the eighth step.

(Effects of the invention) As mentioned above, in normal times, it is sufficient to record a large amount of data at long time intervals, but in the event of a sudden increase in water, etc., the system automatically switches to almost real-time recording. Therefore, it is possible to investigate the suitability of the allowable capacity of the drainage channel without providing a particularly large memory circuit. Furthermore, it is possible to take appropriate measures in case of emergency.

[Brief explanation of the drawing]

Fig. 1 is an overall block diagram of the flow rate measuring device, Fig. 2 is a circuit block diagram of the detector, Fig. 3 is a circuit block diagram of the analog board, Fig. 4 is a circuit block diagram of the CPU board,
FIG. 5 is a flowchart of the operation of the CPU board. l: Detector, 4: Measuring device main body, 15: Memory circuit, 10: CPU board, 17: Display device. 2nd note

Claims (1)

[Claims] When continuously measuring the flow rate using a flow rate measuring device equipped with a detector that is immersed in the flowing water of a drainage canal, the detector detects data on the flow velocity and water depth and calculates the flow rate at a first time interval. , this flow rate data is compared with the immediately preceding flow rate data, and if the comparison value increases, remains unchanged, or decreases by less than a certain value, the flow rate data at the time when the comparison value coincides with a second time interval that is larger than the first time interval. If the comparison value is greater than the previous flow rate data by more than a certain value, all subsequent flow rate data are recorded continuously, and the flow rate data during this continuous recording is recorded. The flow rate data is compared with the immediately preceding flow rate data, and continuous recording is continued until the comparison value becomes less than the comparison value before the start of the continuous recording, and after the comparison value during continuous recording decreases and the continuous recording is ended. The method for measuring the flow rate of a drainage canal is characterized in that the recording time interval is again a second time interval.