JPH0590328U - Flow rate measuring device - Google Patents

Abstract

(57) [Summary] [Purpose] To facilitate construction and maintenance, and to obtain accurate measurement values without being affected by water turbidity. [Structure] A transmitter 2 for emitting ultrasonic waves obliquely to a water surface S from above an open water channel 1 having a constant water channel width B.
And a receiver that receives the reflected wave from the water surface S are arranged in a substantially symmetrical positional relationship with respect to the vertical axis X on the water surface S, and the flow velocity obtained by using the Doppler effect between the emitted wave and the reflected wave. V
Then, the flow rate Q is calculated from the water level H by the water level gauge 5 and the water channel width B.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a flow rate measuring device used for measuring a flow rate in an open channel having a constant channel width.

[0002]

[Prior Art]

 Conventionally, a device that uses radio waves is known as a device that measures the flow rate of an open water channel by a non-contact method, but in this case, the range is restricted with regard to the allocation of the frequency of the used radio wave and the radio field intensity. However, it is difficult to handle such as having to set within the regulation range.

Therefore, generally, as shown in FIG. 4, the water level H is measured by a water level gauge 42 attached to an open water channel 41 having a constant water channel width B, and an ultrasonic wave attached to the side surface of the open water channel 41 is measured. Ultrasonic waves are transmitted and received by the flow velocity meters 43A and 43B to measure the flow velocity V, and the above-mentioned water channel width B, water level H and flow velocity V are applied to the flow rate calculation formula, Q = B · H · V, and the open channel 41 is opened. Flow rate measuring devices configured to calculate the flow rate Q are often used.

[0004]

[Problems to be solved by the device]

 Since the above-mentioned conventional flow rate measuring device is equipped with an ultrasonic velocity meter and the like in water, it takes a lot of time and labor for construction and maintenance work. In addition, since the measurement is performed in water, it is easily affected by the turbidity of water, which causes a measurement error.

The present invention has been made in order to solve the above problems, and provides a highly reliable flow rate measuring device which can simplify the construction and maintenance and has less influence of turbidity. The purpose is to

[0006]

Means for Solving the Problems In order to achieve the above object, a flow rate measuring device according to the present invention comprises a transmitter for emitting ultrasonic waves obliquely to the water surface above an open channel having a constant channel width. , The receiver that receives the reflected wave from the water surface is placed in a substantially symmetrical positional relationship with respect to the vertical axis on the water surface, and the frequency difference between the emitted wave of the ultrasonic wave and the reflected wave, the wavelength of the emitted wave, and the The flow rate is calculated from the flow velocity obtained from the incident angle of the launch wave to the water surface, the water level measured by the water level gauge above the open channel, and the channel width.

[0007]

[Action]

 According to the present invention, ultrasonic waves are emitted from the transmitter above the open channel obliquely to the water surface, and the reflected wave from the water surface is received by the receiver, whereby the flow velocity is obtained, while the water level meter is used. The water level is measured, and the flow rate is calculated from the flow velocity, water level and channel width. In addition, because the ultrasonic transmitter and receiver are placed above the open channel, the installation and maintenance work can be performed easily, and the measurement of flow rate does not depend on the turbidity of the water, so there is no measurement error. Will be reduced. Also, since the receiver is placed in the direction in which the ultrasonic waves are reflected on the water surface, it is possible to set a large allowable range of measurable water level fluctuations.

[0008]

【Example】

 Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a flow rate measuring device according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes an open water channel having a constant water channel width B. Above this open water channel 1, a transmitter 2 which emits ultrasonic waves obliquely from above at an incident angle α to the water surface S, The receiver 3 which receives the reflected wave from the water surface S is arranged in a substantially symmetrical positional relationship with the vertical axis X on the water surface S, and the ultrasonic wave emitted from the transmitter 2 has a certain spread to the emitted wave U0. It is kept. Reference numeral 4 denotes an arithmetic circuit connected to the receiver 3, which determines a flow velocity V from the frequency difference f0-f1 between the emitted wave U0 and the reflected wave U1, the wavelength λ of the emitted wave U0, and the incident angle α, and The water level H by the water level gauge 5 arranged above the open water channel 1 and the flow rate Q from the water channel width B are calculated based on the equation Q = B · H · V.

Next, the operation of the above configuration will be described. The ultrasonic wave U0 is emitted from the transmitter 2 to the water surface S with a predetermined spread, and the reflected wave U1 reflected by the water surface S is received by the receiver 3. At this time, the arithmetic circuit 4 receiving the output of the receiver 3 performs the following arithmetic operation.

Now, it is assumed that the emission wave U0 from the transmitter 2 is represented as U0 = Acos (ω0t + θt) and the reflected wave U1 = Acos (ω1t + θ1) from the water surface S (however, A Is a constant). The frequency f0 of the launch wave U0 = ω0 / 2π changes to f1 = ω1 / 2π due to the Doppler effect when reflected by the water surface S. Here, since f0 = C / λ and f1 = (C + Vcosα) / λ, the frequency difference f1−f0 = (Vcosα) λ. Therefore, the flow velocity V is obtained from V = λ (f1−f0) / cos α.

Further, the water level measurement value from the water level gauge 5 is taken into the arithmetic circuit 4. As a result, the arithmetic circuit 4 calculates the flow rate θ from the channel width B of the open channel 1, the flow velocity V and the water level H based on θ = B · H · V.

Here, the transmitter 2 installed above the open channel 1 emits ultrasonic waves to the water surface S, and uses the emitted wave U0 and the reflected wave U1 to obtain the flow velocity V and the like. It is easier to install than installing it in the water, it is not destroyed by driftwood, etc., and the operator can be freed from maintenance work from underwater. In addition, the measurement error can be reduced because the measurement can be performed without being affected by the turbidity in water. Further, the transmitter 2 and the receiver 3 are arranged substantially axially symmetrical with respect to the vertical axis X, so that the measurable water level fluctuation range can be made large.

Further, since the ultrasonic waves emitted from the transmitter 2 are spread, the receiver 3 can be easily set to the optimum position with respect to the water level change.

Note that the ultrasonic waves emitted from the transmitter 2 may have directivity as shown in FIG. 2, and in that case, the transmitter 2 and the receiver 3 are set in the optimum directions according to the water level. do it.

Further, as shown in FIG. 3, by arranging three or more transmitters 2 in parallel and giving a phase difference to the ultrasonic waves emitted from each transmitter 2, a preferable transmission / reception angle with respect to a change in the water surface is obtained. You may choose the degree.

[0017]

[Effect of the device]

 As described above, according to the present invention, the ultrasonic transmitter and receiver are arranged in a substantially symmetrical positional relationship with the vertical axis above the water surface on an open channel with a constant channel width, and the Doppler effect of ultrasonic waves is utilized. Since the flow rate is calculated from the calculated flow velocity, the channel width and the water level, the construction work and maintenance work are easier than those installed in water, and the turbidity of water is affected. It is possible to obtain accurate measurement values without

[Brief description of drawings]

FIG. 1 is a block diagram showing a flow rate measuring device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a flow rate measuring device when a wave emitted from a transmitter has directivity.

FIG. 3 shows another embodiment of the present invention and is a configuration diagram showing a flow rate measuring device when three transmitters are arranged in parallel.

FIG. 4 is a configuration diagram showing a conventional flow rate measuring device.

[Explanation of symbols]

 1 Open channel 2 Transmitter 3 Receiver 5 Water level gauge H Water level S Water level V Flow velocity X Vertical axis

Claims (1)

[Scope of utility model registration request] 1. A transmitter for emitting ultrasonic waves obliquely to the water surface and a receiver for receiving reflected waves from the water surface with respect to a vertical axis above the water surface above an open water channel having a constant water channel width. Are placed in a substantially symmetric positional relationship, the flow rate obtained from the frequency difference between the emitted wave of the ultrasonic wave and the reflected wave, the wavelength of the emitted wave and the incident angle of the emitted wave with respect to the water surface, and the water level above the open channel. A flow rate measuring device configured to calculate a flow rate from a water level measured by a meter and the water channel width.