JP5872654B2 - Ultrasonic gas meter - Google Patents

Description

  The present invention relates to an ultrasonic gas meter.

  Conventionally, an ultrasonic gas meter using an ultrasonic flow velocity sensor has been proposed (for example, Patent Document 1). In the ultrasonic gas meter described above, an ultrasonic flow sensor is constituted by two acoustic transducers composed of, for example, piezoelectric transducers that operate at an ultrasonic frequency that are arranged at a predetermined distance in the 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.

JP 2008-51562 A

  By the way, in a gas supply system including an ultrasonic gas meter, water accumulates in the piping due to cracks in the piping, etc., and a gas containing a large amount of water vapor is supplied into the meter. Condensation with water adhering to the protective member may occur and the instrumental error may change. If the instrumental difference changes, the gas flow rate cannot be detected accurately, causing a problem with charges.

  Therefore, it is conceivable to provide a moisture sensor in order to detect the intrusion of water in the meter. In this case, not only the sensor cost is required, but also a sensor wiring seal structure is required, resulting in an increase in cost.

  The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide an ultrasonic gas meter capable of judging condensation while suppressing cost. .

  An ultrasonic gas meter according to the present invention includes a transmitting unit that intermittently transmits an ultrasonic signal in a gas flow path, a receiving unit that receives the ultrasonic signal, and a signal received by the receiving unit with a predetermined strength. Amplifying means that amplifies the signal and the amplification degree by the amplification 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 occurs in the meter flow path. And a means for determining condensation, and an updating means for updating the initial value to the amplification degree by the amplification means when the amplification degree by the amplification means is within a specified range with respect to the initial value, the transmission means and the reception means Transmits and receives ultrasonic signals from both the upstream side and the downstream side with respect to the gas flow direction, and the determination means transmits the ultrasonic signal transmitted from the upstream side and received, and Sent from downstream The sum of the propagation time of the received ultrasonic signal, when outside the predetermined range, characterized in that it does not perform a determination of whether condensation to meter flow path has occurred.

  According to this ultrasonic gas meter, the amplification level is monitored every predetermined time, and when the monitored amplification level changes by a predetermined value or more than the initial value, it is determined that condensation has occurred in the meter flow path. 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, it can be determined that condensation has occurred in the meter flow path in the above case. In particular, since the determination of dew condensation is determined by processing by the dew condensation determination means, it is not necessary to provide a moisture sensor or the like, and the generation of sensor cost and cost required for the seal structure can be suppressed. Therefore, it is possible to determine the condensation while suppressing the cost.

  When 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 the predetermined range, the meter flow path Do not make a determination as to whether or not condensation has occurred. 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. Therefore, when the sum of the propagation times is out of the predetermined range, it can be said that the gas type to be measured has changed or a mixed gas state has occurred. As described above, when the gas type is changed or in the mixed gas state, the amplification degree tends to change, and an error is easily caused in the determination of the occurrence of condensation. Therefore, the possibility of erroneous determination can be reduced by not performing the determination of the occurrence of condensation when the sum of the propagation times is outside the predetermined range.

  In addition, when the amplification degree is within a specified range with respect to the initial value, the initial value is updated to the amplification degree by the amplification means, so that condensation and condensation are caused based on the amplification degree that has changed due to temperature change or dust adhesion. Judgment can be suppressed, and the possibility of misjudgment can be reduced.

  In the ultrasonic gas meter according to the present invention, it is preferable that the ultrasonic gas meter further includes a switching unit capable of switching between execution and non-execution for determining whether or not dew condensation has occurred in the meter flow path.

  According to this ultrasonic gas meter, since it is possible to switch between execution and non-execution for determining whether or not condensation has occurred in the meter flow path, the gas meter is removed during maintenance to enter a mixed gas state. In such a case, the determination of the occurrence of condensation can be made non-executed so as not to erroneously determine that it is condensation, and the possibility of erroneous determination can be reduced.

  According to the present invention, it is possible to determine condensation while suppressing costs.

1 is a configuration diagram of a gas supply system including an ultrasonic gas meter according to an embodiment of the present invention. It is a lineblock diagram showing the ultrasonic gas meter concerning the embodiment of the present invention. FIG. 3 is a configuration diagram showing the inside of μCOM shown in FIG. 2. It is a graph which shows the outline | summary of operation | movement of the ultrasonic type gas meter which concerns on this embodiment. It is a flowchart which shows operation | movement of the ultrasonic type gas meter which concerns on this embodiment.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a gas supply system including an ultrasonic gas meter according to an embodiment of the present invention. 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 flow path connected to the upstream pipe 31 and the downstream pipe 32 is formed in the gas meter 40, and the fuel gas passes through the gas meter 40 and the downstream pipe 32 from the upstream pipe 31. It reaches the instrument 10 and is burned in the gas instrument 10.

  Here, in the conventional 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 showing an ultrasonic gas meter 40 according to the embodiment of the present invention. 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 (switching means) 48. The changeover switch 48 can switch the validity / invalidity of a dew condensation determination function described later.

  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. It has a flow rate measurement function that measures the flow rate. Here, the sampling time is, for example, 2 seconds.

  Further, the CPU 44a according to the present embodiment 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, It has a dew condensation determination function (determination means) that determines that dew condensation has occurred in the meter flow path. 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, it can be determined that condensation has occurred in the meter flow path when the amplification degree changes by a predetermined value or more from the initial value. The initial value is determined according to, for example, the gas type, and is about “40” in the case of 43A gas and about “20” in the case of LP gas.

  In addition, the dew condensation determination function does not determine whether or not dew condensation has occurred in the meter flow path in the following two cases. 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 outside 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, when the sum of the propagation times is outside the predetermined range, the dew condensation determination function does not execute the dew condensation occurrence determination.

  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 become unstable. For this reason, an error is likely to occur in the determination of the occurrence of condensation. Therefore, the condensation determination function does not execute the determination of the occurrence of condensation when the flow rate exceeds the predetermined flow rate.

  Further, the CPU 44a according to the present embodiment includes an update function (update means). The update function is a function for updating the initial value. 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 update function updates the initial value.

  More specifically, when the ambient temperature changes, the amplification degree tends to increase or decrease by about “2”. Further, when dust adheres, the amplification degree tends to change gradually over a long period of time of about “1” to “2”. Therefore, the update function measures the amplification degree by the amplifier 43a every predetermined period (for example, 15 days), and when the measured amplification degree is within a prescribed range (for example, ± 2) with respect to the initial value, the initial value is amplified. The amplification degree is updated to 43a. Thereby, it is possible to reduce a possibility that a minute change in the amplification degree is accumulated and erroneously determined to be dew condensation.

  Further, the CPU 44a enables or disables the dew condensation determination function according to the switch signal from the changeover switch 48. That is, when the changeover switch 48 is set to the effective side, the dew condensation determination function executes the determination of the occurrence of condensation, and when the changeover switch 48 is set to the invalid side, the dew condensation determination function does not determine the occurrence of condensation. Execute.

  Next, the outline | summary of operation | movement of the ultrasonic type gas meter 40 which concerns on this embodiment is demonstrated. FIG. 4 is a graph showing an outline of the operation of the ultrasonic gas meter 40 according to the present embodiment. As shown in FIG. 4, it is first assumed that the initial value of the amplification degree is “40”. Assume that the amplification degree after the elapse of 15 days is “41”. In this case, the update function of the CPU 44a updates the initial value because the amplification degree of the amplifier 43a is within the range of ± 2 of the initial value “40”. That is, the update function updates the initial value to “41”.

  It is assumed that the amplification degree of the amplifier 43a is “44” when 30 days have elapsed. In this case, the update function does not update the initial value because the amplification degree has changed (increased) by “3” or more from the initial value “41”.

  Next, it is assumed that the amplification degree by the amplifier 43a is “47” when 45 days have elapsed. In this case, the update function does not update the initial value because the amplification degree of the amplifier 43a is not within the range of ± 2 of the initial value.

  Thereafter, it is assumed that the amplification degree by the amplifier 43a is “56” when 60 days have elapsed. In this case, the update function does not update the initial value. Further, the dew condensation determination function determines that dew condensation has occurred in the meter flow path because the amplification degree has changed by a predetermined value (eg, “10”) or more with respect to the initial value (initial value “41”). . Further, the CPU 44a causes the display unit 45 to display a warning because the amplification degree has changed by a predetermined value or more with respect to the initial value. The warning is not limited to display, but may be voice output, notification to the management center, notification to an alarm device, or the like.

  FIG. 5 is a flowchart showing the operation of the ultrasonic gas meter 40 according to this embodiment. First, the CPU 44a determines whether or not a specified time has elapsed (S1). Here, the specified time is, for example, 2 seconds. If it is determined that the specified time has not elapsed (S1: NO), this process is repeated until it is determined that the specified time has elapsed. If it is determined that the specified time has elapsed (S1: YES), the transducers TD1, TD2 intermittently transmit ultrasonic signals (S2).

  Next, the amplifier 43a amplifies the received ultrasonic signal to a predetermined level (S3), and the flow rate measurement function measures the propagation time (S4). Thereafter, the flow rate measurement function calculates the gas flow rate from the propagation time (S5), and calculates the gas flow rate from the gas flow rate and the flow path diameter (S6).

  Thereafter, the CPU 44a determines whether or not a predetermined time has elapsed (S7). If it is determined that the predetermined time has not elapsed (S7: NO), the process proceeds to step S1. On the other hand, if it is determined that the predetermined time has elapsed (S7: YES), the CPU 44a determines whether or not the changeover switch 48 is set to the effective side (S8).

  If it is determined that the changeover switch 48 is not set to the valid side (S8: NO), the process proceeds to step S1. When it is determined that the changeover switch 48 is set to the effective side (S8: YES), the dew condensation determination function determines whether the sum of propagation times is within a predetermined range (S9).

  When the sum of the propagation times is not within the predetermined range (S9: NO), that is, when it is outside the predetermined range, the dew condensation determination function moves to step S1 without executing the dew condensation determination in step S14 described later. When it is determined that the sum of the propagation times is within the predetermined range (S9: YES), that is, when it is not outside the predetermined range, the dew condensation determination function determines whether or not the flow rate calculated in step S6 is less than or equal to the predetermined flow rate. (S10).

  When it is determined that the flow rate is not equal to or less than the predetermined flow rate (S10: NO), that is, when it is determined that the flow rate exceeds the predetermined flow rate, the dew condensation determination function does not execute the dew condensation determination in step S14 described later, and the process proceeds to step S1. To do. When it is determined that the flow rate is equal to or lower than the predetermined flow rate (S10: YES), that is, when it is determined that the predetermined flow rate is not exceeded, the dew condensation determination function determines whether or not the amplification degree in step S3 has changed by a predetermined value or more from the initial value. Judgment is made (S11).

  When it is determined that the amplification degree has not changed by a predetermined value or more from the initial value (S11: NO), the update function determines whether or not the amplification degree in step S3 is within a specified range (S12). If it is determined that the amplification degree is not within the specified range (S12: NO), the process proceeds to step S1. On the other hand, when it is determined that the amplification factor is within the specified range (S12: YES), the update function updates the initial value to the amplification factor in step S3 (S13). Then, the process proceeds to step S1.

  By the way, when it is determined that the degree of amplification has changed by a predetermined value or more from the initial value (S11: YES), the dew condensation determination function determines that dew condensation has occurred in the meter flow dew (S14). Thereafter, the CPU 44a displays a warning on the display 45 (S15), and the process shown in FIG.

  Thus, according to the ultrasonic gas meter 40 according to the present embodiment, the amplification degree is monitored every predetermined time, and when the monitored amplification degree changes by a predetermined value or more than the initial value, Judge 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, it can be determined that condensation has occurred in the meter flow path in the above case. In particular, since the determination of dew condensation is determined by processing by the dew condensation determination function, there is no need to provide a moisture sensor or the like, and the generation of sensor cost and cost required for the seal structure can be suppressed. Therefore, it is possible to determine the condensation while suppressing the cost.

  When 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 the predetermined range, the meter flow path Do not make a determination as to whether or not condensation has occurred. 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. Therefore, when the sum of the propagation times is out of the predetermined range, it can be said that the gas type to be measured has changed or a mixed gas state has occurred. As described above, when the gas type is changed or in the mixed gas state, the amplification degree tends to change, and an error is easily caused in the determination of the occurrence of condensation. Therefore, the possibility of erroneous determination can be reduced by not performing the determination of the occurrence of condensation when the sum of the propagation times is outside the predetermined range.

  Further, when the amplification degree is within the specified range with respect to the initial value, the initial value is updated to the amplification degree by the amplifier 43a, so it is determined that condensation has occurred based on the amplification degree that has changed due to temperature change or dust adhesion. Can be suppressed, and the possibility of misjudgment can be reduced.

  In addition, since it is possible to switch between execution and non-execution for determining whether or not condensation has occurred in the meter flow path, condensation may occur when the gas meter 40 is removed during maintenance to enter a mixed gas state. Therefore, the determination of the occurrence of condensation can be made non-executed so as not to make a false determination that it is, thus reducing the possibility of erroneous determination.

  As described above, the present invention has been described based on the embodiment, but the present invention is not limited to the above embodiment, and may be modified without departing from the gist of the present invention. For example, each numerical value shown above can be changed to various values depending on the usage environment, specifications, etc. of the ultrasonic gas meter 40.

DESCRIPTION OF SYMBOLS 1 ... Gas supply system 10 ... Gas appliance 20 ... Regulator 31 ... Upstream piping 32 ... Downstream piping 40 ... Ultrasonic gas meter 41a, 41b ... Transducer I / F circuit 42 ... Transmission circuit 43 ... Reception circuit 43a ... Amplifier ( Amplification means)
44 ... μCOM
44a ... CPU (determination means, update means)
44b ... ROM
44b ... RAM
44b ... bus line 45 ... indicator 46 ... partition plate 47 ... gas shutoff valve 48 ... changeover switch (switching means)
TD1, TD2 ... Transducer (transmission means, reception means)

Claims (3)

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;
The degree of amplification by the amplification means is monitored every predetermined time, and when the monitored degree of amplification changes by a predetermined value or more than the initial value, condensation determination means for determining that condensation has occurred in the meter flow path;
When the amplification degree by the amplification means is within a specified range with respect to the initial value, the update means for updating the initial value to the amplification degree by the amplification means,
The transmission means and the reception means transmit and receive ultrasonic signals from both the upstream side and the downstream side with respect to the gas flow direction, and
When 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 the predetermined range, the determination means An ultrasonic gas meter characterized by not performing a determination as to whether or not condensation occurs in the meter flow path. The gas meter according to claim 1, further comprising a switching unit that can switch between execution and non-execution for determining whether or not condensation has occurred in the meter flow path by the determination unit. 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 determination means does not execute a determination as to whether or not condensation has occurred in the meter flow path when the flow rate measured by the flow rate measurement means exceeds a predetermined flow rate.
The ultrasonic gas meter according to claim 1, wherein the ultrasonic gas meter is provided.

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