JP5150537B2 - Error detection method in gas meter and flow measurement - Google Patents

Description

  The present invention relates to a gas meter or the like installed in a gas supply path and having a function of measuring a gas flow rate, and more particularly to a gas meter or the like that can accurately and efficiently detect an error in the flow rate measurement and improve a safety function.

  Conventionally, a gas meter is installed for the purpose of measuring the flow rate of the gas supplied to the gas user, such as each household. The gas meter is provided in a gas supply pipe to each user and incorporates a gas flow meter for measuring the gas flow rate. The measured gas flow rate is used for calculating the billed gas charge and also for the security function of the gas meter. This safety function shuts off the gas supply or issues an alarm when an abnormal condition occurs, and uses the gas flow meter to detect abnormal conditions such as gas leaks or forgetting to turn off the instrument. Flow measurement is used.

  There are various types of gas flowmeters, such as those using an ultrasonic sensor and those using the thermal conductivity of a gas. Any gas flowmeter has a measurement error due to various factors. Can occur.

  In particular, the measurement characteristics of the gas flow meter may change due to the secular change caused by using the gas flow meter over a long period of time, and the zero point of the gas flow meter may shift. In other words, some flow value other than zero is measured even when there is no flow rate. In such a case, the measurement value when there is a flow rate also includes this deviation, so the measurement is inaccurate. End up.

  Techniques for correcting such a zero point shift are disclosed in Patent Documents 1 and 2 listed below. In the following Patent Document 1, a technique for detecting the deviation of the zero point (hereinafter referred to as an offset) based on the measured flow rate and pressure is proposed, and in the following Patent Document 2, the flow rate in a gas unused state is proposed. It has been proposed to correct on the basis.

  Further, the gas flow in the gas supply pipe may pulsate depending on the surrounding conditions, and this pulsation also affects the measurement accuracy of the gas flow rate. Japanese Patent Application Laid-Open No. 2004-228561 discloses that the occurrence of pulsation is determined and correction processing related to pulsation is performed.

Japanese Patent No. 3888946 JP 2000-111043 A JP 2001-324362 A

  However, the method in Patent Document 1 requires a certain amount of pressure change to detect the zero point offset, and cannot be detected without such pressure change, such as when the gas supply is shut off. There are challenges. In addition, this method requires pressure measurement with the same frequency as the flow rate measurement, which is a more frequent measurement than a general gas meter, and has the problem of increased power consumption and microcomputer load. .

  Moreover, in the method described in Patent Document 2, it is necessary to accurately set the period in which the gas is not used, and the above-described pulsation is not taken into consideration. Therefore, there is a problem that a person is involved in performing the correction, and the correction may be inaccurate.

  In the method described in Patent Document 3, it is assumed that the pulsation is a sine wave. However, considering that the actual pulsation is not a sine wave, it is considered that there is a problem in the accuracy of correction.

  On the other hand, in the safety function against gas leak, even if there is a gas leak, the flow rate is measured less than the actual one, and the zero point offset to the minus side that makes it impossible to recognize it as a gas leak can be detected. is important. Therefore, from the viewpoint of security, it is desired that an error to the minus side of the gas flow meter provided in the gas meter can be detected reliably and accurately.

  Therefore, an object of the present invention is a gas meter that is installed in a gas supply path and has a gas flow rate measuring function, and can accurately and efficiently detect an error in the flow rate measurement and improve the safety function, Etc. is to provide.

  In order to achieve the above object, according to one aspect of the present invention, a gas meter is measured by a flow rate measuring unit that measures an instantaneous flow rate of a gas passing through a gas flow path at a predetermined time interval, and the flow rate measuring unit. There is a case where the calculation means for obtaining the average flow rate of the gas for a predetermined time using the instantaneous flow rate and the average flow rate obtained by the calculation means are compared with a predetermined negative threshold value and the average flow rate is smaller. And an error determination unit that determines that there is an error in the flow rate measurement by the flow rate measurement unit when it occurs more than a predetermined number of times within a predetermined period.

  In order to achieve the above object, another aspect of the present invention is that a gas meter is measured by a flow rate measuring unit that measures an instantaneous flow rate of gas passing through a gas flow path at predetermined time intervals, and the flow rate measuring unit. A calculation means for obtaining an average flow rate of the gas for a predetermined time using the instantaneous flow rate, and a predetermined negative value of an average flow rate obtained by the calculation means that is smaller than the predetermined flow rate, and a predetermined negative threshold value, And an error determination unit that determines that there is an error in the flow rate measurement by the flow rate measurement unit when the average value is smaller.

  Furthermore, in the above invention, a preferable aspect is that the predetermined negative threshold value is detected as a gas leak from a flow rate threshold value that determines that there is a gas leak for a flow rate higher than that value in the gas leak detection performed by the gas meter. It is a value obtained by subtracting the minimum flow rate to be performed.

  Furthermore, in the above-described invention, a preferred aspect is characterized in that the predetermined flow rate is a value equal to or lower than a minimum flow rate when the gas is used downstream of the gas meter.

  In order to achieve the above object, another aspect of the present invention is that a gas meter is measured by a flow rate measuring unit that measures an instantaneous flow rate of gas passing through a gas flow path at predetermined time intervals, and the flow rate measuring unit. A calculating means for obtaining an average flow rate of the gas for a predetermined time using the instantaneous flow rate, and a frequency at which the measured instantaneous flow rate or the obtained average flow rate is a negative value within a predetermined period is a positive value. And an error determination unit that determines that there is an error in the flow rate measurement by the flow rate measurement unit when the frequency is greater than a certain frequency.

  Further, in the above invention, a preferred aspect is that the average flow rate used for determination by the error determination unit is a difference between a maximum value and a minimum value or a standard deviation of the instantaneous flow rate used when obtaining the average flow rate. Is less than or equal to a predetermined value.

  In order to achieve the above object, another aspect of the present invention provides a flow rate measuring unit that measures an instantaneous flow rate of a gas passing through a gas flow path at predetermined time intervals, and an instantaneous flow rate measured by the flow rate measuring unit. In a gas flow measurement error detecting method in a gas meter having a control means for obtaining an average flow rate of the gas for a predetermined time using the control means, the control means compares the obtained average flow rate with a predetermined negative threshold value. When the average flow rate is smaller, it is determined that there is an error in the flow rate measurement by the flow rate measurement means when it occurs more than a predetermined number of times within a predetermined period.

  In order to achieve the above object, still another aspect of the present invention provides a flow rate measuring means for measuring an instantaneous flow rate of gas passing through a gas flow path at a predetermined time interval, and a moment measured by the flow rate measuring means. In a gas meter having a control means for obtaining an average flow rate of the gas for a predetermined time using a flow rate, the control means has a predetermined number of the obtained average flow rate that is smaller than the predetermined flow rate. The average value is compared with a predetermined negative threshold value, and when the average value is smaller, it is determined that there is an error in the flow rate measurement by the flow rate measuring means.

  In order to achieve the above object, another aspect of the present invention provides a flow rate measuring unit that measures an instantaneous flow rate of a gas passing through a gas flow path at predetermined time intervals, and an instantaneous flow rate measured by the flow rate measuring unit. In a gas meter having a control means for obtaining an average flow rate of the gas for a predetermined time using the control means, the control means measures the measured instantaneous flow rate or the obtained average within a predetermined period. When the frequency with a negative flow rate is greater than the frequency with a positive value, it is determined that there is an error in the flow rate measurement by the flow rate measuring means.

  Further objects and features of the present invention will become apparent from the embodiments of the invention described below.

It is a block diagram which concerns on the example of embodiment of the gas meter to which this invention is applied. 3 is a flowchart illustrating an example of a flow rate measurement error detection process performed by a control unit 11; It is a figure for demonstrating the influence of the zero point offset with respect to gas leak detection. It is a figure for demonstrating the measured value in case a flow volume is zero.

  Embodiments of the present invention will be described below with reference to the drawings. However, such an embodiment does not limit the technical scope of the present invention. In the drawings, the same or similar elements are denoted by the same reference numerals or reference symbols.

  FIG. 1 is a configuration diagram according to an embodiment of a gas meter to which the present invention is applied. A gas meter 1 shown in FIG. 1 is a gas meter according to the present embodiment, and a zero point (of the gas flow meter 12 is obtained by using a measured value of a gas flow rate that is constantly obtained by a built-in gas flow meter 12. It is intended to improve the safety function by reliably detecting an offset (shift) to the minus side of the measured value when there is no flow rate.

  As shown in FIG. 1, the gas meter 1 is provided in a gas supply pipe 3 that supplies gas from a gas supply source 2 to a gas supply destination 4 such as a customer's house. The gas supply destination 4 is provided with various gas appliances (for example, a water heater, a stove, a fan heater, etc.), and gas is used as necessary.

  As shown in FIG. 1, the gas meter 1 includes a control unit 11, a gas flow meter 12, a gas cutoff valve 13, a display unit 14, a communication unit 15, and the like. In the gas meter 1, there is a gas flow path for flowing the gas flow from the gas supply pipe 3 on the gas supply source 2 side to the gas supply pipe 3 on the gas supply destination 4 side. Thus, a gas shut-off valve 13 and a gas flow meter 12 are provided.

  The gas shut-off valve 13 is a valve that shuts off the gas supply of the gas flow path according to an instruction from the control unit 11, and operates when an abnormal state is detected, such as when a gas leak is detected.

  The gas flow meter 12 is a flow meter that can detect an instantaneous gas flow rate. For example, an ultrasonic flow meter that measures a flow rate from the propagation time of ultrasonic waves in the fluid, a heater that is placed in the fluid, or the like. A thermal flow sensor that obtains a flow rate using temperature sensors provided on the upstream and downstream sides can be used. Here, as an example, the flow rate is detected every 2 seconds.

  The control unit 11 is a control unit of the gas meter 1, acquires and holds a measurement value of the gas flow rate from the detection result of the gas flow meter 12, and executes an integrated gas amount measurement and safety function. In the safety function, the gas flow rate in the gas supply pipe 3 (gas flow path) is monitored at any time, and measures such as shutting off the gas shut-off valve 13 are detected when an abnormal state such as a gas leak or forgetting to turn off the gas using appliance is detected. Is executed. In addition, in order to correctly execute the security function, the gas meter 1 has a function of detecting an error of the gas flow meter 12, and the gas meter 1 is characterized by this error detection process. The specific contents will be described later.

Note that the control unit 11 can be realized by a so-called microcomputer, and specifically includes a CPU, a ROM, a RAM, and the like, although not shown. And the said function which the control unit 11 performs is performed when the said CPU operate | moves according to the program stored in the said ROM. The ROM stores data necessary for various control processes performed by the control unit 11. The RAM also stores the measured instantaneous gas flow rate Q, the average gas flow rate Q _AVE within a predetermined period (for example, 30 seconds) obtained from the gas flow rate, and the like. Further, the RAM holds a count value used in flow rate measurement error detection (zero point offset detection) described later.

Further, from a functional point of view, the control unit 11 is a gas flow rate measuring means for obtaining a measured value Q of the gas flow rate from the detection result of the gas flow meter 12, and an operation for obtaining the average gas flow rate Q _AVE from the measured value Q. Means, error determination means for detecting an error in the flow rate measurement, and the like.

  The display unit 14 is a part that displays the accumulated gas amount measured by the control unit 11 and a message necessary for the security function to notify the user. The communication unit 15 is a part that manages communication with a monitoring center or the like located remotely, and can receive control of the gas shut-off valve 13 from a remote location via the communication unit 15. Further, when an abnormality is detected by the control unit 11, it can be notified to the monitoring center or the like via the communication unit 15.

  As described above, the gas meter 1 according to the present embodiment having the above-described configuration has an error detection related to the flow rate measurement, specifically, a negative offset occurs at the zero point of the gas flow meter 12. In the following, the specific contents will be described.

FIG. 2 is a flowchart illustrating the procedure of the error detection process performed by the control unit 11. First, when the power of the control unit 11 is turned on, the control unit 11 starts acquiring and holding the gas flow rate value (step S1). Specifically, each instantaneous flow rate value Q is obtained and acquired from the detection result measured every 2 seconds by the gas flow meter 12, and these values are appropriately stored in the RAM. Then, an average flow rate value Q _AVE within a predetermined time (for example, 30 seconds) is calculated from the held instantaneous flow rate value Q, and sequentially stored in the RAM. When the predetermined time for calculating the average flow rate value Q _AVE is 30 seconds, after the start of the processing, 15 instantaneous flow rate values Q every 2 seconds are sequentially held, and then the 15 instantaneous flow rate values Q are The average flow rate value Q _AVE is calculated from the average value and stored. Thereafter, the same processing is repeatedly performed.

  The gas flow value acquired and held in this way is used as appropriate for the above-described measurement of the integrated gas amount and various security functions. For example, if the gas flow rate value of a predetermined value or more is continuously acquired for a predetermined time without changing, it is determined that the gas appliance has been forgotten to be turned off, or the gas flow rate is a small amount and a predetermined threshold value or more. When the gas flow rate value is continuously acquired, processing such as determining that the gas is leaking is performed.

Next, the control unit 11 acquires a gas flow rate value used for determining that a negative offset has occurred at the zero point of the gas flow meter 12 (step S2). The gas flow rate value acquired here is selected and acquired from the acquired and held instantaneous flow rate value Q and average flow rate value Q _{AVE according} to a predetermined condition.

  Thereafter, the control unit 11 uses the acquired gas flow value to determine whether or not the negative offset has occurred (step S3). This determination process (S3) can be performed by several methods, and the acquired gas flow rate value (S2) varies depending on the determination method. Specific contents of each method will be described later.

  If it is determined by the determination process that a negative offset has occurred at the zero point of the gas flow meter 12, the control unit 11 outputs the result of the determination (step S4). Specifically, the fact that the zero point of the gas flow meter 12 is deviated and that the gas flow meter 12 needs to be replaced or adjusted is indicated on the display unit 14 and / or via the communication unit 15. The administrator and / or user of the gas meter 1 is notified through the communication.

  Thus, the error detection process described with reference to FIG. 2 is completed, but the gas meter 1 is replaced by the administrator of the gas meter 1 or the zero point is corrected by the notification, and the flow rate in the gas meter 1 is changed. Measurement accuracy is improved and non-detection of gas leaks is avoided.

  Next, each method of the determination process (S3) described above will be described. There are three methods (the first method, the second method, and the third method). For the first method and the second method, the offset of the zero point to the minus side (absolute value of the deviation) is a predetermined value or more. When it can be inferred that the offset has occurred, the third method determines that the zero point has shifted to the minus side regardless of the magnitude of the offset (deviation). It is determined that an offset has occurred.

  FIG. 3 is a diagram for explaining the influence of the zero point offset on the gas leak detection. In the graph shown in FIG. 3, the horizontal axis represents the elapsed time T, and the vertical axis represents the instantaneous flow rate value Q measured by the gas flow meter 12. The x mark plotted in the graph indicates each measured instantaneous flow rate value Q, and the plot point group indicated by X in the figure shows that no zero point offset occurs in the gas flow meter 12. The case where the correct value is measured is shown. Further, the plot point groups indicated by X1 and X2 in the figure are values measured when the flow rate is the same as that of the plot point group indicated by X, respectively. A case where OS1 and OS2 are generated as offsets is shown.

  A flow rate 3.0 (l / h (liter / hour)) indicated by a solid line in the drawing is an example of a minimum flow rate to be detected as a gas leak, and a flow rate 1.5 (shown by a broken line in the drawing is 1.5). l / h) is an example of a threshold value for determining that there is a gas leak in the gas leak detection process. That is, it is determined that there is a gas leak if the gas flow rate value subjected to the gas leak determination is equal to or greater than the threshold.

  In such a case, the gas flow rate value of the plot point group indicated by X described above exceeds the minimum flow rate that should be detected as the gas leak, and thus needs to be detected as a gas leak. Then, in the case of X1 in which OS1 is generated as a negative offset at the zero point of the gas flow meter 12, the value of OS1 is not so large as shown in FIG. Since the difference DE between the minimum flow rate to be detected and the threshold value for determining the gas leak is smaller than 3.0 (here, 3.0-1.5 = 1.5), in the determination of the gas leak, there is a gas leak. The correct judgment will be made.

  On the other hand, in the case of X2 where OS2 is generated as a negative offset at the zero point of the gas flow meter 12, the value of OS2 is larger than the difference DE between the minimum flow rate and the threshold value, as shown in FIG. In addition, each plot point is located below the broken line, and in the determination of the gas leak, it is not determined that there is a gas leak. Such a situation can be said to be a dangerous situation in which a gas leak to be detected is not detected.

  Therefore, for the purpose of gas leak detection, it is meaningful to detect a case where the offset of the zero point to the minus side is larger than a predetermined value. The first method and the second method are based on this concept.

First, the first method is the above-described average flow rate value Q _AVE , which is a negative value, and whose absolute value is larger than the difference DE between the minimum flow rate and the threshold value related to the gas leak determination, When it occurs for a predetermined number of times (n1 times) within a predetermined period (m months), it is determined that the zero point is shifted to the minus side by a predetermined value or more, that is, it is determined that there is an error in the gas flow meter 12 It is. That is, when the average flow rate value Q _AVE to an average flow rate value Q _{AVE <-DE} is detected more than n1 times during the m months determines that it should correct the zero point of the gas flow meter 12 . For example, when the average flow rate value _{Q AVE} to an average flow rate value _{Q AVE <-1.5 (l / h} ) is detected more than 10 times during 1 month, corrects the zero point of the gas flow meter 12 Judge that it should be.

In this technique, the average flow value Q _AVE held in the RAM is acquired every time in the process of step S2 described above, and the condition of the average flow value Q _AVE <−DE is satisfied in the determination process of step S3 described above. A determination is made whether or not. If the condition is satisfied, the cumulative number of times satisfying the condition is counted up within the predetermined period (m months), and when the value reaches the predetermined number of times (n1 times), zero is reached. It is determined that a negative offset has occurred for the point, and the result of the determination is output (S4). If the predetermined number of times is not reached within the predetermined period, the cumulative number satisfying the above condition is returned to 0, and the process is restarted. Further, the determination is not performed when the predetermined number of times (n1 times) is reached, and it is determined whether the cumulative number is equal to or more than the predetermined number (n1 times) when the predetermined period has elapsed. You may make it determine by.

  In a gas meter having a configuration such as the gas meter 1, the gas flow rate does not constantly become negative at the position of the gas flow meter 12 even if gas leakage or the like is taken into consideration. Therefore, when a negative flow rate that cannot normally be generated repeatedly occurs within a predetermined period, an error relating to the flow rate measurement occurs, that is, the zero point of the gas flow meter 12 is shifted to the negative side. It can be judged. Therefore, it can be said that the first method is an appropriate method for detecting the zero point offset. In the first method, the predetermined period (m months) is long, and the predetermined number of times (n1 times) is a value commensurate with it, so that it is not affected by short-term fluctuations such as the aforementioned pulsation. In addition, a more correct determination can be made. Further, by using the condition based on the difference DE, it is possible to reliably determine that the zero point is shifted to the minus side, and it is possible to detect the above-mentioned dangerous situation on security.

Next, in the second method, the average value of the predetermined number (n2, for example, 100) of the average flow rate value Q _AVE that is smaller than the predetermined value (q (l / h)) is − When it is smaller than DE, it is determined that the zero point is shifted to the minus side by a predetermined value or more. And the value below the minimum usage-amount (minimum flow rate) (for example, 5.0 (l / h)) at the time of use of a gas use instrument is used for the said predetermined value q. Thus, for example, when the q and the minimum flow, the value obtained by dividing 100 total 100 average flow rate value _{Q AVE} to an average flow rate value _Q AVE <5.0 is the case -1.5 smaller, It is determined that the zero point of the gas flow meter 12 should be corrected.

In this method, the average flow rate value Q _AVE held in the RAM is compared with a predetermined value q each time in the process of step S2 described above, and the value is obtained for those smaller than q. Then, in the determination process of step S3 described above, when the obtained average flow rate value Q _AVE reaches n2, the average value is obtained, and if the value is smaller than −DE, the zero point is negative. It is determined that a side offset has occurred, and the result of the determination is output (S4). In the comparison with -DE, when the average value is -DE or more, acquisition of the average flow rate value Q _AVE smaller than q is restarted from the first.

  FIG. 4 is a diagram for explaining a measured value when the flow rate is zero. In general, there is a fluctuation of the measured value in any flow meter, and even in a flow meter with no zero point offset, the measured value when the actual flow rate is zero shifts slightly positive and negative around zero. It is known. FIG. 4 illustrates a frequency distribution of values measured when the actual flow rate is zero, and the solid line indicated by Y1 indicates a case where there is no zero point offset. In this case, the center of the mountain of the frequency distribution is approximately 0, and the frequency decreases as the distance from 0 increases in both positive and negative directions. In this case, the above-described flow rate measurement value with a value smaller than 5.0 (l / h), that is, the flow rate measurement value when there is no flow rate, is described. The average value is approximately 0. If there is a gas leak, in the configuration of the gas meter 1, this average value in the gas flow meter 12 is considered to be a positive value.

  On the other hand, the frequency distribution indicated by Y2 in FIG. 4 is an example of the case where the zero point of the flow meter is shifted to the minus side. Also in this case, it is considered that the average value measured when the actual flow rate is zero is approximately the center value of the mountain of the frequency distribution. The value can be considered as the value of the offset of the zero point. Therefore, in the example shown in FIG. 4, it can be seen that an offset of 1.5 (l / h) or more occurs on the minus side.

  Therefore, it can be said that the second method is an appropriate method for detecting the zero point offset. Also, in the second method, by taking a large number (n2), it is possible to make a correct determination without being affected by short-term fluctuations such as the occurrence of a negative flow rate due to the pulsation or temperature change described above. Further, by using the condition based on the difference DE, it is possible to reliably determine that the zero point is shifted to the minus side, and it is possible to detect the above-mentioned dangerous situation on security.

Next, the third method determines that the zero point is shifted to the minus side when the frequency (number) of the negative flow rate measurement value is larger than the frequency (number) of the positive flow rate measurement value. . Here, as the flow rate measurement value, the instantaneous flow rate value Q or the average flow rate value Q _AVE described above is used. Moreover, the period which takes the said frequency can be made into 1 to 2 months.

In this method, in the process of step S2, the positive or negative of the instantaneous flow rate value Q or the average flow rate value Q _AVE held in the RAM is determined every time. If the value is negative, the negative cumulative frequency is calculated. Count up, and if it is positive, count up the positive cumulative frequency and obtain the cumulative frequency. In the determination process in step S3 described above, at a predetermined timing, for example, when one month has elapsed since the accumulation of the frequency is started, the negative cumulative frequency is compared with the positive cumulative frequency, If the negative cumulative frequency is larger, it is determined that a negative offset has occurred at the zero point, and the result of the determination is output (S4). If it is not determined that the negative cumulative frequency is larger, both cumulative frequencies are returned to 0 and the process is resumed.

  As described above, in the configuration of the gas meter 1, a negative flow rate does not occur at the position of the gas flow meter 12, and when the gas appliance is used at the gas supply destination 4, the gas flow rate is naturally increased. Considering the fact that the zero point is not deviated as described with reference to FIG. 4, the frequency of the measured value when the gas is not used is approximately the same in both positive and negative directions. If it is not shifted to the minus side, the above-mentioned positive cumulative frequency is larger than the negative cumulative frequency. Therefore, when the negative cumulative frequency becomes larger, it can be determined that the zero point is shifted to the negative side, and it can be said that the third method is an appropriate method for detecting the zero point offset.

  Also in this third method, by taking a long period for taking the above-mentioned frequency, it is possible to make a correct determination without being affected by short-term fluctuations such as the occurrence of a negative flow rate due to the pulsation or temperature change described above. . Further, in the third method, there is a possibility of detecting that there is an offset even when the offset of the zero point to the minus side is small. In particular, in the environment where the usage time of the gas appliance is short, such a possibility is high. In this sense, it can be said that the method is more sensitive in terms of offset detection than the first method and the second method described above.

  In an environment where the gas appliance is used for a long time, the sensitivity detected by the third method may be low or may not be detected. In such an environment, the measured flow rate value is a predetermined value. You may make it take frequency about the thing (for example, 5.0 (l / h)) or less.

  Although the first method, the second method, and the third method have been described above, these may be used alone or in combination. When combining, a combination of the first method and the third method and a combination of the second method and the third method are desirable. In these combinations, first, it is detected that there is a negative offset by the third method, and then, it is determined whether the offset is a predetermined value or more by the first method or the second method. It is desirable to determine whether the offset is large enough to be a security risk.

Further, in these determinations, in order to further suppress the above-described adverse effects of pulsation, further limiting conditions may be provided for the gas flow rate value (average flow rate value Q _AVE ) used for the determination. The limiting condition (1) is that the difference between the maximum value and the minimum value of the instantaneous flow rate value Q used for _obtaining the average flow rate value Q _AVE is not more than a certain value. The limiting condition (2) is that the standard deviation of the instantaneous flow rate value Q used for _obtaining the average flow rate value Q _AVE is not more than a certain value. Further, the limiting condition (3) does not include the instantaneous flow rate value Q when the gas flow rate is measured in the pulsation mode in the instantaneous flow rate value Q used for _obtaining the average flow rate value Q _AVE. That is. Note that the pulsation mode is a mode in which the measurement frequency of the gas flow rate is increased in order to detect pulsation when it is found that pulsation may occur due to some factor. This limiting condition (3) is used when is adopted. These limiting conditions (1) to (3) may be applied singly or in combination.

Further, in the third method, the zero point offset detection is more easily performed by using only the gas flow rate value when there is no actual flow rate. A further limiting condition may be provided for the flow rate value (average flow rate value Q _AVE ). The limiting condition (4) is that the maximum value of the instantaneous flow rate value Q used for _obtaining the average flow rate value Q _AVE is not more than a certain value. The limiting condition (5) is that the value of the average flow value Q _AVE obtained and held _immediately before the average flow value Q _AVE is equal to or less than a predetermined value. Further, the limiting condition (6) is that the maximum value of the instantaneous flow rate value Q used for _obtaining the average flow rate value Q _AVE obtained and held _immediately before the average flow rate value Q _AVE is not more than a certain value. That is. These limiting conditions (4) to (6) may be applied singly or in combination. Further, these limiting conditions (4) to (6) may be applied to the second method.

As described above, in the gas meter 1 according to the present embodiment, there is an error in the gas flow meter 12 using the instantaneous flow rate value Q and the average flow rate value Q _AVE that are constantly acquired and held, that is, The offset of the zero point of the gas flow meter 12 can be detected, no new measurement is required for this purpose, and the determination process is relatively easy, so that the power cost An increase in microcomputer load can be suppressed. In particular, in the third method, the process for determination can be easily performed.

  Moreover, the accurate offset determination which excluded the influence of the short-term flow volume fluctuation | variation is possible by determination by each method mentioned above.

  Also, as described above, in an environment where the flow rate can hardly be negative, an offset to the negative side is detected, so it is possible to reliably detect the offset, and to detect the negative side offset, Since replacement or adjustment of the gas flow meter 12 is urged, undetected at the time of gas leakage can be prevented, and the security function can be improved.

  In the first method and the second method, replacement or adjustment of the gas flow meter 12 is urged in the case of an offset that is dangerous from the viewpoint of gas leakage detection, which is suitable for both safety and convenience. It is possible to take corrective action.

  The protection scope of the present invention is not limited to the above-described embodiment, but covers the invention described in the claims and equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 Gas meter, 2 Gas supply source, 3 Gas supply pipe, 4 Gas supply destination, 11 Control unit (flow rate measurement means, calculation means, error determination means, control means), 12 Gas flow meter (flow rate measurement means), 13 Gas shut off Valve, 14 Display, 15 Communication

Claims (9)

A flow rate measuring means for measuring an instantaneous flow rate of the gas passing through the gas flow path at predetermined time intervals;
A calculation means for obtaining an average flow rate of the gas for a predetermined time using the instantaneous flow rate measured by the flow rate measurement means;
When the average flow rate obtained by the calculation means is compared with a predetermined negative threshold value and the average flow rate is smaller, the flow rate measurement by the flow rate measurement means occurs when a predetermined number of times occurs within a predetermined period. An error determination means for determining that there is an error in the gas meter. A flow rate measuring means for measuring an instantaneous flow rate of the gas passing through the gas flow path at predetermined time intervals;
A calculation means for obtaining an average flow rate of the gas for a predetermined time using the instantaneous flow rate measured by the flow rate measurement means;
When the average flow rate obtained by the calculation means is smaller than the predetermined flow rate but a predetermined average value is compared with a predetermined negative threshold, the average value is smaller, and the flow rate measurement means is used for flow rate measurement. An error determination means for determining that there is an error. In claim 1 or claim 2,
The predetermined negative threshold is:
In the gas leak detection performed by the gas meter, the gas meter is a value obtained by subtracting a minimum flow rate to be detected as a gas leak from a flow rate threshold value for determining that there is a gas leak for a flow rate higher than that value. In claim 2,
The predetermined flow rate is a value equal to or lower than a minimum flow rate when the gas is used downstream of the gas meter. A flow rate measuring means for measuring an instantaneous flow rate of the gas passing through the gas flow path at predetermined time intervals;
A calculation means for obtaining an average flow rate of the gas for a predetermined time using the instantaneous flow rate measured by the flow rate measurement means;
If the frequency at which the measured instantaneous flow rate or the obtained average flow rate is a negative value is larger than the positive value within a predetermined period, there is an error in the flow rate measurement by the flow rate measuring means. And an error determination means for determining the gas meter. In any one of Claims 1 to 5,
The average flow rate used for the determination by the error determination means is characterized in that the difference or standard deviation between the maximum value and the minimum value of the instantaneous flow rate used when determining the average flow rate is a predetermined value or less. And gas meter. A flow rate measuring means for measuring an instantaneous flow rate of the gas passing through the gas flow path at predetermined time intervals, and a control means for obtaining an average flow rate of the gas for a predetermined time using the instantaneous flow rate measured by the flow rate measuring means. An error detection method of flow measurement in a gas meter having
When the control means compares the determined average flow rate with a predetermined negative threshold value and the average flow rate is smaller than a predetermined number of times within a predetermined period, the flow rate by the flow rate measurement means An error detection method for flow measurement, characterized by determining that there is an error in measurement. A flow rate measuring means for measuring an instantaneous flow rate of the gas passing through the gas flow path at predetermined time intervals, and a control means for obtaining an average flow rate of the gas for a predetermined time using the instantaneous flow rate measured by the flow rate measuring means. An error detection method of flow measurement in a gas meter having
The control means compares the predetermined average value of the obtained average flow rate which is smaller than the predetermined flow rate with a predetermined negative threshold value, and when the average value is smaller, the flow rate measurement by the flow rate measurement means An error detection method for flow measurement, characterized in that it is determined that there is an error. A flow rate measuring means for measuring an instantaneous flow rate of the gas passing through the gas flow path at predetermined time intervals, and a control means for obtaining an average flow rate of the gas for a predetermined time using the instantaneous flow rate measured by the flow rate measuring means. An error detection method of flow measurement in a gas meter having
When the frequency at which the measured instantaneous flow rate or the obtained average flow rate is a negative value is larger than the frequency at a positive value within a predetermined period, the control unit measures the flow rate by the flow rate measurement unit. An error detection method for flow measurement, characterized in that it is determined that there is an error.

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