JP4008741B2 - Ultrasonic flow velocity measuring method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic flow velocity measuring method for measuring the flow velocity of a gas or other fluid using ultrasonic waves.
[0002]
[Prior art]
When determining the flow rate of gas or other fluids, first, the flow rate of the fluid is measured continuously or periodically, and the flow rate is calculated based on this. A method using ultrasonic waves is known as one of the fluid flow velocity measurement methods.
[0003]
The principle of this ultrasonic flow velocity measuring method will be described with reference to FIG. In FIG. 4, (1) is an ultrasonic flow velocity measuring tube through which a fluid such as gas flows. In this ultrasonic flow velocity measuring tube (1), ultrasonic transducers (2) and (3) are arranged at a predetermined distance on the upstream side and the downstream side in the flow direction. The ultrasonic transducers (2) and (3) are driven by drive pulses from the drive pulse generation circuit (4) to vibrate, generate and transmit ultrasonic waves, and receive transmitted ultrasonic waves. The received wave when the ultrasonic transducers (3) and (2) vibrate is output from the reception amplification circuit (5).
[0004]
Then, the propagation time until the ultrasonic wave transmitted in the forward direction from the upstream ultrasonic transducer (2) is received by the downstream ultrasonic transducer (3), and the downstream side The difference from the propagation time until the ultrasonic wave transmitted from the ultrasonic transducer (3) in the opposite direction to the flow is received by the upstream ultrasonic transducer (2) is related to the flow velocity. The flow velocity of the fluid is measured by obtaining the propagation time difference using the received wave.
[0005]
In FIG. 4, (6) is a switching circuit for switching the connection between the ultrasonic transducers (2), (3), the drive pulse generation circuit (4), and the reception amplification circuit (5). First, the drive pulse generation circuit After connecting the upstream ultrasonic transducer (2) and the downstream ultrasonic transducer (3) to the reception amplification circuit (5) and measuring the propagation time from the upstream side to the downstream side, The operation of the switching circuit (6) connects the drive pulse generation circuit (4) to the downstream ultrasonic transducer (3), and the upstream ultrasonic transducer (2) to the reception amplification circuit (5). Thus, the propagation time from the downstream side to the upstream side is measured.
[0006]
By the way, in order to reduce an error due to variations in ultrasonic propagation time, an ultrasonic flow velocity measurement method called a single-around method is known. In this sing-around method, as shown in FIG. 5, the ultrasonic waves transmitted from the transmitting ultrasonic transducers (2) and (3) are received by the receiving ultrasonic transducers (3) and (2). At the same time, the transmission of ultrasonic waves from the ultrasonic transducers (2) and (3) on the transmission side is repeated continuously a plurality of times (n times). Then, a propagation time sum from the first ultrasonic transmission to the nth ultrasonic reception is obtained, and the ultrasonic propagation time τ is obtained by dividing the propagation time sum by the number of ultrasonic transmissions. .
[0007]
However, a part of ultrasonic waves transmitted from the ultrasonic transducers (2) and (3) on the transmission side is reflected by the ultrasonic transducers (3) and (2) on the reception side to transmit the ultrasonic transducers on the transmission side. (2) Go to (3), and further reflect by the ultrasonic transducers (2) and (3) on the transmission side and go to the ultrasonic transducers (3) and (2) on the reception side. That is, the ultrasonic wave transmitted from the transmitting-side ultrasonic transducers (2) and (3) for the third time and the above-described reflected ultrasonic wave transmitted from the transmitting-side ultrasonic transducers (2) and (3) for the first time. Sound waves exit from the ultrasonic transducers (2) and (3) almost simultaneously and are received by the ultrasonic transducers (3) and (2) on the receiving side almost simultaneously. For this reason, in detecting the ultrasonic wave transmitted for the third time from the ultrasonic transducers (2) and (3) on the transmission side, the reflected ultrasonic wave transmitted for the first time becomes noise, and the propagation time of the ultrasonic wave There was a problem that an error occurred in the measurement.
[0008]
[Problems to be solved by the invention]
Therefore, in order to eliminate the above difficulty, as shown in FIG. 2, after receiving ultrasonic waves by the ultrasonic transducers (3) and (2) on the reception side, the ultrasonic transducers (2) on the transmission side next. ) A method of setting a certain delay time t from (3) to transmitting an ultrasonic wave is known. According to this, the ultrasonic wave transmitted from the transmitting-side ultrasonic transducers (2) and (3) for the third time and the above-described ultrasonic wave transmitted for the first time from the transmitting-side ultrasonic transducers (2) and (3). It is possible to prevent the reflected ultrasonic waves from overlapping.
[0009]
However, in the above-described conventional method, the period from reception of ultrasonic waves by the ultrasonic transducers (3) and (2) on the reception side to transmission of ultrasonic waves by the ultrasonic transducers (2) and (3) on the transmission side In order to measure the delay time t, a timer using an electronic circuit made of an expensive crystal or the like is used, so that there is a problem that it is not economical to apply to a general-purpose flow meter.
[0010]
The present invention has been made in view of the above-mentioned problems, and can accurately measure the delay time in the sing-around method without using expensive electronic components. For the purpose of provision.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the present invention arranges ultrasonic transducers on the upstream side and downstream side of the measurement fluid flowing through the ultrasonic flow velocity measuring tube, and generates ultrasonic waves from the respective ultrasonic transducers. An ultrasonic flow velocity measuring method for transmitting and receiving transmitted ultrasonic waves to each other and measuring a flow velocity based on a difference in propagation times of the ultrasonic waves,
After a certain delay time has elapsed since the ultrasonic wave transmitted from the ultrasonic transducer on the transmission side was received by the ultrasonic transducer on the reception side, the ultrasonic wave is transmitted from the ultrasonic transducer on the transmission side again. Repeated several times in succession, and measures the total time from when an ultrasonic wave is first transmitted from the transmitting ultrasonic transducer to when the ultrasonic wave is received by the receiving ultrasonic transducer after a predetermined number of transmissions. However, when obtaining the propagation time of the ultrasonic wave based on the total time,
The delay time is measured by counting the wave number of the received wave corresponding to the ultrasonic wave received by the ultrasonic transducer on the receiving side.
[0012]
According to this, since the delay time in the sing-around method is measured by counting the number of received waves, the delay time in the sing-around method can be accurately measured without using expensive electronic components. For this reason, it is possible to accurately measure the propagation time of ultrasonic waves at low cost, and as a result, the method can be applied to a general-purpose flow meter very economically.
[0013]
Further, according to the present invention, ultrasonic transducers are arranged on the upstream side and the downstream side of the measurement fluid flowing in the ultrasonic flow velocity measuring tube, and the ultrasonic transducers generate and transmit ultrasonic waves to and from each ultrasonic transducer. An ultrasonic flow velocity measuring apparatus that receives ultrasonic waves from each other and measures a flow velocity based on a difference in propagation times of the ultrasonic waves,
After a certain delay time has elapsed since the ultrasonic wave transmitted from the ultrasonic transducer on the transmission side was received by the ultrasonic transducer on the reception side, the ultrasonic wave is transmitted from the ultrasonic transducer on the transmission side again. Repeated several times in succession, and measures the total time from when an ultrasonic wave is first transmitted from the transmitting ultrasonic transducer to when the ultrasonic wave is received by the receiving ultrasonic transducer after a predetermined number of transmissions. Then, the propagation time of the ultrasonic wave is obtained based on the total time,
The receiving-side ultrasonic transducer is provided with measuring means for measuring the delay time by counting the number of received waves corresponding to the received ultrasonic waves.
[0014]
According to this, the ultrasonic flow velocity measuring method can be realized easily and reliably.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the present invention will be described.
[0016]
FIG. 1 shows an ultrasonic flow velocity measuring apparatus for carrying out the present invention. In FIG. 1, (1) is a flow velocity measuring tube, (2) and (3) are ultrasonic transducers arranged at a predetermined distance upstream and downstream in the flow direction, and (4) generates a drive pulse. Drive pulse generation circuit, (5) is a reception amplification circuit that outputs a reception wave when ultrasonic waves are received by the ultrasonic transducers (2) and (3), and (6) is an ultrasonic transducer (2) (3) And a switching circuit for switching the connection between the drive pulse generating circuit (4) and the amplifier circuit (5), which are the same as those shown in FIG.
[0017]
In this embodiment, a zero cross detection circuit (7) is provided on the output side of the reception amplifier circuit (5). As shown in FIG. 3, the zero-cross detection circuit (7) detects each zero-crossing time point of the received wave output from the receiving circuit (5), and a delay time measurement counter (described later) at each zero-crossing time point. 8) and a circuit for transmitting a zero cross signal to the propagation time measurement counter (9).
[0018]
A delay time measuring counter (8) is provided on one output side of the zero cross detection circuit (7), and the drive pulse generating circuit (4) is provided on the output side of the delay time measuring counter (8). Provided, and constitutes a feedback loop.
[0019]
As shown in FIG. 3, the delay time measuring counter (8) calculates the wave number of the received wave from the time when the received wave starts output based on each zero cross signal transmitted from the zero cross detection circuit (7). This circuit counts and transmits a drive signal to the drive pulse generation circuit (4) when a predetermined wave number is counted. That is, since the delay time measuring counter (8) counts a predetermined wave number in the received wave, the period 2T0 of the received wave is constant, so (predetermined wave number) × (1/2 period T0 of the received wave). ) Is measured. Therefore, there is a certain delay from the time when the ultrasonic wave is received by the ultrasonic transducers (3) and (2) on the reception side until the ultrasonic wave is transmitted from the ultrasonic transducers (2) and (3) on the transmission side. Time t can be set.
[0020]
For example, when the delay time is set to a time corresponding to eight received waves, the delay time measuring counter (8) sets the wave number of the received wave one by one every time a zero cross signal is received from the zero cross detection circuit (7). If the drive signal is transmitted to the drive pulse generation circuit (4) at the time of counting and the number of received waves (8 waves) is counted, (8 waves) × (1/2 period T0 of received waves) = 8T0 This means that the delay time is measured.
[0021]
Thus, since the delay time t in the sing-around method is measured by counting the number of received waves, the delay time t in the sing-around method can be accurately measured without using expensive electronic components. Therefore, as described later, it is possible to accurately measure the propagation time τ of ultrasonic waves at a low cost, and it becomes possible to apply the method to a general-purpose flow meter very economically.
[0022]
On the other hand, a clock circuit (9) is provided on the output side of the drive pulse generation circuit (4). This clock circuit (9) is a circuit that continuously outputs a clock wave having a constant period in synchronization with the time point when the ultrasonic waves are first transmitted from the ultrasonic transducers (2) and (3).
[0023]
A propagation time measurement counter (10) is provided on the output side of the clock circuit (9) and the zero cross detection circuit (7). This propagation time measurement counter (10) starts from the time when the first ultrasonic wave is transmitted from the ultrasonic transducer (2) (3) to the ultrasonic transducer (3) (2). This is a circuit that counts the clock wave output from the clock circuit (9) until the time point when the ultrasonic wave is received. The count value N of this clock wave is transmitted to the arithmetic circuit (11) described later. The propagation time measurement counter (10) receives the nth ultrasonic wave from the ultrasonic transducers (3) and (2) based on the zero cross signal transmitted from the zero cross detection circuit (7). Specify the point in time.
[0024]
An arithmetic circuit (11) is provided on the output side of the propagation time measurement counter (10). The arithmetic circuit (11) is a circuit for obtaining the ultrasonic wave propagation time based on the count value N transmitted from the counter (10), and executes the calculations of the following equations [1] and [2].
T = Ts × N ... [1]
T: Total time from when the first ultrasonic wave is transmitted until the nth ultrasonic wave is received Ts: Clock wave cycle N: Clock wave count value In the above equation [1], the count value Is the wave number of the clock wave output from the clock circuit (9) from when the first ultrasonic wave is transmitted to when the nth ultrasonic wave is received, so the clock wave period Ts is included in this count value. Is multiplied by the total time from when the first ultrasonic wave is transmitted until the nth ultrasonic wave is received.
[0025]
[tau] = {T- (n-1) * t} / n [2]
τ: Ultrasonic propagation time t: Delay time n: Number of ultrasonic transmissions In the above equation [2], the first ultrasonic transmission is excluded from the n ultrasonic transmissions (n− 1) A delay time t is generated at each transmission of each ultrasonic wave, and the ultrasonic wave is obtained by subtracting the delay time sum (n−1) × t from the total time T obtained by the above equation [1]. By subtracting the ultrasonic propagation time sum {T− (n−1) × t} by the number of ultrasonic transmissions n, The propagation time τ of the sound wave can be obtained.
[0026]
Next, an ultrasonic flow velocity measuring method using the apparatus shown in FIG. 1 will be described.
[0027]
First, a drive pulse is driven from the drive pulse generation circuit (4), an ultrasonic wave is transmitted from the upstream ultrasonic transducer (2), and in synchronization with the transmission, the clock circuit (9) has a constant cycle Ts. The clock wave is output continuously.
[0028]
When the ultrasonic wave transmitted from the upstream ultrasonic transducer (2) is received by the downstream ultrasonic transducer (3), the received wave corresponding to the ultrasonic wave is received from the reception amplification circuit (5). Is output by the zero-cross detection circuit (7), and the zero-cross signal is sent to the delay time measurement counter (8) and the propagation time measurement counter (9) at each zero-cross time point. Send.
[0029]
As shown in the figure, the delay time measurement counter (8) is based on each zero cross signal transmitted from the zero cross detection circuit (7), and the wave number of the received wave (for example, 8 When the predetermined wave number is counted, a drive signal is transmitted to the drive pulse generation circuit (4) to thereby obtain a delay time of (predetermined wave number) × (1/2 period T0 of the received wave). t is measured. Therefore, there is a certain delay from the time when the ultrasonic wave is received by the ultrasonic transducers (3) and (2) on the reception side until the ultrasonic wave is transmitted from the ultrasonic transducers (2) and (3) on the transmission side. Time t can be set.
[0030]
On the other hand, the propagation time measurement counter (10) receives the nth ultrasonic wave at the ultrasonic transducers (3) and (2) based on the zero cross signal transmitted from the zero cross detection circuit (7). Specify the time point until. Then, the propagation time measurement counter (10) receives the n-th signal from the ultrasonic transducers (2) and (3) to the ultrasonic transducers (3) and (2) from the time when the first ultrasonic wave is transmitted. The clock wave output from the clock circuit (9) is counted by the time until the ultrasonic wave is received, and the count value N is transmitted to the arithmetic circuit (11).
[0031]
The arithmetic circuit (11) obtains the ultrasonic propagation time τ based on the count value N transmitted from the propagation time measurement counter (10). That is, the arithmetic circuit (11) obtains the total time T from when the first ultrasonic wave is transmitted until the nth ultrasonic wave is received by the above equation [1]. Then, the arithmetic circuit (11) subtracts the delay time sum (n−1) × t from the total time T obtained by the above equation [1] in the above equation [2], thereby obtaining the ultrasonic propagation time sum. {T− (n−1) × t} is obtained, and the ultrasonic propagation time is divided by dividing the ultrasonic propagation time sum {T− (n−1) × t} by the number of ultrasonic transmissions n. Find τ.
[0032]
After obtaining the forward ultrasonic propagation time τ in this way, the switching circuit (6) is operated to operate the downstream ultrasonic transducer (3), the drive pulse generation circuit (4), and the upstream ultrasonic transducer. (2) and the reception amplifier circuit (5) are connected to each other, and the ultrasonic propagation time τ ′ in the reverse direction is obtained in the same manner as described above. After that, the flow velocity of the fluid is obtained based on the difference in propagation time (τ′−τ) between the ultrasonic waves in the forward direction and the backward direction, and the flow rate of the fluid is further obtained as necessary.
[0033]
In this embodiment, the case where the period of the received wave is constant has been described. However, the present invention is applicable even when the period of the received wave is not constant due to the natural frequencies of the ultrasonic transducers on the transmission side and the reception side. That is, even if the period of the received wave is not constant, the waveform of the received wave at each time is substantially constant. Therefore, if the predetermined number of waves is counted in each received wave, the same delay time can always be measured.
[0034]
【The invention's effect】
According to the first aspect of the present invention, the delay time in the sing-around method is measured by counting the number of received waves, so that the delay time in the sing-around method is accurately measured without using expensive electronic components. be able to. For this reason, it is possible to accurately measure the propagation time of ultrasonic waves at low cost, and as a result, the method can be applied to a general-purpose flow meter very economically.
[0035]
According to the invention which concerns on Claim 2, according to the said ultrasonic flow velocity measuring method, it is realizable easily and reliably.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an example of an ultrasonic flow velocity measuring apparatus for carrying out the present invention.
FIG. 2 is a diagram illustrating a relative relationship between received waves of ultrasonic waves.
FIG. 3 is an enlarged view showing a received wave of ultrasonic waves.
FIG. 4 is a block diagram showing a conventional ultrasonic flow velocity measuring apparatus.
FIG. 5 is a diagram showing a relative relationship between reception waves of conventional ultrasonic waves.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Flow velocity measuring tube 2, 3 ... Ultrasonic vibrator 4 ... Drive pulse generation circuit 5 ... Reception amplification circuit 6 ... Switching circuit 7 ... Zero cross detection circuit 8 ... Delay Counter for time measurement 9... Clock circuit 10... Counter for propagation time measurement 11.

Claims (2)

Ultrasonic transducers are arranged on the upstream and downstream sides of the measurement fluid flowing through the ultrasonic flow velocity measuring tube, respectively, and ultrasonic waves are generated and transmitted from the ultrasonic transducers, and the transmitted ultrasonic waves are mutually transmitted. An ultrasonic flow velocity measuring method for receiving and measuring a flow velocity based on a difference between propagation times of the ultrasonic waves,
After a certain delay time has elapsed since the ultrasonic wave transmitted from the ultrasonic transducer on the transmission side was received by the ultrasonic transducer on the reception side, the ultrasonic wave is transmitted from the ultrasonic transducer on the transmission side again. Repeated several times in succession, and measures the total time from when an ultrasonic wave is first transmitted from the transmitting ultrasonic transducer to when the ultrasonic wave is received by the receiving ultrasonic transducer after a predetermined number of transmissions. However, when obtaining the propagation time of the ultrasonic wave based on the total time,
An ultrasonic flow velocity measuring method, wherein the delay time is measured by counting the wave number of a received wave corresponding to an ultrasonic wave received by an ultrasonic transducer on a receiving side. Ultrasonic transducers are arranged on the upstream and downstream sides of the measurement fluid flowing through the ultrasonic flow velocity measurement tube, respectively, and generate and transmit ultrasonic waves from the ultrasonic transducers, and transmit the transmitted ultrasonic waves to each other. An ultrasonic flow velocity measuring device that receives and measures a flow velocity based on a difference in propagation time of the ultrasonic waves,
After a certain delay time has elapsed since the ultrasonic wave transmitted from the ultrasonic transducer on the transmission side was received by the ultrasonic transducer on the reception side, the ultrasonic wave is transmitted from the ultrasonic transducer on the transmission side again. Repeated several times in succession, and measures the total time from when an ultrasonic wave is first transmitted from the transmitting ultrasonic transducer to when the ultrasonic wave is received by the receiving ultrasonic transducer after a predetermined number of transmissions. Then, the propagation time of the ultrasonic wave is obtained based on the total time,
An ultrasonic flow velocity measuring method, comprising: a measuring means for measuring the delay time by counting the wave number of a received wave corresponding to an ultrasonic wave received by an ultrasonic transducer on a receiving side.

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