JP2005233437A - Device and method for detecting abnormal pressure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and a method for detecting abnormal pressure capable of accurately detecting the abnormal lowering of a pressure without deviating the measurement of the pulsation of a fluid to a high or low level side even when the pulsation occurs in the fluid to be measured. <P>SOLUTION: This device for detecting the abnormal pressure comprises a pressure sensor 301 measuring the pressure of a gas, control part 306 and a pressure value calculation part 303 controlling the measurement by the pressure sensor 301 so as to measure the pressure at a non-constant frequency over the predetermined number of times, and a pressure lowering abnormality determination part 304 determining that a pressure lowering abnormality occurs when the number of measurement of pressure below a predetermined threshold value is equal to or higher than the number of times NL-th, a predetermined threshold value, as the result of the pressure measurement over the specified number of times. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pressure abnormality detection device and a pressure abnormality detection method for detecting the occurrence of pressure abnormality in a fluid to be measured such as city gas in a flow rate measurement device such as a gas meter.

  In a so-called gas meter that measures the flow rate of city gas, when the gas pressure falls below a predetermined threshold pressure such as about 0.83 [kPa] (85 [mmH2 O]), the shut-off valve is closed and the downstream side ( The gas supply to the user side) is stopped. For example, when a dangerous state such as gas leakage occurs in a pipe on the downstream side of a gas meter or a gas consuming device used by a user, the gas pressure in the gas meter is often clearly abnormally low. Therefore, when an abnormal gas pressure drop is detected, the shutoff valve is closed to shut off the gas supply from the gas meter to the downstream side.

  More specifically, in an NI meter equipped with a pressure sensor that outputs an electric signal or an optical signal corresponding to the gas pressure, the normal monitoring mode is always performed every 10 seconds (at a measurement frequency of 0.1 [Hz]). ) Measuring pressure with a pressure sensor.

  When the measured pressure value becomes equal to or lower than a predetermined threshold pressure such as about 0.83 [kPa], the measurement frequency (measurement cycle) is accelerated to 0.125 seconds (8 Hz) for 3 seconds. Continue the pressure monitoring mode (pressure monitoring state) for a total of 25 times. At this time, (1) When the flow rate is detected within 4 minutes until that time (gas flow is present), or (2) When the flow rate is detected during pressure drop (in pressure monitoring mode) Since there is a high risk that a pressure drop abnormality due to gas leakage or the like has occurred, the shutoff valve built in the gas meter is closed to stop the gas supply to the user side (downstream side of the gas meter). However, if a pressure exceeding a predetermined threshold pressure is measured even once during the pressure monitoring mode, it is not determined that a pressure drop abnormality has occurred, and the normal monitoring mode is resumed. Measure pressure every second.

  In an NB meter equipped with a mechanical pressure drop detection device (hereinafter also referred to as a pressure switch) that is a combination of a diaphragm and a contact-type switch linked to the diaphragm, the measured gas pressure value is about 0.29 [kPa]. ] (30 [mmH2 O]) or less, the pressure switch becomes energized (switch-on) and enters the pressure monitoring mode. Then, every 0.1 second from that point (at 10 [Hz]), the energized state of the pressure switch is detected 10 times in total for 1 second, and the pressure switch is detected over 10 times in 1 second. If the energized state is continued, there is a high risk that a pressure drop abnormality due to gas leakage or the like has occurred. Therefore, the shutoff valve built in the gas meter is closed to stop the gas supply to the user side. However, if the pressure value of the gas becomes about 0.59 [kPa] (60 [mmH2 O]) or more during the pressure monitoring mode, the pressure switch returns to the non-energized state (switch off), so that there is an abnormal pressure drop. It does not determine that it has occurred and returns to the normal monitoring mode again.

  By the way, generally, in a fluid in a gaseous state having high compressibility such as gas, pulsation tends to occur easily for some reason.

  Further, in the city gas supply system, generally, one user's gas meter and gas equipment and another user's gas meter and gas equipment are connected via a pipe. If pulsation occurs in one of the users, it may affect the gas meter of the adjacent (second) user, and pulsation may occur there.

  Such pulsations can have some effect on the gas meter. Therefore, the present applicant has invented a flow rate measuring device as proposed in Japanese Patent Application Laid-Open No. 2001-183196. According to this flow rate measurement device, accurate flow rate values or integration can be achieved even in the presence of pulsation, without relying on an expensive microcomputer (hereinafter referred to as a microcomputer) that supports high-speed and large-capacity processing and consumes high power. It became possible to measure the flow rate value.

JP 2001-183196 A (Detailed description of the invention as a whole)

  The pulsation in the gas as described above is a factor that significantly hinders accurate detection even when detecting a pressure drop abnormality. It was confirmed by examination of cases and factor analysis.

  That is, when pulsation occurs in the gas via a pipe or the like in the gas meter, if the measurement period in the pressure monitoring mode matches an integer multiple of the pulsation period, only the higher side of the amplitude of the gas pulsation In some cases, the average pressure value at that time should be judged as abnormal pressure drop below the threshold pressure, but it may be overlooked (not judged as abnormal pressure drop). . Or, conversely, only the lower side of the pulsation amplitude of the gas is measured, and the average pressure value at that time should exceed the threshold pressure and be judged as a normal pressure state. May be determined.

  In addition, since the pulsations that occur in general are different, it is difficult to predict in advance what kind of pulsation will occur, so the measurement period in the pressure monitoring mode does not match the pulsation period. Thus, it is difficult or impossible to set in advance.

  In addition, in order to make it possible to measure an accurate flow rate value or integrated flow value even in a state where pulsation occurs, if the invention proposed by the present applicant in Japanese Patent Laid-Open No. 2001-183196 is used, a state where pulsation occurs However, it seems that the pressure drop abnormality can be accurately determined.

  However, according to the invention proposed in Japanese Patent Laid-Open No. 2001-183196, an accurate flow rate value or integrated flow rate value can be obtained even when pulsation occurs by measuring the gas flow rate value intermittently at non-constant periods. Although it is possible to measure, even if it is applied to the pressure drop abnormality detection as it is, it is difficult or impossible to perform accurate detection when pulsation occurs in accordance with the detection method as described above.

  That is, by performing the gas pressure measurement at non-constant periods, it is possible to avoid the measurement being biased only to the high or low amplitude of the pressure pulsation. However, conversely, this means that the measured pressure value can be scattered anywhere within the amplitude of the pressure pulsation. For example, in the case of the NI meter described above, 10 times during the pressure monitoring mode. In the pressure measurement, a pressure value exceeding a predetermined threshold pressure and the following pressure values are mixedly measured. As a result, although the average pressure value should be determined to be an abnormal pressure drop state below a predetermined threshold pressure, there is a high pressure measurement value even once in 10 times. Therefore, it may be determined that the pressure is normal and the occurrence of a pressure drop may be overlooked. This does not mean that the determination result settles on the safe side, but rather, on the contrary, the occurrence of a dangerous state such as an abnormal pressure drop (such as a gas leak that causes it) may be overlooked.

  Alternatively, in a state where pulsation is occurring, the lower pressure measurement value is frequently measured during the normal monitoring mode even though the average pressure value actually exceeds the predetermined threshold pressure. There is a possibility that the pressure monitoring mode will be entered frequently even though it is not actually necessary. As a result, the pressure measurement in the pressure monitoring mode is performed more frequently than in the normal monitoring mode, and the amount of power consumption is large, so that the battery built in the gas meter is consumed quickly.

  In addition, since pulsation does not always occur continuously or continuously, consistency must be ensured in the determination method and the determination accuracy between the state where the pulsation occurs and the state where the pulsation does not occur. In addition, even for conventional pressure drop abnormality detection methods and devices that do not take into account pulsation countermeasures, the consistency of the pressure drop abnormality detection method and device that incorporates pulsation countermeasures is ensured. It is desirable. However, such matters have not been suggested in the prior art including the invention proposed in Japanese Patent Laid-Open No. 2001-183196.

  The invention proposed in Japanese Patent Application Laid-Open No. 2001-183196 is essentially for measuring the flow rate of a fluid such as a gas, but the target physical quantity of the present invention is the pressure of the fluid. In addition, since it is to detect (determine) the presence or absence of an abnormal drop in pressure, the invention proposed in Japanese Patent Application Laid-Open No. 2001-183196 and the present invention have both a measurement object and an object, It is essentially different. For this reason, the invention for accurate flow measurement at the time of occurrence of pulsation as proposed in Japanese Patent Application Laid-Open No. 2001-183196, including the matters described above, can be applied to pressure drop abnormality detection as it is. Extremely difficult or impossible.

  Thus, conventionally, there has been a problem that accurate pressure drop abnormality detection may not be possible due to the occurrence of pulsation in the gas. In addition, it is possible to ensure the consistency of the judgment method and judgment accuracy for the conventional pressure drop abnormality detection method and equipment that does not take pulsation countermeasures into consideration. It would be desirable to devise an anomaly detection method and apparatus, but such a method and apparatus has not been proposed or even suggested.

  The present invention has been made in view of such problems, and its purpose is to enable accurate pressure drop abnormality detection even in a state where pulsation is generated in a fluid to be measured such as city gas. An object of the present invention is to provide a pressure abnormality detection device and a pressure abnormality detection method.

  The first pressure abnormality detecting device according to the present invention includes a pressure measuring means for measuring the pressure of the fluid, and a measurement by the pressure measuring means so as to measure the pressure of the fluid every non-constant period over a predetermined number of times. Pressure measurement control means for controlling the pressure, and if the average value of the pressure measured over the predetermined number of times is equal to or less than a predetermined threshold pressure, it is determined that a pressure drop abnormality has occurred in the fluid And a pressure abnormality determination detecting means.

  In the first pressure abnormality detection method according to the present invention, the pressure of the fluid is measured every non-constant period over a predetermined number of times, and the average value of the pressure measured over the predetermined number of times is a predetermined number of times. When the pressure is lower than the threshold pressure, it is determined that a pressure drop abnormality has occurred in the fluid, and when the pressure exceeds a predetermined threshold pressure, no pressure drop abnormality has occurred in the fluid. It is determined to be a thing.

  That is, in the first pressure abnormality detection device or the first pressure abnormality detection method according to the present invention, the fluid pressure is measured not at the same period but at a non-constant period every time over a predetermined number of times. Even in the state where pulsation has occurred, it is possible to measure the pressure value within the pulsation amplitude without deviation without measuring only the higher side or lower side of the pulsation amplitude. Thus, by calculating the average value of pressures measured without deviation over a predetermined number of times, it becomes possible to accurately estimate the center value of the pressure of the fluid that shakes due to pulsation. Then, the calculated average pressure value is compared with a predetermined threshold pressure, and if it is equal to or lower than the predetermined threshold pressure, it is determined that a pressure drop abnormality has occurred in the fluid. If the pressure exceeds the threshold pressure, it is determined that no abnormal pressure drop has occurred in the fluid. In this way, even when pulsation occurs, the occurrence of an abnormal pressure drop can be detected with high reliability without being adversely affected (such as disturbance or error) due to measurement bias caused by the pulsation. It becomes possible. Even when no pulsation occurs, it is possible to detect the occurrence of an abnormal pressure drop with high reliability in the same manner as when pulsation occurs (with good consistency in both cases).

  The second pressure abnormality detecting device according to the present invention includes a pressure measuring means for measuring the pressure of the fluid, and a measurement by the pressure measuring means so as to measure the pressure of the fluid every non-constant period over a predetermined number of times. The pressure measurement control means for controlling the pressure and the number of times the pressure below the predetermined threshold pressure is measured as a result of the pressure measurement over the predetermined number of times is equal to or greater than the predetermined threshold number of times. In some cases, pressure abnormality determining means for determining that a pressure drop abnormality has occurred in the fluid is provided.

  Further, the second pressure abnormality detection method according to the present invention measures the pressure of the fluid every non-constant period over a predetermined number of times, and as a result of the measurement over the predetermined number of times, the pressure is below a predetermined threshold pressure. When the number of times the pressure is measured is equal to or greater than a predetermined threshold number, it is determined that a pressure drop abnormality has occurred in the fluid, and when the number of times is less than the predetermined threshold number Is to determine that no abnormal pressure drop has occurred in the fluid.

  That is, in the second pressure abnormality detection device or the second pressure abnormality detection method according to the present invention, as in the case of the first pressure abnormality detection device or the first pressure abnormality detection method, a predetermined number of times are obtained. By measuring the fluid pressure every non-constant period instead of every same period, only the higher and lower levels of the pulsation amplitude are measured even when pulsation occurs in the fluid. Therefore, the pressure value within the amplitude of the pulsation can be measured without deviation. In other words, the probability that the higher side of pressure pulsation amplitude (pressure value higher than the central value of pulsation) is measured and the lower side of pressure pulsation amplitude (pressure value lower than the central value of pulsation) The measured probability is equal. And as a result of the measurement over the predetermined number of times (for example, 11 times), the number of times the pressure below the predetermined threshold pressure is measured is, for example, 6 times that is more than half of the total number of 11 times of measurement. If the number of times is equal to or greater than the set threshold number of times, it is estimated that the center value of the pulsation amplitude of the fluid pressure is less than or equal to the predetermined threshold pressure. On the contrary, if the number of times is less than the predetermined threshold number, the central value of the pulsation amplitude of the fluid pressure is greater than the predetermined threshold pressure. Since it is estimated, it is determined that no abnormal pressure drop has occurred in the fluid. In this way, even when pulsation occurs, the occurrence of pressure drop abnormality can be detected with high reliability without being adversely affected by measurement bias caused by the pulsation. Even when no pulsation occurs, it is possible to detect the occurrence of an abnormal pressure drop with high reliability in the same manner as when pulsation occurs (with good consistency in both cases).

  Here, in the second pressure abnormality detecting device or the second pressure abnormality detecting method according to the present invention, the threshold number of times in the pressure abnormality determining means is more than half or all of a predetermined number (total number of measurements). It is desirable to set the number of times in between. For example, when the number of all measurements (predetermined number) is 11, the threshold number is any number between 6 and 11 (6 times, 7 times, 8 times,... It is desirable to set it to any one of 11 times.

  In addition, as a measurement of said non-constant period, you may make it measure the pressure of the fluid with a random period without the repetition of the same period. By doing so, it becomes possible to measure the pressure of the fluid in a completely random cycle within a predetermined number of times of measurement, and it is possible to measure a pressure value without deviation within the amplitude of pulsation.

  Alternatively, as the measurement of the non-constant period, the fluid pressure may be measured at a non-constant period including a certain period and an odd multiple of the half period over a predetermined number of times. Good. By doing so, for example, when a certain measurement cycle and the pulsation cycle coincide by chance in a plurality of predetermined measurements, two pressure values measured in the measurement cycle at that time Are biased to the high or low side, but in the next measurement round, the pressure was measured at an odd multiple of a half cycle of the previous measurement period, and the measurement was made at the previous two times. A pressure value biased to the opposite side of the pressure value bias is measured. For example, if the pressure value on the higher side of the pulsation is measured at the previous two timings, the pressure value on the lower side of the pulsation is measured at the next timing (through an odd multiple of the half cycle). Is measured. In this way, it is possible to avoid biasing and measuring only the higher side and the lower side of the pulsation.

  It is also possible to determine the occurrence of a fluid pressure drop abnormality based on the remaining measured values obtained by removing the maximum value and the minimum value from the measured pressure values measured over a predetermined number of times. desirable. That is, when the pulsation is generated in the fluid to be measured, the pressure value changes between the maximum value and the minimum value of the amplitude of the pulsation. Therefore, the measured value of the pressure measured over a predetermined number of times. Includes a maximum value and a minimum value that are significantly deviated from the center value due to pulsation (a large error from the center value). Therefore, it is possible to determine the occurrence of a fluid pressure drop abnormality based on the remaining measured values obtained by removing the maximum value and the minimum value from the measured pressure values measured over a predetermined number of times. In addition, it is possible to detect the occurrence of the pressure drop abnormality with high reliability by eliminating the disturbance or the mixing of errors in the pressure measurement and the pressure drop abnormality determination caused by the pulsation.

  In the first monitoring period, the pressure of the fluid is measured for a predetermined number of times, and based on the pressure measured in the first monitoring period, whether or not a fluid pressure drop abnormality has occurred is first determined. If the provisional determination is made and it is temporarily determined that there is a pressure drop abnormality in the fluid, then the fluid pressure is measured a predetermined number of times in the second monitoring period, and the second Based on the pressure measured during the monitoring period, a final determination may be made as to whether or not a fluid pressure drop abnormality has occurred.

  That is, even if a low pressure value is continuously measured over a predetermined monitoring period, such as 3 seconds, and it is determined that the pressure drop is abnormal, it is actually finally detected such as gas leakage. For example, if it occurs instantaneously because the operation of a large-capacity gas consuming device is accidentally started at that time, the determination of abnormal pressure drop at that time is substantially incorrect. It will be a decision. Therefore, in order to avoid such an erroneous determination, the second monitoring period is provided following the first monitoring period as described above, and the pressure drop abnormality is continuously detected even in the second monitoring period. In this case, for example, it is desirable to finally determine that an abnormality in pressure drop due to gas leakage has occurred. By providing a measure for avoiding such erroneous determination, consistency with a pressure drop abnormality detection device or a pressure drop abnormality detection method used in a general gas meter is improved.

  More specifically, if the average value of the pressure measured in the second monitoring period exceeds a predetermined threshold pressure, no abnormal pressure drop has occurred in the fluid, or the second monitoring It may be determined that the pressure has returned to normal during the period, and if the pressure is equal to or lower than a predetermined threshold pressure, it may be determined that a pressure drop abnormality has occurred in the fluid.

  Alternatively, as a result of the pressure measurement over the predetermined number of times in the second monitoring period, the number of times the pressure exceeding the predetermined threshold pressure is measured is equal to or greater than the predetermined threshold number of times. In such a case, it is determined that no abnormal pressure drop has occurred in the fluid or that the fluid has returned to normal during the second monitoring period. It may be determined that an abnormality has occurred.

  Further, when the fluid pressure exceeds a predetermined threshold pressure, the fluid pressure is measured in a period set to a period longer than the non-constant period as the normal monitoring mode, and the fluid pressure is When the pressure falls below a predetermined threshold pressure, the pressure of the fluid is measured at a non-constant period for a predetermined number of times as a judgment mode, and an abnormal pressure drop occurs in the fluid based on the result of the measurement. If it is determined that there is no error, the determination mode may be canceled and the normal monitoring mode may be returned.

  That is, as the normal monitoring mode, the fluid pressure is measured in a long cycle, and when the fluid pressure falls below a predetermined threshold pressure in the normal monitoring mode, the determination mode is entered from that time. enter. In the determination mode, the pressure of the fluid is frequently measured for each non-constant period set shorter than the normal monitoring mode for a predetermined number of times as described above, and based on the measurement result, Next, it is determined whether or not a pressure drop abnormality has occurred. When it is determined that no abnormality in pressure drop has occurred, the determination mode in which frequent measurement is performed with a non-constant period is canceled, and the normal monitoring mode in which the fluid pressure is measured with a long period is returned. Alternatively, if it is determined that a pressure drop abnormality has occurred, for example, in the case of a gas meter, the gas supply is stopped by operating a shut-off valve, or a warning that a pressure drop abnormality has occurred. Needless to say, it may be set so that the determination mode is forcibly executed from the outside, for example, by executing a measure such as issuing a determination. By doing so, frequent monitoring and determination are necessary because there is a suspicion of occurrence of an abnormal pressure drop, and therefore, a determination mode that tends to increase power consumption needs to be really frequently monitored and determined. It is possible to reduce the amount of power consumed for pressure drop abnormality measurement or judgment by executing only in the case and maintaining the normal monitoring mode in the normal case where such a need is not required It becomes.

  In addition, a plurality of sets of maximum and minimum values are extracted from the measured pressure values measured over a predetermined number of times, and the difference between each of the plurality of sets of maximum and minimum values is calculated. The difference is compared with a predetermined pulsation amplitude determination threshold value, and if each of the plural sets is equal to or greater than the pulsation amplitude determination threshold value, it is determined that pulsation has occurred, and the pulsation amplitude determination If it is less than the threshold value, it may be determined that no pulsation has occurred. When it is determined that pulsation has occurred, it is desirable to record or output information indicating that pulsation has occurred.

  That is, in the pressure abnormality detection device or the pressure abnormality detection method according to the present invention, it is possible to measure the pressure value within the amplitude of the pulsation without any deviation, so that the pressure measurement value measured over a predetermined number of times can be measured. The difference between the maximum value and the minimum value is a significant value corresponding to the amplitude of the pulsation with high probability if pulsation has occurred at that time. Therefore, the difference between the maximum value and the minimum value of the measured pressure values measured over a predetermined number of times is calculated, and the difference value is used as a pressure displacement corresponding to a measurement error, fluid temperature change, etc. Compared with a predetermined pulsation amplitude determination threshold value as a significant value that can be determined to correspond to a clearly different pulsation amplitude, the difference values are all equal to or greater than the pulsation amplitude determination threshold value. In this case, it can be determined that pulsation has occurred, and if it is less than the pulsation amplitude determination threshold, it can be determined that pulsation has not occurred. Here, using the difference between the maximum value and the minimum value of each of the plurality of sets, if each of the plurality of sets is equal to or greater than the pulsation amplitude determination threshold, it is determined that pulsation has occurred. Even if the pressure value changes drastically during a predetermined number of measurements in a state where no pulsation occurs, using only the difference between a set of maximum and minimum values, This is for avoiding such erroneous determination because there is a possibility that it is determined that “pulsation is present”. In a state where pulsation occurs, generally, a plurality of sets of maximum and minimum values can be extracted from the measured pressure values, and the difference between the plurality of sets of maximum and minimum values is Both have a high probability of becoming a significant pulsation amplitude determination threshold corresponding to the pulsation amplitude, but in the state where no pulsation has occurred, the difference between the maximum and minimum values is a significant pulsation amplitude determination threshold. This is because it is rare that a plurality of sets of maximum and minimum values exist.

  Here, the fluid pressure is combustible gas, and the above-described gas pressure drop abnormality is detected by a gas meter that performs flow rate measurement using the gas as a measurement target. It is a desirable mode of an apparatus or a pressure abnormality detection method. Further, in the case of such a gas meter, since it is generally provided with a shut-off valve that shuts off the gas conduction, when it is determined that an abnormal pressure drop has occurred in the gas as described above, It is desirable to shut off the gas conduction by closing the shut-off valve. By doing so, it is possible to reliably detect an abnormal gas pressure drop without erroneous determination and shut off the gas, thereby avoiding a dangerous state such as gas leakage.

  In addition, the dispersion of the pressure measured over the predetermined number of times is calculated, and the dispersion is compared with a predetermined threshold. When the dispersion is equal to or greater than the threshold, pulsation occurs in the fluid. It may be determined that there is no pulsation when the variance is less than the threshold value. Thereby, a pressure abnormality due to the occurrence of pulsation can be detected. In that case, for example, the mode can be shifted to the monitoring mode in the second monitoring period. When the dispersion is extremely large, the shutoff valve may be closed for safety to shut off the gas conduction regardless of the average pressure.

  As described below, according to the pressure abnormality detection device according to any one of claims 1 to 14 or the pressure abnormality detection method according to any one of claims 15 to 28, the same every time over a predetermined number of times. Since the fluid pressure is measured every non-constant period instead of every period, even if the pulsation occurs in the fluid, without measuring only the high side or low side of the amplitude of the pulsation, The pressure value within the amplitude of the pulsation can be measured without deviation.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a schematic configuration of a gas meter including a pressure abnormality detection device according to an embodiment of the present invention. In addition, since the pressure abnormality detection method which concerns on embodiment of this invention is embodied by the operation | movement or effect | action of the pressure abnormality detection apparatus incorporated in this gas meter, they are demonstrated collectively below. Further, in order to avoid complication of illustration and description, details of the membrane type flow meter and the integrated flow value counter (or integrated flow value display) that are generally built in the gas meter are omitted. To do. This gas meter includes a flow rate measuring device 100, a shut-off valve device 200, a pressure abnormality detection device 300, an information storage device 400, and a display device 500.

  The flow rate measuring device 100 measures the flow rate of the gas flowing through the pipe 101, for example, a flow rate measuring device (not shown) such as a membrane type or an ultrasonic wave propagation method, and an integrated flow rate value obtained by integrating the flow rate measured thereby. Is an ordinary flow rate display counter (not shown) or the like.

  The shut-off valve device 200 includes a valve body 201 and a valve drive mechanism 202 using, for example, a solenoid coil, and the main part thereof is configured. As will be described later, the operation is controlled by the control unit 306, and when a pressure drop abnormality is detected, the valve drive mechanism 202 is moved so that the valve body 201 is closed, and gas conduction is performed. Cut off. When returning the valve body 201 to the open state, for example, when the user presses a return button (not shown) attached to the body of the gas meter, the valve body 201 is returned from the closed state to the open state by using it as a command input. As a result, the gas conduction is resumed.

  The pressure abnormality detection device 300 includes a pressure sensor 301, an A / D converter 302, a pressure value calculation unit 303, a pressure drop abnormality determination unit 304, a control law storage unit 305, and a control unit 306. The part is composed.

  The pressure sensor (pressure measuring means) 301 may be a general one that is used for a so-called NI meter and that converts the pressure of a gas to be measured into an electrical signal or a voltage level by a piezoelectric device, for example, and outputs it. Absent. Alternatively, a combination of a diaphragm whose surface changes according to the gas pressure and a contact switch set so that the electrical connection state of the contact changes in conjunction with the change, as used in a so-called NB meter. A pressure switch (not shown) or the like can also be used as the pressure sensor 301.

  The A / D converter 302 converts analog electric signals (or voltage levels; hereinafter collectively referred to as electric signals) output from the pressure sensor 301 into digital signals and outputs the digital signals.

  The pressure value calculation unit 303 reads the electric signal output from the pressure sensor 301 via the A / D converter 302 with the reading timing controlled by the control unit 306 in a non-constant period. Then, the pressure value is calculated based on the read electric signal obtained by A / D conversion, and the information (data) is sent to the pressure drop abnormality determination unit 304.

  The pressure drop abnormality determination unit 304 is controlled by the control unit 306 based on the control law stored in the control law storage unit 305, and determines whether or not the pressure drop abnormality has occurred based on the measured pressure value. There are mainly two methods for performing this determination (action). It calculates the average value of multiple pressure measurements and compares it with a predetermined threshold value, and the pressure measurement values obtained by multiple measurements are below a predetermined threshold value. A method of comparing the number of occurrences with a predetermined threshold number of times, the details of which will be described later. Further, the pressure drop abnormality determination unit 304 determines whether or not pulsation has occurred based on the pressure measurement values obtained by a plurality of measurements. Details of this determination operation will also be described later.

  The control law storage unit 305 is a control law for controlling the timing at which the pressure value calculation unit 303 reads the output from the pressure sensor 301, and is used when the pressure drop abnormality determination unit 304 determines whether or not a pressure drop abnormality has occurred. Judgment logic, a control law for bringing the shut-off valve device 200 into a shut-off state when it is determined that a pressure drop abnormality has occurred, a case where it has been determined that a pressure drop abnormality has occurred, or a pulsation has been determined In addition to the information on the date and time of occurrence, a control rule for storing the information in the information storage device 400 and a control rule for displaying the information on the display device 500 are stored. Further, the control law storage unit 305 may store, for example, a control law for controlling the operation of the flow rate measuring device 100 in addition to the control law and judgment logic related to the pressure drop abnormality judgment. Needless to say.

  The control unit 306 controls the operation of the pressure value calculation unit 303, the pressure drop abnormality determination unit 304, and the shut-off valve device 200 based on the control law stored in the control law storage unit 305. In addition, the operation of the flow rate measuring device 100 is controlled.

  When the pressure drop abnormality determination unit 304 determines that a pressure drop abnormality has occurred, or when it is determined that pulsation has occurred, the information storage device 400 stores information to that effect along with information on the date and time of occurrence thereof. It is. Information (data) stored in the information storage device 400 may be read out of the gas meter via a communication device (not shown) such as a telephone line, or a liquid crystal display panel (not shown). ) Or the like may be displayed in a segment display or dot matrix display on the display screen of the display device 500.

  The display device 500 displays and outputs information indicating that a pressure drop abnormality or pulsation has occurred in association with the information on the occurrence date and time. In the case where the flow rate measuring device 100 can output the integrated flow rate value as an electrical signal, for example, the display unit 500 displays the integrated flow rate value at the normal time, and a display switching command is given from the outside. When input, information indicating that a pressure drop abnormality or pulsation has occurred may be displayed on the display device 500 so that the display mode can be switched.

  Next, the operation of the gas meter, in particular, the pressure abnormality detection device 300 will be described.

  FIG. 2 schematically shows an example of pressure measurement timing when pressure measurement is performed at a non-constant period (random period) over 25 times in a state where pulsation is generated in the gas. Such control of the pressure measurement timing is executed by the control unit 306 controlling the reading timing in the pressure value calculation unit 303.

  In the example shown in FIG. 2, the period λ1 between the first measurement and the second measurement, the period λ2 between the second measurement and the third measurement,... The 24th measurement. The period λ24 between the measurement and the 25th measurement is set to be long and short so that the same period does not continue, and there is no repetition of the combination of periods in a plurality of consecutive periods. Yes. Such a combination of a plurality of periods may be determined based on, for example, a random number table, or a total of 24 periods (λ1, λ2,... Λ24) are different from each other. You may set so that it may be a period.

  However, here, for example, if the period of λ1 is 1, and the period of λ1, λ2,... Λ24 is set to 1: 2: 3: 4. If the period and λ1 match or approximate, all other periods (λ2,... Λ24) will also be an integral multiple of the pulsation period, so the measurement result is higher on the pulsation side. It will be biased to the lower side. In order to avoid such an inconvenience, the individual periods (λ 1: λ 2: λ 3... Λ 24) are not set to integer ratios. For example, λ 1: λ 2: λ 3. It is effective to set the ratio so that the ratio of the periods cannot be reduced to the integer ratio, such as 2.3: 0.7 ... 1.9. Alternatively, it is also effective to set the individual periods to have a prime number ratio.

  Alternatively, the pressure measurement may be performed at a non-constant period including a period λ0 and an odd multiple of the half period (λ0 / 2, 3λ0 / 2, 5λ0 / 2, 7λ0 / 2...). It is valid. Specifically, as shown in FIG. 3, for example, when the period λ1 between the first and second times coincides with the pulsation period λp by chance, the measurement was performed at the measurement period at that time. Both of the two pressure values are biased toward the higher side of the pulsation. However, in the next measurement cycle λ2, the cycle is an odd multiple of a half cycle of the previous measurement cycle (for example, in the example of FIG. 3, λ2 is 3 of λ1). By measuring the pressure at a cycle of / 2 times), a pressure value biased to the opposite side (low side) to the pressure value bias measured at the previous two timings is measured. As described above, in the example of FIG. 3, the pressure value on the higher side of the pulsation is measured at both the first and second timings with λ1 interposed therebetween, but the next time (from the second timing, λ2 At the third timing (after the elapse of time), since the phase is inverted from the previous time (second time), the pressure value on the lower side of the pulsation is measured. In this way, it is possible to avoid measuring only the high-order side or the low-order side of pulsation.

  However, when the measurement timing is composed only of a combination of one cycle as described above and a cycle that is an odd multiple of the half of the cycle, assuming that the minimum cycle is 1, the measurement timing is configured. The ratio of the combinations of all the periods is an integer ratio such as 1: 3: 5: 7. For this reason, for example, if the minimum period of all the periods coincides with or approximates the pulsation period, all the periods become an integral multiple of the pulsation period. There is a risk of biasing to the lower side. Therefore, in order to avoid such inconvenience, the entire measurement timing is not composed only of a combination of a certain period and a period that is an odd multiple of the half period, but the random number table as described above is included in the combination. It is effective to mix a random period and a random period with a prime ratio.

  As described above, by measuring the pressure at a non-constant cycle timing, even when pulsation is generated in the gas, it is possible to avoid the pressure measurement timing from being biased toward the higher or lower side of the pulsation. . In other words, by measuring the pressure at a non-constant period as described above, the phase of the measurement timing can be shifted with respect to the pulsation period of the pressure, so the result (measurement value) of the pressure measurement is In other words, it can be distributed with no probability within the amplitude of the pulsation. More specifically, by measuring the pressure at a non-constant period timing as described above in a state where pulsation is occurring, the probability of measuring the pressure value on the higher side of the pulsation is also lower. The probability of measuring the pressure value can also be both 50%. By utilizing this action, the pressure drop abnormality determination unit 304 can accurately and reliably (without erroneous determination) and reliably (without overlooking) the pressure drop abnormality even when pulsation occurs by two methods. It can be judged.

  That is, as a first determination method, an average value Pm of a plurality of pressure measurement values measured in a non-constant period as described above is calculated and compared with a predetermined threshold pressure PL-th. . When Pm ≦ PL-th, it is determined that there is a pressure drop abnormality, and when Pm> PL-th, it is determined that there is no pressure drop abnormality.

  FIG. 4 shows the main operation flow in the pressure drop abnormality detection device according to the present embodiment, focusing on the first determination method. When the gas pressure is in a state exceeding a threshold pressure PL-th such as 0.83 [kPa], for example, the normal monitoring mode is longer than a non-constant period in a determination mode described later, for example, 10 The gas pressure is measured every cycle such as every second (N to S41 of S41 to S42). Note that the measurement period in the normal monitoring mode may be a fixed period (a constant period), but is more preferably a non-constant period. For example, pulsation may occur without interruption. In this case, if the cycle and the fixed cycle in the normal monitoring mode match or approximate, the pressure measurement value will be biased and accurate pressure drop abnormality detection will occur. It is because there is a possibility that it becomes impossible. However, the measurement cycle in the normal monitoring mode is a long cycle level such as 10 seconds, and on the other hand, the pulsation cycle is a very short cycle level such as 0.01 seconds. Even if the measurement cycle of the normal monitoring mode coincides with the measurement cycle of pulsation by chance, there is a higher probability that a phase shift between them will occur over time. Since there is a tendency that the necessity for the measurement in is low, a fixed period may be used in the normal monitoring mode.

  When the pressure value P measured in the normal monitoring mode becomes equal to or less than the threshold pressure PL-th (Y in S42), the determination mode is set to a predetermined time such as 3 seconds. In the determination mode, as described above, the pressure is measured over a predetermined number of times, for example, a total of 25 times at each non-constant period timing (S43), and measured over the predetermined number of times. The pressure measurement value is temporarily stored and held (S44).

  Then, an average value Pm of the pressure measurement values measured and stored for all 25 times is calculated (S45). At this time, the individual pressure measurement values obtained in all 25 measurements are measured without any phase deviation from the pulsation waveform, and therefore are extracted (measured) with equal probability from the pulsation amplitude. It can be regarded as a thing. Therefore, the average value Pm calculated from the pressure measurement values measured over 25 times is approximated with high probability to the central value of the pressure pulsation.

  The average value Pm of the pressure measurement values calculated in this way is compared with a predetermined threshold pressure PL-th (S46). As a result of the comparison, if Pm ≦ PL-th (Y of S46), it is determined that there is a pressure drop abnormality (S47), and a warning and information to that effect are displayed together with information on the date and time at that time. The information is displayed and output together with the information storage device 400 (S48). However, if Pm> PL-th (N in S46), it is determined that there is no pressure drop abnormality, the determination mode is canceled, and the normal monitoring mode is returned (N to S41 in S46).

  When calculating the average value Pm of the pressure measurement values, the maximum value and the minimum value are excluded from all the pressure measurement values, and the average value of the remaining pressure measurement values is calculated. Also good. Alternatively, a large value from the maximum value to the kth and a small value from the minimum value to the jth (k and j are predetermined natural numbers) are excluded, and an average value of the remaining pressure measurement values is calculated. You may do it. In order to improve the symmetry of excluding measured values centered on the pulsation center value (this is the symmetry of the measured values used to calculate the average value) When the number of times of measurement is made as high as possible, it is expected that the probability that the higher value at that time is measured and the probability that the lower value is measured are equal to 50%, so k = j is set. It is desirable. However, for example, when it is found that the probability that the lower pressure value is statistically measured tends to be slightly higher due to, for example, a practical instrumental difference of the pressure detection device 300 or higher. In order to correct this, it is also effective not to set k = j but to divide the symmetry and set k <j.

  As a second determination method, among the predetermined number of measurements in the determination mode, the number N of times when the measured pressure measurement value P is equal to or less than the predetermined threshold pressure PL-th is, for example, the total number of measurements. Compare with a predetermined threshold number of times NL-th, such as more than half the number of times. When N ≧ NL-th, the number of times the pressure measurement value P is equal to or less than the predetermined threshold pressure PL-th is so large that the pulsation center value is the threshold pressure PL- This means that the probability of being equal to or less than th is high, and it is determined that there is a pressure drop abnormality. However, if N <NL-th, the probability that the center value of pulsation is equal to or lower than the threshold pressure PL-th is low, so it is determined that there is no pressure drop abnormality.

  This second determination method will be described in more detail. FIG. 5 schematically shows an example of a dispersion state of pressure measurement values when pressure is measured at a non-constant period when pulsation occurs in the pressure abnormality detection device and pressure abnormality detection method according to the present embodiment. It is. In FIG. 5, the pressure values measured at non-constant periods are indicated by dots. In addition, in order to simplify the explanation, in the following explanation, the number of measurements is set to an extremely small number such as 25, but in reality, the reliability of the expected value of the pressure measurement value is statistically sufficient. Needless to say, it is desirable to set a large number of measurement times so as to achieve a certain value. Further, for simplification of explanation and illustration, illustration of pulsation in the middle of one determination mode period is omitted.

  In the pressure abnormality detection device and the pressure abnormality detection method according to the present embodiment, since the pressure is measured in a non-constant period as described above, the pressure value within the amplitude of the pulsation is measured without deviation. In other words, regardless of the amplitude and period of the pulsation, the pressure measurement values measured in a non-constant period over the entire number of measurements are distributed evenly within the pulsation amplitude. In this schematic example, of the 25 pressure measurements, 12 are on the high side of the pulsation, 1 is on the center of the pulsation, and the other 12 are on the low side of the pulsation. Distributed. Thus, by measuring the pressure frequently at non-constant periods, the probability that the higher side of the pressure pulsation amplitude (pressure value higher than the central value of the pulsation) will be measured, and the lower side of the pressure pulsation amplitude The probability that (pressure value lower than the central value of the pulsation) is measured is equal to 50%. Alternatively, the value is approximately 50%.

  Here, a case where the central value of the pulsation coincides with the threshold pressure PL-th as a critical state is considered as one schematic model. In this case, the pressure measurement value measured over the entire number of measurements in a non-constant period is half of the threshold pressure PL-th (= the central value of pulsation) on the higher side from the above probability theory. The number of measurements is distributed, and the remaining half of the number of measurements is distributed on the lower side. In other words, when the center value of the pulsation is actually equal to or less than the threshold pressure PL-th, the pressure value below the threshold pressure PL-th among the total number of measurements. The number of times that is measured is estimated as an expected value to be half or more of the total number of measurements. In other words, if the number of times the pressure value below the threshold pressure PL-th is measured is 50% or more of the total number of measurements, then the center value of the pulsation is the threshold value. The probability that the pressure is equal to or lower than the pressure PL-th is high, and in this case, it can be determined that the pressure drop is abnormal. In other words, if the pressure value below the threshold pressure PL-th is less than 50% of the total number of measurements, the central value of the pulsation at that time is the threshold pressure PL-th. This means that it is highly probable that it is super, and in this case, it can be determined that no pressure drop abnormality has occurred.

  From the consideration regarding such a critical state, it can be understood that the threshold number NL-th used for determination of the pressure drop abnormality may be set to a value that is half or more of the total number of measurements. For example, when the total number of measurements is 25 as in the example schematically shown in FIG. 5 above, it is desirable to set the minimum value to 13 times among the number of times more than half. Alternatively, it may be set to 14 or 15 times more than that. However, as the threshold number NL-th is set to a higher value, the determination accuracy of occurrence of pressure drop abnormality can be increased (the probability of erroneous determination can be decreased), but in a trade-off with that, There is also a tendency for the probability of missing a critical pressure drop abnormality to increase.

  FIG. 6 schematically shows a case where the center value P0 of the pulsation with the amplitude A is shifted by a pressure S (lower pressure) to the lower pressure side than the threshold pressure PL-th. is there. In FIG. 6, the pulsation waveform is approximated by a linear sawtooth wave having a fixed period in order to make the description easier to understand by simplifying the illustration. In this case, when the pressure is measured at a non-constant period, the probability that a pressure value equal to or less than PL-th is measured increases in proportion to the deviation amount S. For example, when the deviation amount S is 20% of the pulsation amplitude A, 50 + 20 = 70% of the pulsation amplitude is below the threshold pressure PL-th. The probability that the pressure value is measured is 70%. Therefore, in this case, for example, the expected value of the number of times that the pressure value equal to or lower than the threshold pressure PL-th is measured out of 25 times is 25 × 70% = 17.5 times. Therefore, it is estimated as an expected value that the number of times the pressure value below the threshold pressure PL-th is measured is 18 out of 25 times. In other words, if the number of times the pressure value less than or equal to the threshold pressure PL-th is measured is 18 or more out of 25, the pulsation center value is greater than the threshold pressure PL-th. That is, it can be determined that the amplitude A is lower by 20% or more (shifted to the low pressure side).

  However, conversely, if the threshold number NL-th is set to 18 or more, the center value of pulsation must be 20% or more lower than the threshold pressure PL-th. It also means that it is not determined that “there is a pressure drop abnormality”. In other words, when the pulsation center value P0 is equal to or less than the threshold pressure PL-th and less than 20% of the amplitude A, a pressure value less than the threshold pressure PL-th is measured. Since the probability is 50% or more and less than 70%, the expected number of times is 13 to 17 times. Therefore, although the center value of the pulsation is actually equal to or lower than the threshold pressure PL-th and should be determined as “abnormal pressure drop”, the pressure equal to or lower than the threshold pressure PL-th It is highly probable that the number of times of measurement will not exceed 18 times (= threshold number of times NL-th). Therefore, it is not determined that there is “abnormal pressure drop” and the actual occurrence of abnormal pressure drop is overlooked. It means that there is a risk of it.

  In summary, by setting the threshold number of times NL-th to more than half of the total number of measurements, the judgment conditions can be made stricter or the judgment accuracy can be increased, but the pressure drop abnormality This means that there is a high probability that the occurrence of the occurrence will be missed.

  On the other hand, although the pulsation center value P0 is greater than the threshold pressure PL-th, the number of times the pressure below the threshold pressure PL-th is measured is half of all 25 times (13 times) As described above, there is a risk that a false pressure drop abnormality may be erroneously determined even though no pressure drop abnormality has actually occurred, such as accidental stochastic fluctuations and instrumental errors. This may be due to various factors. Therefore, in order to avoid such a misjudgment, if the threshold number NL-th is set to a number larger than half of the total number of measurements, the determination accuracy is improved. It is effective to set the threshold number of times NL-th to be greater than 13 times, which is half of the total number of times of measurement, for example, 14 times or 15 times.

  FIG. 7 shows a flow of main operations in the pressure drop abnormality detection device according to the present embodiment, focusing on the second determination method.

  When the gas pressure is in a value exceeding a threshold pressure PL-th such as 0.83 [kPa], for example, the gas is detected as a normal monitoring mode every cycle longer than the non-constant cycle in the determination mode. Is measured (N to S71 of S71 to S72). The measurement period in the normal monitoring mode may be a fixed period (a constant period), but it is more preferable to set the measurement period to a non-constant period, as in the first determination method.

  When the pressure value P measured in the normal monitoring mode becomes equal to or lower than the threshold pressure PL-th (Y in S72), a determination mode set to a predetermined time such as 3 seconds is entered. In the determination mode, as described above, the pressure is measured over a predetermined number of times, for example, a total of 25 times at each non-constant period timing (S73), and measured over the predetermined number of times. Individual pressure measurement values are temporarily stored (S74).

  Then, the individual measured pressure values (P1, P2, P3,... Pn,..., P25) measured and stored over 25 times are respectively compared with a predetermined threshold pressure PL-th ( S75). Then, the number N of times when the pressure measurement value Pn is equal to or less than the threshold pressure PL-th is counted (S76).

  The number N thus counted is compared with a predetermined threshold number NL-th set in advance, for example, 13 times (S77). As a result of the comparison, if NL-th ≦ N (Y in S77), it is determined that there is a pressure drop abnormality (S78), and a warning and information to that effect are displayed together with the date and time information at that time. The information is displayed and output together with the information storage device 400 (S79). However, if NL-th> N (N in S77), it is determined that there is no pressure drop abnormality, the determination mode is canceled, and the normal monitoring mode is returned (N to S71 in S77).

  In addition, as shown in FIG. 8 as the main flow, the maximum value and the minimum value are excluded from all the pressure measurement values that have been temporarily stored and retained (S74) (S81), and the remaining remaining values are excluded. The pressure measurement value Pn is compared with the threshold pressure PL-th (S75), and the number N of times that the pressure is less than or equal to the threshold pressure PL-th is counted (S76). The number of times may be compared with NL-th (S77). In FIG. 8, steps similar to those in FIG. 7 are denoted by the same reference numerals as in FIG. In this way, the maximum and minimum values of pressure measurement values that are measured near the maximum or minimum pulsation amplitude and may increase the probability of erroneous determination or oversight are excluded. By doing so, it becomes possible to further ensure the reliability (accuracy) of the determination.

  In this case, however, the threshold number NL-th is smaller than the number of times when the maximum value and the minimum value are not excluded, corresponding to the number of times when the maximum value and the minimum value are excluded twice. Needless to say, setting is necessary. For example, if the maximum number and the minimum value are not excluded in all 25 measurements, and the threshold number NL-th is set to 13 times that is 50% or more of the total number, the maximum and minimum values Is excluded, the number of times of measurement used for the determination is substantially 23, so 23 times × 50% = 11.5. Therefore, when the determination is performed excluding the maximum value and the minimum value, The threshold number NL-th must be set to 12.

  Alternatively, a large value from the maximum value to the mth and a small value from the minimum value to the mth (m is a natural number) are excluded, and the remaining individual pressure measurement values Pn are used as the threshold pressure PL. You may make it judge compared with -th. As judgment logic in this case, the maximum and minimum values up to m-th of all the pressure measurement values are excluded, and the remaining pressure measurement values Pn are compared with the threshold pressure PL-th, respectively. Then, it is possible to compare the number N of the threshold pressures PL-th or less with the threshold number of times NL-th, but it is not limited to this.

  In addition to this, for example, as shown in the main flow in FIG. 9, after excluding the large value from the maximum value to the mth and the small value from the minimum value to the mth, The measured pressure value Pi is compared with the threshold pressure PL-th (S92), and if Pi ≦ PL-th (Y in S92), it may be determined that the pressure drop is abnormal. Good. That is, in this case, the determination is not made based on the number N of times where Pi ≦ PL−th, but the measured value fluctuation due to pulsation is the smallest and most approximate to the pulsation center value P0. Using Pi, which is an estimated value, a determination is made based directly on whether Pi ≦ PL-th. In FIG. 9, steps similar to those in FIGS. 7 and 8 are denoted by the same reference numerals.

  For example, out of the 25 pressure measurement values obtained by all 25 measurements, if the large value from the maximum value to the twelfth and the small value from the minimum value to the twelfth are excluded, the remaining one The pressure measurement value Pi is estimated to be a value closest to the pulsation center value P0 among the pressure measurement values obtained by all 25 measurements. Therefore, by comparing this pressure measurement value Pi with the threshold pressure PL-th, it is possible to accurately determine whether or not a pressure drop abnormality has occurred with a high probability.

  Here, for example, depending on conditions, a large pressure drop temporarily occurs over several seconds, but such a pressure drop state itself may be canceled and the pressure may return to a normal pressure range. For this reason, when the determination mode period set for a short period of about 3 seconds as described above coincides with the timing of the temporary pressure drop state, the determination is performed based on the pressure value measured at that time. Then, there is a risk that a temporary pressure drop or the like may be erroneously determined as a long-term pressure drop abnormality caused by gas leakage or the like. This is true for both the first determination method and the second determination method.

  Therefore, in order to eliminate such a misjudgment, the period during which the monitoring in the judgment mode as described above is performed is the first monitoring period, and when it is determined that there is a pressure drop abnormality in the first monitoring period. Is provided with a second monitoring period for monitoring in the determination mode following the first monitoring period, and if it is determined that there is a pressure drop abnormality even in the second monitoring period, a temporary Assuming that a substantial pressure drop abnormality has occurred instead of a pressure drop or the like, it may be finally determined that “there is a pressure drop abnormality”. If it is not determined that there is an abnormal pressure drop in the second monitoring period, it is assumed that a pressure drop due to a temporary pressure drop or the like has been accidentally measured in the first monitoring period. Needless to say, it can be finally determined that there is no abnormality in pressure drop.

  By the way, both of the first determination method and the second determination method as described above can accurately detect (determine) a pressure drop abnormality even in a state where no pulsation occurs. This is because the state in which no pulsation occurs means that the amplitude of the pulsation is A = 0 (or within a small fluctuation range of pressure fluctuation caused by temperature change; A≈0). Since the average value Pm of the pressure measurement values and all the pressure measurement values Pn are equal to the actual gas pressure value P at that time, when the actual pressure value P is lower than the threshold pressure PL-th, the pressure Since the average value Pm of the measured values is equal to or lower than the threshold pressure PL-th and the pressure measured value Pn is equal to or lower than the threshold pressure PL-th in all measurement times, N ≧ NL-th. It is determined that there is a decrease abnormality. Thus, the pressure abnormality detection device according to the present embodiment is consistent with the determination of pressure drop abnormality with respect to the pressure abnormality detection device of a general gas meter that does not take measures against pulsation, and when pulsation occurs. The consistency of judgment in the case where it does not occur is good.

  Further, in the pressure abnormality detection device according to the present embodiment, even if the period and amplitude of pulsation change, the pressure measurement period during the determination mode period is always changed to a non-constant period. There is no bias toward the lower or higher pulsation.

  Here, it is also possible to determine the presence or absence of pulsation itself. That is, according to the pressure abnormality detection device or the pressure abnormality detection method according to the present embodiment, it is possible to measure the pressure value without deviation within the amplitude of the pulsation. The difference ΔPn (= Pmax−Pmin) between the maximum value Pmax and the minimum value Pmin among the measured pressure values is a significant value corresponding to the amplitude of the pulsation with high probability if pulsation has occurred at that time. It becomes. In other words, there is a probability that the value will be significantly greater than the value of the minute pressure fluctuation that is caused by factors other than pulsation, such as temperature change and instrumental error, and a minute pressure change value of an error level. Extremely high. Therefore, among the measured pressure values measured over a predetermined number of times such as 25 times, for example, two sets of maximum and minimum values (Pmax-1 and Pmin-1) One set and one set of Pmax-2 and Pmin-2 are extracted, and the difference ΔP1, ΔP2 (ΔP1 = Pmax-1−) between the maximum value and the minimum value of each of the plurality of sets is extracted. Pmin−1, ΔP2 = Pmax−2−Pmin−2) are calculated, and the differences ΔP1 and ΔP2 are compared with a predetermined pulsation amplitude determination threshold value ΔPth, and a plurality of sets of differences ΔP1 and ΔP2 are calculated. However, if both are greater than or equal to the pulsation amplitude determination threshold value ΔPth, it can be determined that pulsation has occurred, and if it is less than the pulsation amplitude determination threshold value ΔPth, it can be determined that no pulsation has occurred.

  As described above, using the difference between the maximum value and the minimum value of each of the plurality of sets, it is determined that pulsation has occurred if each of the plurality of sets is equal to or greater than the pulsation amplitude determination threshold. The reason for this is that, as shown in an example in FIG. 10, if only a difference ΔPmax-min between a set of maximum value Pmax and minimum value Pmin is used, for example, no pulsation actually occurs, Even if the constant pressure value changes significantly during the number of measurements and becomes a constant high pressure value, it may be determined that there is pulsation, so avoid such erroneous determination. Because. In a state where pulsation occurs, generally, a plurality of sets of maximum and minimum values can be extracted from the pressure measurement values measured a plurality of times, and the plurality of sets of maximum and minimum values can be extracted. The difference ΔP1, ΔP2,... Has a high probability that it is greater than or equal to a significant pulsation amplitude determination threshold value ΔPth corresponding to the pulsation amplitude, but in the state where no pulsation occurs, the difference between the maximum value Pmax and the minimum value Pmin. This is because the difference ΔPmax-min is smaller than the significant pulsation amplitude determination threshold value ΔPth, and there are rarely a plurality of combinations of the maximum value and the minimum value. Theoretically, when there is no pulsation and there is no change in pressure in the middle, the pressure value can be considered to be constant. Therefore, all measured values are maximum value = minimum value, and ΔPmax− min = 0 or almost zero. Therefore, there is only one type of ΔPmax-min, and the value ΔPmax-min is extremely small or zero. Therefore, if this is not the case, that is, if there are differences ΔP 1, ΔP 2... Between a plurality of sets of maximum values and minimum values and they are larger than a significant ΔPth, it is determined that “pulsation occurs”. It can be done.

The frequency of pulsation is generally about several tens to several hundreds [Hz]. Therefore, the period is often on the order of 10 ⁻¹ to 10 ⁻² [seconds] (digits or scale). On the other hand, the measurement in the judgment mode is performed 25 times in 3 seconds, for example, if it is set to match the measurement rule used in a general NI meter. The average period is about 0.12 [seconds], which is about the same or an order of magnitude larger than the period of pulsation. Therefore, for example, the measurement rule used in the NI meter is set by measuring the pressure in a non-constant period by setting the period of the judgment mode to a value of about 3 seconds as in the measurement rule used in the NI meter. The pressure value can be measured without any deviation within the amplitude when pulsation occurs. Conversely, as shown in FIG. 11 as a comparative example, if the average period of pressure measurement is shorter by one or two digits than the period of pulsation, all the measurement timings in one determination mode period are all. All pressure measurement values within one judgment mode period, regardless of how the measurement period within the judgment mode period is changed at non-constant periods, if it falls within the half cycle of the higher or lower pulsation. Is likely to be biased only to the higher side or the lower side. Therefore, it is desirable that the average period of the pressure measurement is set to be a long period equal to or longer than the pulsation period that is expected to occur. Alternatively, it is desirable to set the entire measurement range (or the period during which the measurement in the determination mode is performed) to be a period of the order equal to or larger than one period of pulsation expected to occur.

  As described above, in the present embodiment, the fluid is a flammable gas, and the case where a gas pressure drop abnormality is detected by a gas meter that performs flow measurement using the gas as a measurement target has been described. It goes without saying that the application of the pressure-over-detecting device (and method) is not limited to a gas meter. In addition, the present invention can be applied as a device for detecting a pressure abnormality such as a liquid such as liquid fuel or a viscous substance, instead of a gas such as gas. Further, in addition to fluid flowing in a pipe line such as a conduction path or a pipe, the present invention can be applied to, for example, an outdoor atmosphere or a device that detects an abnormal pressure of a gas or liquid that is always stationary.

  Moreover, the pressure abnormality detection device according to the present embodiment can be applied to detecting an abnormal increase in pressure in addition to detecting the abnormal decrease in pressure as described above. In that case, it is needless to say that the determination logic opposite to the case of detecting the pressure drop abnormality as described above may be used. That is, as the threshold pressure PH-th, for example, a pressure value that may cause a dangerous state if the pressure further increases is set in advance, and the pressure value measured over a predetermined number of times. The average value Pm is compared with the threshold pressure PH-th, and when Pm ≧ PH-th, it can be determined that the pressure is abnormal. Alternatively, among the pressure values Pn measured over a predetermined total number of times of measurement, the number N of times that Pn has become equal to or greater than the threshold pressure PH-th is preliminarily set to a value equal to or greater than half the total number of measurements If it is equal to or more than a predetermined threshold number of times NH-th, it can be determined that the pressure rise is abnormal.

  Further, as a variation of a specific method of measurement at a non-constant period, in addition to what has been described in the present embodiment, for example, a combination of geometric sequence having a common ratio that is not an integer ratio, Furthermore, various variations such as combinations of a plurality of types of non-constant periods are possible.

  As described above, in the gas meter and the pulsation detection method according to the present embodiment, the fluid pressure is measured every non-constant period, not every same period, over a predetermined number of times. Even in the state in which the pulsation occurs, it is possible to measure the pressure value within the amplitude of the pulsation without deviation without measuring only the higher side or the lower side of the pulsation amplitude.

  Then, by calculating the average value of the pressures measured without deviation over a predetermined number of times in this way, it becomes possible to accurately estimate the central value of the pressure pulsation, and the calculated pressure When the average value is equal to or lower than the predetermined threshold pressure when compared with the predetermined threshold pressure, it is determined that an abnormal pressure drop has occurred in the fluid, and exceeds the predetermined threshold pressure. In this case, it is determined that the pressure drop abnormality has not occurred in the fluid, so even if there is a pulsation, the pressure drop abnormality does not occur without causing a measurement bias due to the pulsation. Can be detected with high reliability. Even when no pulsation occurs, the occurrence of a pressure drop abnormality can be detected with high reliability in the same manner as when the pulsation occurs (with good consistency in both cases).

  In addition, as a result of the measurement over a predetermined number of times, the number of times that a pressure equal to or lower than a predetermined threshold pressure is measured is equal to or greater than the threshold number of times set to more than half of all the measurement times In some cases, it is estimated that the center value of the pulsation amplitude of the fluid pressure is less than or equal to a predetermined threshold pressure, so it is determined that a pressure drop abnormality has occurred in the fluid, and conversely, If the number of times is less than the predetermined threshold number, it is estimated that the center value of the pulsation amplitude of the fluid pressure is greater than the predetermined threshold pressure. Even if pulsation occurs, the occurrence of pressure drop abnormality can be detected with high reliability without being adversely affected by measurement bias caused by the pulsation. Can do. Further, even when no pulsation occurs, the occurrence of a pressure drop abnormality can be detected with high reliability in the same manner as when pulsation occurs (good consistency with or without pulsation).

  Note that the pressure is measured for a predetermined period at a frequency equal to or higher than the maximum frequency of pulsation, and the average value of the measured pressures, for example, several wavelengths to several tens of wavelengths or more, is calculated and compared with a threshold value. Thus, a detection method of determining whether or not to perform blocking is also possible. However, in this case, the pressure can be measured at an extremely high speed, the memory capacity for storing the measured pressure value data is sufficient, and such a large amount of data can be processed in a short time. It is required for a gas meter (such as a microcomputer built in) to have a calculation speed.

  More specifically, when a pressure drop (for example, 85 mmH 2 O) is first detected, there is a frequency that is statistically or heuristically expected to occur (there is a measurement system performance constraint, etc.). The higher the frequency, the more desirable; for example, several hundreds [Hz] or more), and pressure measurement is performed at equal intervals over, for example, 3 seconds. An average value of all the measured pressure values is calculated. And the pressure average value and a threshold value are compared, and it is determined whether interruption | blocking is performed.

  Alternatively, as a variation of the above detection method, the following is also possible. That is, the gas pressure is measured at a normal time when a pressure drop or a large pressure fluctuation is not detected. At this time, it is assumed that the pressure fluctuation is almost zero or a minute value close to it. Therefore, if the measurement value (data) is stored or measured at this time, for example, 10 to several tens of times. Good. When a pressure drop is detected, pressure measurement is performed for a predetermined number of times n at a random frequency. The variance V (P) for all of the measured n pressure measurements P is calculated. And when the dispersion | distribution becomes more than the predetermined threshold value Vth, it determines with the pulsation or supply pressure fluctuation | variation having generate | occur | produced. For example, the case where the measurement result as shown in FIG. 12 is obtained will be described. When the pressure fluctuation is relatively small (195 ≦ P ≦ 210) as shown in FIG. In this case, the variance is V (P) = 22.5. On the other hand, when the pressure fluctuation is relatively large as shown in FIG. 12B (40 ≦ P ≦ 290), the dispersion is V (P) = 6494.7 when n = 10. Based on such a value of the variance V (P), it is possible to determine whether or not pulsation or supply pressure fluctuation has occurred. Here, the total number n of the pressure measurements is not limited to being fixed to the predetermined number as described above. That is, the variance V (P) may be calculated by changing the value of n based on the calculated V (P). For example, if V (P) ≦ 1, n = 10 samples are used (for example, 10 pressure measurements are extracted from all data), and if 1 <V (P) ≦ 100, n = 100 samples are used, and if 100 <V (P), n = 1000 samples are used to obtain highly reliable dispersion even with a relatively small number of samples (number of measurements), and highly reliable pulsation Alternatively, it is possible to determine the presence or absence of pressure fluctuation.

  Alternatively, as a further variation, as the pulsation assumed corresponding to the variance calculated based on the pressure measurement value is non-stationary and difficult to determine, it is fed back to the measurement and the total number n of pressure measurements is increased. It is also possible to make it happen. As a specific example, when a pressure drop of a predetermined value or more is detected, first, n = 10 (the total number of measurements is 10), and the variance V (P) of the pressure measurement values is calculated. When the calculated dispersion value becomes V (P) ≦ 1, the pressure measurement value V (P) measured with n = 10 is used. Alternatively, when 1 <V (P) ≦ 100, reset to n = 100, perform 100 measurements, recalculate V (P) using the measured value, and The pressure fluctuation is judged using the value. Alternatively, if 100 <V (P), reset to n = 1000, perform 1000 measurements, recalculate V (P) using the measured value, and use that value. Determine the pressure fluctuation. In this way, it is possible to obtain highly reliable dispersion even with a relatively small number of samples (number of measurements), and to determine the presence or absence of highly reliable pulsation or pressure fluctuation. In addition, when the pulsation is unsteady and there is a high tendency for accurate judgment of blockage, the number of measurements is increased, but when the necessity is low, it can be done with a small number of measurements, so it is always useless. Power consumption can be suppressed. When the above dispersion V (P) shows an extremely large value, the gas conduction may be shut off by closing the shutoff valve in order to avoid strong pressure fluctuation and pulsation regardless of the average pressure. desirable.

It is a figure showing the schematic structure of the gas meter which incorporated the pressure abnormality detection apparatus which concerns on one embodiment of this invention. It is the figure which represented typically an example of the pressure measurement timing in the case of performing a pressure measurement by a non-constant period (random period) over 25 times in the state where the pulsation generate | occur | produced. It is a figure showing an example at the time of performing a pressure measurement by the non-constant period containing a certain period and the period of the odd multiple of the period of the half. It is a figure showing the flow of the main operation | movement in the pressure drop abnormality detection apparatus which concerns on this Embodiment centering on a 1st determination method. It is the figure which represented typically an example of the dispersion | distribution state of a pressure measurement value when a pressure is measured with a non-constant period at the time of pulsation generation | occurrence | production in the pressure abnormality detection apparatus and pressure abnormality detection method which concern on this Embodiment. FIG. 6 is a diagram schematically showing a case where the center value P0 of fixed periodic pulsation with an amplitude A is deviated by a pressure S (lower pressure) to a lower pressure side than the threshold pressure PL-th. is there. It is a figure showing the flow of the main operation | movement in the pressure drop abnormality detection apparatus which concerns on this Embodiment centering on a 2nd determination method. It is a figure showing the flow of the main operation | movement in the case of performing determination except the maximum value and the minimum value in the flow of the 2nd determination method shown in FIG. Using Pi, which is a value obtained by excluding a large value from the maximum value to the m-th and a small value from the minimum value to the m-th, it is determined whether Pi ≦ PL-th directly. It is a figure showing the flow of the main operation | movement when performing. It is a figure showing an example of difference (DELTA) Pmax-min of a set of maximum value Pmax and minimum value Pmin measured in the state without a pulsation. As a comparative example, it is a figure showing about an example in case the average period of a pressure measurement is a short period one digit thru | or two digits smaller than the period of a pulsation. It is a figure showing an example of the pressure measurement result in the experiment which performed interception judgment using dispersion of a pressure measurement value.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Flow measuring device, 200 ... Shut-off valve device, 300 ... Pressure abnormality detection device, 400 ... Information storage device, 500 ... Display device, 301 ... Pressure sensor, 302 ... A / D converter, 303 ... Pressure value calculating part, 304 ... Pressure drop abnormality determination unit, 305 ... Control law storage unit, 306 ... Control unit

Claims (28)

Pressure measuring means for measuring the pressure of the fluid;
Pressure measurement control means for controlling the measurement by the pressure measurement means so as to measure the pressure of the fluid every non-constant period over a predetermined number of times;
Pressure abnormality determination detection means for determining that a pressure drop abnormality has occurred in the fluid when the average value of the pressure measured over the predetermined number of times is equal to or less than a predetermined threshold pressure. A pressure abnormality detection device characterized by that. Pressure measuring means for measuring the pressure of the fluid;
Pressure measurement control means for controlling the measurement by the pressure measurement means so as to measure the pressure of the fluid every non-constant period over a predetermined number of times;
As a result of the pressure measurement over the predetermined number of times, when the number of times the pressure equal to or lower than the predetermined threshold pressure is measured is equal to or higher than the predetermined threshold number of times, the pressure is applied to the fluid. A pressure abnormality detection device comprising pressure abnormality determination means for determining that a decrease abnormality has occurred. The pressure abnormality detection device according to claim 2, wherein the threshold number of times in the pressure abnormality determination means is set to a number between half or all of the predetermined number of times. The pressure measurement control means controls the measurement by the pressure measurement means so as to measure the pressure of the fluid in a random cycle without repeating the same cycle over the predetermined number of times. Item 4. The pressure abnormality detection device according to any one of Items 1 to 3. Measurement by the pressure measurement means so that the pressure measurement control means measures the pressure of the fluid in a non-constant period including a certain period and a period that is an odd multiple of the half period over the predetermined number of times. The pressure abnormality detection device according to any one of claims 1 to 4, wherein the pressure abnormality detection device is controlled. The pressure abnormality determining means determines the occurrence of an abnormal pressure drop of the fluid based on the remaining measured values obtained by removing the maximum value and the minimum value from the measured pressure values measured over the predetermined number of times. The pressure abnormality detection device according to any one of claims 1 to 5, wherein: The pressure measurement control means measures the pressure of the fluid over the predetermined number of times in the first monitoring period, and based on the pressure measured in the first monitoring period, the pressure abnormality determination means However, if the fluid pressure drop abnormality is tentatively determined, and the tentative determination indicates that the fluid has a pressure drop abnormality, the pressure measurement control means further includes a second In the monitoring period, the pressure of the fluid is measured for a predetermined number of times, and the pressure abnormality determining means determines whether the fluid pressure drop abnormality has occurred based on the pressure measured in the second monitoring period. The pressure abnormality detection device according to any one of claims 1 to 6, wherein final determination of presence or absence is performed. The pressure abnormality determining means has no pressure drop abnormality in the fluid when the average value of the pressure measured in the second monitoring period exceeds a predetermined threshold pressure, or 8. It is determined that the fluid has returned to normal during the second monitoring period, and when the pressure is equal to or lower than a predetermined threshold pressure, it is determined that a pressure drop abnormality has occurred in the fluid. The pressure abnormality detection device described. The pressure abnormality determining means has a predetermined threshold as the number of times a pressure exceeding a predetermined threshold pressure is measured as a result of pressure measurement over a predetermined number of times in the second monitoring period. When the number of times is greater than or equal to the number of times, it is determined that no abnormality in pressure drop has occurred in the fluid or that the fluid has returned to normal during the second monitoring period. The pressure abnormality detection device according to claim 7, wherein it is determined that a pressure drop abnormality has occurred in the fluid. When the pressure of the fluid exceeds the predetermined threshold pressure, the pressure measurement control means measures the pressure of the fluid at a period longer than the non-constant period as a normal monitoring mode, and When the pressure is equal to or lower than the predetermined threshold pressure, the pressure of the fluid is measured every non-constant period as the determination mode for the predetermined number of times, and the fluid is determined based on the measurement result. When the pressure abnormality determination detecting means determines that no pressure drop abnormality has occurred, the measurement by the pressure measuring means is controlled so as to cancel the determination mode and return to the normal monitoring mode. The pressure abnormality detection device according to any one of claims 1 to 9. Extracting a plurality of sets of maximum and minimum values from the measured pressure values measured over the predetermined number of times, calculating a difference between each of the plurality of sets of maximum and minimum values, The difference is compared with a predetermined pulsation amplitude determination threshold, and if each of the plurality of sets is equal to or greater than the pulsation amplitude determination threshold, it is determined that pulsation has occurred, and the pulsation amplitude determination The pressure abnormality detection device according to any one of claims 1 to 10, further comprising a pulsation occurrence determination unit that determines that pulsation does not occur when the value is less than the threshold value. The dispersion of the pressure measured over the predetermined number of times is calculated, and the dispersion is compared with a predetermined threshold value. When the dispersion is equal to or greater than the threshold value, pulsation occurs in the fluid. 11. A pulsation occurrence determination means for determining that no pulsation has occurred and determining that no pulsation has occurred when the variance is less than the threshold value. The pressure abnormality detection device described in 1. The fluid is a combustible gas, and the pressure measuring means, the pressure measurement control means, and the pressure abnormality determination detecting means are connected to a pipe and are used in a gas meter for measuring the flow rate of the gas flowing through the pipe. The pressure abnormality detection device according to any one of claims 1 to 12, wherein the pressure abnormality of the gas is detected by the gas meter. The gas meter is provided with a shutoff valve for shutting off the gas conduction, and when the pressure abnormality judging means determines that the pressure drop abnormality has occurred in the gas, the shutoff valve is closed and the gas is shut off. The pressure abnormality detection device according to claim 13, wherein the electrical conduction is interrupted. When the pressure of the fluid is measured every non-constant period over a predetermined number of times, and the average value of the pressure measured over the predetermined number of times is less than or equal to a predetermined threshold pressure, A pressure abnormality detection method comprising: determining that a pressure drop abnormality has occurred, and determining that a pressure drop abnormality has not occurred in the fluid when a predetermined threshold pressure is exceeded. The number of times the pressure of the fluid is measured every non-constant period over a predetermined number of times, and the pressure measured below the predetermined threshold pressure as a result of the measurement over the predetermined number of times is the predetermined threshold number of times. When the number of times is equal to or greater than that, it is determined that a pressure drop abnormality has occurred in the fluid. When the number of times is less than a predetermined threshold number, the fluid has no pressure drop abnormality. A method for detecting pressure abnormality, characterized in that it is determined as a thing. The pressure abnormality detection method according to claim 16, wherein the threshold number of times is set to a number between half or all of the predetermined number of times. The pressure abnormality detection method according to any one of claims 15 to 17, wherein the pressure of the fluid is measured at a random cycle without repeating the same cycle over the predetermined number of times. The pressure of the fluid is measured at a non-constant period including a certain period and a period that is an odd multiple of the half period over the predetermined number of times. The pressure abnormality detection method described in 1. The occurrence of pressure drop abnormality of the fluid is determined based on the remaining measurement values obtained by removing the maximum value and the minimum value from the pressure measurement values measured over the predetermined number of times. The pressure abnormality detection method according to any one of claims 15 to 19. In the first monitoring period, the pressure of the fluid is measured over the predetermined number of times, and based on the pressure measured in the first monitoring period, whether or not an abnormality in the pressure drop of the fluid has occurred is temporarily determined. And when it is temporarily determined that the fluid has a pressure drop abnormality in the temporary determination, the fluid pressure is measured a predetermined number of times in the second monitoring period, and the first 21. The pressure according to any one of claims 15 to 20, wherein a final determination is made as to whether or not a fluid pressure drop abnormality has occurred based on the pressure measured in the monitoring period of 2. Anomaly detection method. When the average value of the pressure measured in the second monitoring period exceeds a predetermined threshold pressure, no abnormal pressure drop has occurred in the fluid or during the second monitoring period The pressure abnormality detection method according to claim 21, wherein it is determined that the fluid has returned to normal, and when the pressure is equal to or lower than a predetermined threshold pressure, it is determined that a pressure drop abnormality has occurred in the fluid. When the pressure measurement over the predetermined number of times in the second monitoring period results in the number of times the pressure exceeding the predetermined threshold pressure is measured being equal to or greater than the predetermined threshold number Is determined that the fluid does not have a pressure drop abnormality or has returned to normal during the second monitoring period, and if the fluid is less than a predetermined threshold number of times, The pressure abnormality detection method according to claim 21, wherein it is determined that a drop abnormality has occurred. When the fluid pressure exceeds the predetermined threshold pressure, the fluid pressure is measured in a period longer than the non-constant period as a normal monitoring mode, and the fluid pressure is the predetermined threshold value. When the pressure is less than or equal to the value pressure, the pressure of the fluid is measured at the non-constant period for the predetermined number of times as a determination mode, and the occurrence of a pressure drop abnormality in the fluid is determined based on the measurement result. The pressure abnormality detection method according to any one of claims 15 to 23, wherein when it is determined that there is not, the determination mode is canceled and the normal monitoring mode is resumed. Extracting a plurality of sets of maximum and minimum values from the measured pressure values measured over the predetermined number of times, calculating a difference between each of the plurality of sets of maximum and minimum values, The difference is compared with a predetermined pulsation amplitude determination threshold, and if each of the plurality of sets is equal to or greater than the pulsation amplitude determination threshold, it is determined that pulsation has occurred, and the pulsation amplitude determination The pressure abnormality detection method according to any one of claims 15 to 24, wherein it is determined that no pulsation occurs when the value is less than the threshold value. The dispersion of the pressure measured over the predetermined number of times is calculated, and the dispersion is compared with a predetermined threshold value. When the dispersion is equal to or greater than the threshold value, pulsation occurs in the fluid. 25. A pulsation occurrence determination means for determining that no pulsation has occurred and determining that no pulsation has occurred when the variance is less than the threshold value. The pressure abnormality detection method according to item. 27. Any one of claims 15 to 26, wherein the fluid is a flammable gas, and the occurrence of an abnormal pressure of the gas is detected by a gas meter that performs flow rate measurement using the gas as a measurement target. The pressure abnormality detection method described in 1. The gas meter is provided with a shut-off valve for shutting off the gas conduction, and when it is determined that an abnormal pressure drop has occurred in the gas, the gas shut-off valve is closed to shut off the gas conduction. The pressure abnormality detection method according to claim 27.

Images