JP2001281041A - Gas meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cut off an over flow without influence of pulsation in a gas meter that leads from an instantaneous flow rate that is discretely measured to an integrating flow rate for a definite time. SOLUTION: A setting means for setting the upper limit value of a dead zone is provided based on one or more kinds of functions from among a statistical function showing the dispersion of the instantaneous flow rate, a function consisting of the differences in the continuous instantaneous flow rates, and a function of a progression consisting of a variation of the instantaneous flow rate per unit time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas meter provided with an instantaneous flow rate measuring means for measuring an instantaneous flow rate which is discretely measured, and relates to a gas meter which derives a used flow rate or the like from the measured instantaneous flow rate.

[0002]

2. Description of the Related Art Conventionally, as a flow meter used for a gas meter, a membrane type flow meter is mainly used. However, due to its convenience and the like, a meter using an ultrasonic wave and a heat conduction type flow sensor are presently used. Meters that use the same have been proposed.
In such a meter, the flow rate taken in is an instantaneous flow rate obtained by being temporally discrete from the measurement principle, and the data sequence is a discrete type.

On the other hand, a gas meter for detecting the flow rate of gas supplied downstream of the meter is provided with a dead zone for the flow rate. In principle, this dead zone is used to set the unstable region to zero output when the reliability of the measurement cannot be ensured due to the relationship between the measurement principle and the like. Usually, the upper limit of this dead zone is set as described above,
The constant value is set in advance depending on the model and number of the gas meter (set by the standard flow rate measured by the meter). Further, conventionally, the dead zone is always set, and if a flow rate lower than the above-mentioned fixed value is detected, it is determined that there is no detected flow rate.

[0004]

With respect to this dead zone, the following events occur. (1) If the set value of the upper limit of the dead zone is too low, a so-called over-count state occurs in each customer to which the meter is attached, in which a gas flow rate larger than the original usage is measured. (2) If the set value of the upper limit of the dead zone is too high, an unmeasured gas amount to be measured without gas supply is generated even though gas is supplied. (3) Furthermore, the measurement accuracy and the like of a meter originally change due to seasons, changes over time, and the like, and an error term in a general sense is generated. Conventionally, the dead zone is set to be constant. Therefore, the dead zone is set on the wide side without following such a change. (4) The measurement principle of the flow rate is as follows:
In the configuration in which the used flow rate or the like is obtained from a large number of measured instantaneous flow rates, if there is a pulsation in the flow, an error due to the relationship between the pulsation and the discretized measurement timing is a small area of the flow rate. May affect the flow rate measurement results, taking into account the effects of such errors, the dead zone should be originally set, but such factors have not been considered at all .

It is an object of the present invention to provide a gas meter having an instantaneous flow rate measuring means for measuring an instantaneous flow rate measured discretely, and having a reasonable dead zone capable of coping with the above-mentioned problem. is there.

[0006]

In order to achieve this object, a flow rate deriving method according to the present invention is characterized in that a statistical function representing a variation in an instantaneous flow rate is used as a continuous function. A dead band upper limit setting unit that sets the upper limit value of the dead band based on at least one of a statistical function of a sequence consisting of a difference in instantaneous flow rate or a statistical function of a sequence consisting of a change amount of the instantaneous flow per unit time. Have prepared. In the apparatus provided with the dead zone upper limit setting means, the upper limit of the dead zone is set based on one of the statistical functions. In such a setting, a statistical function may be placed on a fixed value serving as the basis of the dead zone, or the width of the dead zone may be determined from the statistical function itself. Now, the nature of the statistical function used in the present application is basically a physical quantity that can represent variations in instantaneous flow rate measured by being discretized, fluctuations, and the like.
This can be regarded as including an error that may occur when the instantaneous flow rate is discretely measured. For example, when a pulsating component is included in the flow rate and the measurement timing of the instantaneous flow rate is randomized and set in a distributed manner, the measurement time required for the instantaneous flow rate cannot be a target of the dispersion processing. For example, in the case where n measurements are performed within a certain integration time T, if the measurement time required for one measurement is Δt, the time zone of T−n × Δt can be dispersed and the error factor is low, The time of n × Δt cannot be a target of dispersion. Therefore,
There is a high possibility that an error corresponding to this time will occur. Such error factors affect the flow rate which should be measured by the meter, and also affect the reliability of the dead zone. Therefore, this should be considered when setting the upper limit (the lower limit is naturally 0) of the dead zone. By doing so, for example, it is possible to measure the flow rate with the measurement error factor removed, and as a result, it is possible to accurately measure the flow rate without overcounting in a state where the unmeasured flow rate is not excessive. Becomes Here, any of the statistical function representing the variation of the instantaneous flow rate, the statistical function of a sequence composed of the difference between the continuous instantaneous flow rates, or the statistical function of the sequence composed of the amount of change in the instantaneous flow rate per unit time is as described above. Since it is a preferable physical quantity in view of the influence of fluctuation and the like, it can be suitably adopted.

[0007] In the above derivation method according to claim 1,
As described in claim 2, to determine the use flow rate, which is the flow rate supplied to the downstream side of the meter during the use period, from the instantaneous flow rate measured during the use period,
It is preferable that the upper limit value of the dead zone is adapted to the instantaneous flow rate measured during the use period to obtain the use flow rate. By employing this configuration, it is possible to obtain a flow rate without excess or deficiency as the usage flow rate.

In the above configuration, an average measurement timing interval for measuring the instantaneous flow rate is set in advance, and an interval between the instantaneous flow rate measurement completion time point when the instantaneous flow rate is measured and the subsequent instantaneous flow rate start time point is set. With respect to a discrete interval which is a time, a discrete interval for processing the discrete interval so that a sum of an average value of a large number of discrete intervals and a measurement required time required for measuring the instantaneous flow rate is the average measurement timing interval. In order to set an upper limit value of the dead zone from the statistical function, it is preferable that the upper limit value is set based on the average measurement timing interval and the required measurement time.

As described above, when a discrete measurement structure is provided, even if the measurement timing is dispersed based on randomization processing or the like, the time required for measurement that cannot be randomized (measurement time) is reduced. The resulting error occurs. If the measurement object includes a pulsation and the cycle of the pulsation coincides with the average measurement timing interval, the pulsation component significantly contributes to the above-described statistical function which is an error factor. Therefore, when the upper limit of the dead zone is determined based on a statistical function having a property as an error in anticipation of this contribution, the upper limit value is determined based on the average measurement timing interval and the required measurement time in consideration of this effect. Is set, the error factor when the complete distributed processing cannot be performed can be well represented in the dead zone.

The structure described above is based on the premise that a dead zone is provided. However, the setting of the dead zone based on the variation caused by the measurement structure or the like as in the present application allows the variation as it is. (There is no dead zone) and an effective measurement amount may prevent occurrence of an unmeasured flow rate. Such an example occurs when a relatively large amount of gas is flowing and a temporary shut-off condition occurs. The following configuration example attempts to cope with such a situation. That is, comprising an instantaneous flow rate measuring means for measuring the instantaneous flow rate measured discretely, the use flow rate which is the flow rate supplied to the meter downstream side during the use period,
The gas meter obtained from the instantaneous flow rate measured during the use period, as described in claim 3, is configured to be able to set a dead zone of the flow rate where the flow rate output in the minute flow rate area is set to the zero flow rate output. In deriving the used flow rate in the inside, a dead zone setting state for providing the dead zone,
It is configured to be switchable to a dead zone non-setting state in which the dead zone is not provided. By doing so, the case where the dead zone is adapted and the case where the dead zone is not adapted can be executed by state switching. That is, for example, when there is a high probability that the unmeasured flow rate is high, the state is switched to the dead zone non-set state, and the flow rate of the dead zone is set as the measurement target,
Unmeasured flow can be reduced.

A case where such switching is appropriate is a case where the customer to be measured uses a certain amount or more of gas. In such a case, for example, as described in claim 4, The apparatus further includes a dead zone setting switching unit that sets the dead zone at the start point of the use period and sets the dead zone to a non-set state when a flow rate exceeding a certain flow rate is measured during the use period. If you do this,
In the case where the gas is consumed at a certain flow rate or more, which has a high probability of being in a normal normal use state, the occurrence of an unmeasured flow rate can be reliably prevented.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
It will be described based on. The gas meter 1 includes a measuring pipe 2 for obtaining information on a predetermined flow using ultrasonic waves,
A system for obtaining the instantaneous flow rate referred to in the present application based on the information from the measurement pipe 2 and a system for obtaining the used flow rate and the safety function flow rate in the present application from the obtained instantaneous flow rate are provided. That is, the gas meter 1 includes the above-described measuring tube 2 and a meter body 7 to which the output end 2a of the measuring tube 2 is connected. The processing system is stored as various means.

In the measuring tube 2, the gas f to be measured is
It flows into the measuring pipe 2 from the introduction part 3 and is discharged from the outlet part 4. In the figure, the flow direction of the gas f in the measurement tube 2 is from left to right on the figure, as indicated by the large arrow. The left side is the upstream side, and the right side is the downstream side. The measuring tube 2 is provided with a pair of transducers 5 provided in a predetermined direction with respect to the measuring tube 2. The distance L between the transducers 5 is fixed. The transmitter / receiver 5 includes an ultrasonic transmitter 5a and a receiver 5b, respectively.
In accordance with a command from the main unit, the transmitter 5a on one side
The ultrasonic wave can be transmitted from one side to the other side, and the receiver 5b on the other side receives the ultrasonic wave transmitted from the one side at a predetermined timing, thereby transmitting the ultrasonic wave. It is configured to be able to determine the time (the time difference between the transmission timing at the transmitter 5a on one side and the reception timing at the receiver 5b on the other side).
This operation can be similarly performed for the transmitter 5a and the receiver 5b that are in a reversed positional relationship with respect to the flow direction. The forward direction along the flow direction (from left to right on the drawing) and Ultrasonic waves are propagated in both directions, that is, in the opposite direction (from right to left in the figure), and a configuration is employed in which the propagation time of each ultrasonic wave can be obtained.

In the above structure, the measurement of the propagation time is such that the ultrasonic wave is propagated in the forward direction in which the sound propagation direction is along the flow, and the ultrasonic wave propagates between the transducer in the forward direction. An operation for obtaining the forward propagation time t10 and an operation for obtaining the backward propagation time t20 in which the ultrasonic wave propagates in the reverse direction, which is the direction opposite to the flow, and the ultrasonic wave propagates between the transducers in the opposite direction are paired. , Is executed by the instantaneous flow rate measuring means 6.

The instantaneous flow rate measuring means 6 calculates the gas flow velocity Vx (this is a flow velocity component along the ultrasonic wave propagation direction) based on the output forward propagation time t10 and backward propagation time t20. In addition, a single flow rate is obtained in consideration of the cross-sectional area S1 of the measurement unit and the flow coefficient β of the measurement unit.
The flow velocity Vx and the instantaneous flow rate Q are given by the following equations.

[0016]

Vx = L × (1 / t10-1 / t20) / 2 Q = Vx × S1 × β × cos (θ)

The instantaneous flow rate Q is a value obtained by one measurement, and is measured discretely. The measurement timing of the instantaneous flow rate is individually given by the measurement time control unit 8 including the clock 8a and the dispersion unit 8b. The operation of the measuring time control means 8 will be described with reference to FIGS. In the figure, individual measurement timings are shown as discrete points on the horizontal axis. It is the role of this means 8 to issue a command for each measurement timing, but the setting of the mutual measurement timing is also controlled by this means 8.
This control is executed by the distributing means 8b by employing the following sequence. The integration time T is preset as an appropriate constant value such as tens of minutes to several hours in consideration of the use of the gas meter and the like. In addition, the number of measurement timings (sampling number n) within the integration time T is also set to 100 to 30,000 in consideration of the purpose of use and the like. Therefore, the reference sampling interval is about 1 second. Now, each measurement timing is defined as the integration time T, the time required for one measurement in which the forward and reverse directions are paired by ultrasonic waves (this measurement time is not only the time required for the measurement but also the time required in the CPU). (Including a prohibition time that cannot be included in the measurement of the magnetic field generated due to the balance with other calculations) Δt, and N is a single-digit random number generated every time the measurement timing is set, based on the following equation. . In this case, the time from one measurement timing to the next measurement timing is as follows.

[0018]

## EQU2 ## Δt + (T / n−Δt) × N / ｛(1 + Nma
x) / 2} Here, the random number N is a random number generated in an integer range from 1 to Nmax, and it is assumed that the probability of occurrence of each number is the same. This sequence is sequentially repeated.

That is, in the processing in the dispersing means 8b, the average measurement timing interval T / n for measuring the instantaneous flow rate is set in advance, and the instantaneous flow rate measurement time when the instantaneous flow rate is measured and the subsequent instantaneous flow rate are measured. Regarding the measurement timing interval (time called the discrete interval, which is T / n-Δt in the above case), which is the time between the start of the flow and the average value of the many discrete intervals, the measurement of the instantaneous flow is required. The sum with the required measurement time Δt is the average measurement timing interval T /
The discrete intervals are varied so as to be n.
Therefore, by adopting this configuration, the number of samplings n within the integration time T can be statistically secured, and the occurrence of errors due to logical resonance can be significantly reduced by varying the timing. 2 and 3, the measured values of the instantaneous flow rate are shown as points on the flow rate line of the analog display described as the actually measured flow rate.

In this way, a plurality of instantaneous flow rates Q within a predetermined integration time T are obtained.

First, a system for obtaining the safety function flow rate Qsa from the instantaneous flow rate Q described above will be described. The error function obtained by this system is used for setting a dead zone, which is a feature of the present invention, as described later.

The part for deriving the safety function flow rate Qsa is calculated based on a plurality of instantaneous flow rates Q measured within the integrated time T from:
It is a first statistical function deriving means 9 for obtaining a first statistical function representing a variation in a plurality of instantaneous flow rates Q, and a statistical function of a difference between continuous instantaneous flow rates for a plurality of instantaneous flow rates Q measured within an integrated time T. A second statistical function deriving unit 10 for obtaining a second statistical function. Then, the first statistical function obtained by the first statistical function deriving means 9 and the second statistical function obtained by the second statistical function deriving means 10 are:
An error function deriving means 11 for obtaining an error function which is one or both functions is provided. Further, a safety function flow deriving means 13 for obtaining the safety function flow Qsa for the safety function based on the error function obtained by the error function deriving means 11 and the integrated flow rate obtained by the integrated flow deriving means 12 is provided. I have. The flow rate for safety function Qsa obtained by the flow rate deriving means 13 for safety function is used for determining whether or not a pipe (not shown) in which the gas meter 1 is provided is cut off. Blocking is performed.

Hereinafter, the individual means shown in FIG. 1 will be described. B. Integrated flow rate deriving means 12 The integrated flow rate Q as a product of the average of the instantaneous flow rates Q input within the integrated time from the instantaneous flow rate measuring means 6 and the integrated time.
Sum is derived. In this means, as described later, a dead zone process which is a characteristic configuration of the present application is performed.
This processing will be described again. This integrated flow Q
sum is a flow rate deriving means 13 for safety function, dead zone processing,
It is sent to the used flow rate deriving means 16. (B) First statistic deriving means 9 The standard deviation σ of the instantaneous flow rate Q input within the integration time is derived from the instantaneous flow rate measuring means 6. This standard deviation σ
Is sent to the error function deriving means 11. (C) second statistic deriving means 10 derives the average dm of the absolute value of the difference between successive instantaneous flow rates Q input within the integration time from the instantaneous flow rate measuring means 6. The average dm of the differences is sent to the error function deriving means 11. D. Flow rate deriving means 13 for safety function An error function obtained by weighting the standard deviation σ as the first statistical function and the average dm of the difference as the second statistical function is received from the error function deriving means 11 and input. The flow rate Qsa for the safety function is obtained by adding or subtracting the cumulative flow rate Qsum that comes. This flow rate for the safety function can be expressed as follows.

[0024]

[Mathematical formula-see original document] Qsa = Qsum + a1 * [sigma] + a2 * dm Here, a1 and a2 are constants set in advance based on the integration time T and the type of the variation index.

For example, as (a1, a2), (-2,
In the case of adopting (0), the flow rate for the safety function on the lower side (shown by a long broken line) in FIGS. 2 and 3 is given, and in the case of (2, 0), the flow rate for the safety function on the higher side (short broken line) ). When such a flow rate for the safety function on the lower side is employed, about 90% of malfunction due to pulsation can be prevented. Furthermore, as (a1, a2), (0, -dm / sq
rt (n)). In this case, substantially the same effects as described above can be obtained. Also, in this method, the determination time can be reduced.

As (a1, a2), it is also possible to adopt a combination of mutually valid numbers. For example,
By dividing the accumulated time into smaller times, determining the relationship between the standard deviation and the average of the differences within the divided time,
The combination may be changed by determining the pulsation and the ON / OFF of the device. Further, in terms of the relationship between the pulsation cycle and the average measurement timing interval, in the situation shown in FIG. 2 where the pulsation cycle is smaller than the average measurement timing interval, the measurement of the instantaneous flow rate is performed almost randomly with respect to the phase of the pulsation. Since the average of the absolute value of the difference is proportional to the pulsation amplitude, a method of taking a multiple of this average is appropriate. On the other hand, in a situation as shown in FIG. 3 where the pulsation cycle is larger than the average measurement timing interval, there is no significant difference between the standard deviation indicating the degree of variation and the average. Therefore, the multiple of the average of the absolute values of the differences is one function that can be easily and usefully selected and used in the structure of the present invention.

The above is the part for obtaining the flow rate for the safety function. In parallel with this part, there is provided a system for obtaining the flow rate of gas supplied downstream from the meter within a predetermined usage period. Have been. This system is a system for obtaining the used flow rate ΣQsum based on the integrated flow rate Qsum and the error function, similarly to the safety system described above.

In the dead zone processing, upon receiving the above error function, when deriving the integrated flow rate by the integrated flow deriving means 12, information for setting whether or not to perform the dead zone processing is output. That is, as shown as dead zone processing in FIG. 1, there is provided a dead zone upper limit setting means 14 for setting the upper limit of the dead zone in response to the above-mentioned error function, and whether the setting by the dead zone upper limit setting means 14 is applied. (In other words, the apparatus is provided with a dead zone setting switching unit 15 for making a determination to switch between a dead zone setting state where a dead zone is provided and a dead zone non-setting state where no dead zone is provided. Information on such a dead zone is sent to the integrated flow rate deriving means 12, and is used when the integrated flow rate deriving means 12 derives the aforementioned integrated flow rate Qsum. Hereinafter, each means will be described in order.

E Dead zone upper limit setting means 14 This means sets the upper limit of the dead zone based on a statistical function (specifically, the above average dm) of a sequence consisting of the difference between the continuous instantaneous flow rates. This dead zone is a region from the flow rate 0 to its upper limit value ULmax, and the upper limit is set as follows.

[0030]

## EQU4 ## ULmax = ULmin + ΔQ ΔQ = k1 × k2 × dm

Here, ULmin is the minimum value (0 or finite value) of the dead zone, k1 is one or more constants depending on incompleteness in distributed processing involving random number generation, and k2 is
A constant representing the effect of the time Δt required for ultrasonic measurement when a pulsation represented by cos (φ) having the same cycle as the integration time enters. + Θ and the pulsation period from −π to + π is defined as follows.

[0032]

## EQU5 ## k2 = k21 / k22 k21 is the integral area from -.theta.
(Φ) dφ k22 is obtained by setting the integration area from −π to + π, {cos
(Φ) dφ

Therefore, in order to set the upper limit of the dead zone from the statistical function, which is an error function, the average measurement timing interval (which is included in the range from -π to + π) and the required measurement time (which is included in the range from -θ to + θ). ), The contribution is expected.

By employing this configuration, the upper limit ULmax of the dead zone is variably set according to the state of the instantaneous flow rate. This dead zone upper limit information is sent to the integrated flow rate deriving means 12.

The dead zone setting switching means 15 This means is used for the instantaneous flow rate Q
This is a means for switching whether to set a dead zone when deriving the integrated flow rate Qsum from. As described above, the meter can operate in both a dead zone setting state in which a dead zone is provided and a dead zone non-setting state in which a dead zone is not provided, but this means handles this switching setting, and switches information. Integrated flow rate deriving means 1
Send to 2. More specifically, this means outputs switching information for setting a dead zone at a start point of a use period, and when a flow rate exceeding a certain flow rate is measured during the use period, the dead zone is not set. The switching information for setting the state is output. Therefore, if the gas flow is measured only at a certain flow rate or less during the use period, the dead zone is always applied during the use period, and overcounting can be substantially prevented. On the other hand, when a certain amount or more is used, the dead zone is not set, and a significant flow rate is set up to a minute flow rate region which has not been measured conventionally. As a result, an unmeasured flow rate can be prevented from being generated.

(A) Integrated flow deriving means 12 As described above, this integrated flow deriving means 12
Derives an integrated flow rate Qsum from the instantaneous flow rate measuring means 6 as a product of the average of the instantaneous flow rates Q input within the integrated time and the integrated time, and sends the integrated flow rate Qsum to a predetermined portion. However, when calculating the integrated flow rate Qsum, the upper limit information of the dead zone and the switching information are used. This process is performed as follows. E1 Dead zone non-setting state The dead zone is not set at all, all the instantaneous flows input within the integration time are integrated, the average instantaneous flow is obtained, and the integrated flow Qsum is obtained based on the result. E2 Dead zone setting state Based on the dead zone upper limit information, all instantaneous flows lower than this upper limit are regarded as zero instantaneous flow outputs, and the average instantaneous flow is obtained.
An integrated flow rate Qsum is obtained based on the result. In this case, the setting of the dead zone is performed. However, in the case where ULmin is a finite value in Equation 4, it is possible to select both the state where the application of ΔQ targeted by the present application is performed and the state where the ΔQ is not performed. Is also good. The integrated flow rate Qsum thus obtained is sequentially sent to the used flow rate deriving means 16.

G. Used flow rate deriving means 16 The integrated flow rate Q sequentially sent from the integrated flow rate deriving means 12
sum is added within a predetermined use flow rate period, and the use flow rate Σ
Obtain and output Qsum. With the above configuration, it is possible to change the upper limit of the dead zone depending on the measurement situation, and it is possible to select a case where the dead zone is applied and a case where the dead zone is not applied.

[Another Embodiment] (1) In the above-described embodiment, an example in which a flow rate is measured by an ultrasonic wave has been described as an example, but an integrated flow rate is obtained from an instantaneous flow rate that is discretely measured. In addition to those using a heat conduction type flow sensor as a main part of the flow measurement, there are also electromagnetic types and the like, and the present invention is applicable to all of them. (2) In the above embodiment, the error function is defined with respect to the integrated flow rate. However, after a lapse of the integrated time, the error function of the present application is calculated based on a plurality of obtained instantaneous flow rates. A function corresponding to the function may be individually obtained for the instantaneous flow rate, and based on this, the instantaneous flow rate itself may be individually subjected to error correction processing.However, when this method is employed, correction of the instantaneous flow rate and its Since a detour procedure of deriving the flow rate from the corrected value is taken, and finally, it is necessary to obtain the flow rate for the safety function with respect to the integrated flow rate, it is considered to be substantially equivalent. (3) In the above-described embodiment, the standard deviation is used as the first statistical function. However, a variance or the like may be used as the statistical function representing the variation in the integrated flow rate. (4) In the above-described embodiment, the average value of the absolute values of the differences between the continuous instantaneous flow rates is adopted as the second statistical function. A statistical function such as an average value may be defined as a second statistical function, and a statistical function such as an average value of a series of numbers of changes in instantaneous flow rate per unit time may be defined as a second statistical function. Further, in addition to the function corresponding to the first derivative of the flow rate, a function corresponding to the second derivative and the like can be adopted. (5) In the above-described embodiment, the flow rate for the safety function is obtained by linearly connecting the integrated flow rate and the error function. On the other hand, a flow rate that becomes a constant rate may be used as the flow rate for the safety function. That is, the flow rate for the safety function can be determined from the integrated flow rate and the error function. (6) In the above embodiment, the average of the differences dm was used to set the upper limit of the dead zone. However, the above-described statistical function representing the variation of the instantaneous flow rate such as the standard deviation σ was used. Alternatively, any one or more of a statistical function of a sequence consisting of a difference between successive instantaneous flow rates or a statistical function of a sequence consisting of a change amount of an instantaneous flow per unit time may be used. Further, in the above-described embodiment, the upper limit of the dead zone is set by the procedure shown in Expression 4, but ΔQ may be set in consideration of the following error factors.

Error 1 to be considered Error due to imperfect randomization of the measurement timing interval ΔQ1 This maximum value is represented by A × sin (π × Δt × n) where A is the amplitude of a pulsation synchronized with the average flow rate measurement interval. / T) / π. 2 Error due to the sample number not being sufficiently large within the integration time ΔQ2 = A × / sqrt (n) 3 Error due to the flow velocity distribution of the gas flowing through the measuring part being different from the steady flow ΔQ3 This is the difference between ΔQ1 and ΔQ2. Small enough. Here, A can be the mean square of the difference described above, and as a result, ΔQ1 + ΔQ2, which is the error function of the present application, is obtained using the mean square, and the upper limit of the dead zone is set from this. It is also possible. Specific values when setting in this way are as follows. T / n
= 1 sec, Δt = 0.1 sec, n = 400, and if the mean square of the difference is 1 (m ³ / h) ² , A = 1 m ³ / h
Therefore, assuming that ULmin = 0, ΔQ1 = 0.028 m ³
/ H, ΔQ2 = 0.05 m ³ / h, ΔQ = 0.07
8 m ³ / h. This value may be set as the upper limit of the dead zone. This error function gives a value close to the value of the dead zone actually used for the current meter, and it can be seen that the present method is effective.

[Brief description of the drawings]

FIG. 1 is a diagram showing a system configuration of a gas meter of the present application.

FIG. 2 is an explanatory diagram showing a situation when a pulsation cycle is short.

FIG. 3 is an explanatory diagram showing a situation when a pulsation cycle is long.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gas meter 2 Measuring pipe 3 Introducing part 4 Deriving part 5 Transceiver 5a Transmitter 5b Receiver 6 Instantaneous flow rate measuring means 7 Meter body 8 Measurement time control means 8a Clock 8b Dispersing means 9 First statistical function deriving means 10 First Two statistical function deriving means 11 Error function deriving means 12 Integrated flow deriving means 13 Flow deriving means for safety function 14 Dead zone upper limit setting means 15 Dead zone setting switching means 16 Usage flow deriving means

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Shigeru Tagawa 4-1-2, Hirano-cho, Chuo-ku, Osaka-shi, Osaka F-term in Osaka Gas Co., Ltd. (reference) 2F030 CA03 CC13 CE24 CE25 2F035 DA14

Claims (4)

[Claims] 1. A gas meter comprising an instantaneous flow rate measuring means for measuring an instantaneous flow rate measured discretely, and having a dead zone of a flow rate in which a flow rate output in a predetermined minute flow rate range is a zero flow rate output. Based on at least one of a statistical function representing a variation in instantaneous flow rate, a statistical function of a sequence consisting of a difference between successive instantaneous flow rates, or a statistical function of a sequence consisting of a change amount of instantaneous flow rate per unit time, A gas meter provided with a dead zone upper limit setting means for setting an upper limit value of a dead zone. 2. A method for determining a use flow rate, which is a flow rate supplied to a downstream side of a meter during a use period, from the instantaneous flow rate measured during the use period, wherein the instantaneous flow rate measured during the use period is used. The gas meter according to claim 1, wherein the use flow rate is determined by adapting an upper limit value of the dead zone. 3. An instantaneous flow rate measuring means for measuring an instantaneous flow rate measured discretely, wherein an operating flow rate, which is a flow rate supplied to a downstream side of the meter during a use period, is measured during the use period. A gas meter obtained from a flow rate, wherein a dead zone of a flow rate in which a flow rate output in a predetermined minute flow rate area is set to a zero flow rate output can be set, and a dead zone setting state in which the dead zone is provided in deriving a use flow rate in the use period. And a gas meter configured to be switchable between a dead zone not set and a dead zone not provided. 4. A dead zone setting switching means for setting the dead zone at the starting point of the use period and setting the dead zone to a non-set state when a flow rate exceeding a certain flow rate is measured during the use period. The gas meter according to claim 3, further comprising: