WO2007004384A1

WO2007004384A1 - Pulse doppler ultrasonic flowmeter and program thereof

Info

Publication number: WO2007004384A1
Application number: PCT/JP2006/311414
Authority: WO
Inventors: Yoshinori Ohmuro; Toshihiro Yamamoto; Hironobu Yao; Kazuyuki Yamada
Original assignee: Fuji Electric Systems Co., Ltd.
Priority date: 2005-06-30
Filing date: 2006-06-07
Publication date: 2007-01-11
Also published as: JP4548485B2; JPWO2007004384A1

Abstract

A Doppler frequency distribution measuring part (11) measures a Doppler shift frequency distribution. A frequency distribution correcting part (12) determines a part of the Doppler shift frequency distribution that is affected by 'aliasing', and corrects the measurement value of the Doppler shift frequency of that part, thereby obtaining a correct Doppler shift frequency distribution. When the actual value of the Doppler shift frequency exceeds a measurement limit defined by the repetition frequency, the measurement value is a value as affected by the 'aliasing'.

Description

Specification

Pulsed Doppler ultrasonic flow meter, its program

Technical field

[0001] The present invention relates to a pulsed Doppler ultrasonic flow meter.

Background art

[0002] A clamp-on type ultrasonic flowmeter is equipped with an ultrasonic transducer (a module that transmits and receives an ultrasonic pulse of an arbitrary frequency) on a part of the outer peripheral surface of a tubular body such as a water pipe. This is a flow meter that measures the flow velocity of the fluid flowing through the outside of the tubular body. Clamp-on type ultrasonic flowmeters can be broadly classified into the propagation time difference type and the pulse-Doppler type.

[0003] The propagation time difference equation is the difference in time required for ultrasonic waves to travel in the forward and return paths by reciprocating the ultrasonic waves in a path that crosses the fluid flowing inside the tubular body diagonally. In other words, the flow rate of the fluid is measured.

[0004] On the other hand, the pulse-Doppler method is based on the assumption that suspended particles and bubbles contained in a fluid move at the same speed as the fluid, and measures the flow rate of the fluid from the moving speed of the suspended particles and bubbles. It is. This is because the frequency of the ultrasonic wave that is transmitted to the fluid and reflected by suspended particles changes due to the Doppler effect, so the flow velocity distribution of the fluid is calculated based on the frequency deviation, and the flow velocity distribution Is used to calculate the fluid flow rate.

[0005] Such a pulse-Doppler flow measurement technique as described in Patent Document 1, for example, enables non-contact and highly accurate measurement of a non-steady state fluid. In this technology, an ultrasonic pulse with a frequency f is repeatedly applied to the fluid to be measured at a constant frequency f.

0 Transmits at prf intervals and receives ultrasonic echoes reflected by reflectors on the survey line. Based on this, the Doppler shift frequency is calculated to determine the flow velocity distribution of the fluid to be measured, and the flow rate can be measured by deriving the flow rate by integration based on this flow velocity distribution.

[0006] Regarding the flow rate measurement technique using the pulse-Doppler method, Patent Document 2 discloses that the flow rate measurement range is doubled by shifting the flow rate measurement range to either positive or negative. A flow rate switching technique is presented.

[0007] The pulse-Doppler method is a method for obtaining a flow rate by calculating Doppler shift frequencies at a plurality of points (hereinafter referred to as channels) in a pipe, calculating a flow velocity thereof, and integrating the cross section of the pipe. The flow velocity is also calculated by the following equation (1) for the Doppler shift frequency force:

[0008] [Equation 1]

c

2 x / ₀ x sin α

/. : Transmission frequency,: Maximum fluid velocity, _Cw : Fluid sound velocity,

a: Underwater incident angle, f _fd Doller-shift frequency,,, ( ₁ )

However, the Doppler shift frequency f can be measured only within a range determined by the pulse repetition frequency f (a range of 1 f / 2 to f / 2) according to the sampling theorem.

Thus, in the technique of Patent Document 2 described above, the measurement range that has been assigned equally to positive and negative is assigned only to positive or only negative. Therefore, doubling the measurement range does not really double the measurement range itself. In other words, if only positive, the measurement range is 0 to f, and if only negative, the measurement range is only f to 0. In other words, the measurement range is the value of the pulse repetition frequency f after all, and cannot be increased any further. The above positive and negative mean the flow direction of the fluid (positive direction, negative direction).

Patent Document 1: JP 2000-97742 A

Patent Document 2: Japanese Patent Application Laid-Open No. 2004-61109 The problem of the present invention is to correct the Doppler shift frequency measurement value as appropriate even if it exceeds the measurement range determined by the Doppler shift frequency force repetition frequency. However, the present invention is to provide a pulsed Doppler type ultrasonic flowmeter that can determine the Doppler shift frequency distribution and can cope with the case where the measurement range is greatly exceeded.

Disclosure of the invention

[0010] The pulse Doppler type ultrasonic flowmeter of the present invention is a pulse Doppler type ultrasonic flowmeter that measures the flow rate of a fluid to be measured that flows in a pipe using ultrasonic Doppler shift. Delivering ultrasonic pulses to the fluid under measurement at a pulse repetition frequency; A first channel force in the vicinity of the pipe wall of the pipe, and a Doppler shift frequency measuring means for measuring the Doppler shift frequency of each channel up to the m-th channel in the center of the pipe; and the Doppler shift frequency measurement Based on the Doppler shift frequency distribution up to the m-th channel, the first channel force obtained from the measurement results obtained by the means is used to determine the channel range affected by the aliasing, and each channel within the calculated channel range is obtained. The Doppler shift frequency distribution correction means for correcting the measured value of the Doppler shift frequency using the correction value obtained based on the measurement range of the Doppler shift frequency, and the Doppler shift corrected by the Doppler shift frequency distribution correction means A flow rate calculating means for determining a flow rate of the fluid to be measured using a frequency distribution. Configured to.

[0011] As described above, in the pulse Doppler ultrasonic flowmeter, the measurement range of the Doppler shift frequency is determined by the pulse repetition frequency f. Doppler shift frequency force this

prf

If the measurement range is exceeded, the measurement value is obtained as an incorrect value affected by the aliasing.

Accordingly, in the above-described Norsdoppler ultrasonic flowmeter of the present invention, the Doppler shift frequency measurement value is affected by the aliasing by the Doppler shift frequency distribution correcting unit. Are determined, and the measured Doppler shift frequency value of each channel is corrected using the correction value.

[0013] In the pulse Doppler type ultrasonic flowmeter having the above-described configuration, for example, the Doppler shift frequency distribution correcting means determines the channel where the aliasing occurs and also already aliases in the first channel. If the first channel is not affected by folding, the first channel force Doppler of each channel in the range up to the channel where the folding occurs is determined. The measured value of the shift frequency is not corrected, the measured value of the Doppler shift frequency of each channel in the range from the channel where the aliasing occurs to the m-th channel, and the measured range of the Doppler shift frequency is the corrected value. As a correction.

[0014] The flow velocity of the fluid to be measured is not uniform at the center of the tube but faster than the vicinity of the tube wall. Therefore, the absolute value of the Doppler shift frequency is larger in the center of the tube than in the vicinity of the tube wall. As a result, the channel in the vicinity of the tube wall is affected by folding, but the channel in the center of the tube is folded. It is usually not possible to be unaffected by repeated actions. Conversely, it is possible that the channel near the tube wall is not affected by folding, but the channel in the center of the tube is affected by folding. Thus, in the above configuration, if there is a fold-back location, the channel in the range up to the center of the tube is also affected by the fold-back, and correction is performed using the measurement range f as a correction value. Do.

prf

[0015] Further, in the pulse Doppler type ultrasonic flowmeter having the above-described configuration, for example, the Doppler shift frequency distribution correction means determines the channel where the aliasing occurs and also already in the first channel. When it is determined whether or not the force is affected by folding, if the first channel is affected by folding, the first channel force is also applied to each channel in the range up to the channel where the folding occurs. The measured value of the Doppler shift frequency is corrected using the measurement range of the Doppler shift frequency as the correction value, and the Doppler shift frequency of each channel in the range from the channel where the aliasing occurs to the m-th channel is performed. The measurement value is corrected with the correction value being twice the measurement range of the Doppler shift frequency.

[0016] All channels may be affected by aliasing. In this case, if there is a turn-up point, the channel in the range of the force to the center of the pipe is double affected by the turn-up. Therefore, for channels in this range, twice the measurement range (2f) is used as the correction value. Of course, the return from the first channel

prf

For each channel in the range up to the raw location, the measurement range f is used as a correction value for correction.

prf

I do.

[0017] Further, in the pulse Doppler type ultrasonic flowmeter having the above-described configuration, for example, the Doppler shift frequency distribution correction means determines the channel where the aliasing occurs, and already in the first channel. It is determined whether or not the force is affected by the folding, and if the first channel is not affected by the folding and there are a plurality of places where the folding occurs, 1 is determined from the first channel. The measured value of the Doppler shift frequency of each channel in the range up to the channel where the first fold occurs is not corrected, and the range from the channel where the first fold occurs to the m-th channel is an even number. The channel force at the occurrence of the fold The range up to the channel where the fold occurs is not corrected, and the range from the odd number of the fold occurrence channel to the even number of the fold occurrence channel is! The measured value of the Doppler shift frequency of each channel is corrected using the measured range of the Doppler shift frequency as the correction value.

[0018] As described above, since the absolute value of the Doppler shift frequency is greater in the center of the tube than in the vicinity of the tube wall, the Doppler shift frequency distribution up to the tube center force, for example, near the tube wall is, for example, the flow is in the positive direction. In some cases, the force is basically increasing. If there is a local flow velocity fluctuation, it may decrease partially. In this case, there may be multiple places where wrapping occurs. With the above configuration, even when there is a local fluctuation in the flow velocity, it is possible to correct the measured value of the Doppler shift frequency without any problem and obtain a correct Doppler shift frequency distribution.

[0019] Further, in the pulse Doppler type ultrasonic flowmeter having the above-described configuration, for example, the Doppler shift frequency distribution correction means determines the channel where the aliasing occurs and also already in the first channel. It is determined whether or not the force is influenced by folding, and when the first channel is affected by folding and there are a plurality of places where the folding occurs, the first channel is Correct the measured value of the Doppler shift frequency of each channel in the range up to the channel where the first aliasing occurs, using the measurement range of the Doppler shift frequency as the correction value, and the location where the first aliasing occurs For the range from the channel No. to the m-th channel, the odd-numbered aliasing loops from the channel where the folding occurs. For the range up to the channel where the occurrence occurred, the measured value of the Doppler shift frequency of each channel in the range is corrected using the measured range of the Doppler shift frequency as the correction value. Channel force at the place where the fold occurs For the range up to the channel where the fold occurs at the even number, the measured value of the Doppler shift frequency of each channel within the range is double the measurement range of the Doppler shift frequency. The correction value is corrected.

[0020] Even in the above configuration, even when there is a local fluctuation in the flow velocity, it is possible to correct the measurement value of the problematic Doppler shift frequency and correct to obtain a Doppler shift frequency distribution. it can.

[0021] Further, in the pulse Doppler type ultrasonic flowmeter having the above-described configuration, for example, the Doppler shift frequency distribution correction means further determines the flow direction of the fluid to be measured, and the determined flow direction. Is the positive direction, the correction is a process of adding the correction value to the measured value of the Doppler shift frequency of each channel.

Similarly, in the pulse Doppler type ultrasonic flowmeter having the above-described configuration, for example, the Doppler shift frequency distribution correction means further determines the flow direction of the fluid to be measured, and determines the determination. When the flow direction is a negative direction, the correction is a process of subtracting the correction value from the measured value of the Doppler shift frequency of each channel.

[0023] The flow direction of the fluid to be measured is determined from the range from the first channel to the channel where the folding occurs or the channel where the measured value of the first channel force and the Doppler shift frequency crosses zero. Calculate the cumulative addition value or average value of the measured values of the Doppler shift frequency of each channel in the range, and if the calculated cumulative addition value or average value is a positive value, the value is positive or negative. Is the negative direction.

[0024] Even when the object to be measured is one in which the flow direction of the fluid to be measured is reversed depending on, for example, the time zone, the flow direction is automatically determined without any human intervention at any time by the above configuration, and the flow Correction processing can be performed according to the direction, and it can be handled by installing only one flow meter.

According to the pulse Doppler ultrasonic flowmeter of the present invention, even when the Doppler shift frequency exceeds the measurement range determined by the repetition frequency, a correct Doppler shift frequency distribution can be obtained by performing correction processing. In effect, the measurable range of the Doppler shift frequency can be made larger than the measurement range determined by the repetition frequency. In particular, even if the Doppler shift frequency force is a value that cannot be measured using the method of Patent Document 2, it can be measured. Furthermore, it is possible to deal with both positive Z and negative as well as only one of positive Z and negative.

Brief Description of Drawings

FIG. 1 is a block diagram of a pulse Doppler ultrasonic flow meter.

FIG. 2A is an example of a measurement result of a Doppler shift frequency exceeding the measurement range. FIG. 2B is an example of a measurement result of the Doppler shift frequency exceeding the measurement range.

[Fig. 3A] An example (part 1) of the measurement result of the Doppler shift frequency exceeding the measurement range.

FIG. 3B is a diagram showing flow direction determination for the example of FIG. 3A.

[FIG. 3C] An example of frequency correction of the measurement result of FIG. 3A.

[Fig. 3D] This is an example (part 2) of the measurement result of the Doppler shift frequency exceeding the measurement range.

FIG. 3E is a diagram showing flow direction determination for the example of FIG. 3D.

[FIG. 3F] An example of frequency correction of the measurement result of FIG. 3D.

[Fig. 4A] An example (part 3) of the measurement result of the Doppler shift frequency exceeding the measurement range.

FIG. 4B is a diagram showing the flow direction determination for the example of FIG. 4A.

[FIG. 4C] An example of frequency correction of the measurement result of FIG. 4A.

[Fig. 4D] An example of measurement results of the Doppler shift frequency exceeding the measurement range (No. 4).

FIG. 4E is a diagram showing the flow direction determination for the example of FIG. 4D.

[FIG. 4F] An example of frequency correction of the measurement result of FIG. 4D.

[5] FIG. 5 is a flowchart schematically showing the entire flow rate calculation process.

FIG. 6 is a detailed flowchart of the process of step S2 of FIG.

FIG. 7 is a detailed flowchart of the process of step S3 of FIG.

FIG. 8 is a detailed flowchart of the process of step S38 of FIG.

FIG. 9 is a detailed flowchart of the process in step S39 of FIG.

FIG. 10 is a detailed flowchart of the process of step S41 of FIG.

FIG. 11 is a detailed flowchart of the process of step S42 of FIG.

[12A] This is an example of a measurement result of the Doppler shift frequency that exceeds the measurement range and has local variations.

FIG. 12B is a diagram showing the flow direction determination for the example of FIG. 12A.

FIG. 12C is an example of frequency correction of the measurement result of FIG. 12A.

FIG. 13A is an example of a measurement object whose fluid flow direction changes.

FIG. 13B is an example of a measurement object whose fluid flow direction changes.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the pulse Doppler type ultrasonic flowmeter of the present embodiment.

The illustrated pulse Doppler type ultrasonic flowmeter includes an ultrasonic transducer 1, an emitter 2, a transmitter 3, an amplifier 4, an AZD converter 5, a display device 6, and a CPU 10.

The periodic signal output from the transmitter 3 is input to the emitter 2, and the emitter 2 generates an electrical pulse for causing the ultrasonic transducer 1 to transmit an ultrasonic pulse from the periodic signal, and the ultrasonic transformer. Enter into user 1. The ultrasonic transducer 1 sends an ultrasonic pulse into the fluid through the pipe wall by this electric pulse, and receives a reflected echo. The reflected echo is converted into an electrical signal by the ultrasonic transducer 1 and amplified by the amplifier 4. The amplified electrical signal and the periodic signal of the transmitter 3 (that is, the signal of the transmission wave and the reception wave) are converted into a digital signal by the AZD converter 5 and input to the CPU 10.

[0029] The ultrasonic transducer 1 is installed on the pipe wall 7 of the pipe, transmits an ultrasonic pulse toward the pipe wall 8 on the opposite side, and is in the middle (included in the fluid, Receives reflected echoes reflected by reflectors 9 such as bubbles (moving at approximately the same speed as the fluid)

The CPU 10 includes a Doppler frequency distribution measurement unit 11, a frequency distribution correction processing unit 12, and a flow rate calculation processing unit 13. The Doppler frequency distribution measurement unit 11 measures the Doppler shift frequency of each channel to obtain the Doppler frequency distribution in the range from the tube wall 8 to the center of the tube as shown in FIG. That is, the frequency difference between the transmission wave and the reception wave output from the AZD transformation 5 is obtained. The frequency distribution correction processing unit 12 uses the Doppler shift frequency of each channel obtained by the Doppler frequency distribution measurement unit 11 to calculate the cross section of the pipe (actually the pipe center force pipe wall 8 (the opposite pipe wall)). Range) Doppler shift frequency distribution. The flow rate calculation processing unit 13 obtains a flow velocity distribution based on the Doppler shift frequency distribution, and calculates a flow rate based on the flow velocity distribution.

Note that the Doppler frequency distribution measurement unit 11 may be realized by a dedicated circuit. In this case, the output of AZD Transform 5 is input to this Doppler frequency distribution measurement circuit. The Doppler frequency distribution power obtained by this circuit is input to CPU10. In any case, the Doppler frequency distribution measurement unit 11, the above circuit, and the flow rate calculation processing unit 13 are existing configurations, and thus will not be described in detail.

A feature of the present invention resides in the frequency distribution correction processing unit 12. That is, in the conventional frequency distribution calculation processing unit, when the flow velocity is fast, that is, there is a portion where the Doppler shift frequency exceeds the range determined by the repetition frequency f (range of 1 f / 2 to f / 2). is there

prf prf prf

In this case, since the “folding” occurs, the distribution of the calculated Doppler shift frequency is wrong, and the flow velocity distribution and flow rate are calculated based on this Doppler shift frequency distribution. The frequency distribution correction processing unit 12 according to the present invention corrects the Doppler shift frequency distribution in which the “folding” has occurred to the correct one. . This makes it possible to calculate the correct flow velocity distribution and flow rate even when “turning” occurs.

Here, the “folding” will be described.

Figures 2A and 2B show the Doppler shift frequency distribution when "folding" occurs.

FIG. 2A shows an example in which the flow is in the positive direction, and FIG. 2B shows an example in which the flow is in the negative direction. In addition, as shown in Fig. 1, the flow is positive or negative when the transmission direction of ultrasonic pulses is upstream of the flow, and the flow is normal when the flow direction is opposite. Distinguishes from “negative direction”. Usually, if the Doppler shift frequency is a positive value, it can be identified as “flow is positive”, and if the Doppler shift frequency is a negative value, it is identified as “flow is negative”. However, when "folding" occurs, there are both a positive part and a negative part of the Doppler shift frequency as shown in Fig. 2A and Fig. 2B. In the example, the value of the Doppler shift frequency near the pipe wall 8 (range from channel 0 to channel i) is correct! /, So that no wrapping occurs, so in Figure 2A the Doppler around the pipe wall 8 Since the shift frequency is positive, the flow can be determined as the positive direction, and similarly, the flow can be determined as the negative direction in Fig. 2B.The method of determining the flow direction when "folding" occurs will be described later.

[0035] In the example of Fig. 2A, since the flow is in the positive direction, the channel 0 force near the tube wall 8 gradually increases toward the center of the tube (as described above, the value of the Doppler shift frequency increases). Prf prf shows the case where the Doppler shift frequency in the channel i shown is almost f / 2, and the Doppler shift frequency of the next channel i + 1 exceeds f / 2

Yes. In this case, as shown in the figure, the Doppler shift frequency of channel i + 1 becomes approximately −f / 2 due to “folding”, and the value of the Doppler shift frequency after channel i + 2 is −f

prf

It gradually increases again from / 2. That is, in this example, channel i + 1 to the center pipe prf

The channel range up to channel m (i + l to m) is affected by 'folding', and the Doppler shift frequency value is wrong.

[0036] In the example of Fig. 2B, in contrast to Fig. 2A, the Doppler shift frequency value gradually decreases from the channel near the tube wall 8 toward the center of the tube (the absolute value of the flow is fast because the center of the tube is fast). As it increases, when it exceeds f / 2, it becomes f / 2 by "wrapping" and from there

prf prf

It will decrease.

FIG. 3 and FIG. 4 show examples of Doppler shift frequency distributions when the above “folding” occurs and examples of Doppler shift frequency distributions corrected by the frequency distribution correction processing unit 12.

[0038] The Doppler shift frequency distribution when the “turnback” occurs is roughly divided into four patterns. That is, there are four patterns shown in FIGS. 3A, 3D, 4A, and 4D. Of these, FIGS. 3A and 4A are the same as those shown in FIGS. 2A and 2B. That is, the channel near the tube wall 8 is not affected by “folding”, and the measured value of the Doppler shift frequency is a correct value. Somewhere in the range from the channel to the channel m in the center of the tube. In the range up to the channel “m” in the center of the tube where “folding” occurs, the measured value of the Doppler shift frequency is incorrect due to the influence of “folding”. It's something that gets value.

On the other hand, FIGS. 3D and 4D show patterns in which “folding” has already occurred in a channel (channel 0 or the like) near the tube wall 8. Further, in this example, “folding” occurs immediately before channel i + 1. In other words, in the range from channel i + 1 to channel m, it is doubly affected by “folding.” The same applies to FIG.

FIG. 3C shows the frequency distribution corrected by the frequency distribution correction processing unit 12 in FIG. 3A. Similarly, Figure 3F for Figure 3D, Figure 4C for Figure 4A, and Figure 4 for Figure 4D. F is the frequency distribution corrected by the frequency distribution correction processing unit 12. Naturally, the corrected frequency distribution is correct.

[0041] As shown in FIG. 3C, the frequency distribution shown in FIG. 3A is correct for channel 0 to channel, but is incorrect for channel i + 1 and later, and in fact for channel i + 1 and later, all exceed f / 2.

Furthermore, it exceeds f near the center of the pipe, and is close to 3Z2f. Yotsu

prf prf

Thus, even if the method of Patent Document 2 is used, “folding” occurs in the portion beyond f.

prf

As a result, the Doppler shift frequency distribution is incorrect and the flow rate measurement result is incorrect.

[0042] The frequency distribution correction processing unit 12 first determines which of the above four patterns corresponds, and executes correction processing for the corresponding pattern, thereby correcting the wrong frequency distribution to the correct one. To do.

[0043] When the frequency distribution shown in FIG. 3A is corrected, basically, the portion where the “folding” occurs (channel i + 1) is obtained, and all channels after this channel i + 1 (channel i +) are obtained. Add f to the Doppler shift frequency (from 1 to the channel m in the middle of the tube)

prf

The same applies to the pattern of FIG. 4A. However, “addition” is not “subtraction”). However, it is desirable to be able to cope with local fluctuations, as in the processing example described later.

[0044] The channel where the “folding” occurs can be determined by the fact that the difference from the previous channel i is f / 2 or more, as shown in FIG. Channel i and chir prf

The frequency difference from the channel i + 1 is very large (approximately f) and the adjacent channel

ρπ

It is usually not possible to have a frequency difference of more than ^ / 2 (only when "folding" occurs)

prf

) Therefore, of course, the threshold for judging the occurrence of “folding” should be “f / 2 or more”.

prf

Any value is possible as long as it is not normally possible (for example, “2f / 3 or more”). this is,

prf

The same applies to other patterns (as shown in FIGS. 3E, 4B, and 4E).

On the other hand, in the case of the patterns of FIGS. 3D and 4D, the channel 0 to channel i values are also affected by the “turnback”. Further, the channel i + 1 to the channel _m are affected by “folding” twice, so that in the case of FIG. 3D, the Doppler shift frequency of the channel 0 to the channel i is basically changed. Adds f, channel i + 1 to channel

prf

Add 2 Xf to the Doppler shift frequency of the part m. However, later explained It is desirable to be able to cope with local fluctuations as in the processing example. As a result, the Doppler shift frequency distribution shown in FIG. 3F is obtained. The same is true for Figure 4D, but “subtraction”, not “addition”.

[0046] As shown in FIG. 3F, the Doppler shift frequency of the channel m at the center of the tube exceeds 3f / 2.

prf

Therefore, the conventional technology cannot measure (even using the method of Patent Document 2).

As described above, according to the pulse Doppler ultrasonic flowmeter of this example, since the flow velocity is very fast, it is determined by the Doppler shift frequency value force S pulse repetition frequency f.

prf

Even if the measurement range is greatly exceeded (more than 2 times or more than 3 times), the flow velocity / flow rate calculation result can be obtained correctly by correcting the measured Doppler shift frequency distribution.

[0047] The force schematically described above for the processing by the frequency distribution correction processing unit 12 will be described in detail below with reference to the flowcharts shown in Figs. Note that the processing described schematically and the processing in the flowcharts shown in FIGS. 5 to 11 are various set values such as predetermined application programs and threshold values stored in a memory (ROM, flash memory, etc.) not shown. Is realized by the CPU 10 'reading' and executing. The same applies to the Doppler shift frequency distribution calculation process and the flow velocity / flow rate calculation process.

FIG. 5 is a flowchart schematically showing the entire flow rate calculation processing by the CPU 10. As shown in FIG. 5, in the CPU 10, first, the Doppler frequency distribution measuring unit 11 determines the Doppler shift frequency of each channel. After being calculated (step S1), the frequency distribution correction processing unit 12 first determines which of the above four patterns corresponds to the flow direction etc. by determining the flow direction (step S2). By executing the frequency shift process using the processing flow (step S3), the Doppler shift frequency distribution is corrected and corrected to eliminate the influence of “folding”.

[0049] After that, if the conventional flow rate calculation process (step S4) and flow rate calculation process (step S5) can be performed by the flow rate calculation processing unit 13 using the modified Doppler shift frequency distribution, the flow velocity of the fluid The flow velocity / flow rate can be calculated correctly even when the measurement exceeds the measurement range.

FIG. 6 is a detailed flowchart of the flow direction determination process in step S2. In the processing of Fig. 6, first, the channel closest to the wall is set as the current channel. That is, first, the channel closest to the wall is set as an object of processing in steps S12 to S15. The channel closest to the wall is channel 0 that is closest to the wall 8 above. After that, all the channels from the channel 0 closest to the tube wall 8 to the channel m at the center of the tube, such as channel 1, channel 2, etc.! Steps S12 to S15 are repeatedly executed (steps S16 and S17). In other words, the channel to be processed is channel i (i = 0 to m), i = 0 at the beginning, and i = i + 1 is performed in step S17 until i = m. Repeat step 15.

[0051] Processing in steps S12 to S15 will be described. This process is basically a process of finding and recording the “folding” occurrence point.First, the difference Pi of the Doppler shift frequency between the current channel and the next channel is calculated (the next channel i + The Doppler shift frequency of 1 is the Doppler frequency of the current channel i, and this is the difference value p for the current channel i (Step S12), and the absolute value of this difference value p is a predetermined threshold (as described above, here Then f / 2

1 prf) or higher (step S13, YES), turn on the phase displacement flag corresponding to the next channel i + 1 (step S14), and if it is below the threshold (step S13, NO), The phase displacement flag corresponding to channel i + 1 is kept OFF (step S15). Although not shown in particular, a first table in which a phase displacement flag is associated with each channel is prepared in advance. All phase displacement flags are OFF by default. The difference value P is temporarily stored. Also, as already mentioned, the above threshold is limited to f / 2.

1 ρπ

This is usually not possible except when "wrapping" occurs! Any value is acceptable.

Note that the next channel is a channel adjacent to the current channel in the center of the tube.

By creating and updating the first table by the processing described above, it can be seen that the channel force “folding” is generated where the phase displacement flag is ON.

[0053] Next, again, channel 0 closest to tube wall 8 is set as the current channel (step S18), and all channels from channel 0 to channel m at the center of the tube are sequentially processed in the same manner as in the above processing. However (steps S21 and S22), the processes of steps S19 and S20 are repeatedly executed. Although not shown in the figure, during the processing of step S18, the cumulative addition of the difference value p is performed. The variable P indicating the value is initialized (P = 0).

In the processing of steps S19 and S20, first, referring to the first table, it is determined whether or not the phase displacement flag corresponding to the next channel i + 1 of the current processing target channel i is OFF (step If it is ON (step S19, NO), no processing is performed. If it is OFF (step S19, YES), the difference value p of the current channel i is added to the variable P. (P = P + P) is performed (step S20).

[0055] When the processing of steps S19 and S20 is executed for all channels from channel 0 to channel m (step S21, YES), the current flow direction of the fluid to be measured is determined depending on whether the variable P is positive or negative. judge. That is, if variable P (cumulative addition of difference value p) is positive (step S23, YES), the flow is determined to be positive (step S24), and if variable P is negative (step S23) In step S23, NO), it is determined that the flow is in the negative direction (step S25).

[0056] When the determination in step S19 is NO, the difference value ϋ of the channel is not added to the variable Ρ, so the influence of “folding” is eliminated, and the flow direction without any problem due to the variable Ρ That is, as described above, the flow is faster in the center of the tube than in the vicinity of the tube wall. Since the flow of the next channel is faster than that of the next channel (that is, the Doppler shift frequency is large), the above difference value p. Is basically a positive value (this is influenced by “folding”). Even within this range, it is basically a positive value). However, in some cases, as shown in Fig. 12, there is a possibility that a part where the above difference value becomes a negative value partially due to local flow velocity fluctuations. Judges positive Z negative. Furthermore, since the difference value P becomes a large minus (almost –f) at the “turnback” location, in step S19 “

1 prf

Since the difference value at the “turn-back” part is excluded, the value of the variable P is always positive if the flow is in the positive direction.

[0057] It should be noted that when the flow is in the negative direction, it can be considered to be the reverse of the case of the positive direction. In other words, in this case, naturally, the flow is faster in the center of the tube than near the tube wall (therefore, the absolute value of the difference value p is larger in the center of the tube), but the flow is in the negative direction. Basically, the force closest to the tube wall The Doppler shift frequency of each channel decreases toward the center of the tube. Therefore, the difference value is a negative value (except for some of the above fluctuations), so the variable P is also a negative value.

[0058] According to the above processing, even when "turning" occurs or when a local flow velocity fluctuation occurs and V, the flow direction can be determined without error.

When the flow direction determination process in FIG. 6 is completed, the frequency shift process in step S3 in FIG. 5 is subsequently executed.

FIG. 7 shows a detailed flowchart of the frequency shift process.

Since the flow direction can be determined by the above processing, for example, when the flow is in the direction, it can be seen that the pattern is one of FIGS. 3A and 3D. 3A or 3D, as described above, whether or not the force that has already been affected by “folding” in the channel 0 nearest to the tube wall 8 that is the processing start channel (the processing reference). In the process of Fig. 7, in addition to the result of determining the flow direction described above, it is determined whether or not the force has already been affected by the "turnback" in the channel 0 closest to the pipe wall 8. It is determined which one of the two patterns is applicable, and according to the determination result, one of steps S38, S39, S41, and S42 of Fig. 7 is executed, and a detailed flow chart of step S38 FIG. 9 shows a detailed flowchart of step S39, FIG. 10 shows a detailed flowchart of step S41, and FIG. 11 shows a detailed flowchart of step S42.

[0060] In the process of FIG. 7, the average value of the Doppler shift frequency in the range up to the channel where the channel force phase displacement flag closest to the wall is ON, or the range from the closest wall to the Doppler shift frequency crossing 0 is obtained. The average value of the Doppler shift frequency is obtained.

[0061] That is, first, channel 0 closest to the wall 8 is defined as the current channel (channel to be processed) (step S31), and channel 1, 2, 3,... Sequentially, each channel is set as a processing target channel (step S35), and until the channel whose phase displacement flag is ON becomes the current channel or until the Doppler shift frequency exceeds 0 (that is, NO in step S32). Until it becomes YES in step S34), the Doppler shift frequency of each channel is cumulatively added (step S33). That is, let the Doppler shift frequency of channel i be f and the cumulative addition value of the Doppler shift frequency be If the variable shown is Q and the variable Q is initialized (Q = 0) in step S31, the process of step S33 is Q = Q + f.

fdi

[0062] It should be noted that the determination method of whether or not the Doppler shift frequency crosses over 0 is, for example, by comparing the Doppler shift frequency of the current channel i with the Doppler shift frequency of the next channel i + 1. If the value is positive and the other is negative, it is determined that the Doppler shift frequency has crossed zero.

[0063] The variable (accumulated addition value) Q obtained by the above processing is the Doppler shift frequency of each channel in the range A shown in the example of Fig. 3 if the pattern of Fig. 3A is used. The cumulative addition value Q of is obtained. In other words, in this case, NO is determined in step S3 2, and the accumulated addition value Q of the channel Doppler shift frequency of each channel in the range A is about the channel 0 force and the channel i + 1 immediately before the channel i + 1 where the phase displacement flag is ON. It will be required. If the pattern shown in FIG. 3D is used, the cumulative addition value Q of the Doppler shift frequencies of each channel in the range E shown in the figure is obtained. In other words, in this case, YES is obtained in step S34, and the accumulated calorific value Q of the Doppler shift frequency of each channel up to the channel immediately before the Doppler shift frequency crosses 0 is obtained. It will be.

As apparent from FIGS. 3A and 3D, in the case of FIG. 3A, the cumulative addition value Q is a positive value, and in the case of FIG. 3D, the cumulative addition value Q is a negative value. In the case of the pattern shown in Fig. 3A, as already mentioned, the measured value of the Doppler shift frequency in the range A from the channel 0 immediately before the tube wall 8 to the channel just before the “folding” occurrence point is correct ( Since it is a value that is not affected by “wrapping”, it is a positive value. However, taking into account the possibility that some channels have a negative Doppler shift frequency due to local fluctuations, the cumulative addition value for the entire range A is obtained (therefore, the variable Q is added to the cumulative addition value). For example, it may be an average value).

[0065] On the other hand, in the case of the pattern of FIG. 3D, the region of the range B shown in the figure (the range from the channel 0 immediately adjacent to the tube wall 8 to the channel just before the “turn-back” occurrence point) is also affected by Therefore, the Doppler shift frequency becomes wrong, and in such a case, the Doppler shift frequency of each channel in the region near the wall 8 (range E in the figure) where the flow velocity is relatively low is usually shown in the figure. As shown, although the flow direction is positive, a negative value is a component.

[0066] On the other hand, in the patterns of FIGS. 4A and 4D, the region near the tube wall 8 is affected by the “turnback”. In this case, the variable Q becomes a negative value, and the “turnback” When affected, the variable Q is positive.

[0067] From this, when the flow is in the positive direction (step S36, YES) and the variable Q is a positive value (step S37, NO), the Doppler shift frequency corresponding to the pattern of FIG. 3A. The correction process (process a) is executed (step S38). Similarly, if the flow is in the positive direction (step S36, YES) and the variable Q is negative (step S37, YES), the Doppler shift frequency correction process corresponding to the pattern in FIG. 3D ( Process b) is executed (step S39). Similarly, when the flow is in the negative direction (step S36, NO) and the variable Q is a positive value (step S40, YES), the Doppler shift frequency correction process corresponding to the pattern of FIG. 4D ( Process d) is executed (step S42). Similarly, when the flow is in the negative direction (step S36, NO) and the variable Q is negative (step S40, NO), the Doppler shift frequency correction process (process) corresponding to the pattern in FIG. 4A is performed. c) is executed (step S41).

Hereinafter, the processes a, b, c, and d will be described in detail with reference to FIGS.

First, a detailed flowchart of process a shown in FIG. 8 will be described. That is, the correction process of the Doppler shift frequency in the case where the flow is in the positive direction and is affected by the area force folding near the tube wall 8 will be described.

In the process of FIG. 8, first, the range frequency R is initialized (R = 0) (step S51). Range frequency R means the amount of correction for the Doppler shift frequency. In the case of the example in FIG. 3A, as described above, there is no need to correct the range A shown in the figure, so R = 0, and for the range C shown in FIG. Since it is only necessary to add f uniformly to the Doppler shift frequency, the range frequency R is set to f in step S56.

prf prf

[0070] In step S51, the phase-displaced flag is set to OFF. This phase-shifted flag and the processing in steps S54 to S56 are not necessary in the case of the example shown in FIG. 3A. However, due to local variations, the case in Figure 3A can be Sometimes it becomes. In the example of Fig. 12A, an arbitrary range F within the range C becomes a value within the measurement range (here, less than f / 2) because the value of the Doppler shift frequency is partially reduced due to local variation. It has become. In this case, the Doppler shift frequency in range F

prf

The number value is correct and does not need to be corrected. From this situation, the phase-shifted flag is used to distinguish whether the current channel is a force that needs to be corrected.

[0071] However, prior to the description of the processing in FIG. 8, first, the processing in the case where local variation is not considered will be described. This process is a process that does not use the phase-shifted flag in the process of FIG. That is, the process of setting the phase-shifted flag to OFF in step S51 is not necessary. Instead of the processes of steps S54 to S56, the process of simply setting the range frequency R to f may be executed. From this, the range frequency R is initialized to prf in step S51.

First, the current channel i is set to channel 0 (i = 0) closest to the tube wall 8, and it is determined whether the phase displacement flag of the current channel is ON with reference to the first table (step S53). In the case of channel 0, since the flag is OFF (step S53, NO), the process proceeds to step S57 as it is. In step S57, the Doppler shift frequency of the current channel is corrected to a value obtained by adding the range frequency R to the measured Doppler shift frequency. In the case of channel 0, since R = 0, the Doppler shift frequency remains the measured value (not corrected).

[0072] Then, until the current channel becomes channel m at the center of the tube, the same processing as described above is repeatedly executed by sequentially setting each channel from channel 0 to channel m to the current channel. Also after channel 1, until the channel whose phase displacement flag is ON becomes the current channel, the range frequency R remains 0, so the Doppler shift frequency remains the measured value (not corrected). Then, when the phase shift flag of the current channel is ON (step S53, YES), the above-mentioned “processing for setting the range frequency R to f” is performed. As a result, this channel force tube

prf

For all the channels up to the center channel m, the process of step S57 is “Doppler shift frequency = measured value of Doppler shift frequency + f”.

prf

[0073] If the processing in Fig. 10 is a processing that does not consider local fluctuations, it is the same as the above processing except that the range frequency R becomes -f.

prf

Next, with respect to the processing of FIG. 8, referring to the example of FIG. Differences with compatible processing! I will explain in a moment.

In this case, first, the range frequency R is initialized (R = 0) in step S51, and the phase-shifted flag is turned OFF. In the above processing, when the phase displacement flag of the current channel is ON (step S53, YES), simply “range frequency R¾f

The force which performed "the process to prf" differs in performing the process of step S54-S56 instead.

In the example of FIG. 12A, the phase displacement flags of the three channels k and 1 are turned ON.

That is, first in channel j and beyond the measurement range f / 2,

prf

In this example, as shown in Figure 12C, the Doppler shift frequency is partially reduced, so the Doppler shift frequency in the range from channel k to channel 1 is again measured.

prf

Less than / 2. FIG. 12C shows the corrected Doppler shift frequency distribution, that is, the original (correct) Doppler shift frequency distribution.

[0076] In this case, the Doppler shift frequency in the range of channel k to channel 1 is correct! /, So there is no need to correct it. However, in the processing that does not take into account the local variation described above, from channel j to the center of the tube All channels in the range up to channel m are corrected uniformly.

In this case, as shown in FIG. 12A, “folding” occurs in channels k and 1, so that the phase displacement flag is turned ON not only for channel j but also for channels k and 1 by the processing of FIG. It has become.

From the above, by performing the processing of FIG. 8, it is possible to correct the Doppler shift frequency distribution without any problem even when local fluctuations as shown in FIG. 12 occur.

That is, according to the processing of FIG. 8, in the example of FIG. 12, when the current channel is channel j, k, 1, the determination of step S53 is YES, and the processing of steps S54 to S56 is performed. At that time, if the phase-shifted flag is ON, the process of step S55 is executed, and if it is OFF, the process of step S56 is executed.

[0079] First, when the current channel is channel j, since the phase-shifted flag remains OFF in step S51, the process of step S56 is executed. In step S56, f is added to the current range frequency (correction value) R (R = R + f) and the phase has been shifted.

prf prf

Set the flag to ON. Here, the range frequency R remains in the state initialized in step S51, so R = 0 + f = f. From this, channel j force is also up to channel k-1 For each channel, the processing of step S57 is “Doppler shift frequency = measured value of Doppler shift frequency + f”, and the Doppler shift frequency is corrected.

prf

become.

[0080] When the current channel becomes channel k, the determination in step S53 is YES and the phase-shifted flag is ON (step S54, YES), so the process of step S55 is executed. In step S55, f is subtracted from the current range frequency R (R = R — f

prf prf

) And turn off the phase displacement flag. Here, the current range frequency R is f

Since prf exists, R = f -f = 0. From this, each channel from channel k to channel 1-1

prf prf

For the channel, the processing of step S57 is “Doppler shift frequency = measured value of Doppler shift frequency + 0”, and the Doppler shift frequency is not substantially corrected.

[0081] After that, when the current channel becomes 1, the same processing as that for channel j is performed. For each channel from channel 1 to channel m, the correction processing in step S57 is "Doppler". Shift frequency = measured value of Doppler shift frequency + f ''

prf Doppler shift frequency will be corrected.

Next, the process b shown in FIG. 9 will be described. The process in FIG. 9 is the same as the process in FIG. 8 except that the initial value ¾ of the range frequency R is set in step S61. However, the range

prf

Since the initial value of frequency R is f, for each channel in range B shown in Fig. 3D,

prf

Therefore, the processing in step S67 is “Doppler shift frequency = measured value of Doppler shift frequency + f”, and for each channel in range D, the processing in step S67 is “Doppler prf

One shift frequency = measured value of Doppler shift frequency + 2f ". Also, as shown in Figure 12

prf

If there are multiple channels for which the phase displacement flag is ON due to local fluctuations, the processing in step S67 is performed for each channel in the range corresponding to the range of channel k to channel 1 above. Doppler shift frequency = measured value of Doppler shift frequency + f "

prf.

[0083] Also, with regard to the flow of process c shown in FIG. 10, the processing power of steps S75 and S76 is “addition” in the processing of steps S55 and S56 in FIG. 8, and “addition” is “subtraction”. Because of this, the correction process in step S77 is “No correction” or “Doppler shift frequency = Dob The process is the same as the process in FIG.

prf

The description is omitted. According to the processing of FIG. 10, the range frequency R is set to R = R—f = −f in step S76 for the channel corresponding to the channel j, and then the above-described check is performed.

prf prf

For the channel corresponding to channel k, R = R + f = 0 in step S75

prf

Then, the range frequency R is again set to R = R−f = −f in step S76 for the channel corresponding to channel 1 above.

prf prf

Similarly, in the flow of process d shown in FIG. 11, the initial value of the range frequency R is set to 1 f in step S81, and the processing power of steps S85 and S86 is shown in steps S55 and 56 of FIG.

prf

Since the “subtraction” in the process in step “addition” and “addition” in the process becomes “subtraction”! /, The processing in step S87 is “Doppler shift frequency = measured value f of Doppler shift frequency”

prf

Except for the point that `` Blur shift frequency = measured value of Doppler shift frequency 2f '', Figure 8

prf

Since this process is the same as that in FIG.

When a local variation as shown in FIG. 12 occurs in the pattern as shown in FIG. 4A, the process shown in FIG. Compensates by subtracting f from the measured Doppler shift frequency, and the channel k

ρπ

Correction is not performed for each channel corresponding to ~ channel 11 and correction for subtracting f from the measured Doppler shift frequency is performed for each channel corresponding to channel 1 to channel m. Of course, prf corresponding to channel 0 to channel j-1

Correction is not performed for each channel up to the channel.

According to the processing of FIG. 11, the range frequency R is set to R = R—f = −2f in step S86 for the channel corresponding to the channel j, and then corresponds to the channel k.

prf prf

For channel, R = R + f = -f by step S85, and further to channel 1 above

prf prf

For the corresponding channel, the range frequency R is again set to R = R—f =

prf

-It will be 2f.

prf

In this case, for each channel corresponding to channel j to channel k 1, correction is performed by subtracting 2f from the Doppler shift frequency measurement value, and channel k to

prf

For each channel corresponding to channel 1 1, a correction is made by subtracting f from the measured Doppler shift frequency, and prf is applied to each channel corresponding to channel 1 to channel m above. In this case, 2f is subtracted from the measured Doppler shift frequency.

prf

Of course, for each channel from channel 0 to the channel corresponding to channel j1, correction is performed by subtracting f from the measured Doppler shift frequency.

prf

[0088] The pulse Doppler ultrasonic flowmeter of the present example considers local fluctuations, but does not consider the situation where the flow direction is partially reversed due to local fluctuations. . The reason for determining the flow direction of the fluid to be measured in this example is to cope with a system in which the flow direction of the fluid becomes positive or negative depending on, for example, a time zone.

[0089] That is, for example, reservoirs are created above and below the power plant, such as pumped-storage power generation, and the water in the lower pond is pumped up to the upper pond using nighttime power with low electricity consumption. Depending on the situation, the flow direction may be switched between nighttime and daytime when power is generated by using the drop between the upper and lower ponds. In the case of large-scale water purification plants, water is supplied from a water purification plant to multiple water stations, but it is necessary to adjust the amount of water between the water stations according to the downstream load. The direction may change.

[0090] Further, in the piping shown in FIG.

(1) In some cases, stop valves Β and Β and flow from valve C to valve D (Fig. 13Α).

(2) Otherwise, stop valves C and D and flow from valve A to valve B (Fig. 13B)

There is a case. At this time, at the point X of the pipe, the flow direction is reversed between (1) and (2). For this reason, if the flow meter installed at point X has the function of discriminating the flow direction, V can be measured with a single flow meter!

[0091] According to the pulse Doppler ultrasonic flowmeter of the present invention, even when the Doppler shift frequency exceeds the measurement range determined by the repetition frequency, a correct Doppler shift frequency distribution can be obtained by performing correction processing. In effect, the measurable range of the Doppler shift frequency can be made larger than the measurement range determined by the repetition frequency. In particular, even if the Doppler shift frequency force is a value that cannot be measured using the method of Patent Document 2, it can be measured. Furthermore, it is possible to deal with both positive Z and negative as well as only one of positive Z and negative.

Claims

The scope of the claims

[1] Using the ultrasonic Doppler shift, measure the flow rate of the fluid to be measured flowing in the pipe.

An ultrasonic pulse is sent to the fluid to be measured at a predetermined pulse repetition frequency, the ultrasonic echo is received, and the first channel force closest to the pipe wall of the pipe is set to the m-th channel in the center of the pipe. Doppler shift frequency measurement means for measuring the Doppler shift frequency,

Based on the Doppler shift frequency distribution up to the first channel force m-th channel obtained by the measurement result by the Doppler shift frequency measuring means, a channel range affected by the aliasing is obtained, and the obtained channel is obtained. Doppler shift frequency distribution correction means for correcting the measured value of the Doppler shift frequency of each channel within the range using the correction value obtained based on the measurement range of the Doppler shift frequency;

A flow rate calculating means for determining a flow rate of the fluid under measurement using the Doppler shift frequency distribution corrected by the Doppler shift frequency distribution correcting means;

A pulse Doppler type ultrasonic flowmeter characterized by comprising:

[2] The Doppler shift frequency distribution correction means determines the channel where the aliasing occurs and determines whether the force is already affected by the aliasing in the first channel.

If the first channel is not affected by aliasing, the measured Doppler shift frequency of each channel in the range from the first channel to the channel where the aliasing occurs is not corrected and the aliasing 2. The pulse according to claim 1, wherein the measured channel force of each channel in the range up to the m-th channel is corrected using the measured range of the Doppler shift frequency as the correction value. Doppler ultrasonic flow meter.

[3] The Doppler shift frequency distribution correction means determines the channel where the aliasing occurs and determines whether the force is already affected by the aliasing in the first channel.

If the first channel is affected by folding, the first channel force is also The measured value of the Doppler shift frequency of each channel in the range up to the channel where the aliasing occurs is used as the correction value, and the correction is performed, and from the channel where the aliasing occurs, the correction is performed. 3. The pulse Doppler according to claim 1, wherein the measured value of the Doppler shift frequency of each channel in the range up to the m-th channel is corrected using twice the measurement range of the Doppler shift frequency as the correction value. Type ultrasonic flowmeter.

[4] The Doppler shift frequency distribution correcting means determines the channel where the aliasing occurs, and determines whether or not the force is already affected by the aliasing in the first channel.

In the case where the first channel is affected by folding, and there are a plurality of places where the folding occurs,

The measured value of the Doppler shift frequency of each channel in the range from the first channel to the first channel where the aliasing occurred is not corrected,

The channel force at the first fold occurrence point is corrected for the range from the even-numbered fold occurrence point channel to the odd-numbered fold occurrence point channel. First, for the range from the odd-numbered channel where the aliasing occurs to the even-numbered channel where the aliasing occurs, the measured value of the Doppler shift frequency of each channel within the range is the Doppler frequency. The pulse Doppler ultrasonic flowmeter according to claim 1, wherein the measurement range is corrected as the correction value.

[5] The Doppler shift frequency distribution correction means determines the channel where the aliasing occurs, and determines whether the force has already been affected by the aliasing in the first channel,

If the first channel is affected by folding and there are multiple places where the folding occurs,

Correcting the measured value of the Doppler shift frequency of each channel in the range from the first channel to the first channel where the aliasing occurs, using the measured range of the Doppler shift frequency as the correction value, Channel force at the location where the first fold occurs The range up to the m-th channel is as follows:

The channel force at the occurrence site of the even-numbered folds For the range up to the channel at the occurrence site of the odd-numbered folds, the measured value of the Doppler shift frequency of each channel within the range is the measurement range of the Doppler shift frequency. As the correction value,

The channel force at the occurrence site of the odd-numbered aliasing For the range to the channel at the occurrence site of the even-numbered aliasing, the measured value of the Doppler shift frequency of each channel within the range is the measurement range of the Doppler shift frequency. 2. The pulse Doppler ultrasonic flowmeter according to claim 1, wherein the correction value is corrected to twice the correction value.

[6] The Doppler shift frequency distribution correction means further determines the flow direction of the fluid to be measured,

6. The correction is performed by adding the correction value to the measured value of the Doppler shift frequency of each channel when the determined flow direction is a positive direction. The pulse Doppler ultrasonic flowmeter according to any one of the above.

[7] The Doppler shift frequency distribution correction means further determines the flow direction of the fluid to be measured,

6. The correction according to claim 1, wherein when the determined flow direction is a negative direction, the correction is a process of subtracting the correction value from a measured value of the Doppler shift frequency of each channel. The pulse Doppler type ultrasonic flowmeter according to any one of the above.

[8] For each channel, an absolute value of a difference between the measured value of the Doppler shift frequency of the own channel and the measured value of the Doppler shift frequency of the adjacent channel is obtained, and the absolute value is equal to or greater than a predetermined threshold value. The pulse Doppler type ultrasonic flowmeter according to any one of claims 2 to 7, wherein a channel is used as a channel where the folding occurs.

[9] The flow direction of the fluid to be measured is determined as follows:

Accumulation of measured values of the Doppler shift frequency of each channel in the range from the first channel to the channel where the fold occurs or the range of the first channel force measured value of the Doppler shift frequency ^ Addition value or average The value is calculated, and when the calculated cumulative added value or average value is a positive value, the positive direction is set, and when the negative value is a negative value, the negative direction is set. The pulse Doppler type ultrasonic flowmeter described.

Using the ultrasonic Doppler shift, measure the flow rate of the fluid to be measured flowing in the pipe.

An ultrasonic pulse is sent to the fluid to be measured at a predetermined pulse repetition frequency, the ultrasonic echo is received, and the first channel force closest to the pipe wall of the pipe is set to the m-th channel in the center of the pipe. The first function to measure the Doppler shift frequency,

The first channel force obtained from the measurement result of the first function is also influenced by the aliasing of the Doppler shift frequency distribution up to the m-th channel, and the channel range obtained is determined. A second function for correcting the measured value of the Doppler shift frequency of each channel within the range by using a correction value obtained based on the measurement range of the Doppler shift frequency;

A third function for determining the flow rate of the fluid under measurement using the Doppler shift frequency distribution corrected by the second function;

A program to realize