JP2020106358A - Ultrasonic flowmeter, flow rate computing device, and non-full-water state determining method - Google Patents

Abstract

To appropriately determine a non-full-water state even when a beam path length of an ultrasonic beam has changed.SOLUTION: A first sound velocity calculation unit 14B calculates a first sound velocity C1 relating to an ultrasonic beam B on the basis of a fluid temperature T of fluid, a second sound velocity calculation unit 14C calculates a second sound velocity C2 relating to the ultrasonic beam B on the basis of propagation times t1, t2 of the ultrasonic beam B and a reference beam path length Ls of a normal beam path, and a non-full-water state determination unit 14D determines that a liquid level of the fluid is in a non-full-water state when at least a sound velocity error ΔC between the first sound velocity C1 and the second sound velocity C2 is out of range of a preset error permissible range E.SELECTED DRAWING: Figure 1

Description

The present invention relates to an ultrasonic flow meter, and more particularly to a non-fullness determining technique for determining that the inside of a measuring pipe is in a non-full state.

Generally, in flow rate measurement using ultrasonic waves, it is premised that the inside of the measuring tube is filled with fluid and the ultrasonic beam propagates along a beam path assumed in advance in the fluid. Therefore, when the inside of the measuring pipe is not filled with fluid and is in a non-full state, not only the correct fluid velocity cannot be measured but also the calculation of the fluid volume based on the cross-sectional area of the measuring pipe becomes inaccurate. It causes an error in measurement.

Conventionally, as a technique for determining such a non-full state, a technique for comparing the received signal strength of ultrasonic waves with a preset threshold value and determining the non-full state based on the obtained comparison result is proposed. (For example, see Patent Documents 1-2).

JP, 2005-184173, A JP, 2017-116458, A JP, 2013-178125, A

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

When the above-mentioned conventional non-full water determination technology is applied to the ultrasonic flowmeter having such a configuration, the ultrasonic beam may be reflected by the liquid surface depending on the height of the liquid surface in the measuring pipe. , There may be cases where the beam is received on a beam path different from the assumed beam path. In such a case, the received signal strength of the ultrasonic beam increases/decreases as the beam path length shortens/extends, resulting in an erroneous determination result indicating that the ultrasonic beam is full although it is not full. There was a problem. For this reason, not only the correct fluid flow velocity cannot be measured, but also the calculation of the fluid volume based on the cross-sectional area of the measuring pipe becomes inaccurate, which causes an error in the flow rate measurement.

The present invention is for solving such a problem, and an object thereof is to provide a non-full state determination technique capable of appropriately determining the non-full state even when the beam path length of the ultrasonic beam is changed. ..

In order to achieve such an object, an ultrasonic flowmeter according to the present invention includes a measuring pipe through which a fluid to be measured flows and first and second ultrasonic transmitting/receiving devices arranged on the peripheral surface of the measuring pipe. And a flow rate calculating device that measures the flow rate of the fluid based on the propagation time of the ultrasonic beam propagating in the fluid, which is transmitted and received between the first and second ultrasonic transceivers. An acoustic wave flowmeter, wherein the flow rate calculation device calculates a first acoustic velocity for the ultrasonic beam based on a fluid temperature of the fluid, a first acoustic velocity calculation unit, and a propagation time of the ultrasonic beam. A second sound velocity calculation unit that calculates a second sound velocity relating to the ultrasonic beam based on a reference beam path length of a regular beam path, and at least a sound velocity between the first sound velocity and the second sound velocity. When the error is outside the preset error allowable range, the liquid level of the fluid is provided with a non-full state determination unit that determines that the liquid level is not full.

Further, in one configuration example of the ultrasonic flowmeter according to the present invention, when the sound velocity error is within the error allowable range, the reception intensity of the ultrasonic beam is preset in the non-full state determination unit. The liquid level of the fluid is determined to be a full state or a non-full state depending on whether or not it is equal to or more than the strength threshold value.

In the configuration example of the ultrasonic flowmeter according to the present invention, the allowable error range is a range between the lower limit threshold and the upper limit threshold.

In addition, in one configuration example of the ultrasonic flowmeter according to the present invention, the allowable error range is a range equal to or larger than an arbitrary threshold value or equal to or smaller than an arbitrary threshold value.

Further, in one configuration example of the ultrasonic flowmeter according to the present invention, the non-full state determination unit, the sonic velocity error determination result indicating that the sonic velocity error is within the error allowable range, the ultrasonic wave The non-full state is determined based on the logical product with the signal intensity determination result indicating that the beam reception intensity is equal to or higher than the intensity 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 at least on the inner wall surface of the measurement tube. It has two reflection points.

Further, in one configuration example of the ultrasonic flowmeter according to the present invention, the trajectory of the beam path projected on a plane orthogonal to the tube axis of the measurement tube has a substantially triangular shape.

Further, the flow rate calculation device according to the present invention is an ultrasonic flowmeter including a measurement pipe through which a fluid to be measured flows and first and second ultrasonic transceivers arranged on the peripheral surface of the measurement pipe. A flow rate calculation device used for measuring the flow rate of the fluid based on a propagation time of an ultrasonic beam propagating in the fluid, which is transmitted and received between the first and second ultrasonic transceivers. A first sound velocity calculator for calculating a first sound velocity relating to the ultrasonic beam based on a fluid temperature of the fluid; and a propagation time of the ultrasonic beam and a reference beam path length of a regular beam path. And a second sound velocity calculation unit that calculates a second sound velocity relating to the ultrasonic beam, and at least an error allowable range in which a sound velocity error between the first sound velocity and the second sound velocity is preset. When it is outside, the liquid level of the fluid is provided with a non-full state determination unit that determines that the liquid level is a non-full state.

In addition, the non-full state determination method according to the present invention includes a measurement tube through which a fluid to be measured flows, first and second ultrasonic transceivers arranged on a peripheral surface of the measurement tube, and the first and second ultrasonic transducers. A flow rate calculation device for measuring the flow rate of the fluid based on the propagation time of the ultrasound beam propagating in the fluid, which is transmitted and received between the second ultrasound transceivers. A method for determining a full water state, wherein the flow rate calculation device calculates a first sound velocity of the ultrasonic beam based on a fluid temperature of the fluid, and the flow rate calculation device includes: A second sound velocity calculating step of calculating a second sound velocity relating to the ultrasonic beam based on a propagation time of the ultrasonic beam and a reference beam path length of a regular beam path; A non-full state determination step of determining that the liquid level of the fluid is a non-full state when the sonic velocity error between the first sonic velocity and the second sonic velocity is out of a preset error tolerance range; Equipped with.

According to the present invention, it is possible to appropriately determine the non-full state even when the beam path length of the ultrasonic beam changes. Therefore, by notifying the host device of the non-full state together with the measured flow rate of the fluid, not only the host device can determine that the flow rate contains an error, but also notify the occurrence of the non-full state as an alarm. You can

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

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

FIG. 2 is an explanatory diagram showing the beam path (full state). FIG. 3 is an explanatory diagram showing the beam path (non-full state). This ultrasonic flowmeter 1 has a measuring tube P having a hexagonal cross-sectional shape, and the ultrasonic beam B is reflected by the inner wall surface of the measuring tube P to extend the beam path length (for example, a 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 and then by the inner wall surface PB for ultrasonic transmission/reception. It is received by the unit UB. The ultrasonic beam B in the reverse direction transmitted from the ultrasonic transmitter/receiver UB is reflected by the inner wall surface PB in the opposite direction to the forward direction, is then reflected by the inner wall surface PA, and is received by the ultrasonic transmitter/receiver UA. ..

On the other hand, in the non-full state, depending on the liquid level, the forward ultrasonic beam B transmitted from the ultrasonic transmitter/receiver UA is first reflected by the inner wall surface PA, as shown in FIG. The liquid may be reflected by the liquid surface F1 and then again by the inner wall surface PA, then reflected by the liquid surface F2, and received by the ultrasonic transmitter/receiver UB. At this time, since the beam path length Lx is different from the reference beam path length Ls of the beam path assumed in advance in a full state as shown in FIG. 2, the received signal strength of the ultrasonic beam B is increased/decreased. .. Therefore, as in the prior art, when the non-full state is determined by comparing the received signal intensity with a preset intensity threshold value, the full state is present despite the non-full state. Will result in an incorrect determination.

[Principle of the present invention]
An ultrasonic wave is defined as a sound wave having a high frequency that cannot be heard by the human ear, and is generally considered to be a sound wave of 20 kHz or higher. Such ultrasonic waves have the same properties as audible sounds that can be heard by the human ear. One of them is that the speed of sound propagating through a material is It is determined by

The first sound velocity C1 relating to sound propagating in water is obtained 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 of the equation (2). Therefore, as shown in FIG. 3, when the beam path length Lx is different from the reference beam path length Ls due to the non-full state, the beam path length L of the equation (2) remains the reference beam path length Ls. However, the propagation times t1 and t2 change. Therefore, the sound velocity error ΔC (=C2-C1) between the second sound velocity C2 obtained by the equation (2) and the first sound velocity C1 obtained by the equation (1) becomes large.

The present invention focuses on the relationship between the change in the beam path length L due to such a non-full state and the sound velocity error ΔC, obtains the first sound velocity C1 from the fluid temperature T, and measures the assumed reference beam path length Ls. The second sound velocity C2 is obtained from the propagation times t1 and t2, and the non-full state is determined by thresholding the sound velocity error ΔC between the two.

Next, the configuration of the ultrasonic flowmeter 1 according to the present embodiment will be described in detail with reference to FIG.
As shown in FIG. 1, the ultrasonic flowmeter 1 is arranged on a measurement pipe P through which a fluid to be measured flows and upstream and downstream of the circumferential surface of the measurement pipe P with respect to the direction in which the fluid flows. A pair of ultrasonic transmitter/receivers (transducers) UA and UB, and a flow rate calculation device 10 for signal-processing the received waves of the ultrasonic beam B transmitted/received between these 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 upstream UA through which the fluid flows to the downstream UB through which the fluid flows is called the forward direction, and from the downstream UB to the upstream UA. 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 has an inclination with respect to the tube axis O of the measuring tube P as shown in FIG. 1, and as shown in FIGS. 2 and 3. An example will be described in which the inner wall surface of the measurement pipe P has at least two reflection points (PA, PB) and the locus projected on the plane orthogonal to the pipe axis O of the measurement pipe P has a substantially triangular shape. The beam path is not limited to this. For example, if the ultrasonic beam B intersects the liquid surface of the fluid when the liquid level of the fluid drops from the full state, the beam path can be similarly applied to any beam path.

As shown in FIG. 1, the flow rate calculation device 10 includes an input/output I/F circuit 11, a storage circuit 12, a higher I/F circuit 13, and a calculation processing circuit 14 as main circuit units. These circuit units are connected via an internal bus BUS so that data can be exchanged.

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

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

The upper 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 state to a higher-level 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 memory circuit 12 and executes it on the CPU, and uses it in cooperation with hardware and software to perform flow rate measurement processing and non-full-water state determination processing. It is a circuit unit that realizes various processing units.
The main processing units implemented by the arithmetic processing circuit 14 include a measurement unit 14A, a first sound velocity calculation unit 14B, a second sound velocity calculation unit 14C, a non-full state determination unit 14D, and a flow rate calculation unit 14E.

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

The first sound velocity calculation unit 14B has a function of calculating the first sound velocity C1 based on the fluid temperature T acquired from the storage circuit 12 by using, for example, the above-described formula (1).
The second sound velocity calculation unit 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 set in the storage circuit 12 in advance. Thus, it has a function of calculating the second sound velocity C2.

The non-full state determination unit 14D calculates the sound velocity error ΔC between the first sound velocity C1 and the second sound velocity C2, and obtains the obtained sound velocity error ΔC and the error tolerance range E preset in the storage circuit 12. And a function of comparing and a function of determining that the liquid level H of the fluid is a non-full state and storing it in the storage circuit 12 when at least the sound velocity error ΔC is outside the preset error allowable range E. have.

Further, 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 with an intensity threshold value Sth preset in the storage circuit 12, and the sound velocity error ΔC is within an allowable error range. If it is within the range of E, it is determined whether the liquid level of the fluid is full or non-full depending on whether or not the ultrasonic reception intensity S is equal to or more than the intensity threshold value Sth and stored in the storage circuit 12. It has the function to

The flow rate calculation unit 14E flows in the measurement 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 in the measuring pipe P is obtained by the product of the flow velocity V and the cross-sectional area A of the measuring pipe P. Further, the flow velocity V is obtained by the following formula (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 fluid flowing direction.

[Operation of this Embodiment]
Next, the operation of the ultrasonic flowmeter 1 according to the present embodiment will be described with reference to FIG. FIG. 4 is a flowchart showing the non-full state determination process.
The arithmetic processing circuit 14 executes the non-full state determination process of FIG. 4 every time the measurement unit 14A obtains new propagation times t1 and t2 and the fluid temperature T.

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

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

In step S104, when the ultrasonic wave reception intensity S is equal to or higher than the intensity threshold value Sth (step S104: YES), the non-full state determination unit 14D determines that the measuring pipe P is in the full state, and the storage circuit 12 stores it. The data is saved (step S105), and a series of non-full state determination processing ends.

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

In FIG. 4, the execution processing order of step S103 and step 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 logical product of the obtained comparison results. As a specific example, as shown in FIG. 6 described later, the sound velocity error determination result Rc indicating that the sound velocity error ΔC is within the error allowable range E and the ultrasonic wave reception intensity S of the ultrasonic beam B are stronger. The non-full state may be determined based on the logical product with the signal strength determination result Rs indicating that the threshold value Sth or more.

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

As the liquid level H decreases from the full state, the ultrasonic beam B is reflected on the liquid surface of the fluid, and the ultrasonic transceivers UA and UB are exposed to the air. Therefore, the beam path of the ultrasonic beam B is disturbed and the strength of the transmitted ultrasonic signal is reduced. As shown in FIG. 5, when the ultrasonic wave reception intensity S falls below the intensity threshold value Sth at time T1, the signal intensity determination result Rs changes from the H (High) level to the L (Low) level. The signal strength determination result Rs is a logical value inside the non-full state determination unit 14D, which indicates an H level when S≧Sth and an L level when S<Sth.

After that, at the subsequent time Ts1, when the ultrasonic beam B happens to be received on the fluid surfaces F1 and F2 as shown in FIG. 3, for example, the ultrasonic reception intensity S is temporarily reduced to the intensity threshold Sth. Rise to higher levels. 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 and indicates the H level indicating the full state in the period Ws. .. The non-full state determination result Rm is a logical value inside the non-full state determination unit 14D that indicates the H level when the full state and the L level when the non full state.

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

When the beam path of the ultrasonic beam B is disturbed or the strength of the transmitted ultrasonic signal is decreased due to the decrease in the liquid level H, the beam path length L is changed and the propagation times t1 and t2 are changed. .. Therefore, the second sound velocity C2 obtained by the above-mentioned equation (2) changes, and the sound velocity error ΔC changes. Specifically, when the beam path length L is extended, the propagation times t1 and t2 are increased, C2 is decreased, and ΔC is decreased. 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 intensity S falls below the intensity threshold value Sth at time T1, the signal intensity determination result Rs changes from the H level to the L level. After that, when the sound velocity error ΔC falls below the lower limit threshold value EL at time T2, the sound velocity 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. The logic inside the non-full state determination unit 14D It is a value.

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

Therefore, when the non-full state is determined based on the logical product of the signal strength determination result Rs and the sound velocity error determination result Rc, the non-full state determination result Rm is before the time T1 when both Rs and Rc are at the H level. The H level indicating a full state is shown only in the period of, and like the actual liquid level H, even if one of Rs and Rc such as the period Ws and the period Wc becomes the H level after that, It will indicate an L level indicating a non-full state.

In the above description, the error allowable range E is described as an example in which it is defined by a band-shaped range composed of the lower limit threshold EL and the upper limit threshold EH, but the present invention is not limited to this. The beam path of the ultrasonic beam B of the ultrasonic flow meter 1 is determined by the arrangement of the ultrasonic transmitters/receivers UA and UB, the arrangement of the inner wall surface of the measuring tube P, and the liquid level H. For this reason, depending on the beam path, there may be a case where the condition that a period Ws in which the ultrasonic reception intensity S exceeds the intensity threshold Sth and a period in which the sound velocity error ΔC falls below the lower limit threshold EL occur are fixed. ..

For example, as shown in FIG. 6, when the period Ws occurs only in the period when the sound velocity error ΔC is below the lower limit threshold value EL, the upper limit threshold value 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 the arbitrary threshold value Eth. On the contrary, when the period Ws occurs only in the period in which the sound velocity error ΔC exceeds the upper limit threshold value EH, the lower limit threshold value EL 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 less than the arbitrary threshold value Eth.

[Effects of this Embodiment]
As described above, in the present embodiment, the first sound speed calculation unit 14B calculates the first sound speed C1 regarding the ultrasonic beam B based on the fluid temperature T of the fluid, and the second sound speed calculation unit 14C calculates the first sound speed C1. , The second sound velocity C2 relating to the ultrasonic beam B is calculated 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, and the non-full state determination unit 14D at least , If the sound velocity error ΔC between the first sound velocity C1 and the second sound velocity C2 is outside the preset error tolerance range E, it is determined that the fluid level is in a non-full state. It is a thing.

Further, more specifically, when the sound velocity error ΔC is within the error allowable range E, the non-full state determination unit 14D determines that the ultrasonic reception intensity S of the ultrasonic beam B is a preset intensity threshold. The liquid level of the fluid is determined whether it is a full state or a non-full state depending on whether or not the value is Sth or more.
Accordingly, even when the beam path length L of the ultrasonic beam B changes, it is possible to appropriately determine the non-full state. Therefore, if the upper-level device is notified of the non-full state together with the measured flow rate Q of the fluid, not only the upper-level device can determine that the flow rate Q includes an error, but also informs that a non-full state occurs as an alarm. can do.

[Expansion of Embodiment]
Although the present invention has been described with reference to the exemplary embodiments, the present invention is not limited to the above exemplary 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 rate calculation device, 11... Input/output I/F circuit, 12... Storage circuit, 13... Upper I/F circuit, 14... Arithmetic processing circuit, 14A... Measuring part, 14B... 1st Sound velocity calculation unit, 14C... second sound velocity calculation unit, 14D... non-full state determination unit, 14E... flow rate calculation unit, P... measurement pipe, PA, PB, PC... inner wall surface, UA... ultrasonic transmitter/receiver (No. 1 ultrasonic wave transceiver), UB... Ultrasonic wave transceiver (second ultrasonic wave transceiver), 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 velocity, C2... Second sound velocity, ΔC... Sound velocity error, E... Error tolerance range, EL... Lower threshold value, EH... Upper threshold value, S ... ultrasonic wave reception 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)

A measurement tube through which a fluid to be measured flows, first and second ultrasonic transceivers arranged on the peripheral surface of the measurement tube, and transmission and reception between the first and second ultrasonic transceivers, An ultrasonic flow meter comprising: a flow rate calculating device for measuring a flow rate of the fluid based on a propagation time of an ultrasonic beam propagating in the fluid,
The flow rate calculation device,
A first sound velocity calculator that calculates a first sound velocity for the ultrasonic beam based on a fluid temperature of the fluid;
A second sound velocity calculator that calculates a second sound velocity for the ultrasonic beam based on a propagation time of the ultrasonic beam and a reference beam path length of a regular beam path;
At least when 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 determined to be a non-full state An ultrasonic flowmeter, comprising: a determination unit. The ultrasonic flowmeter according to claim 1,
The non-full state determination unit, when the sound velocity error is within the error tolerance range, depending on whether the reception intensity of the ultrasonic beam is equal to or greater than a preset intensity threshold value, An ultrasonic flowmeter, characterized in that the liquid level of the fluid is judged to be full or non-full. The ultrasonic flowmeter according to claim 1 or 2,
The ultrasonic flowmeter, wherein the allowable error range is a range between a lower limit threshold value and an upper limit threshold value. The ultrasonic flowmeter according to claim 1 or 2,
The ultrasonic flowmeter, wherein the allowable error range is a range that is greater than or equal to an arbitrary threshold value and less than or equal to an arbitrary threshold value. The ultrasonic flowmeter according to claim 2,
The non-full state determination unit, the 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, characterized in that it is judged that it is in a non-full state based on a logical product with a strength judgment result. The ultrasonic flowmeter according to any one of claims 1 to 5,
An ultrasonic flowmeter, wherein a beam path of the ultrasonic beam has an inclination with respect to a tube axis of the measuring tube and has at least two reflection points on an inner wall surface of the measuring tube. The ultrasonic flowmeter according to claim 6,
The ultrasonic flowmeter, wherein the beam path has a substantially triangular locus projected on a plane orthogonal to the tube axis of the measuring tube. It is used in an ultrasonic flowmeter provided with a measurement pipe through which a fluid to be measured flows and first and second ultrasonic transceivers arranged on the peripheral surface of the measurement pipe, and the first and second ultrasonic flowmeters are provided. A flow rate calculation device for measuring a flow rate of the fluid, which is transmitted and received between ultrasonic transmitters and receivers, based on a propagation time of an ultrasonic beam propagating in the fluid,
A first sound velocity calculator that calculates a first sound velocity for the ultrasonic beam based on a fluid temperature of the fluid;
A second sound velocity calculator that calculates a second sound velocity for the ultrasonic beam based on a propagation time of the ultrasonic beam and a reference beam path length of a regular beam path;
At least when 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 determined to be a non-full state A flow rate calculation device comprising: a determination unit. A measurement tube through which a fluid to be measured flows, first and second ultrasonic transceivers arranged on the peripheral surface of the measurement tube, and transmission and reception between the first and second ultrasonic transceivers, Based on the propagation time of the ultrasonic beam propagating in the fluid, a non-full state determination method used in an ultrasonic flow meter comprising a flow rate calculation device for measuring the flow rate of the fluid,
A first sound velocity calculation step in which the flow rate calculation device calculates a first sound velocity relating to the ultrasonic beam based on a fluid temperature of the fluid;
A second sound velocity calculation step in which the flow rate calculation device calculates a second sound velocity relating to the ultrasonic beam based on a propagation time of the ultrasonic beam and a reference beam path length of a regular beam path;
The liquid level of the fluid is in a non-full state when at least the sound velocity error between the first sound velocity and the second sound velocity is outside the preset error tolerance range in the flow rate calculation device. A non-full state determination method comprising: a non-full state determination step.