JP4424959B2 - Ultrasonic flow meter - Google Patents

Description

  The present invention relates to an improvement in an ultrasonic flow meter, particularly an ultrasonic flow meter operated by a battery power source.

  The ultrasonic flowmeter calculates the flow velocity from the ultrasonic propagation time in the same forward direction as the fluid flow and the ultrasonic propagation time in the opposite direction to the fluid flow, and multiplies this flow velocity by the cross-sectional area of the flow path. To obtain the flow rate (also called instantaneous flow rate).

In FIG. 1, the transducers 2 and 3 are arranged at a distance L on the upstream side and the downstream side in the flow tube 1, and ultrasonic waves are transmitted from the transducer 2 in the direction along the fluid flow (forward direction). Transmit the ultrasonic wave in the direction opposite to the flow of the fluid from the forward-side arrival time t ₁ until the ultrasonic wave reaches the receiving-side transducer 3, and the downstream-side transducer 3, this ultrasound is reverse arrival time t ₂ Metropolitan to reach the transducer 2 on the receiving side to determine the flow rate, flow rate, a so-called time difference method is known (e.g., see Patent Document 1).

Assuming that the speed of sound in the static fluid is C and the flow velocity of the fluid is V, the forward propagation velocity of the ultrasonic wave is (C + V) and the backward propagation velocity is (C−V). At the time of measuring the forward direction and the reverse direction, the arrival times t ₁ in the forward direction and the reverse direction, respectively, until the ultrasonic waves reach the transmitting and receiving transducers 3 and 2 from the transmitting and receiving transducers 2 and 3, respectively. t ₂ is,
t ₁ = L / (C + V) (1)
t ₂ = L / (C−V) (2)
It becomes. Generally, the flow velocity V is smaller than the sound velocity C, and C ² ≧ V ² .
t ₂ −t ₁ = 2LV / C ² (3)
Get. Therefore, each arrival time (also referred to as propagation time) in the forward direction and the reverse direction is directly measured, and a time difference Δt = t ₂ −t ₁ as a difference between the arrival times is calculated.
V = Δt · C ² / 2L (4)
And the flow rate (also referred to as the instantaneous flow rate) is calculated by multiplying the flow velocity V by the channel cross-sectional area S. Such a flow velocity / flow rate measuring method is called a time difference method.

After measuring the arrival times (propagation times) t ₁ and t ₂ in the forward direction and the reverse direction, a time reciprocal difference method different from the above time difference method was also used to calculate the flow velocity and flow rate (for example, patents) Reference 1). this is,
1 / t ₁ = (C + V) / L (5)
1 / t ₂ = (C−V) / L (6)
Paying attention to the relationship, the flow velocity V is
_{V = {(1 / t 1} ) - (1 / t 2)} L / 2 ··· (7)
And the flow rate Q
Q = S · V (8)
Is what you want. In this time reciprocal difference method, equation (7) for obtaining the flow velocity V does not include the C term, and the flow velocity can be measured regardless of the sound velocity.

Incidentally, even if the time difference method is used or the time reciprocal difference method is employed, t ₁ and t ₂ are very small, so that measurement error becomes a problem. Therefore, when an ultrasonic wave is transmitted from the transmitter / receiver 2 on the transmission side and a reception wave detector (not shown) receiving the signal of the transmitter / receiver on the reception side detects the received wave, it is transmitted again at the same time. The ultrasonic wave is transmitted from the transmitter / receiver 2 on the side, and the transmission of the ultrasonic wave in the forward direction is continuously repeated a certain number of times (n times) in this way, so that a certain number of times (n the total arrival time T ₁ of the up reception times) th measured, then the ultrasonic transmitting a certain number of reverse direction (n times) repeated continuously, a predetermined number of times (n times from the first transmission) When measuring the total arrival time T ₂ of the up eyes received originally forward arrival time t ₁ and reverse arrival time t ₂ is very small, between the continuous and repetitive transmission and reception of a certain number of times almost unchanged little flow velocity V Because it can be considered constant,
T ₁ = nt ₁ (9)
T ₂ = nt ₂ (10)
It can be expressed. Therefore, the total arrival time T ₁ of the forward, the backward of the total arrival time T ₂ Prefecture, the forward arrival time t ₁ and reverse arrival time t _2,
t ₁ = T ₁ / n (11)
t ₂ = T ₂ / n (12)
Substituting t ₁ and t ₂ obtained by the equations (11) and (12) into the equation (3), calculating the flow velocity V by the equation (4), and further multiplying by the cross-sectional area S of the flow path. When the flow rate Q is obtained, the flow velocity V and the flow rate Q can be obtained based on T ₁ and T ₂ with high measurement accuracy, so that the measurement accuracy as a flow meter is improved. For example, if the fixed number of times is an integer n, the measurement accuracy is improved approximately n times.

From the total arrival times T ₁ and T ₂ ,
n / T ₁ = 1 / t ₁ (13)
n / T ₂ = 1 / t ₂ (14)
And substituting them into the equation (7) improves the measurement accuracy by the time reciprocal difference method and can measure the flow velocity V and the flow rate Q with high accuracy. At this time, the flow velocity V is
V = {(1 / T ₁ ) − (1 / T ₂ )} nL / 2 (15)
It becomes. The flow rate Q is obtained by multiplying the flow velocity V by the flow path cross-sectional area S.

In an ultrasonic flowmeter used as a gas meter for measuring the amount of city gas used, a battery-driven one that is operated by a battery power source is required. Therefore, a practically satisfactory battery life cannot be obtained unless current consumption is reduced. Therefore, the arrival times t ₁ and t ₂ or the total arrival times T ₁ and T ₂ are measured at a fixed sampling interval, and based on the measured arrival times t ₁ and t ₂ or the total arrival times T ₁ and T _2. It is obtained by calculating the flow velocity V or the flow rate Q. Then, the amount of gas used is calculated by integrating the flow rate Q. If the sampling interval is increased (long time), the average current consumption is reduced and the battery life can be extended.

In addition, the gas meter constantly monitors the gas flow rate and automatically stops the gas supply when an abnormal flow rate is detected, and it incorporates a security function (safety function) to prevent accidents in advance. The flow rate must be measured in order to be able to quickly determine whether the flow rate is abnormal. In the gas meter, gas pressure pulsation may occur due to the influence of other gas equipment connected to the gas supply pipe, and the gas flow rate may pulsate. The frequency of this pulsation is 3 Hz to 60 Hz.
Japanese Patent Laid-Open No. 10-90029 (pages 2 and 3, FIG. 5)

In the conventional technique, even when the sampling interval is reduced and many measurements are performed in order to average the pulsation, the flow velocity and flow rate are calculated each time the arrival times t ₁ and t ₂ in the forward direction and the reverse direction are measured once. . Even in the case where the transmission / reception is repeated n times continuously, the flow velocity / flow rate are calculated each time the total arrival times T ₁ and T ₂ are measured once. Since these calculations are performed by a microcomputer built in the meter (flow meter), a large amount of current is consumed for each calculation, resulting in adversely affecting battery life, increasing battery capacity, and reducing the size and cost of the gas meter. There was a first problem that it was a factor to raise.

  In addition, when the sampling timing is synchronized with the pulsation of gas, a large deviation occurs in the measured value, the measurement error of the flow rate Q becomes large, and the second problem is that the determination of the security function of the gas meter becomes a large error. there were.

  Accordingly, an object of the present invention is to provide an ultrasonic flowmeter suitable for a gas meter that can solve these problems.

In order to achieve the first object, those of Reference Example 1, the measurement of the ultrasonic wave arrival time, a flow meter that performs the forward and reverse direction,
The measurement of the arrival time of the forward and backward ultrasonic waves is repeated a plurality of times at a fixed sampling interval, and the sum of the arrival times of the forward ultrasonic waves thus measured and the ultrasonic waves in the reverse direction is repeated. It is an ultrasonic flowmeter that calculates a flow rate based on the sum total of a plurality of arrival times.

The arrival times of the ultrasonic waves at each time when transmission / reception in the forward direction and the reverse direction are repeated a plurality of times (m times) alternately are sequentially t ₁₁ , t ₂₁ , t ₁₂ , t ₂₂ ,..., T ₁ i, t2i. ,..., T ₁ m, t ₂ m, the total arrival time Σt ₁ i in the forward direction is
Σt ₁ i = t ₁₁ + t ₁₂ + ... + t ₁ i + ... + t ₁ m
And the total arrival time Σt ₂ i in the reverse direction is
Σt ₂ i = t ₂₁ + t ₂₂ + ... + t ₂ i + ... + t ₂ m
Therefore, the flow rate is calculated using the sum Σt ₁ i and Σt ₂ i. In this way, each time to measure once forward and reverse arrival time, for example as compared with the conventional method for calculating the flow velocity V by using the immediately t ₁₁ and t ₂₁ After measuring t ₁₁ and t _21, The number of flow calculations is reduced to 1 / m. Therefore, less current consumption is required for calculation.

Those of Reference Example 2, in the ultrasonic flowmeter of Example 1, the fixed line measurement of the forward direction of the ultrasonic transit time and the reverse direction of the ultrasonic arrival time at half the spacing of the sampling interval is Umo's.

Those of Reference Example 3, also in order to achieve the first object, ultrasonic waves are transmitted first from the transmission side of the transducer, receiving wave detection unit received wave which receives a signal of the reception-side transducer At the same time, transmitting the ultrasonic wave from the transmitter / receiver again is repeated a certain number of times, and the total arrival time from the first transmission to the certain number of receptions is measured. A flowmeter that determines the total arrival time to be measured in the forward and reverse directions,
The measurement of the total arrival time of the ultrasonic waves in the forward direction and the reverse direction is repeated a certain number of times at a fixed sampling interval, and the sum of the total arrival times of the ultrasonic waves in the forward direction measured in this way and the super based on the sum of a constant multiple of the total arrival time of the acoustic wave is an ultrasonic flowmeter you calculating the flow rate.

In this case , the total arrival times (T ₁ i, T ₂ i) in the forward direction and the reverse direction are alternately measured, and the sum total ΣT ₁ i and ΣT ₂ i is finished after the plural times (m times) are finished. And the flow rate is calculated based on this sum.
ΣT ₁ i = T ₁₁ + T ₁₂ + ... + T ₁ i + ... + T ₁ m
ΣT ₂ i = T ₂₁ + T ₂₂ + ... + T ₂ i + ... + T ₂ m
It is. T _{11 to} T ₁ m are the total arrival times in the forward direction, and T _{21 to} T ₂ m are the total arrival times in the reverse direction. In this case as well, the number of times of flow rate calculation is reduced to 1 / m as compared with the prior art. , Current consumption can be reduced.

Those of Reference Example 4, the ultrasonic flowmeter of Example 3, of the total arrival time of the forward ultrasound at half the interval of a constant sampling interval in the opposite direction of the total arrival time of the ultrasonic measuring the is the Umo line.

In order to achieve the first and second objects, the invention of claim 1 is a flowmeter that measures the arrival time of ultrasonic waves in the forward direction and the reverse direction. The arrival time measurement is repeated a certain number of times at a certain sampling interval, and the total sum of the forward ultrasonic arrival times measured in this way at a certain number of times and the total sum of the arrival times of the ultrasonic waves in the reverse direction at a certain number of times. In the ultrasonic flowmeter that calculates the flow rate based on
During one flow measurement period (T _Q), perform measurements between arrival time of multiple (m times), a flow meter for performing the measurement interval with such a flow measurement,
The forward maximum between at each arrival _[t 1 i] ma x, forward minimum _[t 1 i] mi n, the maximum reverse value _[t 2 i] ma x, Oh Rui reverse minimum [t _{2 i]} to monitor the changes in each flow measurement period of any one of the values of mi n, when the change is more than a certain is the ultrasonic flow meter that is configured to change the sampling interval (Ts) .

  The frequency of pulsation is usually several Hz or more, and the same pulsation continues continuously. Therefore, if the true gas flow rate not including the pulsation is constant, the maximum value and the minimum value of the gas flow rate including the pulsation are substantially constant in time. Therefore, if any of the m arrival time measurements captures the maximum or minimum, they become the maximum value and the minimum value, and are almost constant each time. However, when the sampling is in synchronization or close to synchronization, the maximum and minimum values are not captured as shown in FIG. 2, and the maximum value and the minimum value are different values depending on which position is synchronized each time. Therefore, the sampling interval (period) is changed so as not to synchronize by detecting that the sampling is synchronized by monitoring the change in either the maximum value or the minimum value in the forward direction or the reverse direction.

  In FIG. 2, the solid line indicates pulsation when the gas flow rate includes pulsation, the pulsation frequency is 36 Hz, and the sampling interval is 28 mS. In the figure, white circles indicate the measurement times of the total arrival time in the forward direction, and squares indicate the measurement points of the total arrival time in the reverse direction. From the relationship between the sampling interval (cycle) and the pulsation cycle, it can be seen that the measurement point corresponds to which part of the pulsation gradually changes. FIG. 2 shows a substantially synchronized state. In this measurement, the maximum value of accidental measurement is a true maximum value, but the minimum value Qmin obtained by this measurement does not capture the minimum value.

The invention of claim 2 is a flowmeter that measures the arrival time of the ultrasonic wave in the forward direction and the reverse direction, and repeats the measurement of the arrival time of the ultrasonic wave in the forward direction and the reverse direction a plurality of times at a constant sampling interval. In the ultrasonic flowmeter that calculates the flow rate based on the total sum of the arrival times of the ultrasonic waves in the forward direction measured in this way and the sum of the arrival times of the ultrasonic waves in the reverse direction in a plurality of times,
A flowmeter that measures a plurality of (m times) arrival times (t ₁ i, t ₂ i ) during one flow rate measurement period (T _Q ) and performs such a flow rate measurement at a certain measurement interval. Because
Forward or backward between the time arrival of each flow measurement period (T _Q), to allow the output of the maximum value and the minimum value, the maximum or minimum value for each flow measurement from the previous flow measurement The ultrasonic flowmeter is configured so that the sampling interval (Ts) is changed when the change of the sampling rate is larger than a certain constant of (maximum value−minimum value) this time.

  If the arrival time measurement or total arrival time measurement is not synchronized with the pulsation and the true maximum and minimum values can be detected, the change in the maximum or minimum value is different from the difference between the maximum and minimum values. It can be said that it is small. Therefore, whether the current (maximum value-minimum value) and the absolute value of (previous maximum value-current maximum value) or the absolute value of (previous minimum value-current minimum value) are compared to ensure synchronization. Is possible.

The invention of claim 3 is a flowmeter that measures the arrival time of the ultrasonic wave in the forward direction and the reverse direction, and repeats the measurement of the arrival time of the ultrasonic wave in the forward direction and the reverse direction a plurality of times at a constant sampling interval. In the ultrasonic flowmeter that calculates the flow rate based on the total sum of the arrival times of the ultrasonic waves in the forward direction measured in this way and the sum of the arrival times of the ultrasonic waves in the reverse direction in a plurality of times,
During one flow measurement period (T _Q ), a plurality of (m) arrival times (t ₁ i, t ₂ i ) are measured, and such flow measurement is performed at a certain measurement interval (that is, there is a certain one). A flow meter for every measurement period (T _Q ),
In each flow measurement period (T _Q), as well as counting the increase and decrease times between when the arrival of the forward or reverse direction, when increasing or decreasing the number of times counted is constant below to change the sampling interval (Ts) Is an ultrasonic flowmeter characterized by

  When the pulsation cycle is long, if the sampling interval (Ts) is too small, only a part of the pulsation can be measured, and a true flow rate cannot be obtained by one measurement. It is effective to calculate the flow rate by measuring a time that is an integral multiple of the pulsation period, but this is difficult because the pulsation period is unknown.

In the end, it is desirable to set the flow rate measurement period (T _Q ) corresponding to several pulsation cycles (3 cycles or more).

  If the sampling period is sufficiently smaller than the pulsation period, the arrival time and the total number of increase / decrease times will indicate how many pulsation periods the arrival time measurement has, and if the value is small, the averaging is performed efficiently. I understand that it is not. In that case, it is possible to measure for several cycles of pulsation by increasing the sampling interval.

Further, when the sampling is synchronized, the increase / decrease number may not correctly reflect the number of periods. However, when the invention of claim 6 is used together, it is more effective because it does not synchronize.
Further, by preventing synchronization between sampling and pulsation, it is possible to efficiently average the flow rate of pulsation without reducing the sampling interval so much. FIG. 10 shows an example in which the sampling period is not synchronized with the pulsation in the case where the sampling period is larger than the pulsation period. Sampling varies in various phases of pulsation, and averaging can be performed efficiently. (± 1m ^{3 at} zero true flow rate
When there is / h pulsation. The number of increase / decrease counts both increase and decrease. The average is averaged to a value close to zero (true value). )
FIG. 3 shows a case where measurement is performed only for about 1.3 cycles of pulsation. One period is canceled well, but the remaining 0.3 period is an error.

According to a fourth aspect of the present invention, there is provided the ultrasonic flowmeter according to the second aspect, wherein one flow rate measurement period (T _Q ) During multiple times (m times) ₁ i, t ₂ a flowmeter which performs the measurement of i) and performs such a flow rate measurement at a certain measurement interval,
  Each flow measurement period (T _Q ), The number of increase / decrease times of each arrival time in the forward direction or the reverse direction is counted, and the sampling interval (Ts) is changed when the counted increase / decrease number is not more than a certain value. It is.

The invention according to claim 5 is the ultrasonic flowmeter according to claim 3 or 4 , wherein the measurement value of the arrival time (t ₁ i, t ₂ i ) in the forward direction or the reverse direction in one flow measurement period (T _Q ). each time but obtained at each sampling, increased or decreased by as well as to obtain the maximum and minimum values and their intermediate values of the measured values, and counts the number of times the while upon reaching acquired across the intermediate value It is characterized by detecting the number of times.

Since the pulsation is not necessarily clean sine wave (pulsation of the main large period shorter when small pulsation cycle as is superimposed), or is at increased or decreased between the time simply reached was measured over several periods of the pulsation Things that don't understand happen.
In the present invention, since the number of times of crossing the intermediate value between the maximum value and the minimum value is set as the increase / decrease number, it is possible to know how many cycles were measured for the main large pulsation without being confused by the superimposed small pulsation. is there.

According to the sixth aspect of the present invention, first, an ultrasonic wave is transmitted from the transmitter / receiver on the transmission side, and the reception wave detector that receives the signal of the receiver / transmitter / receiver detects the received wave, and at the same time, the transmitter / receiver on the transmission side again. Transmitting ultrasonic waves continuously from a certain number of times, measuring the total arrival time from the first transmission to the reception of a certain number of times, and the total arrival time measured in this way in the forward and reverse directions With a flowmeter that
The measurement of the total arrival time of the ultrasonic waves in the forward direction and the reverse direction is repeated a certain number of times at a fixed sampling interval, and the sum of the total arrival times of the ultrasonic waves in the forward direction measured in this way and the super In the ultrasonic flowmeter that calculates the flow rate based on the sum total of a certain number of times the total arrival time of sound waves,
A flowmeter that measures the total arrival time multiple times (m times) during one flow rate measurement period (T _Q ), and performs such flow rate measurement at a certain measurement interval,
Forward maximum value [T ₁ i] max, forward minimum value [T ₁ i] min, reverse maximum value [T ₂ i] max, or reverse minimum value [T ₂ i for each arrival time or total arrival time ] An ultrasonic flowmeter configured to monitor a change of any one value of min in the flow rate measurement period and change the sampling interval (Ts) when the change is equal to or greater than a certain value. It is.
According to the seventh aspect of the present invention, first, an ultrasonic wave is transmitted from a transmitter / receiver on the transmission side, and a reception wave detector that receives a signal from the receiver / transmitter / receiver detects a received wave, and at the same time, the transmitter / receiver on the transmission side again. Transmitting ultrasonic waves continuously from a certain number of times, measuring the total arrival time from the first transmission to the reception of a certain number of times, and the total arrival time measured in this way in the forward and reverse directions With a flowmeter that
The measurement of the total arrival time of the ultrasonic waves in the forward direction and the reverse direction is repeated a certain number of times at a fixed sampling interval, and the sum of the total arrival times of the ultrasonic waves in the forward direction measured in this way and the super In the ultrasonic flowmeter that calculates the flow rate based on the sum total of a certain number of times the total arrival time of sound waves,
During one flow rate measurement period (T _Q ), a plurality of (m times) total arrival times (T ₁ i, T ₂ i) are measured, and such a flow rate is measured at a certain measurement interval. A total of
The maximum and minimum values in the forward or reverse direction of the total arrival time for each flow rate measurement period (T _Q ) can be output, and the maximum or minimum value for each flow rate measurement from the previous flow rate measurement The ultrasonic flowmeter is configured so that the sampling interval (Ts) is changed when the change of the sampling rate is larger than a certain constant of (maximum value−minimum value) this time.
In the invention of claim 8, first, an ultrasonic wave is transmitted from a transmitter / receiver on the transmission side, and a reception wave detector that receives a signal of the receiver / transmitter / receiver detects a received wave at the same time. Transmitting ultrasonic waves continuously from a certain number of times, measuring the total arrival time from the first transmission to the reception of a certain number of times, and the total arrival time measured in this way in the forward and reverse directions With a flowmeter that
The measurement of the total arrival time of the ultrasonic waves in the forward direction and the reverse direction is repeated a certain number of times at a fixed sampling interval, and the sum of the total arrival times of the ultrasonic waves in the forward direction measured in this way and the super In the ultrasonic flowmeter that calculates the flow rate based on the sum total of a certain number of times the total arrival time of sound waves,
During one flow rate measurement period (T _Q ), a plurality of (m times) total arrival times (T ₁ i, T ₂ i) are measured, and such a flow rate is measured at a certain measurement interval. A total of
Within each flow rate measurement period (T _Q ), count the number of increases / decreases in the total arrival time in the forward direction or the reverse direction, and change the sampling interval (Ts) when the counted number of increases / decreases is less than a certain value. Is an ultrasonic flowmeter characterized by
The invention according to claim 9 measures the total arrival time (T ₁ i, T ₂ i) a plurality of times (m times) during one flow rate measurement period (T _Q ), and measures such a flow rate. A flowmeter that performs at a measurement interval,
Within each flow rate measurement period (T _Q ), count the number of increases / decreases in the total arrival time in the forward direction or the reverse direction, and change the sampling interval (Ts) when the counted number of increases / decreases is less than a certain value. The ultrasonic flowmeter according to claim 7.
In the invention of claim 10, every time a measurement value of the total arrival time (T ₁ i, T ₂ i) in the forward direction or the reverse direction in one flow rate measurement period (T _Q ) is obtained for each sampling, The maximum and minimum values of measurement values and their intermediate values can be obtained, and the number of times of increase / decrease is detected by counting the number of times the acquired total arrival time crosses the intermediate value. The ultrasonic flowmeter according to 8 or 9 .
The invention according to claim 11 is characterized in that the arrival time of the ultrasonic wave in the forward direction and the arrival time of the ultrasonic wave in the reverse direction are measured at an interval of 1/2 of the fixed sampling interval. The ultrasonic flowmeter according to any one of the above.
According to a twelfth aspect of the present invention, the total arrival time of the ultrasonic waves in the forward direction and the total arrival time of the ultrasonic waves in the reverse direction are measured at an interval ½ of the fixed sampling interval. It is an ultrasonic flowmeter in any one of thru | or 10.

Those of Reference Example 5, in order to achieve the first and second objects,
A flowmeter that measures the arrival time of ultrasonic waves in the forward and reverse directions,
Normal mode for measuring the arrival time of the ultrasonic waves in the forward direction and the reverse direction at a predetermined sampling interval, and calculating the flow rate based on the arrival time,
The measurement of the arrival times of the ultrasonic waves in the forward direction and the reverse direction is repeated a plurality of times (m times) at a sampling interval different from the predetermined sampling interval, and the arrival times of the ultrasonic waves in the forward direction thus measured are constant times (m And a pulsation mode for calculating the flow rate based on the sum of the arrival times of the ultrasonic waves in the reverse direction at a fixed number of times (m times),
In the normal mode, when a change in flow velocity above a certain level is recognized, the mode shifts from the normal mode to the pulsation mode,
In the pulsation mode, the ultrasonic flowmeter is returned to the normal mode from the pulsation mode when the difference between the maximum value and the minimum value of each arrival time is not more than a certain value.

In the normal mode, the arrival times in the forward direction and the backward direction are measured at predetermined sampling intervals, and the flow rate is calculated based on these arrival times or the sum thereof. When there is a change in the flow rate above a certain level, the mode changes to the pulsation mode.
In the pulsation mode, the total sum of arrival times of a plurality of times (m times) is measured at a sampling interval different from the predetermined sampling interval. The total forward arrival time is, for example,
Σt ₁ i = t ₁₁ + t ₁₂ + ... + t ₁ i + ... + t ₁ m
The sum of the arrival times in the reverse direction is, for example,
Σt ₂ i = t ₂₁ + t ₂₂ + ... + t ₂ i + ... + t ₂ m
It is.

Based on the total Σt ₁ i and Σt ₂ i, the flow rate during pulsation is calculated. Since the flow rate calculation is only performed every time the arrival time is measured a plurality of times (m times), the current consumption required for the calculation is reduced.
Further, in the normal mode, since it is used in a steady flow with no flow pulsation, even if the predetermined sampling interval is set long (large), the flow measurement error does not increase, and the current consumption can be reduced.

Those of Reference Example 6, the ultrasonic flowmeter of Example 5, the pulsating mode, first from the transmission side of the transducer transmits ultrasound, receiving wave detection section that receives the signal of the reception-side transducer At the same time that it detects the received wave, it repeats transmitting the ultrasonic wave from the transmitter on the transmitting side again a fixed number of times (n times), and the total from the first transmission to the reception of the fixed number of times (n times) with measuring the arrival time is the total arrival time measured in this way to be to use as the arrival time.

By doing this, the total total arrival time ΣT ₁ i in the forward direction is
ΣT ₁ i = T ₁₁ + T ₁₂ + ... + T ₁ i + ... + T ₁ m
The total sum of arrival times in the reverse direction ΣT ₂ i is
ΣT ₂ i = T ₂₁ + T ₂₂ + ... + T ₂ i + ... + T ₂ m
It becomes.

Those of Reference Example 7, the ultrasonic flowmeter of Example 5 or 6, comprising a plurality of pulsation modes, each pulsating mode is to Umo line measurement of ultrasonic wave arrival time at different sampling intervals.

In this case , the measurement error can be reduced by switching the sampling interval in the pulsation mode corresponding to the pulsation state, for example, the pulsation frequency.

Those of Reference Example 8, the ultrasonic flowmeter of Example 5, 6 or 7, than the sampling interval of the normal mode, is the ash defined short sampling interval of the pulsating mode.

  In this invention, by shortening (decreasing) the sampling interval in the pulsation mode, accurate measurement can be performed following pulsation, that is, flow rate fluctuation.

Those of reference example 9, either in the ultrasonic flowmeter of Example 5-8, the pulsation mode in the measurement of the normal mode, when the difference between the measured value and the present measured values of the last time above a certain it is also of to migrate to.

  In the present invention, the measurement mode can be easily switched from the normal mode to the pulsation mode based on the difference between the previous measurement value of the arrival time measured at a predetermined sampling interval and the current measurement value.

Those of Reference Example 10, in order to achieve the first and second object, a measurement of the ultrasonic wave arrival time, a flow meter that performs the forward and reverse direction,
Normal mode for measuring the arrival time of the ultrasonic waves in the forward direction and the reverse direction at a predetermined sampling interval, and calculating the flow rate based on the arrival time,
The measurement of the arrival times of the ultrasonic waves in the forward direction and the reverse direction is repeated a fixed number of times (m times) at a first sampling interval different from the predetermined sampling interval, and the fixed arrival times of the ultrasonic waves in the forward direction thus measured are determined. A first pulsation mode for calculating a flow rate based on the sum total at the number of times (m times) and the sum of the arrival times of the ultrasonic waves in the reverse direction at a fixed number of times (m times);
The measurement of the arrival time of the ultrasonic waves in the forward direction and the reverse direction is repeated a predetermined number of times (m times) at a second sampling interval different from the predetermined sampling interval and the first sampling interval, and thus the forward super A second pulsation mode for calculating a flow rate based on a sum of the arrival times of the sound waves at a plurality of times (m times) and a sum of the arrival times of the ultrasonic waves in the reverse direction at a plurality of times (m times); Comprising
In the normal mode, when a change in flow velocity of a certain level or more is recognized, the normal mode shifts to the first pulsation mode,
In each pulse mode, an ultrasonic flowmeter that determines the switching or continued modes based on the difference and increase or decrease the number of the arrival time of the maximum and minimum values of each arrival time.

This shall, in each pulse mode, the difference between the maximum value and the minimum value of each arrival time, and so determine the switching or continued modes based on the increase or decrease the number of the arrival time, according to the state of pulsation, and more detailed response Can improve the measurement accuracy.
The maximum value and the minimum value of each arrival time can be obtained in the same manner as in the first or second aspect , and the increase / decrease number of each arrival time is obtained in the same manner as in the third aspect. be able to.

Those of Reference Example 11, the ultrasonic flowmeter of Example 10, the first and second of each pulse mode, ultrasonic waves are transmitted first from the transmission side of the transducer, a signal of the reception-side transducer The reception wave detection unit as an input detects the reception wave and simultaneously transmits the ultrasonic wave again from the transmitter on the transmission side a predetermined number of times (n times). ) eye with measuring the total time to reach the reception of is the total arrival time measured in this way to be to use as the arrival time.

In this case , at the time of pulsation, the sum of arrival times of n × m transmission / reception times can be directly measured in the forward direction and the reverse direction, and the flow rate can be calculated based on the sum, so that the measurement accuracy is further improved.

Those of Reference Example 12, the ultrasonic flowmeter of Example 10 or 11, in the measurement of the normal mode, the difference between the measured value and the present measured values of the last time to migrate to the pulsation mode when more than a predetermined It is.

  In the present invention, in the normal mode, when the difference between the previous measurement value and the current measurement value is greater than or equal to a certain value, it is determined that the flow rate fluctuation is greater than or equal to a certain value, and the first pulsation mode is switched to perform sampling corresponding to the pulsation.

The present invention than being constructed as described above, the flow amount the number of operations is reduced and 1 / m of the prior art, since that amount consumed current is reduced, it is possible to reduce the size of the battery, the battery Contributes to the practical use of driving ultrasonic flowmeters.

  In addition, the sampling time can be prevented from synchronizing with the pulsation, and the accuracy of flow rate measurement is increased. Since the sampling interval can be set to the optimum value, it is possible to sample several pulsation cycles as one flow rate measurement, and the measurement accuracy of the flow meter can be increased also from this aspect.

Furthermore, since the pulsating flow rate can be averaged without making the sampling period so small as compared with the pulsation period, the current consumption can be further suppressed.
In the inventions of Reference Examples 5 to 12 , since the number of times of flow rate calculation in the pulsation mode is reduced to 1 / m, the current consumption of the flow meter is reduced.

In addition, when the steady flow rate has no pulsation, the current consumption in the measurement mode can be lowered regardless of the pulsation by increasing the sampling interval in the normal mode. Current consumption can be reduced.
Furthermore, in the invention of this, it is possible to avoid having to synchronize the pulsation from the sampling point, can reduce the measurement error due to the synchronization, which is effective when using an ultrasonic flowmeter as gas meter.

  Next, preferred embodiments of the present invention will be described according to some examples.

  In FIG. 4 (a), the transducers 2 and 3 are transducers arranged at a distance L on the upstream side and the downstream side as described in FIG. The transmitter / receiver 2 can be operated as both the transmitting side and the receiving side. When the changeover switches S1 and S2 are in the illustrated state, the transmitter / receiver 2 is connected to the transmitter driver 4 and operates as the transmitting side. 3 is connected to the received wave detector 5 and operates as a receiving side.

  Upon receiving the first transmission command signal from the measurement controller 6, the transmitter driver 4 first drives the transmitter / receiver (in this case, 2), and thereafter receives the transmitter / receiver (in this case, 3). Each time the reception wave detection signal is received from the reception wave detection unit 5 connected to the transmitter, the transmitter / receiver (2) on the transmission side is driven. However, when the nth received wave detection signal is received from the first counter 7, the driving is stopped until a new first transmission command signal is received thereafter.

  In the second embodiment, the meaningless (n + 1) th driving is performed, but there is no problem because it is ignored on the receiving side.

  The first counter 7 counts the received wave detection signal from the received wave detector 5 and outputs the nth received wave detection signal as the nth received wave detection signal. The first counter 7 is reset by a first transmission command signal from the measurement control unit 6.

As shown in FIG. 6, after the measurement start signal is input and reset, the second counter 8 starts counting with the first transmission command signal at the time of forward measurement by the transmission direction signal, and with the nth received wave detection signal. repeatedly counting stop, total arrival time _{(T 11, T 12, ...} , T 1 i, T 1 m) for counting measure the sum of. Similarly, the total sum of arrival times (T ₂₁ , T ₂₂ ,..., T ₂ i, T ₂ m) from the first transmission command signal to the n-th received wave detection signal at the time of reverse direction measurement is counted and measured. . The sum of the total arrival times of the measurement values is read after the measurement end signal of the measurement control unit 6 is input by the calculation unit 9 composed of a microcomputer separately for the forward value and the reverse value (see FIGS. 4 and 6). ).

When a measurement start signal is input from the calculation unit 9 composed of a microcomputer, the measurement control unit 6 outputs the first transmission command signal while keeping the transmission direction signal in the forward direction, and after a certain time, inverts the transmission direction signal and reverses it. The direction and the output of the first transmission command signal again are configured to be repeated a plurality of times (m times) set by the microcomputer of the calculation unit 9. The intervals Ts ₁ and Ts ₂ of the first transmission command signal shown in FIGS. 4B and 4C and FIG. 6 are set (set) in the measurement control unit 6 by the microcomputer constituting the calculation unit 9. These flows are not shown.

The measurement control unit 6 outputs the first transmission command signal that is set (set) by the microcomputer constituting the calculation unit 9 as described above and is measured at intervals Ts _2. The microcomputer outputs an end signal to the microcomputer. When the microcomputer receives this signal, the count value (measured value) is the sum total ΣT ₁ i of the total forward arrival times of the second counter 8 and the sum ΣT ₂ i of the total backward arrival times. Read. Calculation unit 9 is thus read-sum oT 1 _i of the forward total arrival time T _{1 i,} the sum oT 2 _i reverse total arrival time T _{2 i,} calculates the flow rate based on both the sum. Microcomputer constituting the operation unit 9 outputs the measurement start signal at longer time intervals than the sampling period T _Q, and the flow rate operation perform the above operation for each receiving a measurement end signal. The sum ΣT ₁ i and the sum ΣT ₂ i are expressed by the following equations.

ΣT ₁ i = T ₁₁ + T ₁₂ + T ₁₃ +... + T ₁ m ₋₁ + T ₁ m (16)
_{ΣT 2 i = T 21 + T} 22 + T 23 + ... + T 2 m -1 + T 2 m ·· (17)
However counter 8a and 8b are not perform calculation of the equation (16) (17), to measure directly oT ₁ i and oT ₂ i.
FIG. 5 shows the configuration of the second counter 8 of FIG. In both the forward total arrival time total counter 8a and the reverse total arrival time total counter 8b, the count value (measured value of the total total arrival time) is reset to zero with the measurement start signal, and the first transmission command signal The reference clock is counted (counted) from the clock oscillating unit 8c, and the counting is stopped by the nth received wave detection signal. The reference clock is input to only the forward total arrival time total counter 8a during forward measurement and only to the backward total arrival time total counter 8b during backward measurement by the switch S3 that is switched by the transmission direction signal. Thus, the total sums ΣT ₁ i and ΣT ₂ i of the total arrival times in the forward and reverse directions are separately measured by the counters 8a and 8b (see FIGS. 4B, 4C, and 6).

In FIGS. 4B and 4C and FIG. 6, Ts is a constant sampling interval, Ts ₁ is an interval time between the forward measurement and the subsequent reverse measurement, and Ts ₂ is a reverse measurement and the subsequent order. The interval time with the direction measurement is not necessarily set to Ts ₁ = Ts ₂ , but in Reference Example 2 and Reference Example 4, it is limited to Ts ₁ = Ts ₂ .

In the first embodiment, by repeating the ultrasonic transmission and reception of each consecutive predetermined number of times in the forward and backward direction (n times), the sum of the forward and the total arrival time of each reverse _{T 11 + T 12+ ... + T} 1 i +... + T ₁ m and T ₂₁ + T ₂₂ +... + T ₂ i +... + T ₂ m are measured, and the flow rate is calculated based on these. Since ΣT ₁ i and ΣT ₂ i correspond to the sum of arrival times in which transmission and reception were performed n × m times in the forward direction and in the reverse direction, respectively, for example, (n × m) t ₁ and (n × m) t ₂ . Using the following equation (18), the flow velocity V is obtained according to the time difference method, and the flow rate is obtained by multiplying the flow path cross-sectional area.

V = (ΣT ₂ i−ΣT ₁ i) C ² / 2L (n × m) (18)
Instead of obtaining the flow velocity V according to the time difference method using the equation (18), the flow velocity V can also be obtained according to the time reciprocal difference method as follows.
This method can be said to be an idea of first obtaining the average arrival times in forward and reverse directions and obtaining the flow velocity V using them.
That is,
t ₁ = ΣT ₁ i / n · m (19)
t ₂ = ΣT ₂ i / n · m (20)
The time reciprocal difference method is expressed by the following equation as in the equation (7).
_{V = {(1 / t 1} ) - (1 / t 2)} L / 2 ··· (7)
Substituting Equations (19) and (20) into Equation (7),
V = {(1 / ΣT ₁ i) − (1 / ΣT ₂ i)} n · m · L / 2 (21)
Thus, by using this equation (21), the flow velocity V can also be obtained according to the time reciprocal difference method using ΣT ₁ i and ΣT ₂ i corresponding to the sum of arrival times.

As in the first embodiment, transmission and reception of ultrasonic waves in the forward direction and the reverse direction are not performed continuously by a certain number of times (n times), but are performed one by one, and the direct arrival times t ₁ and t ₂ are directly transmitted. Is measured m times and Σt ₁ i, ie,
Σt ₁ i = t ₁₁ + t ₁₂ + ... + t ₁ i + ... + t ₁ m
Σt ₂ i = t ₂₁ + t ₂₂ + ... + t ₂ i + ... + t ₂ m
As it can also be adapted to calculating the velocity-flow rate based on the sum .SIGMA.t ₂ i of the sum of the forward reaching time _{t 1} i Σt ₁ i and reverse arrival time _{t 2} i (Reference Examples 1 and 2).

FIG. 7 shows a second embodiment corresponding to the first aspect of the invention. The overall configuration of the flowmeter is similar to that of FIG. 4A, and the configuration of the second counter 8 is as shown in FIG. The configuration is different from the first and fourth embodiments.

In the second embodiment, the total arrival time counter 8A and the maximum value holder 10 for holding the maximum value are added to the configuration of FIG. 5 and have the configuration of the block diagram of FIG. When the transmission direction signal is input to the maximum value holder and the measurement start signal of FIG. 6 is input, the content is reset to zero, and during the single flow rate measurement period T _Q shown in FIG. 4B or FIG. The maximum value [T ₁ i] max of the total forward arrival time T ₁ i is held and output to the calculation unit 9 in FIG.

Calculation unit 9 stores the maximum value [T 1 _i] max, as compared to the stored value of the maximum value of the forward total arrival time between the previous flow measurement period T _Q, obtains the difference, the difference, That is, when the fluctuation is larger than a certain value, the sampling interval Ts is changed on the assumption that the measurement of the sum of the total arrival times repeated a plurality of times is synchronized with the pulsation of the gas flow rate. In this way, flow rate measurement with less error is performed avoiding synchronization with pulsation.

  The frequency of pulsation is a few Hz or higher and hardly changes. Therefore, if the true flow rate excluding pulsation (the flow rate of gas used) is constant, the maximum and minimum values of the gas flow rate including pulsation do not change, and it is considered that the value is kept almost constant. However, when the sampling interval Ts of the total arrival time measurement is synchronized with the pulsation, the true maximum value and the minimum value are not captured as shown in FIG. Therefore, the change of either the maximum value or the minimum value in the forward direction or the reverse direction is monitored, and if the change is more than a certain value, the sampling timing is considered to be synchronized with the pulsation, and the sampling interval is changed and measured. The error is reduced.

Example 2 has been focused on variation of the maximum value of the flow rate per measurement period T _Q of the forward total arrival time, the presence of monitors synchronously the minimum flow rate for each measurement period T _Q of the forward total arrival time may be determined, it may be determined whether the synchronization capture the change of the maximum or minimum value of the flow rate per measurement period T _Q reverse total arrival time.

In the inventions of Reference Examples 1 and 2 in which the arrival time of one transmission / reception is measured a plurality of times (m times), not the total arrival time, and the flow rate is calculated from the sum Σt ₁ i and Σt ₂ i Similarly, it is possible to improve the measurement accuracy by avoiding synchronization with pulsation.

A third embodiment will be described with reference to FIG. 8 and FIGS. This embodiment corresponds to the invention of claim 2 in which the total arrival time is measured and the flow rate is calculated.

  The configuration of the second counter 8 is shown in FIG. The forward maximum value and the forward minimum value are output to the calculation unit 9. As in the description of FIG. 7, the minimum value holder 11 detects and stores the minimum value of the total arrival time only when the transmission direction signal indicates the forward direction, and when the measurement start signal is input, all the bits 1 (maximum that can be counted). Number). If the total arrival time is smaller than the value, the value is continuously stored, so that the minimum value of the total arrival time is stored at the end of the measurement.

When the measurement end signal is input from the measurement control unit 6, the calculation unit 9 reads the forward maximum value and the forward minimum value together with the total sum of the forward and reverse total arrival times, and calculates the previous value of the forward maximum value. When the difference is obtained and larger than (maximum forward value−minimum forward value) × 1/4, the sampling interval set in the control unit 6 is changed. The maximum value read this time is stored as the previous value for the next time.
Further, in the calculation unit 9, when (maximum forward value−minimum forward value) is smaller than a certain value, the sampling interval set in the control unit 6 is changed to change Embodiments 5 to Reference Examples 5 to 12 described later. , 6.

Next, an embodiment corresponding to the invention of claims 3 and 5 that measures the total arrival time and performs the flow rate calculation will be described with reference to FIGS.

  FIG. 9 shows the configuration of the second counter 8 in the fourth embodiment. The maximum and minimum value holders 10 and 11 hold the maximum value and the minimum value in the forward direction in the same manner as in FIG. These outputs are input to the intermediate value output unit 12, and the intermediate value output unit 12 outputs an intermediate value of two inputs. The intermediate value output unit 12 is composed of an adder.

  This intermediate value is input to the A input of the comparator 13 and the output of the total arrival time counter is input to the B input. The output of the comparator 13 is a signal that becomes “High” when the A input is greater than the B input, and the output is updated by the direction signal input as the output update signal and the nth received wave detection signal. Yes. Therefore, the output does not change in the process of counting up the total arrival time counter, and outputs the result every time the forward measurement is completed.

Therefore, the output of the comparator 13 is “High” when the arrival time is smaller than the intermediate value, and “Low” when equal or larger. The counter 14 counts the rise of this output. Accordingly, the output count value counts the number of times the arrival time is smaller than the intermediate value. In terms of increase / decrease, the number of decrease can be counted.
By changing the circuit, the increase may be counted, or both the increase and decrease may be counted.

Next, Example 5 corresponding to those of Reference Examples 5 to 9 will be described. In this embodiment, the hardware configuration of the entire flow meter uses FIG. The operation will be described with reference to the flowchart of FIG. Since the description of FIG. 4A itself has been described in detail in the above description, it will not be described again.

In FIG. 11, normal mode measurement is performed in step 101. In this normal mode, the total arrival time in the forward direction and in the reverse direction is measured a plurality of times (m times) at a predetermined sampling interval Ts. The measurement interval Ts _{1 in} the forward direction and the reverse direction is set to a smaller value than the sampling interval Ts. The measurement interval Ts ₂ reverse the next forward defines a value close to Ts. In other words,
Ts ₁ ≪Ts
Ts ₂ ≒ Ts
Ts ₁ << Ts ₂
Stipulated in

  The number of continuous transmissions and receptions is n = 100 times in each of the forward direction and the reverse direction, and the predetermined sampling interval Ts is 1 second. By doing so, the total arrival time for n = 100 times is measured at a sampling interval of 2 seconds in both the forward direction and the backward direction, and the flow rate during steady state is calculated every 2 seconds.

  Then, it is determined whether or not the difference between the previous value and the current value in the normal mode in step 101 is a certain value or more. , Transition to the pulsation mode of step 105 (switch). In step 103, it may be determined from the difference between the previous arrival time (strictly, the total arrival time) measured in the normal mode in step 101 and the current arrival time (total arrival time), or the arrival time ( Strictly speaking, it may be determined from the difference between the previous flow rate and the current flow rate calculated from the total arrival time). In short, it is determined whether or not the difference between the total arrival time or flow rate that is the previous measurement value and the arrival time or flow rate that is the current measurement value is greater than or equal to a certain value. When this is not more than a certain value, that is, when it is small, it is determined that there is a steady flow without pulsation, and the process returns to step 101.

In pulsed mode in step 105, the sampling interval Ts is 56 ms, transmission and reception number n is four consecutive sampling times performed between the period T _Q, i.e. n of said predetermined plurality of times is defined as 16 times. Accordingly, the flow rate is calculated based on the sum of the total arrival time obtained by collecting the four total arrival times and the total number of sampling times of 16 times in the forward direction and after the reverse direction.

In the fifth embodiment, Ts ₁ and Ts ₂ are determined at intervals of 1/2 of the sampling interval Ts = 56 ms in the pulsation mode, and Ts ₁ = Ts ₂ = Ts / 2. By doing this, it is possible to reliably capture the whole picture of flow fluctuations with a sampling interval of ½ or less of one cycle of pulsation, and to improve the measurement accuracy according to the so-called Shannon's theorem. Become.

  In the present embodiment, steady measurement in the normal mode or measurement in the pulsation mode is performed once every 2 seconds. When the difference in step 103 is equal to or larger than a certain value, the pulsation measurement in the pulsation mode is continued as a re-measurement. It is also possible to execute. In the case of actual pulsation, a more accurate measurement result can be obtained. It is also possible to abandon the result of detecting the flow rate change in step 103 and adopt the previous value that is the result before the change (that is, before pulsation occurs).

  In the pulsation measurement in the pulsation mode in step 105, sampling is performed 16 times at a sampling interval of 56 ms with n = 4 repeated transmissions / receptions in each of the forward direction and the reverse direction (the number of transmissions / receptions is n × m). The flow rate is calculated from the sum of the total arrival times, and the maximum and minimum values only in the forward direction among the total arrival times measured at each sampling interval are stored as the number of clocks of the reference oscillation unit ( Step 106).

  When the (maximum value) − (minimum value) is larger than a certain value, it is determined that the sampling is not synchronized with the pulsation (step 107), and the pulsation measurement is continued with the sampling period of 56 ms as it is. That is, the process returns from step 106 to step 105. When (maximum value) − (minimum value) is not greater than a certain value (small value) in step 107, it is determined that sampling is synchronized with pulsation, and the process proceeds to step 109, where a sampling interval (period) is determined. ) Change Ts to a different value of 16 ms and continue measurement during pulsation.

  In step 106, the maximum value and the minimum value for each of the m times of sampling are stored only in the forward direction, and when the difference between these values is equal to or greater than a certain value (step 107), it is not synchronized. The condition is determined to return to the pulsation mode 105. However, the maximum value and the minimum value in both the forward direction and the reverse direction are stored, and (maximum value) − (minimum value) is both in the forward direction and the reverse direction. If it is determined that the sampling is not synchronized with the pulsation when the value is larger than a certain value, the condition may be set so as to return from step 107 to step 105. In this way, the determination can be made with higher accuracy when the determination is made based on the values in the forward and reverse directions.

  Now, based on the measurement value at the time of pulsation in step 109, when (maximum value)-(minimum value) is larger than a certain value (step 111), it is judged that there is pulsation and synchronization is avoided, and the sampling interval is left as it is. Return to 105. Further, when (maximum value) − (minimum value) is less than a certain value, there is no pulsation and it is determined that the flow is a steady flow, and the normal mode of step 101 is restored.

  In the above description, the process shifts from step 103 to step 105 to change the sampling interval to 56 ms, and the process shifts from step 107 to step 109 to change the sampling interval to 16 ms. However, the sampling interval is inversely related to the above description. That is, 16 ms may be set in the transition from step 103 to step 105, and 56 ms may be set in step 109.

Flow rate when sampling interval Ts is 56 ms, pulsation frequency is 37 Hz, Ts ₁ = Ts ₂ = Ts / 2, and sampling start point is 0 point of pulsation wave to 1/10 of pulsation cycle FIG. 12 shows the relationship between the waveform (pulsation waveform) and the forward and backward measurement points (sampling points). Under this condition, the true average value of the flow rate was 0, the amplitude of pulsation was 1 m ³ / h, and the average of measured values was 0.58 m ³ / h because the sampling point was synchronized with pulsation. In FIG. 12, the horizontal axis represents time, the vertical axis represents the flow rate, the flow rate fluctuation is a sinusoidal pulsation itself, and the average value is zero. For synchronization, (maximum value) − (minimum value) is less than a certain value. This pulsation is sampled at intervals of 16 ms in FIG. By avoiding synchronization, the maximum and minimum of pulsation are captured, and (maximum value) − (minimum value) is almost the same as the width of PP of pulsation, which is a large value. Here, the sampling points vary with respect to the pulsation waveform, so that measurement is performed at various phases of the pulsation waveform, and a true average value is obtained by obtaining an average of the measurement values.

  In the above embodiment, two sampling intervals (cycles) of 56 ms and 16 ms are used. However, if the two sampling intervals (cycles) are selected so as not to be synchronized with the same pulsation cycle, there is no problem even if other sampling intervals are combined. Also, prepare three or more sampling intervals instead of two, and switch to the normal mode when the difference between the maximum and minimum values is less than a fixed value in all three sampling periods to perform steady measurement. May be.

Next, Example 6 corresponding to Reference Examples 10 to 12 will be described. As in the fifth embodiment, FIG. 4A is used for the hardware configuration. The operation will be described with reference to the flowcharts of FIGS. 14, 15, and 16 are exploded views of the entire flow. FIG. 15 is connected to a in FIG. 14, and FIG. 16 is connected to b in FIG. 14.

  In this embodiment, the measurement mode is switched according to the flow rate change or the sampling synchronization determination result, and the measurement mode has three modes, a normal mode, a first pulsation mode, and a second pulsation mode.

  The normal mode is a measurement mode when there is no pulsation (flow rate fluctuation), in which m is repeatedly measured 32 times in both the forward and reverse directions, and the flow rate is obtained from the sum of the total arrival times of both. Yes, in the first pulsation mode and the second pulsation mode, in the embodiment, n = 4 measurements are continuously performed in reverse and forward alternately at equal intervals (determined sampling intervals) 16 times in each direction, for a total of 64 times. The flow rate is obtained from the sum of the total arrival times in each direction. The sampling interval is different between the first pulsation mode and the second pulsation mode.

  Description will be made along the flow 16, 15, and 14 diagrams of FIGS. This flow is executed once every 2 seconds. It is divided into three major flows shown in FIGS. 16, 15, and 14 corresponding to the above three modes.

1) Switching from the normal mode When there is no pulsation (small fluctuation), the normal mode (step 203) is set in the flow of FIG. 16, and the measurement is performed in the normal mode.
When the difference from the previous value exceeds a certain range due to pulsation or flow rate change, it is determined that there is a flow rate change (step 205), and the measurement method is changed from the normal mode to the first pulsation mode (step 207).
Since the flow rate value at this time can be influenced by changes due to pulsation, the previous value can also be adopted. If not, the normal mode is continued with no change in flow rate (step 209).

2) Switching from the first pulsation mode In the pulsation mode, the maximum value and the minimum value in the forward direction among the total arrival times (actually, the count value of the reference clock) of n = 4 consecutive transmissions and receptions that are one sampling The number of changes is memorized. This is similar to the second and fourth embodiments.
In the first pulsation mode, the flow chart of FIG. 15 is obtained (step 211). First, when it is determined that the difference between the maximum and minimum values is smaller than a certain value (step 213), it is considered as a steady flow or synchronization by sampling, and the measurement mode is changed to the second pulsation mode (step 215).
When the difference is larger than a certain value, the number of times of increase / decrease is confirmed (step 215). When the difference is larger than a certain number, the first pulsation mode is continued assuming that the pulsation is well captured (step 217).
When the number is small, it is considered that the pulsation cycle is long and the convergence is slow, but when the measurement is performed after changing from the second pulsation mode to the first pulsation mode (YES in step 219), the first pulsation mode And continue (step 217).
When the mode is changed from the normal mode (NO in step 219), the mode is changed to the second pulsation mode.

3) Switching from the second pulsation mode In the second pulsation mode (step 221), the flow is as shown in FIG. Similarly to the first pulsation mode (step 211 in FIG. 15), the maximum value, minimum value, and increase / decrease count are stored, and when the difference between the maximum and minimum is small (NO in step 223), the first pulsation mode The difference between the maximum and the minimum measured in step (2) is confirmed (step 225). If the difference is smaller than a certain value, it is determined that the flow is steady and the mode is changed to the normal mode (step 227).
In step 225, if the difference was greater than a certain value in the first pulsation mode but the number of increase / decrease was small, the transition to the second pulsation mode (step 225) is synchronized with sampling in the second pulsation mode. Therefore, the first pulsation mode is changed (step 235).
If the difference in the second pulsation mode is large (YES in step 223), the number of increase / decrease is confirmed (step 229) as in the first pulsation mode, and if the difference is greater than the predetermined number, the second pulsation mode is continued. (Step 231).
When the number of times is small (YES in step 229), the difference is larger than a certain value in the first pulsation mode, but when the number of increase / decrease is small and the mode is shifted to the second pulsation mode (NO in step 233). The first pulsation mode is prioritized and changed to the first pulsation mode (step 235). When the difference is smaller than a predetermined value in the first pulsation mode and the mode is shifted to the second pulsation mode (YES in step 233) ) Maintains the second pulsation mode.

In this embodiment, when the total arrival time increase / decrease count is less than a certain value, the sampling is judged to be synchronized with the pulsation and the sampling interval is switched, so a state close to the sampling pulsation synchronization is also detected. Since the sampling interval can be changed, the flow rate that pulsates more effectively can be averaged, and the flow rate can be measured with higher accuracy.
Also in the case of this embodiment 6, we have determined in the same manner as the previous Example 5 to _{Ts 1 = Ts 2 = Ts /} 2, has been to enhance the measurement accuracy.
In any of the embodiments, the flow rate is integrated over time to calculate the amount of gas used and can be used as a gas meter.

Explanatory drawing of the operation principle of an ultrasonic flowmeter. The figure which shows the pulsation of flow volume, and a sampling time. The figure which shows the pulsation of flow volume, and a sampling time. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows Example 1 of this invention, (a) is a block diagram of a flowmeter, (b) is a figure which shows the measurement timing of total arrival time, (c) is expanded a part of the figure (b). Figure. FIG. 5 is a detailed block diagram of the counter 8 in FIG. 4. FIG. 3 is a timing chart of the first embodiment. The principal part block diagram of Example 2. FIG. The principal part block diagram of Example 3. FIG. The principal part block diagram of Example 4. FIG. It is explanatory drawing for demonstrating invention of Claim 5 , and is a figure which shows the pulsation of flow volume, and a sampling time. FIG. 10 is a flowchart of the fifth embodiment. The figure which shows the flow rate pulsation and sampling time of Example 5. The figure which shows the flow rate pulsation and sampling time of Example 5. FIG. 11 is a flowchart of Example 6. FIG. 11 is a flowchart of Example 6. FIG. 11 is a flowchart of Example 6.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Flow tube 2,3 Transmitter / receiver 4 Transmitter drive part 5 Received wave detection part 7 1st counter 8 2nd counter 8A Total arrival time counter 8a Forward total arrival time total counter 8b Reverse direction total arrival time total Counter 9 Calculation unit 10 Maximum value holder 11 Minimum value holder 13 Comparator 14 Counter

Claims (12)

The measurement of the ultrasonic wave arrival time, a flowmeter to perform the forward and reverse
The measurement of the arrival time of the forward and backward ultrasonic waves is repeated a plurality of times at a fixed sampling interval, and the sum of the arrival times of the forward ultrasonic waves thus measured and the ultrasonic waves in the reverse direction is repeated. in the ultrasonic flowmeter calculating the flow rate based on the sum of a constant multiple of the arrival time,
A flowmeter that measures the arrival time multiple times (m times) during one flow rate measurement period (T _Q ) and performs such flow rate measurement at a certain measurement interval,
Forward maximum value [t ₁ i] max, forward minimum value [t ₁ i] min, reverse maximum value [t ₂ i] max, or reverse minimum value [t ₂ i] min of each arrival time An ultrasonic flowmeter configured to monitor a change of any one value for each flow rate measurement period and to change a sampling interval (Ts) when the change is equal to or greater than a certain value. A flowmeter that measures the arrival time of ultrasonic waves in the forward and reverse directions.
  The measurement of the arrival time of the forward and backward ultrasonic waves is repeated a plurality of times at a fixed sampling interval, and the sum of the arrival times of the forward ultrasonic waves thus measured and the ultrasonic waves in the reverse direction is repeated. In the ultrasonic flowmeter that calculates the flow rate based on the sum of the arrival times at a certain number of times,
One flow measurement period (T _Q ) During multiple times (m times) ₁ i, t ₂ a flowmeter which performs the measurement of i) and performs such a flow rate measurement at a certain measurement interval,
  Each flow measurement period (T _Q ) The maximum and minimum values in the forward or reverse direction of each arrival time can be output, and the change in the maximum or minimum value for each flow measurement from the previous flow measurement is the current (maximum value). The ultrasonic flowmeter is configured to change the sampling interval (Ts) when it is larger than a predetermined value of (minimum value). A flowmeter that measures the arrival time of ultrasonic waves in the forward and reverse directions.
  The measurement of the arrival time of the forward and backward ultrasonic waves is repeated a plurality of times at a fixed sampling interval, and the sum of the arrival times of the forward ultrasonic waves thus measured and the ultrasonic waves in the reverse direction is repeated. In the ultrasonic flowmeter that calculates the flow rate based on the sum of the arrival times at a certain number of times,
One flow measurement period (T _Q ) During multiple times (m times) ₁ i, t ₂ a flowmeter which performs the measurement of i) and performs such a flow rate measurement at a certain measurement interval,
  Each flow measurement period (T _Q ), The number of increase / decrease times of each arrival time in the forward direction or the reverse direction is counted, and the sampling interval (Ts) is changed when the counted increase / decrease number is not more than a certain value. . One flow measurement period (T _Q ) During multiple times (m times) ₁ i, t ₂ a flowmeter which performs the measurement of i) and performs such a flow rate measurement at a certain measurement interval,
  Each flow measurement period (T _Q The number of times of increase / decrease of each arrival time in the forward direction or the reverse direction is counted in (), and the sampling interval (Ts) is changed when the counted number of increase / decrease is less than a certain value. Ultrasonic flow meter. One flow measurement period (T _Q ) Forward or reverse arrival time (t ₁ i, t ₂ Each time the measurement value of i) is obtained for each sampling, the maximum value, the minimum value, and the intermediate value of those measurement values can be obtained, and the number of times the acquired arrival time crosses the intermediate value is counted. 5. The ultrasonic flowmeter according to claim 3, wherein the number of times of increase / decrease is detected by First, send ultrasonic waves from the transmitter / receiver, and the received wave detector that receives the signal from the receiver / transmitter detects the received wave, and at the same time transmits the ultrasonic waves from the transmitter / receiver again. Is a flow meter that repeats a certain number of times continuously to measure the total arrival time from the first transmission to the reception of a certain number of times, and obtains the total arrival time measured in this way in the forward and reverse directions,
  The measurement of the total arrival time of the ultrasonic waves in the forward direction and the reverse direction is repeated a certain number of times at a fixed sampling interval, and the sum of the total arrival times of the ultrasonic waves in the forward direction measured in this way and the super In the ultrasonic flowmeter that calculates the flow rate based on the sum total of a certain number of times the total arrival time of sound waves,
  One flow measurement period (T _Q ), The total arrival time is measured a plurality of times (m times), and such a flow rate measurement is performed at a certain measurement interval,
  Forward maximum value of each total arrival time [T ₁ i] max, forward minimum [T ₁ i] min, reverse maximum value [T ₂ i] max or the minimum value in the reverse direction [T ₂ i] An ultrasonic flow rate characterized in that a change in any one value of min among flow rate measurement periods is monitored, and when the change is greater than or equal to a certain value, the sampling interval (Ts) is changed. Total. First, send ultrasonic waves from the transmitter / receiver, and the received wave detector that receives the signal from the receiver / transmitter detects the received wave, and at the same time transmits the ultrasonic waves from the transmitter / receiver again. Is a flow meter that repeats a certain number of times continuously to measure the total arrival time from the first transmission to the reception of a certain number of times, and obtains the total arrival time measured in this way in the forward and reverse directions,
  The measurement of the total arrival time of the ultrasonic waves in the forward direction and the reverse direction is repeated a certain number of times at a fixed sampling interval, and the sum of the total arrival times of the ultrasonic waves in the forward direction measured in this way and the super In the ultrasonic flowmeter that calculates the flow rate based on the sum total of a certain number of times the total arrival time of sound waves,
One flow measurement period (T _Q ) During multiple times (m times) total arrival time (T ₁ i, T ₂ a flowmeter which performs the measurement of i) and performs such a flow rate measurement at a certain measurement interval,
  Each flow measurement period (T _Q ) The maximum and minimum values in the forward or reverse direction of the total arrival time can be output, and the change in the maximum or minimum value for each flow measurement from the previous flow measurement is the current (maximum The ultrasonic flow meter is configured to change the sampling interval (Ts) when the value is larger than a predetermined value of (value−minimum value). First, send ultrasonic waves from the transmitter / receiver, and the received wave detector that receives the signal from the receiver / transmitter detects the received wave, and at the same time transmits the ultrasonic waves from the transmitter / receiver again. Is a flow meter that repeats a certain number of times continuously to measure the total arrival time from the first transmission to the reception of a certain number of times, and obtains the total arrival time measured in this way in the forward and reverse directions,
  The measurement of the total arrival time of the ultrasonic waves in the forward direction and the reverse direction is repeated a certain number of times at a fixed sampling interval, and the sum of the total arrival times of the ultrasonic waves in the forward direction measured in this way and the super In the ultrasonic flowmeter that calculates the flow rate based on the sum total of a certain number of times the total arrival time of sound waves,
One flow measurement period (T _Q ) During multiple times (m times) total arrival time (T ₁ i, T ₂ a flowmeter which performs the measurement of i) and performs such a flow rate measurement at a certain measurement interval,
  Each flow measurement period (T _Q ), The number of increase / decrease times of the total arrival time in the forward direction or the reverse direction is counted, and the sampling interval (Ts) is changed when the counted increase / decrease number is less than a certain value. Total. One flow measurement period (T _Q ) During multiple times (m times) total arrival time (T ₁ i, T ₂ a flowmeter which performs the measurement of i) and performs such a flow rate measurement at a certain measurement interval,
  Each flow measurement period (T _Q 8), the number of increase / decrease of the total arrival time in the forward direction or the reverse direction is counted, and the sampling interval (Ts) is changed when the counted increase / decrease number is less than a certain value. The described ultrasonic flowmeter. One flow measurement period (T _Q ) Total arrival time in the forward or reverse direction (T ₁ i, T ₂ Each time the measurement value of i) is obtained for each sampling, the maximum value and the minimum value of those measurement values and their intermediate values can be obtained, and the obtained arrival time or total arrival time is set to the intermediate value. The ultrasonic flowmeter according to claim 8 or 9, wherein the number of times of increase / decrease is detected by counting the number of crossings. The supersonic wave arrival time in the forward direction and the ultrasonic wave arrival time in the reverse direction are measured at an interval that is 1/2 of the fixed sampling interval. Sonic flow meter. The total arrival time of the ultrasonic waves in the forward direction and the total arrival time of the ultrasonic waves in the reverse direction are measured at an interval that is ½ of the fixed sampling interval. Ultrasonic flow meter.

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