JP7246021B2 - ultrasonic flow meter - Google Patents

Description

The present invention relates to an ultrasonic flowmeter that measures the propagation time of ultrasonic waves using a pair of ultrasonic transducers that can transmit and receive, and measures the flow rate of a fluid to be measured.

The ultrasonic propagation time measurement method used in conventional ultrasonic flowmeters is to arrange a pair of ultrasonic transducers capable of transmitting and receiving to face each other, drive one of the ultrasonic transducers with a burst signal, and A sound wave was transmitted and received by the other ultrasonic transducer for measurement. FIG. 3 is an image diagram of a received waveform for explaining the method of measuring the propagation time, in which the horizontal axis indicates time and the vertical axis indicates voltage. The start point T0 in the figure indicates the start point of the driving wave 13, and the end point T1 indicates the end point of the m-th (m=3 in the figure) wave after the start of driving. R0 indicates the start point of reception, and R1 indicates the end point of the m-th wave after the start of reception.

In this way, the zero-crossing point of the m-th wave of the driving wave 13 is defined as the end point T1, and the zero-crossing point of the m-th wave of the received wave 14 received by the other ultrasonic transmitter/receiver is defined as the end point R1. is measured as the propagation time TP1 of the ultrasonic wave, the flow velocity of the fluid is measured using this propagation time, and the flow rate is calculated (see, for example, Patent Document 1).

FIG. 4 shows the configuration of the ultrasonic flowmeter described in Patent Document 2. As shown in FIG. This ultrasonic flowmeter 100 includes an ultrasonic transducer 102 installed in a measurement channel 101 through which a fluid flows, a drive circuit 103 for driving the ultrasonic transducer 102, and a control unit 104 for outputting a start signal to the drive circuit 103. , a propagation time measurement unit 105 for measuring the propagation time of ultrasonic waves, an ultrasonic transducer 107 for receiving ultrasonic waves transmitted from the ultrasonic transducer 102, an amplifier 106 for amplifying the output of the ultrasonic transducer 107, an amplifier 106 is compared with the detection reference voltage 15, and the reception detection circuit 108 stops the propagation time measurement unit 105 when the magnitude relationship is reversed.

In addition, in order to use the propagation time reciprocal difference method so that the effect of temperature on the speed of sound can be ignored, the propagation time of the ultrasonic wave from the upstream side to the downstream side of the measurement channel 101 and the propagation time from the downstream side to the upstream side are A changeover switch 109 is provided for measurement.

Furthermore, even if the delay time inside the ultrasonic transducer or the delay time due to changes in the received waveform changes due to fluctuations in the ultrasonic transducer or temperature changes, etc., it is possible to accurately measure the propagation time of the ultrasonic waves. Propagation time TP from transmitting ultrasonic waves from the ultrasonic transducer to receiving the m-th wave of the first received wave (first received wave) by the reception detection circuit, and the ultrasonic transducer on the receiving side Propagation until the reception detection circuit receives the m-th wave of the second received wave (second received wave) that is reflected once by the ultrasonic transducer on the transmitting side and reaches the ultrasonic transducer on the receiving side A reception delay time measuring means 110 for measuring the time TP2 and obtaining the true propagation time TP0 between ultrasonic transducers and the true reception delay time TR from half the difference between the propagation time TP and the second propagation time TP2. are ready.

FIG. 5 shows an image diagram of the first received wave and the second received wave. As shown in the figure, the ultrasonic transducer on the transmitting side is driven by the driving wave 13 to transmit an ultrasonic signal, and the ultrasonic transducer on the receiving side receives the first received wave 14 . At the same time, a reflected wave is generated, reaches the ultrasonic transducer on the transmission side as a waveform 21, and is reflected. Then, the ultrasonic transducer on the receiving side receives this reflected wave as the second received wave 22 . Here, TR is the delay time of the measured propagation time (see Patent Document 2, for example).

JP-A-9-33308 JP-A-2005-172556

However, according to the ultrasonic flowmeter described in Patent Document 2, it is possible to measure the true reception delay time and perform highly accurate flow measurement, but in order to measure the second received wave, it takes three times as much as usual. Since it is necessary to measure the length of the propagation time, and the propagation time measuring unit is operated for a long time, there is a problem that the current consumption becomes very large.

The present invention solves the above-mentioned conventional problems, and even if the number of times of measuring the second received wave is greatly reduced, the ultrasonic flow rate that can reduce the current consumption of the ultrasonic flow meter without degrading the measurement accuracy. The purpose is to provide

In order to solve the above-described conventional problems, the ultrasonic flowmeter of the present invention includes a pair of ultrasonic transducers capable of transmitting and receiving ultrasonic signals, and an ultrasonic transducer transmitted from one of the ultrasonic transducers and propagating through a fluid. A propagation time measuring unit for measuring the propagation time of the ultrasonic wave until the other ultrasonic transducer receives the sound wave signal, and the m-th wave of the received wave received by the ultrasonic transducer on the receiving side is detected. a reception detection circuit, a first propagation time TP from when an ultrasonic wave is transmitted from an ultrasonic transducer on the transmission side until the m-th wave of the first received wave is detected by the reception detection circuit; The second reception until the reception detection circuit detects the m-th wave of the second reception wave that is reflected once by the ultrasonic transducer and the ultrasonic transducer on the transmission side and reaches the ultrasonic transducer on the reception side. The propagation time TP2 is measured, the true propagation time TP0 between the ultrasonic transducers is obtained from half the difference between the first propagation time TP and the second propagation time TP2, and this true propagation time TP0 and From the difference of the first propagation time TP, the ultrasonic wave reaches the ultrasonic transducer on the receiving side and the reception detection circuit detects that the m-th wave of the received ultrasonic wave has been received from the start of reception. a reception delay time measuring means for calculating a delay time TR; a propagation time correction value storage means for measuring the reception delay time TR by the reception delay time measuring means at a predetermined timing and storing and updating the reception delay time; a propagation time correcting means for obtaining a corrected propagation time TPC by subtracting the reception delay time TR from the first propagation time TP measured by the propagation time measuring unit using TR; and the corrected propagation time TC or the true propagation time. and a control unit for determining the flow rate of the fluid that fills the space between the ultrasonic transducers by calculation from TP0.

As a result, even if the number of times of measuring the second received wave is greatly reduced, the current consumption of the ultrasonic flowmeter can be reduced without degrading the measurement accuracy.

Since the ultrasonic flowmeter of the present invention can reduce current consumption without degrading measurement accuracy, it is possible to reduce the number of batteries installed in the ultrasonic flowmeter, and it is possible to reduce the size and cost of the ultrasonic flowmeter. become.

FIG. 1 is a configuration diagram of an ultrasonic flowmeter according to Embodiment 1 of the present invention; Configuration diagram of an ultrasonic flowmeter according to Embodiment 2 of the present invention Image diagram of the received waveform for explaining the method of measuring the propagation time of ultrasonic waves Configuration diagram of a conventional ultrasonic flowmeter Image diagram of received waveform including first received wave and second received wave

A first invention is a pair of ultrasonic transducers capable of transmitting and receiving ultrasonic signals, and one of the ultrasonic transducers transmits the ultrasonic signal and propagates through a fluid, and the other ultrasonic transducer receives the ultrasonic signal. a propagation time measuring unit for measuring the propagation time of the ultrasonic wave to, a reception detection circuit for detecting the m-th wave of the received wave received by the ultrasonic transducer on the receiving side, and from the ultrasonic transducer on the transmitting side A first propagation time TP from when an ultrasonic wave is transmitted until the m-th wave of the first received wave is detected by the reception detection circuit, and the ultrasonic transducer on the receiving side and the ultrasonic transducer on the transmitting side are 1. A second propagation time TP2 until the reception detecting circuit detects the m-th wave of the second reception wave that has been reflected one by one and reaches the ultrasonic transducer on the receiving side is measured, and the first propagation time TP2 is measured. and the second propagation time TP2, the true propagation time TP0 between the ultrasonic transducers is obtained. From the difference between the true propagation time TP0 and the first propagation time TP, the a reception delay time measuring means for calculating a reception delay time TR from when the ultrasonic wave reaches the ultrasonic transducer and when the reception detecting circuit detects that the m-th wave of the received ultrasonic wave has been received; a propagation time correction value storing means for storing and updating the reception delay time TR measured by the reception delay time measuring means at a predetermined timing; a propagation time correcting means for obtaining a corrected propagation time TPC by subtracting the reception delay time TR from the first propagation time TP; and a fluid filling between the ultrasonic transducers by calculation from the corrected propagation time TC or the true propagation time TPO By providing a control unit that obtains the flow rate of , it is possible to greatly reduce the number of times the second received wave is measured, and the current consumption of the ultrasonic flowmeter can be reduced without degrading the measurement accuracy. .

In a second invention, in addition to the configuration of the first invention, the propagation time correction value storage means measures and stores the reception delay time TR using the reception delay time measurement means at regular intervals. It updates the received reception delay time TR.

A third invention, in addition to the configuration of the first invention, further includes a temperature sensor for measuring the temperature of the fluid to be measured, the temperature of the fluid measured by the temperature sensor, the first propagation time TP, and the ultrasonic waves. reception delay time measurement timing determining means for determining timing for updating the reception delay time TR when any of the amplification factors for amplifying the received signal to a predetermined amplitude changes by a predetermined value or more; and the propagation time correction value The storage means measures the reception delay time TR using the reception delay time measurement means when the reception delay time measurement timing determination means determines that it is time to update the reception delay time TR, and stores the stored reception delay time TR. By updating the delay time TR, the reception delay time can be properly remeasured at the timing when the reception delay time correction value changes, so the current consumption of the ultrasonic flowmeter can be reduced without degrading the measurement accuracy. can.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the present invention is not limited by this embodiment.

(Embodiment 1)
Embodiment 1 of the present invention will be described below with reference to FIGS. 1, 3, and 5. FIG.

FIG. 1 shows a configuration diagram of an ultrasonic flowmeter according to Embodiment 1 of the present invention. As shown in FIG. 1, an ultrasonic flowmeter 20 of the present embodiment includes a pair of ultrasonic transducers 2 and 7 installed upstream and downstream of a measurement channel 1 in which a fluid flows, and a pair of ultrasonic transducers 2 and 7, a switch 9 for switching transmission/reception settings, a drive circuit 3 for driving the ultrasonic transducer set on the transmission side, a control unit 4 for outputting a start signal to the drive circuit 3, and an ultrasonic wave. A propagation time measuring unit 5 for measuring the propagation time, an amplifier 6 for amplifying the ultrasonic signal received by the ultrasonic transducer set on the receiving side to a predetermined amplitude, and the m-th of the received wave amplified by the amplifier 6. A reception detection circuit 8 for detecting waves is provided. In this embodiment, m=3, and the m-th wave will be described as the third wave hereinafter.

Here, the reception detection circuit 8 compares the preset detection reference voltage 15 with the received wave amplified by the amplifier 6, detects the third wave (timing P) when the magnitude relationship is inverted, and then detects the third wave. The end point R1, which is the first zero-crossing point of , is used as the reception timing, and the propagation time measurement unit 5 measures the time from the start of transmission to the reception timing as the propagation time.

Also, the propagation time measuring unit 5 measures the time from when an ultrasonic wave is transmitted from the ultrasonic transducer on the transmitting side to when the reception detecting circuit 8 detects the third wave of the first received wave (first received wave). 1 propagation time TP and the second received wave (second received wave) reflected once by the ultrasonic transducer on the receiving side and the ultrasonic transducer on the transmitting side and reaching the ultrasonic transducer on the receiving side The second propagation time TP2 until the third wave is detected by the reception detection circuit 8 is measured, and the true difference between the ultrasonic transducers is calculated from half the difference between the first propagation time TP and the second propagation time TP2. The propagation time TP0 is obtained, and from the difference between the true propagation time TP0 and the first propagation time TP, the ultrasonic wave reaches the ultrasonic transducer on the receiving side, and the reception detection circuit detects the third ultrasonic wave from the start of reception. A reception delay time measuring means 10 for calculating a reception delay time TR until a wave is detected, and the reception delay time TR is measured by the reception delay time measuring means 10 only at a predetermined timing, stored, and updated. A propagation time correction value storage means 12 and a propagation time correction means 11 for obtaining a corrected propagation time TPC by subtracting the reception delay time TR from the first propagation time TP measured using the reception delay time TR.

Then, the control unit 4 calculates the flow rate of the fluid that fills the space between the ultrasonic transducers 2 and 7 from the corrected propagation time TC or the true propagation time TP0.

In Embodiment 1, the propagation time correction value storage means 12 operates the reception delay time measurement means 10 at preset time intervals, and uses the measured reception delay time TR to calculate the stored reception It is characterized by updating the delay time TR.

During normal flow measurement (when the reception delay time TR is not calculated by the reception delay time measurement means 10), the reception delay time TR stored in the propagation time correction value storage means 12 is used to obtain the first The corrected propagation time TPC used for calculating the flow rate by correcting the propagation time TP is obtained by TPC=TP-TR. Here, the propagation time correction value storage means 12 can be implemented using an EEPROM or a RAM within a microcomputer.

When the reception delay time TR is calculated by the reception delay time measuring means 10, the true propagation time TP0 can be obtained from the second propagation time TP2 and the first propagation time TP. A propagation time TP0 can also be used.

Also, the interval at which the reception delay time measuring means 10 is operated is set to a predetermined timing of about 1 minute to 10 minutes so that the change in the reception delay time TR does not affect the flow rate calculation due to the temperature change in the normal use environment. is desirable. Normally, the measurement interval of the ultrasonic flow meter is several seconds, but by setting the operation timing of the reception delay time measuring means 10 to a constant interval of several minutes, the current consumption can be greatly reduced. Further, even if the measurement timing of the reception delay time TR decreases, the update is performed at a frequency at which the reception delay time TR does not change in the surrounding environment, so that the measurement accuracy is not deteriorated.

As described above, the calculation of the reception delay time TR by the reception delay time measuring means 10 is performed at a predetermined timing or at constant intervals, thereby greatly reducing the number of times the second reception wave is measured. , the current consumption of the ultrasonic flowmeter can be reduced without degrading the measurement accuracy.

(Embodiment 2)
FIG. 2 shows a configuration diagram of an ultrasonic flowmeter according to Embodiment 2 of the present invention. The basic configuration and operation of the ultrasonic flowmeter 30 in this embodiment are the same as in the first embodiment.
The difference from the first embodiment is that a temperature sensor 16 is provided in the measurement channel 1 to enable measurement of the temperature of the gas to be measured, and that the controller 4 is provided with reception delay time measurement timing determination means 17. is.

In the reception delay time measurement timing determination means 17, the current temperature measured by the temperature sensor 16, the current first propagation time TP, and the current reception signal set in the reception detection circuit 8 are amplified to a predetermined amplitude. It is determined whether or not the amplification factor of the amplifier 6 differs from each value at the timing at which the previous reception delay time TR is measured and a predetermined value or more. It is determined that it is time to update the reception delay time TR when it has changed by a predetermined value or more.

Then, the propagation time correction value storage means operates the reception delay time measurement means 10 only when the reception delay time measurement timing determination means 17 determines that it is time to update the reception delay time TR, and measures the reception delay time TR. , the reception delay time TR stored in the propagation time correction value storage means 12 is updated.

As described above, the reception delay time measuring means is operated only when there is a change in the temperature of the surrounding environment or a change in the gas type of the gas to be measured. , and the current consumption can be further reduced.

In this embodiment, a pair of ultrasonic transducers 2 and 7 are arranged facing each other upstream and downstream so that the propagation path of ultrasonic waves matches the flow direction of the measurement flow path 1. , the pair of ultrasonic transducers 2 and 7 and the propagation paths of the ultrasonic waves are not limited to the above. (2) A pair of ultrasonic transducers 2 and 7 are arranged on the same surface upstream and downstream of the measurement channel 1, and the ultrasonic wave propagation path (3) A pair of ultrasonic transducers 2 and 7 are arranged on the same surface upstream and downstream of the measurement flow channel 1, and the ultrasonic wave Various forms can be adopted, such as one in which the propagation path reflects twice on the opposite surfaces of the measurement channel 1 .

As described above, the ultrasonic flowmeter according to the present invention can greatly reduce the timing of measuring the second received wave, and reduce the current consumption of the ultrasonic flowmeter without degrading the measurement accuracy. Therefore, it is possible to reduce the number of batteries to be mounted, realize a small and highly accurate ultrasonic flowmeter, and apply it to applications such as gas meters.

1 measurement channel 2, 7 ultrasonic transducer 3 drive circuit 4 control unit 5 propagation time measurement unit 6 amplifier 8 reception detection circuit 9 switch 10 reception delay time measurement means 11 propagation time correction means 12 propagation time correction value storage means 16 Temperature sensor 17 Reception delay time measurement timing determining means 20, 30 Ultrasonic flow meter

Claims (3)

a pair of ultrasonic transducers capable of transmitting and receiving ultrasonic signals;
a propagation time measuring unit that measures the propagation time of an ultrasonic wave until the other ultrasonic transducer receives an ultrasonic signal transmitted from one of the ultrasonic transducers and propagating through a fluid;
a reception detection circuit for detecting the m-th wave of the reception wave received by the ultrasonic transducer on the reception side;
A first propagation time TP from when an ultrasonic wave is transmitted from the ultrasonic transducer on the transmitting side until the m-th wave of the first received wave is detected by the reception detection circuit, and the ultrasonic transducer on the receiving side and transmission Measure the second propagation time TP2 until the reception detecting circuit detects the m-th wave of the second received wave that is reflected once by the ultrasonic transducer on the receiving side and reaches the ultrasonic transducer on the receiving side. Then, the true propagation time TP0 between the ultrasonic transducers is obtained from half the difference between the first propagation time TP and the second propagation time TP2, and this true propagation time TP0 and the first propagation time From the difference in TP, the reception delay time TR from when the ultrasonic wave reaches the ultrasonic transducer on the receiving side and when the reception detection circuit detects that the m-th wave of the received ultrasonic wave has been received is calculated. a reception delay time measuring means for
Propagation time correction value storage means for measuring the reception delay time TR by the reception delay time measuring means at a predetermined timing and storing and updating the correction value ;
a propagation time correction means for obtaining a corrected propagation time TPC by subtracting the reception delay time TR stored in the propagation time correction value storage means from the first propagation time TP measured by the propagation time measuring unit ;
a control unit that obtains a flow rate of the fluid that fills between the ultrasonic transducers by calculation from the corrected propagation time TPC or the true propagation time TP0;
Ultrasonic flow meter with 2. The propagation time correction value storage means according to claim 1, wherein said reception delay time TR is measured using said reception delay time measuring means at regular intervals, and said stored reception delay time TR is updated. of ultrasonic flowmeters. a temperature sensor for measuring the temperature of the fluid to be measured;
The reception delay time TR is updated when any one of the temperature of the fluid measured by the temperature sensor, the first propagation time TP, and the amplification factor for amplifying the received ultrasonic signal to a predetermined amplitude changes by a predetermined value or more. Reception delay time measurement timing determination means for determining timing,
The propagation time correction value storage means measures and stores the reception delay time TR using the reception delay time measurement means when the reception delay time measurement timing determination means determines that it is time to update the reception delay time TR. 2. The ultrasonic flowmeter according to claim 1, wherein the received reception delay time TR is updated.

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