JP5516182B2 - Gas shut-off device - Google Patents

Description

  The present invention relates to a gas cutoff device, and more particularly to a gas cutoff device that detects a measurement abnormality caused by a medium having different acoustic impedance entering a measurement unit of the gas cutoff device.

  Conventionally, as this type of gas shut-off device, there is one as shown in FIG. 3 (for example, see Patent Document 1).

  The configuration of the gas shut-off device disclosed in Patent Document 1 will be briefly described with reference to FIG.

  The gas cutoff device includes two acoustic transducers TD1 and TD2, which are piezoelectric vibrators. Furthermore, the gas cutoff valve 1 is provided on the upstream side of the acoustic transducers TD1 and TD2, and shuts off the gas flow path. Each acoustic transducer TD1, TD2 is connected to a transmission circuit 4 and a reception circuit 5 via acoustic transducer interface (I / F) circuits 2, 3. The transmission circuit 4 drives one of the acoustic transducers TD1 and TD2 to generate an ultrasonic signal under the control of the microcomputer (μCOM) 6. The receiving circuit 5 includes an amplifier 7 that receives the ultrasonic signal that has passed through the flow path from the other acoustic transducers TD1 and TD2 and amplifies the ultrasonic signal to a predetermined intensity. The amplification degree of the amplifier 7 can be adjusted by the μCOM 6. Further, the display 8 is connected to the μCOM 6.

The μ COM 6 has a measurement function of measuring the gas flow rate at each sampling time using the two acoustic transducers TD1 and TD2, and multiplying the measured gas flow rate by the cross-sectional area of the gas flow path to measure the instantaneous flow rate. The μ COM 6 has a mode determination function for determining the current mode from the specified number of instantaneous flow values measured by the measurement function, and transits between the three modes of the small pulsation mode, the large pulsation mode, and the limit mode. The small pulsation mode is a mode when the gas pulsation is the smallest, and the gas pulsation is large in the large pulsation mode and the limit mode. When the pulsation of the gas is large, the flow rate variations occur, to change the mode, or longer measurement interval, also Increase the number of measurements to determine a more accurate instantaneous flow rate.

Next, the operation of the configuration of the prior art will be described with reference to FIG. The μ COM 6 determines whether water has entered the gas flow path based on the amplification degree of the received ultrasonic signal. When the amount of flooding is 0 cc, the maximum value and the minimum value of the amplification degree are 20 as the initial value. And in the range of 20 cc-70 cc, the degree of amplification will be 35 or more. The amplification degree is equal to or greater than a value obtained by adding a predetermined value (for example, 10) to the initial amplification degree.

Further, when the water immersion amount is 80 cc and the gas flow path is full, the amplification factor is 8 to 10, and the amplification factor is equal to or less than a value obtained by subtracting a specified value (for example, 10) from the initial amplification factor. μ COM6 has a predetermined value or more when the amplification degree is not less than a value obtained by adding a predetermined value to the initial amplification degree, and water less than a predetermined amount has entered. Judge that water has entered.

Next, when the water immersion amount is 0 cc to 40 cc, the propagation time is about 248 μs in both forward and reverse directions, and when the water immersion amount is 50 cc to 80 cc, the propagation time decreases to less than 134 μs. The μ COM 6 determines that a predetermined amount or more of water has entered when the initial amplification degree is equal to or less than a value obtained by subtracting the specified value and the propagation time is equal to or less than a predetermined time.

Further, when the amount of water immersion is 0 cc, the difference between the maximum value and the minimum value of the instantaneous flow rate is small. When the amount of water is 20 cc or more, the difference between the maximum value and the minimum value of the instantaneous flow rate is a predetermined flow rate or more. In μCOM6, the amplification degree is equal to or greater than the value obtained by adding a predetermined value to the initial amplification degree, and the difference between the maximum and minimum instantaneous flow rates measured a predetermined number of times is equal to or greater than the predetermined flow rate. It is determined that less than a predetermined amount of water has entered. The ingress of a small amount of water is detected using the difference between the degree of amplification and the instantaneous flow rate.

Further, when the amount of water immersion is 0 cc, the minimum value of the instantaneous flow rate is a positive value when the gas is flowing, and a value near zero when the gas is not flowing. When the amount flooded over 20 cc, the minimum value of the instantaneous flow rate becomes less than negative prescribed flow rate, mu COM6 among the instantaneous flow rate which is a predetermined number of times measurement, if the minimum value is less than the negative prescribed flow rate, water less than a predetermined amount It is judged that has entered.

In addition, when water enters, the gas shut-off device easily enters the limit mode, and the μ COM 6 has entered less than a predetermined amount of water into the gas flow path only when the current mode is the limit mode. Judge.

The μ COM 6 starts the timer and determines whether a predetermined amount of water has been submerged in one week (168 hours) cycle every predetermined period.

JP 2010-25851 A

  However, in the above conventional configuration, when water or the like in the pipe enters the measuring unit of the gas shut-off device, μCOM 6 determines the upper and lower limits of the amplification degree, and confirms the difference between the maximum value and the minimum value of the instantaneous flow rate, Further, it is determined whether or not the current mode is the limit mode, and it is determined that a predetermined amount of water has entered, and a similar phenomenon occurs due to pressure fluctuation generated by installing an instrument such as GHP that varies the gas pressure. It may be erroneously determined that water has entered, and it is determined whether the propagation time or amplification level is less than the initial value only when the gas passage is blocked or the amount of water is large. If it is small, it can be judged only once a week, and the flow channel cross-sectional area where the flow rate measurement is originally performed is small due to inundation and the measurement flow channel is in an abnormal state. Defects such as continuing to accumulate Occur. This is inconvenient for gas consumers, has poor usability, and has the problem that the abnormal state can only be determined every week and the accuracy of abnormality detection is low.

  The present invention solves the above-mentioned problems. When a medium with different acoustic impedance, such as rainwater, which enters the pipe due to gas pipe construction or the like enters the measuring section of the gas shut-off device and enters a flooded state, the different acoustics are obtained. Providing a highly safe and easy-to-use gas shut-off device that ensures the safety of detecting the intrusion state due to the phenomenon caused by impedance at an early stage and immediately reporting to the gas company's center or stopping the gas supply To do.

In order to solve the above-described conventional problems, the gas cutoff device of the present invention includes a flow path through which a gas flows, a pair of ultrasonic transmitters / receivers disposed upstream and downstream of the flow path, and one of the ultrasonic transmission / reception devices. A propagation time measuring means for measuring a propagation time until the ultrasonic signal transmitted from the transmitter propagates through the gas and is received by the other ultrasonic transceiver, and adjusts the amplification degree of the received ultrasonic signal A flow rate detecting means comprising an amplification degree adjusting means, a flow rate calculating means for calculating an instantaneous flow rate value from a propagation time measured by the flow rate detecting means, and an amplification for determining the amplification degree adjusted by the amplification degree adjusting means. And an identification time measuring means for starting timing when the instantaneous flow rate value obtained by the flow rate calculating means is not more than a predetermined flow rate and the amplification degree adjusted by the amplification degree judging means is not less than a predetermined value; Obtained by the flow rate calculation means A measurement condition setting means by the instantaneous flow rate value sets the measurement conditions of the measurement frequency and the measurement cycle of the flow rate detecting means, during counting of the identification time measuring means, measured in the set measurement conditions in the measurement condition setting means a measurement ratio computing unit for obtaining a ratio of the number of measurements, when the ratio of the number of measurements obtained by the measurement ratio computing means is equal to or greater than a predetermined ratio, and penetration abnormality of media with different acoustic impedances with the gas in the flow channel An abnormality determining means for determining, and a blocking means for cutting off the supply of the gas when the abnormality determination is established by the abnormality determining means.

  According to the above invention, when a medium with different acoustic impedance, such as rainwater, enters the flow detection means, it propagates between the transceivers of the flow detection means through various routes, and the detected flow value fluctuates and the instantaneous flow value Is less than a predetermined value, and because it propagates through various routes, the phase is different when the transmitted ultrasonic wave arrives, the signal detected by the flow rate detection means is small, and it tries to increase the amplification level to increase the signal level. The measurement condition is changed to the maximum measurement condition in order to start the time measurement with a predetermined degree of amplification and to further stably measure the flow rate fluctuation width to be small, but a different medium by obtaining the measurement condition ratio during the predetermined time, for example, It can be determined that rainwater has infiltrated, and can be prevented by blocking the continued abnormal measurement state, and is highly safe.

  The gas shut-off device of the present invention is configured such that when a medium with different acoustic impedance enters the measuring unit, for example, rainwater or the like that has accumulated in the piping due to piping work or the like uses a gas appliance, so that the flow measuring unit inside the gas shut-off device In case of intrusion, the gas flow is constantly measured and the gas supply is always judged correctly and the gas supply is stopped at the time of abnormality judgment. It is possible to prevent monitoring in the state of.

The block diagram of the gas interruption | blocking apparatus in embodiment of this invention Control block diagram of the gas shutoff device Control block diagram of a conventional gas shut-off device

According to a first aspect of the present invention, there is provided a gas cutoff device comprising: a flow path through which a gas flows; a pair of ultrasonic transceivers disposed upstream and downstream of the flow path; and an ultrasonic signal transmitted from one of the ultrasonic transceivers Comprises propagation time measuring means for measuring the propagation time until the gas is received by the other ultrasonic transceiver and amplification adjusting means for adjusting the amplification degree of the received ultrasonic signal. A flow rate detection unit; a flow rate calculation unit that calculates an instantaneous flow rate value from a propagation time measured by the flow rate detection unit; an amplification degree determination unit that determines an amplification degree adjusted by the amplification degree adjustment unit; and the flow rate calculation unit When the instantaneous flow rate value obtained by the means is less than or equal to a predetermined flow rate and the amplification degree adjusted by the amplification degree judgment means is greater than or equal to a predetermined value, the identification time measurement means that starts timing and the flow rate computation means The flow rate is detected based on the instantaneous flow rate value. Measurements to determine the measurement condition setting means for setting a measurement condition of the measurement frequency and the measurement period of the unit, during counting of the identification time measuring means, the ratio of the number of measurements measured at set measurement conditions by the measurement condition setting means When the ratio of the number of measurements obtained by the ratio calculation means and the measurement ratio calculation means is equal to or greater than a predetermined ratio, an abnormality determination means for determining that an intrusion abnormality of a medium having an acoustic impedance different from that of the gas in the flow path occurs; When the abnormality determination is established by the abnormality determination means, the apparatus includes a cutoff means for cutting off the gas supply.

Then, the flow rate detection means periodically detects the flow rate signal by the measurement control means, amplifies the received signal to a predetermined level, and maximizes the measurement conditions to stably measure the flow rate when the flow rate value fluctuates. If the amplification level exceeds the predetermined value, the time measurement starts and the ratio of the maximum measurement conditions for stable measurement is obtained after the predetermined time has passed. For example, it is determined that the water supply has been inundated due to the intrusion of rainwater, etc., and the gas supply to the gas appliance is stopped. It is possible to prevent safety monitoring and gas consumption accumulation in the state, and it is highly safe.

  The second invention is a program for causing a computer to execute all or part of the means of the gas cutoff device of the first invention.

  And since it is a program, a part or all of the gas interruption | blocking apparatus of this invention can be easily implement | achieved using a microcomputer etc. Also, program distribution and installation can be simplified by recording on a recording medium or distributing a program using a communication line.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a diagram showing a schematic configuration diagram of a gas cutoff device in Embodiment 1 of the present invention, and FIG. 2 is a control block diagram of a control device mounted on the gas cutoff device.

  In FIG. 1, the gas shut-off device 9 is installed in the vicinity of a gate of each household, a garden, etc., and is piped to a place where various gas appliances used in each home are installed via the gas shut-off device 9. Is supplied. From the inlet 9a of the gas shut-off device 9, it is connected to a supply port 9e for supplying gas to each gas appliance via an inlet-side channel 9b, a bottom channel 9c, and an outlet-side channel 9d. An upstream transmitter / receiver 10 and a downstream transmitter / receiver 11 that transmit and receive an ultrasonic signal are attached to the channel 9c so as to face each other in the flow direction.

  FIG. 2 is a control block diagram of the apparatus. The flow rate detection means 12 includes a pair of ultrasonic transceivers (upstream transceiver 10 and downstream transceiver 11), switching means 13, transmission means 14, reception means 15, propagation time measurement means 16, amplitude determination means 17, And an amplification degree adjusting means 18. Note that the upstream transceiver 10 that transmits or receives ultrasonic waves and the downstream transceiver 11 that also receives or transmits ultrasound can be switched between transmission and reception by the switching means 13. Transmitting means 14 for outputting an ultrasonic signal is connected to the upstream transceiver 10 or the downstream transceiver 11, and the ultrasonic signal is received by the switching means 13 via the upstream transceiver 10 or the downstream transceiver 11. 15 is received.

  First, an ultrasonic signal is transmitted by the upstream transceiver 10 by the transmitter 14 and received by the downstream transceiver 11, and the propagation time is measured by the propagation time measuring unit 16 of the reception signal from the receiver 15. Next, switching is performed by the switching means 13, and similarly, an ultrasonic signal is transmitted from the downstream to the upstream, and the propagation time is measured. Then, the ultrasonic propagation time difference between the upstream side transceiver 10 and the downstream side transceiver 11 is obtained by the measurement control means 19 every predetermined period (for example, every 2 seconds). The ultrasonic signal received by the receiving unit 15 is determined by the amplitude determining unit 17 to determine whether the amplitude is an appropriate magnitude. If the ultrasonic signal is too large or too small, the amplitude adjusting unit 18 adjusts the ultrasonic signal so that the amplitude is appropriate. In the next measurement, the received signal is amplified with the adjusted amplification degree.

  Then, the flow rate calculation means 20 converts the flow rate to an instantaneous flow rate value based on the propagation time measured and determined for each predetermined period. The measurement condition setting means 21 determines the flow state in the flow path 9c from the obtained instantaneous flow rate value, and changes the measurement conditions such as the number of measurements and the measurement cycle so that the flow rate detection means 12 can always measure the flow rate stably. Control.

The measurement condition setting means 21 switches the number of measurements, the measurement cycle, etc. in a stepwise manner, or switches from a plurality of steps in a stepless manner.

  Note that the number of measurements is the number of measurements per measurement cycle. Increasing the number of times improves the measurement accuracy, but the current consumption increases, so the flow state is determined based on the measured instantaneous flow rate value. However, when the flow is unstable, the number of times of measurement is set to be optimal, such as increasing the number of times and decreasing the number of times when the flow is stable.

  In addition, the measurement cycle is set to a long period when the flow is stable to suppress power consumption, and is set to a short period when the flow is unstable, so that the accuracy is improved.

  When a medium with different acoustic impedance enters between the upstream side transceiver 10 and the downstream side transceiver 11 or when a gas appliance that changes pressure is used, the flow rate detecting means 12 detects irregular flow rate variations. Then, the measurement conditions are switched so that the flow rate can be detected with a stable small flow rate fluctuation range. The instantaneous flow rate value is input to the average flow rate calculation means 22, and a predetermined number of instantaneous flow rate values are collected and calculated as an average flow rate value. On the other hand, the amplification degree of the ultrasonic signal adjusted by the amplification degree adjusting means 18 is monitored by the amplification degree judging means 23. When the normal flow rate is increased, the ultrasonic signal reception sensitivity is lowered, so that the amplification degree tends to be increased.

  Here, when the instantaneous flow rate value obtained by the flow rate calculation means 20 is less than or equal to a predetermined flow rate and the amplification degree of the amplification degree determination means 23 is greater than or equal to a predetermined value, the identification time measurement means 24 uses the abnormality monitoring timer ( Start counting time from several minutes to 1 hour, etc. Then, the abnormality monitoring timer is started, and monitoring of the measurement condition of the measurement condition setting unit 21 is started by the measurement ratio calculation unit 25.

Then, the abnormality determination unit 26 monitors the appliance used at the obtained average flow rate or monitors whether there is an abnormality in the current flow rate detection unit 12. The abnormality determination means 26 obtains the frequency ratio measured under the measurement conditions set by the measurement condition setting means 21 in the measurement ratio calculation means 25, and when the measured frequency ratio becomes a predetermined ratio or more, a normal small flow rate is obtained. The flow rate detection means 12 determines that an abnormal flow rate is detected by, for example, inundation of rainwater or the like, and outputs a cut-off signal.

  In addition, the abnormality determination means 26 stores a time limit value for use time corresponding to each flow rate region, a monitor determination value for the maximum use flow rate, or the like. For example, when the hose that supplies gas to a stove or the like is disconnected for some reason, an abnormally large flow rate is generated, but the total flow cutoff value for monitoring such a condition and the maximum use time of the appliance normally The usage time cutoff time limit that defines the usage time limit time corresponding to the case of use for a much longer time is stored. By comparing and determining the set value and the average flow rate value by the abnormality determining means 26, the flow rate value does not exceed the maximum use flow rate value, or the use time of the appliance is set to the continuous use time limit corresponding to the registered flow rate. Monitor whether it has exceeded.

  When the abnormality determining means 26 determines that an abnormality has occurred, a cutoff signal is sent to the cutoff means 27 to stop the gas supply. In addition, the notification communication means 28 displays the shut-off state and shut-off content on a liquid crystal display element or the like, and notifies the center of the gas company that is monitoring the safety of the gas by communication such as a telephone line.

Next, the operation of the gas cutoff device 9 configured as described above will be described. After the gas shut-off device 9 is installed in the gas customer's house, when a medium with different acoustic impedance enters the flow path 9c, for example, rainwater collected in the gas pipe due to gas pipe replacement work, etc. In the flow path 9c located at the lower part of the gas cutoff device 9, and the upstream and downstream transceivers 10 and the downstream transceiver 11 may be submerged. The flow rate is detected by the flow rate detection means 12 in a state where media having different acoustic impedances are mixed. Usually, the acoustic impedance Z is given by Z = ρ × C from the medium density ρ and the velocity C. The acoustic impedance of water is Z = 1.48 and air is 0.0004, which is overwhelmingly liquid, that is, water has better ultrasonic wave propagation.

  Under such circumstances, the propagation time of the ultrasonic signal is measured as a detected value, and this signal is converted into an instantaneous flow rate value by the flow rate calculation means 20, but if there is water in the flow path 9c, the upstream side transceiver 10 Alternatively, the ultrasonic signal transmitted from the downstream transmitter / receiver 11 passes through various routes such as in water, in gas gas, from gas to water, or reflected between the wall surface of the flow path 9c and the water surface. The upstream transmitter / receiver 10 and the downstream transmitter / receiver 11 sequentially receive ultrasonic signals having different propagation times and phases through various routes of media having different acoustic impedances. As a result, the signal level received and output by the upstream transceiver 10 and the downstream transceiver 11 is small, and the size of the ultrasonic signal is unstable and fluctuates. Therefore, the propagation time value measured by the propagation time measuring means 16 changes even in a flow rate state where no instrument is used, and as a result, the flow value obtained by the flow rate calculating means 20 varies.

  Further, when the ultrasonic signal received by the receiving unit 15 becomes small and the signal level is determined to be below a predetermined value by the amplitude determining unit 17, the amplification adjusting unit 18 increases the amplification. Usually, when the instrument flow rate increases, the amplification degree increases. However, when a medium having a different acoustic impedance enters, the instrument is not used, but the amplification degree of the signal for detecting the flow rate signal gradually increases.

  When the instantaneous flow rate value obtained by the flow rate calculation means 20 changes every time it is measured at the time set by the measurement control means, the measurement condition setting means 21 periodically measures the measurement conditions so that the flow rate fluctuation range becomes smaller than the fluctuation state. Change control to. That is, an attempt is made to stably measure the flow rate by increasing the number of times of measurement by transmitting ultrasonic waves (the fluctuation range of the instantaneous flow rate value measured periodically is small).

When the identification time measuring unit 24 and the measurement ratio calculating unit 25 determine that the instantaneous flow rate value from the flow rate calculating unit 20 is equal to or smaller than the predetermined flow rate value and the amplification degree determining unit 23 has reached the predetermined amplification level or more, the gas cutoff device. 9, it is determined that the flow rate detection means 12 located at the lower part of 9 is in an abnormal state for some reason, and the identification time measurement means 24 starts measuring the abnormality monitoring timer of the flow rate detection means 12. At the same time, the measurement ratio calculation means 25 changes the measurement conditions such as the number of times of measurement of the flow rate in the abnormality monitoring timer of the identification time measurement means 24 and the measurement conditions such as the measurement cycle, and measures the ratio of the number of times the flow rate is measured. The obtained frequency ratio is compared with a predetermined ratio that is a frequency ratio under a predetermined measurement condition. Predetermined measurement condition, for example, the measurement condition number Ru is set to a predetermined number of times or more that is measured for each measurement period, or the number of times is measured for each measurement period is the measurement conditions that will be set equal to or less than a predetermined number of times.

Then, monitoring every flow rate measurement by the measurement control unit 19, abnormality superintendent of identification time measuring means 24
During the measurement of the visual timer, when the ratio of the number of times measured for each measurement period reaches a predetermined ratio, the flow rate detection means 12 is inundated, etc. A determination signal is output to the abnormality determination means 26.

  When the abnormality determining means 26 determines that an abnormality has occurred, a cutoff signal is sent to the cutoff means 27 to stop the gas supply. In addition, the notification communication means 28 displays the shut-off state and shut-off content on a liquid crystal display element or the like, and notifies the center of the gas company that is monitoring the safety of the gas by communication such as a telephone line. The gas company can immediately take countermeasures such as replacing the gas shut-off device, and can quickly avoid abnormal conditions.

On the other hand, the average flow rate calculation means 22 calculates the instantaneous flow rate value obtained by the flow rate calculation means 20 as an average flow rate value for every predetermined number. As for the obtained average flow rate, the abnormality determination means 26 stores a time limit value for use time corresponding to each flow rate region, a monitor determination value for the maximum use flow rate, or the like. For example, when the hose that supplies gas to a stove or the like is disconnected for some reason, an abnormally large flow rate is generated, but the total flow cutoff value for monitoring such a condition and the maximum use time of the appliance normally The usage time cutoff time limit that defines the usage time limit time corresponding to the case of use for a much longer time is stored.

  By comparing and determining the set value and the average flow rate value by the abnormality determining means 26, the flow rate value does not exceed the maximum use flow rate value, or the use time of the appliance is set to the continuous use time limit corresponding to the registered flow rate. Monitors whether it exceeds the limit, and outputs a cut-off signal if exceeded.

  Note that the configuration used in this embodiment is merely an example, and the usage pattern is not limited to this embodiment.

  As described above, rainwater or the like that has accumulated due to piping work or the like has entered the flow path 9c below the gas cutoff device 9 due to any cause, and the upstream side transceiver 10 or the downstream side located below the gas cutoff device 9 Amplification of the amplification degree adjusting means 18 for adjusting and controlling the flow rate value detected from the flow rate detecting means 12 and the change in the flow rate value or the detected flow rate signal when a medium having a different density or acoustic impedance has entered between the transceiver 11. The discrimination time measuring means 24 is activated with the trigger as a trigger, and the measurement conditions of the flow rate detection means 12 are monitored at a ratio set to the maximum measurement condition when the pulsation is large, thereby different acoustic impedances between the transceivers of the flow rate detection means 12 It is possible to detect an anomaly intruding the medium at an early stage.

  Therefore, if a medium with different density or acoustic impedance is inserted between the transmitter and the receiver, the abnormal flow rate is measured and integrated as an abnormal gas usage amount even though the instrument is not originally used, or the abnormal flow rate is detected. Prevent abnormal operations such as safety shut-offs from occurring continuously, and periodically monitor the gas shut-off device to safely monitor gas consumers who use gas appliances. Therefore, the safety and reliability are extremely high and the usability is high.

  As described above, the gas shut-off device according to the present invention can detect an abnormal state when it is flooded with rainwater or the like accumulated in piping work, etc., and can determine that it is difficult to continue security monitoring or flow measurement. Similarly, the present invention can be applied to all appliance monitoring devices such as when a large amount of back gas gas is mixed in a water meter.

9 Gas cutoff device 9c Flow path 10 Upstream transmitter / receiver (ultrasonic transmitter / receiver)
11 Downstream transmitter / receiver (ultrasonic transmitter / receiver)
DESCRIPTION OF SYMBOLS 12 Flow rate detection means 20 Flow rate calculation means 21 Measurement condition setting means 22 Average flow rate calculation means 23 Amplification degree determination means 24 Identification time measurement means 25 Measurement ratio calculation means 26 Abnormality determination means 27 Blocking means

Claims (2)

A flow path through which the gas flows, a pair of ultrasonic transceivers disposed upstream and downstream of the flow path, and an ultrasonic signal transmitted from one of the ultrasonic transceivers propagates the gas to the other A flow rate detecting means comprising a propagation time measuring means for measuring a propagation time until it is received by the ultrasonic transceiver, and an amplification degree adjusting means for adjusting the amplification degree of the received ultrasonic signal;
A flow rate calculation means for calculating an instantaneous flow rate value from the propagation time measured by the flow rate detection means;
An amplification degree determining means for determining the amplification degree adjusted by the amplification degree adjusting means;
An identification time measuring unit that starts timing when the instantaneous flow rate value obtained by the flow rate computing unit is equal to or less than a predetermined flow rate, and the amplification degree adjusted by the amplification degree determining unit is greater than or equal to a predetermined value;
A measurement condition setting means for setting a measurement condition of the number of measurements and a measurement cycle of the flow rate detection means based on the instantaneous flow rate value obtained by the flow rate calculation means;
During timing of the identified time measuring means, and measuring the ratio calculating means for calculating a ratio of the number of measurements measured at set measurement conditions by the measurement condition setting means,
When the ratio of the number of times of measurement obtained by the measurement ratio calculation means is equal to or greater than a predetermined ratio, an abnormality determination means that determines that an intrusion abnormality of a medium having an acoustic impedance different from the gas in the flow path is generated, and the abnormality determination means A shut-off means for shutting off the supply of the gas when abnormality determination is established;
Gas shut-off device with A program for causing a computer to function as all or part of means of the gas shut-off device according to claim 1.

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