Flow rate calculation device and ultrasonic flowmeter

Abstract

To provide a flow rate calculation device which makes it possible to reduce the size of an ultrasonic flowmeter compared with the conventional one.SOLUTION: A flow rate calculation device (100) includes: a transmission unit (20) for transmitting ultrasonic waves, by beamforming, from one of a first transducer (2) and a second transducer (3) each having a plurality of ultrasonic elements arranged in an array toward the other of the first transducer (2) and the second transducer (3); and a calculation unit (60) for calculating the flow rate of fluid in a pipe (1), in a state where the first transducer (2) and the second transducer (3) are disposed on opposite sides of the pipe (1), on the basis of the difference between the time until the ultrasonic wave from the first transducer (2) reaches the second transducer (3) through the fluid in the pipe (1) and the time until the ultrasonic wave from the second transducer (3) reaches the first transducer (2) through the fluid in the pipe (1).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a flow rate calculation device and an ultrasonic flow meter. [Background technology]

[0002] A clamp-on ultrasonic flow sensor that measures the flow rate of a fluid flowing through a pipe has been disclosed (see Patent Document 1). This ultrasonic flow sensor calculates the flow rate of the fluid flowing through the pipe based on the difference between the propagation time of an ultrasonic wave transmitted from a first ultrasonic element to a second ultrasonic element and the propagation time of an ultrasonic wave transmitted from the second ultrasonic element to the first ultrasonic element. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-158678 Summary of the Invention [Problem to be solved by the invention]

[0004] In the ultrasonic flow sensor described in Patent Document 1, a first ultrasonic element and a second ultrasonic element are attached to a pipe via a wedge material. However, in the ultrasonic flow sensor described in Patent Document 1, ultrasonic waves transmitted from the first ultrasonic element and the second ultrasonic element are directed obliquely with respect to the axis of the pipe, and therefore, a joint surface disposed obliquely with respect to the axis of the pipe is formed on the wedge material, which poses a problem that it is difficult to reduce the size in a direction perpendicular to the axis of the pipe.

[0005] The present disclosure is intended to solve the above-mentioned problems, and has an object to provide a flow rate calculation device and an ultrasonic flow meter that can make ultrasonic flow meters smaller than conventional ones. [Means for solving the problem]

[0006] The flow rate calculation device according to the present disclosure is characterized by comprising: a transmitting unit that transmits ultrasonic waves from one of a first transducer and a second transducer having a plurality of ultrasonic elements arranged in an array toward the other of the first transducer and the second transducer by beamforming; and a calculation unit that calculates the flow rate of the fluid in the pipe based on the difference between the time it takes for the ultrasonic waves from the first transducer to reach the second transducer through the fluid in the pipe and the time it takes for the ultrasonic waves from the second transducer to reach the first transducer through the fluid in the pipe, when the first transducer and the second transducer are arranged on opposite sides of the pipe. [Effects of the Invention]

[0007] According to the present disclosure, the flow calculation device transmits ultrasonic waves from one of the first transducer and the second transducer toward the other of the first transducer and the second transducer by beamforming, thereby making it possible to make the ultrasonic flow meter smaller than conventional ultrasonic flow meters. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram showing a schematic configuration of an ultrasonic flowmeter according to a first embodiment. [Figure 2] FIG. 2 is a diagram showing an example of the hardware configuration of a flow rate calculation unit according to the first embodiment. [Figure 3] FIG. 2 is a diagram showing an example of the hardware configuration of a flow rate calculation unit according to the first embodiment. [Figure 4] 4 is a flowchart showing processing performed by a flow rate calculation unit according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Embodiment 1 Fig. 1 is a block diagram showing a schematic configuration of an ultrasonic flowmeter according to embodiment 1. The ultrasonic flowmeter according to embodiment 1 is a device for measuring the flow rate of a fluid by transmitting and receiving ultrasonic waves to and from the fluid flowing inside a pipe 1. As shown in Fig. 1, the ultrasonic flowmeter according to embodiment 1 includes a pair of transducers 2, 3 consisting of a first transducer 2 and a second transducer 3 that transmit and receive ultrasonic waves, a flow rate calculation device 100 that calculates the flow rate of the fluid flowing inside the pipe 1 based on signals from the pair of transducers 2, 3, an operation unit 40, and a display unit 50, which are electrically connected to each other.

[0010] For example, the ultrasonic flowmeter according to the first embodiment is a clamp-on type ultrasonic flowmeter in which a pair of transducers 2 and 3 are configured to be detachably attached to the outer surface of the pipe 1. For example, the ultrasonic flowmeter has a holding unit (not shown) that detachably holds the pair of transducers 2 and 3 on the outer surface of the pipe 1 by generating external forces inward from a plurality of different positions in the circumferential direction of the pipe 1, for example, by clamping the pipe 1 or wrapping around the pipe 1. Also, for example, the ultrasonic flowmeter has a holding unit (not shown) that detachably holds the pair of transducers 2 and 3 on the outer surface of the pipe 1 by magnetically attracting the pair of transducers 2 and 3 to the outer surface of the pipe 1, which is made of a magnetic material. Also, for example, the ultrasonic flowmeter has an operator hold the pair of transducers 2 and 3 on the outer surface of the pipe 1, so that the pair of transducers 2 and 3 are detachably held on the outer surface of the pipe 1.

[0011] The first transducer 2 has a plurality of ultrasonic elements arranged in an array, and transmits (emits) ultrasonic waves by vibrating due to power supplied from the flow rate calculation device 100. Furthermore, when the first transducer 2 receives ultrasonic waves, the plurality of ultrasonic elements vibrate, thereby converting the ultrasonic waves into electric power. For example, the first transducer 2 has a plurality of ultrasonic elements arranged in an array along direction D1, which is the axial direction of the pipe 1. In other words, the first transducer 2 has a plurality of ultrasonic elements arranged in an array along the flow direction of the fluid in the pipe 1.

[0012] For example, the first transducer 2 has a plurality of piezoelectric elements arranged in an array as a plurality of ultrasonic elements arranged in an array. The first transducer may be configured by arranging ultrasonic elements processed individually in an array, or may be configured by an MUT (Micromachined Ultrasonic Transducer) formed using micromachining technology. Examples of such MUTs include PMUTs (Piezoelectric Micromachined Ultrasonic Transducers) and CMUTs (Capacitive Micromachined Ultrasonic Transducers).

[0013] Generally, ultrasonic elements made by sintering piezoelectric materials such as PZT (Lead Zirconate Titanate) and polarizing them by applying a strong electric field at high temperatures have the problem that the polarization disappears when the temperature exceeds the Curie point, and even if the temperature is then lowered, the sensitivity decreases compared to before the Curie point was exceeded. However, by constructing ultrasonic elements using PMUT or CMUT, it is possible to improve resistance to high temperatures.

[0014] The second transducer 3 has a plurality of ultrasonic elements arranged in an array. The details of the configuration of the second transducer 3 are the same as those of the first transducer 2, and therefore will not be described here.

[0015] When measuring the flow rate of a fluid in a pipe 1 using an ultrasonic flowmeter, the pair of transducers 2 and 3 are arranged on opposite sides of the pipe 1. For example, when measuring the flow rate of a fluid in the pipe 1 using an ultrasonic flowmeter, the pair of transducers 2 and 3 are arranged on opposite sides of the pipe 1 and at different positions in the D1 direction. In other words, when measuring the flow rate of a fluid in the pipe 1 using an ultrasonic flowmeter, the pair of transducers 2 and 3 are arranged on opposite sides of the pipe 1 and at positions offset from each other in the D1 direction. In other words, when measuring the flow rate of a fluid in the pipe 1 using an ultrasonic flowmeter, the pair of transducers 2 and 3 are arranged on opposite sides of the pipe 1 and at positions offset from each other in the D1 direction. In other words, when measuring the flow rate of a fluid in the pipe 1 using an ultrasonic flowmeter, the pair of transducers 2 and 3 are arranged on opposite sides of the pipe 1 and at positions where the ends of the transducers on one side in the D1 direction are at different positions from each other in the D1 direction.

[0016] For example, the ultrasonic flowmeter includes a position limiting member (not shown) that limits the relative position between the pair of transducers 2 and 3 to a preset position. Specifically, the ultrasonic flowmeter includes a base member as a position limiting member that holds the pair of transducers 2 and 3 and thereby limits the relative position in the D1 direction between at least the pair of transducers 2 and 3. Note that such a position limiting member may be any member that limits the relative position between the pair of transducers 2 and 3 at least when the ultrasonic flowmeter measures the flow rate of the fluid in the pipe 1, and may be configured to adjust the relative position between the pair of transducers 2 and 3 based on, for example, an operator's operation or an external input signal.

[0017] The operation unit 40 receives input operations from an operator and transmits signals corresponding to the input operations to the flow rate calculation device 100. For example, the operation unit 40 is configured with buttons, a touch panel, or other input devices. The display unit 50 receives signals from the operation unit 40 and signals from the calculation unit 60 and displays content corresponding to the received signals. For example, the display unit 50 is configured with a liquid crystal display panel, an organic or inorganic EL (Electroluminescence) panel, a dot matrix display, or other display device.

[0018] The flow rate calculation device 100 is electrically connected to a pair of transducers 2, 3. For example, the flow rate calculation device 100 is connected to each of the first transducer 2 and the second transducer 3 by electric wires the number of which corresponds to the number of ultrasonic elements included in the first transducer 2 and the second transducer 3. In other words, if the number of ultrasonic elements included in each of the first transducer 2 and the second transducer 3 is N, the flow rate calculation device 100 is connected to each of the first transducer 2 and the second transducer 3 by N electric wires.

[0019] The flow rate calculation device 100 includes a multiplexer 10, a transmitting unit 20, a receiving unit 30, and a calculation unit 60. The multiplexer 10 switches the connection between the pair of transducers 2, 3 and the transmitting unit 20 and receiving unit 30. In other words, the multiplexer 10 switches between a state in which the first transducer 2 and the transmitting unit 20 are connected by N electric wires and the second transducer 3 and the receiving unit 30 are connected by N electric wires, and a state in which the first transducer 2 and the receiving unit 30 are connected by N electric wires and the second transducer 3 and the transmitting unit 20 are connected by N electric wires.

[0020] The transmitting unit 20 supplies power to the pair of transducers 2, 3 via the multiplexer 10, and causes one of the first transducer 2 and the second transducer 3 to transmit ultrasonic waves toward the other of the first transducer 2 and the second transducer 3 by beamforming. For example, the transmitting unit 20 controls the phase of the ultrasonic waves transmitted from each ultrasonic element of one of the first transducer 2 and the second transducer 3, thereby transmitting ultrasonic waves from one of the first transducer 2 and the second transducer 3 so that the transmission direction of the ultrasonic waves is directed toward the other of the first transducer 2 and the second transducer 3.

[0021] The receiving unit 30 acquires, via the multiplexer 10, the power generated when the pair of transducers 2 and 3 receive the ultrasonic waves as an electrical signal.

[0022] When the first transducer 2 and the second transducer 3 are arranged on opposite sides of the pipe 1 and the transmitting unit 20 causes the first transducer 2 and the second transducer 3 to alternately transmit ultrasonic waves, the calculating unit 60 calculates the flow rate of the fluid in the pipe 1 based on the difference between the time it takes for the first ultrasonic wave from the first transducer 2 to reach the second transducer 3 through the fluid in the pipe 1 and the time it takes for the second ultrasonic wave from the second transducer 3 to reach the first transducer 2 through the fluid in the pipe 1.

[0023] For example, the calculation unit 60 calculates the flow rate of the fluid flowing inside the pipe 1 based on the following formulas (1) and (2): V is the velocity of the fluid, C is the speed of sound, L is the distance between the first transducer 2 and the second transducer 3, Φ is the sensor angle (the angle between the flow direction of the fluid and the transmission direction of the ultrasonic waves from the transducers), t1 is the propagation time of the first ultrasonic wave, t2 is the propagation time of the second ultrasonic wave, S is the cross-sectional area of ​​the pipe 1, Q is the flow rate, and k is a flow rate correction coefficient. V≒(C 2 / (2×L×cosΦ))×(t2-t1) ···(1) Q = k × S × V (2)

[0024] Configured in this manner, the flow rate calculation device 100 calculates the flow rate of the fluid flowing inside the pipe 1 and outputs the calculation result to an external device (not shown) or to the display unit 50. Note that the flow rate calculation device 100 may have some or all of the configurations and functions other than those of the flow rate calculation device 100 of the ultrasonic flowmeter described above, or some of the configurations and functions of the flow rate calculation device 100 may be provided by other configurations of the ultrasonic flowmeter.

[0025] Next, the hardware configuration of the flow rate calculation device 100 will be described with reference to FIGS. 2 and 3. FIG. 2 is a block diagram showing an example of the hardware configuration of the flow rate calculation device 100 according to the first embodiment, and FIG. 3 is a block diagram showing an example of a hardware configuration of the flow rate calculation device 100 according to the first embodiment, which is different from that shown in FIG. 2. For example, as shown in FIG. 2, the flow rate calculation device 100 includes a processor 100a, a memory 100b, and an I / O port 100c, and is configured so that the processor 100a reads and executes a program stored in the memory 100b. The memory 100b may be, for example, a non-volatile or volatile semiconductor memory such as RAM, ROM, flash memory, EPROM, or EEPROM. The memory 100b may also be a magnetic disk, a flexible disk, an optical disk, a compact disk, a minidisk, a DVD, or the like. The memory 100b may also be an HDD or an SSD.

[0026] 3, the flow rate calculation device 100 includes a processing circuit 100d and an I / O port 100c, which are dedicated hardware. The processing circuit 100d is configured, for example, by a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, a system LSI (Large-Scale Integration), an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. Each function of the flow rate calculation device 100 is realized by the processor 100a or the processing circuit 100d, which is dedicated hardware, executing a program that is software, firmware, or a combination of software and firmware. In addition to the above hardware, the flow rate calculation device 100 may also include other hardware for realizing the functions of the flow rate calculation device 100.

[0027] Next, details of the processing performed by the flow rate calculation device 100 according to the first embodiment will be described with reference to Fig. 1 and Fig. 4. Fig. 4 is a flowchart showing the processing performed by the flow rate calculation device 100 according to the first embodiment. The processing shown in Fig. 4 is processing in which the flow rate calculation device 100 calculates the flow rate of the fluid flowing inside the piping 1 based on the propagation time of the first ultrasonic wave and the propagation time of the second ultrasonic wave.

[0028] 4, when processing starts, the flow rate calculation device 100 causes the first transducer 2 to transmit ultrasonic waves toward the second transducer 3 (step ST01). In this processing, the flow rate calculation device 100 causes the transmitting unit 20 to transmit ultrasonic waves from the first transducer 2, with the transmitting unit 20 and the first transducer 2 being connected by the multiplexer 10.

[0029] In addition, if the relative position between the first transducer 2 and the second transducer 3 is not preset, for example, in this process, the flow calculation device 100 may be configured so that the transmitting unit 20 acquires information regarding the relative position between the first transducer 2 and the second transducer 3, and based on the acquired information regarding the relative position, the transmitting unit 20 controls the transmission direction of the ultrasonic waves from the first transducer and the second transducer so that the ultrasonic waves are transmitted from one of the first transducer and the second transducer to the other.

[0030] Specifically, the flow rate calculation device 100 may be configured such that the calculation unit 60 or the transmission unit 20 receives a signal transmitted from the operation unit 40 in response to an input operation by an operator, and the transmission unit 20 adjusts the transmission direction of the ultrasonic waves from the first transducer and the second transducer based on the received signal. Furthermore, specifically, the flow rate calculation device 100 may be configured such that the transmission unit 20 transmits ultrasonic waves from one of the first transducer and the second transducer so as to continuously change the direction, and the transmission unit 20 adjusts the transmission direction of the ultrasonic waves from the first transducer and the second transducer based on the intensity of the ultrasonic waves received by the other of the first transducer and the second transducer. Furthermore, specifically, the flow rate calculation device 100 may be configured such that the position of the other of the first transducer and the second transducer is detected based on a signal from a sensor (not shown) provided in at least one of the first transducer and the second transducer, and the transmission unit 20 adjusts the transmission direction of the ultrasonic waves from the first transducer and the second transducer based on the detection result.

[0031] After performing the process of step ST01, the flow rate calculation device 100 acquires a signal from the second transducer (step ST02). In this process, the flow rate calculation device 100 acquires the signal from the second transducer by the receiving unit 30 and transmits the acquired signal to the calculation unit 60.

[0032] After performing the processing of step ST02, the flow rate calculation device 100 calculates the propagation time of the ultrasonic waves (step ST03). In this processing, the flow rate calculation device 100 calculates the propagation time of the ultrasonic waves, which is the time from when the first transducer 2 transmits the ultrasonic waves to when the second transducer 3 receives the ultrasonic waves, using the calculation unit 60. In this processing, the calculation unit 60 may be configured to acquire, from the transmission unit 20, information indicating the time at which the transmission unit 20 causes the first transducer 2 to transmit the ultrasonic waves, or may be configured so that the calculation unit 60 controls the time at which the transmission unit 20 causes the first transducer 2 to transmit the ultrasonic waves.

[0033] After performing the process of step ST03, the flow rate calculation device 100 causes the second transducer to transmit ultrasonic waves toward the first transducer (step ST04). In this process, the flow rate calculation device 100 switches the state in which the transmission unit 20 and the first transducer 2 are connected by the multiplexer 10 from a state in which the transmission unit 20 and the second transducer 3 are connected, and causes the transmission unit 20 to transmit ultrasonic waves from the second transducer 3. Note that the process when the relative positions between the first transducer 2 and the second transducer 3 are not preset is the same as step ST01, and therefore a description thereof will be omitted.

[0034] After performing the process of step ST04, the flow rate calculation device 100 acquires a signal from the first transducer 2 (step ST05). In this process, the flow rate calculation device 100 acquires the signal from the first transducer 2 by the receiving unit 30 and transmits the acquired signal to the calculation unit 60.

[0035] After performing the processing of step ST05, the flow rate calculation device 100 calculates the propagation time of the ultrasonic waves (step ST06). In this processing, the flow rate calculation device 100 calculates the propagation time of the ultrasonic waves, which is the time from when the first transducer 2 transmits the ultrasonic waves until the second transducer 3 receives the ultrasonic waves, using the calculation unit 60. Note that the processing by the calculation unit 60 to acquire information indicating the time when the transmitting unit 20 causes the second transducer 3 to transmit the ultrasonic waves is similar to the processing by the calculation unit 60 to acquire information indicating the time when the transmitting unit 20 causes the first transducer 2 to transmit the ultrasonic waves in step ST03, and therefore a description thereof will be omitted.

[0036] After performing the processing of step ST06, the flow rate calculation device 100 calculates a propagation time difference (step ST07). In this processing, the flow rate calculation device 100 calculates a propagation time difference, which is the difference between the propagation time calculated in step ST03 and the propagation time calculated in step ST06. For simplicity of explanation, the propagation time difference is calculated using the difference between the propagation time calculated in step ST03 and the propagation time calculated in step ST06, but a method of calculating the propagation time difference from the peak position of the cross-correlation function of the signal acquired in step ST02 and the signal acquired in step ST05 may also be used.

[0037] After performing the process of step ST07, the flow rate calculation device 100 calculates the flow rate of the fluid (step ST08), and after performing the process of step ST08, the flow rate calculation device 100 outputs the calculation result (step ST09) and ends the process.

[0038] As described above, the flow rate calculation device 100 according to the first embodiment includes a transmitting unit 20 that transmits ultrasonic waves from one of the first transducer 2 and the second transducer 3, each having a plurality of ultrasonic elements arranged in an array, toward the other of the first transducer 2 and the second transducer 3 by beamforming, and a calculation unit 60 that calculates the flow rate of the fluid in the pipe 1 based on the difference between the time it takes for the ultrasonic waves from the first transducer 2 to reach the second transducer 3 through the fluid in the pipe 1 and the time it takes for the ultrasonic waves from the second transducer 3 to reach the first transducer 2 through the fluid in the pipe 1, when the first transducer 2 and the second transducer 3 are arranged on opposite sides of the pipe 1.

[0039] Configured in this manner, the flow calculation device 100 transmits ultrasonic waves from one of the first transducer 2 and the second transducer 3 toward the other of the first transducer 2 and the second transducer 3 by beamforming, so that when transmitting ultrasonic waves in a direction intersecting the normal direction to the inner surface of the pipe 1, the ultrasonic flow meter does not need to be equipped with a wedge material or the like that is thick in the normal direction, and the ultrasonic flow meter can be made smaller than conventional ones.

[0040] Furthermore, the wedge material in an ultrasonic flowmeter is generally made of synthetic resin, and depending on the operating temperature of the flow calculation device, such as the ambient temperature when the ultrasonic flowmeter is used, the temperature of the fluid, and the temperature of the piping, and the material of the wedge material, the wedge material may deteriorate or deform, resulting in a decrease in measurement accuracy. In contrast, the flow calculation device 100 according to the first embodiment does not require such a wedge material, and therefore prevents the operating temperature of the ultrasonic flowmeter from being restricted by the wedge material.

[0041] Furthermore, the flow rate calculation device 100 according to the first embodiment is configured to acquire information relating to the relative positions between the first transducer 2 and the second transducer 3, and to control the transmission direction of ultrasonic waves from the first transducer 2 and the second transducer 3 based on the acquired information relating to the relative positions. With this configuration, the flow rate calculation device 100 can transmit ultrasonic waves from one of the first transducer 2 and the second transducer 3 to the other, regardless of the diameter and shape of the pipe 1 to which it is attached.

[0042] In the first embodiment, the flow rate calculation device 100 is configured to transmit ultrasonic waves from the first transducer 2 and the second transducer 3 in a direction intersecting the normal direction to the inner surface of the pipe 1, but is not limited to this. The flow rate calculation device only needs to be configured to emit ultrasonic waves in a direction in which the dot product of the flow direction of the fluid in the pipe and the emission direction of the ultrasonic waves is not zero, and for example, depending on the shape of the pipe 1, the flow rate calculation device may be configured to transmit ultrasonic waves in a direction along the flow direction of the fluid.

[0043] Furthermore, in the first embodiment, the flow rate calculation device 100 is arranged so that the first transducer 2 and the second transducer 3 are at different positions in the D1 direction, but this is not limiting. The flow rate calculation device may be configured to emit ultrasonic waves in a direction in which the dot product of the flow direction of the fluid in the pipe and the emission direction of the ultrasonic waves is not zero, and for example, the flow rate calculation device may be configured so that the first transducer 2 and the second transducer are arranged opposite each other, and ultrasonic waves are transmitted from one of the first transducer and the second transducer to the end of the other in the D1 direction.

[0044] In addition, in the present disclosure, any component of the embodiments may be modified or any component of the embodiments may be omitted. [Explanation of symbols]

[0045] 1: Piping 2: First transducer 3: Second transducer 10: Multiplexer 20: Transmitter 30: Receiving unit 40:Operation unit 50:Display section 60: Arithmetic section 100:Flow rate calculation device

Claims

1. a transmitting unit that transmits ultrasonic waves from one of a first transducer and a second transducer having a plurality of ultrasonic elements arranged in an array toward the other of the first transducer and the second transducer by beamforming; a calculation unit that calculates a flow rate of the fluid in the pipe based on a difference between a time taken for an ultrasonic wave from the first transducer to reach the second transducer through the fluid in the pipe and a time taken for an ultrasonic wave from the second transducer to reach the first transducer through the fluid in the pipe, with the first transducer and the second transducer being disposed on opposite sides of the pipe. A flow rate calculation device characterized by:

2. The transmitting unit transmits ultrasonic waves from the first transducer and the second transducer in a direction intersecting a normal direction to an inner surface of the pipe.

2. The flow rate calculation device according to claim 1.

3. The calculation unit calculates the flow rate of the fluid in the pipe based on the difference between the time it takes for the ultrasonic wave from the first transducer to reach the second transducer through the fluid in the pipe and the time it takes for the ultrasonic wave from the second transducer to reach the first transducer through the fluid in the pipe, with the first transducer and the second transducer being disposed at different positions in a direction perpendicular to the normal direction to the inner surface of the pipe.

2. The flow rate calculation device according to claim 1.

4. The transmitting unit acquires information about a relative position between the first transducer and the second transducer, and controls a transmission direction of ultrasonic waves from the first transducer and the second transducer based on the acquired information about the relative position.

2. The flow rate calculation device according to claim 1.

5. A flow rate calculation device according to any one of claims 1 to 4; the first transducer; the second transducer; 1. An ultrasonic flow meter comprising:

6. a holding portion that detachably holds the first transducer and the second transducer on the outer surface of the pipe; 6. The ultrasonic flowmeter according to claim 5.

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