JPH10307049A - Ultrasonic flow-velocity measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ultrasonic flow-velocity measuring method in which the difference in the propagation time between downstream-side received waves and upstream-side received waves can be measured by a method wherein triangular waves which rise proportionally rectilinearly are output in synchronization with a time in which the downstream-side received waves become a reference value and the voltage value of the triangular waves is found at a time when the upstream-side received waves become a reference value. SOLUTION: Ultrasonic waves and clock waves are output simultaneously from an upstream- side transmitter 2a, a downstream-side transmitter 2b and a clock circuit 6 by using the driving pulse of a pulse generation circuit 4. Forward ultrasonic waves are received by a downstream-side receiver 3a, and a forward received signal is output from a reception circuit 5. The clock waves from the output start of the ultrasonic waves up to the reception of the forward ultrasonic waves are counted by a counter 7, and the propagation time of the forward ultrasonic waves is found. An integrating circuit 9 outputs triangular waves in which a rise part becomes rectilinear by the received signal of the forward ultrasonic waves. Reverse ultrasonic waves are received by an upstream-side receiver 3b, and the received signal of the reverse ultrasonic waves is output from the reception circuit 5. The voltage value of the triangular waves at this time is held by a peak-hold circuit 11, and the difference in the propagation time between both received waves is found by a computing circuit 12 via an A/D conversion circuit 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic flow velocity measuring method for measuring gas and other fluids using ultrasonic waves.

[0002]

2. Description of the Related Art When determining the flow rate of a gas or other fluid, the flow rate of the fluid is measured continuously or periodically, and the flow rate is calculated based on the measured flow rate. As one of such fluid flow velocity measuring methods, a method using ultrasonic waves is known.

The principle of such an ultrasonic flow velocity measuring method is shown in FIG.
The description is as follows. In FIG.
(1) is a pipeline through which a fluid such as gas flows in the direction of the arrow. In this pipe (1), a transmitter (2a) and a receiver (3b) are arranged on the upstream side in the flow direction, and the transmitter (2b) is also provided on the downstream side at a predetermined distance. And a receiver (3a).

The transmitters (2a) and (2b) each include an ultrasonic transmitting element (not shown) composed of a vibrator and the receiver (3a).
(3b) is provided with an ultrasonic receiving element (not shown) composed of a vibrator, and the ultrasonic transmitting elements of these transmitters (2a) and (2b) are driven by driving pulses from a pulse generating circuit (4). And vibrates to generate and transmit an ultrasonic wave, while receiving the transmitted ultrasonic wave to receive the ultrasonic wave (3a).
The received wave when the ultrasonic receiving element of (3b) vibrates is output as an electric signal from the receiving circuit (5).

[0005] Generally, the propagation time t1 until the ultrasonic wave transmitted from the upstream transmitter (2a) in the forward direction to the flow is received by the downstream receiver (3a) is t1. = L / (C + V) ... [1] L: Pipe length C: Ultrasonic velocity V: Fluid velocity, and the direction opposite to the flow from the downstream transmitter (2b) The propagation time t2 until the ultrasonic wave transmitted to the receiver is received by the upstream receiver (3b) is expressed as t2 = L / (CV) (2), and these [1] From equation (2), the velocity V of the fluid
Since V = L / 2 × (1 / t1−1 / t2), the flow velocity V of the fluid can be derived by calculating the propagation times t1 and t2, respectively.

[0006] In the conventional ultrasonic flow velocity measurement, the propagation time t1 of the ultrasonic wave transmitted in the forward direction (forward ultrasonic wave) and the propagation time of the ultrasonic wave transmitted in the reverse direction (reverse ultrasonic wave). The method of measuring t2 separately using a clock circuit has been adopted.

[0007]

However, when the forward and backward propagation times t1 and t2 are separately measured, the propagation times t1 and t2 vary, and several tens or more are required to obtain an accurate propagation time. Measurement data of the propagation time was required. Therefore, there are drawbacks in that the labor and time required for the measurement and the power consumption of the measurement circuit increase.

Further, to measure the propagation time of a fluid having a wide flow rate from a large flow rate to a small flow rate, an expensive clock circuit having a large frequency (small cycle) is used in accordance with a small flow rate having a small propagation time difference. There was a disadvantage that it had to be done.

As a specific example, the maximum measured flow rate is 5 m3 / h, the minimum measured flow rate is 5 l / h, the maximum measured flow rate (V1) is 10 m / s, the minimum measured flow rate is (V2), 10 mm / s, and the sectional area of the pipe is 1.38 cm3. Assuming that the length (L) is 20 cm and the ultrasonic flow velocity (C) is 330 m / s, the propagation times t1 and t1 of the forward and backward ultrasonic waves at the large flow rate and the small flow rate are calculated from the above equations [1] and [2].
t2 is as follows.

Propagation time t1 Propagation time t2 Propagation time difference t1-t2 Large flow rate (10 m / s) 588.235 μs 625.000 μs 36.675 μs Small flow rate (10 mm / s) 606.042 μs 606.079 μs 0.037 μs The propagation time of the normal frequency 1MHz (period 1μs)
If you try to measure using the cheap clock circuit of
As can be seen from the above table, the propagation time of a large flow rate can be measured with sufficient accuracy, but the propagation time of a small flow rate is the propagation time difference (0.037 μs) due to the period of the clock circuit (1 μm).
s) It cannot be measured accurately because it is smaller.
Therefore, in order to accurately measure the propagation time of a small flow rate, an expensive clock circuit having a large frequency (at least 100 MHz is required in the above example) must be prepared separately.
The propagation time of a fluid having a wide flow rate from a large flow rate to a small flow rate cannot be measured using an inexpensive clock circuit having a small frequency.

The present invention has been made in view of such a technical background, and reduces the number of times of measuring the propagation time of an ultrasonic wave, and saves labor, time loss, and power consumption of a measurement circuit for measurement. It is an object of the present invention to provide an ultrasonic flow velocity measurement method capable of measuring the propagation time of a fluid having a wide flow rate from a large flow rate to a small flow rate with an inexpensive clock circuit, and thus enabling a highly accurate flow velocity measurement. .

[0012]

To achieve the above object, an ultrasonic flow velocity measuring method according to claim 1 of the present invention comprises:
Transmitters and receivers are respectively arranged on the upstream side and the downstream side of the measurement fluid, and ultrasonic waves are generated and transmitted almost simultaneously by applying a drive pulse to the ultrasonic transmission element of each of the transmitters,
In the ultrasonic flow velocity measuring method in which the transmitted ultrasonic waves are mutually received by the receiver and the flow velocity is measured based on the propagation time of both the received waves, the ultrasonic wave is synchronized with the time when the received wave on the downstream side reaches the reference value. A triangular wave whose rising edge forms a proportional straight line is separately output, and immediately after that, the voltage value of the triangular wave at the time when the received wave on the upstream side reaches the reference value is proportional to the voltage value and time in the proportional linear portion of the triangular wave. From the relationship, a difference between the propagation times of both received waves is obtained.

[0013] Thus, it is possible to accurately determine any propagation time difference from a long one to a minute one. Therefore, by adding or subtracting the propagation time difference and the propagation time of either the forward ultrasonic wave or the backward ultrasonic wave measured by the clock circuit, the other propagation time can be accurately obtained by suppressing the dispersion. Therefore, it is possible to reduce the number of times of measurement of the propagation time required for obtaining an accurate propagation time.

Further, since the clock circuit may be used only for measuring the propagation time of either the forward ultrasonic wave or the backward ultrasonic wave, the clock circuit is also used for measuring the propagation time of a fluid having a small flow rate and a small flow rate. It is possible to use an inexpensive clock circuit having a small size.

According to a second aspect of the present invention, there is provided an ultrasonic flow velocity measuring method, wherein a time when a downstream received wave reaches a reference value is set as a reference time.
A plurality of reference times are set for one received wave, the triangular wave is separately output in synchronization with each reference time, and immediately thereafter, the triangular wave at the time when the upstream received wave reaches the reference value is set. From the respective voltage values and the proportional relationship between the voltage value and the time in each proportional linear portion of the triangular wave, a difference between a plurality of propagation times in one transmission is obtained. The number of times of transmission of both ultrasonic waves necessary for obtaining a good propagation time can be further reduced.

The ultrasonic flow velocity measuring method according to the third aspect is characterized in that the inclination of the proportional linear portion of the triangular wave is selected in accordance with the magnitude of the propagation time difference caused by the difference in the flow rate of the fluid. In addition, various propagation time differences caused by the difference in the flow rate of the fluid can be obtained with higher accuracy.

[0017]

FIG. 1 shows an ultrasonic flow velocity measuring apparatus for carrying out the present invention. In FIG.
(1) is a pipeline, (2a) and (2b) are transmitters arranged upstream and downstream in the flow direction, and (3a) and (3b) are predetermined distances from the transmitters (2a) and (2b). (4) is a pulse generation circuit that generates forward and reverse drive pulses with respect to the flow, and (5) is a receiver (3a) or (3b) Is a receiving circuit that outputs a forward receiving signal or a backward receiving signal when receiving an ultrasonic wave, and these are the same as those shown in FIG.

In this embodiment, a clock circuit (6) is provided on the transmitting side, and this clock circuit (6) includes the transmitters (2a) and (2b) as shown in FIG. And outputs a clock wave (L) having a period T in synchronization with the time (A) at which the ultrasonic wave is transmitted from the oscilloscope.

On the output side of the clock circuit (6), a counter (7) and an arithmetic circuit (8) are provided. The counter (7) receives the forward ultrasonic wave from the receiving circuit (3a) from the time (A) at which the clock wave (L) starts to be output from the clock circuit (6), and Counting the number of clock waves (L) output from the clock circuit (6) within the time until the time (B) at which the forward reception signal is output, that is, within the propagation time (t1) of the forward ultrasonic wave. It is. The arithmetic circuit (8)
Calculates and outputs the forward propagation time (t1) based on the number of clock waves (L) counted by the counter (7), and is specifically expressed by the following equation.

(Time t1) = (period T of clock wave (L)) × (wave number of output clock wave (L) -1)
[3] As can be seen from FIG. 2 (d), the time error (DB) is calculated between the forward propagation time (AD) obtained by equation [3] and the actual forward propagation time (AB). However, since this time error (DB) is minute (even the largest error is the period T of the clock wave) compared to the propagation time (AB), the forward propagation time (A
D) is assumed to be the same as the actual propagation time (AB).

On the other hand, an integrating circuit (9) is provided on the receiving side, and as shown in FIG. 2 (c), the forward ultrasonic wave is received by the receiver (3a) and received from the receiving circuit (5). In synchronism with the time (B) at which the forward reception signal is output, a triangular wave (P) having a period T0 with a gentle rise and a steep fall and a peak value V0 is output. The output value of the integration circuit (9) indicates the voltage value of the capacitor in the circuit. When the capacitor is charged, the voltage value of the capacitor and the time have a proportional relationship. Is part of the proportional line.

A peak hold circuit (10) is provided on the output side of the integration circuit (9).
This is because the backward ultrasonic wave is received by the receiver (3b) and the receiving circuit (5) outputs the backward receiving signal (B).
In (1), the voltage value of the capacitor, which is the output value of the integration circuit (9), is held. In this embodiment,
As shown in FIG. 2C, at the time (B ′) at which the reverse direction received signal is output from the receiving circuit (5), the output value of the integrating circuit (9) is the voltage of the capacitor in the integrating circuit (9). This is a value corresponding to the value V, and therefore this value V is to be held in the peak hold circuit (10).

Further, on the output side of the peak hold circuit (10), an A / D conversion circuit (11) for digitally converting the voltage value V held by the peak hold circuit (10) is provided. Is provided with an arithmetic circuit (12). The arithmetic circuit (12) calculates a propagation time difference τ between the forward received wave and the backward received wave based on the voltage value V accurately measured by the A / D conversion.
That is, as shown in FIG. 3, since the time and the voltage value at the rising portion of the triangular wave (P) are proportional to each other, τ / T0 = V / V0... Is represented by the following equation.

.Tau. = (V.times.T0) / V0 (5) Since T0 and V0 are known with the period and peak value of the triangular wave (P), respectively, the integration when the backward receiving signal is output. If the voltage value V of the capacitor in the circuit (9) is known, the propagation time difference τ can be obtained, and the arithmetic circuit (12) performs these processes.

An adder (13) is provided on the output side of the operation circuits (8) and (12).
By adding the respective measurement times t1 and τ output from 2), the propagation time t2 of the backward ultrasonic wave is obtained and output.

Next, an ultrasonic measuring method using the apparatus shown in FIG. 1 will be described. The driving pulse is driven from the pulse generation circuit (4) to transmit the upstream and downstream transmitters (2a) (2a).
The ultrasonic wave is simultaneously transmitted from b), and a clock wave (L) is output from the clock circuit (6) in synchronization with the ultrasonic wave.

Then, of the transmitted ultrasonic waves,
When the forward ultrasonic wave is received by the downstream transducer (3a), the receiving circuit (5) outputs a forward reception signal. At this time, since the clock circuit (6) outputs N clock waves (L) as shown in FIG. 2D, the clock wave (L) starts to be output by the counter (7). The wave number N of the clock wave (L) from the time (A) to the time (B) at which the forward ultrasonic wave is received is counted. The propagation time t1 of the forward ultrasonic wave is calculated by the arithmetic circuit (8) based on the wave number N of the clock wave (L).
Is calculated. In this embodiment, the wave number of the clock wave is N
When it is input to the arithmetic circuit (8), the arithmetic circuit (8) performs the operation of the equation [3], and the propagation time t1 of the forward ultrasonic wave is (N-1) T and the output is Is done.

On the other hand, at time (B) at which the forward receiving signal is output from the receiving circuit (5), the integrating circuit (9) outputs a triangular wave (P).

Thereafter, when the backward ultrasonic wave is received by the upstream transducer (3b), a backward receiving signal is outputted from the receiving circuit (5), and the triangular wave (P) at this time is shown in FIG. Since the voltage value is V as shown in FIG. 2 (c), the voltage value V of the capacitor in the integration circuit (8) is held by the peak hold circuit (11). After the held output value V is read by the A / D conversion circuit (12), it is input to the arithmetic circuit (12) and the propagation time difference τ is output. In this embodiment, the propagation time is represented by equation [5].

Then, the output value t1 from the arithmetic circuit (8)
And the output value .tau. From the arithmetic circuit (12) are input to the adder circuit (13), and the adder circuit (13) outputs the propagation time t2 of the backward ultrasonic wave, which is expressed by the following equation.

T 2 = t 1 + τ = (N−1) T + (V × T 0) / V 0 (6) After the propagation times t 1 and t 2 of the forward ultrasonic wave are measured in this manner, a reset circuit (not shown) is used. The capacitor of the integrating circuit (9) is discharged to prepare for the next measurement.

Thus, in the method of measuring the propagation time difference τ, not only a long propagation time difference but also a minute propagation time difference can be accurately obtained. Therefore, as described above, the propagation time t2 of the backward received wave is suppressed by adding the propagation time difference τ and the propagation time t1 of the forward ultrasonic wave obtained by using the clock circuit (6). Therefore, it is possible to reduce the number of measurements required to obtain an accurate propagation time.

Further, the clock circuit (6) having large power consumption may be used only for measuring the propagation time of one of the ultrasonic waves (in this embodiment, only the measurement of the propagation time t1 of the forward ultrasonic wave). Use), and the power consumption for the measurement can be reduced.

Further, as described above, since the propagation time can be measured by the clock circuit using only one of the forward ultrasonic wave and the backward ultrasonic wave, the propagation time of a small flow rate fluid having a small propagation time difference can be measured. An inexpensive clock circuit with a small frequency (long cycle) can be used for measurement.

In the above embodiment, the time when the triangular wave is output from the integrating circuit (9) is the time when the forward received wave reaches the receiver (3a), and the time when the voltage value V of the triangular wave is measured is the time when the backward received wave is measured. The triangular wave is output when the triangular wave is output. When the forward received wave reaches a reference value such as a zero crossing point, the measurement timing of the voltage value V of the triangular wave is determined by the reverse received wave. Immediately after that, the reference value may be reached.

In particular, as shown in the embodiment of FIG.
At each time (B1, B2, B3, B4, B5,...) At which the rising portion of the forward received wave (W) reaches the zero crossing point, the integration circuit (9) synchronizes with the triangular wave (P1).
, P2, P3, P4, P5,...), And immediately after that, each time (B'1, B'2, B'3) at which the rising portion of the backward received wave (W ') reaches the zero cross point. , B'4, B
'5,...), The respective voltage values (V1, V2) of the triangular wave.
, V3, V4, V5,...), The respective propagation time differences (τ1, τ2, τ3, τ4, τ5,. You can ask. For this reason, since a plurality of accurate propagation time differences can be obtained by one transmission of both ultrasonic waves, it is possible to further reduce the number of transmissions of both ultrasonic waves necessary for obtaining an accurate propagation time. Become. Further, the period and peak value of the triangular wave used for obtaining the propagation time difference are T0 and V0, respectively, but are not limited to these values. That is, the slope of the triangular wave may be selected in a plurality of stages by preliminarily measuring the approximate flow rate of the fluid and switching the integration circuit according to the flow rate. For example, in the case of measuring the propagation time in a fluid having a large flow rate, as shown in FIG. 5A, a triangular wave having a gradual slope of the proportional linear portion (a long period TL) is selected, and a triangular wave within the propagation time difference τ is selected. Is not terminated. On the other hand, in the case of the propagation time measurement in a small flow rate fluid, a triangular wave having a steep slope (short period Ts) of the proportional linear portion is selected as shown in FIG. It is better to obtain it with higher accuracy. Then, a more accurate transit time difference that matches the flow rate of the fluid, and thus a more accurate transit time, can be obtained. In each of the above embodiments, the propagation time of the forward ultrasonic wave is obtained by the clock circuit, but the propagation time of the backward ultrasonic wave is obtained by the clock circuit, and the propagation time difference is subtracted therefrom to obtain the propagation time of the forward ultrasonic wave. The time may be obtained.

[0037]

The ultrasonic flow velocity measuring method according to claim 1 is
As described above, in synchronization with the time when the downstream received wave reaches the reference value, a separate triangular wave whose rising edge forms a proportional straight line is output separately, and immediately after that, the time when the upstream received wave reaches the reference value is obtained. From the voltage value of the triangular wave and the proportional relationship between the voltage value and the time in the proportional linear portion of the triangular wave, the difference between the propagation times of the two received waves is obtained. It is possible to accurately determine any propagation time difference up to. Therefore, by adding or subtracting the propagation time difference and the propagation time of either the forward ultrasonic wave or the backward ultrasonic wave measured by the clock circuit, the other propagation time can be accurately obtained by suppressing the dispersion. Therefore, it is possible to reduce the number of times of measurement of the propagation time required for obtaining an accurate propagation time. Therefore, labor, time loss, and power consumption required for the measurement can be suppressed, and an economical and highly accurate flow velocity measurement can be performed.

Further, since the clock circuit consuming a large amount of power may be used only for measuring the propagation time of one of the ultrasonic waves, the power consumption for the measurement can be reduced.

Further, as described above, since the clock circuit may be used only for measuring the propagation time of one of the ultrasonic waves, it is inexpensive even when measuring the propagation time of a small flow rate fluid having a small propagation time difference. A simple clock circuit can be used. As a result, an inexpensive clock circuit can be used for measuring the propagation time of a fluid having a wide flow rate from a large flow rate to a small flow rate.

In the ultrasonic flow velocity measuring method according to a second aspect, a plurality of reference times are set for one received wave with the time when the downstream received wave reaches a reference value as a reference time. The triangular wave is separately output in synchronization with each reference time, and immediately thereafter, each voltage value of the triangular wave at the time when the received wave on the upstream side reaches the reference value, and the voltage value and the voltage value of each proportional straight line portion of the triangular wave Since the difference between a plurality of propagation times in one transmission is determined from the proportionality of time, the number of transmissions of both ultrasonic waves required to obtain an accurate propagation time is more reduced. Can be reduced. Therefore, the labor, time loss, and power consumption required for the measurement can be suppressed to be lower, and the flow velocity can be measured more economically.

The ultrasonic flow velocity measuring method according to the third aspect is characterized in that the inclination of the proportional linear portion of the triangular wave is selected in accordance with the magnitude of the propagation time difference caused by the difference in the flow rate of the fluid. In addition, various propagation time differences caused by differences in fluid flow rates can be determined more accurately.
Therefore, a more accurate propagation time can be obtained, and a more accurate flow velocity measurement can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of an ultrasonic flow velocity measuring device for carrying out the invention of claim 1;

FIG. 2 is a diagram showing a relative relationship between both received waves, a clock wave output from a clock circuit, and a triangular wave output from an integration circuit in the apparatus of FIG. 1;

FIG. 3 is an enlarged view of a portion I in FIG. 2;

FIG. 4 is a diagram showing a relative relationship between both received waves and a triangular wave output from an integration circuit when the invention of claim 2 is implemented.

FIG. 5 is a diagram showing a relative relationship between both received waves and a triangular wave output from an integrating circuit when the invention of claim 3 is implemented.

FIG. 6 is a block diagram showing an example of an ultrasonic flow velocity measuring device for implementing a conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Pipe line 2a, 2b ... Transmitter 3a, 3b ... Receiver

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akio Tomita 4-1-2, Hirano-cho, Chuo-ku, Osaka-shi Inside Osaka Gas Co., Ltd. (72) Inventor Tetsuya Yasuda 2- 10-16 Higashi-Kobashi, Higashi-Nari-ku, Osaka-shi Kansai Gas Meter Co., Ltd. (72) Inventor Akio Kono 2-10-16 Higashikobashi, Higashi-Nari-ku, Osaka-shi Kansai Gas Meter Co., Ltd. (72) Eiji Nakamura 2-10-16 Higashi-Kobashi, Higashi-Nari-ku, Osaka Kansai Gas Meter Inside the corporation

Claims (3)

[Claims] 1. A transmitter and a receiver are respectively arranged on the upstream side and the downstream side of a measurement fluid, and a driving pulse is applied to an ultrasonic wave transmitting element of each of the transmitters to generate and transmit ultrasonic waves almost simultaneously. In the ultrasonic flow velocity measurement method in which the transmitted ultrasonic waves are mutually received by the receiver and the flow velocity is measured based on the propagation time of both received waves, the time at which the received wave on the downstream side reaches the reference value In synchronization with the triangular wave whose rising edge forms a proportional straight line, the voltage value of the triangular wave at the time when the received wave on the upstream side reaches the reference value immediately thereafter, the voltage value of the proportional linear portion of the triangular wave and An ultrasonic flow velocity measuring method, wherein a difference between propagation times of both received waves is obtained from a proportional relation of time. 2. A time when a downstream received wave reaches a reference value is set as a reference time, a plurality of reference times are set for one received wave, and the triangular wave is synchronized with each reference time. A single transmission is performed based on the respective voltage values of the triangular wave at the time when the received wave on the upstream side reaches the reference value immediately after that, and the voltage value and time in each proportional linear portion of the triangular wave at the time when the received wave reaches the reference value. 2. The method according to claim 1, wherein a difference between a plurality of propagation times is obtained. 3. The ultrasonic flow velocity measuring method according to claim 1, wherein the inclination of the proportional linear portion of the triangular wave is selected in accordance with the magnitude of the propagation time difference caused by the difference in the flow rate of the fluid.