JPH1073463A - Method for measuring flow velocity using ultrasonic wave - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely recognize and catch a plurality of waves of receiving waves and secure sufficient measurement accuracy, by impressing a plurality of phase adjustment pulses of the same frequency as a resonant frequency of an ultrasonic transmitting receiving element after a driving pulse. SOLUTION: Subsequent to a first wave P of a driving pulse, phase adjustment pulses Pf of the same or approximately the same frequency as a resonant frequency of an ultrasonic transmitting receiving element are impressed to the ultrasonic transmitting receiving element. In consequence, vibrations of the phase adjustment pulses Pf are overlapped and added to a vibration by the first wave P, so that the vibrations are continued without being attenuated while the phase adjustment pulse Pf is output. Received waves W, W' are accordingly not attenuated suddenly showing a waveform with a uniformed phase and an amplitude necessary for measurements secured. Propagation time differences t1-t5 are measured by comparing reach timings of first - fifth waves W1-W5, thereby to obtain five measurement data. A flow velocity of a fluid is obtained from an averaged propagation time difference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic flow velocity measuring method for measuring the flow velocity of gas or other fluid using ultrasonic waves.

[0002]

2. Description of the Related Art When determining the flow rate of a gas or other fluid, the flow rate of the fluid is measured continuously or periodically, and the flow rate is calculated based on the measured flow rate. As one of such fluid flow velocity measuring methods, a method using ultrasonic waves is known.

FIG. 2 shows the principle of such an ultrasonic flow velocity measuring method.
The description is as follows. In FIG.
(1) is a pipeline through which a fluid such as gas flows in the direction of the arrow. In the pipeline (1), the transducers (2) and (3) are arranged at a predetermined distance upstream and downstream in the flow direction.

Each of the transducers (2) and (3) serves as both a transmitter and a receiver, and includes an ultrasonic transmitting / receiving element (not shown) composed of a vibrator. When the transmitting / receiving element is driven by the driving pulse from the pulse generation circuit (4) and vibrates to generate and transmit an ultrasonic wave, while receiving the transmitted ultrasonic wave and the ultrasonic transmitting / receiving element vibrates. Is output as an electric signal from the amplifier circuit (5).

The propagation time until the ultrasonic wave transmitted from the upstream transducer (2) in the forward direction to the flow is received by the downstream transducer (3), and the downstream The difference between the propagation time until the ultrasonic wave transmitted in the opposite direction to the flow from the transmitter (3) and the ultrasonic wave received by the upstream transducer (2) is related to the flow velocity. , The flow velocity of the fluid is measured.
In FIG. 2, (6) indicates each transducer (2) (3)
And a switching circuit for switching the connection between the pulse generation circuit (4) and the amplification circuit (5). First, the pulse generation circuit (4), the upstream-side transducer (2), and the downstream-side transducer (3) After the amplifier circuit (5) is connected and the propagation time from the upstream side to the downstream side is measured, the pulse generating circuit (4) and the downstream transducer (3) are operated by the operation of the switching circuit (6). The transmission / reception device (2) on the upstream side and the amplifier circuit (5) are switched so as to be connected, and the propagation time from the downstream side to the upstream side is measured.

[0006] By the way, the propagation time difference of the ultrasonic waves as described above is conventionally based on the first wave of the received wave output from the amplifier circuit (5) via the mutual transducers (2) and (3). Was measured. More specifically, the time difference at the time when the first wave of the received wave reaches the reference phase (reference voltage) has been measured.

However, if the propagation time difference is measured based on only the first wave of the received wave as described above to measure the flow velocity, only one measurement data can be obtained, so that the reliability is slightly increased. There was a disadvantage of lacking.

[0008]

Therefore, a plurality of first waves, second waves,... Of the received waves output from the amplifier circuit (5) via the mutual transducers (2) and (3). A method is conceivable in which the time difference when each of the waves reaches a reference phase (reference voltage) is measured, a plurality of measurement data is obtained, and the measured data is averaged to determine the propagation time difference of the ultrasonic wave. ,
Conventionally, since the drive pulse applied to the ultrasonic wave transmitting elements of the transducers (2) and (3) is single, there are the following problems.

That is, when a single drive pulse transmitted from the pulse generation circuit (4), for example, a rectangular drive pulse P shown by a chain line in FIG. The sound wave transmitting element vibrates and an ultrasonic wave corresponding to the vibration is output, and a reception wave as shown by a solid line in FIG. 4 is output to the amplifier circuit (5). This received wave is the first wave (W
1) The phase of the initial wave such as the second wave (W2) is uniform and the amplitude is sufficient, but the received wave is attenuated immediately, so that the phase of the subsequent waves gradually increases. The variation and the amplitude also become small.

As described above, since the received wave output to the amplifier circuit (5) is immediately attenuated, the above-described method of obtaining the propagation time difference, that is, the first wave, the second wave,
... A method of measuring the time difference at the time when a plurality of waves reach a reference phase (reference voltage), obtaining a plurality of data, and averaging them to obtain a propagation time difference of the ultrasonic wave. There is a drawback in that it is difficult to reliably recognize and capture a plurality of waves necessary for using the hologram.

The present invention has been made in view of such a technical background, and an ultrasonic flow velocity measurement capable of reliably recognizing and capturing a plurality of waves in a received wave, and ensuring sufficient measurement accuracy. The purpose is to provide a method.

[0012]

In order to achieve the above object, the present invention provides a drive pulse applied to an ultrasonic transmitting element so as to equalize the phase of a received wave and to secure an amplitude required for measurement. The transmission method was devised.

That is, according to the present invention, a transmitter and a receiver are arranged on the upstream side and the downstream side of the measurement fluid, respectively, and a driving pulse is applied to the ultrasonic wave transmitting element of each of the transmitters to mutually supersonic. An ultrasonic flow velocity measuring method for generating and transmitting a sound wave, mutually receiving the transmitted ultrasonic waves by a receiver, and measuring a flow velocity based on a difference in propagation time of the ultrasonic waves obtained from a comparison of the received waves. Wherein a plurality of phase matching pulses having the same or substantially the same frequency as the resonance frequency of the ultrasonic transmitting element and the ultrasonic receiving element are applied after the driving pulse.

The waveform of the driving pulse may be the same rectangular wave or triangular wave as the waveform of a conventional single-shot driving pulse, and the waveform of a plurality of phase matching pulses transmitted after the driving pulse is preferably rectangular. It is not particularly limited.

As described above, by applying a plurality of phase matching pulses having the same or substantially the same frequency as the resonance frequency of the ultrasonic transmitting element and the ultrasonic receiving element after the driving pulse, the ultrasonic transmitting element The vibration due to the phase matching pulse is added to the vibration component due to the driving pulse, and the vibration is continued without attenuating while the phase matching pulse is being output. Therefore, the phase of the received wave is made uniform and has an amplitude necessary for measurement, so that a plurality of waves in the received wave can be reliably recognized and captured. As a result, a method of obtaining a more reliable propagation time difference than the conventional method, that is, the first wave, the second wave,
... A method of measuring the time difference at the time when a plurality of waves reach a reference phase (reference voltage), obtaining a plurality of data, and averaging them to obtain a propagation time difference of the ultrasonic wave. Can be used.

[0016]

Next, one embodiment of the present invention will be described. FIG. 2 shows an ultrasonic flow velocity measuring device for carrying out the present invention. In FIG. 2, (1) is a pipeline, (2) and (3) are transducers arranged at a predetermined distance upstream and downstream in a flow direction, and (4) is a pulse generator for generating a drive pulse. Circuit, (5) is a transducer (2)
An amplifier circuit for outputting the received wave received in (3), (6) a switching circuit for switching the connection between each of the transducers (2) and (3), the pulse generator circuit (4) and the amplifier circuit (5); These are the same as those shown in FIG.

Further, in this embodiment, the amplifier circuit (5)
A zero-crossing detection circuit (7) is provided on the output side of. This zero-cross detection circuit (7) includes an amplification circuit (5)
Immediately after the reception wave is output from the amplifying circuit (5)
Is detected at the timing of the arrival times T1 and T1 'for the first wave, for example, and this is used as the reception wave arrival timing. By utilizing this, even when the reference voltage fluctuates, the timing of the zero-cross does not fluctuate, so that the timing of arrival of the received wave does not fluctuate, and thus more accurate flow velocity measurement can be performed.

Next, an ultrasonic measuring method according to the present invention using the apparatus shown in FIG. 2 will be described. First, in order to drive the ultrasonic wave transmitting element in the transmitter / receiver (2) on the upstream side of the fluid, as shown by a chain line in FIG. 1, a first wave () of the drive pulse output from the pulse generation circuit (4). P) is a rectangular wave, and after the first wave (P), a rectangular phase matching pulse (Pf) having a frequency equal to or substantially the same as the resonance frequency of the ultrasonic transmitting element and the ultrasonic receiving element is generated by a pulse generation circuit. A plurality is output from (4). When such a drive pulse is applied to the ultrasonic transmitting element in the transducer (2) on the upstream side of the fluid, the ultrasonic transmitting element is superimposed on the vibration component due to the first wave and the vibration due to the phase matching pulse is generated. Therefore, the vibration is continued without attenuating while the phase matching pulse is being output. Accordingly, a received wave (W) having a waveform as shown by the solid line in FIG. 1 is output from the amplifier circuit (5) in response to the vibration of the ultrasonic transmission element. The received wave (W) has a uniform phase without abrupt attenuation, and has a waveform in which the amplitude required for measurement is secured.

The number of time difference measurement data required to derive the propagation time difference (phase difference) is assumed to be 5, and the received wave (W) output from the amplifier circuit (5) by the zero-cross detection circuit (7) by the zero-cross detection circuit (7). Are detected at the timings of arrival times T1, T2,..., T5 as shown in FIG. 1, and this is used as the arrival timing of the received wave (W). Since the phase of the received wave (W) is uniformed and the amplitude is sufficiently ensured, each wave of the received wave (W) can be reliably captured, and therefore, T1, T2,. The arrival timing can be determined accurately.

Next, in order to switch the connection by the switching circuit (6) and drive the ultrasonic wave transmitting element in the transducer (3) on the downstream side of the fluid, the same driving as described above is performed from the pulse generating circuit (4). When the pulse P and the phase matching pulse Pf are output, a reception wave (W ') having a waveform as shown by a broken line in FIG. 1 is output from the amplifier circuit (5) in the same manner as the reception wave (W).

In the same manner as described above, the number of measurement data of the time difference necessary for deriving the propagation time difference (phase difference) is set to five, and the data is output from the amplifier circuit (5) by the zero-cross detection circuit (7). As shown in FIG. 1, the zero cross of the received wave (W ') reaches the arrival times T1', T2 ',.
5 ′, and the received wave (W
)).

Thus, the two received waves (W) obtained
(W ') has propagation time differences (phase differences) t1, t2,..., T5 that vary according to the fluid flow velocity as shown in FIG. 1, so that each received wave (W) (W') ) First
Half-wave (W1) (W1 '), second half-wave (W2) (W2
),..., The fifth half-waves (W5) (W5 ') are compared to determine the propagation time differences t1, t2.
,..., T5 are measured to obtain five pieces of measurement data, the fluid velocity is obtained from the averaged propagation time difference, and the flow rate is obtained as necessary. Further, when it is necessary to measure the fluid flow velocity continuously or periodically, the above operation may be repeated continuously or periodically at predetermined intervals.

In the above embodiment, the arrival timing of the received wave is set to the zero cross point. However, the setting of the arrival timing of the received wave is not limited to this. The arrival timing of the received wave may be determined when the phase is reached. Furthermore, one transducer is provided for each of the upstream and downstream sides of the fluid flow, and the connection is switched by a switching circuit, so that transmission from the upstream side to the downstream side and transmission from the downstream side to the upstream side are sequentially performed. Although the case of performing is shown, the transmitter and the receiver are separately provided on the upstream side and the receiver and the transmitter are separately provided on the downstream side, so that the measurement of the propagation time can be performed. It may be performed simultaneously.

[0024]

According to the present invention, as described above, a transmitter and a receiver are arranged on the upstream side and the downstream side of the measurement fluid, respectively.
The drive pulse was applied to the ultrasonic wave transmitting elements of the respective transmitters to generate and transmit ultrasonic waves to each other, and the transmitted ultrasonic waves were mutually received by the receiver, and were obtained by comparing the received waves. In the ultrasonic flow velocity measuring method for measuring the flow velocity based on the difference in the propagation time of the ultrasonic wave, the drive pulse is a rectangular wave,
After the drive pulse, it is characterized by applying a plurality of phase matching pulses of the same or substantially the same frequency as the resonance frequency of the ultrasonic transmission element and the ultrasonic reception element, when the drive pulse is a single shot In contrast, the received wave output to the amplifier circuit does not attenuate immediately, becomes a vibration waveform with the uniform phase and the amplitude required for measurement,
A plurality of received waves can be reliably recognized and captured. As a result, in order to determine the propagation time difference of the received wave, the respective time differences when a plurality of waves of the first wave, the second wave,... Of the received wave reach the reference phase (reference voltage) are measured. By obtaining a plurality of measurement data and averaging them, it is possible to use a method of obtaining a propagation time difference of an ultrasonic wave. The reliability of the propagation time difference is higher than that of the method for determining the velocity, and the flow velocity measurement with higher measurement accuracy can be performed.

[Brief description of the drawings]

FIG. 1 is a waveform diagram showing a relationship between a drive pulse applied to an ultrasonic wave transmitting element of a transmitter and a received wave in the present invention.

FIG. 2 is a schematic configuration diagram of an ultrasonic flow velocity measuring circuit used in an embodiment of the present invention.

FIG. 3 is a schematic configuration diagram for explaining the principle configuration of ultrasonic flow velocity measurement.

FIG. 4 is a waveform chart showing a relationship between a drive pulse applied to an ultrasonic wave transmitting element of a transmitter and a received wave in a conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Piping 2, 3 ... Transceiver 4 ... Pulse generation circuit 5 ... Amplification circuit P ... Drive pulse W, W '... Received wave

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akio Tomita 4-1-2, Hirano-cho, Chuo-ku, Osaka-shi Inside Osaka Gas Co., Ltd. Kansai Gas Meter Co., Ltd. (72) Eiji Nakamura, Inventor 2- 10-16 Higashi-Kobashi, Higashi-Nari-ku, Osaka-shi Kansai Gas Meter Co., Ltd. Inside the corporation

Claims (1)

[Claims] 1. A transmitter and a receiver are arranged on an upstream side and a downstream side of a measurement fluid, respectively, and a driving pulse is applied to an ultrasonic transmitting element of each of the transmitters to generate and transmit ultrasonic waves mutually. While receiving the transmitted ultrasonic waves with each other,
In the ultrasonic flow velocity measuring method for measuring the flow velocity based on the difference in the propagation time of the ultrasonic wave obtained from the comparison of each received wave, after the driving pulse, the same as the resonance frequency of the ultrasonic transmitting element and the ultrasonic receiving element Or an ultrasonic flow velocity measuring method, wherein a plurality of phase matching pulses having substantially the same frequency are applied.