JP7151311B2 - ultrasonic flow meter - Google Patents

Description

The present invention relates to ultrasonic flowmeters.

Ultrasonic waves are used to measure the flow rates of liquids and gases (hereinafter referred to as "fluids") flowing in pipes.

As one of the measurement principles, the propagation time reciprocal difference method is known. FIG. 7 is a schematic diagram showing a conventional ultrasonic measurement method. As shown in FIG. 7, a pair of ultrasonic sensors 72 and 73 for both transmission and reception are arranged in a conduit 71 to alternately transmit and receive ultrasonic pulses. Consider the propagation time of the ultrasonic pulse only in the conduit 71 . Let L be the propagation path length of the ultrasonic pulse in the conduit 71, C be the speed of sound in the fluid 74 in the conduit 71, and θ be the angle between the central axis of the conduit 71 and the propagation axis of the ultrasonic pulse. A sound velocity Co of an ultrasonic pulse that travels between the ultrasonic sensors 72 and 73 is affected by the flow velocity V and is expressed by Equation (1).

Here, the propagation time of the ultrasonic pulse in the conduit 71 is td in the forward direction (direction from the ultrasonic sensor 72 to the ultrasonic sensor 73), and td in the reverse direction (from the ultrasonic sensor 73 to the ultrasonic sensor 72). Let tu be the time of the heading direction). The propagation times td and tu are expressed by the following equations.

Taking the reciprocals of Equations 2 and 3, calculating the difference, and arranging them gives Equation 4.

That is, by measuring the propagation times td and tu, the flow velocity V of the fluid 74 flowing through the conduit 71 can be obtained. By multiplying the flow velocity V by the cross-sectional area A of the conduit 71, the flow rate Q of the fluid 74 can be obtained.

An ultrasonic flowmeter using such a propagation time reciprocal difference method uses ultrasonic sensors 72 and 73 for both transmission and reception. Therefore, it is necessary to provide a changeover switch for alternately switching the output destination of the transmission circuit and the input source of the reception circuit between the ultrasonic sensors 72 and 73 . In addition, since a transmission circuit that handles high voltage and a reception circuit that handles weak signals are connected via a changeover switch, a high voltage signal leaks from the transmission circuit to the reception circuit, which causes noise. In order to prevent this, in the receiving circuit, it is necessary to provide a clamp circuit to extract only weak signals from the input signal and amplify the received signal by an amplifier circuit. Thus, conventional ultrasonic flowmeters are subject to circuit design restrictions.

Also, the ultrasonic sensors 72 and 73 are used for both transmission and reception of ultrasonic waves, that is, they alternately transmit and receive ultrasonic waves. For this reason, the frequency of ultrasonic waves must be selected so that the sensitivity of transmission and reception is intermediate, or selected so that either the sensitivity of transmission or reception is high. In other words, for example, the resonance frequency of the ultrasonic sensor 72 during transmission cannot match the anti-resonance frequency of the ultrasonic sensor 73 during reception.

Moreover, the directivity of the ultrasonic sensors 72 and 73 cannot be differentiated. For example, if an ultrasonic sensor with wide directivity is used to increase the reception sensitivity, the transmission sensitivity will decrease.

An ultrasonic flowmeter that does not use an ultrasonic sensor for both transmission and reception has been proposed (see, for example, Patent Document 1).

In the ultrasonic flowmeter of Patent Document 1, ultrasonic signals are emitted from one transmitting ultrasonic sensor (transducer) in a plurality of directions in a pipe, and the respective ultrasonic signals are received by a plurality of receiving ultrasonic sensors. Then, the flow rate in the pipe is measured based on the received signal only from the receiving ultrasonic sensor.

JP-A-2001-356034

However, in the ultrasonic flowmeter of Patent Document 1, paths of ultrasonic pulses for measuring the propagation times tu and td are different. Therefore, since the propagation path length L in the above equations 2 and 3 is different, it causes an error in the flow rate measurement.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is an object of the present invention to provide an ultrasonic flowmeter that has a high degree of freedom in circuit design, high sensitivity, and little error.

One aspect of the ultrasonic flowmeter of the present invention includes an upstream transmission sensor and a downstream transmission sensor that transmit ultrasonic pulses toward a fluid in a pipeline, and the upstream transmission sensor and the downstream transmission sensor of the pipeline. At least two receiving sensors sequentially attached along the flow direction of the fluid between the side transmitting sensor and a time difference for measuring the time difference between the received signals at any two of the at least two receiving sensors. and a measurement unit, wherein the time difference when the ultrasonic pulse is transmitted from the upstream transmission sensor is taken as a forward propagation time, and the time difference when the ultrasonic pulse is transmitted from the downstream transmission sensor is taken as a backward propagation time. a calculation unit for calculating a flow rate of the fluid based on the forward propagation time and the backward propagation time, and detecting a peak value of the received signal from any two of the at least two receiving sensors; and a peak value detector , wherein each of the at least two receiving sensors receives the incident ultrasonic pulse and outputs the received signal, and the other adjacent one of the The ultrasonic pulse is reflected toward the receiving sensor, and the calculating section obtains the pressure of the fluid using the ratio of the two peak values detected by the peak value detecting section .

According to one aspect of the present invention, it is possible to provide an ultrasonic flowmeter that has a high degree of freedom in circuit design, high sensitivity, and few errors.

1 is a schematic configuration diagram of an ultrasonic flowmeter according to a first embodiment; FIG. 2 is a schematic configuration diagram of a control circuit in the ultrasonic flowmeter according to the first embodiment; FIG. 1 is a schematic configuration diagram of an ultrasonic flowmeter according to a first embodiment; FIG. FIG. 2 is a schematic configuration diagram of an ultrasonic flowmeter according to a second embodiment; FIG. FIG. 7 is a schematic configuration diagram of a control circuit in an ultrasonic flowmeter according to a second embodiment; FIG. 11 is a schematic configuration diagram of an ultrasonic flowmeter according to a third embodiment; It is a schematic diagram which shows the conventional ultrasonic measurement method.

As a result of intensive studies to solve the above problems, the inventors of the present invention have found that an ultrasonic pulse transmitted from a transmitting ultrasonic sensor is reflected by a receiving ultrasonic sensor. By making the propagation path of the ultrasonic pulse when measuring the propagation time and the propagation path of the ultrasonic pulse when measuring the propagation time in the opposite direction the same, although the direction is opposite, the error of the flow rate measurement is reduced. The inventors have found that it can be suppressed, and completed the present invention.

That is, one aspect of the ultrasonic flowmeter of the present invention includes an upstream transmission sensor and a downstream transmission sensor that transmit ultrasonic pulses toward a fluid in a pipeline, and the upstream transmission sensor of the pipeline. At least two receiving sensors sequentially attached along the flow direction of the fluid between the downstream transmitting sensor and measuring the time difference between the received signals at any two of the at least two receiving sensors. and a time difference measuring unit that defines the time difference when the ultrasonic pulse is transmitted from the upstream transmission sensor as a forward propagation time, and the time difference when the ultrasonic pulse is transmitted from the downstream transmission sensor. and a calculation unit that calculates the flow rate of the fluid based on the forward propagation time and the backward propagation time, and the at least two receiving sensors each receive the incident ultrasonic wave. It is characterized by receiving a sound wave pulse and outputting the received signal, and reflecting the ultrasonic pulse toward another of the receiving sensors arranged one next to the other.

With the configuration as described above, according to one aspect of the present invention, it is possible to provide an ultrasonic flowmeter with a high degree of freedom in circuit design, high sensitivity, and little error.

(First embodiment)
An ultrasonic flowmeter according to the first embodiment will be described below. FIG. 1 is a schematic configuration diagram of an ultrasonic flowmeter according to the first embodiment. The ultrasonic flowmeter shown in FIG. 1 is a clamp-on type in which an ultrasonic sensor is mounted on an existing pipeline. In FIG. 1, an ultrasonic pulse and various signals are illustrated with an example of measuring a forward propagation time td (described later).

As shown in FIG. 1, an ultrasonic flowmeter 10 has two transmission ultrasonic sensors (hereinafter simply referred to as transmission sensors) 12 and 13 attached to the outer surface of a pipeline 11 . Transmitting sensors 12 , 13 transmit ultrasonic pulses towards fluid 14 in conduit 11 .

The transmission sensors 12 and 13 are spaced apart along the axial direction when viewed in a cross section along the axial direction of the pipeline 11 (hereinafter referred to as a tube axial cross section) (hereinafter referred to as a tube axial cross section). are placed. Hereinafter, when the upstream transmission sensor 12 is described alone, it will be referred to as an upstream transmission sensor. Also, when describing the downstream transmission sensor 13 alone, it is referred to as a downstream transmission sensor.

In addition, the transmission sensors 12 and 13 are positioned symmetrically about the central axis O of the pipeline 11 when viewed in a cross section orthogonal to the axial direction of the pipeline 11 (hereinafter referred to as an orthogonal cross section). are placed. Note that the positional relationship of the transmission sensors 12 and 13 when viewed in an orthogonal cross section is not limited to point symmetry. There is no particular limitation as long as it can be received by the other sensor after being reflected by a receiving sensor (described later).

The transmission sensors 12, 13 comprise, for example, ultrasonic transducers made of piezoelectric ceramics. When voltage is applied to the ultrasonic transducer, it vibrates and emits ultrasonic waves. By appropriately selecting the size and shape of the ultrasonic transducer, the resonance frequency and directivity can be controlled.

In addition, the transmission sensors 12 and 13 are arranged so that the ultrasonic waves can be incident at an angle to the central axis O of the conduit 11 in order to utilize the reflection of the ultrasonic waves at the receiving sensors as will be described later. It is attached obliquely to the outer surface of the pipeline 11 .

Between the transmitting sensors 12 and 13, two receiving ultrasonic sensors (hereinafter simply referred to as receiving sensors) 15 and 16 are arranged.

Each of the receiving sensors 15 and 16 can receive an ultrasonic pulse emitted from one of the transmitting sensors 12 and 13, and reflect the ultrasonic pulse toward the other adjacent one. are arranged to Reflection will be discussed later.

More specifically, in the first embodiment, a receiving sensor 15 is located upstream and a receiving sensor 16 is located downstream between the transmitting sensors 12 and 13 along the axial direction in a cross-sectional view of the tube axis. are placed. Hereinafter, when the receiving sensor 15 on the upstream side is described alone, it is referred to as the first receiving sensor. Also, when the receiving sensor 16 on the downstream side is described alone, it is referred to as a second receiving sensor.

Further, the receiving sensors 15 and 16 are arranged at point-symmetrical positions with respect to the central axis O of the pipeline 11 when viewed in an orthogonal cross section. Here, the positional relationship of the transmitting sensors 12 and 13 when viewed in an orthogonal cross section is not limited to point symmetry, as long as ultrasonic waves reflected by one of the receiving sensors 15 and 16 can be received by the other. is not particularly limited.

The receiving sensors 15, 16 are provided with ultrasonic transducers made of piezoelectric ceramics, for example. Due to the vibration applied to the ultrasonic transducer, an electromotive force corresponding to the vibration is generated between the electrodes and output as a reception signal. Therefore, the wall of the conduit 11 where the ultrasonic pulse impinges on the inner surface of the conduit 11 vibrates. This vibration is transmitted through the walls to the ultrasonic transducers of the receiving sensors 15 and 16, which generates an electromotive force and outputs a reception signal.

Also, the receiving sensors 15 and 16 can control the anti-resonant frequency and directivity by appropriately selecting the size and shape of the ultrasonic transducer.

Next, referring to FIG. 1, the circuit configuration in the first embodiment will be described. The transmission sensors 12 and 13 are electrically connected to the transmission circuit 21 . The upstream transmission sensor 12 is connected to the first output terminal a of the transmission circuit 21, and the downstream transmission sensor 13 is connected to the second output terminal b of the transmission circuit 21, respectively.

The transmission circuit 21 applies a high voltage to the ultrasonic oscillators of the transmission sensors 12 and 13 to oscillate ultrasonic waves. The transmission circuit 21 is electrically connected to the control circuit 22 .

FIG. 2 is a schematic configuration diagram of a control circuit in the ultrasonic flowmeter according to the first embodiment. The control circuit 22 has a transmission control section 221 , a calculation section 222 and an output section 223 .

Here, the control circuit 22 is, for example, an integrated circuit that executes various processes. However, instead of the control circuit 22, a control device configured by a processor, memory, etc., for executing various processes may be used. The memory is composed of one or more storage media such as ROM (Read Only Memory), RAM (Random Access Memory), etc., depending on the application. The memory stores programs for executing various processes.

The transmission control section 221 of the control circuit 22 is configured to output a transmission start signal to the transmission circuit 21 and cause the transmission circuit 21 to output a burst signal from either one of the output terminals a and b.

On the other hand, amplifier circuits 23 and 24 are electrically connected to the receiving sensors 15 and 16, respectively. The received signals amplified by the amplifier circuits 23 and 24 are input to a time difference measurement circuit 25, which is an example of the time difference measurement section of the present invention.

The time difference measuring circuit 25 measures the time difference between the ultrasonic waves detected by the receiving sensors 15 and 16 based on the received signals input from the receiving sensors 15 and 16 . The time difference measurement circuit 25 is electrically connected to the control circuit 22 .

In the control circuit 22, the calculation unit 222 calculates the flow velocity V of the fluid 14 based on the propagation times td and tu (described later) measured by the time difference measurement circuit 25. FIG. Further, the calculation unit 222 multiplies the flow velocity V by the cross-sectional area A of the pipeline 11 to obtain the flow rate Q. FIG.

Also, the output unit 223 causes the display unit 26 to display the calculation result of the calculation unit 222 . The output unit 223 may transmit the calculation result to an external recording device such as a paperless recorder via a communication path for recording.

Next, flow measurement in the ultrasonic flowmeter according to the first embodiment will be described with reference to FIGS. 1 and 3. FIG. First, the measurement of the forward propagation time td will be described with reference to FIG. In FIG. 1, the propagation paths of ultrasonic pulses are indicated by dashed lines with arrows.

First, the transmission control section 221 of the control circuit 22 outputs a transmission start signal to the transmission circuit 21 . This transmission circuit signal includes an instruction to cause the transmission circuit 21 to output a burst signal from the output terminal a. As a result, a burst signal of frequency f is input from the transmission circuit 21 to the upstream transmission sensor 12 .

In the upstream transmission sensor 12, the ultrasonic oscillator vibrates in response to the burst signal to generate ultrasonic pulses of frequency f. The ultrasonic pulses vibrate the walls of conduit 11 and reach fluid 14 . The ultrasonic pulse that reaches the fluid 14 propagates through the fluid 14 toward the first receiving sensor 15 .

The ultrasonic pulse then impinges on the inner surface of the conduit 11, causing the wall of the conduit 11 to vibrate. This vibration reaches the ultrasonic transducer of the first receiving sensor 15, and the ultrasonic transducer vibrates. At this time, an electromotive force is generated in the ultrasonic transducer, and the received signal is output to the amplifier circuit 23 .

The vibration of the ultrasonic transducer not only generates an electromotive force, but also vibrates the wall of the conduit 11 again. This vibration reaches the fluid 14 and propagates through the fluid 14 . As a result, the ultrasonic pulse changes direction at the first receiving sensor 15 and behaves as if it were emitted at approximately the same angle as the incident angle. In this specification, such ultrasonic pulse behavior is referred to as "reflection." The ultrasonic pulse reflected by the first receiving sensor 15 propagates through the fluid 14 toward the second receiving sensor 16 .

The ultrasonic pulse impinges on the inner surface of the conduit 11 , vibrates the wall of the conduit 11 and reaches the ultrasonic transducer of the second receiving sensor 16 . At this time, an electromotive force is generated in the ultrasonic transducer, and the received signal is output to the amplifier circuit 24 .

Reflection of the ultrasonic pulse also occurs in the second receiving sensor 16 as in the first receiving sensor 15 described above. The ultrasonic pulse reflected by the second receiving sensor 16 returns into the fluid 14 and propagates toward the downstream transmitting sensor 13 . As a result, the ultrasonic pulse propagates through the fluid 14 in a generally N-shaped propagation path, as shown in FIG.

The time difference measuring circuit 25 measures the time difference between the signal received by the first sensor 15 and the signal received by the second sensor 16 . A correlation method, for example, is used to measure the time difference. The correlation method calculates the cross-correlation function of the waveform data of two received signals, and obtains from the time shift amount corresponding to the maximum value. The time difference measuring circuit 25 outputs the measured time difference to the control circuit 22 . The calculation unit 222 (see FIG. 2) of the control circuit 22 treats the time difference when the ultrasonic pulse is transmitted from the upstream transmission sensor 12 as the forward propagation time td.

In the received signal input to the time difference measuring circuit 25, in addition to the waveform (A) caused by the reflection of the ultrasonic pulse on the receiving sensors 15 and 16, there are also waveforms caused by the reflection of the ultrasonic pulse on the inner surface of the conduit 11 It contains a waveform (B) that For this reason, the time difference measuring circuit 25 can consider, for example, the following method for distinguishing between them. The ultrasonic pulse hits the inner surface of the conduit 11 before the receiving sensors 15 and 16 . Therefore, waveform (B) always appears earlier than waveform (A). Therefore, the time difference measurement circuit 25 should use the next waveform (A) instead of the first waveform (B) to measure the time difference.

When the wall of the conduit 11 is thin, spacers are placed between the outer surface of the conduit 11 and the receiving sensors 15 and 16 so that the waveforms (A) and (B) do not overlap. It is preferable to increase the distance between the inner surface and the receiving sensors 15,16.

Next, the measurement of the backward propagation time tu will be described with reference to FIG. FIG. 3 is a schematic configuration diagram of an ultrasonic flowmeter according to the first embodiment. In FIG. 3, the ultrasonic pulse and various signals are illustrated by taking the case of measuring the backward propagation time tu as an example. Also, in FIG. 3, the propagation path of the ultrasonic pulse is indicated by a dotted line with an arrow.

First, the transmission control section 221 of the control circuit 22 outputs a transmission start signal to the transmission circuit 21 . This transmission circuit signal includes an instruction to cause the transmission circuit 21 to output a burst signal from the output terminal b. As a result, a burst signal is input from the transmission circuit 21 to the downstream transmission sensor 13 .

In the downstream transmission sensor 13, the ultrasonic oscillator vibrates according to the burst signal to generate ultrasonic pulses. The ultrasonic pulses vibrate the walls of conduit 11 and reach fluid 14 . The ultrasonic pulse that reaches the fluid 14 propagates through the fluid 14 toward the second receiving sensor 16 .

The ultrasonic pulses then impinge on the inner surface of conduit 11 . The ultrasonic pulse vibrates the wall of the conduit 11 and reaches the ultrasonic transducer of the second receiving sensor 16 . At this time, an electromotive force is generated in the ultrasonic transducer, and the received signal is output to the amplifier circuit 24 .

At the second receiving sensor 16 reflection of the ultrasound pulse occurs in the same way as described with reference to FIG. The ultrasonic pulse reflected by the second receiving sensor 16 propagates through the fluid 14 toward the first receiving sensor 15 .

The ultrasonic pulses then impinge on the inner surface of conduit 11 and cause the walls of conduit 11 to vibrate. This vibration reaches the ultrasonic transducer of the first receiving sensor 15, and the ultrasonic transducer vibrates. At this time, an electromotive force is generated in the ultrasonic transducer, and the received signal is output to the amplifier circuit 23 .

Further, reflection of the ultrasonic pulse also occurs at the first receiving sensor 15 . The ultrasonic pulse reflected by the first receiving sensor 15 returns into the fluid 14 and propagates toward the upstream transmitting sensor 12 . As a result, the propagation path of the ultrasonic pulse from the downstream transmission sensor 13 to the upstream transmission sensor 12 via the second reception sensor 16 and the first reception sensor 15 follows the order described with reference to FIG. Although the direction is opposite to the propagation path when measuring the directional propagation time td, it is the same.

The time difference measuring circuit 25 measures the time difference between the signal received by the first sensor 15 and the signal received by the second sensor 16 . The time difference measuring circuit 25 outputs the measured time difference to the control circuit 22 . The calculation unit 222 (see FIG. 2) of the control circuit 22 treats the time difference when the ultrasonic pulse is transmitted from the downstream transmission sensor 13 as the backward propagation time tu.

The propagation times td and tu are thus obtained. The calculation unit 222 of the control circuit 22 calculates the flow velocity V of the fluid 14 using the above equation 4 based on the propagation times td and tu. get

As described above, when the ultrasonic flowmeter 10 according to the first embodiment measures the propagation times td and tu described with reference to FIGS. 1 and 3, the propagation path of the ultrasonic pulse is , between the receiving sensors 15, 16 and are identical but opposite in orientation. Therefore, since the propagation path lengths L in the above equations 2 and 3 are the same, errors are less likely to occur.

Further, since the ultrasonic pulse transmitted from one of the transmitting sensors 12 and 13 is reflected by one of the receiving sensors 15 and 16 and received by the other, ultrasonic waves for both transmission and reception can be used as in the conventional art. Ultrasonic pulses can travel a longer distance than when ultrasonic waves are transmitted and received between sensors. The longer the flight distance of the ultrasonic pulse, the longer the time for measuring the flow velocity, and the greater the influence of the ultrasonic pulse from the fluid 14, so that the flow velocity sensitivity can be increased. Thereby, the accuracy of the ultrasonic flowmeter 10 can be improved. Here, the flow velocity sensitivity refers to the amount of occurrence of the time difference between the propagation times td and tu corresponding to the flow velocity of the fluid.

In addition, there is no need to use an ultrasonic sensor for both transmission and reception, and a switch is not required. Further, since the transmission system circuit composed of the transmission circuit 21 and the transmission sensors 12 and 13 and the reception system circuit composed of the reception sensors 15 and 16 and the amplifier circuits 23 and 24 are independent, the output from the transmission circuit 21 is There is no possibility that the burst signal thus generated leaks into the amplifier circuits 23 and 24 and noise increases. Therefore, since it is not necessary to provide a clamp circuit in the amplifier circuits 23 and 24, it is possible to prevent the measured propagation time from fluctuating due to noise. As a result, the degree of freedom in circuit design of the ultrasonic flowmeter 10 increases.

Further, there is no need to use an ultrasonic sensor for both transmission and reception, and an ultrasonic sensor having characteristics optimized for the transmission sensors 12 and 13 or the reception sensors 15 and 16 can be used.

First, the resonant frequencies of the transmitting sensors 12 and 13 and the anti-resonant frequencies of the receiving sensors 15 and 16 can be matched. The resonance frequency and anti-resonance frequency represent the impedance characteristics of the ultrasonic sensor. The resonance frequency is the frequency at which the admittance of the ultrasonic sensor becomes maximum, and the transmission efficiency of the ultrasonic sensor increases.

On the other hand, the anti-resonance frequency is the frequency at which the admittance of the ultrasonic sensor is minimized, and the reception efficiency of the ultrasonic sensor increases.

Therefore, matching the resonance frequencies of the transmission sensors 12 and 13 with the anti-resonance frequencies of the reception sensors 15 and 16 increases the efficiency of transmission and reception of ultrasonic pulses and improves the S/N ratio of received signals. ,preferable. Accordingly, by setting the frequency f of the burst signal to the resonance frequency of the transmission sensors 12 and 13, the transmission sensitivity can be improved. Moreover, since the frequency f is also the anti-resonance frequency of the receiving sensors 15 and 16, the receiving sensitivity can be improved.

In the first embodiment, the frequencies of the ultrasonic pulses transmitted from the transmission sensors 12 and 13 are set to the resonance frequencies of the transmission sensors 12 and 13 and to the anti-resonance frequencies of the reception sensors 15 and 16. You may do either of In other words, in the first embodiment, it is not essential to match the resonance frequencies of the transmission sensors 12 and 13 with the anti-resonance frequencies of the reception sensors 15 and 16 .

Moreover, the directivity of the transmitting sensors 12 and 13 and the receiving sensors 15 and 16 can be differentiated. That is, the transmission sensors 12 and 13 narrow the directivity toward the reception sensors 15 and 16 to increase the transmission sensitivity. On the other hand, the reception sensors 15 and 16 have wide directivity to efficiently convert ultrasonic pulses from oblique directions into reception signals, thereby increasing reception sensitivity. As a result, the efficiency of transmission and reception of ultrasonic pulses can be increased, and the S/N ratio of received signals can be improved, which is preferable.

That is, in the first embodiment, it is preferable that the receiving sensors 15 and 16 have wider directivity than the transmitting sensors 12 and 13 from the viewpoint of increasing the measurement accuracy. For example, it is particularly preferable to set the directivity of the receiving sensors 15 and 16 to 45 degrees and the directivity of the transmitting sensors 12 and 13 to 30 degrees.

(Second embodiment)
An ultrasonic flowmeter according to the second embodiment will be described below. FIG. 4 is a schematic configuration diagram of an ultrasonic flowmeter according to a second embodiment. In FIG. 4, the ultrasonic pulse and various signals are illustrated by exemplifying the case of measuring the forward propagation time td (described later). In FIG. 4, the same components as in FIGS. 1 to 3 are denoted by the same reference numerals, and descriptions thereof are omitted.

The ultrasonic flowmeter 40 according to the second embodiment differs from the first embodiment in that it has three reception sensors.

The positional relationship of the transmission sensors 12 and 13 is arranged on the same side with respect to the pipeline 11, unlike the first embodiment.

Further, three reception sensors 41, 42, 43 are arranged in order from the upstream side along the flow direction between the transmission sensors 12, 13 in a cross-sectional view of the tube axis. Hereinafter, when the upstream receiving sensor 41 is described alone, it is referred to as the first receiving sensor. Also, when describing the intermediate receiving sensor 42 alone, it is referred to as a second receiving sensor. When the receiving sensor 43 on the downstream side is described alone, it is referred to as the third receiving sensor.

The reception sensors 41, 42, and 43 have the same relationship as the reception sensors 15 and 16 in the first embodiment between adjacent ones. That is, the first receiving sensor 41 and the second receiving sensor 42 can receive the ultrasonic pulse transmitted from one of the transmitting sensors 12 and 13, and transmit the ultrasonic pulse toward the other adjacent one. It is arranged to reflect ultrasound pulses.

Also, the second receiving sensor 42 and the third receiving sensor 43 can receive the ultrasonic pulse transmitted from one of the transmitting sensors 12 and 13, and transmit the ultrasonic pulse toward the other one. arranged to be reflective.

In the above description, the fact that the second receiving sensor 42 and the third receiving sensor 43 can receive the ultrasonic pulse transmitted from one of the transmitting sensors 12 and 13 means that the ultrasonic pulse is received by the other receiving sensor. Including receiving after reflection.

In the second embodiment, the reception circuitry is the same as in the first embodiment, and amplifier circuits 44, 45 and 46 are electrically connected to reception sensors 41, 42 and 43, respectively.

FIG. 5 is a schematic configuration diagram of a control circuit in the ultrasonic flowmeter 40 according to the second embodiment. The control circuit 22 includes a reception sensor selection section 224 in addition to a transmission control section 221 , a calculation section 222 and an output section 223 .

The reception sensor selection unit 224 instructs the time difference measurement circuit 25 to select any two of the reception sensors 41, 42, and 43 and measure the time difference based on the received signal output from the selected one. is configured to

Next, referring to FIG. 4, flow measurement in the ultrasonic flowmeter according to the second embodiment will be described. First, the measurement of the forward propagation time td will be described with reference to FIG. In FIG. 4, the propagation paths of ultrasonic pulses are indicated by dotted lines with arrows.

First, the transmission control section 221 of the control circuit 22 outputs a transmission start signal to the transmission circuit 21 . As a result, a burst signal of frequency f is input from the transmission circuit 21 to the upstream transmission sensor 12 .

It also outputs a sensor selection signal to the receiving sensor selection section 224 of the control circuit 22 . The sensor selection signal includes instructions to the time difference measurement circuit 25 to make time difference measurements based on the received signals from the first receiving sensor 41 and the third receiving sensor 43 .

The upstream transmission sensor 12 transmits ultrasonic pulses in response to the burst signal. The transmitted ultrasonic pulse propagates through the fluid 14 toward the first receiving sensor 41 .

The ultrasonic pulse then impinges on the inner surface of the conduit 11, causing the wall of the conduit 11 to vibrate. This vibration reaches the ultrasonic transducer of the first receiving sensor 41, and the ultrasonic transducer vibrates. At this time, an electromotive force is generated in the ultrasonic transducer, and the received signal is output to the amplifier circuit 44 .

Also, the ultrasonic pulse is reflected by the first receiving sensor 41 . The ultrasonic pulse reflected by the first receiving sensor 41 propagates through the fluid 14 toward the second receiving sensor 42 .

The ultrasonic pulse then impinges on the inner surface of the conduit 11 , vibrates the wall of the conduit 11 and reaches the ultrasonic transducer of the second receiving sensor 42 . At this time, an electromotive force is generated in the ultrasonic transducer, and the received signal is output to the amplifier circuit 45 .

Reflection of the ultrasonic pulse also occurs in the second receiving sensor 42 as in the first receiving sensor 41 described above. The ultrasonic pulse reflected by the second receiving sensor 42 returns into the fluid 14 and propagates toward the third receiving sensor 43 .

After that, the ultrasonic pulse strikes the inner surface of the conduit 11 , vibrates the wall of the conduit 11 , and reaches the ultrasonic transducer of the third receiving sensor 43 . At this time, an electromotive force is generated in the ultrasonic transducer, and the received signal is output to the amplifier circuit 46 .

Reflection of the ultrasonic pulse also occurs in the third receiving sensor 43 as in the first and second receiving sensors 41 and 42 described above. The ultrasonic pulse reflected by the third receiving sensor 43 returns into the fluid 14 and propagates toward the downstream transmitting sensor 13 . As a result, as shown in FIG. 4, the ultrasonic pulse travels from the upstream transmission sensor 12 through the first reception sensor 41, the second reception sensor 42, and the third reception sensor 43, to the downstream transmission sensor 13. It propagates in the fluid 14 along a substantially W-shaped propagation path leading to .

The time difference measuring circuit 25 measures the time difference between the signal received by the first sensor 41 and the signal received by the third sensor 43 . The time difference measuring circuit 25 outputs the measured time difference to the control circuit 22 . The calculation unit 222 (see FIG. 5) of the control circuit 22 treats the time difference when the ultrasonic pulse is transmitted from the upstream transmission sensor 12 as the forward propagation time td.

Next, the measurement of the backward propagation time tu will be described. First, the transmission control section 221 of the control circuit 22 outputs a transmission start signal to the transmission circuit 21 . This transmission circuit signal includes an instruction to cause the transmission circuit 21 to output a burst signal from the output terminal b. As a result, a burst signal is input from the transmission circuit 21 to the downstream transmission sensor 13 .

The downstream transmission sensor 13 transmits an ultrasonic pulse in response to the burst signal. The ultrasonic pulse propagates through the fluid 14 toward the third receiving sensor 43 .

The ultrasonic pulses then impinge on the inner surface of conduit 11 . The ultrasonic pulse vibrates the wall of the conduit 11 and reaches the ultrasonic transducer of the third receiving sensor 43 . At this time, an electromotive force is generated in the ultrasonic transducer, and the received signal is output to the amplifier circuit 46 .

At the third receiving sensor 43 reflection of the ultrasonic pulse occurs. The ultrasonic pulse reflected by the second receiving sensor 42 propagates through the fluid 14 toward the second receiving sensor 42 .

Further, the ultrasonic pulses impinge on the inner surface of conduit 11 . The ultrasonic pulse vibrates the wall of the conduit 11 and reaches the ultrasonic transducer of the second receiving sensor 42 . At this time, an electromotive force is generated in the ultrasonic transducer, and the received signal is output to the amplifier circuit 45 .

At the second receiving sensor 42 reflection of the ultrasonic pulse occurs. The ultrasonic pulse reflected by the second receiving sensor 42 propagates through the fluid 14 toward the first receiving sensor 41 .

The ultrasonic pulses then impinge on the inner surface of conduit 11 and cause the walls of conduit 11 to vibrate. This vibration reaches the ultrasonic transducer of the first receiving sensor 41, and the ultrasonic transducer vibrates. At this time, an electromotive force is generated in the ultrasonic transducer, and the received signal is output to the amplifier circuit 23 .

Further, reflection of the ultrasonic pulse also occurs at the first receiving sensor 41 . The reflected ultrasonic pulse propagates back into the fluid 14 toward the upstream transmitting sensor 12 . As a result, the propagation path of the ultrasonic pulse from the downstream transmission sensor 13 to the upstream transmission sensor 12 via the third reception sensor 43, the second reception sensor 42, and the first reception sensor 41 is , the direction of the propagation path in the measurement of the forward propagation time td described with reference to FIG. 4 is opposite but the same.

The time difference measuring circuit 25 measures the time difference between the signal received by the third sensor 43 and the signal received by the first sensor 41 . The time difference measuring circuit 25 outputs the measured time difference to the control circuit 22 . The calculation unit 222 (see FIG. 5) of the control circuit 22 treats the time difference when the ultrasonic pulse is transmitted from the downstream transmission sensor 13 as the backward propagation time tu.

The propagation times td and tu are thus obtained. The calculation unit 222 of the control circuit 22 calculates the flow velocity V of the fluid 14 using the above equation 4 based on the propagation times td and tu. get

Here, the propagation path length in Equation 4 corresponds to the length of the propagation path between the first and third receiving sensors 41,43. Therefore, the propagation path length is doubled compared to the ultrasonic flowmeter 10 according to the first embodiment.

In the ultrasonic flowmeter 10 according to the first embodiment, the propagation path corresponds to the Z-shape of the conventional ultrasonic flowmeter arrangement method. On the other hand, in the ultrasonic flowmeter 40 according to the second embodiment, the arrangement method is the same as the conventional V method (reflection method).

The ultrasonic flowmeter 40 according to the second embodiment can change the arrangement method of the ultrasonic sensors by changing the combination of the two reception sensors used by the time difference measurement circuit 25 by the reception sensor selection unit 224. . That is, for the Z method (transmission method), a combination of the first receiving sensor 41 and the second receiving sensor 42 or the combination of the second receiving sensor 42 and the third receiving sensor 43 is used. On the other hand, the V method uses a combination of the first receiving sensor 41 and the third receiving sensor 43 as described above.

According to the ultrasonic flowmeter 40 according to the second embodiment, the Z method and the V method can be arbitrarily switched without changing the mounting positions of the receiving sensors 41, 42, 43, and the flow rate Q of the fluid 14 can be measured.

Therefore, the ultrasonic flowmeter 40 has the advantage of being able to measure the flow rate Q of the fluid 14 with higher accuracy by appropriately selecting either the Z method or the V method according to the difference in the measurement environment. The Z-method can be less affected by attenuation caused by particles or bubbles in the fluid 14 and less affected by drift or swirl in the fluid 14 than the V-method. On the other hand, the V method has an advantage over the Z method in that it can reduce the error due to the influence of the gap between the flows. Flow separation means that the components of the flow of fluid 14 include components other than those parallel to conduit 11 . The fact that there is a difference in flow means that the flow is non-uniform when the pipe line 11 is viewed in axial cross-section.

The ultrasonic flowmeter 40 according to the second embodiment uses the three reception sensors 41, 42, and 43 to support the Z method and the V method among the methods of arranging the ultrasonic sensors. The present invention is not limited to this, and for example, five receiving sensors can be used to support Z-method, V-method and W-method.

(Third Embodiment)
An ultrasonic flowmeter according to the third embodiment will be described below. FIG. 6 is a schematic configuration diagram of an ultrasonic flowmeter according to the third embodiment. In FIG. 6, ultrasonic pulses and various signals are illustrated with an example of measuring a forward propagation time td (described later). In FIG. 6, the same components as in FIGS. 1 to 3 are denoted by the same reference numerals, and descriptions thereof are omitted.

An ultrasonic flowmeter 60 according to the third embodiment electrically connects peak detection circuits 61 and 62, which are examples of the peak value detection section of the present invention, to the output sides of amplifier circuits 23 and 24. This is different from the ultrasonic flowmeter 10 according to the first embodiment.

The peak detection circuits 61 and 62 are configured to detect the peak value as an amount representing the magnitude of the received signal at the receiving sensors 15 and 16 and output it to the calculation section 222 (see FIG. 2) of the control circuit 22. there is

The peak value corresponds to the amplitude of the ultrasound pulse. The amplitude of the ultrasonic pulse increases as the density of the fluid 14 increases, and decreases as the density decreases. Therefore, for the same fluid 14, the higher the pressure, the greater the amplitude.

By utilizing such a relationship between the pressure of the fluid and the amplitude of the ultrasonic pulse, the pressure value of the fluid can be obtained from the peak value.

However, the propagation of ultrasonic waves in the fluid 14 is affected by the temperature of the fluid 14 . The amplitude of the ultrasonic pulses is therefore affected by the temperature of the fluid 14 . Therefore, when the peak value is detected from the received signal of one ultrasonic sensor by the peak detection circuit and the corresponding pressure value is obtained, the temperature of the fluid 14 is actually measured, and the obtained temperature is used for correction. However, there is a disadvantage that the cost of the ultrasonic flowmeter 60 is high.

In the ultrasonic flowmeter 60 according to the third embodiment, the calculation unit 222 calculates the ratio of the two peak values obtained from the reception signals of the reception sensors 15 and 16 (hereinafter referred to as the reception signal ratio). do. This reception signal ratio corresponds to the amplitude ratio of the ultrasonic pulses at the reception sensors 15 and 16 . At each of the receiving sensors 15 , 16 the amplitude of the ultrasonic pulse is similarly affected by the temperature of the fluid 14 . Therefore, by taking the ratio between the two amplitudes, the effect of temperature can be eliminated.

Although the method of obtaining the pressure value of the fluid 14 from the received signal ratio is not particularly limited, for example, the following method is conceivable. For example, through experiments, a calibration curve is created by plotting a plurality of measured values on a graph in which the pressure value of the fluid 14 is plotted on the horizontal axis and the received signal ratio is plotted on the vertical axis. ) in a storage unit (not shown). By actually measuring the received signal ratio with the ultrasonic flowmeter 60 and using the calibration curve, the pressure value of the fluid 14 corresponding to the received signal ratio can be obtained.

As another method, the pressure value of the fluid 14 may be calculated by converting the calibration curve into a function and substituting the actually measured value of the received signal ratio into the function. Further, a table representing the relationship between the pressure value of the fluid 14 and the received signal ratio is stored in the storage unit (not shown) of the calculation unit 222 (see FIG. 2), and the table is referenced from the measured value of the received signal ratio. , the corresponding pressure value of the fluid 14 can also be determined.

As described above, the ultrasonic flowmeter 60 according to the third embodiment uses the peak detection circuits 61 and 62 to measure the pressure of the fluid 14 while suppressing the influence of the temperature of the fluid 14. Flow meter 60 can accurately measure the pressure of fluid 14 .

Further, if the ultrasonic flowmeter 60 according to the third embodiment corrects the value of the flow rate Q using the obtained pressure value of the fluid 14, the influence of the temperature of the fluid 14 can be eliminated, and the flow rate Q can be changed. Measurement accuracy can be improved.

Correction of the flow rate Q based on the pressure value of the fluid 14 can be performed by a known method. For example, it can be performed as follows. A correction coefficient table is stored in a storage unit (not shown) of the calculation unit 222 (see FIG. 2) of the control circuit 22 . The correction coefficient table stores a correction coefficient for each flow velocity for each pressure value. For example, the pressure values are in the columns of the table, the flow velocities are in the rows of the table, and the correction coefficients are entered at the intersections of the rows and columns corresponding to each pressure value and each flow velocity.

In the ultrasonic flowmeter 60, the calculation unit 222 obtains the flow velocity V and the pressure value of the fluid 14, refers to the correction coefficient table, and obtains the correction coefficient corresponding to the flow velocity V and the pressure value. The flow velocity V is corrected with a correction factor.

It should be noted that the present invention is not limited to the above embodiments, and can be implemented with various modifications. In the above embodiment, the size, shape, function, and the like of the constituent elements illustrated in the accompanying drawings are not limited to these, and can be changed as appropriate within the scope of exhibiting the effects of the present invention. In addition, it is possible to carry out by appropriately modifying the present invention as long as it does not deviate from the scope of the purpose of the present invention.

For example, in the above embodiments, the cases where two and three receiving sensors are used have been described as examples, but four or more receiving sensors may be used.

Further, in the second embodiment, the first to third receiving sensors 41, 42, 43 are arranged in the vertical cross section of the pipeline 11, and when the second receiving sensor 42 is at the 0 o'clock position, the first receiving sensor A sensor 42 and a third receiving sensor 43 are arranged at the 6 o'clock position. However, the invention is not limited to such an arrangement. For example, the first receiving sensor 41 may be placed at the 8 o'clock position, the second receiving sensor 42 at the 0 o'clock position, and the third receiving sensor 43 at the 4 o'clock position. Such a positional relationship is only an example and does not limit the present invention.

Moreover, in the above embodiment, the clamp-on type ultrasonic flowmeter was described as an example, but the present invention can also be applied to a spool type in which an ultrasonic sensor is installed in a pipeline. In this case, the surface of the receiving sensor can be exposed in the conduit and the ultrasonic pulses can be directly reflected on the surface of the receiving sensor.

Further, in the third embodiment, the configuration in which the peak detection circuits 61 and 62 (see FIG. 6) are added to the ultrasonic flowmeter 10 (see FIGS. 1 and 3) according to the first embodiment. explained with an example. However, it is not limited to this, and the peak detection circuits 61 and 62 of the third embodiment may be combined with the ultrasonic flowmeter 40 of the second embodiment.

INDUSTRIAL APPLICABILITY The present invention exhibits the effect of being able to provide an ultrasonic flowmeter with a high degree of freedom in circuit design, high sensitivity and few errors, and is suitable for application to ultrasonic flowmeters used in all fields. is.

10, 40, 60 ultrasonic flow meter 11 conduit 12 upstream transmission sensor (transmission sensor)
13 downstream transmission sensor (transmission sensor)
14 fluid 15, 41 first receiving sensor (receiving sensor)
16, 42 second receiving sensor (receiving sensor)
41 third receiving sensor (receiving sensor)
21 transmission circuit 22 control circuit 23, 23, 45, 46 amplifier circuit 25 time difference measurement circuit (time difference measurement unit)
26 display unit 61, 61 peak detection circuit 221 transmission control unit 222 calculation unit 223 output unit 224 reception sensor selection unit

Claims (3)

an upstream transmitting sensor and a downstream transmitting sensor that transmit ultrasonic pulses toward the fluid in the conduit;
at least two receiving sensors mounted sequentially along the direction of flow of the fluid between the upstream transmitting sensor and the downstream transmitting sensor of the conduit;
a time difference measuring unit that measures a time difference between received signals from any two of the at least two receiving sensors;
The time difference when the ultrasonic pulse is transmitted from the upstream transmission sensor is defined as a forward propagation time, and the time difference when the ultrasonic pulse is transmitted from the downstream transmission sensor is defined as a backward propagation time, a calculation unit that calculates the flow rate of the fluid based on the forward propagation time and the backward propagation time;
a peak value detection unit that detects a peak value of the received signal from any two of the at least two receiving sensors ;
Each of the at least two receiving sensors receives the incident ultrasonic pulse, outputs the received signal, and reflects the ultrasonic pulse toward another adjacent receiving sensor. death,
The calculation unit obtains the pressure of the fluid using a ratio of the two peak values detected by the peak value detection unit.
An ultrasonic flowmeter characterized by: 2. The ultrasonic flowmeter according to claim 1, wherein the resonance frequencies of said upstream transmission sensor and said downstream transmission sensor and the anti-resonance frequency of said reception sensor are matched. 3. The ultrasonic flowmeter according to claim 1, wherein the receiving sensor has a wider directivity than the upstream transmitting sensor and the downstream transmitting sensor.

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