JP6652840B2 - Ultrasonic flow meter - Google Patents

Description

  The present invention relates to an ultrasonic flowmeter, and more particularly to a technique for determining soundness of flow accuracy.

An ultrasonic flowmeter that measures a flow rate using ultrasonic waves is known. The measuring method in the ultrasonic flow meter is roughly divided into two methods, a zero cross method and a correlation method. FIG. 15 is a cross-sectional view illustrating the measurement principle of the ultrasonic flowmeter. V is the flow velocity of the fluid 2 flowing through the pipe 1, L is the propagation distance between the ultrasonic sensors 3 and 4 provided in the pipe 1, and the line connecting the ultrasonic sensors 3 and 4 is the pipe axis. Assuming that the angle formed with 5 is θ and the sound velocity is C, the propagation time t _{1 of the} ultrasonic wave in the forward direction (the direction in which the fluid 2 flows) from the ultrasonic sensor 3 to the ultrasonic sensor 4, and the ultrasonic sensor 4 The propagation time t _{2 of the} ultrasonic wave in the reverse direction up to 3 can be expressed by the following equation.
t ₁ = L / (C + Vcos θ) (1)
t ₂ = L / (C−Vcos θ) (2)

In the zero-cross method, the ultrasonic signals are transmitted from the ultrasonic sensors 3 and 4 to measure the propagation times t ₁ and t ₂ , and the flow velocity V and the flow rate Q of the fluid 2 are calculated as follows ( Patent Document 1).
V = (t ₁ −t ₂ ) L / (2t ₁ t ₂ ) (3)
Q = SV / k (4)

In the equation (4), S is a sectional area of the pipe 1, and k is a predetermined flow rate correction coefficient. At the propagation time t ₁ , the first reception pulse of the ultrasonic reception signal _{Su → d} as shown in FIG. 16A received by the ultrasonic sensor 4 rises from the transmission of the ultrasonic signal from the ultrasonic sensor 3. Until the time. Similarly, the propagation time t ₂ is the time from when the ultrasonic sensor 4 sends out the ultrasonic signal to the first reception of the ultrasonic reception signal S _{d → u} as shown in FIG. It is the time until the pulse rises. Actually, since it is difficult to detect the rise time of the first received pulse, the propagation times t ₁ and t ₂ are calculated from the zero cross point, which is the intersection of the received waveform and the x-axis (time axis).

On the other hand, in the correlation method, the propagation time difference Δt between the forward and backward ultrasonic waves is measured, and the flow velocity V and the flow rate Q of the fluid 2 are calculated as follows (see Patent Document 2).
V ≒ C ² Δt / (2Lcosθ) (5)
Q = SV / k ≒ SC ² Δt / ( ² kL cos θ) (6)

The propagation time difference Δt is obtained directly from the received waveform. Specifically, ultrasonic reception signal S _d as shown in FIG. 16 received by the ultrasonic wave reception signal S _{u → d} and the ultrasonic sensor 3 as shown in FIG. 16 received by the ultrasonic sensor 4 (B) (B) _{→ u} is sampled, a cross-correlation operation is performed between the waveform data of the ultrasonic reception signal S _{u → d and} the waveform data of the ultrasonic reception signal S _{d → u} , and a propagation time difference Δt is obtained from the correlation function.

  By the way, in the ultrasonic flow meter, it is known that the ultrasonic reception signal is attenuated when contaminants or the like adhere to the pipe, and that the operation of the ultrasonic flow meter increases the noise derived from the operation. I have. When the unintended noise is superimposed on the measured ultrasonic reception signal, a flow rate error may occur, and in the worst case, a measurement may not be possible. Therefore, detecting noise is very important for correct measurement.

  Therefore, an ultrasonic flowmeter capable of detecting noise that has an adverse effect on measurement has been proposed (see Patent Document 3). The ultrasonic flow meter disclosed in Patent Literature 3 determines the soundness of a received waveform by detecting a characteristic value of the received waveform.

Japanese Patent No. 5346870 JP 2013-088322 A Japanese Patent No. 5649476

  However, in the ultrasonic flow meter disclosed in Patent Literature 3, an appropriate amplification ratio determined by a combination of the actual amplification factor of the amplification unit that amplifies the ultrasonic reception signal, the type of fluid, the temperature of the fluid, and the pressure of the fluid. Comparing with the theoretical amplification factor, if the difference between the theoretical amplification factor and the actual amplification factor is equal to or more than a predetermined value, it is determined that noise has occurred, but it is necessary to obtain the temperature and pressure of the fluid, There is a problem that the configuration of the ultrasonic flowmeter becomes complicated. In addition, it is necessary to create a database in which the theoretical amplification factors corresponding to various combinations of the type of fluid, the temperature of the fluid, and the pressure of the fluid are registered in advance, and there is a problem that it takes time to create the database. .

  The present invention has been made to solve the above problems, and has as its object to provide an ultrasonic flowmeter that can determine the soundness of flow accuracy with a simple configuration.

  The ultrasonic flow meter according to the present invention includes a pipe through which a fluid to be measured flows, a pair of ultrasonic sensors arranged upstream and downstream of the pipe, and the downstream side ultrasonic sensor sent from the upstream ultrasonic sensor. The maximum value of the first ultrasonic reception signal received by the ultrasonic sensor and the maximum value of the second ultrasonic reception signal transmitted from the ultrasonic sensor on the downstream side and received by the ultrasonic sensor on the upstream side An intensity difference calculating means for calculating an absolute value of a difference between the first and second ultrasonic reception signals and an absolute value of a difference between the minimum value of the second ultrasonic reception signal and the minimum value of the second ultrasonic reception signal; A multiplication value calculating means for calculating a multiplication value of a propagation time difference between the sound wave reception signal and the second ultrasonic reception signal and an absolute value of the intensity difference calculated by the intensity difference calculation means; If the multiplied value is larger than the specified allowable difference, an alarm is output. It is characterized in further comprising a comparing means that.

Further, the ultrasonic flowmeter of the present invention comprises a pipe through which a fluid to be measured flows, a pair of ultrasonic sensors arranged upstream and downstream of the pipe, and a downstream side sent from the upstream ultrasonic sensor. The amplitude of the first ultrasonic reception signal received by the ultrasonic sensor and the amplitude of the second ultrasonic reception signal transmitted from the ultrasonic sensor on the downstream side and received by the ultrasonic sensor on the upstream side Amplitude difference calculating means for calculating the absolute value of the difference, the propagation time difference between the first ultrasonic reception signal and the second ultrasonic reception signal, and the absolute value of the amplitude difference calculated by the amplitude difference calculation means And a comparing means for outputting an alarm when the multiplied value calculated by the multiplied value calculating means is larger than a predetermined allowable amplitude difference. .
Additionally, in an example of an ultrasonic flowmeter of the present invention, the multiplication value calculating means, the Propagation from the correlation function of the waveform data cross the first ultrasonic reception signal and the second ultrasonic receiving signal It is characterized in that a time difference is obtained.

  According to the present invention, by providing the intensity difference calculation means, the multiplication value calculation means, and the comparison means, the soundness of the flow accuracy of the ultrasonic flowmeter can be determined with a simple configuration.

  Further, in the present invention, by providing the amplitude difference calculating means, the multiplication value calculating means, and the comparing means, the soundness of the flow rate accuracy of the ultrasonic flowmeter can be determined with a simple configuration.

FIG. 3 is a cross-sectional view illustrating a state where noise is not superimposed on an ultrasonic reception signal. FIG. 4 is a diagram illustrating a waveform example of an ultrasonic reception signal when noise is not superimposed. It is a figure explaining signs that an ultrasonic wave reception signal and noise overlap when there is no fluid flow. It is a figure explaining signs that an ultrasonic wave reception signal and noise overlap when there is a flow of fluid. FIG. 7 is a diagram illustrating an example of waveforms of an ultrasonic reception signal and noise for calculating a flow rate error. FIG. 9 is a diagram illustrating a result of calculating a waveform of an ultrasonic reception signal mixed with noise. It is the figure which expanded a part of waveform of FIG. It is the figure which expanded a part of waveform of FIG. FIG. 8 is a diagram illustrating a result of calculating a relationship between a noise phase, a flow rate error, and an intensity difference between ultrasonic reception signals. FIG. 8 is a diagram illustrating a result of calculating a relationship between a noise phase, a flow rate error, and an intensity difference between ultrasonic reception signals. FIG. 1 is a block diagram illustrating a configuration of an ultrasonic flowmeter according to a first embodiment of the present invention. 5 is a flowchart illustrating a flow rate accuracy soundness determination process in the ultrasonic flowmeter according to the first embodiment of the present invention. It is a block diagram showing the composition of the ultrasonic flow meter concerning a 2nd embodiment of the present invention. It is a flowchart explaining the soundness determination processing of the flow rate accuracy in the ultrasonic flowmeter according to the second embodiment of the present invention. It is sectional drawing explaining the measurement principle of an ultrasonic flowmeter. FIG. 3 is a diagram illustrating a method of determining a propagation time according to a zero-cross method, and a diagram illustrating a method of determining a propagation time difference according to a correlation method.

[Principle of the invention]
The inventor paid attention to the difference in the intensity of the upstream-to-downstream, downstream-to-upstream ultrasonic reception signals measured by the ultrasonic flowmeter. This makes it possible to more easily detect noise that has an adverse effect on measurement than the ultrasonic flow meter disclosed in Patent Document 3.
1A and 1B are diagrams illustrating the principle of the present invention, and are cross-sectional views illustrating a state in which noise is not superimposed on an ultrasonic reception signal. 1A is a cross-sectional view of the pipe 1, and FIG. 1B is a vertical cross-sectional view of the pipe 1 of FIG.

  In the present invention, since the pair of ultrasonic sensors 3 and 4 are arranged at locations where the positions on the circumference of the circular cross section of the pipe 1 are the same and the positions in the direction in which the fluid 2 flows are different, The propagation path of the transmission and reception of the sound wave is a V-shaped propagation path reflected on the inner wall of the pipe 1 as shown in FIG. That is, the upstream ultrasonic sensor 3 transmits an ultrasonic signal toward the inner wall of the pipe 1 on the opposite side via the fluid 2, and at the same time, the downstream ultrasonic sensor 4 transmits the ultrasonic signal via the fluid 2. An ultrasonic signal is transmitted toward the inner wall of the pipe 1 on the side to be cleaned. The angle between the direction in which the ultrasonic sensor 3 sends out the ultrasonic signal and the inner wall of the pipe 1 and the angle between the direction in which the ultrasonic sensor 4 sends out the ultrasonic signal and the inner wall of the pipe 1 are θ. is there.

The ultrasonic reception signal S _{u → d} transmitted from the ultrasonic sensor 3 and received by the ultrasonic sensor 4 and the ultrasonic reception signal S _{d → u} transmitted from the ultrasonic sensor 4 and received by the ultrasonic sensor 3 are the fluid 2 Is output with a phase difference (time difference) proportional to the flow velocity V (the zero-cross point which is the intersection with the time axis and the received waveform also has a time difference).

For example, when the flow velocity V is 0 [m / s], the time difference between the ultrasonic reception signal S _{u → d} and the ultrasonic reception signal S _{d → u} is 0 [ns], and the phase difference is 0 [rad] ( FIG. 2 (A)). When the flow velocity V is 0.3 [m / s], the time difference is 15 [ns] and the phase difference is 0.12 [rad] (FIG. 2B). When the flow velocity V is 3 [m / s], the time difference is 150 [ns], and the phase difference is 1.22 [rad] (FIG. 2C). When the flow velocity V is 6 [m / s], the time difference is 300 [ns] and the phase difference is 2.45 [rad] (FIG. 2 (D)).

On the other hand, when transmitting and receiving ultrasonic waves, unintended noise of the same frequency (for example, noise transmitted through the pipe 1) may be mixed from a place different from the normal path. When such noise is mixed, a waveform in which the ultrasonic reception signals S _{u → d} and S _{d → u} and the noise are superimposed is observed. FIG. 3A is a diagram for explaining how the noise N having a phase of 0 ° is superimposed on the ultrasonic reception signals S _{u → d} and S _{d → u} when there is no fluid flow, and FIG. FIG. 8 is a diagram illustrating a state in which noise N having a phase of 180 ° is superimposed on the ultrasonic reception signals S _{u → d} and S _{d → u} when there is no fluid flow.

In the example of FIGS. 3A and 3B, the phase of the noise N is not affected by the water temperature or the like (it always appears at the same place), and the noise N is the frequency of the ultrasonic wave (eg, 1.3 MHz). It is assumed that the frequency is about the same as. In the present invention, the phase of the ultrasonic reception signals S _{u → d} and S _{d → u} when there is no fluid flow is set as a reference (0 °), and the phase of the noise N is defined with respect to this phase. .

Ultrasonic wave reception signal S _{u → d,} the noise N is superimposed on S d _{→ u,} ultrasonic reception signal S _{u → d,} but the strength of the S d _{→ u} changes, above as the flow velocity V is 0 [m / In the state of [s], since the time difference between the ultrasonic reception signal S _{u → d} and the ultrasonic reception signal S _{d → u} is 0 [ns], the intensity of the ultrasonic reception signal S _{u → d} and the ultrasonic reception signal S _{d → u} Similarly changes, and there is no difference in intensity. That is, the propagation time difference Δt calculated by the correlation method is 0, the propagation times t ₁ and t ₂ calculated by the zero-cross method become equal, and no flow rate error occurs.

However, when there is a flow of fluid, there is a difference (time difference) between the ultrasonic reception signals S _{u → d} and the ultrasonic reception signals S _{d → u} as shown in FIGS. 2 (A) to 2 (D). . FIG. 4A is a view for explaining a state in which noise N having a phase of 0 ° is superimposed on the ultrasonic reception signals S _{u → d} and S _{d → u} when there is a fluid flow, and FIG. FIG. 11 is a diagram illustrating a state in which noise N having a phase of 180 ° is superimposed on the ultrasonic reception signals S _{u → d} and S _{d → u} when there is a flow of a fluid. 4A and 4B, the phase of the noise N is not affected by the water temperature or the like, and the noise N is substantially equal to the frequency of the ultrasonic wave (eg, 1.3 MHz). Assume frequency.

When there is a flow of the fluid, the ultrasonic reception signal S _{u → d} from the ultrasonic sensor 3 to the ultrasonic sensor 4 (upstream → downstream) and the ultrasonic wave from the ultrasonic sensor 4 to the ultrasonic sensor 3 (downstream → upstream) Since the arrival position of the reception signal S _{d → u} changes, the noise N is added to the ultrasonic reception signals S _{u → d} and S _{d → u at} different phases. Therefore, shows the change in amplitude Y _{d → u} amplitude Y _{u → d} and ultrasonic reception signal S _{d → u} ultrasonic reception signals S _{u → d} are different, a difference in signal strength occurs. That is, an error occurs between the propagation time difference Δt calculated by the correlation method and the propagation times t ₁ and t ₂ calculated by the zero-cross method.

Next, a flow rate error due to a phase difference between the ultrasonic reception signal and noise is calculated. Here, the same frequency noise N (phase is 0) as shown in FIG. 5B is added to the ultrasonic reception signals S _{u → d} and S _{d → u} having a frequency of 1.3 MHz as shown in FIG. (° to 359 °), the signal intensity difference and the flow rate error were calculated. Specifically, the change in the zero-cross point of the ultrasonic reception signals S _{u → d} and S _{d → u} due to the noise N was calculated. The phases of N ₀ , N ₉₀ , N ₁₈₀ , and N ₂₇₀ in FIG. 5B are 0 °, 90 °, 180 °, and 270 ° with respect to the ultrasonic reception signals _{Su → d} and _{Sd → u} , respectively. The waveform of the shifted noise N is shown.

When the noise N is not mixed, the ultrasonic reception signals S _{u → d} and S _{d → u} are as _follows : when the noise N is not mixed, the amplitude of the ultrasonic signal is A _S ; the frequency of the ultrasonic signal is f [Hz]; Is represented by ω [rad / s], and the propagation time difference between the ultrasonic signals in the forward direction and the reverse direction is represented by Δt [ns], which can be expressed as Expressions (7) and (8). As is well known, the angular velocity ω is equal to 2πf.
_{S u → d = A S sinωt} ··· (7)
_{S d → u = A S sin} (ωt + Δt) ··· (8)

Also, the ultrasonic reception signals S _{u → d} and S _{d → u} when the noise N is mixed are expressed by the following equation (9), where A _{N is} the amplitude of the noise N and φ is the phase difference of the noise N. It can be expressed as in equation (10).
_{S u → d = A S sinωt} + A N sin (ωt + φ) ··· (9)
_{S d → u = A S sin} (ω (t + Δt)) + A N sin (ωt + φ) ··· (10)

FIG. 6 is a view showing the results of calculating the waveforms of the ultrasonic reception signals S _{u → d} and S _{d → u} mixed with the noise N based on the equations (9) and (10), and FIG. FIG. 8 is an enlarged view of a portion 61 in FIG. 7 and 8, _{Su → d0} , _{Su → d90} , _{Su → d180} , and _{Su → d270} have phases of 0 °, 90 °, 180 °, and 270 ° in the ultrasonic reception signal _{Su → d} , respectively. shows the waveform when the noise N is _{mixed, S d → u0, S d} → u90, S d → u180, S d → u270 each phase 0 ° to the ultrasonic reception signal _{S d → u, 90 °,} 180 ° , 270 ° when noise N is mixed.

According to FIGS. 7-8, an ultrasonic reception signal S _{u → d,} S _{d →} the noise N phase difference with is applied to the _u, ultrasonic reception signal S _{u → d,} the displacement of S d _{→ u} It can be seen that the intensity of the ultrasonic reception signals S _{u → d} and S _{d → u} has a large difference. As described above, an error occurs due to the difference in intensity.

9 and 10 show the results of calculating the relationship between the phase of the noise N, the flow rate error, and the intensity difference between the ultrasonic reception signals S _{u → d} and S _{d → u} . Here, the flow rate Q with and without the noise N is calculated using the correlation method to determine the flow rate error. FIG. 9 shows the result when the propagation time difference Δt is 80 [ns], the maximum value of the signal intensity when noise N is not mixed is 25000, and the maximum value of the noise N intensity is 500. FIG. Is 40 [ns], the maximum value of the signal intensity when the noise N is not mixed is 25000, and the maximum value of the intensity of the noise N is 500. In FIG. The intensity difference is shown.

From the calculation results shown in FIG. 9 and FIG. 10, the magnitude of the noise N and the intensity difference V ′ between the ultrasonic reception signals S _{u → d} and S _{d → u} are almost proportional to each other. It can be seen that the errors are also approximately proportional. Further, the propagation time difference Δt, the intensity difference V ′, and the flow rate error E also have a proportional relationship as in the following equation.
E [%] ∝Δt × | V ′ | (11)

If the maximum value of the intensity of the ultrasonic reception signal S _{u → d} is Y _{Maxu → d} and the maximum value of the intensity of the ultrasonic reception signal S _{d → u} is Y _{Maxd → u} , the difference between these maximum values is obtained. The absolute value of the intensity difference V ′ is as shown in Expression (12).
| V '| = | Y _{Maxu → d} −Y _{Maxd → u} | (12)

If the minimum value of the intensity of the ultrasonic reception signal S _{u → d} is Y _{MINu → d} and the minimum value of the intensity of the ultrasonic reception signal S _{d → u} is Y _{MINd → u} , the difference between these minimum values is obtained. The absolute value of the intensity difference V ′ is as shown in Expression (13).
| V '| = | Y _{MINu → d} −Y _{MINd → u} | (13)

According to equation (11), it can be seen that the flow rate error E can be estimated by observing the intensity difference V ′ between the ultrasonic reception signals S _{u → d} and S _{d → u} . Therefore, when it is suspected that the flow rate error E is large due to the influence of noise, it is possible to issue an alarm and maintain the soundness of the ultrasonic flow meter.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 11 is a block diagram showing the configuration of the ultrasonic flowmeter according to the first embodiment of the present invention. The ultrasonic flowmeter according to the present embodiment includes a pipe 1 through which a fluid 2 (a liquid such as water) to be measured, ultrasonic sensors 3 and 4 attached to the pipe 1, a transmitting unit 6, and a receiving unit 7 , A flow measuring unit 8, a determining unit 9, and an output unit 10. The determination unit 9 includes an intensity difference calculation unit 90, a multiplication value calculation unit 91, and a comparison unit 92.

  The arrangement of the ultrasonic sensors 3 and 4 and the propagation path of the ultrasonic signal are as described with reference to FIGS. 1A and 1B. The transmission unit 6 supplies a transmission pulse for driving to the ultrasonic sensors 3 and 4. Accordingly, the ultrasonic sensors 3 and 4 transmit ultrasonic signals in a diagonal direction to the fluid 2 flowing in the pipe 1 in accordance with the transmission pulse from the transmission unit 6.

The ultrasonic sensor 4 receives a reflected signal of the ultrasonic signal transmitted from the ultrasonic sensor 3, and the ultrasonic sensor 3 receives a reflected signal of the ultrasonic signal transmitted from the ultrasonic sensor 4.
The receiving unit 7 performs processing such as amplification on the ultrasonic reception signals S _{u → d} and S _{d → u} obtained by the ultrasonic sensors 3 and 4, respectively.

The flow measurement unit 8 calculates the flow velocity V and the flow rate Q of the fluid 2 based on the ultrasonic reception signals S _{u → d} and S _{d → u} output from the reception unit 7. As a method of calculating the flow velocity V and the flow rate Q, there are a zero-cross method (for example, see Patent Literature 1) and a correlation method (for example, see Patent Literature 2).

FIG. 12 is a flowchart illustrating a flow rate accuracy soundness determination process in the ultrasonic flowmeter according to the present embodiment.
The intensity difference calculation unit 90 of the determination unit 9 acquires the maximum value Y _{Maxu → d} of the ultrasonic reception signals S _{u → d} output from the reception unit 7 (Step S1 in FIG. 12), and outputs the maximum value Y _{Maxu → d} from the reception unit 7. The maximum value Y _{Maxd → u} of the received ultrasonic reception signals S _{d → u} is obtained (step S2 in FIG. 12), and the absolute value | V ′ | of the intensity difference V ′ is calculated by equation (12) (step S3 in FIG. 12). ).

The multiplication value calculation unit 91 of the determination unit 9 calculates a multiplication value Δt × | V ′ | of the absolute value | V ′ | of the intensity difference V ′ calculated by the intensity difference calculation unit 90 and the propagation time difference Δt (FIG. 12). Step S4). The propagation time difference Δt is obtained by sampling each of the ultrasonic reception signals S _{u → d} and the ultrasonic reception signals S _{d → u} , and obtaining the waveform data of the sampled ultrasonic reception signals S _{u → d} and the ultrasonic reception signals S _{d →} The cross-correlation calculation with the waveform data of _u may be performed, and the propagation time difference Δt may be calculated from the correlation function. A method for obtaining such a propagation time difference Δt is disclosed in Patent Document 2.

  The comparing unit 92 of the determining unit 9 compares the multiplied value Δt × | V ′ | calculated by the multiplied value calculating unit 91 with a predetermined allowable intensity difference Va (Step S5 in FIG. 12). When the multiplied value Δt × | V ′ | is larger than the allowable intensity difference Va, the comparing unit 92 outputs an alarm signal indicating that the flow rate accuracy is not sound (step S6 in FIG. 12). The allowable intensity difference Va may be set in advance in consideration of the S / N (signal-to-noise) ratio and the allowable accuracy of the flow rate.

  The output unit 10 outputs the calculation result of the flow measurement unit 8 and the determination result of the determination unit 9. As a method of outputting the calculation result of the flow rate measuring unit 8, there is, for example, display by the output unit 10, and information of the calculation result may be transmitted to the outside. Similarly, as a method of outputting the determination result of the comparing unit 92, there is a display by the output unit 10, blinking of a lamp for notifying an alarm or sound output, and the information of the determination result may be transmitted to the outside.

  As described above, in the present embodiment, the soundness of the flow rate accuracy of the ultrasonic flowmeter can be determined with a simple configuration. In the ultrasonic flow meter disclosed in Patent Document 3, the temperature and pressure of the fluid must be obtained. On the other hand, in the present embodiment, the soundness of the flow rate accuracy is determined without using the temperature and the pressure of the fluid by using the intensity difference between the ultrasonic reception signals in the forward direction and the reverse direction. be able to. Even if the magnitude of the ultrasonic reception signal changes depending on the temperature and pressure of the fluid, the influence on the flow rate error is determined by the ratio of the magnitude of the ultrasonic reception signal to the magnitude of the noise.

  Further, in the ultrasonic flow meter disclosed in Patent Document 3, it is necessary to previously create a database in which the theoretical amplification factors corresponding to various combinations of the type of the fluid, the temperature of the fluid, and the pressure of the fluid are registered. In this embodiment, it is only necessary to set the allowable intensity difference Va in advance, and the database can be made unnecessary. Further, in the present embodiment, by measuring the intensity difference V ', it is possible to detect deterioration of the ultrasonic sensors 3 and 4 or measurement abnormality such as bubbles.

In the above example, the intensity difference V ′ is obtained from the maximum value of the ultrasonic reception signal, but may be obtained from the minimum value. That is, the intensity difference calculation unit 90 obtains the minimum value Y _{MINu → d} of the ultrasonic reception signal S _{u → d} output from the reception unit 7 and obtains the ultrasonic reception signal S _{d →} output from the reception unit 7. The minimum value of _u , Y _{MINd → u,} may be obtained, and the absolute value | V ′ | of the intensity difference V ′ may be calculated by equation (13).

[Second embodiment]
Next, a second embodiment of the present invention will be described. FIG. 13 is a block diagram showing a configuration of an ultrasonic flowmeter according to a second embodiment of the present invention, and the same components as those in FIG. 11 are denoted by the same reference numerals. The ultrasonic flow meter according to the present embodiment includes a pipe 1, ultrasonic sensors 3, 4, a transmitting unit 6, a receiving unit 7, a flow measuring unit 8, a determining unit 9a, and an output unit 10. ing. The determination unit 9a includes a comparison unit 92, an amplitude difference calculation unit 93, and a multiplication value calculation unit 94.

The operations of the ultrasonic sensors 3 and 4, the transmitting unit 6, the receiving unit 7, and the flow measuring unit 8 are as described in the first embodiment.
FIG. 14 is a flowchart illustrating a flow rate accuracy soundness determination process in the ultrasonic flow meter according to the present embodiment. The amplitude difference calculation unit 93 of the determination unit 9a acquires the amplitude Y _{u → d} of the ultrasonic reception signal S _{u → d} output from the reception unit 7 (Step S10 in FIG. 14) and outputs the amplitude Y _{u → d} from the reception unit 7. The amplitude Y _{d → u} of the ultrasonic reception signal S _{d → u} is obtained (Step S11 in FIG. 14), and the absolute value | Y ′ | of the amplitude difference Y ′ is calculated (Step S12 in FIG. 14).
| Y ′ | = | Y _{u → d} −Y _{d → u} | (14)

  The multiplication value calculation unit 94 of the determination unit 9a calculates a multiplication value Δt × | Y ′ | of the absolute value | Y ′ | of the amplitude difference Y ′ calculated by the amplitude difference calculation unit 93 and the propagation time difference Δt (FIG. 14). Step S13). The method of determining the propagation time difference Δt is as described above.

  The comparing unit 92 of the determining unit 9a compares the multiplied value Δt × | Y ′ | calculated by the multiplied value calculating unit 94 with a predetermined allowable amplitude difference Ya (Step S14 in FIG. 14). When the multiplied value Δt × | Y ′ | is larger than the allowable amplitude difference Ya, the comparing unit 92 outputs an alarm signal indicating that the flow rate accuracy is not sound (step S15 in FIG. 14). The allowable amplitude difference Ya may be set in advance in consideration of the S / N ratio and the allowable accuracy of the flow rate.

The output unit 10 outputs the calculation result of the flow measurement unit 8 and the determination result of the determination unit 9a, as in the first embodiment.
Thus, in the present embodiment, the same effects as in the first embodiment can be obtained.

  At least the flow measurement unit 8 and the determination units 9 and 9a of the ultrasonic flow meters described in the first and second embodiments are a computer having a CPU (Central Processing Unit), a storage device, and an interface. Can be realized by a program that controls the hardware resources. The CPU executes the processing described in the first and second embodiments according to a program stored in the storage device.

  The present invention can be applied to an ultrasonic flowmeter.

  DESCRIPTION OF SYMBOLS 1 ... Piping, 2 ... Fluid, 3, 4 ... Ultrasonic sensor, 6 ... Transmitting part, 7 ... Receiving part, 8 ... Flow rate measuring part, 9, 9a ... Judgment part, 10 ... Output part, 90 ... Intensity difference calculation part , 91, 94: Multiplied value calculation unit, 92: Comparison unit, 93: Amplitude difference calculation unit.

Claims (3)

A pipe through which the fluid to be measured flows,
A pair of ultrasonic sensors arranged upstream and downstream of the pipe,
The maximum value of the first ultrasonic reception signal transmitted from the ultrasonic sensor on the upstream side and received by the ultrasonic sensor on the downstream side and the ultrasonic sensor transmitted from the ultrasonic sensor on the downstream side and the ultrasonic sensor on the upstream side Absolute value of the difference between the maximum value of the received second ultrasonic reception signal and the absolute value of the difference between the minimum value of the first ultrasonic reception signal and the minimum value of the second ultrasonic reception signal Intensity difference calculating means for calculating
Multiplication value calculation means for calculating a multiplication value of a propagation time difference between the first ultrasonic reception signal and the second ultrasonic reception signal, and an absolute value of the intensity difference calculated by the intensity difference calculation means;
An ultrasonic flowmeter comprising: a comparing unit that outputs an alarm when the multiplied value calculated by the multiplied value calculating unit is larger than a predetermined allowable intensity difference. A pipe through which the fluid to be measured flows,
A pair of ultrasonic sensors arranged upstream and downstream of the pipe,
The amplitude of the first ultrasonic reception signal transmitted from the ultrasonic sensor on the upstream side and received by the ultrasonic sensor on the downstream side and received by the ultrasonic sensor on the upstream side transmitted from the ultrasonic sensor on the downstream side Amplitude difference calculating means for calculating an absolute value of a difference from the amplitude of the second received ultrasonic signal;
Multiplication value calculation means for calculating a multiplication value of the propagation time difference between the first ultrasonic reception signal and the second ultrasonic reception signal, and the absolute value of the amplitude difference calculated by the amplitude difference calculation means;
An ultrasonic flowmeter comprising: a comparison unit that outputs an alarm when the multiplication value calculated by the multiplication value calculation unit is larger than a predetermined allowable amplitude difference. The ultrasonic flowmeter according to claim 1 or 2,
The multiplication value calculation unit, ultrasonic flowmeter, characterized in that determining the Propagation time difference from the correlation function of the waveform data cross the first ultrasonic reception signal and the second ultrasonic receiving signal.