JP3425667B2 - Flow velocity measuring device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow velocity measuring device for measuring the flow velocity of rivers, waterways, water pipes and the like.

[0002]

2. Description of the Related Art Conventionally, to measure the flow velocity of a river, it has been general to use a water turbine type velocity meter. The method of measuring the flow velocity of a river with the water turbine type current meter is that when it becomes necessary to measure the flow velocity, a person holds the velocity meter by hand into the river and inserts it into the water flow. It was to measure.

There is also an ultrasonic type flow velocity measuring device which measures the flow velocity in a pipeline by utilizing ultrasonic waves. Figure 8
It is a figure which shows the conventional ultrasonic type flow velocity measuring device. In FIG. 8, 30 is an ultrasonic flow velocity measuring device, 31 is a pipe line, 32
Is a liquid flowing in the conduit 31.

An ultrasonic flow velocity measuring device 3 is provided on the outer wall of the pipe 31.
1 is closely attached and fixed, and ultrasonic waves are irradiated toward the inside of the conduit 31. The applied ultrasonic waves are reflected by the bubbles in the liquid flowing in the pipe 31, floating matters, and the disturbance of the liquid density caused by the liquid flow, and then return to the ultrasonic flow velocity measuring device 31. At that time, due to the Doppler effect based on the flow of the liquid 32, the frequency of the reflected wave is increased or decreased from the irradiated frequency in proportion to the flow velocity of the liquid 32. By the way,
When the liquid 32 flows in the direction of the arrow, the frequency of the reflected wave increases in proportion to the flow velocity. Then, the amount of change in the reception frequency from the irradiation frequency is obtained by the measuring circuit, and the flow velocity of the liquid 32 is obtained from the amount of change.

Further, as disclosed in Japanese Patent Laid-Open No. 6-294670, a beat of a difference frequency is generated by mixing an emitted ultrasonic wave and a received reflected wave using an electric circuit, and the beat frequency is changed. A technique for measuring the flow velocity by measuring has also been developed. By doing so, even a slight frequency difference can be accurately detected, and the flow velocity can be accurately measured.

[0006]

However, in the above-mentioned conventional water turbine type velocity meter, when performing continuous measurement for a long period of time, it is necessary to fix the velocity meter to a river and install it for a long period of time. There was a problem that dust and the like flowing through the river adhered during the operation, and the rotation of the water turbine slowed down or stopped, making accurate measurement impossible.

Further, in the conventional ultrasonic type flow velocity measuring device for measuring the flow velocity based on the change amount of the reception frequency, the change amount of the frequency of the reflected wave with respect to the change of the flow velocity is extremely small. There is a problem that it is very difficult to obtain

Further, in the above-mentioned ultrasonic type flow velocity measuring apparatus utilizing the beat, since the emitted ultrasonic wave and the received reflected wave are mixed, a complicated electric circuit is required and the cost becomes high. There was a problem.

The present invention solves such a problem, that is, even if the anemometer is fixedly installed in the river and continuous measurement is performed for a long period of time, the influence of dust or the like flowing in the river. It is an object of the present invention to enable accurate measurement of a flow velocity with a simple and cost-saving configuration while using an ultrasonic type flow velocity measuring device capable of performing accurate measurement without being affected.

[0010]

In order to solve the above-mentioned problems, a flow velocity measuring apparatus according to claim 1 is provided with a rigid block and an outer surface of the rigid block, and a constant frequency toward a flowing liquid. And an ultrasonic transducer that is attached to the outer surface of the rigid block and is irradiated from the irradiation transducer into the liquid through the rigid block and reflected from the liquid and the rigidity. A velocity sensor having a receiving transducer that receives both of the ultrasonic waves reflected in the block and converts them into an electric signal, and a low frequency component of the output of the receiving transducer is detected, and the frequency is converted into a velocity. And a flow velocity measuring circuit for controlling the flow rate. With this configuration, the flow rate can be accurately measured without being affected by dust flowing in the river even when installed in the river and continuously measuring for a long period of time with a simple and cost-effective configuration. .

The flow velocity measuring device according to claim 2 is
The rigid block is made of stainless steel. This makes it possible to efficiently reflect the ultrasonic waves in the rigid block and also to resist rust and damage.

Further, the flow velocity measuring device according to claim 3 is
It is characterized in that it is used to measure the speed of a ship by fixing it on the part of the ship that comes into contact with water. In this way, the speed of the ship can be easily measured.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is an explanatory view of the principle of the flow velocity measuring device of the present invention. In FIG. 1, 1 is a rigid block, 2 is an inclined surface, 3 is an irradiation transducer, 4
Is a receiving transducer and 5 is a water stream.

The rigid block 1 is made of a block of stainless steel, aluminum or the like and has a rectangular shape as shown in FIG.
An inclined surface 2 is provided with a predetermined angle in one of the corners, and an irradiation transducer 3 and a reception transducer 4 each made of a piezoelectric element are arranged in parallel on the outer surface thereof. The oscillation power supplied to the irradiation transducer 3 and the reception signal output from the reception transducer 4 to the flow velocity measuring circuit are sent via the cable 6. Although not shown, the rigid block 1 is provided outside the rigid block 1, the irradiation transducer 3, and the reception transducer 4.
In order to protect the housing, it is covered with a metal storage case made of nickel-plated steel plate or the like.

A part A _{1 of the} ultrasonic wave A emitted from the irradiating transducer 3 is transmitted through the rigid block 1 and radiated into the water stream 5, and water generated by bubbles, suspended matter and water stream in the water stream 5 is radiated. Reflected due to disturbance of density, etc., reflected wave a
_The light enters the receiving transducer 4 as ₁ . Also,
The remaining part A ₂ of the ultrasonic wave A is reflected by the bottom surface of the rigid block 1 and then repeatedly reflected in the rigid block 1 before entering the receiving transducer 4.

At this time, the frequency of the reflected wave a ₁ is slightly higher than the frequency of the ultrasonic wave A emitted from the irradiation transducer 3 due to the Doppler effect due to the flow velocity of the water flow 5. The rate of increase in the frequency is proportional to the flow velocity of the water flow 5.

As described above, the flow velocity of the water stream 5 can be measured by directly detecting the change in the frequency of the reflected wave reflected from the water, but the change in the frequency of the reflected wave with respect to the change in the flow velocity is extremely small. It is very difficult to accurately obtain the flow velocity from the amount of change in frequency.

Here, that point will be described. Flow velocity v
And the amount of change in frequency Δf are as shown in Equation 1.

[0019]

[Equation 1] Here, C is the speed of sound in water (1450 m / s), f _T is the irradiation frequency, and θ is the irradiation angle with respect to the flow direction.

Here, for example, the irradiation frequency f _T is 625
Assuming that the kHz and the irradiation angle θ are 60 °, the frequency change amount Δf is 1.72 kHz when the flow velocity v is 4 m, and 0.86 kHz when the flow velocity v is 2 m. That is, the reception frequency is 626.72 kHz when the flow velocity v is 4 m, and 625.86 kHz when the flow velocity v is 2 m, which is 0.28% with respect to the irradiation frequency f _T , respectively.
It will increase by 0.14%. It is not easy to detect such small fluctuations accurately.

Therefore, the radiated ultrasonic wave and the reflected ultrasonic wave are mixed to generate a beat, and the flow velocity is measured by measuring the frequency of the beat. Beat is a phenomenon in which when two sounds with slightly different frequencies coexist, the sound periodically becomes stronger or weaker due to sound wave interference.The beat frequency is the difference between the frequencies of the two sounds. Is equal to The same applies to ultrasonic waves.

If such a beat phenomenon is utilized, an output of a frequency equal to the difference between the applied ultrasonic wave and the reflected ultrasonic wave can be obtained, so that the change in the frequency of the reflected wave with respect to the change in the flow velocity is small. Also, the amount of change in frequency can be accurately detected, and as a result, the flow velocity can be accurately obtained. In utilizing the phenomenon of beat in detecting the amount of change in the frequency of the reflected wave, a complicated electric circuit is used in the present invention to mix the emitted ultrasonic wave and the reflected ultrasonic wave. Instead, the rigid block 1 has a special structure so that both waves are mixed in the rigid block 1.

That is, the rigid block 1 is made of stainless steel or aluminum which has excellent ultrasonic wave conduction characteristics and ultrasonic wave reflection characteristics inside the surface, and a part of the ultrasonic wave A emitted from the irradiation transducer 3 is formed. The position of the ceiling surface and the rear end surface of A2 is adjusted so that A2 is reflected on the bottom surface of the rigid block 1 and then repeatedly reflected in the rigid block 1 and then enters the receiving transducer 4. .

As the material of the rigid block 1, a metal other than stainless steel or aluminum, a plastic, or the like can be used as long as a good ultrasonic wave reflection characteristic can be obtained. However, it is most desirable to use stainless steel and aluminum, especially stainless steel, from the viewpoints of ultrasonic wave reflection characteristics and strength against rust and damage.

As a result, from the irradiation transducer 3
The ultrasonic wave A to be irradiated is part A ₁Is rigid block 1
The water in the water flow 5 is transmitted through the inside of the
Due to disturbance of water density caused by bubbles, suspended matter and water flow
Reflected and reflected wave a₁As the receiving transducer 4
Incident. Also, the remaining part A of the ultrasonic wave A₂Is a rigid block
Reflected on the bottom surface of the rack 1, and then reflected inside the rigid block 1.
After repeating the irradiation, it is incident on the receiving transducer 4.
It

At this time, the frequency of the reflected wave a ₁ becomes higher than the frequency of the ultrasonic wave A emitted from the irradiation transducer 3 due to the Doppler effect due to the flow velocity of the water flow 5.
The rate of increase in frequency is proportional to the flow velocity of the water flow 5. The receiving transducer 4 receives the reflected wave a ₁ and the ultrasonic wave A which is repeatedly reflected in the rigid block 1.
And a part A ₂ of the incident light is added.

In this way, the input from the receiving transducer 4 is a mixture of the reflected wave a ₁ reflected by the water stream 5 and a part A _{2 of the} ultrasonic wave A repeatedly reflected in the rigid block 1. Output is obtained. The output is sent to the flow velocity measuring circuit.

FIG. 3 is a block diagram of the flow velocity measuring circuit. The flow velocity sensor 13 corresponds to the one shown in FIGS. The reference frequency oscillation circuit 10 outputs a rectangular wave at a stable frequency by the crystal oscillator. Waveform shaping circuit 11
Shapes the output of the reference frequency oscillation circuit 10 and converts it into a sine wave having a constant frequency. After being amplified by the amplifier circuit 12, it is given to the irradiation transducer 3 of the flow velocity measuring device 13.

As a result, ultrasonic waves are emitted from the irradiation transducer 3, and the reception transducer 4 of the flow velocity measuring device 13 receives the reflected wave a ₁ reflected by the water flow 5 and the rigid block 1 as described above. A part A _{2 of the} ultrasonic wave A that has been repeatedly reflected is mixed and input, and a signal corresponding thereto is output from the receiving transducer 4.

The output waveform from the receiving transducer 4 is as shown in FIG. As shown in FIG. 4, in the waveform output from the receiving transducer 4, the high frequency amplitude oscillates in the cycle T. The output is amplified by the high frequency amplification circuit 14 and then detected by the amplitude detection circuit 15. as a result,
A signal having a frequency significantly lower than the ultrasonic waves emitted from the irradiation transducer 3 and a frequency proportional to the flow velocity of the water flow 5 can be obtained. It is input to the low frequency amplifier circuit 16. The low frequency amplifier circuit 16 has a built-in upper limiter circuit, and the low frequency amplifier circuit 16 outputs a signal whose amplitude falls within a predetermined range.

The output is input to the frequency-voltage conversion circuit 17, and a voltage proportional to the flow velocity of the water flow 5 is obtained. The flow velocity display 18 converts the voltage into a flow velocity and displays it. Further, the voltage comparison / selection circuit 19 compares with a reference value, and when the flow velocity is out of a predetermined range, an alarm signal is output to the automatic notification device via the buffer circuit 20.

An experiment was conducted using such an apparatus. In the experiment, the oscillation frequency of the reference frequency oscillation circuit 10 is 625 kHz.
As z, the irradiation transducer 3 is excited, and a rectangular hole having a width of 11 mm and a length of 51 mm is opened on the side surface of the pipe having an inner diameter of 16 mmφ, and the flow velocity measuring device having the structure shown in FIG. Then, water was sent by a pump through it to flow, and the relationship between the flow velocity and the output voltage was obtained. The measurement was performed by changing the rotational speed of the pump and dividing the flow rate per second at that time by the cross-sectional area of the pipe to calculate the flow velocity. Then, the output voltage of the frequency-voltage conversion circuit 17 was measured for each different flow rate. In addition, the conversion ratio of the frequency-voltage conversion circuit 17 is 2 V when the input is 2 kHz.
Was set so that the output of

FIG. 5 is experimental data showing the relationship between the flow velocity and the output voltage, and FIG. 6 is a graph showing the relationship. As is clear from FIG. 6, it has been confirmed that the flow velocity and the output voltage have a proportional relationship, and the flow velocity can be accurately measured based on the output voltage of the frequency-voltage conversion circuit 17.

This flow velocity measuring device can be installed in a river to continuously measure the flow velocity of the river. As described above, the voltage comparison / selection circuit 19 compares with the reference value, and when the flow velocity is out of the predetermined range, an alarm signal is output to the automatic notification device via the buffer circuit 20. The alarm signal is notified to the manager by the automatic notification device. The above reference values include a lower limit value, an upper limit value, and an abnormal upper limit value,
You can set multiple reference values.

FIG. 7 is a block diagram of the automatic notification device. The flow velocity signal receiving circuit 21 receives the alarm signal from the buffer circuit 20 and sends it to the microcomputer 22. The microcomputer 22 takes over the signal processing of the automatic notification device and executes it. In the setting circuit 23, a notification destination, a notification timing, etc. are set. In the message registration memory 24,
Message data corresponding to the type of alarm is stored. The telephone number memory 25 stores the telephone number of the report destination.

Therefore, when an alarm signal is sent to the flow velocity signal receiving circuit 21, the microcomputer 22 receives the alarm signal, and when the time set in the setting circuit 23 arrives, a telephone number is stored in the telephone number memory 25. The voice reproduction circuit 2 retrieves the corresponding message data from the message registration memory 24 while transmitting it to the dialer circuit 26.
Send to 7. As a result, the dialer circuit 26 outputs the tone signal or pulse signal of the received telephone number to call the administrator, and the voice reproduction circuit 27 converts the received message data into a voice signal and outputs it. The voice signal is sent to the telephone line via the amplifier circuit 28 and the electrical insulation circuit 29.

In the above embodiment, the case of measuring the flow velocity of a river has been described, but it can be used for measuring the flow velocity of other water channels, pipes and the like. It can also be used to measure the flow velocity of liquids other than water, as well as water flow. Further, it is possible to measure the speed of a ship or the like by fixing the flow velocity sensor to the ship's skid or the like.

[0038]

Since the present invention is constructed as described above, it has the following effects. That is, in the flow velocity measuring device according to claim 1, after being irradiated from the irradiation transducer, the receiving transducer simultaneously receives the ultrasonic wave reflected from the liquid and the ultrasonic wave reflected in the rigid block. Convert it to an electrical signal,
Since the low frequency component is detected and used for the flow velocity measurement, a complicated electric circuit for mixing the irradiated ultrasonic wave and the received reflected wave is not necessary, and the structure is simple and the cost can be suppressed. Even when installed in a river and continuously measuring for a long period of time, the flow velocity can be accurately measured without being affected by dust or the like flowing in the river.

The flow velocity measuring device according to claim 2 is
Since the rigid block is made of stainless steel, ultrasonic waves can be efficiently reflected in the rigid block, and the rigid block is resistant to rust and damage.

The flow velocity measuring device according to claim 3 is
Since it is used to measure the speed of the ship by fixing it to the part of the ship that comes into contact with water, the speed of the ship can be easily measured.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of a flow velocity measuring device of the present invention.

FIG. 2 is an external view of a flow velocity sensor used in the present invention.

FIG. 3 is a block diagram of a flow velocity measuring circuit.

FIG. 4 is a diagram showing an output waveform of a receiving transducer of a flow velocity sensor.

FIG. 5 is experimental data showing the relationship between flow velocity and output voltage.

FIG. 6 is a graph showing the relationship between flow velocity and output voltage.

FIG. 7 is a block diagram of an automatic notification device.

FIG. 8 is a diagram showing a conventional ultrasonic flow velocity measuring apparatus.

[Explanation of symbols]

1 ... Rigid block 2 ... Inclined surface 3 ... Transducer for irradiation 4 ... Transducer for reception 5 ... Water flow 6 ... Cable

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-58-178216 (JP, A) JP-A-8-327733 (JP, A) JP-A 63-133019 (JP, A) JP-A 53- 114472 (JP, A) Special Table 10-508111 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01F 1/66 G01F 1/66 103 G01P 5/00 G01P 5/00

Claims (3)

(57) [Claims] 1. A rigid block, an irradiation transducer mounted on the outer surface of the rigid block and irradiating ultrasonic waves of a constant frequency into a flowing liquid, and the irradiation block mounted on the outer surface of the rigid block. Receiving transducer for receiving both the ultrasonic waves reflected from the liquid and the ultrasonic waves reflected in the liquid from the liquid transducer through the rigid block into the liquid and converting them into electric signals. And a flow velocity measuring circuit for detecting a low frequency component of the output of the receiving transducer and converting the frequency into a flow velocity. 2. The flow velocity measuring device according to claim 1, wherein the rigid block is made of stainless steel. 3. The flow velocity measuring device according to claim 1, which is used for speed measurement of a ship by being fixed to a portion of the ship that comes into contact with water.