JP2020180814A - Ultrasonic flowmeter - Google Patents

Abstract

To provide an ultrasonic flowmeter capable of achieving high-precision measurement using the received wave twice without limiting the installation environment by reducing the effects of noise and temperature.SOLUTION: N reception delay time TRs measured by the reception delay time measuring means 10 is saved and reception delay time storage means 12 saves N pieces average values as the reception delay time correction value TRC. A control unit 4 calculates the flow rate by correcting the propagation time with the reception delay time correction value TRC saved in the reception delay time storage means 12.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. 4 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 16, and the end point T1 indicates the end time of the m (m = 3 in the figure) wave after the start of the drive. The starting point R0 indicates the reception start time point, and the end point R1 indicates the m-wave end time point after the reception start. In this way, between the end point T1 and the end point R1 with the zero crossing point of the mth wave of the drive wave 16 as the end point T1 and the mth wave of the received wave received by the ultrasonic transmitter / receiver on the receiving side as the end point R1. Was measured as the propagation time TP1 of ultrasonic waves, the flow velocity of the fluid was measured using this propagation time TP1, and the flow rate was calculated (see, for example, Patent Document 1).

FIG. 5 shows the configuration of the ultrasonic flowmeter described in Patent Document 2. The ultrasonic flow meter 100 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, and a control unit 104 for outputting a start signal to the drive circuit 103. , 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. It is composed of a reception detection circuit 108 that compares the output of 106 with the detection reference voltage 18 and stops the propagation time measuring unit 105 when the magnitude relationship is reversed.

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.

Furthermore, even if the delay time in the ultrasonic vibrator or the reception delay time due to a change in the received wave changes due to variations in the ultrasonic vibrator or temperature changes, the ultrasonic propagation time can be accurately measured. Propagation time TP until the mth wave of the first received wave (first received wave) is received by the reception detection circuit 108 after transmitting ultrasonic waves from the ultrasonic vibrator on the side, and ultrasonic vibration on the receiving side. The reception detection circuit 108 receives the mth wave of the second received wave (second received wave) that is reflected once by the child and the ultrasonic vibrator on the transmitting side and reaches the ultrasonic vibrator on the receiving side. The second propagation time TP2 up to is measured, and the true propagation time TP0 and the true reception delay time TR between the ultrasonic transducers are obtained from the half of the difference between the propagation time TP and the second propagation time TP2. The time measuring means 110 is provided.

FIG. 6 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 drive wave 16 to transmit an ultrasonic signal, and the ultrasonic transducer on the receiving side receives the ultrasonic signal as the first received wave 17. At the same time, a reflected wave is generated, reaches the ultrasonic transducer on the transmitting 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, it is the delay time of the propagation time measured by TR (see, for example, Patent Document 2).

Japanese Unexamined Patent Publication No. 9-33308 Japanese Unexamined Patent Publication No. 2005-172556

However, according to the ultrasonic flow meter described in Patent Document 2, the reception delay time can be measured and the flow rate can be measured with high accuracy. However, when the fluid to be measured is a gas, the second received wave is attenuated during propagation. Since it is large and the received signal is very small, it is easily affected by noise and temperature, and it is necessary to limit the usage environment of the ultrasonic flowmeter electrically and temperature in order to realize measurement with the required accuracy. There was a problem.

An object of the present invention is to solve the above-mentioned conventional problems, and to provide an ultrasonic flowmeter capable of realizing highly accurate measurement without limiting the installation environment by reducing the influence of noise and temperature. To do.

In order to solve the above-mentioned conventional problems, the ultrasonic flowmeter of the present invention has a pair of ultrasonic transducers capable of transmitting and receiving ultrasonic signals, and a pair of ultrasonic transducers transmitted from one of the ultrasonic transducers and propagated in a fluid. The propagation time measuring unit that measures the propagation time of the ultrasonic wave until the other ultrasonic vibrator receives the sound wave signal, and the mth wave of the received wave received by the ultrasonic vibrator on the receiving side are detected. The reception detection circuit, the first propagation time TP from transmitting ultrasonic waves from the transmitting side ultrasonic transducer to detecting the mth wave of the first received wave by the reception detection circuit, and the receiving side super The second until the reception detection circuit detects the mth wave of the second received wave that has been reflected once by the sound oscillator and the ultrasonic oscillator on the transmitting side and reached the ultrasonic oscillator on the receiving side. The propagation time TP2 is measured, and the true propagation time TP0 between the ultrasonic transducers is obtained from half of the difference between the first propagation time TP and the second propagation time TP2, and the true propagation time TP0 and the said Reception delay 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 reaches the ultrasonic vibrator on the receiving side due to the difference in the first propagation time TP. A reception delay time measuring means for calculating the time TR, and a reception delay time saving means for storing the reception delay time TR for a predetermined number of times by measuring the reception delay time TR by the reception delay time measuring means at a predetermined timing. The reception delay time correction value updating means for saving and updating the average value of the reception delay times saved at the time when the reception delay time TR for the predetermined number of times is saved as the reception delay time correction value TRC, and the reception delay time. The propagation time correction means for obtaining the correction propagation time TPC by subtracting the reception delay time correction value TRC from the first propagation time TP measured by the propagation time measurement unit using the correction value TRC, and the correction propagation time TPC or the said By providing a control unit that calculates the flow rate of the fluid that fills the space between the ultrasonic transducers by calculation from the true propagation time TP0, it is possible to reduce the influence of noise and temperature on the reception delay time, and it is highly accurate. An ultrasonic flow meter can be realized.

Since the ultrasonic flow meter of the present invention can set the reception delay time used for flow rate calculation without being affected by noise or temperature change, the ultrasonic flow rate can maintain highly accurate flow rate measurement without limiting the usage environment. It becomes possible to realize the total.

Configuration diagram of the ultrasonic flowmeter according to the first embodiment of the present invention Configuration diagram of the ultrasonic flowmeter according to the second embodiment of the present invention Configuration diagram of the ultrasonic flowmeter according to the third embodiment of the present invention Image of ultrasonic wave reception waveform to explain how to measure ultrasonic wave propagation time Configuration diagram of the conventional ultrasonic flowmeter Image of received waveform including first received wave and second received wave

In the first invention, a pair of ultrasonic transducers capable of transmitting and receiving ultrasonic signals and an ultrasonic signal transmitted from one of the ultrasonic transducers and propagated in a fluid are received by the other ultrasonic transducer. From the propagation time measuring unit that measures the propagation time of the ultrasonic waves up to, 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 transmitting side. The first propagation time TP until the mth wave of the first received wave is detected by the reception detection circuit after transmitting the ultrasonic wave, and the ultrasonic vibrator on the receiving side and the ultrasonic vibrator on the transmitting side 1 The second propagation time TP2 until the mth wave of the second received wave that is reflected each time and reaches the ultrasonic transducer on the receiving side is detected by the reception detection circuit is measured, and the first propagation time TP is measured. The true propagation time TP0 between the ultrasonic transducers is obtained from half of the difference between the second propagation time TP2 and the second propagation time TP2, and the difference between the true propagation time TP0 and the first propagation time TP is the difference between the receiving side. The reception delay time measuring means for calculating 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 reaches the sound oscillator, and the above-mentioned reception delay time measuring means. The reception delay time saving means for measuring the reception delay time TR by the reception delay time measuring means at a predetermined timing and saving the reception delay time TR for a predetermined number of times and the reception delay time TR for the predetermined number of times are saved. Measured by the propagation time measuring unit using the reception delay time correction value updating means for saving and updating the average value of the reception delay time saved at that time as the reception delay time correction value TRC and the reception delay time correction value TRC. The propagation time correction means for obtaining the corrected propagation time TPC by subtracting the reception delay time correction value TRC from the first propagation time TP, and the ultrasonic vibrator by calculation from the corrected propagation time TPC or the true propagation time TP0. By providing a control unit that determines the flow rate of the fluid that fills the gap, it is possible to reduce the influence of noise and temperature on the reception delay time used for flow rate calculation, and a highly accurate ultrasonic flow meter can be realized. ..

In the second invention, in addition to the configuration of the first invention, a temperature sensor for measuring the temperature of the fluid to be measured is provided, and the reception delay time storage means includes the temperature of the fluid measured by the temperature sensor and the temperature of the fluid measured by the temperature sensor. The storage of the reception delay time TR is started at the timing when either the first propagation time TP or the amplification factor that amplifies the ultrasonic reception signal to a predetermined amplitude changes to the first predetermined value or more. The reception delay time TR measured by the reception delay time measuring means is added only when the change amount of any of the fluid temperature, the first propagation time TP, and the amplification factor is equal to or less than the second predetermined value. By storing in, the reception delay time can be measured accurately without being affected by changes in temperature and the gas to be measured, and a highly accurate ultrasonic flowmeter can be realized.

In the third invention, in addition to the configuration of the second invention, the temperature of the fluid measured by the temperature sensor, the first propagation time TP, and the ultrasonic wave before and after the measurement operation of the reception delay time measuring means. The reception delay time measurement condition determining means for determining whether or not any one of the amplification factors for amplifying the received signal of the above or all the values is within the predetermined change amount is provided, and the reception delay time is stored. When the means is determined by the reception delay time measurement condition determining means that the change is not within a predetermined change amount, the means does not save the reception delay time TR measured by the reception delay time measuring means, so that the first propagation time TP And the second propagation time TP2 is being measured, and if there is a temperature change or gas change, the reception delay time correction value TRC affected by the change is no longer corrected, so a more accurate ultrasonic flowmeter Can be realized.

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.

The basic configuration of the ultrasonic flowmeter 20 of the present embodiment is the transmission and reception of a pair of ultrasonic vibrators 2 and 7 installed upstream and downstream of the measurement flow path 1 and a pair of ultrasonic vibrators 2 and 7. The changeover switch 9 for switching the setting of, the drive circuit 3 for driving the ultrasonic transducer set on the transmission side, the control unit 4 for outputting the start signal to the drive circuit 3, and the propagation time of the ultrasonic wave are measured. The propagation time measuring unit 5 and the amplifier 6 that amplifies the ultrasonic signal received by the ultrasonic vibrator set on the receiving side to a predetermined amplitude, and the output of the amplifier 6 and the detection reference voltage 18 are compared and the magnitude relationship is large. It is composed of a reception detection circuit 8 that stops the propagation time measuring unit 5 when it is inverted.

Furthermore, even if the delay time in the ultrasonic vibrator or the reception delay time due to a change in the reception waveform changes due to variations in the ultrasonic vibrator or temperature changes, the ultrasonic propagation time can be accurately measured. Propagation time TP from transmitting ultrasonic waves from the ultrasonic vibrator on the side to receiving the mth wave of the first received wave (first received wave) by the reception detection circuit 8 and ultrasonic vibration on the receiving side. Until the mth wave of the second received wave (second received wave) that has been reflected once by the child and the ultrasonic oscillator on the transmitting side and reached the ultrasonic oscillator on the receiving side is received by the reception detection circuit. The reception delay time measuring means 10 is provided for measuring the propagation time TP2 of the above two and obtaining the true propagation time TP0 and the true reception delay time TR between the ultrasonic transducers from one half of the difference between the two propagation times. There is.

Further, the control unit 4 has the reception delay time storage means 12 and the reception delay in order to reduce the influence of the reception delay time TR used for the flow rate calculation on the electrical and temperature due to the installation environment of the ultrasonic flow meter. The time correction value updating means 13 is provided.

The reception delay time storage means 12 stores the reception delay time TR measured by the reception delay time measuring means 10 for a predetermined number of times (N). Then, the reception delay time correction value updating means 13 averages the N reception delay time TRs stored in the reception delay time storage means 12, and uses the reception delay time correction value TRC used for the flow rate calculation based on the averaged result. Update.

The propagation time correction means 11 subtracts the reception delay time correction value TRC updated by the reception delay time correction value update means 13 from the propagation time TP of the first received wave measured by the propagation time measurement unit 5, and corrects the propagation time TPC. Ask for.

Then, the control unit 4 can calculate the flow rate by using the corrected propagation time TPC corrected by the propagation time correction means 11. When measuring the second received wave, the flow rate of the fluid can be calculated using the true propagation time TP0.

As a method of updating the reception delay time correction value TRC stored in the reception delay time storage means 12 by the reception delay time correction value update means 13, every time a new reception delay time TR is measured by the reception delay time measurement means 10. In addition to the new reception delay time TR measured this time, the N-1 reception delay time TR measured up to the previous time is added to the method of finding and updating the moving average by the average of N pieces, or by the reception delay time measuring means 10. A method of finding and rewriting the average every time N reception delay time TRs are measured can be adopted.

According to this embodiment, by averaging the measurement results of the reception delay time TR by the reception delay time measuring means 10, the influence of noise and temperature change can be reduced, and the flow rate can be measured with high accuracy without limiting the installation environment. Can be realized.

(Embodiment 2)
FIG. 2 shows a block diagram of the ultrasonic flowmeter according to the second embodiment of the present invention. The basic configuration and operation of the ultrasonic flow meter 30 of the present embodiment are the same as those of the first embodiment. The difference from the first embodiment is that the temperature sensor 14 is provided in the measurement flow path 1 so that the temperature of the gas to be measured can be measured, and the reception delay time TR is stored in the reception delay time storage means 12. The condition was added.

The reception delay time storage means 12 of the present embodiment has the temperature of the gas to be measured measured by the temperature sensor 14 since the reception delay time correction value TRC was updated by the reception delay time correction value update means 13 last time, and the first first. When either the propagation time TP or the amplification factor of the amplifier changes by more than the first predetermined value set for each value, the reception delay time TR measured by the reception delay time measuring means 10 is stored. Start.

Further, the reception delay time storage means 12 changes the temperature of the gas to be measured, the first propagation time TP, and the amplification factor at the time when the reception delay time storage means 12 starts storage of the reception delay time TR, respectively. Is monitored, and the reception delay time TR is additionally saved only when the change width of any or all of the three values is equal to or less than the second predetermined value set for each value.

Then, the reception delay time correction value updating means 13 averages the N reception delay time TRs at the timing when the reception delay time TRs for a predetermined number of times (N) are stored in the reception delay time storage means 12. The reception delay time correction value TRC is updated. However, if N reception delay time TRs cannot be saved within a predetermined time from the start of saving the reception delay time TR, the number of reception delay time TRs that can be saved in the reception delay time storage means 12 is averaged. The reception delay time correction value TRC is updated, or the reception delay time TR stored in the reception delay time storage means 12 is deleted, and then the reception delay time correction is performed until N reception delay time TRs are saved. Adopt a method of deferring the update of the value TRC.

According to the present embodiment, the erroneous reception delay time correction value TRC is not adopted due to the influence when the temperature changes or the type of the gas to be measured changes, so that the influence of the change in the surrounding environment of the ultrasonic flowmeter Highly accurate measurement performance can be realized without receiving.

(Embodiment 3)
FIG. 3 shows a block diagram of the ultrasonic flowmeter according to the third embodiment of the present invention. The basic configuration and operation of the ultrasonic flow meter 40 of the present embodiment are the same as those of the second embodiment. The difference from the second embodiment is that the control unit 4 is provided with the reception delay time measurement condition determination means 15.

The reception delay time measurement condition determination means 15 determines the temperature of the fluid measured by the temperature sensor 14, the first propagation time TP, and the amplification factor of the amplifier 6 before and after the reception delay time measurement means 10 measures the reception delay time TR. It is confirmed whether any or all of the values are within the predetermined change amount set for each value. Then, the reception delay time storage means 12 does not store the measured reception delay time TR when it is determined by the reception delay time measurement condition determination means 15 that the change amount is not within a predetermined change amount.

According to the present embodiment, the reception delay time TR affected when there is a temperature change or a gas change while measuring the first propagation time TP and the second propagation time TP2 is not adopted. A more accurate ultrasonic flowmeter can be realized.

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 flowmeter according to the present invention can reduce the influence of noise and temperature change on the reception delay time, so that the ultrasonic flowmeter is highly accurate even in an installation environment where noise and temperature change are expected. It is possible to realize the above, and it can be applied to applications such as gas meters.

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 Reception delay time measurement means 11 Propagation time correction means 12 Reception delay time storage means 13 Reception Delay time correction value update means 14 Temperature sensor 15 Reception delay time Measurement condition judgment means 20, 30, 40 Ultrasonic flowmeter

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 ultrasonic waves until the ultrasonic signal transmitted from one of the ultrasonic transducers and propagated through the fluid is received by the other ultrasonic transducer.
A reception detection circuit that detects the mth wave of the received wave received by the ultrasonic transducer on the receiving side,
The first propagation time TP until the mth wave of the first received wave is detected by the reception detection circuit after transmitting ultrasonic waves from the ultrasonic vibrator on the transmitting side, and the ultrasonic vibrator and transmission on the receiving side. Measure the second propagation time TP2 until the m-th wave of the second received wave that is reflected once by the ultrasonic transducer on the side and reaches the ultrasonic transducer on the receiving side is detected by the reception detection circuit. Then, the true propagation time TP0 between the ultrasonic transducers is obtained from half of the difference between the first propagation time TP and the second propagation time TP2, and the true propagation time TP0 and the first propagation time TP are obtained. From the difference between the above, 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 is calculated. Reception delay time measuring means and
A reception delay time saving means that measures the reception delay time TR by the reception delay time measuring means at a predetermined timing and saves the reception delay time TR for a predetermined number of times.
A reception delay time correction value updating means for storing and updating the average value of the reception delay times saved at the time when the reception delay time TR for the predetermined number of times is saved as the reception delay time correction value TRC, and
Propagation time correction means for obtaining the correction propagation time TPC by subtracting the reception delay time correction value TRC from the first propagation time TP measured by the propagation time measuring unit using the reception delay time correction value TRC.
An ultrasonic flow meter including a control unit for obtaining a flow rate of a fluid satisfying between the ultrasonic transducers by calculation from the corrected propagation time TPC or the true propagation time TP0. Equipped with a temperature sensor for measuring the temperature of the fluid under test
The reception delay time storage means has a first predetermined value of 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 signal of ultrasonic waves to a predetermined amplitude. The storage of the reception delay time TR is started at the timing when the value changes above the value, and thereafter, the amount of change in any of the fluid temperature, the first propagation time TP, and the amplification factor is equal to or less than the second predetermined value. The ultrasonic fluid meter according to claim 1, wherein the reception delay time TR measured by the reception delay time measuring means is additionally stored only in the case of. Before or after the measurement operation of the reception delay time measuring means, 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 ultrasonic reception signal to a predetermined amplitude. Alternatively, a reception delay time measurement condition determining means for determining whether or not all the values are within a predetermined change amount is provided.
2. The reception delay time saving means does not save the reception delay time TR measured by the reception delay time measuring means when the reception delay time measuring condition determining means determines that the change amount is not within a predetermined change amount. The ultrasonic flow meter described in.

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