JP4117996B2 - Gas meter flow derivation method and gas meter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gas meter for deriving an integrated flow rate within a fixed integration time from an instantaneous flow rate measured discretely.
[0002]
[Prior art]
Conventionally, as a flow meter used for a gas meter, a membrane type is the mainstream, but due to its convenience, there are currently meters using an ultrasonic wave and a meter using a heat conduction type flow sensor. Proposed.
In such a meter, from the measurement principle, the flow rate taken in is an instantaneous flow rate obtained discretely in time, and the data string is a discrete type. From a plurality of instantaneous flow rates taken in this way, an integrated flow rate within a certain integrated time is obtained by a predetermined method.
[0003]
On the other hand, for safety reasons, the gas meter detects an excessive flow rate and shuts off the gas by detecting an instantaneous excessive flow rate, and whether there is continuous leakage of gas for a certain period (usually about 30 days). It has several safety functions such as a leak monitoring function that detects and issues an alarm.
Conventionally, the integrated flow rate has been employed as it is as a flow rate for determining whether or not such a safety function is to be used.
[0004]
[Problems to be solved by the invention]
When trying to adopt a new measurement method as described above, there are the following problems.
That is, in the case of a gas meter such as an ultrasonic meter that derives the integrated flow rate in a certain time from the discretely measured instantaneous flow rate, the comparison used for determining the instantaneous flow rate or the safety function due to the pulsation of the gas, etc. Fluctuation occurs in the integrated flow rate for a short time (several tens of seconds to 1 hour).
If the safety function is activated based on the integrated flow rate including the fluctuation, an inappropriate case may occur. For example, in the overflow detection function, a change in instantaneous flow rate due to pulsation is misrecognized as an overflow, and unnecessary blocking is repeated.
This technical problem is particularly noticeable in deriving an integrated flow rate within a fixed time from instantaneous flow rates measured discretely.
Conventionally, this did not become a problem because even if the integrated flow rate is the object of judgment as it is, in the case of a membrane type, the measured flow rate was a flow rate averaged in the time domain, This is probably because the problem of fluctuation was absorbed.
[0005]
An object of the present invention is to provide a gas meter flow rate deriving method capable of solving the above-mentioned problems in a gas meter that derives an integrated flow rate within a predetermined time from discretely measured instantaneous flow rates. The object is to obtain a gas meter capable of solving such problems.
[0006]
[Means for Solving the Problems]
In order to achieve this object, the characteristic means of the flow rate deriving method according to the present invention derives the integrated flow rate within a predetermined integration time from the instantaneous flow rate measured discretely as described in claim 1. In the gas meter,
For a plurality of instantaneous flow rates measured within the integration time,
One or both functions of the first statistical function representing the variation of the plurality of instantaneous flow rates and the second statistical function that is the difference between the continuous instantaneous flow rates or the statistical function of the change amount of the instantaneous flow rate per unit time Find the error function
The flow of the safety function for the safety function in the gas meter is derived based on the obtained error function and the separately obtained integrated flow rate.
[0007]
A gas meter using this method, as described in claim 5,
A gas meter provided with an integrated flow rate deriving means for deriving an integrated flow rate within a predetermined integrated time from an instantaneous flow rate measured in a discrete manner,
First statistical function derivation means for obtaining a first statistical function representing variation of the plurality of instantaneous flow rates from a plurality of instantaneous flow rates measured within the integration time;
Second statistical function derivation means for obtaining a second statistical function which is a statistical function of a difference between the continuous instantaneous flow rates or a change amount of the instantaneous flow rate per unit time with respect to a plurality of instantaneous flow rates measured within the predetermined integration time. And
Error function deriving means for obtaining an error function that is one or both of the first statistical function obtained by the first statistical function deriving means and the second statistical function obtained by the second statistical function deriving means ,
Comprising a safety function flow deriving means for obtaining a safety function flow for a safety function based on the error function obtained by the error function deriving means and the accumulated flow obtained by the accumulated flow deriving means. Can do.
[0008]
In this configuration, the first statistical function is a function representing the variation of the instantaneous flow rate group within the accumulated time, and the second statistical function is a statistical function of the difference between the instantaneous flow rates within the accumulated time or the change amount per unit time. Therefore, the error function obtained from these functions is a value representative of the dispersion of data measured discretely. For example, if the measured instantaneous flow rate includes a flow rate change component related to pulsation, the statistical function also includes fluctuation due to pulsation and reflects this.
On the other hand, the integrated flow rate can be regarded as a flow rate when an average instantaneous flow rate flows within this integration time.
[0009]
From the viewpoint of safety functions, for example, when considering an overflow cutoff, it is preferable to perform the cutoff based on a true flow rate that is not affected by pulsation. Therefore, in the present application, it is assumed that the error function described above represents the degree of pulsation and the like, and processing such as removing the influence or maximizing the effect is performed.
That is, in accordance with a predetermined procedure, a safety function flow rate suitable for the safety function is obtained by combining the integrated flow rate and an error function representative of this variation to derive a safety function flow rate suitable for the safety function. Can do.
The flow rate for the safety function can be the flow rate for determining whether or not the safety function is to be operated, so that the safety function can be appropriately performed.
[0010]
In the derivation method according to claim 1, as described in claim 2, the flow rate for the safety function in the gas meter is derived based on the obtained error function and the separately obtained integrated flow rate. It is preferable to derive the safety function flow rate by adding both or subtracting the former from the latter.
This configuration will be described with reference to FIG. The horizontal axis in FIG. 2 indicates time, and the vertical axis indicates the flow rate (the same in FIG. 3). In the figure, the periodic flow signal drawn along the horizontal axis indicates the pulsation component included in the actually measured flow rate (shown by the solid line). Accordingly, the flow rate at the base is in a state indicated by a thin solid line. Now, each instantaneous flow rate discretely measured in a predetermined state is indicated by discrete points with respect to the actual flow rate. Now, on the right side of the figure, the standard deviation σ as the first statistical function is representatively shown.
[0011]
As can be seen from this figure, the instantaneous flow rate group that is actually measured has a simple error because it can be considered that the average instantaneous flow rate has flown within the integration time and the flow rate is a variation. By adding and subtracting functions, the flow rate in the state excluding the variation can be obtained.
Here, when subtraction is performed, the flow rate is viewed on the base side, and for example, a blocking operation can be performed while capturing a certain change tendency of the flow rate of the base.
On the contrary, when performing addition, monitoring omission etc. can be reliably eliminated when safety is a problem in a minute flow rate range.
[0012]
In the present application, the integration time, the period of pulsation, and the unit time when the change amount of the instantaneous flow rate is taken are not defined. That is, various relational situations occur, but at the same time, there are various causes of fluctuations in the flow rate measured by the gas meter. For example, as explained so far, there may be pulsation at the inlet pipe branch upstream from the gas meter, and even if the gas equipment provided downstream from the gas meter is operated or stopped, the flow rate Changes occur. Here, the flow rate change in the former case has periodicity, but the latter case is usually temporary. Therefore, it may be preferable to obtain a variation representative value in consideration of these factors, and it is preferable to employ various representative values as described below.
[0013]
As described in claim 3, a standard deviation of a plurality of instantaneous flow rates can be adopted as the first statistical function.
The standard deviation is the most general index when the variation is observed, and when the variation is in a normal distribution state, it becomes possible to satisfactorily specify the limit point of the distribution. In the case of this example, a preferable statistical function is given when pulsation is the main variation factor. Such a function is simple and effective without imposing a burden on the CPU of the gas meter.
[0014]
On the other hand, as the second statistical function, as described in claim 4, the second statistical function is obtained from a number sequence consisting of a difference between successive instantaneous flow rates or a number sequence consisting of an absolute value of a change amount of the instantaneous flow rate per unit time. Statistical functions can also be employed.
Based on such difference or fluctuation amount, data indicating the degree of variation can be obtained by a simple calculation, and the load on the CPU can be reduced.
If there is a gas device that is intermittently driven at a relatively high frequency, such as a floor heating water heater with an ON / OFF type heat retention function, on the downstream side of the gas meter, the operation of these devices can be controlled according to the appropriate setting of the integration time. By distinguishing from the influence of pulsation, an appropriate variation index can be obtained according to the situation. Furthermore, in this case, the distinction from pulsation becomes clear by shortening the integration time.
That is, the intermittent drive type gas device gives flow fluctuations only for a short time at the moment of ON / OFF, but always gives fluctuations in the case of pulsation, so both can be easily identified. By appropriately extracting the ON / OFF of the device, the flow rate for the safety function can be appropriately set in accordance with this situation.
[0015]
Furthermore, as described in claim 4, it is also a preferable aspect to employ an average value of absolute values of differences between successive instantaneous flow rates as the second statistical function.
Even when such an average value is used, evaluation can be performed in a state in which variations in measured values are averaged.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present application will be described with reference to FIG.
The gas meter 1 includes a measuring tube 2 for obtaining information on a predetermined flow using ultrasonic waves, a system for obtaining an instantaneous flow rate based on information from the measurement tube 2 and an obtained instantaneous flow rate. The system for determining the flow rate for the safety function referred to in the present application is provided.
That is, the gas meter 1 includes the above-described measurement tube 2 and a meter main body 7 to which the output end 2a of the measurement tube 2 is connected. The processing system is stored as various means.
[0017]
In the measurement tube 2, the measurement target gas f flows from the introduction unit 3 into the measurement tube 2 and is discharged from the lead-out unit 4. In the figure, the flow direction of the gas f in the measuring tube 2 is from left to right in the figure as indicated by a large arrow. The left side is the upstream side, and the right side is the downstream side.
The measurement tube 2 is provided with a pair of transducers 5 provided to be positioned in a predetermined direction with respect to the measurement tube 2. The separation distance L of these transducers 5 is constant.
Each of the transmitters / receivers 5 includes an ultrasonic transmitter / receiver 5a and a receiver 5b, and in accordance with a command from the main body side, the transmitter / receiver 5a on one side transmits ultrasonic waves from one side to the other. The receiving device 5b on the other side receives the ultrasonic wave transmitted at a predetermined timing from the one side, and thereby the propagation time of the ultrasonic wave (transmitting on the one side) The time difference between the transmission timing in the receiver 5a and the reception timing in the other receiver 5b) can be determined.
This operation can be similarly performed with respect to the transmitter 5a and the receiver 5b that are in a positional relationship reversed with respect to the flow direction, and in both the forward direction and the reverse direction along the flow direction, A configuration is employed in which sound waves are propagated and the propagation time of each ultrasonic wave can be obtained.
[0018]
In the above structure, the propagation time is measured by transmitting the ultrasonic wave in the forward direction in which the sound propagation direction is along the flow, and in the forward direction, the ultrasonic wave propagates between the transducers. The operation for obtaining the time t10 and the operation for obtaining the reverse propagation time t20 in which the ultrasonic wave propagates between the transducers in the reverse direction, which is the direction opposite to the flow, are obtained as a pair. It is executed by the measuring means 6.
[0019]
The instantaneous flow rate measuring means 6 obtains and measures the gas flow velocity Vx (this is the flow velocity component along the ultrasonic propagation direction) based on the forward propagation time t10 and the backward propagation time t20 that are output. A single flow rate is obtained in consideration of the cross-sectional area S1 of the part and the flow coefficient β of the measurement part.
The flow velocity Vx and the instantaneous flow rate Q are given by the following equations.
[0020]
[Expression 1]
Vx = L × (1 / t10−1 / t20) / 2
Q = Vx × S1 × β × cos (θ)
[0021]
The instantaneous flow rate Q is a value that can be obtained by a single measurement, and is measured discretely. The measurement timing of the instantaneous flow rate is individually given by the measurement time control means 8 provided with the clock 8a.
The operation of the measurement 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 individual measurement timing commands, but the setting of the mutual measurement timing is also controlled by this means 8. This control is executed by adopting the following sequence.
The integration time T is set in advance as an appropriate constant value such as several tens of minutes to several hours in consideration of the usage of the gas meter. Further, the number of measurement timings (sampling number n) within the integrated time T is also set to 100 to 30000 in relation to the purpose of use and the like. Therefore, the reference sampling interval is about 1 second.
Now, each measurement timing is the time required for one measurement in which the integrated time is T, and the forward and reverse directions by ultrasonic waves are a pair (this measurement required time is not only the time required for measurement, It is set based on the following equation, where Δt is a prohibition time not included in the next measurement that occurs due to balance with other computations in the CPU, etc., and N is a random number generated every time the measurement timing is set.
That is, the time from one measurement timing to the next timing is as follows.
[0022]
[Expression 2]
Δt + (T / n−Δt) × N / {(1 + Nmax) / 2}
Here, the random number N is a random number generated in the range of an integer from 1 to Nmax, and the probability that each number is generated is the same.
This sequence is repeated sequentially.
[0023]
In this way, by setting the measurement timing, the number of samplings n within the integration time T can be statistically ensured, and by varying the timing, the probability of occurrence of errors due to logical resonance is greatly reduced. be able to.
In FIGS. 2 and 3, the measured value of the instantaneous flow rate is shown as each point on the analog flow rate line described as the actual flow rate.
[0024]
In this way, a plurality of instantaneous flow rates Q within a predetermined integration time T are obtained. Hereinafter, the characteristic constituent parts of the present application will be described. This part is a part for obtaining the safety function flow Qsa from the instantaneous flow Q described above.
[0025]
In this part, a first statistical function deriving means 9 for obtaining a first statistical function representing a variation in a plurality of instantaneous flow rates Q from a plurality of instantaneous flow rates Q measured within the accumulated time T;
Second statistical function deriving means 10 for obtaining a second statistical function that is a statistical function of a difference between successive instantaneous flow rates with respect to a plurality of instantaneous flow rates Q measured within the integration time T is provided.
Then, an error function deriving unit that obtains an error function that is one or both of the first statistical function obtained by the first statistical function deriving unit 9 and the second statistical function obtained by the second statistical function deriving unit 10. 11 is provided.
Furthermore, a safety function flow rate deriving unit 13 for obtaining a safety function flow rate for the safety function based on the error function obtained by the error function deriving unit 11 and the accumulated flow rate obtained by the integrated flow rate deriving unit 12 is provided. .
The safety function flow rate obtained by the safety function flow rate derivation means 13 is sent to the safety operation means 14 and is used for determining whether the pipeline (not shown) provided with the gas meter 1 is shut off. In such a case, the pipeline is blocked.
[0026]
Hereinafter, the individual means shown in FIG. 1 will be described.
Integrated flow derivation means 14
From the instantaneous flow rate measuring means 6, an integrated flow rate Qsum is derived as a product of the average of the instantaneous flow rates Q inputted within the integrated time and the integrated time. This integrated flow rate Qsum is sent to the flow rate deriving means 13 for safety function.
B First statistic deriving means 9
A standard deviation σ of the instantaneous flow rate Q inputted 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
From the instantaneous flow rate measuring means 6, the average dm of the absolute value of the difference between the continuous instantaneous flow rates Q inputted within the integration time is derived. The average dm of the difference is sent to the error function deriving unit 11.
D Flow rate deriving means 13 for safety functions
Using the 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 in the error function deriving means 11 for the input integrated flow rate Qsum, In response to this, addition / subtraction is performed to obtain the safety function flow Qsa.
This safety function flow rate can be expressed as follows.
[0027]
[Equation 3]
Qsa = Qsum + a1 × σ + a2 × dm
Here, a1 and a2 are constants set in advance based on the accumulated time T or the like and the type of variation index.
[0028]
For example, when (−2, 0) is adopted as (a1, a2), 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 set to (2, 0). Gives the flow rate for the safety function on the higher side (indicated by a short dashed line).
By adopting such a low-order safety function flow rate, approximately 90% of malfunctions due to pulsation can be prevented.
Further, (0, -dm / sqrt (n)) may be used as (a1, a2). In this case, the same effect as described above can be obtained. Moreover, in this method, the determination time can be shortened.
[0029]
It is possible to adopt combinations of numbers that are mutually effective as (a1, a2). For example, the integrated time is divided into finer times, and the standard deviation and the average of the differences within the divided time are divided. The above combination may be changed by determining the relationship between the pulsation and the ON / OFF state of the device.
Further, in relation to the relationship between the pulsation cycle and the average measurement interval, in the situation shown in FIG. 2 where the pulsation cycle is smaller than the average measurement interval, the instantaneous flow rate is measured almost randomly with respect to the pulsation phase. Therefore, since the average of the absolute value of the difference is proportional to the pulsation amplitude, the method of taking a multiple of this average value is valid.
On the other hand, in the situation shown in FIG. 3 where the pulsation period is larger than the average measurement interval, there is no significant difference between the standard deviation indicating the degree of variation and the average.
Therefore, the average multiple of the absolute value of the difference is one function that can be easily and usefully selected and used in the structure of the present application.
[0030]
E Safe operation means 14
The safe operation means 14 performs operations such as blocking the flow path and generating an alarm based on the flow rate derived by the safety function flow rate deriving means 13.
The main operation of this means is as follows.
Ho 1 Total flow cut-off This is a cut-off after a maximum of 60 seconds when an abnormally large flow flows on the downstream side of the meter, such as when the gas plug is accidentally opened or the rubber pipe is disconnected.
When the safety function flow rate Qsa of the present application is used for this function, it is preferable to make the determination based on the lower safety function flow rate for reasons such as eliminating the influence of pulsation.
Ho 2 Individual flow rate cutoff This is to shut off after about 60 seconds when the flow rate set for each meter number flows.
When the safety function flow rate Qsa of the present application is used for this function, it is preferable to make the determination based on the lower safety function flow rate as described above, for reasons such as eliminating the influence of pulsation. .
Ho 3 Leakage Detection Alarm A leakage detection alarm for detecting minute leaks in a room is triggered when the flow rate does not fall below the specified flow rate (3 to 5 liters / h) for 30 consecutive days.
However, when using the Qsa of the present application, it is determined that the flow rate is lower than the specified flow rate due to a negative error, and the above-mentioned safety function flow rate is not set so that the alarm does not become normal by resetting the count for 30 days. It is preferable to make a judgment at
[0031]
The above is the means related to the main configuration of the present application. As shown in FIG. 1, the apparatus is provided with the used flow rate deriving means 15, and the used flow rate deriving means 15 outputs the actual flow rate. It is configured to be. This output value is sent to the use flow rate output means 16 which is a general output device (counter, printer, etc.) so that the amount of gas used can be confirmed.
Here, the used flow rate deriving means 15 obtains a used flow rate within a predetermined period from the accumulated flow rate Qsum obtained within the aforementioned accumulated time.
[0032]
[Another embodiment]
(1) In the above-described embodiment, an example of performing flow rate measurement using ultrasonic waves has been described as an example. However, a heat conduction type flow rate sensor may be used to obtain an integrated flow rate from discretely measured instantaneous flow rates. In addition to the main part of the flow rate measurement, there is an electromagnetic type or the like, and the present application is applicable to all of them.
(2) In the above embodiment, the error function is defined for the integrated flow rate. However, the error function of the present application is obtained from a plurality of instantaneous flow rates obtained after the integration time has elapsed. It is conceivable that the function corresponding to is obtained for the instantaneous flow rate individually, and based on this, the instantaneous flow rate itself is individually subjected to error correction processing. However, when this method is used, the instantaneous flow rate is corrected and the correction is performed. Since it is necessary to take a detour procedure of deriving the flow rate from the subsequent value, and finally it is necessary to obtain the flow rate for the safety function with respect to the integrated flow rate, it is considered that they are substantially equivalent.
(3) In the above embodiment, the standard deviation is adopted as the first statistical function, but dispersion or the like may be adopted as the statistical function representing the variation in the integrated flow rate.
(4) In the above embodiment, as the second statistical function, the average value of the absolute value of the difference between the continuous instantaneous flow rates is adopted, but the average value of the difference between the instantaneous flow rates measured continuously, etc. The statistical function may be the second statistical function, and the statistical function such as the average value of the change amount of the instantaneous flow rate per unit time (for example, 1 sec) may be the second statistical function. Furthermore, in addition to the function corresponding to the first time derivative of the flow rate, a function corresponding to the second derivative and the like can be employed.
(5) In the above embodiment, the flow rate for the safety function is obtained by linearly connecting the integrated flow rate and the error function. However, the integrated flow rate is adjusted according to the value of the error function. On the other hand, a flow rate at a certain ratio may be used as the flow rate for the safety function. That is, the safety function flow rate can be determined from the integrated flow rate and the error function.
[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.
DESCRIPTION OF SYMBOLS 1 Gas meter 2 Measuring tube 3 Introducing part 4 Deriving part 5 Transmitter / receiver 5a Transmitter 5b Receiver 6 Instantaneous flow rate measuring means 7 Meter body 8 Measuring time control means 9 First statistical function deriving means 10 Second statistical function deriving means 11 Error function deriving means 12 Integrated flow deriving means 13 Safety function flow deriving means 14 Safe operation means 15 Used flow deriving means 16 Used flow output means

Claims (5)

In a gas meter that derives the integrated flow rate within a certain integration time from the instantaneous flow rate measured in a discrete manner,
For a plurality of instantaneous flow rates measured within the integration time,
One or both of the functions of the first statistical function representing the variation of the plurality of instantaneous flow rates and the second statistical function that is the difference between the continuous instantaneous flow rates or the statistical function of the change amount of the instantaneous flow rate per unit time. Find the error function
A gas meter flow rate derivation method for deriving a safety function flow rate for a safety function in a gas meter based on the obtained error function and a separately obtained integrated flow rate. In order to derive the flow rate for the safety function in the gas meter based on the obtained error function and the separately obtained integrated flow rate,
The method for deriving a flow rate of a gas meter according to claim 1, wherein the flow rate for safety function is derived by adding both or subtracting the former from the latter. The gas meter flow rate derivation method according to claim 1, wherein the first statistical function is a standard deviation of the plurality of instantaneous flow rates. The second statistical function is a statistical function obtained from a sequence consisting of a difference between successive instantaneous flow rates, or a sequence consisting of an absolute value of a change in instantaneous flow rate per unit time, or
The method for deriving a flow rate of a gas meter according to claim 1 or 2, wherein the second statistical function is an average value of absolute values of differences between successive instantaneous flow rates. A gas meter provided with an integrated flow rate deriving means for deriving an integrated flow rate within a predetermined integrated time from an instantaneous flow rate measured in a discrete manner,
First statistical function derivation means for obtaining a first statistical function representing variation of the plurality of instantaneous flow rates from a plurality of instantaneous flow rates measured within the integration time;
Second statistical function derivation means for obtaining a second statistical function which is a statistical function of a difference between the continuous instantaneous flow rates or a change amount of the instantaneous flow rate per unit time with respect to a plurality of instantaneous flow rates measured within the predetermined integration time. And
Error function deriving means for obtaining an error function that is one or both of the first statistical function obtained by the first statistical function deriving means and the second statistical function obtained by the second statistical function deriving means ,
A gas meter comprising safety function flow deriving means for obtaining a safety function flow for a safety function based on the error function obtained by the error function deriving means and the integrated flow obtained by the integrated flow deriving means.

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