JP5247604B2 - Ultrasonic gas meter and detection method for entering water - Google Patents

Description

  The present invention relates to an ultrasonic gas meter and a method for detecting water entering thereof.

  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 meter, water may enter and accumulate in the meter due to a crack in the pipe. 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 determining the intrusion of water while suppressing the cost, and its The object is to provide a water detection method.

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. When the propagation time of the ultrasonic signal transmitted from the transmitting means and received by the receiving means is not more than a specified value, and when the amplification degree by the amplifying means is not more than a predetermined value In at least one of the cases, a water entering judging means for judging that water has entered the meter flow path is provided. Further, based on the propagation time of the ultrasonic signal transmitted from the transmitting means and received by the receiving means, flow rate measuring means for measuring the flow rate of the gas flowing in the gas flow path, and for determining the propagation time Threshold voltage generating means for generating a threshold voltage of the threshold voltage generating means, wherein the threshold voltage generating means allows the water entry determining means to determine whether or not water has entered the meter flow path. It is characterized in that the timing at which the flow rate is generated is earlier than when the propagation time is obtained by the flow rate measuring means.

According to this ultrasonic gas meter, when at least one of the case where the propagation time of the ultrasonic signal is not more than the specified value and the case where the amplification degree is not more than the predetermined value, water enters the meter flow path. Judge that Here, the ultrasonic signal has a characteristic that it is transmitted faster in water than in gas and less easily attenuated. For this reason, when a certain amount of water accumulates in the meter, the propagation time tends to be short and the amplification degree tends to be small, so that the intrusion of water into the meter channel can be determined. In particular, since water is determined by processing by the water determining means, it is not necessary to provide a moisture sensor in the meter. Therefore, it is possible to detect that water has entered the flow path while reducing the cost. In addition, when the water entry determination means determines whether water has entered the meter flow path, the timing for generating the threshold voltage is set earlier than when the propagation time is obtained by the flow measurement means. Thus, by advancing the generation timing of the threshold voltage, it is possible to easily grasp the propagation time that is shortened at the time of entering the water, and it is possible to appropriately determine the entering of the water.

In the ultrasonic gas meter according to the present invention, the threshold voltage generating means may use the flow rate measuring means to determine whether or not water has entered the meter flow path. Therefore, it is preferable to set the voltage value lower than the voltage value when the propagation time is obtained.

  According to this ultrasonic gas meter, when the water entering judgment means judges whether or not water has entered the meter flow path, a threshold voltage for judging the propagation time is obtained by the flow measuring means. The voltage value is set lower than the current voltage value. Here, immediately before a certain amount of water accumulates in the meter, that is, when the amount of water is relatively small, the ultrasonic signal tends to be received weakly at a relatively early stage. Therefore, by making the threshold voltage lower than that at the time of flow rate measurement, this weakly received ultrasonic signal can be detected, and a relatively small amount of water can be detected.

  In the ultrasonic gas meter of the present invention, it is preferable that the determination interval by the water entering determination unit is longer than the measurement interval by the flow rate measurement unit.

  According to this ultrasonic gas meter, the determination interval by the water entry determination means is longer than the measurement interval by the flow rate measurement means. For this reason, the number of times of determination of entering water is smaller than the number of times of flow rate measurement, and an increase in power consumption for executing the determination of entering water can be suppressed.

  Further, in the ultrasonic gas meter of the present invention, when it is determined that water has entered the flow path a plurality of times in succession to the water entering determination means, an alarm, a signal output for alarming, and a cutoff are provided. It is preferable to further include security means for performing at least one of valve closing.

  According to this ultrasonic gas meter, when it is determined that water has infiltrated into the meter flow path several times in succession, at least one of alarm, signal output for alarm, and valve closing of the shut-off valve It is further provided with a security means for performing one. For this reason, not only can alarms be performed, but it is also possible to prevent alarms due to misjudgment due to external noise by performing alarms when it is determined that water has infiltrated multiple times in succession. can do.

The ultrasonic gas meter water detection method according to the present invention includes a transmission step of intermittently transmitting an ultrasonic signal in a gas flow path, a reception step of receiving the ultrasonic signal, and transmission in the transmission step. In the step of determining whether water has entered the meter flow path when the propagation time of the ultrasonic signal received in the receiving step is less than or equal to a predetermined value, and in the transmitting step A flow rate measuring step for measuring the flow rate of the gas flowing in the gas flow path based on the propagation time of the ultrasonic signal transmitted and received in the reception step, and a threshold voltage for generating a threshold voltage for determining the propagation time And in the threshold voltage generation step, when determining whether or not water has entered the meter flow path in the water entry determination step, the timing for generating the threshold voltage is the flow measurement step. In Characterized in that it faster than when determining the inter搬時.

According to this ultrasonic gas meter water detection method, when the propagation time of the ultrasonic signal is not more than a specified value and at least one of the cases where the amplification degree is not more than a predetermined value, It is judged that water has infiltrated. Here, the ultrasonic signal has a characteristic that it is transmitted faster in water than in gas and less easily attenuated. For this reason, when a certain amount of water accumulates in the meter, the propagation time tends to be short and the amplification degree tends to be small, so that the intrusion of water into the meter channel can be determined. In particular, since water entry is determined by processing in the water entry determination step, it is not necessary to provide a moisture sensor in the meter. Therefore, it is possible to detect that water has entered the flow path while reducing the cost. Furthermore, when making the water entering judgment means determine whether or not water has entered the meter flow path, the timing for generating the threshold voltage is set earlier than when the propagation time is obtained by the flow measurement means. Thus, by advancing the generation timing of the threshold voltage, it is possible to easily grasp the propagation time that is shortened at the time of entering the water, and it is possible to appropriately determine the entering of the water.

  According to the present invention, it is possible to determine the intrusion of water while suppressing the cost.

It is a lineblock diagram showing the ultrasonic gas meter concerning the embodiment of the present invention. FIG. 2 is a configuration diagram showing the inside of μCOM shown in FIG. 1. It is a figure which shows the mode of reception of an ultrasonic signal, (a) shows the reception characteristic of an ultrasonic signal when 0-35 cc of water permeates, (b) shows the ultrasonic wave when 40 cc of water permeates. (C) shows the reception characteristic of the ultrasonic signal when 42 cc or more of water has entered. It is a graph which shows the propagation time and amplification degree according to the amount of infiltrated water. It is a flowchart which shows the water entering detection method by the ultrasonic 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 illustrating an ultrasonic gas meter according to an embodiment of the present invention. The ultrasonic gas meter 1 shown in FIG. 1 includes two acoustic transducers (disposed by a distance L in the gas flow path and 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 10 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 transmitter circuit 12 and a receiver circuit 13 via transducer interface (I / F) circuits 11a, 11b, respectively. The transmission circuit 12 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) 14.

  The receiving circuit 13 incorporates an amplifier (amplifying means) 13a that inputs 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 intensity. Yes. The amplification degree of the amplifier 13a can be adjusted by the μCOM 14. Further, a display 15 is connected to the μCOM 14.

  In addition, a plurality of partition plates 16 are provided in the flow path in which the transducers TD1 and TD2 are provided. The plurality of partition plates 16 prevent the generation of vortices at the time of gas inflow and contribute to accurate flow rate measurement. In FIG. 1, the partition plate 16 and the transmission / reception direction of the ultrasonic signal are illustrated so as to intersect with each other. However, the two are actually in a parallel relationship, and the partition plate 16 does not interfere with the transmission / reception of the ultrasonic signal. Is installed.

  FIG. 2 is a block diagram showing the inside of the μCOM 14 shown in FIG. As shown in FIG. 2, the μCOM 14 includes a central processing unit (CPU) 14a that performs various processes according to a program, a ROM 14b that is a read-only memory that stores a program for processing performed by the CPU 14a, and various types of CPU 14a. A RAM 14c, which is a readable / writable memory having a work area used in the processing process, a data storage area for storing various data, and the like are incorporated. These are connected to each other by a bus line 14d.

  Further, the CPU 14a measures the gas flow rate based on the propagation time 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 flow rate measurement function determines the propagation time based on a threshold voltage from a threshold voltage generation circuit (threshold voltage generation means) (not shown). That is, an ultrasonic signal transmitted intermittently from one transducer TD1, TD2 is received by the other transducer TD1, TD2 while being reflected, refracted, attenuated, and the like. For this reason, some ultrasonic signals are received relatively early after transmission and others are received relatively late. In order to determine the propagation time of such an ultrasonic signal, the flow measurement function calculates the propagation time when the intensity of the received ultrasonic signal is equal to or higher than the threshold voltage generated by the threshold voltage generation circuit. Will be asked. That is, the flow rate measurement function uses the time from when the ultrasonic signal is transmitted to when the intensity of the received ultrasonic signal is equal to or higher than the threshold voltage generated by the threshold voltage generation circuit as the propagation time.

  Furthermore, the CPU 14a according to the present embodiment has at least one of the case where the propagation time of the ultrasonic signal transmitted and received by the transducers TD1 and TD2 is equal to or less than a specified value and the case where the amplification degree by the amplifier 13a is equal to or less than a predetermined value. In this case, it has a water entry judgment function (water entry judgment means) for judging that water has entered the meter flow path. Here, the ultrasonic signal has a characteristic that it is transmitted in water faster and less easily to be attenuated than in gas. For this reason, when a certain amount of water accumulates in the meter, the propagation time tends to be short and the amplification degree tends to be small, so that the intrusion of water into the meter channel can be determined.

  3A and 3B are diagrams showing how an ultrasonic signal is received. FIG. 3A shows the reception characteristics of an ultrasonic signal when 0 to 35 cc of water enters, and FIG. 3B shows that 40 cc of water has entered. (C) shows the reception characteristic of the ultrasonic signal when 42 cc or more of water has entered.

  First, a case where 0 to 35 cc of water has entered will be described with reference to FIG. If transmission of an ultrasonic signal is started at time 0, the ultrasonic signal is not received immediately, but starts to be received at time t1. At time t2, the reception level of the ultrasonic signal becomes equal to or higher than the threshold voltage. For this reason, it is determined that the propagation time is time t2. In this embodiment, the propagation time t2 is about 195 microseconds.

  Next, a case where 40 cc of water has entered will be described with reference to FIG. Ultrasonic signals travel through water faster and less easily than gas. For this reason, if transmission of an ultrasonic signal is started at time 0, an ultrasonic signal having a relatively weak reception level is observed near time t3 (50 microseconds) before time t1. Thereafter, the process is the same as described with reference to FIG. In addition, the case where 40 cc of water permeates is the case where water permeates to about 2.8th layer of the multilayer flow path constituted by the partition plate 16.

  Next, a case where 42 cc of water has entered will be described with reference to FIG. When water enters the 2.8th layer or more, the amount of water increases, so that many ultrasonic signals easily propagate in the water. Therefore, the reception level of the ultrasonic signal becomes equal to or higher than the threshold voltage near time t3 (50 microseconds). For this reason, the propagation time is determined to be time t3.

  FIG. 4 is a graph showing the propagation time and the amplification degree according to the amount of the infiltrated water, and Table 1 is a table showing detailed values of the propagation time and the amplification degree according to the amount of the infiltrated water. As shown in FIG. 4 and Table 1, the propagation time is abruptly shortened at the boundary between 40 cc and 42 cc. Further, when water of 42 cc or more enters, many ultrasonic signals propagate in the water, so that the ultrasonic signals are difficult to attenuate and the amplification degree is also reduced. The water entry judgment function judges the water entry by capturing the features shown in FIG. 4 and Table 1.

  In addition, the CPU 14a according to the present embodiment has a security function. The security function is a function that performs at least one of alarm, signal output for alarm, and closing of the shutoff valve 10 when it is determined that water has entered the flow path.

  Furthermore, the threshold voltage generation circuit according to the present embodiment is configured so that the threshold voltage is variable. Specifically, the ultrasonic gas meter 1 according to the present embodiment has a measurement mode for measuring a flow rate and a water entering determination mode for determining whether water enters, and performs flow rate measurement once every 2 seconds (measurement mode). The water entry determination is performed once every 10 minutes, for example (water entry determination mode). Then, the threshold voltage is set to a normal value at the time of flow rate measurement, and the threshold voltage is set to a voltage value lower than the voltage value at the time of flow rate measurement when water entry determination is performed.

  That is, as shown in FIG. 3B, when performing flow rate measurement with the flow rate measurement function, the threshold voltage for determining the propagation time is set to a normal value (see threshold voltage 1), and the determination of entering water is performed The threshold voltage is set to a voltage value lower than the voltage value when the propagation time is obtained by the flow measurement function (see threshold voltage 2). Thereby, it can also be judged about 40 cc of water before reaching 42 cc.

  FIG. 5 is a flowchart showing a water entry detection method by the ultrasonic gas meter 1 according to this embodiment. First, the CPU 14a determines whether or not a predetermined time has elapsed (S1). Here, the predetermined time is, for example, 2 seconds. If it is determined that the predetermined time has elapsed (S1: YES), the transducers TD1 and TD2 intermittently transmit ultrasonic signals (S2).

  Thereafter, the CPU 14a determines whether or not a second predetermined time has elapsed (S3). Here, the second predetermined time is, for example, about 190 microseconds. Then, the threshold voltage generation circuit is temporarily turned on (S4). As described above, in the ultrasonic gas meter 1 according to the present embodiment, it is known in advance how much the propagation time will be, so that the threshold voltage generation circuit is turned on immediately before the predicted propagation time. As a result, power consumption is reduced.

  Next, the amplifier 13a amplifies the received ultrasonic signal to a predetermined level (S5), and the flow rate measurement function measures the propagation time (S6). Thereafter, the flow rate measurement function calculates the gas flow rate from the propagation time (S7), and calculates the gas flow rate from the gas flow rate and the flow path diameter (S8). Then, the process proceeds to step S1. In addition, the process from step S1 to S8 corresponds to the above-described measurement mode.

  When it is determined that the predetermined time has not elapsed (S1: NO), the CPU 14a determines whether a third predetermined time has elapsed (S9). Here, the third predetermined time is, for example, 10 minutes. When it is determined that the third predetermined time has elapsed (S9: YES), the water entering determination mode is started, and the process proceeds to step S10. On the other hand, when it is determined that the third predetermined time has not elapsed (S9: NO), the process proceeds to step S1. As described above, in this embodiment, the interval of water entry detection by the water entry determination function is set longer than the measurement interval by the flow rate measurement function.

  In step S10, the transducers TD1 and TD2 intermittently transmit ultrasonic signals (S10). Thereafter, the CPU 14a determines whether or not a fourth predetermined time has elapsed (S11). Here, the fourth predetermined time is, for example, about 30 microseconds. Next, the threshold voltage generation circuit sets the threshold voltage to a voltage value lower than that in the measurement mode (S12). This makes it easy to detect water entry immediately before a certain amount of water accumulates in the meter, that is, at a time when the amount of water is relatively small.

  Then, the threshold voltage generation circuit is temporarily turned on (S13). Here, in step S4, the timing at which the threshold voltage circuit is turned on is about 190 microseconds after the start of transmission of the ultrasonic signal, but in step S13, it is 30 microseconds later. Thus, when the threshold voltage generation circuit determines whether water has entered the meter flow path, the threshold voltage generation circuit makes the threshold voltage generation timing earlier than in the measurement mode. Thereby, the propagation time which becomes short at the time of entering water can be easily grasped, and the entering of water can be appropriately determined.

  Next, the amplifier 13a amplifies the received ultrasonic signal to a predetermined level (S14), and the water entering determination function measures the propagation time (S15). Thereafter, the water entering determination function determines whether or not the propagation time is equal to or shorter than the specified time (S16). Here, the specified time is, for example, 60 microseconds, but the degree to which the propagation time is shortened when entering water varies depending on the channel shape, the presence / absence of a multilayer channel, the presence / absence of a flow rate, and the like. For this reason, it is desirable that the specified time is set to about half or about one quarter of the propagation time when water does not enter.

  If it is determined that the propagation time is equal to or shorter than the specified time (S16: YES), the process proceeds to step S18. On the other hand, when it is determined that the propagation time is not less than the specified time (S16: NO), the water entering determination function determines whether or not the amplification degree is equal to or less than a predetermined value (S17). Here, in the present embodiment, the predetermined value is about “35”, but the degree of decrease in the degree of amplification varies depending on various factors. For this reason, it is desirable that the predetermined value is set to about 90% of the amplification degree when water does not enter.

  When it is determined that the amplification degree is not less than or equal to the predetermined value (S17: NO), the process proceeds to step S1. On the other hand, when it is determined that the amplification degree is equal to or less than the predetermined value (S17: YES), the process proceeds to step S18. In step S18, the water entry determination function determines that water has entered the flow path because the propagation time satisfies a condition of either the specified time or less or the amplification degree satisfies a predetermined value or less ( S18).

  Next, the security function determines whether or not water intrusion is detected continuously (n is an integer of 2 or more) times (S19). When it is determined that water intrusion has not been detected n times consecutively (S19: NO), the process proceeds to step S1. On the other hand, when it is determined that water intrusion has been detected n times consecutively (S19: YES), the security function performs at least one of alarm, signal output for alarm, and shut-off valve 10 closing ( S20), and then the processing shown in FIG. 5 ends.

  As described above, according to the ultrasonic gas meter 1 and the water detection method thereof according to the present embodiment, when the propagation time of the ultrasonic signal is not more than the specified value, and when the amplification degree is not more than the predetermined value. In at least one of the cases, it is determined that water has entered the meter flow path. Here, the ultrasonic signal has a characteristic that it is transmitted faster in water than in gas and less easily attenuated. For this reason, when a certain amount of water accumulates in the meter, the propagation time tends to be short and the amplification degree tends to be small, so that the intrusion of water into the meter channel can be determined. In particular, since water entry is determined by processing by the water entry determination function, it is not necessary to provide a moisture sensor in the meter. Therefore, it is possible to detect that water has entered the flow path while reducing the cost.

  In addition, when making the water determination function determine whether water has entered the meter flow path, the threshold voltage for determining the propagation time is lower than the voltage value when the propagation time is determined by the flow measurement function Set to voltage value. Here, immediately before a certain amount of water accumulates in the meter, that is, when the amount of water is relatively small, the ultrasonic signal tends to be received weakly at a relatively early stage. Therefore, by making the threshold voltage lower than that at the time of flow rate measurement, this weakly received ultrasonic signal can be detected, and a relatively small amount of water can be detected.

  Further, the determination interval by the water entry determination function is longer than the measurement interval by the flow rate measurement function. For this reason, the number of times of determination of entering water is smaller than the number of times of flow rate measurement, and an increase in power consumption for executing the determination of entering water can be suppressed.

  Further, when the water entering determination function determines whether water has entered the meter flow path, the timing for generating the threshold voltage is set earlier than when the propagation time is obtained by the flow rate measuring means. Thus, by advancing the generation timing of the threshold voltage, it is possible to easily grasp the propagation time that is shortened at the time of entering the water, and it is possible to appropriately determine the entering of the water.

  In addition, when it is determined that water has infiltrated into the meter flow path several times in succession, a safety function is further provided that performs at least one of an alarm, a signal output for alarm, and a shut-off valve closing. Prepare. For this reason, not only can alarms be performed, but it is also possible to prevent alarms due to misjudgment due to external noise by performing alarms when it is determined that water has infiltrated multiple times in succession. can do. The external noise is, for example, noise from a TV radio tower or noise from a mobile phone. Also, external noise is received when noise is applied to the connection cable between the ultrasonic gas meter 1 and the transmission device.

  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, in the ultrasonic gas meter 1 according to the present embodiment, as shown in FIG. 5, when the propagation time satisfies a condition that is less than a specified time or the amplification degree is less than a predetermined value, It was judged that water had entered the road. However, it may be determined that water has infiltrated into the flow path when both of the conditions are satisfied. This is because it is possible to more reliably determine the entry of water.

  Furthermore, various numerical values shown in the ultrasonic gas meter 1 according to the present embodiment can be changed to various values depending on the installation environment and specifications of the meter.

DESCRIPTION OF SYMBOLS 1 ... Ultrasonic gas meter 10 ... Gas cutoff valve 11a, 11b ... Transducer I / F circuit 12 ... Transmission circuit 13 ... Reception circuit 13a ... Amplifier (amplification means)
14 ... μCOM
14a ... CPU (water determining means, flow rate measuring means, security means)
14b ... ROM
14b ... RAM
14b ... bus line 15 ... display 16 ... partition plates TD1, TD2 ... transducer (transmission means, reception means)

Claims (5)

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;
When the propagation time of the ultrasonic signal transmitted from the transmission unit and received by the reception unit is a specified value or less, and at least one of the cases where the amplification degree by the amplification unit is a predetermined value or less, A water entry judging means for judging that water has entered the meter flow path;
Flow rate measuring means for measuring 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 means and received by the receiving means;
Threshold voltage generating means for generating a threshold voltage for determining the propagation time,
When the threshold voltage generation means causes the water entry determination means to determine whether or not water has entered the meter flow path, the threshold voltage generation means is more timely than the time when the flow rate measurement means obtains the propagation time. ultrasonic gas meter, characterized in that also fast. The ultrasonic gas meter according to claim 1 , wherein the determination interval by the water entering determination means is longer than the measurement interval by the flow rate measurement means . The threshold voltage generating means, when making the water entering determining means determine whether or not water has entered the meter flow path, is more than a voltage value when the threshold voltage is determined by the flow rate measuring means to determine the propagation time. The ultrasonic gas meter according to claim 2, wherein the ultrasonic gas meter is set to a low voltage value . Security that performs at least one of alarm, signal output for alarm, and shut-off of shut-off valve when it is determined that water has infiltrated into the flow path a plurality of times in succession to the water entering determination means The ultrasonic gas meter according to any one of claims 1 to 3 , further comprising means . A transmission step of intermittently transmitting an ultrasonic signal in the gas flow path;
Receiving the ultrasonic signal; and
When the propagation time of the ultrasonic signal transmitted in the transmission step and received in the reception step is equal to or less than a specified value, a water entry determination step for determining that water has entered the meter flow path,
Based on the propagation time of the ultrasonic signal transmitted in the transmission step and received in the reception step, a flow rate measurement step of measuring the flow rate of the gas flowing in the gas flow path,
A threshold voltage generation step of generating a threshold voltage for determining the propagation time,
In the threshold voltage generation step, when determining whether or not water has entered the meter flow path in the water determination step, when determining the propagation time in the flow measurement step, the timing for generating the threshold voltage A method for detecting water entering an ultrasonic gas meter, characterized in that the method is faster .

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