JPH1151726A - Propagation time measuring device, supersonic type flow meter, method for measuring propagation time and controlling supersonic type flow meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure accurate flow rate steadily without increasing power consumption. SOLUTION: An amplifying circuit 7 amplifies and outputs an original detection signal as a detection signal, a zero crossing detecting circuit 8 performs the zero crossing detection of the detection signal and outputs a zero crossing detection signal SZX to an AND circuit 10, and a timer circuit 9 outputs a detection control signal SCCMP at the timing delayed by a predetermined time t0 from the output timing of a trigger signal. The AND circuit 10 obtains the logical product of the zero crossing detection signal SZX and the detection control signal SCCMP and outputs a flow rate detection signal SFL, and a control computational part 11 measures propagation time on the basis of the output timing of the trigger signal STRG and the output timing of the flow rate detection signal SFL and calculates the flow rate of a fluid. Therefore, there is no need for exciting resonators 4 and 5 in advance, it is possible to perform the stable and highly accurate measurement of propagation time, it is possible to reduce power consumption in comparison with the case of performing excitation, and it is possible to perform the highly accurate measurement of flow rate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a propagation time measuring device,
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a propagation time measuring method, an ultrasonic flow meter, and a control method of an ultrasonic flow meter, and particularly relates to a propagation time measuring device and a propagation method used for an ultrasonic flow meter that measures a flow rate of a gas or the like using an ultrasonic wave. The present invention relates to a time measuring method, an ultrasonic flow meter, and a control method of the ultrasonic flow meter.

[0002]

2. Description of the Related Art First Conventional Example FIG. 4 is a schematic block diagram of an ultrasonic flowmeter according to a first conventional example. The ultrasonic flowmeter 20 includes ultrasonic transducers 22 and 23 arranged in a part of a fluid conduit 21 so as to face each other, and an ultrasonic transducer 22 (= transmission side) disposed upstream of the fluid conduit 21. The time t1 until the ultrasonic wave emitted from the ultrasonic oscillator 23) (= function as a receiving-side oscillator) disposed downstream of the fluid conduit 21 is detected, and the ultrasonic oscillator 23 ( The time t2 until the ultrasonic vibrator 22 (functions by vibrating on the receiving side) detects the ultrasonic wave emitted from the transmitting side vibrator) (FIG. 5A).
(B)).

In this case, time t1 and time t2
Is expressed as follows: L is the distance between the ultrasonic transducers 22 and 23, C is the sound velocity, V is the flow velocity of the fluid, Q is the flow rate of the fluid, and A is the cross-sectional area of the fluid pipeline. L / (C + V) (1) t2 = L / (C−V) (2) V = L / 2 · ((t2−t1) / (t1 · t2)) (3) Q = k · A · V = k · A · {L / 2 · ((t2−t1) / (t1 · t2))} (4) Here, k is a coefficient determined by the type of fluid.

Meanwhile, in the ultrasonic flowmeter shown in FIG. 4, since the receiving-side vibrator simply receives the ultrasonic waves emitted from the transmitting-side vibrator, the transmitted ultrasonic waves can be reliably and promptly received. It was difficult to catch. FIG.
As shown in (b), when the flow rate of the fluid is a large flow rate, the time difference Δt between the time t1 and the time t2 is long, so that the measurement accuracy is improved. However, when the flow rate of the fluid is a small flow rate, Is that the time difference Δt between time t1 and time t2 is very short.

[0005] As a result, the detection position in the transmitted ultrasonic waveform becomes unclear, and the times t1 and t2 become inaccurate, resulting in a problem that accurate flow measurement cannot be performed. Therefore, an ultrasonic flowmeter is proposed in Japanese Patent Application Laid-Open No. 8-128874 in order to obtain a reception waveform having a good rising edge of the ultrasonic waveform, reliably and promptly narrow the reception signal, and perform accurate flow measurement. Have been. Second Conventional Example FIG. 6 shows a schematic block diagram of an ultrasonic flowmeter disclosed in Japanese Patent Application Laid-Open No. 8-128874.

Assuming that the fluid is flowing in the direction of the arrow a in the flow measuring tube 34, a trigger signal 41 is operated by inputting a signal from the start signal generator 38. As a result, a signal is sent to the switching unit 49 by the oscillation unit 42. In the initial state, the switching unit 49 includes the transmitting-side vibrator 3
The transmitting unit 39 is connected to 6, and the receiving unit 40 is connected to the receiving vibrator 37.

Therefore, the ultrasonic wave generated by the transmitting-side vibrator 36 by the trigger signal is transmitted for a predetermined time to the flow path 35.
Emitted within. In parallel with this, the delay timer 48 operates, and the trigger unit 41 operates again a little later than the first trigger, so that the oscillating unit 42 transmits ultrasonic waves for a certain time.

At this time, the signal from the delay timer 48 is also sent to the switching unit 49 at the same time, and by operating the switching unit 49, the transmitting unit 39 is connected to the receiving vibrator 37. It is in an excited state. Then, the receiving side vibrator 37 is over-relied for a predetermined time,
The switching unit 49 is activated again by the signal from, and the receiving-side vibrator 37 is connected to the receiving-side unit 40 again.

Therefore, since the receiving-side vibrator 37 is in an excited state, when an ultrasonic wave arrives from the transmitting-side vibrator 36, a large output signal can be generated without delay. This output signal is amplified by the amplifier 43, compared with the reference signal by the comparator 44, and then sends the signal to the timer 46.

The timer 46 measures the elapsed time from the signal already sent from the start unit 38 to the signal sent at this time, and the arithmetic unit 47 calculates the flow rate to calculate the flow rate. FIG. 7 shows an operation explanatory diagram (signal timing chart) of the second conventional example.

FIG. 7A shows an input signal of the transmitting side oscillator 36, and FIG. 7B shows a delay timer 48 (delay time =
(T1) is an input signal sent to the receiving oscillator 37, and FIG. 7C is a signal waveform of the receiving oscillator 37 excited by an input signal from the delay timer 48.

In general, the time Δt3 during which the vibration continues is longer than the vibration time Δt2 of the receiving vibrator 37. Also,
FIG. 7D shows a signal waveform of the receiving-side vibrator 37 when the vibration shown in FIG. 7B is not performed.

The flow velocity value in the flow path 35 can be calculated based on the propagation time T for the ultrasonic wave emitted from the transmitting transducer 36 to reach the receiving transducer 37.
Therefore, by accurately detecting the propagation time T, it is possible to perform highly accurate measurement.

Now, assuming that the threshold value as the reference signal is h, the detectable propagation time when the receiving-side vibrator is not vibrated is T ′, and an error E ′ = TT−T occurs. Becomes On the other hand, when the receiving oscillator 37 is vibrated by the input signal from the delay timer 48, the detectable propagation time is T ", and the error E" = TT "<E ', and the receiving oscillator 37 It is possible to measure the flow rate with higher accuracy as compared with the case where no vibration is applied to the third 37. Third conventional example Fig. 8A shows a schematic configuration block diagram of the third conventional example.

The ultrasonic flowmeter 50 receives the ultrasonic pulse signal PUS generated by the transmitting-side vibrator (not shown) and outputs the original detecting signal SA, and amplifies the original detecting signal SA. An amplification circuit 52 that outputs an amplified detection signal SB; a full-wave rectifier circuit 53 that performs full-wave rectification of the amplified detection signal SB and outputs the rectified signal SC; and an integration that integrates the rectified signal SC and outputs the integrated signal SD. A circuit 54;
A differential circuit 55 for differentiating the integrated signal SD to output a differential signal SE, and a zero-cross comparison circuit 56 for detecting zero-cross of the differential signal SE and outputting the same as a zero-cross detection signal SF are provided.

Next, the general operation will be described. Receiver side transducer 5
1 outputs the original detection signal SA to the amplifier circuit 52 by receiving the ultrasonic pulse signal PUS generated by the transmitting-side transducer (not shown). The amplifying circuit 52 amplifies the input original detection signal SA and generates a full-wave rectifier circuit 53 as an amplified detection signal SC.
Output to

The full-wave rectifier circuit 53 performs full-wave rectification of the amplified detection signal SB and outputs the rectified signal SC to the integration circuit 54. The integrating circuit 54 integrates the rectified signal SC and outputs it to the differentiating circuit 55 as an integrated signal SD.

The differentiating circuit 55 differentiates the integrated signal SD and outputs a differentiated signal SE to the zero-cross comparing circuit 56. The zero-cross comparison circuit 56 detects the zero-cross of the differential signal SE and outputs it as a zero-cross detection signal SF.

As a result, the time T from the rise of the ultrasonic pulse signal US to the fall of the zero-cross detection signal SF becomes the propagation time corresponding to the flow velocity of the fluid. Fourth Conventional Example FIG. 9A shows a schematic configuration block diagram of a fourth conventional example.

The ultrasonic flow meter 60 receives an ultrasonic pulse signal PUS (see FIG. 9 (b)) emitted from a transmitting-side vibrator (not shown) and outputs an original detection signal S1. And the amplified detection signal S
2; a comparison circuit 63 that performs full-wave rectification, integration, differentiation, and zero-cross detection of the amplified detection signal and outputs a zero-cross detection signal S3; and compares the amplified detection signal S2 with a predetermined reference level. A level comparison circuit 6 which outputs a reference zero-cross detection signal S4
4 and an AND circuit 65 for obtaining a logical product (AND) of the zero-cross detection signal S3 and the reference zero-cross detection signal S4 and outputting a logical product signal S5.

Next, the general operation will be described. Receiver side vibrator 6
1 outputs the original detection signal S1 to the amplifier circuit 62 by receiving the ultrasonic pulse signal PUS generated by the transmitting-side transducer (not shown). The amplification circuit 62 amplifies the input original detection signal S1 and outputs the amplified detection signal S2 to the comparison circuit 63 and the level comparison circuit 64.

As a result, the comparison circuit 63 performs full-wave rectification, integration, differentiation, and zero-cross detection of the amplified detection signal S2, and outputs a zero-cross detection signal S3 (see FIG. 9C).
Output to the D circuit 65. On the other hand, the level comparison circuit 64
The amplified detection signal S2 is compared with a predetermined reference level, and is output to the AND circuit 65 as a reference zero-cross detection signal S4 (see FIG. 9D).

As a result, the AND circuit 65 calculates the logical product (AND) of the zero-cross detection signal S3 and the reference zero-cross detection signal S4, and outputs a logical product signal S5 (see FIG. 9E). As a result, the time T from the rise of the ultrasonic pulse signal US to the rise of the logical product signal is the propagation time corresponding to the flow velocity of the fluid. Fifth Conventional Example FIG. 10 shows a schematic block diagram of a fifth conventional example.

The ultrasonic flow meter 70 receives the ultrasonic pulse signal PUS generated by the transmitting-side vibrator (not shown) and outputs the original detecting signal S11, and amplifies the original detecting signal S11. An amplification circuit 72 that outputs an amplified detection signal S12, a peak hold circuit 73 that performs peak hold on the amplified detection signal S12, and outputs a peak hold signal S13, a peak hold signal S13, and an amplified detection signal S12.
And a level comparison circuit 74 for comparing the 12 levels and outputting a comparison result signal S14.

The receiving-side vibrator 71 outputs an original detection signal S11 to the amplifying circuit 72 by receiving the ultrasonic pulse signal PUS generated by the transmitting-side vibrator (not shown). The amplification circuit 72 amplifies the original detection signal S11 and outputs an amplification detection signal S12 (see FIG. 10C) to the peak hold circuit 73 and the level comparison circuit 74.

The peak hold circuit 73 holds the peak of the amplified detection signal S12, and outputs the peak hold signal S13.
(See FIG. 10D) to the level comparison circuit 74. The level comparison circuit 74 compares the level of the peak hold signal S13 with the level of the amplified detection signal S12, and outputs the comparison result signal S12.
14 (see FIG. 10E).

As a result, the time T from the rise of the ultrasonic pulse signal PUS to the rise of the comparison result signal S14 is a propagation time corresponding to the flow velocity of the fluid. Sixth conventional example FIG. 11 shows a schematic block diagram of a sixth conventional example.

The ultrasonic flow meter 80 receives the ultrasonic pulse signal generated by the transmitting-side vibrator (not shown) and outputs the original detecting signal S21, and amplifies the original detecting signal S21. An amplification circuit 82 that outputs an amplification detection signal S22 and a zero-cross comparison circuit 83 that performs zero-cross detection of the amplification detection signal S22 and outputs the same as a zero-cross detection signal S23 are provided.

The receiving-side vibrator 81 outputs an original detection signal S21 to the amplifier circuit 82 by receiving an ultrasonic pulse signal generated by a transmitting-side vibrator (not shown). Amplifier circuit 82
Amplifies the original detection signal S21 and outputs the amplified detection signal S22 to the zero-cross comparison circuit 83.

The zero-cross comparison circuit 83 detects a zero-cross of the amplified detection signal S22 and performs a zero-cross detection signal S23.
(See FIG. 11B). As a result, the time T from the rise of the ultrasonic pulse signal to the rise of the zero-cross detection signal is a propagation time corresponding to the flow velocity of the fluid.

[0031]

In the second prior art, when receiving an ultrasonic pulse signal, it is necessary to vibrate the receiving transducer in advance, so that the power consumption increases. was there.

In the third conventional example, when the level of the rectified signal is low (when the amplitude level of the original detection signal is low), the peak of the integrated signal is flattened, and the same position cannot be always detected. However, there has been a problem that an accurate flow rate cannot be measured. Further, there is a problem that the reverberation in the pipe affects a received waveform, a peak position of the differential signal is shifted, and an accurate flow rate cannot be measured.

In the fourth conventional example, the output of the second level comparator is not constant because the reception level changes, and the same position cannot be always detected. Therefore, an accurate flow rate is measured. There was a problem that it was not possible. In the fifth conventional example, since the peak position changes depending on the flow rate, there has been a problem that the flow rate cannot be reliably and accurately detected.

In the sixth conventional example, no countermeasures are taken against noise input, and the noise input causes erroneous detection, so that an accurate flow rate cannot be measured. was there. Therefore, an object of the present invention is to provide a propagation time measurement device and a propagation time measurement method capable of stably and accurately measuring an ultrasonic propagation time without increasing power consumption, and a stable and accurate fluid flow rate. It is an object of the present invention to provide an ultrasonic flowmeter capable of measuring a flow rate and a control method of the ultrasonic flowmeter.

[0035]

According to a first aspect of the present invention, an ultrasonic pulse signal is transmitted through a fluid passage by a transmitting-side vibrator, and the ultrasonic pulse signal is transmitted by a receiving-side vibrator. In a propagation time measuring device that receives an ultrasonic pulse signal and measures the propagation time based on the transmission timing of the ultrasonic pulse signal and the signal state of the ultrasonic pulse signal, the reception-side vibrator includes the ultrasonic pulse A zero-cross detection means for performing zero-cross detection of a detection signal output by receiving the signal and outputting a zero-cross detection signal; and outputting a detection control signal at a timing delayed by a predetermined time t0 from the transmission timing of the ultrasonic pulse signal. Timer means for performing the AND operation of the zero-cross detection signal and the detection control signal, and outputting a flow rate detection signal; Measuring means for measuring the propagation time based on the transmission timing of the ultrasonic pulse signal and the output timing of the flow rate detection signal.

According to a second aspect of the present invention, there is provided receiving means for receiving an ultrasonic pulse signal transmitted through a fluid flow path at a predetermined transmission timing and outputting a detection signal, and detecting zero-crossing of the detection signal. A zero-crossing detection circuit for outputting a zero-crossing detection signal, a timer means for outputting a detection control signal at a timing delayed by a predetermined time t0 from the transmission timing, and a logical product of the zero-crossing detection signal and the detection control signal. , An AND circuit that outputs a flow rate detection signal, and measuring means that measures the propagation time based on the transmission timing of the ultrasonic pulse signal and the output timing of the flow rate detection signal.

According to a third aspect of the present invention, in the first or the second aspect of the present invention, the predetermined time t0 is such that the detection signal is stably provided when the flow velocity of the fluid is maximum within the measurement range. When the detectable first stable region and the flow velocity of the fluid are minimized within the measurement range, the detection signal is determined based on the second stable region in which stable detection is possible.

According to a fourth aspect of the present invention, a trigger means for outputting a trigger signal is disposed upstream of a fluid flow path, and transmits an ultrasonic pulse signal via the fluid flow path based on an oscillation signal. Or, a first transmitting and receiving means for receiving the transmitted ultrasonic pulse signal and outputting an original detection signal,
An original detection signal that is disposed downstream of the fluid flow path and transmits an ultrasonic pulse signal through the fluid flow path based on the oscillation signal, or receives the transmitted ultrasonic pulse signal. Second transmitting / receiving means for outputting a signal; an oscillating means for generating and outputting the oscillating signal based on the trigger signal; an amplifying means for amplifying the original detection signal and outputting it as a detection signal; Switching means for alternately connecting the oscillating means to one of the transmitting and receiving means and the amplifying means to the other; zero-cross detecting means for performing zero-cross detection of the detection signal and outputting a zero-cross detection signal; and the trigger signal. Timer means for outputting a detection control signal at a timing delayed by a predetermined time t0 from the output timing of the zero-crossing detection signal and the detection control signal. To output a flow rate detection signal
A D circuit; measuring means for measuring the propagation time based on the output timing of the trigger signal and the output timing of the flow rate detection signal;
A first propagation time when the ultrasonic pulse signal is propagated to the transmitting / receiving means, and a second propagation time when the ultrasonic pulse signal is propagated from the second transmitting / receiving means to the first transmitting / receiving means.
Flow rate calculating means for calculating the flow rate of the fluid based on the propagation time.

According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the predetermined time t0 is a first time at which the detection signal can be stably detected when the flow velocity of the fluid is maximum within a measurement range. The detection signal is determined based on the stable region and the second stable region in which the detection signal can be stably detected when the flow velocity of the fluid is minimized within the measurement range.

According to a sixth aspect of the present invention, in the invention of the fifth aspect, the predetermined time t0 is such that a deviation of detection timing is within one wavelength in the first stable region and the second stable region. The resonance frequency of the first transmission / reception means and the resonance frequency of the second transmission / reception means are determined.

According to a seventh aspect of the present invention, an ultrasonic pulse signal is transmitted by a transmitting-side vibrator through a fluid flow path, and the ultrasonic pulse signal is received by a receiving-side vibrator. In the propagation time measuring method for measuring the propagation time based on the transmission timing of the ultrasonic pulse signal and the signal state of the ultrasonic pulse signal, zero-cross detection of a detection signal output by the receiving transducer receiving the ultrasonic pulse signal Performing a zero-cross detection signal to generate a zero-cross detection signal, a detection control signal output step of outputting a detection control signal at a timing delayed by a predetermined time from the transmission timing of the ultrasonic pulse signal, the zero-cross detection signal and the detection control ANDing step of ANDing signals, transmission timing of the ultrasonic pulse signal and output of the flow rate detection signal Configure and a measurement step of measuring the propagation time based on the timing.

According to the eighth aspect of the present invention, a zero-cross detection of a detection signal obtained by receiving an ultrasonic pulse signal transmitted through a fluid flow path at a predetermined transmission timing to generate a zero-cross detection signal is performed. A detection step, a detection control signal output step of outputting a detection control signal at a timing delayed by a predetermined time from the transmission timing, and a logic of taking a logical product of the zero-cross detection signal and the detection control signal and outputting a flow rate detection signal And a measuring step of measuring the propagation time based on the transmission timing of the ultrasonic pulse signal and the output timing of the flow rate detection signal.

According to a ninth aspect of the present invention, there is provided a trigger output unit for outputting a trigger signal for controlling the output timing of an ultrasonic pulse, and a trigger output unit disposed upstream of a fluid flow path.
A first transmitting / receiving unit that transmits an ultrasonic pulse signal through the fluid flow path based on the oscillation signal, or receives the transmitted ultrasonic pulse signal and outputs an original detection signal; An ultrasonic pulse signal is transmitted through the fluid flow path based on the input oscillation signal, or the transmitted ultrasonic pulse signal is received and an original detection signal is output. A second transmitting / receiving unit, an oscillating unit for generating and outputting the oscillating signal based on the trigger signal, an amplifying unit for amplifying the original detection signal and outputting it as a detection signal, a first transmitting / receiving unit means and a second transmitting / receiving unit. A switching unit for alternately connecting the oscillation unit to one of the transmitting and receiving units and the amplifying means to the other, and controlling the ultrasonic flowmeter. A zero-cross detection step of performing a zero-cross detection of a signal to output a zero-cross detection signal, a logical AND step of taking a logical product of the zero-cross detection signal and the detection control signal and outputting a flow rate detection signal, and an output timing of the trigger signal And a measuring step of measuring the propagation time based on the output timing of the flow rate detection signal,
A first propagation time when the ultrasonic pulse signal is propagated from the first transmitting / receiving unit to the second transmitting / receiving unit, and a case where the ultrasonic pulse signal is propagated from the second transmitting / receiving unit to the first transmitting / receiving unit And a flow rate calculating step of calculating the flow rate of the fluid based on the second propagation time.

According to the first aspect of the present invention, the zero-cross detecting means performs zero-cross detection of a detection signal output when the receiving-side vibrator receives the ultrasonic pulse signal, and outputs the zero-cross detection signal to the AND circuit. I do. The timer means outputs the detection control signal at a timing delayed by a predetermined time t0 from the transmission timing of the ultrasonic pulse signal.
Output to D circuit.

The AND circuit calculates the logical product of the zero-cross detection signal and the detection control signal, and outputs a flow rate detection signal to the measuring means. The measuring means measures the propagation time based on the transmission timing of the ultrasonic pulse signal and the output timing of the flow rate detection signal.

According to the second aspect of the present invention, the receiving means receives the ultrasonic pulse signal transmitted through the fluid flow path at a predetermined transmission timing and outputs a detection signal to the zero-cross detection circuit. The zero-cross detection circuit performs zero-cross detection of the detection signal and ANDs the zero-cross detection signal.
Output to the circuit.

The timer means outputs the detection control signal at a timing delayed by a predetermined time t0 from the transmission timing.
Output to D circuit. Thus, the AND circuit calculates the logical product of the zero-cross detection signal and the detection control signal, and outputs the flow rate detection signal to the measuring means.

The measuring means measures the propagation time based on the transmission timing of the ultrasonic pulse signal and the output timing of the flow rate detection signal. According to the third aspect of the present invention, in addition to the operation of the first or second aspect of the present invention, the detection signal is stably provided for the predetermined time t0 when the flow velocity of the fluid becomes maximum within the measurement range. Since the detection signal is determined based on the first stable area where the detection is possible and the second stable area where the flow velocity of the fluid is the minimum within the measurement range, the detection signal is stably detectable, measurement is always possible.

According to the present invention, the trigger means outputs a trigger signal. The switching means alternately connects the oscillating means to one of the first transmitting / receiving means and the second transmitting / receiving means and the amplifying means to the other. The oscillating means generates an oscillating signal based on the trigger signal and outputs the oscillating signal to one of the first transmitting / receiving means and the second transmitting / receiving means via the switching means.

Thus, one of the first transmitting / receiving means and the second transmitting / receiving means transmits an ultrasonic pulse signal through the fluid flow path based on the oscillation signal input through the switching means. The other of the first transmitting / receiving means and the second transmitting / receiving means receives the ultrasonic pulse signal transmitted from the one transmitting / receiving means and outputs the original detection signal to the amplifying means via the switching means.

The amplification means amplifies the original detection signal and outputs it to the zero-cross detection means as a detection signal. The zero-cross detection means performs zero-cross detection of the detection signal and outputs a zero-cross detection signal to an AND circuit.

The timer outputs a detection control signal to the AND circuit at a timing delayed by a predetermined time t0 from the output timing of the trigger signal. The AND circuit calculates a logical product of the zero-cross detection signal and the detection control signal, and outputs a flow rate detection signal to the measurement unit.

The measuring means measures the propagation time based on the output timing of the trigger signal and the output timing of the flow rate detection signal, and the flow rate calculating means transmits the ultrasonic pulse signal from the first transmitting / receiving means to the second transmitting / receiving means. Then, the flow rate of the fluid is calculated based on the first propagation time when the ultrasonic pulse signal is transmitted from the second transmitting / receiving means to the first transmitting / receiving means.

According to the fifth aspect of the invention, in addition to the operation of the fourth aspect of the present invention, the detection signal can be stably detected during the predetermined time t0 when the flow velocity of the fluid is maximum within the measurement range. Since the detection signal is determined based on the first stable region and the second stable region in which the flow rate of the fluid becomes minimum within the measurement range, the detection signal can be stably detected, the measurement can always be performed.

According to the invention described in claim 6, in addition to the effect of the invention described in claim 5, the deviation of the detection timing in the first stable region and the second stable region during the predetermined time t0 is within one wavelength. As described above, since the resonance frequencies of the first transmission / reception unit and the second transmission / reception unit are determined, the influence of the displacement of the detection position can be reduced and accurate measurement can be performed.

According to the seventh aspect of the present invention, in the zero-cross detecting step, the receiving-side vibrator performs a zero-cross detection of a detection signal output by receiving the ultrasonic pulse signal to generate a zero-cross detection signal. The detection control signal output step outputs the detection control signal at a timing delayed by a predetermined time from the transmission timing of the ultrasonic pulse signal.

In the logical product step, a logical product of the zero cross detection signal and the detection control signal is obtained. The measuring step measures the propagation time based on the transmission timing of the ultrasonic pulse signal and the output timing of the flow rate detection signal. According to the eighth aspect of the present invention, the zero-cross detection step performs a zero-cross detection of a detection signal obtained by receiving an ultrasonic pulse signal transmitted through a fluid flow path at a predetermined transmission timing, and performs a zero-cross detection signal. Generate

In the detection control signal output step, the detection control signal is output at a timing delayed by a predetermined time from the transmission timing. The logical product step calculates the logical product of the zero-cross detection signal and the detection control signal, and outputs a flow rate detection signal.

In the measuring step, the propagation time is measured based on the transmission timing of the ultrasonic pulse signal and the output timing of the flow rate detection signal. According to the ninth aspect of the present invention, in the zero crossing step, the detection signal is subjected to zero cross detection and a zero cross detection signal is output.

The logical product step calculates the logical product of the zero-cross detection signal and the detection control signal, and outputs a flow rate detection signal.
The measuring step measures the propagation time based on the output timing of the trigger signal and the output timing of the flow rate detection signal.

As a result, the flow rate calculating step includes the first propagation time when the ultrasonic pulse signal is propagated from the first transmitting / receiving unit to the second transmitting / receiving unit, and the ultrasonic pulse from the second transmitting / receiving unit to the first transmitting / receiving unit. The flow rate of the fluid is calculated based on the second propagation time when the signal is propagated.

[0062]

Preferred embodiments of the present invention will now be described with reference to the drawings. Overview Configuration Figure 1 shows a schematic configuration block diagram of an ultrasonic flowmeter of the embodiment.

The ultrasonic flowmeter 1 generates a trigger signal STRG for starting a measurement and oscillating an ultrasonic pulse signal, and generates and outputs an oscillation signal SVB based on the trigger signal STRG. The oscillation unit 3 is driven by the oscillation signal SVB at the time of transmission, generates and outputs an ultrasonic pulse signal PUS, and receives the ultrasonic pulse signal PUS at the time of reception.
The first oscillator 4 and the second oscillator 5 that output the original detection signal SDET0 based on the first and second oscillators 1 and 2 output the oscillation signal SVB to one of the first oscillator 4 and the second oscillator 5 and output the other oscillator. A switching unit 6 for outputting an original detection signal SDET0 from the switching unit 6, and an amplification detection signal S for amplifying the original detection signal SDET0 output from the switching unit 6.
The amplifier circuit 7 that outputs ADET, the zero-cross detection circuit 8 that detects the zero-cross of the amplified detection signal SADET and outputs the same as the zero-cross detection signal SZX, and compares them at a timing delayed by a predetermined delay time t0 from the rising timing of the trigger signal STRG. A timer circuit 9 for outputting a control signal SCCMP, a zero-cross detection signal SZX and a comparison control signal SCCMP
And an AND circuit 10 for obtaining a logical product (AND) and outputting a flow rate detection signal SFL as a logical product signal, and a control operation for controlling the entire ultrasonic flowmeter 1 and performing a flow rate calculation based on the flow rate detection signal SFL. And a unit 11.

In this case, it is assumed that the first vibrator 4 is disposed on the upstream side in the fluid flow path, and the second vibrator 5 is disposed on the downstream side in the fluid flow path.
Are configured using a crystal oscillator in order to further reduce errors. Of the configuration of the ultrasonic flowmeter 1, at least a zero-cross detection circuit 8, a timer circuit 9, and an AND
The setting of the delay time t0 of the comparison control signal SCCMP by the circuit 10 and the control calculation unit 11 Here, the setting of the delay time t0 will be described before the general operation is described. In this description, the first vibrator 4 will be described as a transmitting side, and the second vibrator 5 will be described as a receiving side.

When the ultrasonic pulse signal PUS generated and output by the first transducer 4 on the transmitting side is received by the second transducer 5 on the receiving side, the receiving transducer 5 is vibrated by resonance.
The vibration waveform is as shown in FIG.
The vibration waveform of the reception-side vibration 5 has a vibration stable region where the peak height is substantially constant.

Therefore, the delay time t0 is compared with the comparison control signal SCCM.
It can be seen that stable measurement can be performed if the output of P (in FIG. 3, the rising timing of the comparison control signal SCCMP) is set so as to be included in the oscillation stable region. Therefore, the stability of the vibration waveform (see FIG. 2B) of the second vibrator 5 functioning as the receiving vibrator corresponding to the case where the flow rate of the fluid is the highest among the flow rates that can be measured by the ultrasonic flowmeter. The vibration waveform of the second vibrator 5 functioning as the receiving vibrator corresponding to the time zone where the region exists and the flow rate of the fluid which is the smallest among the flow rates measurable by the ultrasonic flowmeter (FIG.
(C), when the time zone where the stable region exists is compared on the same time axis with reference to the time when the ultrasonic pulse signal PUS is transmitted, the time zone is included in the time zone common to both vibration stable regions. If the delay time t0 is determined such that the comparison control signal SCCMP is always output within the stable range.

Further, it is necessary to determine the resonance frequencies of the first vibrator 4 and the second vibrator 5 so that a maximum of one wavelength or more does not occur from the target vibration peak. Operations The following is an overview operations. In this case, in the initial state, the switching unit 6 is set so that the first vibrator 4 is on the transmitting side and the second vibrator 5 is on the receiving side.

First, the control operation section 11 controls the trigger section 2 to output a trigger signal STRG (see FIG. 3E) to the oscillation section 3. As a result, the oscillating unit 3 generates an oscillation signal SVB and outputs the oscillating signal SVB to the first vibrator 4 functioning as a transmitting-side vibrator via the switching unit 6. Thus, the first vibrator 4 is driven by the oscillation signal SVB, and generates and outputs an ultrasonic pulse signal PUS (see FIG. 3B).

Thus, the second transducer 5 outputs the original detection signal SDET0 to the amplifier circuit 7 based on the ultrasonic pulse signal BUS received from the first transducer 4. The amplification circuit 7 amplifies the input original detection signal SDET0 and amplifies and detects the amplified detection signal SADET.
(See FIG. 3C) is output to the zero cross detection circuit 8.

The zero-cross detection circuit 8 outputs the amplified detection signal S
Performs ADET zero-cross detection and generates a zero-cross detection signal SZX.
As shown in FIG. 3 (d), in parallel with these operations of outputting to one input terminal of the AND circuit 10, the timer circuit 9
Output the comparison control signal SCCMP to the other input terminal of the AND circuit 10 at a timing delayed by a predetermined delay time t0 from the rising timing of the trigger signal STRG, that is, the comparison control signal SCCCMP of "H" level (FIG.
(See (f)) to the other input terminal of the AND circuit 10.

As a result, the AND circuit 10 performs a logical product (AND) of the zero-cross detection signal SZX and the comparison control signal SCCMP.
And the flow velocity detection signal SFL (FIG. 3
(See (g)). As a result, the time T (see FIG. 3 (g)) from when the comparison control signal SCCMP goes high to when the zero-cross detection signal SZX first rises is the propagation time T1 in the gas flow direction.

Next, the control operation unit 11 switches the switching unit 6
Is switched so that the first vibrator 4 is on the receiving side and the second vibrator 5 is on the receiving side, and then the trigger unit 2 is controlled to generate the trigger signal STRG (see FIG. 3 (e)). 3 output. As a result, the oscillating unit 3 generates an oscillation signal SVB and outputs it to the second vibrator 5 functioning as a transmitting-side vibrator via the switching unit 6.

As a result, the second oscillator 5 outputs the oscillation signal SVB
Generates and outputs an ultrasonic pulse signal PUS (see FIG. 3B). Thereby, the first vibrator 4
Outputs an original detection signal SDET0 to the amplifier circuit 7 based on the ultrasonic pulse signal pus received from the second transducer 5.

The amplification circuit 7 receives the original detection signal SDE
It amplifies T0 and outputs an amplified detection signal SADET (see FIG. 3C) to the zero-cross detection circuit 8. Zero cross detection circuit 8
Performs the zero-cross detection of the amplified detection signal SADET, and outputs the zero-cross detection signal SZX (see FIG. 3D) to one input terminal of the AND circuit 10. In parallel with these operations, the timer circuit 9 The comparison control signal SCCMP is output to the other input terminal of the AND circuit 10 at a timing delayed by a predetermined delay time t0 from the rising timing of the signal STRG, that is, the comparison control signal SCCMP at "H" level (FIG. 3 (f) ) Is output to the other input terminal of the AND circuit 10.

As a result, the AND circuit 10 performs a logical product (AND) of the zero-cross detection signal SZX and the comparison control signal SCCMP.
And the flow velocity detection signal SFL (FIG. 3
(See (g)). As a result, the time T from when the comparison control signal SCCMP goes high to when the zero-cross detection signal SZX first rises is the propagation time T2 in the direction opposite to the gas flow.

In this case, time T1 and time T2
Is expressed as follows: L is the distance between the first vibrator 4 and the second vibrator 5, the sound velocity is C, the flow velocity of the fluid is V, the flow rate of the fluid is Q, and the cross-sectional area of the fluid pipeline is A. L / (C + V) (1) T2 = L / (C−V) (2) V = L / 2 · ((T2−T1) / (T1 · T2)) (3) Q = k · A · V = k · A · {L / 2 · ((T2−T1) / (T1 · T2))} (4) Here, k is a coefficient determined by the type of fluid.

Therefore, the control operation unit 11
The flow velocity V of the fluid and the flow rate Q of the fluid are calculated based on the equations (3) and (4). As a result, stable and accurate flow rate measurement can be performed. Furthermore, since it is not necessary to vibrate the receiving transducer beforehand, power consumption can be reduced.

Further, even at a low flow rate, an accurate flow rate can be measured, and the sensitivity can be improved.

[0079]

According to the first aspect of the present invention, the timer means ANDs the detection control signal at a timing delayed by a predetermined time t0 from the transmission timing of the ultrasonic pulse signal.
The AND circuit takes the logical product of the zero-cross detection signal and the detection control signal, and outputs the flow rate detection signal to the measuring means. The measuring means outputs the ultrasonic pulse signal transmission timing and the flow detection signal output timing. , It is possible to accurately measure a wide range of propagation times from a low flow rate to a high flow rate. Furthermore, by using the propagation time measuring device for the ultrasonic flowmeter, it is possible to perform highly accurate flow measurement.

According to the second aspect of the present invention, the receiving means receives the ultrasonic pulse signal transmitted through the fluid flow path at a predetermined transmission timing and outputs a detection signal to the zero-cross detection circuit, The zero-cross detection circuit performs zero-cross detection of the detection signal and outputs a zero-cross detection signal to an AND circuit. The timer means outputs the zero-cross detection signal to the AND circuit at a timing delayed by a predetermined time t0 from the transmission timing.
Output to the D circuit, the AND circuit takes the logical product of the zero-cross detection signal and the detection control signal, and outputs the flow rate detection signal to the measuring means. The measuring means outputs the transmission timing of the ultrasonic pulse signal and the output of the flow rate detection signal. Since the propagation time is measured based on the timing, it is not necessary to vibrate the receiving means in advance, and it is possible to measure the propagation time stably with high accuracy. It becomes possible to reduce. Further, by using the propagation time measuring device for the ultrasonic flowmeter, it is possible to perform the flow measurement with high accuracy.

According to the third aspect of the present invention, in addition to the operation of the first or second aspect of the present invention, the predetermined time t
0 is a first stable region where the detection signal can be stably detected when the flow velocity of the fluid is maximum within the measurement range, and the detection signal can be stably detected when the flow velocity of the fluid is minimum within the measurement range. Since the determination is performed based on the second stable region, the measurement can be always performed, and the stable and accurate propagation time measurement can be performed. In addition, the accuracy can be improved by using the propagation time measuring device for the ultrasonic flow meter. It is possible to perform a high flow rate measurement.

According to the fourth aspect of the present invention, the oscillating means generates an oscillating signal based on the trigger signal, and outputs the oscillating signal to one of the first transmitting / receiving means and the second transmitting / receiving means via the switching means. One of the first transmitting / receiving unit and the second transmitting / receiving unit transmits an ultrasonic pulse signal through a fluid flow path based on an oscillation signal input through the switching unit, and outputs the first transmitting / receiving unit or One of the second transmitting and receiving means receives the ultrasonic pulse signal transmitted from one of the transmitting and receiving means and outputs the original detection signal to the amplifying means via the switching means. The amplifying means amplifies the original detection signal. And outputs the detection signal to a zero-cross detection means. The zero-cross detection means performs zero-cross detection of the detection signal and outputs a zero-cross detection signal to an AND circuit. The timer means outputs a trigger signal. The detection circuit outputs a detection control signal to the AND circuit at a timing delayed by a predetermined time t0 from the imaging, and the AND circuit calculates a logical product of the zero-cross detection signal and the detection control signal, and outputs a flow rate detection signal to the measurement means. Measures the propagation time based on the output timing of the trigger signal and the output timing of the flow rate detection signal, and the flow rate calculating means determines the first time when the ultrasonic pulse signal is propagated from the first transmitting / receiving means to the second transmitting / receiving means. Since the flow rate of the fluid is calculated based on the propagation time and the second propagation time when the ultrasonic pulse signal is propagated from the second transmitting / receiving means to the first transmitting / receiving means, the receiving means does not need to be vibrated in advance, and is stable. This makes it possible to perform highly accurate propagation time measurement, reduce power consumption compared to the case of performing vibration, and perform highly accurate flow rate measurement. Ukoto is possible.

According to the fifth aspect of the invention, in addition to the operation of the fourth aspect of the present invention, the detection signal can be stably detected during the predetermined time t0 when the flow velocity of the fluid is maximum within the measurement range. Since the detection signal is determined based on the first stable region and the second stable region in which the flow rate of the fluid becomes minimum within the measurement range, the detection signal can be stably detected, and the propagation can be performed stably with high accuracy. Time measurement can be performed, and by using the propagation time measuring device for an ultrasonic flowmeter, highly accurate flow measurement can be performed.

According to the invention described in claim 6, in addition to the effect of the invention described in claim 5, the deviation of the detection timing in the first stable region and the second stable region during the predetermined time t0 is within one wavelength. As described above, since the resonance frequencies of the first transmission / reception unit and the second transmission / reception unit are determined, it is possible to reduce the influence of the shift of the detection position, perform stable and accurate measurement, and perform high-accuracy flow measurement. Become.

According to the seventh aspect of the present invention, in the zero-cross detecting step, the receiving-side vibrator performs a zero-cross detection of a detection signal output by receiving the ultrasonic pulse signal, generates a zero-cross detection signal, and performs detection control. The signal output step outputs the detection control signal at a timing delayed by a predetermined time from the transmission timing of the ultrasonic pulse signal.

In the logical product step, the logical product of the zero cross detection signal and the detection control signal is obtained. In the measurement step, the propagation time is measured based on the transmission timing of the ultrasonic pulse signal and the output timing of the flow rate detection signal, so that a wide range of propagation time from a low flow rate to a high flow rate can be accurately measured. Furthermore, by using the propagation time measuring device for the ultrasonic flowmeter, it is possible to perform highly accurate flow measurement.

According to the eighth aspect of the present invention, the zero-cross detecting step performs zero-cross detection of a detection signal obtained by receiving an ultrasonic pulse signal transmitted through a fluid flow path at a predetermined transmission timing. A zero-cross detection signal is generated, the detection control signal output step outputs a detection control signal at a timing delayed by a predetermined time from the transmission timing, and a logical product step takes a logical product of the zero cross detection signal and the detection control signal, The flow rate detection signal is output, and the measuring step measures the propagation time based on the transmission timing of the ultrasonic pulse signal and the output timing of the flow rate detection signal. , It is possible to measure a high propagation time, and it is possible to reduce the power consumption as compared with the case of performing vibration. Further, by applying the present invention to an ultrasonic flowmeter, it is possible to perform highly accurate flow rate measurement.

According to the ninth aspect of the present invention, in the zero-crossing step, a zero-crossing detection of the detection signal is performed to output a zero-crossing detection signal, and in the logical producting step, a logical product of the zero-crossing detection signal and the detection control signal is obtained. Outputting a flow rate detection signal, the measuring step measures a propagation time based on an output timing of the trigger signal and an output timing of the flow rate detection signal, and the flow rate calculating step includes transmitting an ultrasonic pulse from the first transmitting / receiving unit to the second transmitting / receiving unit. The first when the signal is propagated
Since the flow rate of the fluid is calculated based on the propagation time and the second propagation time when the ultrasonic pulse signal is propagated from the second transmission / reception unit to the first transmission / reception unit, there is no need to excite the transmission / reception unit in advance and it is stable. As a result, it is possible to perform highly accurate propagation time measurement, reduce power consumption as compared with the case of performing vibration, and perform highly accurate flow rate measurement.

[Brief description of the drawings]

FIG. 1 is a schematic configuration block diagram of an ultrasonic flowmeter according to an embodiment.

FIG. 2 is an explanatory diagram of setting of a delay time of a comparison control signal.

FIG. 3 is an operation explanatory diagram of the embodiment.

FIG. 4 is a schematic block diagram of a first conventional example.

FIG. 5 is a diagram illustrating the principle of flow rate detection.

FIG. 6 is a schematic configuration block diagram of a second conventional example.

FIG. 7 is an operation explanatory diagram of the second conventional example.

FIG. 8 is a schematic configuration block and operation explanatory diagram of a third conventional example.

FIG. 9 is a schematic configuration block and operation explanatory diagram of a fourth conventional example.

FIG. 10 is a schematic configuration block and operation explanatory diagram of a fifth conventional example.

FIG. 11 is a schematic structural block diagram and operation explanatory diagram of a sixth conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ultrasonic flow meter 2 Trigger part 3 Oscillator 4 First vibrator 5 Second vibrator 6 Switching part 7 Amplification circuit 8 Zero cross detection circuit 9 Timer circuit 10 AND circuit 11 Control operation part

Claims (9)

[Claims] An ultrasonic pulse signal is transmitted from a transmitting-side vibrator through a fluid flow path, the ultrasonic pulse signal is received by a receiving-side vibrator, and the transmission timing of the ultrasonic pulse signal and the ultrasonic pulse signal are transmitted. In the propagation time measuring device that measures the propagation time based on the signal state of the sound pulse signal, the receiving-side vibrator performs zero-cross detection of a detection signal output by receiving the ultrasonic pulse signal, and performs a zero-cross detection signal. And a predetermined time t from the transmission timing of the ultrasonic pulse signal.
Timer means for outputting a detection control signal at a timing delayed by 0; AND circuit for calculating a logical product of the zero-cross detection signal and the detection control signal to output a flow rate detection signal; and transmission timing of the ultrasonic pulse signal And a measuring means for measuring the propagation time based on the output timing of the flow rate detection signal. 2. A receiving means for receiving an ultrasonic pulse signal transmitted through a fluid flow path at a predetermined transmission timing and outputting a detection signal; and performing zero-cross detection of the detection signal to generate a zero-cross detection signal. A zero-cross detection circuit for outputting, a timer means for outputting a detection control signal at a timing delayed by a predetermined time t0 from the transmission timing, and a logical product of the zero-cross detection signal and the detection control signal to output a flow detection signal And a measuring means for measuring the propagation time based on the transmission timing of the ultrasonic pulse signal and the output timing of the flow rate detection signal. 3. The propagation time measuring device according to claim 1, wherein the predetermined time t0 can stably detect the detection signal when the flow velocity of the fluid is maximum in a measurement range. A propagation time measuring device, wherein the detection signal is determined based on a first stable region and a second stable region in which the detection signal can be stably detected when the flow velocity of the fluid is minimized within the measurement range. 4. Trigger means for outputting a trigger signal, and disposed at an upstream side of a fluid flow path, for transmitting an ultrasonic pulse signal through the fluid flow path based on an oscillation signal, or A first transmitting / receiving unit that receives the ultrasonic pulse signal and outputs an original detection signal; and an ultrasonic pulse that is disposed downstream of the fluid flow path and passes through the fluid flow path based on the oscillation signal. A second transmission / reception unit that transmits a signal or receives the transmitted ultrasonic pulse signal and outputs an original detection signal; an oscillation unit that generates and outputs the oscillation signal based on the trigger signal; Amplification means for amplifying the detection signal and outputting it as a detection signal; switching means for alternately connecting the oscillation means to one of the first transmission / reception means and the second transmission / reception means and the amplification means to the other; signal Zero-cross detection means for performing zero-cross detection and outputting a zero-cross detection signal; timer means for outputting a detection control signal at a timing delayed from the output timing of the trigger signal by a predetermined time t0; An AND circuit that takes a logical product of control signals and outputs a flow rate detection signal; measuring means for measuring the propagation time based on the output timing of the trigger signal and the output timing of the flow rate detection signal; A first propagation time when the ultrasonic pulse signal is propagated from the means to the second transmitting / receiving means, and a second propagation time when the ultrasonic pulse signal is propagated from the second transmitting / receiving means to the first transmitting / receiving means Flow rate calculating means for calculating the flow rate of the fluid based on time; and an ultrasonic flow meter. 5. The ultrasonic flowmeter according to claim 4, wherein the predetermined time t0 is a first stable region where the detection signal can be stably detected when the flow velocity of the fluid is maximum within a measurement range. An ultrasonic flowmeter, wherein the detection signal is determined based on a second stable region in which the detection signal can be stably detected when the flow velocity of the fluid is minimized within the measurement range. 6. The ultrasonic flowmeter according to claim 5, wherein the predetermined time t0 is such that a shift in detection timing is within one wavelength in the first stable region and the second stable region. An ultrasonic flowmeter wherein the resonance frequencies of the first transmitting / receiving means and the second transmitting / receiving means are determined. 7. An ultrasonic pulse signal is transmitted by a transmitting-side vibrator through a fluid flow path, the ultrasonic pulse signal is received by a receiving-side vibrator, and the transmission timing of the ultrasonic pulse signal and the ultrasonic pulse signal are transmitted. In the propagation time measurement method of measuring the propagation time based on the signal state of the sound pulse signal, the receiving-side vibrator performs zero-cross detection of a detection signal output by receiving the ultrasonic pulse signal, and performs a zero-cross detection signal. A zero-cross detection step to generate; a detection control signal output step to output a detection control signal at a timing delayed by a predetermined time from the transmission timing of the ultrasonic pulse signal; and taking a logical product of the zero-cross detection signal and the detection control signal AND operation, based on the transmission timing of the ultrasonic pulse signal and the output timing of the flow rate detection signal Propagation time measuring method characterized by comprising a, a measuring step of measuring the propagation time. 8. A zero-crossing detection step of performing a zero-crossing detection of a detection signal obtained by receiving an ultrasonic pulse signal transmitted through a fluid flow path at a predetermined transmission timing to generate a zero-crossing detection signal; A detection control signal output step of outputting a detection control signal at a timing delayed by a predetermined time from the timing; a logical AND step of taking a logical product of the zero cross detection signal and the detection control signal and outputting a flow rate detection signal; A measurement step of measuring the propagation time based on the transmission timing of the sound wave pulse signal and the output timing of the flow rate detection signal. 9. A trigger output unit for outputting a trigger signal for controlling output timing of an ultrasonic pulse,
It is arranged on the upstream side of the fluid flow path, transmits an ultrasonic pulse signal through the fluid flow path based on an oscillation signal, or receives the transmitted ultrasonic pulse signal and outputs an original detection signal. A first transmitting / receiving unit and an ultrasonic pulse signal that is disposed downstream of the fluid flow path and transmits an ultrasonic pulse signal through the fluid flow path based on an input oscillation signal, or transmitted from the outside. A second transmitting / receiving unit that receives the ultrasonic pulse signal and outputs an original detection signal; an oscillation unit that generates and outputs the oscillation signal based on the trigger signal; and amplifies the original detection signal and outputs the amplified detection signal as a detection signal. And a switching unit for alternately connecting the oscillation unit to one of the first transmission / reception unit means and the second transmission / reception unit and the other to the amplification means. In the control method of the flowmeter, a zero-cross detection step of performing zero-cross detection of the detection signal to output a zero-cross detection signal, and a logic of calculating a logical product of the zero-cross detection signal and the detection control signal to output a flow detection signal A measuring step of measuring the propagation time based on an output timing of the trigger signal and an output timing of the flow rate detection signal; and transmitting the ultrasonic pulse signal from the first transmitting / receiving unit to the second transmitting / receiving unit. A flow rate calculating step of calculating the flow rate of the fluid based on a first propagation time when the ultrasonic pulse signal is propagated from the second transmission / reception unit to the first transmission / reception unit when the ultrasonic pulse signal is transmitted to the first transmission / reception unit. A method for controlling an ultrasonic flowmeter, comprising: