JP7125340B2 - ULTRASONIC FLOW METER, FLOW CALCULATION DEVICE, AND METHOD FOR DETERMINING UNFULL WATER STATE - Google Patents

Description

TECHNICAL FIELD The present invention relates to an ultrasonic flowmeter, and more particularly to a technique for judging that the inside of a measuring pipe is not filled with water.

In general, flow rate measurement using ultrasonic waves is based on the premise that the inside of the measurement tube is filled with fluid, and that the ultrasonic beam propagates in the fluid along an assumed beam path. For this reason, if the inside of the measuring tube is not filled with fluid, not only is it impossible to measure the correct fluid flow rate, but also the calculation of the fluid volume based on the cross-sectional area of the measuring tube becomes inaccurate. It causes an error in the measurement.

Conventionally, as a technique for determining such a non-full-water state, a technique has been proposed in which the received signal strength of ultrasonic waves is compared with a preset threshold value, and the non-full-water state is determined based on the obtained comparison result. (See, for example, Patent Documents 1 and 2).

JP 2015-184173 A JP 2017-116458 A JP 2013-178125 A

In some ultrasonic flowmeters, the beam path along which the ultrasonic beam propagates from one ultrasonic transmitter/receiver attached to the measuring pipe to the other ultrasonic transmitter/receiver intersects the fluid level when the water level is not full. . For example, there is a method in which the measurement accuracy of the flow rate is improved by extending the beam path length by reflecting the ultrasonic beam on the inner wall surface of the measuring tube, which has a polygonal shape in cross section (see, for example, Patent Document 3). ). In such a configuration, depending on the height of the fluid surface in the measurement tube, the ultrasonic beam may be reflected by the fluid surface and may not propagate along the assumed beam path.

When the above-described conventional non-full-water determination technology is applied to an ultrasonic flowmeter having such a configuration, the ultrasonic beam may be reflected by the fluid surface depending on the height of the fluid surface in the measurement pipe. , there may be a case where the signal is received on a beam path different from the assumed beam path. In such cases, as the beam path length is shortened/extended, the received signal strength of the ultrasonic beam increases/decreases, resulting in an erroneous determination that the water level is full even though the water level is not full. There was a problem. As a result, not only is it impossible to accurately measure the flow velocity of the fluid, but the calculation of the fluid volume based on the cross-sectional area of the measurement tube becomes inaccurate, which causes an error in flow measurement.

SUMMARY OF THE INVENTION The present invention is intended to solve such problems, and it is an object of the present invention to provide a non-full state determination technique that can appropriately determine a non-full state even when the beam path length of an ultrasonic beam changes. .

In order to achieve such an object, the ultrasonic flowmeter according to the present invention comprises a measurement pipe through which a fluid to be measured flows, and first and second ultrasonic transmission/reception arranged on the peripheral surface of the measurement pipe. and a flow computing device that measures the flow rate of the fluid based on the propagation time of the ultrasonic beam that propagates in the fluid and is transmitted and received between the first and second ultrasonic transmitters/receivers. A sonic flowmeter, wherein the flow rate computing device includes a first sonic velocity calculator that calculates a first sonic velocity with respect to the ultrasonic beam based on the fluid temperature of the fluid, and a propagation time of the ultrasonic beam a second speed-of-sound calculator that calculates a second speed of sound for the ultrasonic beam based on a reference beam path length of a normal beam path; and at least the speed of sound between the first speed of sound and the second speed of sound and a non-full state determination unit that determines that the liquid level of the fluid is in a non-full state when the error is out of a preset error tolerance range.

Further, in one configuration example of the ultrasonic flowmeter according to the present invention, the non-full state determination unit sets the reception intensity of the ultrasonic beam in advance when the sound speed error is within the error allowable range. It is determined whether the liquid level of the fluid is full or not, depending on whether or not it is equal to or higher than the predetermined strength threshold.

In one configuration example of the ultrasonic flowmeter according to the present invention, the error tolerance range is a range between a lower threshold value and an upper threshold value.

In one configuration example of the ultrasonic flowmeter according to the present invention, the error allowable range is a range equal to or greater than an arbitrary threshold or equal to or less than an arbitrary threshold.

Further, in one configuration example of the ultrasonic flowmeter according to the present invention, the non-full state determination unit includes a sound velocity error determination result indicating that the sound velocity error is within the error allowable range, and the ultrasonic wave It is determined that the water level is not full based on the AND of the signal strength determination result indicating that the received beam strength is equal to or higher than the strength threshold value.

Further, in one configuration example of the ultrasonic flowmeter according to the present invention, the beam path of the ultrasonic beam has an inclination with respect to the tube axis of the measurement tube, and the inner wall surface of the measurement tube has at least It has two reflection points.

In one configuration example of the ultrasonic flowmeter according to the present invention, the trajectory of the beam path projected onto a plane orthogonal to the tube axis of the measurement tube forms a substantially triangular shape.

A flow rate computing device according to the present invention is an ultrasonic flowmeter comprising a measuring tube through which a fluid to be measured flows, and first and second ultrasonic transmitters/receivers arranged on the peripheral surface of the measuring tube. A flow rate calculation device that is used to measure the flow rate of the fluid based on the propagation time of the ultrasonic beam transmitted and received between the first and second ultrasonic transmitters/receivers and propagating in the fluid, a first speed-of-sound calculator for calculating a first speed-of-sound for said ultrasonic beam based on the fluid temperature of said fluid; a second speed-of-sound calculator for calculating a second speed of sound with respect to the ultrasonic beam; and a non-full state determination unit that determines that the liquid level of the fluid is in a non-full state when the water level is outside.

Further, a non-full-water state determination method according to the present invention includes: a measuring pipe through which a fluid to be measured flows; first and second ultrasonic transmitters/receivers arranged on the circumferential surface of the measuring pipe; Non used in an ultrasonic flowmeter comprising a flow computing device that measures the flow rate of the fluid based on the propagation time of the ultrasonic beam that propagates in the fluid and is transmitted and received between the second ultrasonic transmitter and receiver A first sound velocity calculation step in which the flow rate calculation device calculates a first sound speed with respect to the ultrasonic beam based on the fluid temperature of the fluid, and the flow rate calculation device performs the A second speed-of-sound calculation step of calculating a second speed of sound for the ultrasonic beam based on the propagation time of the ultrasonic beam and a reference beam path length of a normal beam path; a non-full state determination step of determining that the liquid level of the fluid is in a non-full state when a sound speed error between the first sound speed and the second sound speed is outside a preset error tolerance range; It has

According to the present invention, even when the beam path length of the ultrasonic beam changes, it is possible to appropriately determine the non-full water condition. Therefore, if the non-full-water condition is notified to the host device along with the measured flow rate of the fluid, not only can the host device determine that the flow rate contains an error, but the occurrence of the non-full-water condition can be notified as an alarm. can be done.

FIG. 1 is a block diagram showing the configuration of an ultrasonic flowmeter. FIG. 2 is an explanatory diagram showing the beam path (full water condition). FIG. 3 is an explanatory diagram showing a beam path (unfilled state). FIG. 4 is a flowchart showing the non-full-water state determination process. FIG. 5 is a graph showing an operation example (only ultrasonic reception intensity) of the conventional non-full water condition determination. FIG. 6 is a graph showing an operation example (sound speed error+ultrasonic wave reception intensity) of non-full water condition determination according to the present invention.

Next, one embodiment of the present invention will be described with reference to the drawings.
[Ultrasonic flow meter]
First, an ultrasonic flowmeter 1 according to this embodiment will be described with reference to FIG. FIG. 1 is a block diagram showing the configuration of an ultrasonic flowmeter.
As shown in FIG. 1, the ultrasonic flowmeter 1 is arranged between ultrasonic transmitters/receivers (transducers) UA and UB arranged on the peripheral surface of the measuring pipe P, and an ultrasonic beam passing through the fluid flowing in the measuring pipe P. B, and measures the flow rate Q of the fluid based on the propagation times t1 and t2 of the ultrasonic beam B obtained. In the present invention, these ultrasonic transmitter/receivers UA and UB may be referred to as first and second ultrasonic transmitter/receivers.

FIG. 2 is an explanatory diagram showing the beam path (full water condition). FIG. 3 is an explanatory diagram showing a beam path (unfilled state). This ultrasonic flowmeter 1 has a measuring pipe P that has a hexagonal cross-sectional shape, and the ultrasonic beam B is reflected by the inner wall surface of the measuring pipe P to extend the beam path length (for example, patent Reference 3, etc.). When the water is full, as shown in FIG. 2, the forward ultrasonic beam B transmitted from the ultrasonic transmitter/receiver UA is first reflected by the inner wall surface PA, then reflected by the inner wall surface PB, and ultrasonic wave transmission/reception is performed. received by device UB. In addition, the reverse ultrasonic beam B transmitted from the ultrasonic transmitter/receiver UB is reflected by the inner wall surface PB in the opposite direction to the forward direction, then reflected by the inner wall surface PA, and received by the ultrasonic transmitter/receiver UA. .

On the other hand, in the non-full state, depending on the fluid level, as shown in FIG. 3, the forward ultrasonic beam B transmitted from the ultrasonic transmitter/receiver UA is first reflected by the inner wall surface PA, and then After being reflected by the liquid surface F1 and reflected again by the inner wall surface PA, it may be reflected by the liquid surface F2 and received by the ultrasonic transmitter/receiver UB. At this time, since the beam path length Lx differs from the reference beam path length Ls of the beam path presumed in the full water state as shown in FIG. 2, the received signal strength of the ultrasonic beam B increases/decreases. . Therefore, as in the prior art, when the non-full water state is determined by comparing the received signal strength with a preset strength threshold value, the water level is full despite the non-full water state. This is an erroneous judgment result.

[Principle of the present invention]
Ultrasonic waves are defined as sound waves having a high frequency that cannot be heard by the human ear, and are generally considered to be sound waves of 20 kHz or higher. Such ultrasonic waves have properties similar to those of audible sounds that can be heard by the human ear. has the property of being determined by

The first sound velocity C1 for sound propagating in water is determined based on the fluid temperature T by the following equation (1), called the Greenspan-Tschiegg empirical equation (1957).

On the other hand, in the ultrasonic flowmeter, the second sound velocity C2 of the ultrasonic beam B propagating through the fluid is obtained by the following equation (2) based on the beam path length L and the propagation times t1 and t2.

Here, the reference beam path length Ls of the beam path R assumed in advance is used as the beam path length L in Equation (2). Therefore, as shown in FIG. 3, when the beam path length Lx differs from the reference beam path length Ls due to the non-full water condition, the beam path length L in equation (2) remains the reference beam path length Ls. However, the propagation times t1 and t2 change. Therefore, the sound speed error ΔC (=C2−C1) between the second sound speed C2 obtained by Equation (2) and the first sound speed C1 obtained by Equation (1) increases.

The present invention focuses on the relationship between the change in the beam path length L and the sound velocity error ΔC due to such a non-filled state, and calculates the first sound velocity C1 from the fluid temperature T, and measures the assumed reference beam path length Ls and A second sound speed C2 is obtained from the propagation times t1 and t2, and a threshold value is applied to the sound speed error .DELTA.C between the two to determine the non-full water condition.

Next, referring to FIG. 1, the configuration of the ultrasonic flowmeter 1 according to this embodiment will be described in detail.
As shown in FIG. 1, an ultrasonic flowmeter 1 is arranged on a measuring pipe P through which a fluid to be measured flows, and on the upstream and downstream sides of the peripheral surface of the measuring pipe P with respect to the direction in which the fluid flows. A pair of ultrasonic transmitters/receivers (transducers) UA and UB, and a flow rate calculation device 10 for signal processing the received waves of the ultrasonic beam B transmitted and received between the UA and UB in the forward and reverse directions to calculate and output the flow rate. I have it. In the present invention, the direction in which the ultrasonic beam B propagates from the UA on the upstream side where the fluid flows to the UB on the downstream side where the fluid flows is called the forward direction. The direction in which the ultrasonic beam B propagates is called the reverse direction.

Further, in the present embodiment, the beam path of the ultrasonic beam B is inclined with respect to the tube axis O of the measurement tube P as shown in FIG. 1, and as shown in FIGS. , the inner wall surface of the measuring pipe P has at least two reflection points (PA, PB), and the trajectory projected onto the plane orthogonal to the pipe axis O of the measuring pipe P forms a substantially triangular shape. Note that the beam path is not limited to this. For example, any beam path can be similarly applied as long as the beam path is such that the ultrasonic beam B intersects the fluid level when the fluid level drops from the full water level.

As shown in FIG. 1, the flow rate computing device 10 includes an input/output I/F circuit 11, a memory circuit 12, an upper I/F circuit 13, and an arithmetic processing circuit 14 as main circuit units. These circuit units are connected so as to be able to exchange data via an internal bus BUS.

The input/output I/F circuit 11 transmits a control signal for controlling the transmission and reception of ultrasonic waves and a received signal indicating the signal strength of the received ultrasonic waves to and from the ultrasonic transmitter/receivers (transducers) UA and UB. It is a circuit unit that exchanges via the wiring L1 and obtains a measurement signal indicating the fluid temperature T measured by the temperature sensor K attached to the measuring pipe P via the wiring L2.

The memory circuit 12 is a memory device such as a semiconductor memory, and is a circuit unit that stores various processing data and programs used for flow rate measurement processing and non-full water state determination processing in the arithmetic processing circuit 14 .

The host I/F circuit 13 is a circuit unit that transmits flow rate data indicating the flow rate measured by the arithmetic processing circuit 14 and status data indicating a non-full water state to a host device such as a controller via the communication line L3. .

The arithmetic processing circuit 14 has a CPU and its peripheral circuits, reads the program of the storage circuit 12, executes it by the CPU, and uses it for flow rate measurement processing and non-full water state determination processing by cooperating hardware and software. It is a circuit unit that realizes various processing units.
Main processing units realized by the arithmetic processing circuit 14 include a measurement unit 14A, a first sound speed calculation unit 14B, a second sound speed calculation unit 14C, a non-full water condition determination unit 14D, and a flow rate calculation unit 14E.

The measurement unit 14A controls the ultrasonic transmitter/receivers UA and UB via the input/output I/F circuit 11 and the wiring L1 at fixed measurement intervals, thereby repeating the ultrasonic transmitter/receivers UA and UB for a predetermined number of times. Between the UBs, the ultrasonic beam B passing through the fluid flowing in the measuring pipe P is transmitted and received in the forward and reverse directions, and the obtained received signals are statistically processed to calculate the propagation times t1 and t2 and store them in the storage circuit 12. By controlling the temperature sensor K via the input/output I/F circuit 11 and the wiring L2, the temperature T of the fluid flowing through the measuring pipe P is acquired and stored at regular measurement intervals. and a function of storing in the circuit 12 .

The first speed-of-sound calculator 14B has a function of calculating the first speed-of-sound C1 based on the fluid temperature T acquired from the storage circuit 12, for example, by using the above-described formula (1).
The second speed-of-sound calculator 14C uses, for example, the above-described formula (2) based on the propagation times t1 and t2 acquired from the storage circuit 12 and the reference beam path length Ls preset in the storage circuit 12. Therefore, it has a function of calculating the second speed of sound C2.

The non-full-water state determination unit 14D calculates the sound speed error ΔC between the first sound speed C1 and the second sound speed C2, and stores the obtained sound speed error ΔC and the error allowable range E preset in the storage circuit 12. a comparing function, and at least a function of determining that the liquid level H of the fluid is not full when the sound speed error ΔC is out of the preset error allowable range E, and storing it in the storage circuit 12. have.

In addition, the non-full water state determination unit 14D has a function of comparing the ultrasonic wave reception intensity S acquired from the storage circuit 12 and the intensity threshold value Sth preset in the storage circuit 12, and the sound speed error ΔC is within the error allowable range. If it is within the range of E, it is determined whether the fluid level is full or not according to whether the ultrasonic wave reception intensity S is equal to or higher than the intensity threshold value Sth, and stored in the storage circuit 12. It has the function to

The flow rate calculation unit 14E determines the flow rate in the measuring pipe P based on the propagation times t1 and t2, the fluid temperature T, the reference beam path length Ls, and the first sound velocity C1 or the second sound velocity C2 acquired from the storage circuit 12. It has a function of calculating the flow rate Q of the fluid and storing it in the memory circuit 12 .

The flow rate Q of the fluid flowing through the measuring pipe P is determined by the product of the flow velocity V and the cross-sectional area A of the measuring pipe P. Also, the flow velocity V is obtained by the following equation (3) based on the propagation times t1 and t2, the sound velocity C, the beam path length L, and the angle θ between the beam path and the flow direction of the fluid.

[Operation of this embodiment]
Next, the operation of the ultrasonic flowmeter 1 according to this embodiment will be described with reference to FIG. FIG. 4 is a flowchart showing the non-full-water state determination process.
The arithmetic processing circuit 14 executes the non-full-water state determination process of FIG.

First, the first speed-of-sound calculator 14B calculates the first speed-of-sound C1 based on the fluid temperature T acquired from the storage circuit 12, for example, using the above-described formula (1) (step S100). Further, the second speed-of-sound calculation unit 14C, based on the propagation times t1 and t2 acquired from the storage circuit 12 and the reference beam path length Ls set in advance in the storage circuit 12, for example, the above equation (2) is used to calculate the second speed of sound C2 (step S101).

Subsequently, the non-full state determination unit 14D calculates the sound speed error ΔC between the first sound speed C1 and the second sound speed C2 (step S102), and the obtained sound speed error ΔC and is compared with the allowable error range E (step S103).
In step S103, if the sound velocity error ΔC is within the error allowable range E (step S103: YES), the non-full water state determination unit 14D sets the ultrasonic reception intensity S acquired from the storage circuit 12 and the storage circuit 12 in advance. is compared with the intensity threshold value Sth (step S104).

In step S104, if the ultrasonic wave reception intensity S is equal to or greater than the intensity threshold value Sth (step S104: YES), the non-full-water state determination unit 14D determines that the measuring pipe P is in the full-water state, and stores the The data is saved (step S105), and the series of non-full water state determination processing ends.

On the other hand, in step S103, if the sound velocity error ΔC is not within the error allowable range E (step S103: NO), and in step S104, if the ultrasonic reception intensity S is less than the intensity threshold value Sth (step S104: NO ), the non-full state determination unit 14D determines that the measuring pipe P is in the non-full state, stores it in the storage circuit 12 (step S106), and ends the series of non-full state determination processing.

In FIG. 4, the execution processing order of steps S103 and S104 may be interchanged. Alternatively, step S103 and step S104 may be executed in parallel, and step S105 or step S106 may be selectively executed based on the AND of the obtained comparison results. As a specific example, as shown in FIG. 6 described later, the sound speed error determination result Rc indicating that the sound speed error ΔC is within the error allowable range E, and the ultrasonic reception intensity S of the ultrasonic beam B are intensified. It may be determined that the water level is not full based on the AND with the signal strength determination result Rs indicating that the water level is equal to or greater than the threshold value Sth.

[Example of operation of the present embodiment]
First, with reference to FIG. 5, an operation example of conventional non-full water state determination will be described. FIG. 5 is a graph showing an operation example (only ultrasonic reception intensity) of the conventional non-full water condition determination. FIG. 5 is a graph showing changes in the received ultrasonic wave strength S when the liquid level H is gradually lowered from the full state with the lapse of time.

As the liquid level H decreases from the full water level, the ultrasonic beam B is reflected by the fluid level, and the ultrasonic transmitter-receivers UA and UB are exposed to the air. As a result, the beam path of the ultrasonic beam B is disturbed and the strength of the ultrasonic signal to be transmitted is lowered. As shown in FIG. 5, when the ultrasonic reception intensity S falls below the intensity threshold value Sth at time T1, the signal intensity determination result Rs changes from H (High) level to L (Low) level. The signal strength determination result Rs is a logic value inside the water non-full state determination unit 14D that indicates H level when S≧Sth, and indicates L level when S<Sth.

After that, at the subsequent time Ts1, for example, as shown in FIG. 3, when the ultrasonic beam B happens to be received by the fluid surfaces F1 and F2, the received ultrasonic wave intensity S temporarily decreases to the intensity threshold value Sth Ascend to a higher level. As a result, the signal strength determination result Rs becomes H level in the period Ws from time Ts1 to time Ts2 when S≧Sth.

Therefore, when the non-full state is determined based on the signal strength determination result Rs, the non-full state determination result Rm is different from the actual liquid level H, indicating the H level indicating the full state during the period Ws. . The non-full water condition determination result Rm is a logic value inside the non-full water condition judging section 14D that indicates the H level when the water level is full and indicates the L level when the water level is not full.

Next, with reference to FIG. 6, an operation example of non-full water condition determination according to the present invention will be described. FIG. 6 is a graph showing an operation example (sound speed error+ultrasonic wave reception intensity) of non-full water condition determination according to the present invention. FIG. 6 is a graph showing changes in the sound velocity error ΔC when the liquid level H is gradually lowered from the full state with the lapse of time. Here, as the error allowable range E, it is assumed that a belt-shaped allowable range consisting of a lower threshold value EL and an upper threshold value EH is set. For reference, the ultrasonic reception intensity S in FIG. 5 is also shown.

If the beam path of the ultrasonic beam B is disturbed or the intensity of the ultrasonic signal to be transmitted is lowered as the liquid level H drops, the beam path length L changes and the propagation times t1 and t2 change. . Therefore, the second sound speed C2 obtained by the above-described equation (2) changes, and the sound speed error ΔC changes. Specifically, when the beam path length L is extended, the propagation times t1 and t2 become longer, C2 becomes smaller, and ΔC also becomes smaller. When the beam path length L is shortened, the propagation times t1 and t2 are shortened, C2 is increased, and ΔC is also increased.

As shown in FIG. 6, when the ultrasonic wave reception strength S falls below the strength threshold value Sth at time T1, the signal strength determination result Rs changes from H level to L level. After that, when the speed-of-sound error ΔC falls below the lower limit threshold EL at time T2, the speed-of-sound error determination result Rc changes from the H level to the L level. The sound velocity error determination result Rc indicates the H level when ΔC is within the error allowable range E, and indicates the L level when ΔC is outside the error allowable range E. value.

During the period Ws from Ts1 to time Ts2, S≧Sth, and the signal strength determination result Rs temporarily changes from L level to H level. After that, at time Tc1, the speed-of-sound error ΔC becomes equal to or greater than the lower limit threshold EL and rises to a level within the error allowable range E, and then exceeds the upper limit threshold EH at time Tc2. In the period Wc up to, the sound velocity error determination result Rc becomes H level.

Therefore, when the non-full state determination result Rm is obtained before time T1 at which both Rs and Rc are at the H level After that, even if one of Rs and Rc becomes H level, such as period Ws or period Wc, like the actual liquid level H, It indicates the L level indicating the non-full water condition.

In the above description, the error permissible range E is defined by a belt-shaped range consisting of the lower threshold value EL and the upper threshold value EH, but the present invention is not limited to this. The beam path of the ultrasonic beam B of the ultrasonic flowmeter 1 is determined by the arrangement of the ultrasonic transmitters/receivers UA and UB, the arrangement of the inner wall surface of the measuring pipe P, and the liquid level H. Therefore, depending on the beam path, there may be a fixed condition in which a period Ws in which the ultrasonic reception intensity S exceeds the intensity threshold value Sth and a period in which the sound speed error ΔC falls below the lower limit threshold value EL occur. .

For example, as shown in FIG. 6, when the period Ws occurs only during the period when the speed-of-sound error ΔC is below the lower limit threshold EL, the upper limit threshold EH can be omitted from the error allowable range E. As a result, the allowable error range E is defined as a range equal to or greater than an arbitrary threshold value Eth. Conversely, if the period Ws occurs only during the period in which the speed-of-sound error ΔC exceeds the upper limit threshold EH, the lower limit threshold EL can be omitted from the allowable error range E. As a result, the allowable error range E is defined as a range equal to or less than an arbitrary threshold value Eth.

[Effects of this embodiment]
As described above, in the present embodiment, the first speed-of-sound calculation unit 14B calculates the first speed-of-sound C1 for the ultrasonic beam B based on the fluid temperature T of the fluid, and the second speed-of-sound calculation unit 14C , based on the propagation times t1 and t2 of the ultrasonic beam B and the reference beam path length Ls of the regular beam path, the second sound velocity C2 for the ultrasonic beam B is calculated, and the non-full water state determination unit 14D determines at least , when the sound speed error ΔC between the first sound speed C1 and the second sound speed C2 is outside the range of the error tolerance E set in advance, it is determined that the liquid level of the fluid is not full. It is a thing.

More specifically, when the sound velocity error ΔC is within the error allowable range E, the non-full-water state determination unit 14D determines that the ultrasonic reception intensity S of the ultrasonic beam B is a preset intensity threshold value. Whether the liquid level of the fluid is full or not is determined according to whether or not it is equal to or higher than the value Sth.
As a result, even when the beam path length L of the ultrasonic beam B changes, it is possible to appropriately determine the non-full water condition. Therefore, if the measured fluid flow rate Q and the non-full-water state are notified to the host device, not only can the host device determine that the flow rate Q contains an error, but the occurrence of the non-full-water state is notified as an alarm. can do.

[Expansion of Embodiment]
Although the present invention has been described with reference to the embodiments, the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

DESCRIPTION OF SYMBOLS 1... Ultrasonic flowmeter, 10... Flow calculation apparatus, 11... Input-output I/F circuit, 12... Storage circuit, 13... Upper-level I/F circuit, 14... Arithmetic processing circuit, 14A... Measuring part, 14B... First 14C... second sound velocity calculator, 14D... non-full water state determination part, 14E... flow rate calculator, P... measuring pipe, PA, PB, PC... inner wall surface, UA... ultrasonic transmitter/receiver (first 1 ultrasonic transmitter/receiver), UB... ultrasonic transmitter/receiver (second ultrasonic transmitter/receiver), K... temperature sensor, B... ultrasonic beam, t1, t2... propagation time, L... beam path length, Ls... Reference beam path length, T... Fluid temperature, C1... First sound speed, C2... Second sound speed, ΔC... Sound speed error, E... Error tolerance, EL... Lower limit threshold, EH... Upper limit threshold, S Received ultrasonic wave intensity, Sth: intensity threshold value, V: flow velocity, A: cross-sectional area, Q: flow rate, L1, L2: wiring, L3: communication line, BUS: internal bus.

Claims (9)

Transmitted and received between a measurement tube through which a fluid to be measured flows, first and second ultrasonic transmitters and receivers arranged on the peripheral surface of the measurement tube, and the first and second ultrasonic transmitters and receivers, An ultrasonic flowmeter comprising a flow rate computing device that measures the flow rate of the fluid based on the propagation time of the ultrasonic beam propagating in the fluid,
The flow rate computing device is
a first speed-of-sound calculator that calculates a first speed of sound with respect to the ultrasonic beam based on the fluid temperature of the fluid;
a second speed-of-sound calculator that calculates a second speed of sound with respect to the ultrasonic beam based on the propagation time of the ultrasonic beam and a reference beam path length of a normal beam path;
A non-full state determining that the liquid level of the fluid is in a non-full state when at least a sound speed error between the first sound speed and the second sound speed is out of a preset error tolerance range. An ultrasonic flowmeter comprising: a determination unit; The ultrasonic flowmeter according to claim 1,
When the sound velocity error is within the error allowable range, the non-full water state determination unit determines whether or not the reception intensity of the ultrasonic beam is equal to or greater than a preset intensity threshold value. An ultrasonic flowmeter that determines whether the liquid level of the fluid is full or not. In the ultrasonic flowmeter according to claim 1 or claim 2,
The ultrasonic flowmeter, wherein the error tolerance range is a range between a lower threshold value and an upper threshold value. In the ultrasonic flowmeter according to claim 1 or claim 2,
The ultrasonic flowmeter, wherein the error tolerance range is a range equal to or greater than an arbitrary threshold or equal to or less than an arbitrary threshold. The ultrasonic flowmeter according to claim 2,
The non-full state determination unit provides a sound velocity error determination result indicating that the sound velocity error is within the error allowable range, and a signal indicating that the reception intensity of the ultrasonic beam is equal to or greater than the intensity threshold value. An ultrasonic flowmeter that determines a non-full-water state based on a logical product with a strength determination result. In the ultrasonic flowmeter according to any one of claims 1 to 5,
An ultrasonic flowmeter, wherein the beam path of the ultrasonic beam is inclined with respect to the tube axis of the measurement tube, and has at least two reflection points on the inner wall surface of the measurement tube. The ultrasonic flowmeter according to claim 6,
The ultrasonic flowmeter according to claim 1, wherein the beam path has a locus projected on a plane perpendicular to the tube axis of the measurement tube and forms a substantially triangular locus. Used in an ultrasonic flowmeter comprising a measuring tube through which a fluid to be measured flows, and first and second ultrasonic transmitters/receivers arranged on the peripheral surface of the measuring tube, wherein the first and second A flow rate calculation device that measures the flow rate of the fluid based on the propagation time of an ultrasonic beam that propagates in the fluid and is transmitted and received between ultrasonic transmitters and receivers,
a first speed-of-sound calculator that calculates a first speed of sound with respect to the ultrasonic beam based on the fluid temperature of the fluid;
a second speed-of-sound calculator that calculates a second speed of sound with respect to the ultrasonic beam based on the propagation time of the ultrasonic beam and a reference beam path length of a normal beam path;
A non-full state in which it is determined that the liquid level of the fluid is in a non-full state when at least a sound speed error between the first sound speed and the second sound speed is out of a preset error tolerance range. A flow rate calculation device comprising: a determination unit; Transmitted and received between a measurement tube through which a fluid to be measured flows, first and second ultrasonic transmitters and receivers arranged on the peripheral surface of the measurement tube, and the first and second ultrasonic transmitters and receivers, A non-full-water state determination method used in an ultrasonic flowmeter comprising a flow rate calculation device that measures the flow rate of the fluid based on the propagation time of the ultrasonic beam propagating in the fluid,
a first speed-of-sound calculation step in which the flow rate calculator calculates a first speed of sound with respect to the ultrasonic beam based on the fluid temperature of the fluid;
a second speed-of-sound calculation step in which the flow rate calculator calculates a second speed of sound for the ultrasonic beam based on the propagation time of the ultrasonic beam and a reference beam path length of a normal beam path;
When the flow rate calculation device detects that at least the sound velocity error between the first sound velocity and the second sound velocity is out of a preset error tolerance range, the liquid level of the fluid is not full. A non-full state determination method, comprising: a non-full state determination step of determining

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