JPH11326561A - Method for time measurement and for ultrasonic flow velocity measurement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for time measurement capable of accurately measuring such a time as transmission of ultrasonic and a method for ultrasonic velocity measurement accurately measuring velocity of fluid by using the time measurement method. SOLUTION: A triangular wave P is output synchronizing with ultrasonic wave reception. When a clock wave Wa comes in a certain time period immediately after that, ultrasonic wave is again generated and transmitted from a wave transmitter and a clock wave W is independently output synchronizing with the transmission and the clock wave is shifted for a half period and reversed. The triangular wave P is output synchronizing with the ultrasonic wave reception and at the rising of the reverse clock wave Wa' immediately after that, the electric potential V of the triangle wave P is measured. Then, by adding or subtracting the time corresponding to the half period of the clock wave W to the value substituting in a proportional linear equation indicating the slope of the triangular wave P, the fraction time (t) from the rising of the final clock wave Wf before reversal to the ultrasonic reception is calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time measuring method for accurately measuring a measuring time and an ultrasonic flow velocity measuring method using the time measuring method.

[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.

FIG. 2 shows the principle of such an ultrasonic flow velocity measuring method.
FIG. 7 is as follows.

[0004] In FIG. 7, (1) is a pipe through which a fluid such as gas flows in the direction of the arrow. In the pipeline (1), the transducers (2) and (3) are arranged at a predetermined distance upstream and downstream in the flow direction. Each of the transducers (2) and (3) serves as a transmitter and a receiver, and includes an ultrasonic transmitting / receiving element (not shown) composed of a vibrator. The element is driven by the driving pulse from the pulse generating circuit (4) to vibrate and generate and transmit an ultrasonic wave, while receiving the transmitted ultrasonic wave and receiving and transmitting the ultrasonic wave when the element vibrates. Are output as electric signals from the receiving circuit (5).

Then, as shown in FIGS. 2A and 2C,
A clock wave (W) is separately output from the clock circuit in synchronization with the transmission of the ultrasonic wave, and the number of clock waves (W) output from the time of transmission (A) to the time of reception (C) of the ultrasonic wave is counted. Thus, the time T from the transmission of the ultrasonic wave (A) to the rising of the last clock wave (Wf) before reception (B) is obtained. In FIGS. 2A and 2C, since three clock waves (L) having a period T0 are output, the time T is obtained as 3T0.

In addition, from the rising (A) of the last clock wave (Wf) before receiving the ultrasonic wave to the time of receiving the ultrasonic wave (C).
In order to obtain the fractional time t, a method using a triangular wave (P) disclosed in Japanese Patent Application No. 8-333407 filed prior to the present application is used. That is, as shown in FIG. 2D, the triangular wave (P) is synchronized with the ultrasonic wave reception (C).
Separately from the potential difference V at the rising edge (D) of the clock wave (Wa) immediately after the output of the triangular wave (P), and the proportional relationship between the potential difference and the time in the proportional linear portion of the triangular wave (P). The last clock wave (W
The fractional time t from the rise (f) of f) to the reception of the ultrasonic wave (C) is obtained.

[0007] The propagation time until the ultrasonic wave transmitted in the forward direction with respect to the flow from the upstream transducer (2) obtained in this way is received by the downstream transducer (3). The difference between the propagation time until the ultrasonic wave transmitted in the opposite direction to the flow from the downstream transducer (3) and the ultrasonic wave received by the upstream transducer (2) is related to the flow velocity. Therefore, the flow velocity of the fluid is measured by calculating the propagation time difference. In FIG. 7, reference numeral (6) denotes a switching circuit for switching the connection between each of the transducers (2) and (3) and the pulse generation circuit (4) and the reception circuit (5). After connecting the upstream transducer (2), the downstream transducer (3) and the receiving circuit (5), the propagation time from the upstream to the downstream is determined using the clock wave,
By the operation of the switching circuit (6), the pulse generating circuit (4) and the downstream transducer (3), and the upstream transducer (2) and the receiving circuit (5) are switched so as to be connected. In addition, the propagation time from the downstream side to the upstream side is also obtained by using a clock wave.

However, the triangular wave (P) generally generates noise for a certain period of time from its rise, and the hypotenuse of the triangular wave (P) at that time is not a straight line but a fine sawtooth wave. Therefore, if the clock wave (W) used for the potential difference measurement timing rises within the noise generation time, an error occurs in the measured potential difference, and there is a problem that the fractional time and the propagation time cannot be determined accurately.

Therefore, Japanese Patent Application No. 10-17303, filed prior to the present application, discloses that when a clock wave (W) used for measuring the potential difference rises after the lapse of the noise generation time, the timing for measuring the potential difference is determined. A shifting method has been proposed. That is, as shown in FIG.
When the clock wave (Wa) used for the potential difference measurement timing rises after a lapse of a fixed time (hatched portion in FIG. 8A) from the rise of the triangular wave (P), the triangular wave at the potential difference measurement timing similarly to the above. (P) potential difference V
Into the proportional linear expression representing the hypotenuse portion of the triangular wave (P), whereby the final clock wave (W
The fractional time t from the rising time B of FIG. On the other hand, when the clock wave (Wa) used for the potential difference measurement timing rises within the noise generation time (the hatched portion in FIG. 8B), the next clock wave (W)
b) The potential difference V of the triangular wave (P) at the rising edge E '
Is added to a proportional linear equation representing the hypotenuse portion of the triangular wave (P) and the cycle T0 of the clock wave (W) to add the fraction time t.

According to this method, even when the timing of measuring the potential difference of the clock wave (W) reaches the noise occurrence time, the fractional time t can be accurately obtained under certain conditions.

[0011]

However, when the clock wave (Wa) rises immediately after the output of the triangular wave, the next clock wave (Wb) rises in the negative region near the X-axis in FIG. In some cases, the clock wave (Wb) rises in a positive region near the X-axis with a slight fluctuation. Therefore, in the actual fractional time t, one cycle time T0 of the clock wave (W) is added to the value Y obtained by substituting the potential difference V of the potential E 'at the rising of the clock wave (Wb) into the proportional linear equation of the triangular wave (P). Since the clock wave (Wb) rises to the positive region of the X-axis, the fractional time t to be measured is equal to the potential difference V of E 'at the rise of the clock wave (Wb). The value Y substituted into the linear equation is the same, and an error corresponding to one cycle T0 of the clock wave (W) occurs in the fractional time t.

Further, a clock wave (W
When a) rises, the clock wave (Wa) is increased as described above.
May rise to a negative area near the X-axis with a little shaking. Therefore, the actual fractional time t should be the value Y obtained by substituting the potential difference V at the rising edge E of the clock wave (Wa) into the proportional linear equation of the triangular wave (P), but the clock wave (Wa) becomes X Since it rises in the negative area of the axis,
The measured fractional time t is a value (T0 + Y) obtained by adding one cycle of the clock wave to a value obtained by substituting the potential difference V at the rising edge E of the clock wave (Wa) into the proportional linear equation of the triangular wave (P).
In this case also, one cycle T of the clock wave in the fractional time t
An error of 0 hours occurs.

Therefore, when the clock wave (Wa) or (Wb), which is the timing for measuring the potential difference, rises in the vicinity of the X axis, one clock wave is generated between the actual fractional time and the fractional time obtained by the measurement. There is a defect that an error corresponding to a cycle occurs, and a large time error corresponding to one cycle of the clock wave also occurs with the propagation time. Such a drawback commonly occurs when obtaining not only the propagation time of the ultrasonic wave but also other measurement times.

The present invention has been made in view of such a technical background, and provides a time measuring method capable of accurately measuring a measuring time such as a propagation time of an ultrasonic wave.
It is an object of the present invention to provide an ultrasonic flow velocity measuring method for accurately measuring the flow velocity of a fluid using the time measuring method.

[0015]

To achieve the above object, an ultrasonic flow velocity measuring method according to the present invention outputs a clock wave (W) in synchronization with a start time A of a measuring time τ.
In the time measuring method for obtaining the measuring time τ by counting the number of clock waves (W) output until the ending time C of the measuring time τ, the ending time C of the measuring time τ
A triangular wave (P) is output in synchronization with the above, and when the timing E for measuring the potential difference determined by the rising or falling of the clock wave (Wa) immediately after the triangular wave (P) arrives within the predetermined time (CD) (FH), , A clock wave (W) is output in synchronization with the start time A of the measurement time τ, the clock wave (W) is inverted by shifting by a half cycle, and the triangular wave (P) is synchronized with the end time C of the measurement time τ. At the potential difference measuring timing E ′ determined by the rising or falling of the clock wave (Wa ′) immediately after the triangular wave (P).
Is measured, and a time T0 / 2 corresponding to a half cycle of the clock wave (W) is added to or subtracted from a value Y obtained by substituting the potential difference V into a proportional linear equation representing the hypotenuse of the triangular wave (P). Thus, the fractional time t from the rising or falling time B of the final clock wave (Wf) before the end time C of the measurement time τ to the end time C is obtained, and the wave number of the output clock (W) is counted. The measurement time τ by adding the fractional time t to the time T from the start time A of the measurement time τ to the rising or falling time B of the final clock wave (Wf). It is characterized by the following.

According to this method, when the potential difference measurement timing determined by the rise or fall of the clock wave (W) arrives within a predetermined time in which a measurement error easily occurs, the clock wave (W) is further increased. Since the potential difference of the triangular wave (P) is measured by shifting and inverting by a half cycle, the fractional time t is always utilized by using the stable intermediate portion of the triangular wave (P).
Can be obtained, and the measurement time τ can be obtained with high accuracy.

Further, a transmitter and a receiver are arranged on the upstream side and the downstream side of the measurement fluid, respectively, and a driving pulse is applied to an ultrasonic wave transmitting element of each of the transmitters to generate and transmit ultrasonic waves mutually. The propagation time from the transmission time to the reception time of the ultrasonic wave is obtained as the measurement time τ by setting the time to perform as the start time A and the time at which the transmitted ultrasonic waves are mutually received as the end time C, When measuring the flow velocity of the fluid based on the difference between the respective propagation times, the propagation time of the ultrasonic wave can be obtained with high accuracy, so that the flow velocity of the fluid can be accurately measured based on the difference between the respective propagation times.

[0018]

FIG. 1 shows an ultrasonic flow velocity measuring apparatus for carrying out the present invention. In FIG.
(1) is a pipeline, (2) and (3) are transducers arranged at a predetermined distance upstream and downstream in the flow direction, (4) is a pulse generation circuit that generates a drive pulse, and (5) ) Is a receiving circuit that outputs a reception signal when ultrasonic waves are received by the transducers (2) and (3), and (6) is a transceiver circuit (2) (3), a pulse generation circuit (4), and a receiving circuit. Switching circuits for switching the connection of the circuit (5), which are the same as those shown in FIG.

In this embodiment, a clock circuit (7) is provided on the transmission side, and the clock circuit (7) is provided with a transmitter / receiver (2) as shown in FIG.
In synchronization with the time (A) at which the ultrasonic wave is transmitted from (3),
It outputs a clock wave (W) having a period T0.

A counter (9) is provided on one output side of the clock circuit (7). The counter (9) receives the ultrasonic waves at the transmitter / receivers (2) and (3) from the time (A) at which the clock wave (W) starts to be output from the clock circuit (7) and receives the ultrasonic waves at the receiving circuit (5). ) To the time (C) at which the received signal is output, that is, within the propagation time (τ) of the ultrasonic wave, counts the number of clock waves (W) output from the clock circuit (7). is there.

The number of clock waves (W) counted by the counter (9) is calculated by the arithmetic circuit (10) of the microcomputer (I) provided on the output side of the counter (9).
Sent to. The arithmetic circuit (10) calculates the last clock wave (Wf) immediately before the output of the received signal from the time (A) when the clock circuit starts to be output from the clock circuit (7) based on the wave number of the clock wave (W). Is calculated and output to the addition circuit (14) until the time (B) at which is output, and specifically, the following operation is executed.

(Time T) = (Period T 0 of Clock Wave (W)) × (Number of Counted Clock Waves (W)) [1] On the receiving side, the output of the receiving circuit (5) A triangular wave generating circuit (8) is provided on the side. As shown in FIG. 2D, the triangular wave generating circuit (8) generates a triangular wave (P) having a sharp rise and a gentle fall in synchronization with reception of a reception signal from the reception circuit (5). The time (CG) from when the triangular wave (P) rises to when the triangular wave (P) reaches the reference voltage value E0 is set to T0 similarly to the cycle of the clock wave (W). The output value of the triangular wave generation circuit (8) indicates the potential difference of the capacitor in the circuit. When the capacitor is charged or discharged, the potential difference of the capacitor and time have a proportional relationship. Is a part of the proportional straight line, but noise is generated for a certain period of time after the fall starts, and the shape is a fine sawtooth.

A hold circuit (11) is provided on the output side of the triangular wave generation circuit (8). When the hold circuit (11) receives the hold signal from the AND circuit (15) to which the output signal of the triangular wave generation circuit (8) and the rising signal of the clock circuit (7) are input, the hold circuit (11) changes the potential difference V of the triangular wave (P). To keep. The potential difference V held by the hold circuit (11) is
After being digitally converted by an A / D conversion circuit (not shown), it is transmitted to the arithmetic circuit (12) of the microcomputer (I).

The arithmetic circuit (12) calculates the Y value by substituting the potential difference V transmitted from the hold circuit (11) into the X value of the following proportional linear equation [2].
The value is transmitted to the comparison circuit (13).

Y = aX−b (a = 9/8, b = 511)... [2] X: Potential difference V to be substituted For convenience, this proportional linear equation [2] is expressed by a voltage axis as shown in FIG. , And the time axis is the Y axis, and the coefficients a and b of this correction equation determine the shape of the triangular wave (P). In this embodiment, numerical values are set in parentheses of the value equation of the coefficients a and b and the proportional linear equation [2]. However, the present invention is not limited to these values.
When it is desired to obtain a fractional time using a triangular wave having a shape different from the triangular wave (P), the coefficients a and b are adjusted accordingly.
Should be set. In particular, Y by the proportional linear equation [2]
Since the calculation of the value is performed by the microcomputer, it is preferable that the value of the coefficient a be a value that facilitates the shift processing, such as a = 3/2, 5/4, 9/8, 17/16, or the like.

The comparison circuit (13) determines that the Y value is U 2 <Y
If <(T0−U1) is satisfied, that is, if the clock wave (Wa) rises during the safe time DF, its Y
The value is transmitted as it is to the addition circuit (14) provided on the output side as the fractional time t. When the Y value satisfies Y ≧ (T0−U1) or Y ≦ U2,
That is, when the clock wave (Wa) rises between the prohibition time CD or the prohibition time FH, the circuit changeover switches (20) and (21) are switched from the solid line to the broken line as shown in FIG. Is transmitted and received, and a new Y value is calculated by the clock inversion circuit (16) and the arithmetic circuit (17).

This clock inverting circuit (18) inverts the clock wave (W) output from the clock circuit (7) by shifting it by a half cycle. The clock inverting circuit (18) is shown in FIG. 2 (c). Such a clock wave (W ′) is output. Therefore, as shown in FIG. 4 or FIG. 5, the rising time E ′ of the clock wave (Wa ′) immediately after the output of the triangular wave (P) is equal to the falling time of the clock wave (Wa) before inversion. The clock wave (Wa ') always rises during the safe time DF. Then, the hold circuit (11) holds the potential difference V of the triangular wave at the rising time E 'of the clock wave (Wa') as described above,
After digital conversion is performed by an A / D conversion circuit (12) not shown, the potential difference V is transmitted to the switched arithmetic circuit (17).

The arithmetic circuit (17) newly calculates Y by the above equation [2] based on the newly transmitted potential difference V.
While calculating the value, the Y value is calculated by the following equation [3] or [4].
To calculate the Y ′ value.

<Original clock wave (Wa) is prohibited time CD
Y '= Y + T0 / 2... [3] <Case where original clock wave (Wa) rises during inhibition time FH (FIG. 5)>Y' = Y -T0 / 2 ... [4] As described above, when the original clock wave (Wa) rises during the prohibition time CD, the newly calculated Y value is changed to the half cycle T0 / 2 of the clock wave. Is added because the rising edge time E ′ of the clock wave (Wa ′) is the original clock wave (W) because the clock wave (W) is inverted as shown in FIG.
From the rising time E of a), the half cycle T0 / 2 of the clock wave
This is because the newly calculated Y value is smaller than the original Y value by half the period T0 / 2. Also,
In the case where the original clock wave (Wa) rises during the inhibition time FH, the half cycle T0 / 2 of the clock wave is subtracted from the newly calculated Y value as shown in FIG. W) is inverted, the rising time E 'of the clock wave (Wa') is earlier than the rising time of the original clock wave (Wa) by a half cycle T0 / 2 of the clock wave from the time E, and the newly calculated Y value is This is because the value is larger than the original Y value by a half period T0 / 2. The Y ′ value obtained by the above equation [3] or [4] represents the fractional time t from the rise of the final clock wave (Wf) of the original clock wave (W) to the reception of the ultrasonic wave.

The operation circuit (10) and the comparison circuit (1
3) and an adder circuit (1) on the output side of the arithmetic circuit (17).
4) is provided. The adding circuit (14) includes a time T from the transmission time A of the ultrasonic wave obtained by the arithmetic circuit (10) to the rising time B of the final clock wave (Wf), and the arithmetic circuit (12) or the arithmetic circuit ( The propagation time τ of the ultrasonic wave is obtained by adding the Y value or the Y ′ value that is the fractional time t obtained in 17).

Next, an ultrasonic measuring method using the apparatus shown in FIG. 1 will be described. First, a circuit changeover switch (20)
With (21) set to the position indicated by the solid line in FIG. 1, the drive pulse is driven from the pulse generation circuit (4), the ultrasonic wave is transmitted from the upstream transducer (2), and the clock is synchronized with it. A clock wave (W) is output from the circuit (7).

Thereafter, when the transmitted ultrasonic wave is received by the downstream transducer (3), a reception signal is output from the receiving circuit (5). At this time, the clock circuit (7)
2B, a clock signal (W) as shown in FIG. 2B is output. Therefore, the counter (9) outputs a received signal from the time (A) at which the clock wave (W) starts to be output. The number of clock waves (W) up to time (B) is counted.

Then, based on the wave number of the clock wave (W), the arithmetic circuit (10) generates the clock wave (W).
From the time (A) when the output of the last clock wave (W) starts.
The time T until the time (B) at which f) is output is calculated.
In this embodiment, the wave number of the clock wave (W) output from the clock circuit (7) is from the time (A) when the clock wave (W) starts to be output to the time (C) when the received signal is output. Since the number is three, when the wave number is input to the arithmetic circuit (10), the arithmetic circuit (10) uses the equation [1]
Is executed, and the time T is output as 3T0.
Note that the final clock wave (Wf) is not counted as the number of clock waves (W) because an ultrasonic wave is received in the middle thereof.

On the other hand, the transducer (3) receives the ultrasonic wave,
The triangular wave generating circuit (8) outputs a triangular wave (P) as shown in FIG. 2D in synchronization with the time (C) at which the receiving signal is output from the receiving circuit (5). This triangular wave (P) has noise for a certain time from its rise (C), and the proportional linear portion has a fine sawtooth shape.

Thereafter, when the clock wave (Wa) rises, the hold circuit (11) receives the hold signal from the AND circuit (15), so that at the rising time E of the clock wave (Wa), the triangular wave (P) is turned off. After holding the potential difference V and performing digital conversion by an A / D conversion circuit (not shown), the potential difference V is transmitted to the arithmetic circuit (12).

In this arithmetic circuit (12), the potential difference V
Is substituted into the X value of the above equation [2] to calculate the Y value, and transmits the Y value to the comparison circuit (13).

Then, the comparison circuit (17) to which the Y value has been transmitted, as shown in FIG.
(T0 -U1), that is, the clock wave (W
When a) rises during the safety time DF, the Y value is set as a fractional time t, and an addition circuit (1) provided on the output side is used.
The data is transmitted to 4) as it is. Further, when the Y value is as shown in FIG.
(A) or as shown in FIG. 5 (a), Y ≧ (T0−U
1) or when Y ≦ U2 is satisfied, that is, when the clock wave (Wa) rises during the inhibition time period CD or FH, the Y value is transmitted to the addition circuit (14) provided on the output side. Without using the circuit changeover switch (2
0) (21) is switched from the solid line to the broken line position, and the ultrasonic wave is transmitted and received again to newly calculate the Y value.

That is, as shown in FIG. 1, the circuit changeover switches (20) and (21) are switched from the solid line to the broken line position, and the ultrasonic wave is transmitted again, and the clock circuit (7) is synchronized with the transmission. Outputs a clock wave (W).
This clock wave (W) is input to a clock inversion circuit (18) and inverted by a half cycle, and is inverted.
Outputs a clock wave (W ′) as shown in FIG.

Then, as shown in FIG. 2D, a triangular wave (P) is output from the triangular wave generating circuit (8) in synchronization with the reception of the ultrasonic wave by the transmitter / receiver (3).

Thereafter, the clock wave (Wa ') immediately after the output of the inverted clock wave (W') is output as the original clock wave (Wa) as shown in FIG. 4 (b) or 5 (b).
It rises further by a half cycle T0 / 2. Therefore, the potential difference V at the rising time E 'of the clock wave (Wa') is held by the hold circuit (11), and A
After the digital conversion by the / D conversion circuit, it is transmitted to the switched arithmetic circuit (17).

Then, in the arithmetic circuit (17), FIG.
If the original clock wave (Wa) rises during the prohibition time CD as shown in (a), a Y 'value corresponding to the fractional time t is calculated by the above equations [2] and [3], and the addition circuit is performed. (1
Send to 4). In addition, when the original clock wave (Wa) rises during the prohibition time FH as shown in FIG. 5A, Y ′ corresponding to the fractional time t by the above equations [2] and [4].
The value is calculated and transmitted to the adding circuit (14) as described above.

The adding circuit (14) has a time T from the transmission time A of the ultrasonic wave obtained by the arithmetic circuit (10) to the rising time B of the final clock wave (Wf), and
Since the Y value or the Y ′ value, which is the fractional time t obtained by the arithmetic circuit (14) or the arithmetic circuit (19), is input, the time T is added to the Y value or the Y ′ value to obtain the ultrasonic wave. Find the propagation time τ.

Next, the switching circuit (6) switches the connection between the transmitter / receiver (3) to the transmitter and the transmitter / receiver (2) to the receiver, and measures the output of the received signal in the same manner as described above. The fractional time t 'is determined based on the output value V' of the triangular wave, and the propagation time τ 'of the ultrasonic wave in the reverse direction is determined. Then, since the two propagation times produce a propagation time difference (τ′−τ) that changes according to the fluid flow velocity, the fluid flow velocity is determined based on this, and the flow rate is further determined as necessary.

According to this method, when the clock wave (Wa), which is the potential difference measurement timing, rises to the inhibition time CD or the inhibition time GH, the clock wave (W) is further increased.
Is shifted by half a cycle to measure the potential difference V of the triangular wave (P), so that the fractional time t can always be obtained by using the stable intermediate portion of the triangular wave (P), and the propagation time τ of the ultrasonic wave is It can be obtained with high accuracy.

In this embodiment, the prohibition time is set at the rising portion and the skirt portion of the triangular wave. However, the prohibition time may be set to only one of them, or the size of the prohibition time may be set arbitrarily. However, when the prohibition time is set at the rising portion of the triangular wave, it is preferable to set the prohibition time longer than the noise generation time in order to prevent the potential difference measurement during the noise generation time of the triangular wave.

Further, the clock wave (Wa) has the prohibition time CD
Clock wave (W) output again when it rises
Has been shifted by a half cycle over the entire region, but only the clock wave directly used to measure the potential difference V of the triangular wave (P) may be inverted by a half cycle.

This time measuring method can be applied to the case where not only the propagation time of the ultrasonic wave but also other measuring times are obtained.

[0048]

According to the present invention, the triangular wave (P) is output in synchronization with the end time C of the measuring time τ, and the potential difference measuring timing E determined by the rising or falling of the clock wave (Wa) immediately thereafter is output. Arrives within the predetermined time (CD) (FH), outputs the clock wave (W) again in synchronization with the start time A of the measurement time τ, and inverts the clock wave (W) by shifting it by a half cycle. , A triangular wave (P) is output in synchronization with the end time C of the measurement time τ, and the clock wave (W
At a potential difference measuring timing E 'determined by the rise or fall of a'), the potential difference V of the triangular wave (P) is measured, and the potential difference V is converted into a proportional linear expression representing the hypotenuse of the triangular wave (P). Clock wave (W) for substituted value Y
By adding or subtracting a time T0 / 2 corresponding to a half cycle of the above, the fractional time from the rising or falling time B of the last clock wave (Wf) before the end time C of the measurement time τ to the end time C. t, the time T from the start time A of the measurement time τ obtained by counting the wave number of the output clock (W) to the rising or falling time B of the final clock wave (Wf), and the fraction Since the measurement time τ is obtained by adding the time t, the fractional time can always be obtained by using the stable intermediate portion of the triangular wave, and the measurement time can be obtained with high accuracy. .

Further, a transmitter and a receiver are arranged on the upstream side and the downstream side of the measurement fluid, respectively, and drive pulses are applied to the ultrasonic wave transmitting elements of the respective transmitters to generate and transmit ultrasonic waves mutually. The propagation time from the transmission time to the reception time of the ultrasonic wave is obtained as the measurement time τ by setting the time to perform as the start time A and the time at which the transmitted ultrasonic waves are mutually received as the end time C, When measuring the flow velocity of the fluid based on the difference of each propagation time, since the propagation time of the ultrasonic wave can be obtained with high accuracy, the flow velocity of the fluid can be accurately measured based on the difference of each propagation time, As a result, highly accurate flow measurement can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an ultrasonic flow velocity measuring device for carrying out the present invention.

FIG. 2 is a diagram showing a relative relationship between a triangular wave output from the triangular wave generation circuit of FIG. 1 and a clock wave output from a clock circuit or a clock inversion circuit.

FIG. 3 is a diagram showing a state in which a rising edge of a clock wave immediately after outputting a triangular wave has reached a safe time DF of the triangular wave.

FIG. 4A is a diagram illustrating a state in which the rising edge of the clock wave immediately after the output of the triangular wave has reached the triangular wave prohibition time CD. (B) A diagram showing a state in which the clock wave is inverted so that the rising of the clock wave immediately after the output of the triangular wave arrives at the safe time DF of the triangular wave.

FIG. 5A is a diagram showing a state in which the rising edge of the clock wave immediately after the output of the triangular wave has reached the triangular wave inhibition time FH. (B) A diagram showing a state in which the clock wave is inverted and the rising edge of the clock wave immediately after the output of the triangle wave arrives at the safe time FH of the triangle wave.

FIG. 6 is a diagram obtained by performing coordinate transformation on a triangular wave.

FIG. 7 is a block diagram showing an example of an ultrasonic flow velocity measuring device for performing a conventional ultrasonic flow velocity measuring method.

FIG. 8 is a diagram showing timing for measuring a potential difference when a conventional ultrasonic flow velocity measuring method is performed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Pipeline 2, 3 ... Transceiver 15 ... AND circuit 20, 21 ... Circuit changeover switch

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akio Kono 2-10-16 Higashi-Kobashi, Higashi-Nari-ku, Osaka Kansai Gas Meter Co., Ltd. Kansai Gas Meter Co., Ltd. (72) Inventor Tetsuya Yasuda Kansai Gas Meter Co., Ltd. 2-10-16 Higashikobashi, Higashinari-ku, Osaka-shi

Claims (2)

[Claims] 1. A clock wave (W) is output in synchronization with a start time A of a measurement time τ, and measurement is performed by counting the number of clock waves (W) output until an end time C of the measurement time τ. In the time measuring method for obtaining the time τ, a triangular wave (P) is output in synchronization with the end time C of the measuring time τ, and the potential difference measuring timing E determined by the rising or falling of the clock wave (Wa) immediately after the triangular wave (P). Arrives within the predetermined time (CD) (FH), a clock wave (W) is output again in synchronization with the start time A of the measurement time τ, and the clock wave (W) is inverted by a half cycle and inverted. A triangular wave (P) is output in synchronization with the end time C of the measurement time τ, and the triangular wave (P) is output immediately after the potential difference measurement timing E ′ determined by the rise or fall of the clock wave (Wa ′). ) Measuring the difference V, and adding or subtracting a time T0 / 2 corresponding to a half cycle of the clock wave (W) to a value Y obtained by substituting the potential difference V into a proportional linear equation representing the oblique side of the triangular wave (P). The fractional time t from the rising or falling time B of the final clock wave (Wf) before the end time C of the measurement time τ to the end time C is obtained, and the wave number of the output clock (W) is counted. T from the start time A of the measurement time τ to the rising or falling time B of the final clock wave (Wf)
A time measuring method characterized in that a measuring time τ is obtained by adding the fractional time t and the fractional time t. 2. An ultrasonic flow velocity measuring method using the time measuring method according to claim 1, wherein a transmitter and a receiver are arranged on an upstream side and a downstream side of a measurement fluid, respectively. The time at which a drive pulse is applied to the ultrasonic transmitting element of the wave device to generate and transmit ultrasonic waves to each other is defined as the start time A, and the time at which the transmitted ultrasonic waves are mutually received is defined as the end time C. An ultrasonic flow velocity measuring method in which a propagation time from a transmission time to a reception time of an ultrasonic wave is obtained as a measurement time τ, and a flow velocity of a fluid is measured based on a difference between the propagation times.