JP7233647B2 - Measurement position determination method and ultrasonic flowmeter - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Law 1. Publication ・Publication Date: November 29, 2018 96th JSME Fluids Engineering Division Lecture Proceedings 2. Conference presentation (poster) ・Date: November 29-30, 2018 (Announcement date: November 29, 2018) ・Meeting name: The 96th JSME Fluids Engineering Division Lecture ・Venue: Yomogi Rai ▼Tono (1-1 Miyanomori-cho, Muroran-shi, Hokkaido)

The present invention relates to a measurement position determination method and an ultrasonic flowmeter.

2. Description of the Related Art Conventionally, there is known an ultrasonic flowmeter that measures the flow rate of fluid flowing inside a pipeline using an upstream transducer and a downstream transducer (see, for example, Patent Document 1).

In the description below, the transducer may be referred to as a "sensor".

In the ultrasonic flowmeter described in Patent Literature 1, ultrasonic waves transmitted by an upstream sensor are received by a downstream sensor. Also, the ultrasonic waves transmitted by the downstream sensor are received by the upstream sensor.

The control unit calculates the propagation time of ultrasonic waves from the upstream sensor to the downstream sensor (propagation time A) and the propagation time of ultrasonic waves from the downstream sensor to the upstream sensor (propagation time B). Furthermore, the controller calculates the propagation time difference between the propagation time A and the propagation time B, and uses the propagation time difference to calculate the flow velocity and flow rate of the fluid.

JP 2015-222188 A

The ultrasonic flowmeter disclosed in Patent Document 1 measures the flow velocity and flow rate of a target fluid by varying the mounting positions of the upstream sensor and the downstream sensor with respect to the flow direction of the fluid. Therefore, in the ultrasonic flowmeter disclosed in Patent Document 1, the measurement result is affected depending on the mounting position of the sensor.

However, a method for setting the mounting position of the sensor has not been studied so far, and a method for easily determining an appropriate setting position for the sensor has been desired.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a measurement position determination method that enables easy determination of a position where a sensor should be attached and measurement should be performed. It is another object of the present invention to provide an ultrasonic flowmeter that enables easy determination of the mounting position of the sensor and high-precision measurement.

In order to solve the above problems, one aspect of the present invention is a measurement position determination method for determining a measurement position of a fluid flowing inside a pipe, wherein from a first position outside the pipe in a thickness direction of the pipe and receiving the first ultrasonic wave multiple times at a second position outside the pipe and downstream of the pipe from the first position. , for the first received signal obtained based on the first ultrasonic waves received a plurality of times, the reception time of the first received signal and the standard deviation of the intensity of the first received signal for each reception time, or from the standard deviation A step of calculating a first time waveform indicating the relationship with the obtained standard deviation equivalent value; and transmitting a second ultrasonic wave a plurality of times in the thickness direction of the pipe from the second position toward the first position. a step of receiving the second ultrasonic wave multiple times at the first position; and a second received signal obtained based on the second ultrasonic wave received multiple times, the reception time of the second received signal. and calculating a second time waveform indicating the relationship between the standard deviation of the intensity of the second received signal for each reception time or the standard deviation equivalent value obtained from the standard deviation; and determining whether the second position is a position suitable as a reception position of the first ultrasonic wave with respect to the first position, based on a two-time waveform. do.

In one aspect of the present invention, in the determining step, in the first time waveform, the intensity at the determination time in the reception period of the noise wave prior to the main signal and the intensity at the determination time in the second time waveform. The suitable position may be determined when the difference between the positions is smaller than a predetermined first threshold value.

In one aspect of the present invention, in the determining step, when a value of a cross-correlation function between the first time waveform and the second time waveform is greater than a predetermined second threshold, It is good also as a method of judging as.

In one aspect of the present invention, in the determining step, the absolute value of the intensity difference between the first temporal waveform and the second temporal waveform or an equivalent value obtained from the absolute value is a noise wave preceding the main signal. The suitable position may be determined when the integrated value integrated during the reception period is smaller than a predetermined third threshold.

In one aspect of the present invention, the determining step includes a first S/N ratio, which is a ratio of the intensity of the main signal to the intensity of the noise wave in the first time waveform, and the intensity of the noise wave in the second time waveform. The suitable position may be determined when the second S/N ratio, which is the ratio of the intensity of the main signal to the position, is greater than a predetermined fourth threshold value.

Further, one aspect of the present invention is an ultrasonic flowmeter that measures the flow rate of a fluid flowing in a pipe, and includes a first transmission unit that transmits a first ultrasonic wave and a first reception unit that receives ultrasonic vibrations. A second ultrasonic transducer having a first ultrasonic transducer, a second transmitting unit that transmits a second ultrasonic wave, and a second receiving unit that receives ultrasonic vibrations, and the first ultrasonic transducer , a determination unit that determines whether a position relative to the second ultrasonic transducer is a position suitable as a position for measuring the flow rate, and the determination unit sends the first transmission unit to the first transmission unit a plurality of times. a first instruction unit that transmits ultrasonic waves; a first received signal acquisition unit that acquires a plurality of first reception signals output by the second reception unit that has received the first ultrasonic waves; Based on the received signal, for each reception time of the first ultrasonic wave, the standard deviation of the reception time of the first reception signal and the intensity of the first reception signal for each reception time, or the standard deviation obtained from the standard deviation A first temporal waveform calculating unit that calculates a first temporal waveform indicating a relationship with an equivalent value, a second instruction unit that causes the second transmitting unit to transmit the second ultrasonic wave a plurality of times, and the second ultrasonic wave A second received signal acquiring unit that acquires a plurality of second received signals output by the received first receiving unit, and based on the plurality of second received signals, for each reception time of the second ultrasonic wave, A second time for calculating a second time waveform representing a relationship between a reception time of the second received signal and a standard deviation of the intensity of the second received signal for each reception time or a standard deviation equivalent value obtained from the standard deviation. An ultrasonic flowmeter, comprising: a waveform calculator; and a position determiner that determines the suitable position based on the first temporal waveform and the second temporal waveform.

ADVANTAGE OF THE INVENTION According to this invention, the measurement position determination method which can determine easily the position which should attach a sensor and perform a measurement can be provided. In addition, it is possible to provide an ultrasonic flowmeter that enables easy determination of the mounting position of the sensor and high-precision measurement.

FIG. 1 is a diagram showing an ultrasonic flowmeter 1 according to an embodiment. FIG. 2 is a schematic diagram showing how the fluid F flows through the inside A2 of the pipe A. As shown in FIG. FIG. 3 is an explanatory diagram showing how ultrasonic vibrations are transmitted in the pipe A. As shown in FIG. FIG. 4 is an explanatory diagram showing how ultrasonic vibrations are transmitted in the pipe A. As shown in FIG. FIG. 5 is a schematic diagram showing the control device 13. As shown in FIG. FIG. 6 shows time waveforms of the first received signal and the second received signal when the sensor attachment position is not suitable for measuring the flow rate. FIG. 7 shows a first time waveform calculated based on the time waveform of the first received signal in FIG. 6 and a second time waveform calculated based on the time waveform of the second received signal. FIG. 8 is an enlarged view of the reception time range including the main signal for each time waveform shown in FIGS. FIG. 9 shows time waveforms of the first received signal and the second received signal when the sensor attachment position is suitable for measuring the flow rate. FIG. 10 shows a first time waveform calculated based on the time waveform of the first received signal in FIG. 9 and a second time waveform calculated based on the time waveform of the second received signal. FIG. 11 is an enlarged view of the reception time range including the main signal for each time waveform shown in FIGS. FIG. 12 is a flow chart showing the operation of attaching the ultrasonic flowmeter 1 to the pipe A. As shown in FIG. FIG. 13 is a flowchart showing details of steps S11 and S12.

A measurement position determination method and an ultrasonic flowmeter according to the present embodiment will be described below with reference to FIGS. 1 to 13. FIG. In addition, in all the drawings below, the dimensions and ratios of the constituent elements are appropriately changed in order to make the drawings easier to see.

The ultrasonic flowmeter according to this embodiment is, for example, a device capable of measuring the flow rate of fluid flowing through a pipe arranged between a steam production device such as a boiler and a load facility. The fluid includes steam. Steam or steam heat is utilized in the load facility. Further, the ultrasonic flowmeter of the present embodiment is a device that uses ultrasonic waves to measure a gaseous fluid flowing in a pipe.

The fluid flowing through the pipe may be a single-phase flow, a two-phase flow, or a multi-phase flow, which will be described later.

FIG. 1 is a diagram showing an ultrasonic flowmeter 1 of this embodiment. As shown in FIG. 1 , the ultrasonic flowmeter 1 has a first ultrasonic transducer 11 , a second ultrasonic transducer 12 and a control device 13 . The first ultrasonic transducer 11 and the second ultrasonic transducer 12 are provided outside the pipe A extending in the horizontal direction.

In the following description, an xyz orthogonal coordinate system is set, and the positional relationship of each member will be described with reference to this xyz orthogonal coordinate system. Here, the predetermined direction in the horizontal plane is the x-axis direction, the direction perpendicular to the x-axis direction in the horizontal plane is the y-axis direction, and the direction perpendicular to each of the x-axis direction and the y-axis direction (that is, the vertical direction) is the z-axis direction. and

In the following description, the first ultrasonic transducer may be referred to as "first ultrasonic sensor". Also, the second ultrasonic transducer may be referred to as a "second ultrasonic sensor".

The first ultrasonic sensor 11 includes a first transmitter 11A that transmits the first ultrasonic wave P1 and a first receiver 11B that receives the ultrasonic wave.

In the following description, the mounting position of the first ultrasonic sensor 11 may be referred to as "first position".

The second ultrasonic sensor 12 includes a second transmitter 12A that transmits the second ultrasonic wave P2 and a second receiver 12B that receives the ultrasonic wave. The second ultrasonic sensor 12 is provided downstream of the first ultrasonic sensor 11 in the flow direction of the steam (fluid F) flowing through the pipe A. In the figure, the direction of flow of the fluid F is indicated by white arrows.

In the following description, the mounting position of the second ultrasonic sensor 12 may be referred to as "second position".

As shown in FIG. 1, the first ultrasonic sensor 11 and the second ultrasonic sensor 12 are installed in contact with the outer surface A1 of the pipe A (clamp-on method). Also, the first ultrasonic sensor 11 and the second ultrasonic sensor 12 are ideally arranged on the same xy plane, that is, at the same height position in the z direction.

The second receiver 12B receives ultrasonic waves including the first ultrasonic wave P1 transmitted by the first transmitter 11A, converts them into received signals (voltage signals), and outputs them.
The first receiving unit 11B receives ultrasonic waves including the second ultrasonic wave P2 transmitted by the second transmitting unit 12A, converts them into received signals (voltage signals), and outputs them.

The control device 13 determines whether the relative position between the first ultrasonic sensor 11 and the second ultrasonic sensor 12 is a position suitable for measuring the flow rate of the fluid F flowing in the pipe A. and

Further, the control device 13 uses the first ultrasonic sensor 11 and the second ultrasonic sensor 12, and the propagation time of the first ultrasonic wave P1 transmitted from the first ultrasonic sensor 11 to the second ultrasonic sensor 12 is and the propagation time of the second ultrasonic wave P2 transmitted from the second ultrasonic sensor 12 toward the first ultrasonic sensor 11, the flow velocity and flow rate of the fluid F flowing in the inside A2 of the pipe A are calculated. do.

Specifically, the control device 13 controls the propagation time of the first ultrasonic wave P1 transmitted from the first ultrasonic sensor 11 to the second ultrasonic sensor 12 and the transmission time from the second ultrasonic sensor 12 to the first ultrasonic sensor 11. A propagation time difference from the propagation time of the second ultrasonic wave P2 to be transmitted is calculated. Further, the control device 13 calculates the flow velocity and flow rate of the fluid F using the obtained propagation time difference.
The control device 13 will be detailed later.

FIG. 2 is a schematic diagram showing how the fluid F flows in the inside A2 of the pipe A, and is a cross-sectional view taken along the line II-II shown in FIG.

The pipe A shown in FIG. 2 has an annular cross-sectional shape when viewed in the central axis direction of the pipe A. As shown in FIG. Further, the pipe A is covered with a damping material B on the outer surface A1. A known damping material B can be used.

When the fluid F flowing in the inside A2 of the pipe A contains less than a saturated amount of water vapor, only gas, for example, so-called "dry steam", flows inside the pipe A. In this specification, such a flow state is called "single-phase flow".

On the other hand, when the steam (fluid F) generated in a boiler, for example, flows inside the pipe A and the temperature of the fluid F drops, the water vapor contained in the fluid F becomes saturated, and the gas G saturated with water vapor in the pipe. (gas phase) and the resulting liquid W (liquid phase). The liquid W flows in the flow direction of the fluid F together with the flow of the gas G. Such a flow state is called "two-phase flow" or "multi-phase flow".

At this time, in the inside A2 of the pipe A, the liquid W flows in a flowing state as shown in each figure of FIG.

FIG. 2(a) shows a "laminar flow" among two-phase flows. The "laminar flow" is a flow in which no ripples can be confirmed at the interface of the liquid L existing in the lower part of the inside A2 of the pipe A, and the gas G and the liquid L are separated.

FIG. 2(b) shows a "wavy flow" among two-phase flows. The "wavy flow" is a flow in which ripples can be confirmed on the liquid surface L1 of the liquid L existing in the lower part of the inside A2 of the pipe A, and the gas G and the liquid L are separated.

FIG. 2(d) shows an "annular spray flow" of the multiphase flow. In the "annular spray flow", a liquid film can be confirmed up to the upper part of the inside A2 of the pipe A, a film of the liquid L exists on the inner wall A3 of the pipe A, and a large number of droplets of the gas G are present at the center of the pipe cross section. It is the flow entrained by L2.

FIG. 2(c) shows a “wavy annular transition” in a two-phase flow. "Wavy Annular Transition" is the transition state flow between "Wave Flow" and "Annular Spray Flow".

3 and 4 are explanatory diagrams showing how ultrasonic vibrations are transmitted in the pipe A, and are cross-sectional views taken along the line II-II shown in FIG. 3 and 4 show that the fluid F in the inside A2 of the pipe A is a laminar flow.

In the ultrasonic flowmeter 1 of this embodiment, the first ultrasonic wave P1 transmitted from the first transmitter 11A of the first ultrasonic sensor 11 installed on the outer surface A1 of the pipe A propagates inside A2 of the pipe A. The second receiver 12B of the second ultrasonic sensor 12 receives the first ultrasonic wave P1 that has propagated through the inside A2 of the pipe A, converts it into a received signal, and outputs the received signal.

On the other hand, in the ultrasonic flowmeter 1, ultrasonic waves applied in the thickness direction of the pipe wall of the pipe A vibrate the pipe wall in the thickness direction. The generated vibration propagates through the pipe A as a noise wave N and is received by the second ultrasonic sensor 12 . The second receiver 12B also receives the noise wave N, converts it into a received signal, and outputs it.

That is, the received signal output by the second receiving unit 12B includes both the signal derived from the first ultrasonic wave P1 propagated through the inside A2 of the pipe A and the signal derived from the noise wave N propagated through the pipe A. include. At this time, the noise wave N propagating through the pipe A, which is solid, reaches the second receiving section 12B earlier than the first ultrasonic wave P1 propagating through the fluid F, which is gas or liquid.

Also, when the second ultrasonic wave P2 transmitted from the second ultrasonic sensor 12 is received by the first ultrasonic sensor 11, the received signal output by the first receiving unit 11B includes the signal propagated through the inside A2 of the pipe A. It includes both a signal originating from the ultrasonic wave that propagated through the pipe A and a signal originating from the noise wave N propagating through the pipe A. At this time, the noise wave N propagating through the pipe A, which is solid, reaches the first receiver 11B earlier than the second ultrasonic wave P2 propagating through the fluid F, which is gas or liquid.

In this specification, the signal derived from the ultrasonic wave P propagated through the inside A2 of the pipe A is referred to as the "main signal". A signal derived from a noise wave is referred to as a "noise signal". The ultrasonic flowmeter 1 measures the flow rate of the fluid F using this signal.

Here, assuming a virtual plane S that includes the center C of the pipe A and extends in the xy directions, the liquid L accumulates on the lower side β of the virtual plane S than on the upper side α of the virtual plane S.

As shown in FIG. 3, when the first ultrasonic wave P1 is transmitted from the first transmission unit 11A of the first ultrasonic sensor 11, the noise wave N1 propagating upward α as the noise wave N propagating in the pipe A, A noise wave N2 is generated which propagates on the lower side β.

At this time, part of the noise wave N2 is transmitted through the liquid L that accumulates downward in the direction of gravity (-z direction) in the inside A2 of the pipe A, and is reflected by the gas-liquid interface (liquid surface L1) to re-pipe. come back to A. Since the liquid L flows through the inside A2 of the pipe A, the liquid surface L1 moves, and part of the noise wave N2 passing through the liquid L undergoes temporal fluctuations. Due to such propagation, the noise wave N contains temporal fluctuations in the case of two-phase or multi-phase flow compared to the case of single-phase flow.

In FIG. 3, the first ultrasonic sensor 11 and the second ultrasonic sensor 12 are arranged on the virtual plane S. As shown in FIG. In other words, the first ultrasonic sensor 11 and the second ultrasonic sensor 12 are positioned symmetrically with respect to the center of the pipe A and are installed at the same height.

In this case, a noise wave N2 generated when ultrasonic waves are transmitted from the first ultrasonic sensor 11 to the second ultrasonic sensor 12 and a noise wave N2 generated when ultrasonic waves are transmitted from the second ultrasonic sensor 12 to the first ultrasonic sensor 11 There is no difference from the noise wave N2 generated at . Therefore, although the influence of noise increases compared to the case of single-phase flow, signal analysis and measurement of the flow rate and flow velocity of the target fluid F are possible.

On the other hand, as shown in FIG. 4, when the first ultrasonic sensor 11 and the second ultrasonic sensor 12 are not arranged on the virtual plane S, the ultrasonic wave from the first ultrasonic sensor 11 to the second ultrasonic sensor 12 is detected. There is a difference between the noise wave N2 (noise wave N21) generated when transmitting the sound wave and the noise wave N2 (noise wave N22) generated when transmitting the ultrasonic wave from the second ultrasonic sensor 12 to the first ultrasonic sensor 11. occurs. This is because the relationship between the sensor position and the thickness of the liquid film of the liquid L differs between the first ultrasonic sensor 11 and the second ultrasonic sensor 12 . Therefore, in the arrangement as shown in FIG. 4, the noise wave N21 and the noise wave N22 are subject to different temporal fluctuations from the liquid L, respectively.

As a result, for example, there is a difference in intensity between the noise wave N21 and the noise wave N22, and the main signal with little noise and the main signal with much noise are output from the receiver. Therefore, in the signal state obtained in the sensor arrangement as shown in FIG. 4, signal analysis and target measurement of the flow rate and flow velocity of the fluid F tend to become difficult.

Furthermore, in addition to the example shown in FIG. 4, when the first ultrasonic sensor 11 and the second ultrasonic sensor 12 are not located point-symmetrically with respect to the center C of the pipe A, The distance between the first ultrasonic sensor 11 and the second ultrasonic sensor 12 differs between the upper side α of the pipe A and the lower side β. In this case, the noise wave N1 propagating on the upper side α and the noise wave N2 propagating on the lower side β have different propagation distances, and thus have different reception times and vibration damping amounts.

As a result, for example, there is a difference in intensity between the noise wave N1 and the noise wave N2, and the main signal with little noise and the main signal with much noise are output from the receiver. Therefore, even if the first ultrasonic sensor 11 and the second ultrasonic sensor 12 are not positioned symmetrically with respect to the center C of the pipe A, signal analysis and flow rate measurement tend to be difficult.

In order to solve such a problem, in the ultrasonic flowmeter 1 of the present embodiment, the control device 13 has the configuration described below, and by performing appropriate processing, the first ultrasonic sensor 11 and the second ultrasonic sensor 11 can be easily detected. The ultrasonic sensor 12 can be installed at an appropriate position (for example, the ideal arrangement shown in FIG. 3).

FIG. 5 is a schematic diagram showing the control device 13. As shown in FIG. FIG. 5 shows part of the configuration of the control device 13. As shown in FIG. The control device 13 determines the attachment positions of the first ultrasonic sensor 11 and the second ultrasonic sensor 12 based on the received signal output by the second receiver 12B, the received signal output by the first receiver 11B, and the like. Determine whether it is appropriate.

The control device 13 shown in FIG. 5 includes a first instruction unit 13A, a second instruction unit 13B, a first reception signal acquisition unit 13C, a second reception signal acquisition unit 13D, a first temporal waveform calculation unit 13E, It has a second temporal waveform calculation unit 13F, a position determination unit 13G, a storage unit 13H, an input unit 13X, an input reception unit 13Y, and an output unit 13Z. a first instruction unit 13A, a second instruction unit 13B, a first reception signal acquisition unit 13C, a second reception signal acquisition unit 13D, a first temporal waveform calculation unit 13E, a second temporal waveform calculation unit 13F, The position determination section 13G constitutes the "determination section" in the present invention.

The first instruction unit 13A issues an instruction to transmit an ultrasonic wave (first ultrasonic wave P1) to the first transmission unit 11A, and causes the first transmission unit 11A to transmit the ultrasonic wave multiple times.

The second instruction unit 13B issues an instruction to transmit an ultrasonic wave (second ultrasonic wave P2) to the second transmission unit 12A, and causes the second transmission unit 12A to transmit the ultrasonic wave multiple times.

The number of transmissions of ultrasonic waves by the first transmission unit 11A and the number of transmissions of ultrasonic waves by the second transmission unit 12A may be the same or different. From the first transmitter 11A and the second transmitter 12A, ultrasonic waves are transmitted a sufficient number of times, for example, 2000 times or more, respectively, to implement the invention of the present embodiment.

The first reception signal acquisition unit 13C acquires the first reception signal output by the second reception unit 12B.

The first received signal includes a signal converted by the second receiving unit 12B receiving the first ultrasonic wave and a signal (noise signal) converted by the second receiving unit 12B receiving the noise wave.

In the second receiving unit 12B, for each ultrasonic wave transmission by the first transmitting unit 11A, the arrival time (the 2 continuously receive ultrasonic waves (the first ultrasonic wave P1 and the noise wave) with different reception times in the receiving unit 12B. The first received signal acquisition unit 13C discretely receives a plurality of first received signals based on the ultrasonic waves received by the second receiving unit 12B.

The time waveform of the first received signal, which is the correspondence relationship of the signal voltage with respect to the reception time of the ultrasonic wave (the first ultrasonic wave P1 and the noise wave), is obtained from the ultrasonic wave reception time and the continuously received first received signal. can ask. The reception interval of the first received signal is preferably an interval that allows the time waveform of the first received signal to be drawn. For example, the first received signal is received every 500 μs (2 kHz).

The time waveform of the first received signal is obtained for each ultrasonic wave transmission by the first transmitter 11A. That is, if the number of transmissions of ultrasonic waves by the first transmitter 11A is 2000 or more, 2000 or more temporal waveforms are obtained.

The second received signal acquiring section 13D acquires the second received signal output by the first receiving section 11B.

The second received signal includes a signal converted by the second receiving unit 12B receiving the first ultrasonic wave and a signal (noise signal) converted by the second receiving unit 12B receiving the noise wave.

In the first receiving unit 11B, for each ultrasonic transmission by the second transmitting unit 12A, the arrival time (second The ultrasonic waves (the second ultrasonic wave P2 and the noise wave) with different reception times in the 1 receiving unit 11B are continuously received. The second reception signal acquisition unit 13D discretely receives a plurality of second reception signals based on the ultrasonic waves received by the first reception unit 11B.

From the reception time of the ultrasonic wave and the continuously received second received signal, the time waveform of the second received signal, which is the correspondence relationship of the signal voltage with respect to the reception time of the ultrasonic wave (the second ultrasonic wave P2 and the noise wave), is obtained. can ask. The reception interval of the second received signal is preferably an interval that allows the time waveform of the second received signal to be drawn. For example, the second reception signal is received every 500 μs (2 kHz).

The time waveform of the second received signal is obtained for each ultrasonic wave transmission by the second transmitter 12A. That is, if the number of transmissions of ultrasonic waves by the second transmitter 12A is 2000 or more, 2000 or more temporal waveforms are obtained.

The first temporal waveform calculator 13E acquires the strength of the first received signal output by the second receiver 12B at a time after a predetermined time has elapsed from the transmission time when the first transmitter 11A transmitted the ultrasonic waves. Similarly, in each of the plurality of ultrasonic wave transmissions transmitted by the first transmission unit 11A, the first temporal waveform calculation unit 13E calculates the , to obtain the strength of the first received signal. The first temporal waveform calculator 13E of the present embodiment calculates the standard deviation (first standard deviation) of the intensities of the plurality of first received signals thus acquired.

Also, the first temporal waveform calculator 13E calculates the above-described first standard deviation at a plurality of times.

Thereby, the time waveform of the first standard deviation, which is the correspondence relationship of the first standard deviation of the signal voltage with respect to the reception time of the ultrasonic waves (the first ultrasonic wave P1 and the noise wave), can be obtained. Hereinafter, the time waveform of the first standard deviation may be referred to as "first time waveform".

The second temporal waveform calculator 13F acquires the intensity of the second received signal output by the first receiver 11B at a time after a predetermined time has elapsed from the transmission time when the second transmitter 12A transmitted the ultrasonic waves. Similarly, in each of the plurality of ultrasonic wave transmissions transmitted by the second transmission unit 12A, the second temporal waveform calculation unit 13F calculates the , to obtain the strength of the second received signal. The second temporal waveform calculator 13F of the present embodiment calculates the standard deviation (second standard deviation) of the intensities of the plurality of second received signals thus acquired.

Also, the second temporal waveform calculator 13F calculates the above-described second standard deviation at a plurality of times.

Thereby, the time waveform of the second standard deviation, which is the correspondence relationship of the second standard deviation of the signal voltage with respect to the reception time of the ultrasonic waves (the second ultrasonic wave P2 and the noise wave), can be obtained. Hereinafter, the time waveform of the second standard deviation may be referred to as "second time waveform".

Based on the first time waveform and the second time waveform, the position determination unit 13G determines that the second position is a position suitable for receiving the first ultrasonic wave with respect to the first position. The position determination unit 13G performs the above determination based on the waveforms of the noise waves in the first time waveform and the second time waveform. Description will be made below with reference to FIGS. 6 to 11. FIG.

6 to 11 show the time waveform of the first received signal, the time waveform of the second received signal, the first time waveform and the second time waveform.

FIG. 6 shows the time waveform of the first received signal and the time waveform of the second received signal when the sensor mounting position is not a position suitable for measuring the flow rate. is an average waveform of a plurality of time waveforms corresponding to . The horizontal axis indicates the ultrasonic wave reception time (unit: microseconds) in the first receiver 11B or the second receiver 12B. The vertical axis indicates the strength (unit: V) of the first received signal and the second received signal.

FIG. 7 shows a first time waveform calculated based on the time waveform of the first received signal in FIG. 6 and a second time waveform calculated based on the time waveform of the second received signal. The horizontal axis indicates the ultrasonic wave reception time (unit: microseconds) in the first receiver 11B or the second receiver 12B. The vertical axis indicates the intensity (unit: V) of the first standard deviation and the second standard deviation.

FIG. 8 is an enlarged view of the reception time range including the main signal for each time waveform shown in FIGS. The horizontal axis indicates the ultrasonic wave reception time (unit: microseconds) in the first receiver 11B or the second receiver 12B. The vertical axis on the left side indicates the strength (unit: V) of the first received signal and the second received signal. The vertical axis on the right side indicates the intensity (unit: V) of the first standard deviation and the second standard deviation.

In FIG. 8, the amplitude waveform centered on 0 V on the vertical axis on the left side indicates the time waveform of the first received signal and the time waveform of the second received signal. Also, in FIG. 8, waveforms having a baseline at a position of less than 0.05 V on the vertical axis on the right side represent the first time waveform and the second time waveform.

FIG. 9 shows the time waveform of the first received signal and the time waveform of the second received signal when the sensor mounting position is suitable for measuring the flow rate, and shows the average waveform corresponding to FIG. The vertical axis and horizontal axis are the same as in FIG.

10 shows a first time waveform calculated based on the time waveform of the first received signal in FIG. 9 and a second time waveform calculated based on the time waveform of the second received signal, corresponding to FIG. It is a diagram. The vertical axis and horizontal axis are the same as in FIG.

FIG. 11 is an enlarged view of the reception time range including the main signal for each time waveform shown in FIGS. 9 and 10, and is a view corresponding to FIG. The vertical axis and horizontal axis are the same as in FIG.

7, 8, 10, and 11, X indicates the time waveform of the standard deviation of the received signal when the first ultrasonic wave transmitted by the first transmitter is received by the second receiver, and Y is the second transmitter. 2 shows the time waveform of the standard deviation of the received signal when the first receiving unit receives the second ultrasonic wave transmitted by .

First, when the time waveform of the received signal and the time waveform of the standard deviation are compared, the sensor mounting position is not suitable for flow measurement (Figs. 6 and 7), and the sensor mounting position is not suitable for flow measurement. In both cases (FIGS. 9 and 10), the time waveform of the standard deviation makes it easier to recognize the main signal (the peak near 200 μs). Therefore, by creating a time waveform of the standard deviation, this signal becomes clear, and it can be seen that the flow rate can be easily measured after the ultrasonic flowmeter 1 is installed.

(Judgment Criteria 1)
Next, comparing FIGS. 7 and 10, in FIG. 7, when comparing the first time waveform and the second time waveform, the reception period of the noise wave, which is the period before the main signal (for example, the period from 50 μs to 150 μs) ), there is a clear difference between the intensity of the first standard deviation and the intensity of the second standard deviation at the decision time (for example, the time of 100 μs). In FIG. 7, the difference between the intensity of the first standard deviation and the intensity of the second standard deviation at the determination time is indicated by symbol Ta (intensity difference Ta).

On the other hand, in FIG. 10, when comparing the first time waveform and the second time waveform, the intensity of the first standard deviation and the second standard deviation are There is no difference in the intensity of

Therefore, by setting a first threshold value T1 for the intensity difference in the determination time between the first time waveform and the second time waveform, the intensity difference Ta between the first standard deviation and the second standard deviation becomes the first If it is smaller than the threshold T1 (Ta<T1), it can be determined that the sensor mounting position is suitable for flow rate measurement.

Such a determination may be made, for example, at the time when the noise waves of the first time waveform and the second time waveform show the maximum value.

Alternatively, as shown in FIG. 7, the judgment time may be set in advance and the judgment may be made at the judgment time. The ultrasonic waves transmitted from the transmission unit reach the reception unit depending on conditions such as the diameter, thickness, material, type of fluid to be measured, flow velocity, etc. of the pipe A to which the ultrasonic flowmeter 1 is attached. (Receiving time at the receiving unit is different. Therefore, when determining the judgment time in advance, it is preferable to conduct a preliminary experiment and determine an appropriate time as the judgment time.

(Judgment Criteria 2)
Also, in the entire time range in FIGS. 7 and 10, the first standard deviation and the second standard deviation are used to calculate the value of the cross-correlation function between the first time waveform and the second time waveform using a known method. Thus, the degree of matching between the first time waveform and the second time waveform may be evaluated. By setting a threshold (second threshold) in advance for the value (maximum value: 1) obtained from the cross-correlation function, it is determined whether or not the shapes of the first time waveform and the second time waveform match. can do.

(Judgment Criteria 3)
Also, by evaluating the difference between the first standard deviation and the second standard deviation at a plurality of times in FIGS. can.

For the "difference between the values of the first standard deviation and the second standard deviation", for example, the absolute value of the difference between the first standard deviation and the second standard deviation, or the equivalent value obtained from the absolute value, is obtained. An integrated value obtained by integrating the absolute value obtained during the reception period of the noise wave preceding the main signal can be used. Using these values as determination criteria, when the determination criteria are smaller than a predetermined threshold value (third threshold value), it can be determined that the sensor mounting position is suitable for flow rate measurement.

Here, the "equivalent value obtained from the absolute value" is the absolute value of the difference between the first standard deviation and the second standard deviation, the value obtained by multiplying a predetermined coefficient, obtained by powering the absolute value values can be mentioned.

(Other criteria)
In FIG. 8, the maximum value of the intensity of the main signal in the first time waveform and the main signal in the second time waveform indicates Tx.
On the other hand, in FIG. 11, the main signal in the first time waveform and the main signal in the second time waveform each have a maximum intensity value of Tb.

When the mounting position of the sensor is suitable for measurement, the strength of the main signal tends to be strong. Conversely, when the mounting position of the sensor is not suitable for measurement, the strength of the main signal tends to be weak. Prone. Therefore, for example, by comparing a threshold value (T2=0.05V) determined in advance as the intensity of the main signal with the intensity of the main signal, it is possible to determine whether the mounting position of the sensor is good or bad.

In this case, as shown in FIG. 8, when the intensity Tx of the main signal is smaller than the threshold value T2 (Tx<T2), the sensors of the first ultrasonic sensor 11 and the second ultrasonic sensor 12 as shown in FIGS. It can be determined that the mounting position is not a suitable position for flow measurement.

Further, when the intensity Tb of the main signal is larger than the threshold value T2 as shown in FIG. 11 (Tb>T2), the sensor mounting positions of the first ultrasonic sensor 11 and the second ultrasonic sensor 12 as shown in FIGS. can be determined to be a suitable position for flow measurement.

Furthermore, a first S/N ratio that is the ratio of the intensity of the main signal to the intensity of the noise wave in the first time waveform, and a second S/N ratio that is the ratio of the intensity of the main signal to the intensity of the noise wave in the second time waveform The N ratio can also be used as a criterion. The S/N ratio can be, for example, the ratio of the maximum intensity of the main signal to the maximum intensity of the noise wave.

When the first S/N ratio and the second S/N ratio are larger than a predetermined threshold value (fourth threshold value) T4 for the S/N ratio, it is determined that the sensor mounting position is suitable for flow rate measurement. be able to.

Furthermore, at a plurality of times during the reception period of the noise wave (for example, a period of 50 μs to 150 μs), the intensity difference between the first time waveform and the second time waveform is obtained, and the integrated value of the intensity difference at the plurality of times obtained. can be used as a criterion. A threshold value is set in advance for such determination criteria, and when the obtained integrated value is smaller than the threshold value, it can be determined that the sensor attachment position is suitable for flow rate measurement.

Each criterion described above can be used in combination with each other.

As for each threshold, it is preferable to conduct a preliminary experiment in advance and set a threshold at which the intensity of the main signal that enables measurement of the flow rate can be obtained. It is preferable that the number of transmissions of ultrasonic waves transmitted from each transmission unit when obtaining each threshold is the same as the number of transmissions of ultrasonic waves transmitted from each transmission unit when determining the mounting position of the ultrasonic sensor. .

The input unit 13X inputs an instruction to the control device 13 to execute a “determination mode” for positioning the first ultrasonic sensor 11 and the second ultrasonic sensor 12 .

The input reception unit 13Y receives instructions input from the input unit 13X, and instructs the first instruction unit 13A, the second instruction unit 13B, and the position determination unit 13G to perform predetermined processing.

The output unit 13Z outputs the determination result of the position determination unit 13G. The output unit 13Z, for example, has a configuration that performs visual output such as a display unit that displays the determination result, a light emitting unit that lights or blinks according to the determination result, and an auditory output such as a beep sound according to the determination result. and a configuration for outputting

FIG. 12 is a flow chart showing the operation of attaching the ultrasonic flowmeter 1 to the pipe A. As shown in FIG. In the following description, the symbols shown in FIGS. 1 to 3 are used as appropriate.

First, the operator attaches the first ultrasonic sensor 11 and the second ultrasonic sensor 12 that constitute the ultrasonic flowmeter 1 to the pipe A (step S10). At that time, for example, the first ultrasonic sensor 11 is on the upstream side of the pipe A, and the second ultrasonic sensor 12 is on the downstream side of the first ultrasonic sensor 11 in the pipe A. The sonic sensor 11 and the second ultrasonic sensor 12 are attached.

Next, the operator turns on the power of the control device 13 and inputs an instruction to the control device 13 to execute a "determination mode" for positioning the first ultrasonic sensor 11 and the second ultrasonic sensor 12. do.

Next, the first received signal is acquired (step S11). FIG. 13 is a flowchart showing details of step S11.

First, the first transmitter 11A of the first ultrasonic sensor 11 transmits the first ultrasonic wave from the first position (step S11A, step of transmitting the first ultrasonic wave multiple times).

Next, the second receiver 12B of the second ultrasonic sensor 12 receives the ultrasonic waves (first ultrasonic wave and noise wave) transmitted from the first transmitter 11A at the second position (step S11B, first ultrasonic wave). receiving the sound wave multiple times).

Next, the second receiver 12B converts the received ultrasonic wave into a first received signal and outputs the first received signal (step S11C).

Next, the first received signal acquiring unit 13C acquires the first received signal output from the second receiving unit 12B (step S11D).

Next, the control unit 14 determines whether or not the number of transmissions of ultrasonic waves by the first transmission unit 11A has reached a preset number (for example, 2000 times) (step S11E).

When the number of transmissions of ultrasonic waves by the first transmission unit 11A reaches the preset number of times, step S11 is ended. On the other hand, if the number of transmissions of ultrasonic waves by the first transmission unit 11A has not reached the preset number of times, the process returns to step S11A.

Next, a second received signal is obtained (step S12). The second received signal can be acquired in the same flow as the acquisition flow of the first received signal described above. FIG. 13 is a flowchart showing details of step S12.

First, the second transmitter 12A of the second ultrasonic sensor 12 transmits the second ultrasonic wave from the second position (step S12A, step of transmitting the second ultrasonic wave multiple times).

Next, the first receiver 11B of the first ultrasonic sensor 11 receives the ultrasonic waves (second ultrasonic waves and noise waves) transmitted from the second transmitter 12A at the first position (step S12B, second ultrasonic wave). receiving the sound wave multiple times).

Next, the first receiver 11B converts the received ultrasonic wave into a second received signal and outputs the second received signal (step S12C).

Next, the second received signal acquiring section 13D acquires the second received signal output from the first receiving section 11B (step S12D).

Next, the control unit 14 determines whether or not the number of transmissions of ultrasonic waves by the second transmission unit 12A has reached a preset number (for example, 2000 times) (step S12E).

When the number of transmissions of ultrasonic waves by the second transmission unit 12A reaches the preset number of times, step S12 ends. On the other hand, if the number of transmissions of ultrasonic waves by the second transmission unit 12A has not reached the preset number of times, the process returns to step S12A.

Next, the first temporal waveform calculator 13E calculates the standard deviation (first standard deviation) of the acquired intensities of the plurality of first received signals. Furthermore, the first temporal waveform calculator 13E obtains a first temporal waveform, which is the correspondence relationship of the first standard deviation of the signal voltage with respect to the reception time of the ultrasonic waves (first ultrasonic wave P1 and noise wave) (step S13, step of calculating the first time waveform).

Next, the second temporal waveform calculator 13F calculates the standard deviation (second standard deviation) of the acquired intensities of the plurality of second received signals. Furthermore, the second temporal waveform calculator 13F obtains a second temporal waveform, which is the correspondence relationship of the second standard deviation of the signal voltage with respect to the reception time of the ultrasonic waves (second ultrasonic waves P2 and noise waves) (step S14, step of calculating the second time waveform).

The order of steps S11 to S14 may be reversed if step S13 is performed after step S11 and step S14 is performed after step S12 in chronological order. For example, the processing order of steps S12 and S13 may be interchanged. Also, the processing order of steps S11 and S12 may be exchanged.

Next, based on the first time waveform and the second time waveform, the position determination unit 13G determines the mounting position (second position) is a position suitable as a reception position of the first ultrasonic wave P1. That is, it is determined whether or not the relative positions of the first ultrasonic sensor 11 and the second ultrasonic sensor 12 are suitable for flow rate measurement (step S15, determination step).

For example, when the fluid F flowing in the inside A2 of the pipe A is a single-phase flow, there is no difference in the noise waves N such as the noise waves N21 and N22 shown in FIG. First, it is determined that the sensor mounting position is suitable for flow rate measurement.

Further, when the fluid F is a two-phase flow or a multi-phase flow, the mounting position of the first ultrasonic sensor 11 and the mounting position of the second ultrasonic sensor 12 are different from the center C of the pipe A, as shown in FIG. If the positions are symmetrical about each other and at the same height position, it is determined that the sensor mounting position is suitable for flow rate measurement.

If the position determination unit 13G determines that the sensor mounting position is suitable for flow rate measurement, the mounting operation of the ultrasonic flowmeter 1 is terminated.

Further, when the mounting position of the first ultrasonic sensor 11 and the mounting position of the second ultrasonic sensor 12 are not point-symmetrical positions with respect to the center C of the pipe A, the first ultrasonic sensor 11 and the second ultrasonic sensor If the sensor 12 is not at the same height position, it is determined that the sensor mounting position is not suitable for flow rate measurement. Further, when the fluid F is a two-phase flow or a multiphase flow, and the first ultrasonic sensor 11 and the second ultrasonic sensor 12 are not at the same height position, the sensor mounting position is not suitable for flow measurement. It is determined that the position is not suitable.

When the position determination unit 13G determines that the sensor attachment position is not a position suitable for flow rate measurement, the attachment positions of the first ultrasonic sensor 11 and the second ultrasonic sensor 12 are changed (step S16). . After that, the process is repeated again from step S11.

After attaching the first ultrasonic sensor 11 and the second ultrasonic sensor 12 to the pipe A as described above, the inside A2 of the pipe A is measured using the ultrasonic flowmeter 1 using a known method. The velocity of the flowing fluid F can be measured.

According to the measurement position determination method as described above, it is possible to easily determine the position where the sensor should be attached and the measurement should be performed.

Further, according to the ultrasonic flowmeter as described above, it is possible to easily determine the mounting position of the sensor, and highly accurate measurement becomes possible.

In the present embodiment, the first temporal waveform calculating unit 13E obtains the first standard deviation to calculate the first temporal waveform, and the second temporal waveform calculating unit 13F obtains the second standard deviation to calculate the second Although the time waveform was calculated, it is not limited to this.

In the first temporal waveform calculator 13E and the second temporal waveform calculator 13F, the standard deviation equivalent value obtained from the standard deviation may be used instead of the standard deviation to calculate the temporal waveform.

Here, the "standard deviation equivalent value obtained from the standard deviation" can include the "variance" which is the value obtained by squaring the standard deviation. Values obtained by multiplying the standard deviation or variance by a predetermined coefficient, and values obtained by multiplying the standard deviation or variance can also be mentioned.

The time waveforms of these "standard deviation equivalent values obtained from the standard deviations" have the same amplitude tendency as the above-described standard deviation time waveforms. Therefore, in the first time waveform calculation unit 13E and the second time waveform calculation unit 13F, even if the standard deviation equivalent value is obtained and the time waveform of the standard deviation equivalent value is calculated as the first time waveform and the second time waveform, the sensor It becomes possible to easily determine the position where the measurement should be performed by mounting.

As the standard deviation equivalent value, for example, the first time waveform calculation unit 13E and the second time waveform calculation unit 13F obtain the variance of the received signal instead of the standard deviation, and the obtained variance is used as the first time waveform and the second time waveform. may be calculated.

When the first time waveform calculator 13E uses the standard deviation of the received signal to calculate the time waveform, the second time waveform calculator 13F also uses the standard deviation of the received signal to calculate the time waveform, Determine the sensor mounting position.

When the standard deviation equivalent value is used in the first temporal waveform calculating section 13E and the second temporal waveform calculating section 13F, the same type of value is used as the standard deviation equivalent value.

For example, when the first temporal waveform calculator 13E calculates the temporal waveform using the variance of the received signal, the second temporal waveform calculator 13F also calculates the temporal waveform using the variance of the received signal, Determine the sensor mounting position.

Further, in the present embodiment, the pipe A to which the sensor is attached extends in the horizontal direction, but the present invention is not limited to this. The present invention can be employed, for example, when attaching an ultrasonic sensor to a pipe A extending in the vertical direction. When the pipe A extends in the vertical direction, even if the fluid F in the pipe A is a two-phase flow, there is no difference in the noise waves N such as the noise waves N21 and N22 shown in FIG. Therefore, the noise wave is not disturbed, and the sensor mounting position is determined to be a position suitable for flow rate measurement.

Although the preferred embodiments according to the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such examples. The various shapes, combinations, etc., of the constituent members shown in the above examples are merely examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

In the above embodiment, the fluid F is steam flowing inside the pipe A, but the object to which the present invention is applied is not limited to steam.
For example, even if the fluid F flowing in the pipe A is a multiphase flow such as a water-air two-phase flow, a liquid-liquid two-phase flow, or a solid-liquid two-phase flow, the phase distribution of the fluid F in the pipe As a result, the noise intensity at the time of reception may differ depending on the transmission direction of the ultrasonic waves. The present invention can also be suitably applied when measuring the flow velocity and flow rate of such fluid F.

DESCRIPTION OF SYMBOLS 1... Ultrasonic flowmeter, 11... 1st ultrasonic transducer, 11A... 1st transmitter, 11B... 1st receiver, 12... 2nd ultrasonic transducer, 12A... 2nd transmitter, 12B... 2nd receiver , 13A... First instruction unit, 13B... Second instruction unit, 13C... First reception signal acquisition unit, 13D... Second reception signal acquisition unit, 13E... First time waveform calculation unit, 13F... Second time waveform calculation unit , 13G... Position determination part, A... Piping, A2... Inside, F... Fluid, G... Gas, L... Liquid, L1... Liquid level, N, N1, N2, N21, N22... Noise wave, P... Ultrasonic wave, P1...first ultrasonic wave, P2...second ultrasonic wave, S...virtual surface

Claims (6)

A measurement position determination method for determining a measurement position of a fluid flowing inside a pipe,
transmitting a first ultrasonic wave a plurality of times in a thickness direction of the pipe from a first position outside the pipe;
a step of receiving the first ultrasonic wave a plurality of times at a second position outside the pipe and downstream of the pipe from the first position;
For the first received signal obtained based on the first ultrasonic waves received a plurality of times, the reception time of the first received signal and the standard deviation of the intensity for each reception time of the first received signal or the standard deviation. A step of calculating a first time waveform showing the relationship with the standard deviation equivalent value obtained;
a step of transmitting a second ultrasonic wave a plurality of times in the thickness direction of the pipe from the second position toward the first position;
receiving the second ultrasonic wave multiple times at the first location;
For a second received signal obtained based on the second ultrasonic waves received a plurality of times, the reception time of the second received signal and the standard deviation or the standard deviation of the intensity for each reception time of the second received signal. A step of calculating a second time waveform showing the relationship with the standard deviation equivalent value obtained;
Based on the first time waveform and the second time waveform, determining that the second position is a position suitable as a reception position of the first ultrasonic wave with respect to the first position; A measurement position determination method comprising: In the determining step, in the first time waveform, the difference between the intensity at the determination time in the reception period of the noise wave prior to the main signal and the intensity at the determination time in the second time waveform is a predetermined number. 2. The method of determining a measured position according to claim 1, wherein the suitable position is determined when the position is smaller than one threshold. 3. The suitable position is determined in the determining step when a value of a cross-correlation function between the first time waveform and the second time waveform is greater than a predetermined second threshold. The measurement position determination method described in . In the determining step, the absolute value of the intensity difference between the first temporal waveform and the second temporal waveform or an equivalent value obtained from the absolute value is integrated during the reception period of the noise wave prior to the main signal. 4. The method of determining a measured position according to any one of claims 1 to 3, wherein the suitable position is determined when is smaller than a predetermined third threshold. The determining step includes a first S/N ratio, which is the ratio of the intensity of the main signal to the intensity of the noise wave in the first temporal waveform, and the ratio of the intensity of the main signal to the intensity of the noise wave in the second temporal waveform. 5. The method of determining a measured position according to any one of claims 1 to 4, wherein the suitable position is determined when all of the second S/N ratios are greater than a predetermined fourth threshold value. An ultrasonic flowmeter that measures the flow rate of a fluid flowing in a pipe,
a first ultrasonic transducer having a first transmitter for transmitting a first ultrasonic wave and a first receiver for receiving ultrasonic vibration;
a second ultrasonic transducer having a second transmitter for transmitting a second ultrasonic wave and a second receiver for receiving ultrasonic vibration;
A determination unit that determines that the relative position between the first ultrasonic transducer and the second ultrasonic transducer is a position suitable as a position for measuring the flow rate,
The determination unit includes a first instruction unit that causes the first transmission unit to transmit the first ultrasonic wave a plurality of times;
a first received signal acquiring unit that acquires a plurality of first received signals output by the second receiving unit that has received the first ultrasonic wave;
Based on the plurality of first received signals, for each reception time of the first ultrasonic wave, the standard deviation of the reception time of the first reception signal and the intensity of the first reception signal for each reception time, or the standard deviation A first temporal waveform calculation unit that calculates a first temporal waveform showing the relationship with the standard deviation equivalent value obtained from
a second instruction unit that causes the second transmission unit to transmit the second ultrasonic wave a plurality of times;
a second received signal acquiring unit that acquires a plurality of second received signals output by the first receiving unit that has received the second ultrasonic wave;
Based on the plurality of second received signals, for each reception time of the second ultrasonic wave, the standard deviation of the reception time of the second reception signal and the intensity of the second reception signal for each reception time, or the standard deviation A second time waveform calculation unit that calculates a second time waveform showing the relationship with the standard deviation equivalent value obtained from
An ultrasonic flowmeter, comprising: a position determination unit that determines the suitable position based on the first time waveform and the second time waveform.

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