JP2015014568A - Ultrasonic gas meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic gas meter capable of suppressing erroneous determination in the case of determining the occurrence of dew condensation.SOLUTION: An ultrasonic gas meter includes: acoustic transducers TD1 and TD2 for intermittently transmitting an ultrasonic signal to the inside of a gas channel, and for receiving the ultrasonic signal; an amplifier 43a for amplifying the signal received by the acoustic transducers TD1 and TD2 until predetermined strength; and a CPU 44 for monitoring the degree of amplification in each predetermined time, and for, when the degree of amplification changes by a predetermined value or more from an initial value, determining that dew condensation occurs in the gas channel, and for determining the unused state of gas. In this case, when determining the unused state of gas, the CPU 44 does not determine whether or not the dew condensation occurs in the gas channel.

Description

  The present invention relates to an ultrasonic gas meter.

  Conventionally, an ultrasonic gas meter using an ultrasonic flow velocity sensor has been proposed. The ultrasonic gas meter constitutes an ultrasonic flow rate sensor by two acoustic transducers composed of, for example, piezoelectric vibrators that operate at an ultrasonic frequency and are spaced apart from each other within a gas flow path. Then, the ultrasonic signal generated by one transducer is received by the other transducer to measure the propagation time during which the ultrasonic signal propagates between the transducers, and the gas flow rate is intermittent based on the measured propagation time. Ask for.

  In this type of ultrasonic gas meter, if condensation occurs on the surface of the sensor or the protection member, there is a problem that the instrumental difference changes and the gas flow rate cannot be detected accurately. Thus, for example, Patent Document 1 discloses an ultrasonic gas meter that determines condensation based on the amplification degree of a sensor signal.

JP 2011-17543 A

  By the way, when the gas stopper upstream of the gas meter is closed and no gas is used for a long time, mixed gas or negative pressure is generated. When mixed gas or negative pressure is generated, the degree of amplification changes. Therefore, there is a possibility that it is erroneously determined that condensation occurs even in a situation where condensation does not occur. Here, the mixed gas is generated when air is mixed due to a breathing action due to poor airtightness such as a gas appliance, a gas hose, and each connection portion downstream of the gas meter, or when an air purge is not performed when a new gas meter is attached. On the other hand, the negative pressure is generated when a temperature change occurs in a closed state where the gas stopper upstream of the gas meter is closed, or by adsorption or permeation to the gas hose.

  This invention is made | formed in view of this situation, The objective is to suppress the misjudgment in the generation | occurrence | production determination of dew condensation.

  In order to solve such a problem, the present invention provides a transmitting means for intermittently transmitting an ultrasonic signal in a gas flow path, a receiving means for receiving an ultrasonic signal, and a signal received by the receiving means as a predetermined signal. Amplifying means for amplifying to the strength and the amplification degree by the amplifying means are monitored every predetermined time, and when the monitored amplification degree changes by a predetermined value or more than the initial value, it is determined that condensation has occurred in the gas flow path. Dew condensation determining means, and a state determining means for determining the unused state of the gas. When the state determining means determines the unused state of the gas, the dew condensation determining means condenses in the gas flow path. An ultrasonic gas meter is provided that does not execute a determination as to whether or not the gas is generated.

  Here, in the present invention, it is preferable that the state determination means determines the unused state of the gas when the gas cutoff valve is in a closed state in which the gas flow in the gas flow path is stopped.

  Further, in the present invention, it further includes pressure detection means for detecting the pressure in the gas flow path, and the state determination means is in an unused state of the gas when the pressure detected by the pressure detection means is outside a predetermined range. Is preferably determined.

  The present invention may further include a flow rate measuring unit that measures the flow rate of the gas flowing in the gas flow path based on the propagation time of the ultrasonic signal transmitted from the transmitting unit and received by the receiving unit. Good. In this case, the state determining means periodically samples the integrated flow value obtained by integrating the flow measured by the flow measuring means, and the difference between the currently sampled integrated flow value and the integrated flow value sampled before a predetermined period is predetermined. If it is smaller than the determination value, it is preferable to determine the unused state of the gas.

  In the present invention, it is preferable that the dew condensation determination means disables the dew condensation determination function when the operation mode is the shipping mode.

  In addition, the present invention may further include a pressure detection unit that detects a pressure in the gas flow path. In this case, it is preferable that the dew condensation determination unit disables the dew condensation determination function when determining an abnormality in the pressure detected by the pressure detection unit.

  When the gas is not used, a mixed gas or negative pressure tends to be generated. When the mixed gas or negative pressure is generated, the amplification degree is changed. Therefore, by not performing the determination of the occurrence of condensation when the gas is unused, the possibility of erroneous determination in the determination of occurrence of condensation can be reduced.

Configuration diagram of a gas supply system including an ultrasonic gas meter according to the present embodiment The block diagram which shows the ultrasonic type gas meter which concerns on this embodiment Configuration diagram showing the inside of μCOM shown in FIG. The flowchart which shows the setting procedure of the reference | standard amplification in the generation | occurrence | production determination of the dew condensation of the ultrasonic type gas meter which concerns on this embodiment. The flowchart which shows generation | occurrence | production determination of the dew condensation of the ultrasonic type gas meter which concerns on this embodiment The flowchart which shows the update procedure of the reference | standard amplification in the generation | occurrence | production determination of the dew condensation of the ultrasonic type gas meter which concerns on this embodiment. The flowchart which shows the process sequence for invalidating the dew condensation judgment function with which the ultrasonic gas meter which concerns on this embodiment is equipped.

  FIG. 1 is a configuration diagram of a gas supply system 1 including an ultrasonic gas meter 40 according to the present embodiment. The gas supply system 1 supplies fuel gas to each gas appliance 10, and includes a plurality of gas appliances 10, pipes 31 and 32, and an ultrasonic gas meter 40.

  The upstream piping 31 connects the gas supply source and the ultrasonic gas meter 40. The downstream pipe 32 is a pipe that connects the ultrasonic gas meter 40 and the gas appliance 10. The ultrasonic gas meter 40 obtains the gas flow rate based on the propagation time of the ultrasonic signal and integrates and displays the obtained gas flow rate. In such a gas supply system 1, a gas flow path connected to the upstream pipe 31 and the downstream pipe 32 is formed in the ultrasonic gas meter 40, and the fuel gas is sent from the upstream pipe 31 to the ultrasonic gas meter 40, And the gas appliance 10 is reached through the downstream pipe 32 and burned in the gas appliance 10.

  In the gas supply system 1, there is a possibility that water W may accumulate in the upstream pipe 31 due to a crack or the like of the upstream pipe 31. When the water W accumulates in the upstream pipe 31, a gas containing a large amount of water vapor is supplied to the ultrasonic gas meter 40, and condensation occurs in which water adheres to the surface of the ultrasonic flow sensor or a protective member such as a mesh. As a result, the instrumental error may change. If the instrumental difference changes, the gas flow rate cannot be detected accurately, causing a problem with charges.

  Therefore, the ultrasonic gas meter 40 according to the present embodiment is configured to be able to determine condensation. FIG. 2 is a configuration diagram illustrating the ultrasonic gas meter 40 according to the present embodiment. The ultrasonic gas meter 40 shown in the figure includes two acoustic transducers (which are separated from each other by a distance L in the gas flow path and are opposed to each other so as to form an angle θ with respect to the gas flow direction Y). (Transmission means, reception means) TD1, TD2.

  The two acoustic transducers TD1, TD2 are composed of, for example, piezoelectric vibrators that operate at an ultrasonic frequency. The gas flow path is provided with a gas shut-off valve 47 that shuts off the gas flow path by closing the valve upstream of both acoustic transducers TD1 and TD2.

  Each transducer TD1, TD2 is connected to a transmission circuit 42 and a reception circuit 43 via transducer interface (I / F) circuits 41a, 41b, respectively. The transmission circuit 42 intermittently transmits a signal for generating an ultrasonic signal by driving one of the transducers TD 1 and TD 2 under the control of the microcomputer (μCOM) 44. For this reason, the transducers TD1, TD2 intermittently transmit and receive ultrasonic signals from both the upstream side and the downstream side with respect to the gas flow direction Y.

  The receiving circuit 43 includes an amplifier (amplifying means) 43a that receives signals from the other transducers TD1 and TD2 that have received the ultrasonic signal that has passed through the gas flow path and amplifies the ultrasonic signal to a predetermined strength. Yes. The amplification degree of the amplifier 43 a can be adjusted by the μCOM 44. Further, the display unit 45 is connected to the μCOM 44.

  A plurality of partition plates 46 are provided in the flow path in which the transducers TD1 and TD2 are provided. The plurality of partition plates 46 prevent the generation of vortices during gas inflow and contribute to accurate flow rate measurement. In FIG. 2, the partition plate 46 and the ultrasonic signal transmission / reception direction are illustrated so as to intersect with each other. However, the two are actually in a parallel relationship so that the partition plate 46 does not hinder the transmission / reception of the ultrasonic signal. Is installed.

  Further, the ultrasonic gas meter 40 includes a changeover switch 48. The changeover switch 48 can switch the validity / invalidity of a dew condensation determination function described later. The ultrasonic gas meter 40 is provided with a pressure sensor 49 that detects the pressure in the gas flow path.

  FIG. 3 is a block diagram showing the inside of the μCOM 44 shown in FIG. As shown in FIG. 3, the μCOM 44 includes a central processing unit (CPU) 44a that performs various processes according to a program, a ROM 44b that is a read-only memory that stores a program for processing performed by the CPU 44a, and various types of CPU 44a. A RAM 44c, which is a readable / writable memory having a work area used in the processing process and a data storage area for storing various data, is incorporated. These are connected to each other by a bus line 44d.

  The CPU 44a measures the gas flow rate based on the propagation times of the ultrasonic signals transmitted and received by the two transducers TD1 and TD2 every sampling time, and instantaneously multiplies the measured gas flow rate by the cross-sectional area of the gas flow path. A flow rate measuring function (flow rate measuring means) for measuring the flow rate is provided. The sampling time is, for example, 2 seconds. The CPU 44a also has a function of calculating an integrated flow value that is an integrated value of the measured instantaneous flow rate.

  Further, the CPU 44a monitors the amplification degree by the amplifier 43a every predetermined time (for example, 24 hours), and when the monitored amplification degree changes by a predetermined value (for example, “10”) or more from the initial value, the CPU 44a enters the gas flow path. It has a condensation determination function (condensation determination means) for determining that condensation has occurred. Here, when condensation occurs, the ultrasonic signal is refracted or attenuated due to the influence of water droplets or the like, and the amplification degree tends to change (increase). Therefore, when the amplification degree changes by a predetermined value or more than the reference amplification level that is the reference value, it can be determined that condensation has occurred in the gas flow path. Note that the reference amplification degree is a value that is set prior to the determination of the occurrence of condensation and is updated as necessary.

  Further, the CPU 44a does not determine whether or not condensation has occurred in the gas flow path when the following three cases are applicable.

  The first is a case where the sum of the propagation time of the ultrasonic signal transmitted and received from the upstream side and the propagation time of the ultrasonic signal transmitted and received from the downstream side is outside a predetermined range. Here, the sum of the propagation times from the upstream side and the downstream side tends to change depending on the gas type without being affected by the flow velocity. For example, even if the flow velocity increases and the ultrasonic signal from the upstream side is received early, the ultrasonic signal from the downstream side is received later, resulting in the influence of the flow velocity. Without being received, the sum of propagation times does not change much. Therefore, the sum of propagation times does not change according to the flow velocity. On the other hand, the sum of propagation times tends to change depending on the gas type. Therefore, the case where the sum of the propagation times is out of the predetermined range can be said to be a case where the gas type to be measured has changed or a mixed gas state has occurred. When the gas type is changed or in a mixed gas state, the amplification degree tends to change, and an error is likely to occur in the determination of the occurrence of condensation. Therefore, the CPU 44a does not execute the determination of the occurrence of condensation when the sum of the propagation times is out of the predetermined range.

  The second is a case where the flow rate measured by the flow rate measurement function exceeds a predetermined flow rate. Here, when the flow rate exceeds a predetermined flow rate (for example, 1000 L / h), drift and vortex flow are generated in the flow path, and the amplification degree tends to be unstable. For this reason, an error is likely to occur in the determination of the occurrence of condensation. Therefore, the CPU 44a does not execute the determination of the occurrence of condensation when the flow rate exceeds the predetermined flow rate.

  The third is a case where the unused state of the gas is determined. Here, when a mixed gas or a negative pressure is generated, the amplification degree is changed, so that an error is easily caused in the determination of the occurrence of condensation. Moreover, mixed gas and negative pressure generate | occur | produce in the unused state of gas. Therefore, the CPU 44a does not determine the occurrence of condensation when the gas is not used. Further, as a premise for making such a determination, the CPU 44a has a function (state determination means) for determining an unused state of gas.

  The determination of the unused state of gas is executed by combining any one or a plurality of the following three methods. Since the gas appliance 10 is used for a limited time in one day, the unused state of gas means that the gas that is not actually used is not used for a short period of time. It is said that the gas is not constantly used over a long period of time.

  When the gas shut-off valve 47 is in a closed state that stops the gas flow in the gas flow path, the gas supply is shut off. Therefore, the gas cannot be used until the gas shut-off valve 47 returns to the open state. Therefore, the CPU 44a determines that the gas is not in use when the gas shut-off valve 47 is closed. The determination of the gas supply cutoff is not limited to the gas cutoff valve 47 provided in the ultrasonic gas meter 40, and may be another cutoff valve that can be in a gas unused state.

  Further, if the gas is in a usable state or usable state, the pressure of the gas flow path detected by the pressure sensor 49 is within a predetermined pressure range (hereinafter referred to as “normal range”). Therefore, the CPU 44a determines that the gas is not used when the pressure of the gas flow path is outside the normal range.

  Furthermore, the integrated flow rate value, which is the integrated value of the instantaneous flow rate that is measured, increases as the gas is used. Therefore, when the gas is used, a difference equal to or greater than a predetermined determination value is generated between two integrated flow rate values obtained with a certain period. Therefore, the CPU 44a periodically samples the integrated flow rate value, and determines that the gas is not used when the difference from the integrated flow rate value sampled before the predetermined period does not exceed a predetermined determination value.

  In the present embodiment, the CPU 44a has an update function. The update function is a function for updating the reference amplification degree. For example, the amplification degree by the amplifier 43 a tends to change according to the ambient temperature of the ultrasonic gas meter 40. Similarly, the amplification degree tends to change when dust adheres to the surfaces of the transducers TD1 and TD2 and their protective members. In such a case, even if condensation does not occur, the amplification degree changes, and there is a possibility that the condensation is erroneously determined. Therefore, the determination of the occurrence of condensation is appropriately performed by updating the reference amplification degree.

  Further, the CPU 44a enables or disables the dew condensation determination function according to the switch signal from the changeover switch 48. In other words, when the changeover switch 48 is set to the valid side, the CPU 44a validates the condensation determination function and executes the determination of the occurrence of condensation. When the changeover switch 48 is set to the invalid side, the CPU 44a Disables the judgment function and does not execute the judgment on the occurrence of condensation.

  FIG. 4 is a flowchart showing a reference amplification degree setting procedure in the determination of the occurrence of condensation in the ultrasonic gas meter 40 according to the present embodiment. First, in step 10 (S10), the CPU 44a measures the propagation time and calculates the gas flow rate. Specifically, the CPU 44a controls the transducers TD1 and TD2 through the transmission circuit 42, whereby the transducers TD1 and TD2 intermittently transmit ultrasonic signals. Next, the amplifier 43a amplifies the ultrasonic signals received by the transducers TD1 and TD2 to a predetermined level according to the amplification degree adjusted by the μCOM 44, and outputs this to the μCOM 44. Then, the CPU 44a measures the propagation time of the transducers TD1 and TD2. Thereafter, the CPU 44a calculates the gas flow rate from the propagation time, and calculates the gas flow rate from the gas flow rate and the flow path diameter.

  In step 11 (S11), the CPU 44a determines whether or not a predetermined time has elapsed. If the predetermined time has not elapsed, a negative determination is made in step 11, and the process returns to step 10. On the other hand, if the predetermined time has elapsed, an affirmative determination is made in step 11, so the process proceeds to step 12 (S 12).

  In step 12, the CPU 44a determines whether or not the changeover switch 48 is set to the effective side. If the changeover switch 48 is set to the invalid side, a negative determination is made in step 12, and the process returns to step 10. On the other hand, if the changeover switch 48 is set to the effective side, an affirmative determination is made in step 12, and the process proceeds to step 13 (S13).

  In step 13, the CPU 44a determines whether or not the sum of propagation times is within a predetermined range. If the sum of the propagation times is outside the predetermined range, a negative determination is made in step 13. As a result, the processing returns to the step 10 without setting the reference amplification degree described later. On the other hand, if the sum of the propagation times is within the predetermined range, an affirmative determination is made in step 13, and the process proceeds to step 14 (S14).

  In step 14, the CPU 44a determines whether or not the calculated flow rate is equal to or less than a predetermined flow rate. If the calculated flow rate is greater than the predetermined flow rate, a negative determination is made in step 14. As a result, the processing returns to the step 10 without setting the reference amplification degree described later. On the other hand, if the calculated flow rate is less than or equal to the predetermined flow rate, an affirmative determination is made in step 14, and thus the process proceeds to step 15 (S15).

  In step 15, the CPU 44a determines whether or not the gas cutoff valve 47 is open. If the gas cutoff valve 47 is in the closed state, a negative determination is made in step 15. That is, in the case where the unused state of the gas is determined, the process returns to step 10 without setting the reference amplification level described later so as to prevent an incorrect value from being reflected in the reference amplification level. On the other hand, when the gas shut-off valve 47 is in the open state, an affirmative determination is made in step 15, and thus the process proceeds to step 16 (S 16).

  In step 16, the CPU 44a determines whether or not the pressure of the gas flow path detected by the pressure sensor 49 is within a normal range. If the detected pressure of the gas flow path is outside the normal range, a negative determination is made in step 16. That is, in the case where the unused state of the gas is determined, the process returns to step 10 without setting the reference amplification level described later so as to prevent an incorrect value from being reflected in the reference amplification level. On the other hand, if the detected pressure of the gas flow path is within the predetermined range, an affirmative determination is made in step 16, and thus the process proceeds to step 17 (S17).

  In step 17, the CPU 44a determines whether or not the difference between the current integrated flow value and the integrated flow value before a predetermined period is equal to or greater than a predetermined determination value. If the difference between the integrated flow values is smaller than the determination value, a negative determination is made in step 17. That is, in the case where the unused state of the gas is determined, the process returns to step 10 without setting the reference amplification level described later so as to prevent an incorrect value from being reflected in the reference amplification level. On the other hand, if the difference between the integrated flow values is greater than or equal to the determination value, an affirmative determination is made in step 17, and the process proceeds to step 18 (S18).

  In step 18, the CPU 44a sets the amplification used in step 10 as the reference amplification.

  FIG. 5 is a flowchart showing the determination of the occurrence of condensation in the ultrasonic gas meter 40 according to this embodiment. First, in step 20 (S20), the CPU 44a determines whether a specified time has elapsed. The specified time corresponds to the execution cycle of the determination of occurrence of condensation, and is, for example, 2 seconds. If an affirmative determination is made in step 20, that is, if the specified time has elapsed, the process proceeds to step 21 (S21). On the other hand, if a negative determination is made in step 20, that is, if the specified time has not elapsed, the process of step 20 is performed again.

  In step 21, the CPU 44a measures the propagation time and calculates the gas flow rate. Specifically, the CPU 44a controls the transducers TD1 and TD2 through the transmission circuit 42, whereby the transducers TD1 and TD2 intermittently transmit ultrasonic signals. Next, the amplifier 43a amplifies the ultrasonic signals received by the transducers TD1 and TD2 to a predetermined level according to the amplification degree adjusted by the μCOM 44, and outputs this to the μCOM 44. Then, the CPU 44a measures the propagation time of the transducers TD1 and TD2. Thereafter, the CPU 44a calculates the gas flow rate from the propagation time, and calculates the gas flow rate from the gas flow rate and the flow path diameter.

  In each process from step 22 (S22) to step 25 (S25), the CPU 44a determines whether or not an execution condition for determining the occurrence of condensation is satisfied. Here, each process from step 22 to step 25 corresponds to each process from step 11 to step 14 in the reference amplification degree setting process described above. Therefore, when the predetermined time has elapsed (negative determination at step 22), when the changeover switch 48 is set to the effective side (negative determination at step 23 (S23)), and when the sum of propagation times is outside the predetermined range If the calculated flow rate is larger than the predetermined flow rate (negative determination in step 25), the process returns to step 20 without determining the occurrence of condensation.

  In step 26 (S26), the CPU 44a determines the occurrence of condensation. Specifically, the CPU 44a determines whether or not the amplification used in step 20 has changed by a predetermined value or more from the reference amplification. If the amplification degree has not changed by a predetermined value or more from the reference amplification degree, a negative determination is made in step 26 and the process returns to step 20. On the other hand, when the amplification degree changes by a predetermined value or more from the reference amplification degree, an affirmative determination is made at step 26. That is, if there is a possibility of condensation, the process proceeds to step 27 (S27).

  In each process from step 27 to step 29 (S29), the CPU 44a determines the unused state of the gas. Each processing from step 27 to step 29 corresponds to each processing from step 15 to step 17 in the reference amplification setting processing described above. Therefore, when the gas shut-off valve 47 is in a closed state (negative determination at step 27), when the pressure of the gas flow path is outside the normal range (negative determination at step 28 (S28)), or the difference between the integrated flow rate values Is smaller than the determination value (negative determination in step 29), the process returns to step 10. That is, in the scene where the unused state of gas is determined, the determination of condensation is not performed in order to suppress erroneous determination of condensation.

  In step 30 (S30), the CPU 44a determines that condensation has occurred in the gas flow path. In step 31 (S31), the CPU 44a displays a warning on the display unit 45.

  FIG. 6 is a flowchart showing a reference amplification degree update procedure in the determination of the occurrence of condensation in the ultrasonic gas meter 40 according to the present embodiment. First, in step 40 (S40), the CPU 44a determines whether a predetermined period has elapsed. The predetermined period corresponds to a reference amplification degree update cycle, and is, for example, 15 days. If an affirmative determination is made in step 40, that is, if a predetermined period has elapsed, the process proceeds to step 41 (S41). On the other hand, if a negative determination is made in step 40, that is, if the predetermined period has not elapsed, the process of step 40 is performed again.

  In step 41, the CPU 44a measures the propagation time and calculates the gas flow rate. Specifically, the CPU 44a controls the transducers TD1 and TD2 through the transmission circuit 42, whereby the transducers TD1 and TD2 intermittently transmit ultrasonic signals. Next, the amplifier 43a amplifies the ultrasonic signals received by the transducers TD1 and TD2 to a predetermined level according to the amplification degree adjusted by the μCOM 44, and outputs this to the μCOM 44. Then, the CPU 44a measures the propagation time of the transducers TD1 and TD2. Thereafter, the CPU 44a calculates the gas flow rate from the propagation time, and calculates the gas flow rate from the gas flow rate and the flow path diameter.

  In each process from step 42 (S42) to step 48 (S48), it is determined whether or not the execution condition for the determination of the occurrence of condensation is satisfied, the determination of the occurrence of condensation, and whether or not the gas is unused. Make a decision. Here, each process from step 42 to step 48 corresponds to each process from step 22 to step 28 in the above-described process for determining the occurrence of condensation.

  In step 49 (S49), the CPU 44a updates the amplification used in step 40 as a reference amplification. The updated reference amplification degree is referred to in determining the occurrence of condensation.

  FIG. 7 is a flowchart showing processing for invalidating the dew condensation determination function provided in the ultrasonic gas meter 40 according to the present embodiment. First, in step 60 (S60), the CPU 44a determines whether or not the changeover switch 48 is set to the invalid side. If the changeover switch 48 is set to the invalid side, an affirmative determination is made in step 60, and therefore the process proceeds to step 64 (S64) described later. On the other hand, if the changeover switch 48 is set to the valid side, a negative determination is made in step 60, and thus the process proceeds to step 61 (S61).

  In step 61, the CPU 44a determines whether or not the sum of propagation times is outside a predetermined range. If the sum of the propagation times is out of the predetermined range, an affirmative determination is made in step 61, and the process proceeds to step 64. On the other hand, if the sum of the propagation times is within the predetermined range, a negative determination is made in step 61, and the process proceeds to step 62 (S62).

  In step 62, the CPU 44a determines whether or not the shipping mode is in progress. The shipping mode is an operation mode of the ultrasonic gas meter 40 that is set between the time when the gas meter is attached to the installation site and the mode is canceled. Since it is meaningful to execute the dew condensation determination only after the ultrasonic gas meter 40 is attached to the installation location such as the pipes 31 and 32, it is determined in this step 62 whether or not it is in the shipping mode. If it is currently in the shipping mode, an affirmative determination is made in step 62, and the process proceeds to step 64. On the other hand, if the shipping mode is currently canceled, a negative determination is made in step 62, and the process proceeds to step 63 (S63).

  In step 63, the CPU 44a determines whether or not the pressure of the gas flow path detected by the pressure sensor 49 is within a normal range. If the pressure in the gas flow path is abnormal, an affirmative determination is made in step 63, and the process proceeds to step 64. On the other hand, if the pressure in the gas flow path is normal, a negative determination is made in step 62, and the process returns to step 60.

  In step 64, the CPU 44a disables the condensation determination function. In this invalid state, each process associated with the determination of the occurrence of condensation is not executed.

  As described above, in the present embodiment, the ultrasonic gas meter 40 intermittently transmits ultrasonic signals into the gas flow path and receives the ultrasonic signals by the acoustic transducers TD1 and TD2 and the acoustic transducers TD1 and TD2. An amplifier 43a that amplifies the received signal to a predetermined strength, and when the amplification level is monitored at predetermined time intervals and the amplification level changes by a predetermined value or more than the initial value, condensation occurs in the gas flow path. And a CPU 44a for determining the unused state of the gas. Here, when the CPU 44a determines that the gas is not used, the CPU 44a does not determine whether or not condensation has occurred in the gas flow path.

  When the gas is not used, a mixed gas or negative pressure tends to be generated. When the mixed gas or negative pressure is generated, the amplification degree is changed. Therefore, the possibility of misjudgment can be reduced by not determining the occurrence of condensation when the gas is unused.

  Further, in the present embodiment, not only the specific determination of the occurrence of condensation, but also the reference amplification degree setting process and its update process, which are processes associated therewith, are determined when the unused state of the gas is determined. Is going to not do this. As a result, it is possible to determine the occurrence of dew condensation with an appropriate reference amplification factor, thereby reducing the possibility of erroneous determination.

  In the present embodiment, the CPU 44a determines that the gas is not used when the gas cutoff valve 47 is in a closed state in which the gas flow in the gas flow path is stopped. When the gas shut-off valve 47 is in the closed state, the gas flow between the gas supply source and the gas appliance 10 is shut off, so there is a high probability that the gas is not in use. Therefore, the unused state of the gas can be effectively determined from the closed state of the gas shutoff valve 47.

  In the present embodiment, the CPU 44a determines that the gas is not used when the pressure in the gas flow path is outside a predetermined range. In a state where the gas can be used, the pressure of the gas flow path is within a predetermined range corresponding to the normal range. In other cases, there is a high probability that the gas is not in use. Therefore, the unused state of the gas can be effectively determined from the closed state of the gas shutoff valve 47.

  Further, in this embodiment, the CPU 44a determines the unused state of the gas when the difference between the currently sampled integrated flow value and the integrated flow value sampled before a predetermined period is smaller than a predetermined determination value. Yes. If the gas is in use, the integrated flow rate value will increase over time. Therefore, the unused state of the gas can be determined effectively by taking into account the difference in the integrated flow rate value.

  In the present embodiment, the CPU 44a disables the condensation determination function when the operation mode is the shipping mode. The dew condensation determination function is effective in the situation where the ultrasonic gas meter 40 is disposed in the pipes 31 and 32 and measures the gas flow rate. In the shipping mode, the dew condensation determination function is disabled. It is possible to suppress erroneous determination of the occurrence of condensation and unnecessary power consumption.

  Further, when the CPU 44a determines that the pressure detected by the gas sensor 39 is reduced, the CPU 44a invalidates the dew condensation determination function. If the pressure of the gas flow path is not at a normal pressure, the condensation judgment may not be performed accurately.Therefore, by invalidating the condensation judgment, erroneous judgment of the occurrence of condensation and unnecessary power consumption can be avoided. Can be suppressed.

  The ultrasonic gas meter according to the present embodiment has been described above, but the present invention is not limited to this embodiment, and various modifications can be made within the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Gas supply system 10 Gas appliance 20 Regulator 31 Upstream piping 32 Downstream piping 40 Ultrasonic gas meter 41a Transducer I / F circuit 41b Transducer I / F circuit 42 Transmission circuit 43 Reception circuit 43a Amplifier 44 μCOM
44a CPU
44b ROM
44b RAM
44b Bus line 45 Indicator 46 Partition plate 47 Gas shut-off valve 48 Changeover switch 49 Pressure sensor TD1 transducer TD2 transducer

Claims (6)

Transmission means for intermittently transmitting ultrasonic signals in the gas flow path;
Receiving means for receiving the ultrasonic signal;
Amplifying means for amplifying the signal received by the receiving means to a predetermined strength;
Condensation determining means for monitoring the amplification degree by the amplification means every predetermined time, and determining that condensation has occurred in the gas flow path when the monitored amplification degree has changed by a predetermined value or more than the initial value;
A state determining means for determining an unused state of the gas,
The ultrasonic gas meter characterized in that the dew condensation determination means does not execute a determination as to whether or not dew condensation has occurred in the gas flow path when the state determination means determines that the gas is not used. .   2. The ultrasonic wave according to claim 1, wherein the state determination unit determines an unused state of the gas when the gas cutoff valve is in a closed state in which the gas flow in the gas flow path is stopped. Gas meter. A pressure detecting means for detecting a pressure in the gas flow path;
3. The ultrasonic type according to claim 1, wherein the state determination unit determines a gas unused state when the pressure detected by the pressure detection unit is outside a predetermined range. Gas meter. Based on the propagation time of the ultrasonic signal transmitted from the transmission unit and received by the reception unit, the flow rate measurement unit further measures the flow rate of the gas flowing in the gas flow path,
The state determining means periodically samples the integrated flow value obtained by integrating the flow measured by the flow measuring means, and the difference from the integrated flow value sampled before a predetermined period is smaller than a predetermined determination value. The ultrasonic gas meter according to claim 1, wherein an unused state of the gas is determined.   2. The ultrasonic gas meter according to claim 1, wherein the dew condensation determination unit invalidates a dew condensation determination function when the operation mode is a shipping mode. A pressure detecting means for detecting a pressure in the gas flow path;
2. The ultrasonic gas meter according to claim 1, wherein the dew condensation determination unit disables the dew condensation determination function when determining an abnormality in the pressure detected by the pressure detection unit.

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