JP2005257612A - Flow measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent increases in a value of a display means when gas is not used, and reduce integration errors when gas is used. <P>SOLUTION: Output of a passage flow quantity computing means 4 is added as an auxiliary integrated value to an auxiliary integrating means 7, which is periodically cleared by the action of a clearing means 9. Since the auxiliary integrated value is added to a main integrating means 8 as an integrated value when a mean quantity of flow determined by a mean flow computing means 10 on the basis of the auxiliary integrated value is greater than a threshold value, a quantity of flow detected when a fluid is not used is cleared, and a quantity of flow detected when the fluid is used is not cleared. It is therefore possible to prevent the integrated value from increasing when the fluid is not used and reduce integration errors when the fluid is used. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a flow rate measuring device that measures the amount of fluid used by intermittently sampling the flow rate of a fluid based on a detected flow velocity, such as an ultrasonic flow meter or a thermal flow meter.

  Conventionally, many types of flowmeters using thermal flow sensors and ultrasonic sensors have been proposed as this type of flowmeter, and these have the characteristics of a highly sensitive flowmeter that can detect minute flows. .

  However, although a minute flow can be detected, there is a case in which the flow rate is detected in response to a local flow even though there is no fluid flow as a drawback because of high sensitivity.

  In particular, this phenomenon appears remarkably when a large pressure fluctuation occurs in the supply pipe. Therefore, by integrating the detected values as they are, the value of the integrated flow rate may increase even though the fluid use is stopped. In order to prevent this phenomenon, a method has been proposed in which the flow rate value detected by the sensor is once added to auxiliary integration means called a cancellation buffer (see, for example, Patent Document 1).

  That is, the conventional flow rate measuring device covers a wide measurement range (several [L / h] to several thousand [L / h]) like a home gas meter, so that a large flow rate is a fluid oscillation of a fluidic element. The phenomenon is measured by a piezoelectric film sensor, and a small flow rate region where fluid oscillation hardly occurs is measured using a thermal flow sensor.

  FIG. 6 shows the flow rate measuring apparatus, and specifically shows the contents of the measurement process in the small flow rate region, that is, the measurement region of the flow sensor. As shown in FIG. 6, the flow sensor 21, a conversion unit 22, a cancellation buffer 23, a timer 24, an integration unit 25, and a display unit 26 are included. The flow sensor 21 is driven every 6 seconds and outputs an electrical signal corresponding to the flow rate generated in the apparatus.

  Based on the output of the flow sensor 21, the conversion means 22 obtains the flow rate that has passed through the apparatus during the sensor driving interval of 6 seconds and outputs it to the cancellation buffer 23. The value added to the cancellation buffer outputs a signal every time it reaches 1 [L], and the integrating means 25 receives the signal output and adds 1 [L] to the integrated value. Then, the value of the integrating means 25 is displayed on the display means 26.

  In the flow rate measuring apparatus having the above configuration, for example, in the case where a large pressure fluctuation occurs under the condition where no gas is used, the output of the conversion means 22 has a large variation, and is instantaneously positive. In some cases, the value may be large, but on the contrary, a large negative value may be output. If averaged over a long period of time, the value settles to 0 [L].

  However, temporarily, the output may be biased to a positive value. If left as it is, there is a risk that the content of the cancellation buffer 23 reaches 1 [L] and the value of the display means 26 increases. Therefore, the timer 24 periodically clears the accumulated value held in the cancellation buffer 23.

For example, this time is determined as follows. If the judgment criterion for gas leakage is 3 [L / h], this value is considered as the detection lower limit flow rate of the apparatus. When a flow rate of 3 [L / h] is generated, the value of the cancellation buffer reaches 1 [L] in 20 minutes. Therefore, if the clear time set by the timer 24 is set to a value larger than 20 minutes, it is possible to detect 3 [L / h] and to prevent an increase in the integrated value when the gas is not used.
JP 2002-62179 A

  However, in the conventional configuration, when the predetermined time has elapsed, the contents of the cancellation buffer 23 are cleared, so that the value remaining in the cancellation buffer 23 when the use of the gas appliance is stopped is discarded. There is a problem that an integration error occurs.

  This phenomenon will be described with reference to FIG. FIG. 7 shows the movement of the instantaneous flow rate value of the gas appliance, the value of the cancellation buffer 23, and the display value of the display means 26. In FIG. 7, it is assumed that a gas appliance of 15 [L / h] is used for 14 minutes. For simplicity, when the use of the gas appliance is started, the value of the canceling buffer 23 and the value of the integrating means 25 at time T0 are both Set to 0L.

  Since the value of the cancellation buffer exceeds 1 [L / h] at times T1, T2, and T3, 1 [L] is added to the integrating means 25 each time, and at the same time, the cancellation buffer 23 is cleared. At the same time, the timer 24 is restarted.

  Since the use of the gas appliance is stopped at time T4, the value of the buffer 23 remains 0.5 [L] and hardly changes after T4. Then, the cancellation buffer 23 is cleared at time T5 when the clear time 20 minutes has elapsed from time T3 when the integrated flow rate value last increased. The total amount of gas used in T0 to T4 is 3.5 [L], but the value output to the integrating means 25 is actually 3 [L], and the remaining 0.5 [L] is It will be thrown away.

  Including the above case, when the use of the gas appliance is stopped, the flow rate held in the canceling buffer is an arbitrary value between 0 and 1 [L / h], so that the average is 0.5 [ L].

  Therefore, every time the use of the gas appliance is stopped for a time longer than the buffer clear time, the average flow rate of 0.5 [L] is discarded. Therefore, in the case where the small-sized gas appliance is used in small increments for a relatively short time, the relative error cannot be ignored.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object of the present invention is to prevent an integrated value from increasing when a gas is not used and to reduce an integrated error when the gas is used.

  In order to solve the conventional problem, the flow rate measuring device of the present invention adds the output of the passage flow rate calculation means to the auxiliary integration means that is periodically cleared as an auxiliary integration value, and calculates the average flow rate obtained from the auxiliary integration value. When the value is larger than the threshold value, the auxiliary integrated value is added to the main integrating means as the integrated value, so that the flow rate detected when the fluid is not used is cleared, and the flow rate detected when the fluid is used is not cleared but the integrated value. Will be added.

  The flow rate measuring device of the present invention can prevent the integrated value from increasing when the fluid is not used, and can also reduce the integrated error when the fluid is used.

  According to a first aspect of the present invention, there is provided a measuring means for intermittently measuring a physical quantity correlated with a fluid flow rate, a computing means for calculating a fluid flow rate or a flow velocity from the output of the measuring means, and a passing flow rate from the output of the computing means. A passing flow rate calculating means for calculating; and an integrating means for adding the output of the passing flow rate calculating means; the integrating means holding the output of the passing flow rate calculating means; and holding the auxiliary integrating means A main integrating means for adding the auxiliary integrated value every time the auxiliary integrated value to be reached reaches a predetermined value, a clearing means for periodically clearing the auxiliary integrated value, an elapsed time from the start of integration of the auxiliary integrating means, An average flow rate calculation means for calculating an average flow rate from the auxiliary integrated value and a determination means for comparing the output of the flow rate calculation means with a threshold value to determine the magnitude of the flow rate. When the flow rate is large, the flow rate detected when the fluid is not used is cleared by adding the auxiliary integrated value to the integrated value held by the main integrating means before the auxiliary integrated value reaches the capacity. The flow rate detected when using the fluid is not cleared, but is added as an integrated value, so that the integrated value is prevented from increasing when the fluid is not used, and at the same time, the integrated error when using the fluid is reduced. Can do.

  In the second invention, by making the determination threshold value in the determination means variable according to the assumed minimum fluid usage, an appropriate determination value can be determined according to the fluid flow rate to be used. The accuracy of the integrated value can be improved.

  According to a third aspect of the present invention, in the determination means, the flow rate detected when using the fluid is more easily integrated by reducing the determination threshold according to the elapsed time from the start of auxiliary integration, and the integration error when using the fluid is reduced. Can be small.

  According to a fourth aspect of the present invention, the determination means is configured to prohibit determination of the flow rate for a predetermined time from the start of auxiliary integration, so that the use or non-use of fluid can be determined more accurately, and the accuracy of the integrated value is improved. can do.

  According to a fifth aspect of the present invention, when the auxiliary integrated value changes from negative to positive, the average flow rate calculation means calculates the average flow rate based on the elapsed time starting from that time point, so that the fluid flow The beginning can be judged more accurately, and the accumulated error when using the fluid can be reduced.

  According to a sixth aspect of the present invention, when the auxiliary integrated value changes from negative to positive, the clearing means detects the auxiliary integrated value clearing time starting from that point, and detects at the beginning of fluid flow. The flow rate is not cleared by mistake, and the accumulated error when using the fluid can be reduced.

  According to a seventh aspect of the present invention, when the output of the calculating means is larger than a predetermined value, the auxiliary integrated value is added to the main integrating means regardless of the average flow rate, so that when the large flow rate is detected, the integrated value is reliably reflected in the integrated value. In addition, the integration error when using the fluid can be reduced.

(Embodiment 1)
The figure assumes application to a home gas meter.

  In FIG. 1, a flow sensor 2 as a measuring means is disposed in a fluid flow path 1, detects a flow rate in the fluid flow path 1, and outputs an electrical signal corresponding to the flow rate. The calculating means 3 calculates the instantaneous flow rate of the fluid from the output of the flow sensor 2, and the passing flow rate calculating means 4 calculates the passing flow rate of the fluid from the output of the calculating means 3 and outputs the result to the integrating means 5. Then, the display unit 6 displays the accumulated flow rate of the fluid obtained by the integrating unit 5. Further, the integrating means 5 has the following configuration.

  That is, the auxiliary integrating means 7 obtains the integrated value by adding the output of the passage flow rate calculating means. Hereinafter, the integrated value obtained by the auxiliary integrating means 7 is referred to as an auxiliary integrated value. The auxiliary integrated value is output to the main integrating means 8 every time it reaches 1 [L] which is a predetermined capacity, but the clearing means 9 periodically clears the auxiliary integrated value (every 20 minutes). Small values that do not reach a certain level are not accumulated.

  Further, the average flow rate calculation means 10 obtains an average flow rate from the auxiliary integrated value and the start elapsed time of the auxiliary integration. Then, the determination unit 11 performs a binary determination of the flow rate by comparing the output of the average flow rate calculation unit 10 with the determination threshold value set by the setting unit 12. When the determination result is a large flow rate, the auxiliary integrated value is the main integrated value. It is output to the integrating means 8 and added.

  The auxiliary integrated value is added to the main integrating means 8 when the auxiliary integrated value reaches 1 [L] and when the determination result of the determining means 11 is large. The integrated value obtained by the main integrating means 8 is hereinafter simply referred to as an integrated value in order to distinguish it from the auxiliary integrated value. The display unit 6 displays the contents of the main integration unit 8 in units of 1 [L].

  The operation and action of the flow rate measuring apparatus configured as described above will be described below.

  First, an operation until the output of the flow sensor 2 is converted into a passage flow rate will be described. The flow sensor 2 is driven every certain time (for example, 2 seconds), and the flow velocity v generated in the fluid flow path at that time is AD converted and output as a voltage signal E. The flow velocity v and the output of the flow sensor 2 are in a proportional relationship. If E is known, the flow velocity v can be obtained using (Equation 1).

v = K · E (Formula 1)
In (Expression 1), K is a proportionality constant. If the flow velocity distribution in the flow path is uniform, the flow rate of the fluid can be obtained by obtaining the product of the flow velocity and the cross-sectional area S. It is not uniform. Therefore, in order to convert the flow velocity v into the instantaneous flow rate Qs, it can be obtained by (Equation 2) using the correction coefficient M depending on the flow velocity v.

Qs = M · S · v = M · S · K · E (Formula 2)
The calculation means 3 calculates the fluid flow rate using (Equation 2). Further, the passage flow rate Qi in the apparatus for t seconds can be obtained by multiplying the flow rate obtained by (Equation 2) by the driving interval t of the flow sensor 2.

Qi = Qs · t (Formula 3)
For example, if Q is, the value is substituted into (Equation 3) and obtained using (Equation 4).

Qi = 180 [L / h] × 2 [s] × (1 [h] / 3600 [s]) = 0.1 [L] (Formula 4)
The passage flow rate calculation means 4 calculates the passage flow rate using (Equation 3).

  Next, the operation / action of the integrating means 5 will be described. The average flow rate calculation means 10 obtains an average flow rate value from the auxiliary integrated value and the elapsed time after the auxiliary integration is started. The cumulative elapsed time of the auxiliary integrated value is assumed to be 0 in synchronization with the auxiliary integrated value being cleared.

  That is, it is normally cleared periodically (every 20 minutes) as described in the background art, but the auxiliary integrated value reaches a predetermined condition and is added to the main integrating means 8 as will be described later. Also cleared in case. Then, the flow rate per time during the auxiliary integration process, that is, the average flow rate Qav, can be obtained by dividing the auxiliary integrated value Qp at a certain time by the auxiliary integrated elapsed time Tp using (Equation 5).

Qav = Qp / Tp (Formula 5)
For example, if Qp is 0.6 [L] and Tp is 60 seconds, Qav is obtained using (Expression 6).

Qav = 0.6 [L] / 60 [s] = 0.01 [L / s] = 0.01 [L / s] × 3600 [s] / 1 [h] = 36 [L / h]
The determination unit 11 compares the flow rate determination threshold Qth set by the setting unit 12 with the average flow rate Qav. If Qav is larger, “large flow”, and if Qth is larger, “low flow”. Judge. “High flow rate” corresponds to a state where the gas appliance is used, and “Low flow rate” corresponds to a state where the use of the gas appliance is stopped.

  Therefore, the determination threshold value Qth can be rephrased as a threshold value for determining whether or not the gas appliance is used. This determination threshold value Qth is variable, and at the time of installation, the setting value of the setting means 12 can be changed using an external device such as a remote controller according to the situation of each home. For example, by setting a value smaller than the minimum flow rate of the installed gas appliance, it is possible to determine whether the gas appliance is used.

  Next, details of the determination method of the determination unit 11 will be described. FIG. 2 shows an example of the time transition of the average flow rate Qav when no gas is used, that is, when the flow rate is 0 [L / h]. Since the instantaneous flow rate Qs calculated by the calculation means 3 varies, the absolute value of the average flow rate Qav is large at the stage where the elapsed time is shallow, but converges to 0 [L / h] with the passage of time.

  In FIG. 2, the dotted lines indicate the upper and lower limits of values that Qav can take for each elapsed time. This property has the same tendency not only in 0 [L / h] but also in all flow rate values. Therefore, by using this property, by recognizing the fluid flow rate, it is possible to determine the usage state of the fluid and reflect it in the integrated flow rate.

  The specific method will be described with reference to FIG. It is assumed that the minimum flow rate of the gas appliance to be used is 15 [L / h]. In FIG. 3, an example of the time transition of the average flow rate Qav when the instantaneous flow rate is 0 [L / h] and 15 [L / h] is shown by a solid line, and when the instantaneous flow rate is 0 [L / h], the average flow rate calculation means 10 The upper limit value that can be obtained by the average flow rate Qav obtained in step 1 is indicated by a dotted line, and the lower limit value that can be obtained by Qav when the instantaneous flow rate is 15 [L / h] is indicated by a dashed line.

  In this figure, the area above the dotted line shows a state where the flow rate is not 0 [L / h], that is, it can be considered that some gas flow is occurring, and the area below the one-dot chain line indicates that the gas appliance is Indicates a state that is not used. Both curves intersect at the elapsed time T1 and thereafter approach their true values.

  Therefore, after the elapsed time T1, it is possible to distinguish between the two, that is, whether or not the gas appliance is used, by the value of the average flow rate Qav. Therefore, by setting the elapsed time of up to 60 seconds as the determination prohibition time, it becomes possible to more accurately determine the flow rate.

  Since the intersection of the dotted line and the alternate long and short dash line is 7.5 [L / h] when the determination prohibition time is 60 seconds, the flow rate determination threshold Qth is set to 7.5 [L / h], and the average flow rate Qav is set. If Qth exceeds Qth, it is determined that the flow rate is large, and the auxiliary integrated value is added to the integrated value held by the main integrating means 8, and at the same time, the auxiliary integrated value is cleared to 0 [L / h]. To do.

  The operation of the integrating means 5 will be described with reference to FIG. In FIG. 4, the content of the main integrating means 12 when a gas appliance of 15 [L / h] is used, that is, the movement of the integrated value is shown. Further, the threshold value Qth for determining the flow rate in the determining means 11 is 7.5 [L / h]. In order to simplify the explanation, it is assumed that the output of the calculation means 3 is not varied and a true value is obtained. Both the integrated value and the auxiliary integrated value are 0 [L] and immediately before the time T0. The auxiliary integrated value shall be cleared.

  At time T1, 60 seconds after the use of the gas appliance is started at the time T0 and the determination prohibition time is released, the average flow rate Qav is 15 [L / h], and the determination threshold value Qth = 7.5 [L / H], the auxiliary integrated value at this time is added to the main integrating means 8, and the integrated value increases. Here, the integrated value is 0.25 [L] from the following equation.

15 [L / h] × 60 [s] × (1 [h] / 3600 [s]) = 0.25 [L] (Formula 6)
Thereafter, since the constant flow rate 15 [L / h] continues, the integrated value increases by 0.25 [L] every 60 seconds. At time T3, when the use of the gas appliance is stopped, the value remaining in the auxiliary integrated value is 0.25 [L] at the maximum, but in FIG. 2, it is half of 0.25 [L]. It shall be 0.125 [L].

  If the use of the gas appliance is stopped as it is, the average flow rate gradually decreases starting from 15 [L] at time T3. Finally, the average flow rate Qav at the time T4 when the determination prohibition time of 60 seconds has elapsed from the time T2 at which the integrated value is added is obtained by (Expression 7).

Qav = 0.125 [L] / 60 [s] = 0.125 [L] / 60 [s] × (3600 [s] / 1 [h] = 7.5 [L / h] (Expression 7)
Since this value is equal to or greater than Qth, the auxiliary integrated value 0.125 [L] is output to the integrating means 8 and added to the integrated value at time T4. Here, the obtained value is a condition for preventing the auxiliary integrated value from being cleared. Even if the auxiliary integrated value is cleared, the maximum value is 0.125 [L].

  Therefore, if the auxiliary integrated value does not reach 1 [L] as in the background art, the integrated error at the end of use of the gas appliance can be made much smaller than the configuration in which the auxiliary integrated value is not added as the integrated value. In the above description, the determination threshold value Qth is described as being fixed regardless of the elapsed time. However, the determination threshold value for Qth is made to coincide with the solid line in FIG. 3, that is, the variation upper limit value of 0 [L / h]. Alternatively, it may be configured such that a curve connecting neighboring values taking a larger value than this curve decreases with the elapsed time.

  In this case, since the determination threshold value decreases with time, the probability that the auxiliary integrated value held in the auxiliary integrating means 7 will be added to the integrated value after the use of the gas appliance is increased. The integration error can be further reduced.

  On the other hand, the use start time T0 of the gas appliance and the auxiliary integration start timing are not always synchronized. There may be a delay from the start of auxiliary integration to the start of the gas appliance. In this case, the auxiliary integrated value starts from 0 [L] and increases with time. If the auxiliary integrated value reaches 1 [L] before the auxiliary integrated value clearing time of 20 minutes elapses, this value is added as an integrated value to the main integrating means 8 in the same manner as in the background art. Furthermore, since the average flow rate Qav may exceed 7.5 [L / h], it can be said that the integrated error at the start-up of the gas appliance can be reduced as compared with the background art.

  For example, a configuration as shown in FIG. 5 may be used as a method of reducing the accumulated error at the beginning of using the gas appliance. FIG. 5 shows the transition between the elapsed time from the start of auxiliary integration and the auxiliary integration value. The gas appliance is started to be used at time T0, and the output of the calculation means 3 shows a large variation in the time zone before that time. Therefore, the complementary integrated value vibrates up and down around 0 [L]. Yes. Assuming that the gas appliance is used from the elapsed time T0, for example, the average flow rate Qav at the elapsed time T2 is obtained by (Equation 8).

Qav = Qa / T2 (Formula 8)
However, in this case, it is obvious that a more accurate average flow rate is obtained starting from the time when the auxiliary integrated value changes from a negative value to a positive value. Therefore, in such a case, it may be determined by regarding the elapsed time as 0 at the elapsed time T0 when the auxiliary integrated value has changed from negative to positive. If this concept is used, the average flow rate Qav can be obtained using (Equation 9).

Qav = Qa / Ta = Qa / (T2-T1) (Formula 9)
At this time, the clearing unit 9 may also start the measurement for 20 minutes, which is the clearing period, when the elapsed time T1 is reached. In this case, even if the elapsed time T1 is just before the clearing time of 20 minutes, the auxiliary integrated value is not cleared, and the integrated error at the beginning of using the gas appliance is further reduced. The accuracy can be further increased.

  The above has described the minimum flow rate of 15 [L / h] for gas appliances. However, if a gas appliance with a much larger flow rate is used, the gas appliance is used immediately. Can be judged. Therefore, in such a case, if the constitution is such that the auxiliary integrated value is added to the integrated value regardless of the average flow rate Qav, the detected flow rate will not be cleared. You can make it smaller.

  As described above, in the present embodiment, the output of the passage flow rate calculating means 4 is added as an auxiliary integrated value to the auxiliary integrating means 7 that is periodically cleared, and the average flow rate obtained from the auxiliary integrated value is larger than the threshold value. Since the auxiliary integrated value is sometimes added to the main integrating means 8 as an integrated value, the flow rate detected when the fluid is not used is cleared, and the flow rate detected when the fluid is used is not cleared. While preventing the integrated value from increasing, the integrated error when using the fluid can be reduced.

  Further, by making the determination threshold value in the determination means 11 variable according to the assumed minimum fluid usage, an appropriate determination value can be determined according to the fluid flow rate used. The accuracy of the value can be improved.

  Moreover, since the flow rate detected at the time of fluid use becomes easy to be integrated by making the determination threshold value in the determination means 11 small according to the elapsed time from the start of auxiliary integration, the integration error at the time of fluid use is reduced. Can do.

  In addition, by determining that the determination unit 11 prohibits the flow amount determination for a predetermined time from the start of auxiliary integration, it is possible to more accurately determine whether the fluid is used or not used. Can be improved.

  Further, when the auxiliary integrated value changes from negative to positive, the average flow rate calculation means 10 is configured to calculate the average flow rate based on the elapsed time starting from that time, thereby starting the fluid flow. Since it becomes possible to judge more accurately, the integration error when using the fluid can be reduced.

  Further, when the auxiliary integrated value changes from negative to positive, the clearing unit 9 determines the auxiliary integrated value clearing time from that point of time, so that the flow rate detected at the beginning of fluid flow is Since it is not cleared by mistake, the accumulated error when using the fluid can be reduced.

  Further, if the output of the calculating means 3 is larger than a predetermined value, the auxiliary integrated value is added to the main integrating means 8 regardless of the average flow rate, so that when a large flow rate is detected, it is reliably reflected in the integrated value. Therefore, the integration error when using the fluid can be reduced.

  The flow rate measuring device of the present invention can prevent an increase in the value of the display means when the fluid is not used, and at the same time, can reduce the integrated error when the fluid is used. It can also be applied to uses such as meters.

Block diagram of a flow rate measuring device in Embodiment 1 of the present invention A characteristic diagram explaining the operation of the integrating means Another characteristic diagram explaining the operation of the accumulating means Another time chart explaining the operation of the accumulating means Another time chart explaining the operation of the accumulating means Block diagram of a conventional flow measurement device Time chart explaining the operation of a conventional flow rate measuring device

Explanation of symbols

2 Flow sensor 3 Computing means 4 Passing flow rate computing means 5 Accumulating means 7 Auxiliary integrating means 8 Main integrating means 9 Clearing means 10 Average flow rate calculating means 11 Judging means 12 Main integrating means

Claims (7)

Measuring means for intermittently measuring a physical quantity correlated with the flow rate of fluid, calculating means for calculating a fluid flow rate or flow velocity from the output of the measuring means, and passing flow rate calculating means for calculating a passing flow rate from the output of the calculating means And an integrating means for adding the output of the passing flow rate calculating means, wherein the integrating means has an auxiliary integrating means for adding the output of the passing flow rate calculating means, and an auxiliary integrated value held by the auxiliary integrating means is predetermined. A main integrating means for adding the auxiliary integrated value every time the value is reached, a clear means for periodically clearing the auxiliary integrated value, an elapsed time from the start of integration of the auxiliary integrating means, and the auxiliary integrated value An average flow rate calculation means for calculating an average flow rate, and a determination means for comparing the output of the flow rate calculation means with a threshold value to determine the magnitude of the flow rate. When the determination result of the determination means is large , The flow rate measuring device the auxiliary integrated value has the auxiliary integrated value before reaching the capacity to be added to the accumulated value held by the main accumulation unit. The flow rate measuring apparatus according to claim 1, wherein a determination threshold value in the determination unit is variable in accordance with a minimum assumed fluid usage amount. The flow rate measuring device according to claim 1 or 2, wherein the determination threshold value in the determination means is determined so as to decrease according to an elapsed time from the start of auxiliary integration. The flow rate measuring device according to any one of claims 1 to 3, wherein the predetermined time from the start of auxiliary integration is configured to prohibit the flow size determination by the determining means. 5. The structure according to claim 1, wherein when the auxiliary integrated value changes from negative to positive, the average flow rate calculation means calculates the average flow rate based on an elapsed time starting from that point. Flow measurement device. 6. The flow rate measuring device according to claim 5, wherein when the auxiliary integrated value changes from negative to positive, the clearing unit determines a clear time of the auxiliary integrated value starting from that point. The flow rate measuring apparatus according to any one of claims 1 to 6, wherein the auxiliary integrated value is added to the main integrating means regardless of the average flow rate if the output of the calculating means is larger than a predetermined value.

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