JP2000009508A - Ultrasonic wave doppler current meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To know garbage deposits at the ultrasonic wave sensor part provided in a waterway at a distance, and to know garbage depositions on the ultrasonic sensor part of the current velocity installed in a manhole without opening the lid of the manhole. SOLUTION: The ultrasonic-wave Doppler current meter obtains the power spectrum shown by the solid line, by processing a Doppler transition signal through fast Fourier transformation. A mean current velocity is found by using the frequency of a peak A. When the power of the peak A decreases below a specific ratio, it is judged that garbages are deposited. Data on the power spectrum shown in the figure are sent out and confirmed at a distance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic Doppler velocimeter, and more particularly to an ultrasonic Doppler velocimeter having a new function other than the measurement of flow velocity.

[0002]

2. Description of the Related Art An ultrasonic Doppler flowmeter for processing a Doppler shift signal by using FFT (Fast Fourier Transform), obtaining a power spectrum, obtaining an average flow velocity from a peak mountain frequency of the power spectrum, and calculating a flow rate. Is disclosed in Japanese Patent Application Laid-Open No. 9-229934. The ultrasonic Doppler flow meter is suitable for measuring the flow velocity and flow rate of an open channel, particularly a sewer, but a surface velocity flow meter is generally known for measuring the flow rate of an open channel, particularly a sewer. The ultrasonic type surface velocity flow meter calculates the flow rate from the average flow velocity measured by the Doppler velocimeter and the cross-sectional area of the flowing water obtained from the water level measurement.

The basic measured quantity of the Doppler flowmeter is the average flow velocity. The processing of the Doppler shift signal is performed by using the FFT as described in Japanese Patent Application Laid-Open No. 9-229934, and the average flow velocity is calculated from the peak frequency of the power spectrum. Ultrasonic TECHNO February 1993 Issue 71-73
Some use the zero-cross method described on the page.

In these current meters and flow meters, a circuit for amplifying an ultrasonic reception signal uses an automatic gain control (AGC) circuit or the like to amplify the reception signal to a constant value as much as possible. Was.

[0005]

In an ultrasonic Doppler velocimeter or flow meter, when dust or dirt accumulates thickly around an ultrasonic sensor unit for transmitting and receiving ultrasonic waves, the ultrasonic waves do not enter the fluid. The transmission of the sound wave and the reception of the reflected signal are disturbed and measurement becomes impossible.

When measuring the flow rate of sewage continuously over a long period of time and using the measured value for system maintenance, the measured value is collected periodically to check the accumulation of garbage and the like to improve the measurement accuracy. Need to be maintained. Some sewer pipes are larger than 3m in diameter, and for inspection, it is necessary for workers to enter through manholes installed on roads. However, safety measures against harmful gases in pipes and waterways, roads Traffic safety measures, etc. are also required, and furthermore, it will be a hindrance to traffic. Therefore, there is a problem that a great deal of labor is required for checking whether or not there is accumulation of dust and the like.

Accordingly, a first object of the present invention is to provide an ultrasonic current meter which can solve such a problem and does not cause a traffic obstacle for the inspection. FFT analysis of ultrasonic Doppler shift signal to obtain power spectrum,
The measurement method that analyzes the power spectrum and makes the local peak peak correspond to the average flow velocity is a measurement method to find the average flow velocity of the water flowing in the open channel, and erroneous measurement due to the reflection of sound waves generated on the water surface It is very effective in preventing

However, in the open channel of sewage, since the depth of the channel to be measured and the amount of suspended matter contained in the water are various, the size of the peak peak of the power spectrum is constant at all measurement sites. It is very difficult to measure with a measuring instrument set in advance.

[0009] Further, even in the same channel, the amount of particles that reflect sound waves varies greatly depending on the difference in water level. Further, during measurement, dust gradually accumulates on the front surface of the sensor, and the level of reception greatly changes.

In the conventional AGC method using the amplitude of the received signal, when the reflected wave due to the wave generated on the water surface is large or when the reflected signal is weak, the transmitted signal wraps around to the receiving side. AGC operates to reduce the target signal, and it may be difficult to amplify only the target signal greatly.

Further, an image signal of a double frequency or the like generated when a Doppler shift signal is extracted from a received signal is also subjected to FFT.
In the analysis, although the level is small, it causes a problem similar to the noise described in the previous section, and it is necessary to remove the noise.

Accordingly, it is a second object of the present invention to provide an ultrasonic Doppler velocimeter capable of preventing malfunction due to noise and improving measurement accuracy even when the measurement environment changes.

[0013]

According to a first aspect of the present invention, a power spectrum is obtained by processing a Doppler shift signal using an FFT, and a power spectrum of the power spectrum is obtained. Ultrasonic Doppler velocimeter that makes the peak mountain frequency correspond to the average flow velocity compares the power of the peak mountain with the average flow velocity with the reference value to determine the presence or absence of dust accumulation on the ultrasonic sensor in the waterway. Is an ultrasonic Doppler velocimeter.

The reference value may be a fixed value that does not change, or may be an initial value or a value that is constantly updated to a value that has been maximized by measurement. According to another aspect of the present invention, in an ultrasonic anemometer which obtains a power spectrum by performing processing of a Doppler shift signal using an FFT, and a frequency of a peak peak of the power spectrum corresponds to an average flow velocity, the Doppler An ultrasonic Doppler velocimeter characterized by transmitting data of a power spectrum of a shift signal and reproducing the power spectrum externally.

For transmission of measured value data and power spectrum data, a telephone line, a dedicated line, or an optical fiber cable can be used. The invention of claim 3 is based on claim 2
Wherein the method of communication with the outside is wireless data transmission or a simplified portable telephone system.

If a telephone line is used, information communication using the Internet can be used. In order to further achieve the second object, a fourth aspect of the present invention relates to the ultrasonic Doppler velocimeter according to the first or second or third aspect, wherein the ultrasonic wave Doppler velocimeter is capable of setting a constant peak in obtaining a peak of a power spectrum. Only the data of the power spectrum above the threshold value is processed, and the data of the power spectrum below the threshold value is ignored to prevent a malfunction due to noise. The threshold can be easily set at the time of initial installation according to the condition of the waterway.

According to a fifth aspect of the present invention, in the ultrasonic Doppler velocimeter of the fourth aspect, the threshold value is set by a personal computer external to the velocimeter, and the power spectrum of the Doppler shift signal is displayed. The set threshold value or the threshold value to be changed is displayed on the power spectrum screen. The threshold can be set to the optimum value according to the waterway.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the present invention will be described with reference to the drawings. [Embodiment 1] In FIGS. 2 and 3, reference numeral 1 denotes an inner diameter of 1.8 m.
In a water channel (pipe) having a gradient of 1/1000, the sewage 2 flows naturally from right to left as shown by the arrow in FIG. 2 in a non-full state.

The ultrasonic sensor unit 3 is mounted at the center of the bottom of the water channel 1, and a transmitting element 4 for transmitting an ultrasonic signal at a constant elevation angle θ = 30 ° with respect to the flow direction of the fluid 2 on the inclined part.
And a receiving element 5 disposed adjacent to the transmitting element 4 in substantially the same direction and receiving a reflected signal of ultrasonic waves from the suspended particles 6 in the fluid and converting the reflected signal into an electric signal. I have.
In FIG. 2, reference numeral 8 denotes the central axis of the sound beam of the transmitting element 4.

FIG. 1 is a block diagram of a signal processing circuit. A transmitting circuit unit 9 continuously amplifies a transmitting element 4 by amplifying a high frequency oscillator 10 of f ₀ = 1 MHz and a high frequency signal from the high frequency oscillator 10. And a power amplifier 11.

The receiving operation unit 12 amplifies the received signal of the receiving element 5 to about 1000 times, and mixes the output of the amplifier 13 and the signal of the transmitter 10 to obtain the frequency f ₀ ′ of the received signal. A mixer (heterodyne detection unit) that mixes the frequency f ₀ = 1 MHz of the transmission signal and the signal of the reference frequency fst of the reference frequency oscillation circuit 22 to obtain a difference frequency.
14, a half-wave rectifier circuit 15, a low-pass filter 16 as a filter unit, an A / D conversion unit for converting an output of the filter unit 16 into a digital signal, and a digital signal converted by the A / D conversion unit. A fast Fourier transform (FFT) unit 17 for obtaining a power spectrum of the difference signal
A peak detector 18 for calculating the frequency of the peak of the power spectrum obtained by the T unit 17, and a flow velocity is calculated based on the frequency of the peak obtained by the peak detector 18, and the presence or absence of dust accumulation is determined. And an operation unit 19. Reference numeral 20 denotes the next stage such as a flow rate calculation based on a display unit or a water level signal.

The frequency of the signal supplied to the transmitting element 4 is 1M
When the ultrasonic wave is emitted into the fluid as a sine wave of Hz, the receiving element 5 receives a signal including the Doppler shift frequency Δf corresponding to the flow velocity V of the fluid 2.

This signal is amplified by the amplifier circuit 13 and mixed by the mixer 14 with the frequency f ₀ of the transmission signal and the reference frequency fst. The reference frequency fst at this time is the transmission frequency f
1.0045 of a value that is a fixed frequency 4.5 kHz higher than ₀
MHz.

The frequency component of 10 kHz or more is removed by the filter unit 16 and sent to an A / D converter to be converted into a digital value. The data converted into the digital value is subjected to FFT in the FFT unit 17 and converted into power spectrum data. The power spectrum data sent to the peak ridge detection unit 18 is data of an average value obtained by performing the above measurement several times.

As shown in FIG. 4, the signal having passed through the filter after the heterodyne detection has a Doppler frequency Δf corresponding to the flow velocity and a component having a frequency of about 4.5 kHz, which is the difference between the reference frequency oscillation circuit 22 and the transmission signal. With the waveform
When the FT is performed, the power spectrum indicated by the solid line in FIG. 5 is obtained.

The power spectrum shown in FIG. 5 is averaged ten times and is moving averaged. The power spectrum of the Doppler shift signal before each averaging is a power spectrum having large irregularities as shown in FIG. It is not appropriate to determine the frequency of the peak peak corresponding to the average flow velocity.

The calculation procedure for calculating the average flow rate from the power spectrum obtained by the FFT unit 17 is as follows. . Measure and average the power spectrum several times or more.

[0028] The power having a predetermined width around the frequency corresponding to the zero flow velocity is compared, and the frequency having the maximum power is stored as the zero flow velocity frequency (peak detection of the zero flow velocity). a. The value of the power Vst at zero flow velocity is also stored.

[0029] After removing data at several points before and after the reference frequency, the data is converted into moving average data at several points before and after each point. . The power of each frequency is sequentially compared from zero frequency to the stored frequency. The power is set to a value equal to or greater than a certain threshold, and a value less than the threshold is set to zero. The power and frequency of the larger power are stored (the maximum value until then is stored).

When the value of the power for which the comparison is continued is reduced to a certain ratio of the stored value, the operation is stopped, and the value of the stored value is regarded as a peak in the forward direction. . The power from the maximum frequency to the stored frequency is successively compared in the same manner as described above, and peak peaks are detected.

[0031] The peak peak power is compared with the peak peak power, and the higher frequency is stored as the frequency corresponding to the average flow velocity. b. The power Vav corresponding to the average flow velocity is stored.

[0032] When the frequency is subtracted from the above frequency, a positive frequency difference (Δf) is obtained in the positive flow, and a negative frequency difference is obtained in the reverse flow. . The obtained frequency difference is multiplied by a coefficient such as a change in water temperature of the elevation angle and the speed of sound to convert it into a flow velocity.

C. At the start of measurement, Vx = power Vav at average flow velocity / power Vst at zero point is calculated, and the reference power ratio V
Store as 0.

D. Vx is calculated for each measurement, and when the value falls below a certain value compared to V0 and continues for a certain period of time, it is determined that dust has accumulated and stored together with the display or measured value.

E. In response to a request from the outside of the measuring instrument, the measurement data recorded so far and the average data of the power spectrum of the Doppler shift signal obtained from the measurement data are transmitted to the outside.

F. It is particularly advantageous to use a portable wireless telephone as the communication means to the outside. To perform the FFT, A
A fixed number of the / D-converted signals are stored, and a product-sum calculation is performed.
For this reason, it is necessary to determine the period of A / D conversion and the number of signals for measurement. In the embodiment, the sampling frequency is 15 kHz.
And the number of samples was 4096 points. Therefore, the resolution is about 3.7 Hz, the maximum frequency is 7.5 kHz, and the flow velocity can be measured from about 3.1 mm / s to 6.4 m / s in terms of flow velocity. The flow velocity is assigned to about -1.5 to 4.5 m / s because actual forward / reverse measurement is performed. The resolution of the flow velocity is 3.1 mm / s.

The flow velocity distribution in the water channel becomes uniform as the flow velocity increases. This is because the flow becomes a turbulent region. There is also a signal where the power spectrum of the Doppler shift is higher than the average flow velocity. One is that there is a part of the maximum flow velocity due to the curve of the flow velocity distribution, and the other is a turbulent flow area, which is 30 ° Since the measurement is performed from the direction, it is due to the signal reflected by the particles of the flow that match the measurement direction of the turbulence.

Now, the power spectrum of the Doppler shift signal is obtained by synthesizing reflected waves from a large number of dispersed points, such as dust and bubbles in water, as shown in FIG. As shown in FIG. 5, when this is averaged 10 times or more, a smooth waveform is obtained as shown in FIG. 5. The frequency of the difference between this peak A and the reference peak B is the average flow velocity. This is multiplied by a coefficient, and when the water temperature change of the sonic velocity is corrected, the average flow velocity can be obtained.

The procedure for calculating the average flow velocity in the arithmetic section from the averaged power spectrum will be described in more detail below. 1). Detection of Reference Frequency fp The peak peak that is strongest around the reference frequency fst (4.5 kHz) is detected, and the frequency fp and the power Pp of the peak peak are recorded. Since the transmitter of the reference frequency fluctuates in temperature and the like, it is measured every time and used as a reference value.

2). Flow velocity detection on the positive flow side Peaks are obtained by successively comparing spectral intensities from zero to several tens Hz before fp on the frequency side lower than fp. The maximum value and the frequency are stored, and when the signal becomes larger, the storage is updated.

The comparison of the spectrum intensities is performed for signals having a certain threshold or more. 1 /
The comparison is stopped when the value decreases by か ら from 3 and the peak is determined. This frequency is ff.

3). As in the case of backflow detection 2, the peaks are obtained by sequentially comparing the spectrum intensities from the maximum value to several tens Hz before fp on the frequency side higher than fp. The maximum value and the frequency are stored, and when the signal becomes larger, the storage is updated.

The comparison of spectrum intensities is performed for signals having a certain threshold or more. 1 /
The comparison is stopped when the value decreases by か ら from 3 and the peak is determined. This frequency is defined as fr.

4). Judgment of forward / backward flow The peaks obtained in steps 2 and 3 are compared, and the larger one is taken as the average flow velocity fl. 5). Calculation of average flow velocity A frequency corresponding to the average flow velocity is calculated by fl-fp.

Further, the following signal processing is performed for detecting the accumulation of dust according to the present invention. 6). In the first measurement, the peak peak power at the frequency fl is divided by Pp and stored. This is Pav.

The peak power of fl is compared for each measurement, and when the peak power becomes larger than the stored value, it is replaced. 7). Garbage accumulation alarm The power value of the average flow velocity for each measurement divided by Pp is Pav
Is set to be less than or equal to a certain value (set to 1/20 to 1/50), and if this continues for more than a certain time (about 30 minutes), it is determined that dust has accumulated, and the measured value is marked and displayed.

When the same time elapses when the accumulation of dust is stopped, the dust accumulation alarm is stopped. The power spectrum at the initial stage when no refuse is deposited is as shown by the solid line in FIG. 5, but when refuse is deposited, the peak A becomes A 'as shown by the dotted line.
(Power is small). A received wave from near or a surface wave with a slow flow velocity is indicated by reference symbol C.

The detection of the accumulation of dust and the flow velocity direction is determined by analyzing the power spectrum obtained by FFT of the Doppler shift signal as described above. When analyzing the situation of dust accumulation and the flow path in detail, it is better for the inspector to directly observe the FFT waveform to determine the situation, and to determine the situation in more detail.

Therefore, it is possible to configure so that the power spectrum of the averaged Doppler shift signal can be transmitted as data in response to an external request. The data transmission is RS2 of the microcomputer used for the control operation.
32C is used, and a PHS adapter for low-power wireless or PHS telephone is used for the transmission path by using optical fiber after optical conversion. Of course, you can use the telephone line without any problems.

FIG. 7 shows a PHS (simple cellular phone system) 34 which converts the measured value data of the meter 33 of the present invention provided on the manhole 32 of the road 31 and the data of the power spectrum of the Doppler shift signal to the external office 30 and the manhole 32 of the road 31. This example shows that personal computer communication is performed by the handy personal computer 35 or communication is performed via the telephone office 36, and centralized management is performed in the office 30. When the instrument 33 is temporarily installed in the manhole 32, the contents of the power spectrum data can be checked remotely, and there is no need to open the manhole cover for checking the accumulation of dust.

In the office 30 or the handy personal computer 35, the power spectrum shown in FIG. 5 is reproduced on the display (CRT) 37 of the personal computer, etc., and the administrator sees the power spectrum, and if the display shown in FIG. It can be determined that a backflow has occurred or not in the display of FIG.

As described above, the condition of the waterway can be analyzed and estimated from the change in the FFT power spectrum. Then, the administrator (person in charge) can judge the altitude by seeing a subtle signal change when an abnormality occurs.

[Embodiment 2] FIG. 9 is a block diagram of an ultrasonic Doppler velocimeter implemented by a microcomputer, and the elements denoted by the same reference numerals as those in FIG.
Since they perform the same functions as the same elements, description thereof will be omitted.

Reference numeral 12A denotes a receiving circuit unit, 16 'denotes an A / D converter, and 17 denotes an FFT unit which is constituted by a DSP. 19A
Is a microcomputer as a control unit, which has both a peak area detection unit 41, a flow velocity calculation unit 42, and a flow path area calculation and flow rate calculation unit 43 which receives a water level signal and determines whether or not there is dust accumulation. The display unit 20A is provided as needed. 40 constitutes a controller unit as a whole.

The operation of this embodiment shown in FIG. 9 is similar to that of the above-described embodiment and will not be described in detail. In both of the above embodiments, in the present invention, the average flow rate is obtained from the peak of the power spectrum, and the presence or absence of dust can be determined from the analysis of the peak power of the peak of the spectrum. The ultrasonic Doppler velocimeter using
This is not possible because neither the average flow velocity nor the effects of surface waves can be separated.

FIG. 10 is a flowchart of the calculation for detecting the frequency of the peak peak corresponding to the average flow velocity from the power spectrum of the Doppler shift signal in the first and second embodiments. This flowchart also corresponds to the calculation procedure of the maximum value of the power spectrum in the case of detecting the flow velocity on one side in FIG. FIG. 11 shows a specific example of a power spectrum in the case of a measurement method using only a positive flow, and FIG. 12 is an enlarged view of the vertical axis of FIG.

FIGS. 13 and 14 show examples of different power spectra in the case of the measurement method for measuring the forward flow and the reverse flow. As described above, the Doppler shift signal of the ultrasonic wave is
When the power spectrum is obtained by FT analysis and the average flow velocity measuring method that makes the frequency of the peak mountain correspond to the average flow velocity is applied to the open channel, the reflected wave due to the wave on the water surface is a large signal near the flow velocity (so-called noise). (For example, FIG. 1
3, the peak indicated by the symbol B in FIG. 14).

In FIG. 13, in addition to the signal of the zero flow velocity indicated by the reference sign B, an image signal of the zero flow velocity indicated by the reference sign D appears. In FIG. 14, in addition to the zero point signal B, a peak A of the average flow velocity and other noise E appear.

Further, in FIG. 12, in addition to the signal of the peak A corresponding to the average flow velocity, the noise A 'of the image signal of the double frequency of the peak A is clearly seen. In order to remove the adverse effect of noise due to the surface wave, in the above embodiment, F
The power is sequentially compared from the maximum of the frequency of the FT power spectrum, and the maximum value of the power is recorded. When the power attenuates from the maximum value to a certain value, it is recognized as a peak mountain and corresponds to the average flow velocity. .

However, the Doppler shift frequency is obtained, and F
In the case of FT analysis, a secondary image signal of the main power spectrum is generated, an image signal of a signal near the zero point (for example, an image signal of zero flow velocity indicated by a symbol D in FIG. 13), and further, a received wave itself. It is unavoidable that a double-frequency image signal (for example, a double-peak image signal indicated by the symbol A 'in FIG. 12) is generated, which causes a malfunction in signal processing.

Therefore, when the peak peak of the power spectrum is determined, as described above, processing is performed on a power value that is equal to or greater than a certain threshold (threshold), and a value less than the threshold is removed as zero. I was trying to do it.

In the initial adjustment at the start of the measurement, the peak of the average flow velocity in the power spectrum was observed, and the amplification of the receiving section was adjusted so that the peak became a certain value or more. The threshold value was programmed as a constant value in the microcomputer of the control unit.

However, when the reflected wave due to the wave generated on the water surface is large, or when the original reflected signal is weak, the transmitted signal wraps around to the receiving side. In operation, the target signal may become smaller than necessary, making it difficult to amplify only the target signal.

Further, although the image signal of the double frequency generated when the Doppler shift signal is extracted from the received signal has a small level in the FFT analysis, but has a bad influence as noise, it needs to be removed similarly to the noise described in the preceding section.

Therefore, according to a fourth aspect of the present invention, a function of removing an image signal (noise) can be achieved by changing and adjusting a threshold value set in a control unit as shown in the following embodiments. I made it.

[Embodiment 3] In Embodiment 3 shown in FIG.
An instrument (Doppler velocimeter section) 33A of the present invention connected to the ultrasonic sensor section 3 by a cable 50 is provided with a mini notebook personal computer 35A connected by an RS232C cable 51.

On the liquid crystal display 35a of the mini notebook personal computer 35A, the power spectrum calculated by the FFT by the Doppler velocimeter 33A is displayed. In the first and second embodiments, the threshold value shown in the flowchart of FIG.
In the third embodiment shown in FIG. 15, a key of the mini-notebook personal computer 35A is operated so that the value can be changed and set to an arbitrary value from outside the current meter unit.

The values that need to be set in accordance with the installation status of the water channel by the initial adjustment at the time of setting of the measuring instrument with the surface velocity flow meter include the water channel shape, dimensions, water level zero point setting, clock adjustment, Among them, the threshold value itself is designed as an external set value.

Needless to say, an appropriate default value is set when the switch is turned on. Instrument 33A
Since the threshold value is displayed on the graph when the power spectrum is displayed by the external reading / writing personal computer 35A, the initial adjustment becomes even easier because the reception amplification and AGC adjustment are not required.

The first necessary adjustment at the time of installing the ultrasonic Doppler velocimeter or flow meter at the measurement site is to confirm the zero point of the water level. This is easy to set up and there is no problem.
The second is confirmation of the received signal. That is, as shown in FIG. 16, the power spectrum of the Doppler shift shows that the peak A of the average flow velocity is larger than the threshold, and the noise A '
It is necessary to confirm that the measurement is sufficiently smaller than the threshold value and correct measurement is performed.

In order to set this accurately, conventionally, the gain of reception and the AGC signal were adjusted while observing the power spectrum with an FFT analyzer or the like. In this embodiment,
While looking at the display screen of the liquid crystal display 35a of the mini-notebook personal computer 35A, a threshold value near the middle of the peak A and much larger than the double frequency noise A 'is set as shown in FIG.

At this time, it is preferable to set the threshold value when the water level is about the middle of the change width. If the threshold value is set to a large value like this, a malfunction may occur in which the measured value becomes 0 due to fluctuations in the flow velocity (water level).

When the threshold value is set to a small value like this, when the water level rises and the peak mountain A rises, the double frequency noise A 'increases, and there is a possibility that the flow velocity about twice as high will be erroneously measured. Occurs.

Therefore, an appropriate threshold value is selected and set. The level of this set value is displayed together with the power spectrum on the liquid crystal display 35a of the personal computer 35A. [Embodiment 4] In Embodiment 4 of FIG. 17, the Doppler velocimeter unit 33A and the mini notebook personal computer 35A are connected via a wireless transmission line by PHS adapters 34A and 34B, and the lid of the manhole 32 is operated. Even if there is no communication between the current meter 33A and the mini notebook computer 35A,
The same operation as in the third embodiment can be performed.

In this case, the personal computer 35 is connected by wireless communication.
Since the power spectrum is displayed on A and the threshold is set to an appropriate level between the peak A and the noise A 'while monitoring the power spectrum with the personal computer 35A, there is no need to open the manhole cover. Communication between PHS adapters using a telephone line may be used.

[Embodiment 5] In Embodiment 5 of FIG. 18, the current meter 33A is connected to a personal computer 35B in the office via a PHS adapter 34A and a telephone office 36. A modem 52 connects the personal computer 35B to a telephone line.

In this embodiment, the flow velocity measuring unit 33A and the personal computer 35B are connected via a telephone line by PHS communication, and the power spectrum is displayed on the display 35b of the personal computer 35A. The operator sets an appropriate threshold value by key operation while monitoring the power spectrum on the display 35b. On the display screen, the level of the threshold value set so as to be superimposed on the power spectrum is displayed.

In this way, the threshold is determined while reproducing and monitoring the power spectrum in the office at a position away from the Doppler velocimeter 33A. Even if the measurement situation changes, stable measurement can be continued by adjusting the threshold value.

In the third to fifth embodiments, the threshold value set at the beginning of measurement in the control unit is set to a value that can be externally set in the same manner as the channel shape and width, and the peak value of the received signal is set to 2 to 5 V
At this time, the threshold de-alt value is set to 40, and the correction value can be written from 0 to 200 in increments of one (see FIG. 16).

In the reception, the power spectrum of the Doppler shift of the received signal is displayed on the displays 35a and 35b and the threshold is also displayed. The threshold value is preferably set in the middle between the noise A 'and the peak peak A of the average flow velocity as shown by the reference numeral in FIG. 16. In the embodiment, the setting state can be monitored, so that the setting state can be easily changed. It can be confirmed and can be measured stably for a long time in the best condition.

The setting operation is simple and accurate because only the numerical values on the display screens of the personal computers 35A and 35B are set and the writing process is performed.

[0082]

The ultrasonic Doppler velocimeter of the present invention is constructed as described above. Since the reliability of the measured value due to the accumulation of garbage can be displayed, recorded and transmitted, the reliability of the measurement could be increased.

2. The maintenance of the sensor unit of the measuring instrument and the necessity of removing dust can be judged without raising the ultrasonic sensor unit from the water, and significant labor saving was achieved. 3. In particular, since the measured values can be measured remotely using wireless or PHS, it is possible to judge the necessity of maintenance without opening the manhole usually installed on the road, without obstructing traffic, and This greatly contributed to the work safety.

4. Since the power spectrum of the Doppler shift signal can be received from outside as well as the judgment of the dust by the computer, the receiving device and the handy PC can not only judge the accumulation status of the dust but also check the status of the waterway at the measurement center at the measurement center. Administrators can now estimate subtleties.

Further, in this method, measurement data can be collected very easily. 5. The relative decrease in the received signal due to a large signal near the zero point of the flow velocity due to the reflection of waves generated on the water surface due to the conditions of each measurement site, the design flow velocity due to the gradient of the water channel, the roughness of the wall surface, etc. Use a personal computer (handy type) for setting against the change in the size of the peak peak of the average flow velocity due to the amount of suspended matter and bubbles, etc., without using tools or measuring instruments when installing the instruments. You can easily check the measurement status and set the required values. That is, the initial adjustment can be performed by setting the threshold value without adjusting the reception sensitivity and the amplification degree, and the adverse effect of noise can be reduced.

6. Using a PHS phone or optical fiber communication, the measured value is monitored remotely, the power spectrum of the received signal is monitored to diagnose the measurement condition, and the received signal is monitored in response to the accumulation of dust and changes in the measurement condition. By changing the hold value, it became possible to continue the optimal measurement, and from this aspect, it was possible to reduce the adverse effects of noise.

7. When the PHS telephone is used in the wireless communication mode, the instrument installed in the manhole can determine the flow state in a non-contact manner without opening the manhole, determine the accumulation of garbage, and greatly reduce the maintenance man-hours. Was.

This is effective when a repeater for connecting to a place other than the telephone service area or a telephone line cannot be installed.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a vertical sectional front view of a water channel according to the embodiment of the present invention.

FIG. 3 is a vertical sectional view of a water channel according to the embodiment of the present invention.

FIG. 4 is a diagram illustrating an output waveform of a filter unit according to the embodiment of the present invention.

FIG. 5 is a power spectrum diagram obtained by averaging FFT-doppler shift signals according to the embodiment of the present invention.

FIG. 6 is a power spectrum diagram of a Doppler shifted signal subjected to FFT according to the embodiment of the present invention.

FIG. 7 is a schematic diagram of a data transmission system according to an embodiment of the present invention.

FIG. 8 is a diagram in which a power spectrum transmitted by data is reproduced in the example of the present invention.

FIG. 9 is a block diagram of a second embodiment of the present invention.

FIG. 10 is a flowchart of a calculation procedure of a maximum value (peak peak) of a power spectrum in the case of detecting a flow velocity on one side (positive flow side) in the embodiment of the present invention.

FIG. 11 is a power spectrum diagram of a positive flow measurement method according to the embodiment of the present invention.

FIG. 12 is an enlarged view of the vertical axis of the power spectrum diagram of FIG. 11;

FIG. 13 is an example of a power spectrum diagram of the forward / backward flow measurement method in the embodiment of the present invention.

FIG. 14 is another example of a power spectrum diagram of the forward / backward flow measurement method in the embodiment of the present invention.

FIG. 15 is a schematic diagram of a data transmission system according to a third embodiment of the present invention.

FIG. 16 is a diagram illustrating setting of a threshold on the power spectrum diagram of FIG. 12 in the embodiment of the present invention.

FIG. 17 is a schematic diagram of a data transmission system according to a fourth embodiment of the present invention.

FIG. 18 is a schematic diagram of a data transmission system according to a fifth embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 1 water channel 2 sewage 3 ultrasonic sensor unit 4 transmitting element 5 receiving element 6 suspended particles 17 fast Fourier transform unit (FFT
18) Peak mountain detector 19 Operation unit 30 Office 33, 33A Instrument (Doppler current meter) 34, 34A, 34B PHS adapter 35, 35A, 35B Personal computer 36 Telephone office 37, 35a, 35b Display A Peak mountain

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Noriaki Nagata 2-70, Millennial, Atsuta-ku, Nagoya-shi, Aichi F-term in Aichi Watch Electric Co., Ltd. 2F035 DA12 5J083 AA02 AB20 AC18 AD12 AE10 AF01 BE05 BE14 BE18 BE19 BE45 BE53 CA01 DA01 EB04

Claims (5)

[Claims] 1. An ultrasonic Doppler velocimeter for processing a Doppler shift signal using an FFT to obtain a power spectrum, and making the peak mountain frequency of the power spectrum correspond to the average flow velocity. An ultrasonic Doppler velocimeter characterized by comparing with a reference value and judging the presence or absence of debris in an ultrasonic sensor in a waterway. 2. An ultrasonic velocimeter for processing a Doppler shift signal by using an FFT to obtain a power spectrum and making a peak mountain frequency of the power spectrum correspond to an average flow velocity. An ultrasonic Doppler velocimeter characterized by transmitting power spectrum data and reproducing the power spectrum externally. 3. The ultrasonic Doppler velocimeter according to claim 2, wherein the external communication method is a wireless data transmission or a simple portable telephone system. 4. When calculating a peak peak of a power spectrum, only data of a power spectrum equal to or higher than a predetermined threshold which can be set is processed, and data of a power spectrum lower than the threshold is ignored, thereby causing malfunction due to noise. 4. The ultrasonic Doppler velocimeter according to claim 1, wherein the ultrasonic wave is prevented from being generated. 5. A threshold value is set by a personal computer external to the anemometer, a power spectrum of the Doppler shift signal is displayed, and the set threshold value or a threshold value to be changed is displayed on a power spectrum screen. The ultrasonic Doppler velocimeter according to claim 4, characterized in that: