JP2020180813A - Ultrasonic flowmeter - Google Patents

Abstract

To provide an ultrasonic flowmeter capable of precisely performing no flow rate judgment even when there is a difference in the delay time other than the propagation time of the ultrasonic waves transmitted through the gas to be measured due to the difference in temperature characteristics of the ultrasonic vibrator and transmission/reception circuit and the influence of aging deterioration.SOLUTION: The ultrasonic flowmeter measures the true propagation time in the forward and reverse directions with respect to the fluid flow by detecting the received waves twice after being reflected. With this, it is possible to determine whether the flow rate is actually flowing or whether the flow rate is erroneously detected due to the influence of the characteristic difference of the ultrasonic vibrator and transmission/reception circuit.SELECTED DRAWING: Figure 1

Description

The present invention relates to an ultrasonic flow meter that measures the flow rate of a fluid to be measured by measuring the propagation time of ultrasonic waves using a pair of ultrasonic transducers capable of transmitting and receiving.

In the method of measuring the ultrasonic propagation time used in the conventional ultrasonic flowmeter, a pair of transmit and receive ultrasonic vibrators are arranged facing each other, and one ultrasonic vibrator is driven by a burst signal. Sound waves were transmitted and received by the other ultrasonic transducer for measurement. FIG. 5 is an image diagram of a received waveform for explaining a method of measuring the propagation time, with time on the horizontal axis and voltage on the vertical axis. In the figure, the starting point T0 indicates the start time of the drive wave 13, and the end point T1 indicates the end time of the m (m = 3 in the figure) wave after the start of driving. The start point R0 of the received wave 14 indicates the reception start time point, and the end point R1 indicates the mth wave end time point after the reception start.

In this way, between the starting point T0 and the ending point R1 with the zero crossing point of the first wave of the driving wave 13 as the starting point T0 and the mth wave of the received wave 14 received by the other ultrasonic transmitter / receiver as the ending point R1. The propagation time TP of is measured, the reception delay time TR estimated from the number of drive waves is set in advance, the reception delay time TR is subtracted from the propagation time TP to obtain the propagation time TP0 for flow rate measurement, and this propagation time TP0 is obtained. Was used to measure the flow velocity of the fluid and calculate the flow velocity.

FIG. 6 shows the configuration of the ultrasonic flowmeter described in Patent Document 1. This ultrasonic flowmeter includes an ultrasonic vibrator 102 installed in a measurement flow path 101 through which fluid flows, a drive circuit 103 for driving the ultrasonic vibrator 102, a control unit 104 for outputting a start signal to the drive circuit 103, and a control unit 104. A propagation time measuring unit 105 that measures the propagation time of ultrasonic waves, an ultrasonic vibrator 107 that receives ultrasonic waves transmitted from the ultrasonic vibrator 102, an amplifier 106 that amplifies the output of the ultrasonic vibrator 107, and an amplifier 106. It is composed of a reception detection circuit 108 that stops the propagation time measuring unit 105 when the magnitude relationship is reversed by comparing the output of the above and the detection reference voltage 15. Further, in order to use the propagation time reciprocal difference method so that the influence of temperature on the speed of sound can be ignored, the propagation time of ultrasonic waves from the upstream side to the downstream side and the propagation time from the downstream side to the upstream side of the measurement flow path 101 are used. A changeover switch 109 is provided so that measurement can be performed.

Japanese Unexamined Patent Publication No. 2005-172556

However, due to the temperature characteristics of the ultrasonic vibrator and transmission / reception circuit and the influence of aging deterioration, there is a difference in the delay time other than the propagation time of the ultrasonic waves transmitted through the gas to be measured, and the flow rate is very small even when there is no actual flow rate. There was a problem of detecting that there was.

In order to solve the above-mentioned conventional problems, the ultrasonic flowmeter of the present invention has a pair of ultrasonic vibrators capable of transmitting and receiving ultrasonic signals, and a supersonic vibrator transmitted from one of the ultrasonic vibrators and propagated in a fluid. A propagation time measuring unit that measures the propagation time of ultrasonic waves until the other ultrasonic vibrator receives a sound wave signal, and a reception that detects the mth wave of the received wave received by the ultrasonic vibrator on the receiving side. The reception delay time TR from the start of reception to the detection that the mth wave of the received ultrasonic wave is received by the detection circuit and the reception detection circuit when the ultrasonic wave reaches the ultrasonic vibrator on the receiving side. A propagation time correction means for correcting the propagation time measured by the propagation time measuring unit, and a control unit for obtaining a flow rate of a fluid satisfying between the ultrasonic vibrators by calculation from the propagation time corrected by the propagation time correcting means. The propagation time TP until the m-th wave of the first received wave is received by the reception detection circuit after transmitting ultrasonic waves from the ultrasonic vibrator on the transmitting side, and the ultrasonic vibrator on the receiving side. Propagation time TP2 until the m-th wave of the second received wave that is reflected once by the transmitting side ultrasonic vibrator and reaches the receiving side ultrasonic vibrator is received by the reception detection circuit. Is calculated, and the true propagation time TP0 between the ultrasonic transducers is calculated from half of the difference between the propagation time TP and the propagation time TP2. True downstream propagation from the upstream side to the downstream side. A flow rate non-determining means for obtaining the true upstream side propagation time TP0u from the time TP0d and the downstream side to the upstream side and determining the presence or absence of a flow rate from the difference between the true downstream side propagation time TP0d and the true upstream side propagation time TP0u. It is characterized by having.

As a result, it is possible to accurately determine that there is no flow rate without being affected by the temperature characteristics and aging deterioration of the ultrasonic vibrator and the transmission / reception circuit when there is no flow rate.

Since the ultrasonic flow meter of the present invention can determine that there is no flow rate without being affected by the characteristics of the ultrasonic vibrator and the transmission / reception circuit, it can detect minute flow rate leakage even in a large flow meter where it is difficult to determine a minute flow rate. Becomes possible.

Configuration diagram of the ultrasonic flowmeter according to the first embodiment of the present invention Image of ultrasonic wave reception waveform according to the first embodiment of the present invention Configuration diagram of the ultrasonic flowmeter according to the second embodiment of the present invention (A) Image diagram of ultrasonic signal from upstream side to downstream side in Embodiment 2 of the present invention, (b) Image diagram of ultrasonic signal from downstream side to upstream side. Image of received waveform to explain how to measure the propagation time of ultrasonic waves Configuration diagram of the conventional ultrasonic flowmeter

The first invention is a pair of ultrasonic transducers capable of transmitting and receiving ultrasonic signals, and until the other ultrasonic transducer receives an ultrasonic signal transmitted from one of the ultrasonic transducers and propagated through a fluid. The propagation time measuring unit that measures the propagation time of the ultrasonic waves, the reception detection circuit that detects the mth wave of the received wave received by the ultrasonic vibrator on the receiving side, and the ultrasonic vibrator on the receiving side. The propagation time measured by the propagation time measuring unit using the reception delay time TR from the start of reception to the detection that the mth wave of the received wave of the ultrasonic wave is received by the reception detection circuit when the ultrasonic wave arrives. A propagation time correction means for correction, a control unit for obtaining a flow rate of a fluid satisfying between the ultrasonic transducers by calculation from the propagation time corrected by the propagation time correction means, and an ultrasonic wave from the ultrasonic transducer on the transmitting side. Propagation time TP until the mth wave of the first received wave is received by the reception detection circuit, and once for the ultrasonic vibrator on the receiving side and once for the ultrasonic vibrator on the transmitting side. The propagation time TP2 until the mth wave of the second received wave that is reflected and reaches the ultrasonic transducer on the receiving side is received by the reception detection circuit is measured, and the propagation time TP and the propagation time TP2 are measured. A method of calculating the true propagation time TP0 between the ultrasonic transducers from one half of the difference, the true downstream propagation time TP0d from the upstream side to the downstream side and the true upstream side from the downstream side to the upstream side. By providing a flow rate non-determining means for obtaining the side propagation time TP0u and determining the presence or absence of the flow rate from the difference between the true downstream side propagation time TP0d and the true upstream side propagation time TP0u, the ultrasonic vibrator and Since the difference in true propagation time between the forward direction and the reverse direction can be confirmed without being affected by the temperature characteristics of the transmission / reception circuit and aging deterioration, the accuracy of determining the presence or absence of the flow rate can be improved.

In the second invention, in addition to the configuration of the first invention, the true downstream propagation time TP0d and the true upstream propagation time TP0u obtained by the flow rate non-determining means are used to move from the upstream side to the downstream side. It is provided with a reception delay time saving means for obtaining and saving the downstream reception delay time TRd when the propagation time to the side is measured and the upstream reception delay time TRu when the propagation time from the downstream side to the upstream side is measured.
The propagation time correction means uses the downstream reception delay time TRd and the upstream reception delay time TRu stored in the reception delay time storage means to propagate the first received wave measured by the propagation time measuring unit. By correcting the above, the flow rate measurement accuracy can be improved without being affected by the temperature characteristics of the ultrasonic vibrator and the transmission / reception circuit and the deterioration over time.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to this embodiment.

(Embodiment 1)
FIG. 1 shows a configuration diagram of an ultrasonic flow meter according to the first embodiment of the present invention.

As shown in FIG. 1, the ultrasonic flowmeter 20 of the present embodiment includes a pair of ultrasonic transducers 2 and 7 that can transmit and receive ultrasonic signals installed upstream and downstream of the measurement flow path 1 through which fluid flows. , A changeover switch 9 for switching the transmission / reception settings of the pair of ultrasonic vibrators 2 and 7, a drive circuit 3 for driving the ultrasonic vibrator set on the transmission side, and a control for outputting a start signal to the drive circuit 3. Part 4, an amplifier 6 that amplifies the ultrasonic signal received by the ultrasonic vibrator set on the receiving side to a predetermined amplitude, and a reception detection circuit that detects the mth wave of the received wave amplified by the amplifier 6. 8 and propagation for measuring the ultrasonic propagation time TP until the ultrasonic signal transmitted from the ultrasonic transducer set on the transmitting side and propagating the fluid is received by the ultrasonic transducer set on the receiving side. The time measuring unit 5, the control unit 4 that obtains the flow rate of the fluid satisfying between the ultrasonic vibrators 2 and 7 by calculation from the propagation time TP, and the reception detection circuit 8 when the ultrasonic waves reach the ultrasonic vibrator on the receiving side. Propagation time correction means 10 for correcting the propagation time measured by the propagation time measuring unit 5 using the reception delay time TR from the start of reception to the detection that the mth wave of the ultrasonic reception wave has been received, with or without flow rate The determination means 12 is provided.

Here, as shown in FIG. 5, the reception detection circuit 8 compares the preset detection reference voltage 15 with the reception wave 14 amplified by the amplifier 6, and determines the mth wave because the magnitude relationship is reversed. The detection (timing P) is performed, the end point R1 which is the first zero crossing point after that is set as the reception timing, and the propagation time measuring unit 5 measures the time from the transmission start (start point T0) to the end point R1 as the propagation time TP. is there.

FIG. 2 is an image diagram showing the relationship between the received wave and the propagation time of this embodiment. As shown in the figure, the ultrasonic transducer on the transmitting side is driven by the drive wave 13 to transmit an ultrasonic signal, and the ultrasonic transducer on the receiving side receives it as the first received wave 14. At the same time, a reflected wave is generated, reaches the ultrasonic transducer on the transmitting side as a waveform 21, and is reflected. Further, the ultrasonic transducer on the receiving side receives this reflected wave as the second received wave 22. The reception detection circuit 8 is provided with a second reception wave detection means 11 for detecting the second reception wave 22.

The propagation time measuring unit 5 transmits ultrasonic waves from the ultrasonic vibrator 2 on the transmitting side and receives the mth wave of the first received wave 14 by the reception detection circuit 8 and the propagation time TP and the receiving side. The m-th wave of the second received wave 22 that is reflected once by the ultrasonic vibrator 7 on the transmitting side and the ultrasonic vibrator 2 on the transmitting side and reaches the ultrasonic vibrator 7 on the receiving side is detected as the second received wave. The propagation time TP2 to the end point R2, which is the timing for determining that the means 11 has received the signal, is measured.

As can be seen from FIG. 2, the true propagation time TP0 between the ultrasonic transducers can be obtained by the following equation (1).

TP0 = (TP2-TP) / 2 ... (1)
In the present embodiment, the second received wave detecting means 11 is used to measure the second propagation time TP2, so that the propagation time measuring unit 5 can measure the second propagation time TP2 from the upstream side to the downstream side at a predetermined timing. The second propagation time TP2d on the downstream side to In (3), the true downstream propagation time TP0d from the downstream side to the upstream side and the true upstream propagation time TP0u from the downstream side to the upstream side were calculated, and the difference between the two propagation times was less than a predetermined value. In some cases, it is determined that there is no flow rate.

TP0d = (TP2d-TPd) / 2 ... (2)
TP0u = (TP2u-TPu) / 2 ... (3)
Here, TPd and TPu are propagated from the upstream side to the downstream side (downstream side propagation) measured at the time of normal flow rate measurement (when the flow rate is measured only by measuring the propagation time of the first received wave). Time) and the propagation time from the downstream side to the upstream side (upstream side propagation time).

As described above, according to the present embodiment, the second received wave detecting means 11 can be used to detect the second received wave, so that the temperature characteristics and aging deterioration of the ultrasonic oscillator and the transmission / reception circuit are deteriorated. Since the difference in the true propagation time between the forward direction and the reverse direction of the flow can be confirmed without being affected by the above, the accuracy of determining the presence or absence of the flow rate can be improved.

Further, in the embodiment of the present invention, it is assumed that minute leakage is confirmed in the environment where the ultrasonic flow meter is installed, and the flow rate presence / absence determining means 12 is operated every several hours. This makes it possible to determine whether or not there is a leak in the piping system in which the ultrasonic flowmeter is installed, without being affected by the temperature characteristics of the ultrasonic transducer and the transmission / reception circuit and deterioration over time.

The second received wave detecting means 11 does not perform the reception detection operation when the first received wave 14 arrives at the ultrasonic transducer on the receiving side, and receives when the second received wave 22 arrives. The second propagation time TP2 is measured by performing the detection operation. Since the reception delay time TR in FIG. 2 is determined by the characteristics of the ultrasonic transducer, the same value is obtained for both the first received wave and the second received wave.

(Embodiment 2)
FIG. 3 shows a block diagram of the ultrasonic flowmeter according to the second embodiment. The basic configuration and operation are the same as those in the first embodiment. The difference between the ultrasonic flow meter 30 of the present embodiment and the ultrasonic flow meter 20 of the first embodiment is that the control unit 4 is provided with the reception delay time saving means 16 and the reception delay time updating means 17.

The reception delay time saving means 16 includes the downstream propagation time TPd and the upstream propagation time TPu measured by the propagation time measuring unit 5, the true downstream propagation time TP0d obtained by the flow rate presence / absence determining means 12, and the true upstream side. Propagation time The downstream reception delay time TRd when the propagation time from the upstream side to the downstream side of TP0u is measured and the upstream reception delay time TRu when the propagation time from the downstream side to the upstream side are measured are obtained and saved. ..

FIG. 4A is an image diagram showing the propagation of ultrasonic waves from the upstream side to the downstream side, and FIG. 4B is an image diagram showing the propagation of ultrasonic waves from the downstream side to the upstream side. The downstream side measured by the propagation time measuring unit 5 Side propagation time TPd and upstream propagation time TPu, true downstream propagation time TP0d obtained by the flow rate presence / absence determining means 12 and true upstream propagation time TP0u, downstream reception saved by the reception delay time saving means 16. The delay time TRd and the flow side reception delay time TRu are shown.

As can be seen from FIG. 4, the downstream reception delay time TRd and the upstream reception delay time TRu can be obtained by the following equations (4) and (5).

TRd = TPd-TP0d ... (4)
TRu = TCu-TP0u ... (5)
Further, the reception delay times TRd and TRu stored in the reception delay time storage means 16 are updated each time the reception delay time TRd and TRu are newly measured by the propagation time measurement unit 5 by the reception delay time update means 17.

Then, the propagation time correction means 10 receives the second received wave by the second received wave detecting means 11 at the time of normal flow rate measurement (the propagation time is measured only by the first received wave to obtain the flow rate. Time) is the downstream propagation time TPd from the upstream side to the downstream side measured by the propagation time measuring unit 5 and the downstream propagation time TPu from the downstream side to the upstream side stored in the reception delay time storage means 16. It is corrected by subtracting the side reception delay time TRd and the upstream side reception delay time TRu, respectively, and the control unit 4 calculates the flow rate using the propagation time corrected by the propagation time correction means 10.

With the above configuration, the flow rate measurement accuracy can be improved without being affected by the temperature characteristics of the ultrasonic vibrator and the transmission / reception circuit and the deterioration over time. Further, according to the present embodiment, the zero point correction is performed regardless of the surrounding environment and the presence or absence of the flow rate, so that the zero point adjustment step performed at the time of manufacturing the ultrasonic flow meter can be omitted. It also makes it possible to reduce manufacturing costs.

In the present embodiment, a pair of ultrasonic vibrators 2 and 7 are arranged to face each other upstream and downstream so that the propagation path of ultrasonic waves coincides with the flow direction of the measurement flow path 1. , The pair of ultrasonic transducers 2 and 7 and the ultrasonic propagation path are not limited to this, and (1) upstream and downstream so that the ultrasonic propagation path crosses diagonally with respect to the flow direction of the measurement flow path 1. A pair of ultrasonic transducers 2 and 7 arranged opposite to each other, (2) A pair of ultrasonic transducers 2 and 7 are arranged on the same surface upstream and downstream of the measurement flow path 1, and the ultrasonic propagation path. (3) A pair of ultrasonic transducers 2 and 7 are arranged on the same surface upstream and downstream of the measurement flow path 1 so that the ultrasonic waves are reflected once on the opposite surfaces of the measurement flow path 1. Various forms can be adopted, such as one in which the propagation path is reflected twice on the opposite surfaces of the measurement flow path 1.

As described above, the ultrasonic flow meter according to the present invention can always accurately determine the flow rate without being affected by the temperature characteristics of the ultrasonic vibrator and the transmission / reception circuit and the deterioration over time. It can also be applied to applications such as gas meters that require detection.

1 Measurement flow path 2, 7 Ultrasonic oscillator 3 Drive circuit 4 Control unit 5 Propagation time measurement unit 6 Amplifier 8 Reception detection circuit 9 Changeover switch 10 Propagation time correction means 11 Second reception wave detection means 12 Flow rate presence / absence judgment means 16 Reception Delay time storage means 17 Reception delay time update means

Claims (2)

A pair of ultrasonic transducers capable of transmitting and receiving ultrasonic signals,
A propagation time measuring unit that measures the propagation time of ultrasonic waves until the other ultrasonic transducer receives an ultrasonic signal transmitted from one of the ultrasonic transducers and propagated in a fluid.
A reception detection circuit that detects the mth wave of the received wave received by the ultrasonic transducer on the receiving side,
The propagation using the reception delay time TR from the start of reception to the detection that the mth wave of the ultrasonic reception wave is received by the reception detection circuit when the ultrasonic wave reaches the ultrasonic vibrator on the receiving side. Propagation time correction means for correcting the propagation time measured by the time measurement unit,
A control unit that obtains the flow rate of the fluid that satisfies the space between the ultrasonic transducers by calculation from the propagation time corrected by the propagation time correction means.
Propagation time TP until the m-th wave of the first received wave is received by the reception detection circuit after transmitting ultrasonic waves from the ultrasonic transducer on the transmitting side, and transmission with the ultrasonic transducer on the receiving side. The propagation time TP2 until the m-th wave of the second received wave that has been reflected once by the ultrasonic transducer on the receiving side and reached the ultrasonic transducer on the receiving side is received by the reception detection circuit is measured. Then, the true propagation time TP0 between the ultrasonic transducers is calculated from half of the difference between the propagation time TP and the propagation time TP2, and the true downstream propagation time TP0d from the upstream side to the downstream side. A flow rate non-determining means for obtaining the true upstream side propagation time TP0u from the downstream side to the upstream side and determining the presence or absence of the flow rate from the difference between the true downstream side propagation time TP0d and the true upstream side propagation time TP0u. Ultrasonic flowmeter equipped with. The downstream reception delay time TRd when the propagation time from the upstream side to the downstream side is measured using the true downstream side propagation time TP0d and the true upstream side propagation time TP0u obtained by the flow rate non-determining means. It is equipped with a reception delay time storage means for obtaining and storing the upstream reception delay time TRu when the propagation time from the downstream side to the upstream side is measured.
The propagation time correction means uses the downstream reception delay time TRd and the upstream reception delay time TRu stored in the reception delay time storage means to propagate the first received wave measured by the propagation time measuring unit. The ultrasonic flowmeter according to claim 1, wherein the ultrasonic flowmeter is characterized in that.

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