JP2010025851A - Electronic gas meter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic gas meter capable of determining immersion of a small amount of water. <P>SOLUTION: The electronic gas meter 1 includes a transmission circuit 12 and a reception circuit 13, by which ultrasonic waves are transmitted from acoustic transducers TD1 and TD2 and then received. A received signal is amplified by an amplifier 13a. A CPU 14a of a μ COM 14 determines that a small amount of water less than a predetermined amount has entered a gas flow path when an amplification degree is a value equal to or larger than an initial amplification degree with a predetermined value added. In addition, the CPU 14a closes a gas cutoff valve 10. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electronic gas meter.

  Currently, 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. The passage flow rate is obtained by multiplying the flow rate by the sectional area of the gas flow path and the intermittent time. Furthermore, an electronic gas meter can be configured by displaying the integrated flow rate obtained by integrating the passing flow rate.

  Moreover, in the conventional electronic gas meter, water may enter the gas flow path. For example, in a gas meter for city gas, when a water pipe and a gas pipe are adjacent to each other and the water pipe corrodes and water leaks, the leaked water corrodes the gas pipe, and water enters the gas pipe. As a result, water may enter the gas flow path of the electronic gas meter. Further, even in a gas meter for LP gas, the possibility that water in the gas accumulates and the water accumulates in the gas flow path cannot be denied.

Therefore, conventionally, an electronic gas meter has been proposed that determines that the gas flow path is almost full when the amplification level of the ultrasonic signal received by the other transducer is small and the propagation time is small. ing.
Japanese Patent Publication No.7-119638

  However, in the conventional electronic gas meter, the ingress of water cannot be detected unless the gas flow path is almost full, and the ingress of a small amount of water cannot be detected.

  The present invention has been made to solve such conventional problems, and an object of the present invention is to provide an electronic gas meter capable of determining the ingress of a small amount of water.

  An electronic 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 up to a predetermined strength. Amplifying means for amplifying; and judging means for judging whether water has entered the gas flow path based on the amplification degree of the signal received by the amplifying means; When the amplification degree is equal to or greater than a value obtained by adding a predetermined value to the initial amplification degree, it is determined that less than a predetermined amount of water has entered the gas flow path.

  In the electronic gas meter of the present invention, the determination means determines that a predetermined amount or more of water has entered the gas flow path when the amplification degree is equal to or less than a value obtained by subtracting a specified value from the initial amplification degree. It is preferable to do.

  Further, in the electronic gas meter according to the present invention, when the propagation time of the ultrasonic signal transmitted from the transmitting unit and received by the receiving unit is equal to or shorter than a predetermined time, the determining unit has a predetermined amount or more in the gas flow path. It is preferable to determine that the water has entered.

  The electronic gas meter according to the present invention further includes a 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. The determination means determines that less than a predetermined amount of water has entered the gas flow path when the difference between the maximum and minimum flow rates measured by the measurement means a predetermined number of times is equal to or greater than the predetermined flow rate. It is preferable to do.

  Further, in the electronic gas meter according to the present invention, the determination means includes a flow of less than a predetermined amount of water in the gas flow path when the minimum flow rate of the flow rates measured by the measurement means is less than the negative specified flow rate. It is preferable to determine that has entered.

  The electronic gas meter of the present invention further includes mode determining means for determining the current mode based on the flow rate measured by the measuring means, and the mode determining means is configured to measure a specific amount in the specified number of measurements by the measuring means. When the above increase and decrease in the flow rate are repeated a specific number of times, the current mode is determined to be the limit mode, and the judging means enters the gas flow path only when the current mode is the limit mode. It is preferable to determine that less than a predetermined amount of water has entered.

  According to the electronic gas meter of the present invention, when the amplification degree is equal to or greater than a value obtained by adding a predetermined value to the initial amplification degree, it is determined that less than a predetermined amount of water has entered the gas flow path. Here, the present inventor has found that the degree of amplification tends to be as follows during water intrusion. That is, when a small amount of water enters the gas flow path, the ultrasonic waves are scattered, refracted, attenuated, etc. at the boundary surface between water and gas, and the propagation becomes unstable. For this reason, the received ultrasonic signal tends to be small, and the amplification degree tends to increase. For these reasons, the present inventors have found that the amplification degree tends to increase when a small amount of water enters. For this reason, when the amplification degree is equal to or greater than a value obtained by adding a predetermined value to the initial amplification degree, it is determined that less than a predetermined amount of water has entered the gas flow path, thereby detecting the entry of a small amount of water. Can do.

  Further, when the amplification degree is equal to or less than a value obtained by subtracting the specified value from the initial amplification degree, it is determined that a predetermined amount or more of water has entered the gas flow path. Here, when a large amount of water enters the gas flow path and becomes almost full, the transmission means to the reception means are filled with the same medium, and scattering, refraction, attenuation, etc. are less likely to occur. . For this reason, when a large amount of water permeates, the degree of amplification tends to decrease. Therefore, when the amplification degree is equal to or less than the value obtained by subtracting the specified value from the initial amplification degree, it is possible to detect the entry of a small amount of water by determining that a predetermined amount or more of water has entered the gas flow path. An electronic gas meter that can detect even a large amount of water can be provided.

  Further, when the propagation time of the ultrasonic signal is equal to or shorter than a predetermined time, it is determined that a predetermined amount or more of water has entered the gas flow path. Here, when a large amount of water enters the gas flow path, the propagation time tends to decrease. For this reason, when the propagation time is equal to or shorter than the predetermined time, it is possible to improve the detection accuracy for a large amount of water by determining that the water has entered the gas channel in a full state.

  If the difference between the maximum and minimum 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 gas flow path. Here, the electronic gas meter may be equipped with a function of determining a mixed gas that is a mixed state of gas and water or determining the intrusion of dust based on the amplification degree. For this reason, the possibility of misjudgment can be reduced by using the difference in flow rate without determining the ingress of water based only on the amplification degree, and even in an electronic gas meter that determines mixed gas and dust, a small amount of Water intrusion can be detected.

  Further, if the minimum flow rate among the flow rates measured a predetermined number of times is less than the negative specified flow rate, it is determined that less than a predetermined amount of water has entered the gas flow path. Here, when the user uses a gas stove or the like, the flow rate increases, and the difference between the maximum flow rate and the minimum flow rate among the predetermined number of measurements increases. For this reason, when the flow rate is less than the negative predetermined flow rate, it is determined that less than the predetermined amount of water has entered the gas flow path, so that the detection accuracy of a small amount of water can be improved without misjudging even when using the gas. Can be improved.

  Also, it is determined that less than a predetermined amount of water has entered the gas flow path only when the current mode is the limit mode. Here, when a small amount of water enters, the measured flow rate tends to increase or decrease. In particular, the limit mode is not a rush mode unless pulsation occurs, and only when a limit mode occurs, it is determined that less than a predetermined amount of water has entered the gas flow path. Can be improved.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing an electronic gas meter according to an embodiment of the present invention. The electronic gas meter 1 shown in FIG. 1 is an ultrasonic gas meter, and is disposed opposite to each other so as to be separated by a distance L in the gas flow path and at an angle θ with respect to the gas flow direction Y. There are also two acoustic transducers (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 transmits, in the form of a pulse burst, a signal for driving one of the transducers TD1 and TD2 to generate an ultrasonic signal 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.

  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 programs for processes 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.

  In addition, the CPU 14a uses the two transducers TD1 and TD2 to measure the gas flow rate at each sampling time, and measures the instantaneous flow rate by multiplying the measured gas flow rate by the cross-sectional area of the gas flow path (measurement means). It has. Furthermore, the CPU 14a has a mode determination function (mode determination function) for determining the current mode from the value of the instantaneous flow rate for the specified number of times measured by the measurement function.

  FIG. 3 is a state transition diagram showing modes determined by the CPU 14a shown in FIG. The mode shown in FIG. 3 shows a part of the mode determined by the CPU 14a of the electronic gas meter 1, and the electronic gas meter 1 may have other modes.

  In the example shown in FIG. 3, the electronic gas meter 1 is configured to transition between three modes of a small pulsation mode, a large pulsation mode, and a limit mode. The small pulsation mode is a mode in which the gas pulsation is the smallest among the three modes, and the gas pulsation increases as the large pulsation mode and the limit mode are entered. When the pulsation of gas increases, the gas flow rate varies, making it difficult to measure an accurate instantaneous flow rate. Therefore, the electronic gas meter 1 attempts to obtain a more accurate instantaneous flow rate by changing the mode when the pulsation increases, increasing the measurement interval, or increasing the number of measurements. Note that if the measurement interval is increased or the number of measurements is increased, the built-in battery is likely to be consumed. Therefore, the electronic gas meter 1 basically operates in the small pulsation mode to reduce the battery consumption. .

  This will be specifically described. First, it is assumed that the current mode is the small pulsation mode. In this case, the CPU 14a determines whether an increase or decrease of a specific amount (for example, 13 l / h or 5%) or more has been repeated a specific number of times (for example, 3 times) in the measurement of a specified number of times (for example, 15 times). If it is determined that the operation has been repeated, the CPU 14a switches the current mode from the small pulsation mode to the large pulsation mode.

  In the large pulsation mode, the CPU 14a determines whether an increase or decrease of a specific amount (for example, 15 l / h or 5%) or more has been repeated a specific number of times (for example, 5 times) in the measurement of a specified number of times (for example, 15 times). . If it is determined that the process has been repeated, the CPU 14a switches the current mode from the large pulsation mode to the limit mode.

  Further, in the limit mode, the CPU 14a determines whether the change amount of the instantaneous flow rate is within a specified range (5 l / h or 5%) continuously for a specified number of times (for example, 5 times). When this condition is satisfied, the CPU 14a switches the current mode from the limit mode to the large pulsation mode.

  Further, in the large pulsation mode, the CPU 14a determines whether the change amount of the instantaneous flow rate is within a specified range (3 l / h or 5%) continuously for a specified number of times (for example, 7 times). When this condition is satisfied, the CPU 14a switches the current mode from the large pulsation mode to the small pulsation mode.

  Reference is again made to FIGS. 1 and 2. In the present embodiment, the CPU 14a has a determination function (determination means) for determining whether water has entered the gas flow path based on the amplification degree of the received ultrasonic signal. In particular, the CPU 14a can distinguish and determine whether the intrusion is less than a predetermined amount of water or more than a predetermined amount of water in the gas flow path.

  FIG. 4 is a diagram showing experimental results obtained by measuring the amplification degree, instantaneous flow rate, and propagation time for each inundation amount when an arbitrary flow rate of gas flows. In the experiment shown in FIG. 4, 64 measurements are performed for each value, the maximum value and the minimum value are shown for the amplification degree, and the maximum value, the minimum value, These differences are shown, and the average value for both forward and reverse is shown for the propagation time.

  As shown in FIG. 4, when the amount of water immersion is 0 cc, the amplification degree is “20” in both the maximum value and the minimum value. The value “20” is an initial value of the amplification degree. Then, the amount of water immersion increases, and in the range of 20 cc to 70 cc water immersion, the degree of amplification is at least “35” or more. For this reason, 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 amount of water immersion is 80 cc and the gas flow path is almost full, the amplification degree is “10” at the maximum and “8” at the minimum. For this reason, the amplification degree is equal to or less than a value obtained by subtracting a specified value (for example, “10”) from the initial amplification degree.

  The reason why the amplification degree changes in this way is as follows. When a small amount of water, such as 20 to 70 cc, enters the gas flow path, the ultrasonic waves are scattered, refracted, attenuated, etc. at the interface between water and gas, and the propagation becomes unstable. For this reason, the received ultrasonic signal tends to be small, and the amplification degree tends to increase. On the other hand, when a large amount of water of 80 cc or the like enters the gas flow path and becomes almost full, the space between the acoustic transducers TD1 and TD2 is filled with the same medium. For this reason, there is no interface between water and gas, scattering, refraction, attenuation and the like are less likely to occur, and the degree of amplification tends to decrease. For these reasons, the degree of amplification tends to increase for the ingress of a small amount of water, and tends to decrease for the ingress of a large amount of water.

  As described above, in the present embodiment, when the amplification degree is equal to or greater than the value obtained by adding a predetermined value to the initial amplification degree, less than a predetermined amount of water has entered, and the specified value is subtracted from the initial amplification degree. When the value is less than or equal to the value, it can be determined that a predetermined amount or more of water has entered.

  In addition, when a large amount of water of 50 cc or more enters, the propagation time tends to be short. That is, as shown in FIG. 4, the propagation time is about 248 μs in both forward and reverse directions when the water immersion amount is 0 cc to 40 cc. On the other hand, when the amount of water immersion is 50 cc to 80 cc, the propagation time decreases to less than 134 μs. This is because water has a property of faster light propagation than city gas or LP gas.

  Therefore, the CPU 14a determines that water of a predetermined amount or more has entered when the initial amplification degree is equal to or less than the value obtained by subtracting the specified value and the propagation time is equal to or less than a predetermined time (for example, 134 μs). The determination accuracy can be improved with respect to intrusion of a predetermined amount or more of water.

  Moreover, when 20 cc or more of water permeates, the instantaneous flow rate tends to be as follows. That is, when the amount of water immersion is 0 cc, refraction, scattering, and the like at the interface between water and gas do not occur, so the instantaneous flow rate is measured almost accurately. For this reason, the difference between the maximum value and the minimum value of the instantaneous flow rate becomes very small. However, when 20 cc or more of water enters, the difference between the maximum value and the minimum value of the instantaneous flow rate is greater than a predetermined flow rate (for example, 174 l / h) due to the influence of water. As described above, the difference between the maximum value and the minimum value of the instantaneous flow rate tends to increase due to water intrusion.

  Therefore, the CPU 14a has an amplification degree equal to or greater than a value obtained by adding a predetermined value to the initial amplification degree, and the difference between the maximum and minimum of the instantaneous flow rates measured a predetermined number of times is equal to or greater than the predetermined flow rate. If it is, it is determined that less than a predetermined amount of water has entered. Thereby, it is possible to improve the determination accuracy when less than a predetermined amount of water has entered.

  In particular, some electronic gas meters 1 determine a mixed gas that is a mixed state of gas and air based on the degree of amplification, or determine that dust has entered the gas flow path. For this reason, it is possible to reduce the possibility of misjudgment of mixed gas and dust by using the difference in instantaneous flow rate without judging the ingress of water only by the amplification degree. Even in the electronic gas meter to be determined, the entry of a small amount of water can be detected.

  Further, when 20 cc or more of water enters, the minimum instantaneous flow rate tends to be as follows. That is, when the amount of water immersion is 0 cc, refraction, scattering, etc. at the interface between water and gas do not occur, so the instantaneous flow rate is measured almost accurately. For this reason, the minimum value of the instantaneous flow rate is a positive value when the gas is flowing, and is a value near zero even if the gas is not flowing. However, when 20 cc or more of water enters, the minimum value of the instantaneous flow rate is less than the negative specified flow rate (for example, −80 l / h) due to the influence of water. As described above, the minimum value of the instantaneous flow rate tends to become a certain large value on the negative side due to water intrusion.

  Therefore, in addition to the above conditions, the CPU 14a determines that less than a predetermined amount of water has entered when the minimum instantaneous flow rate measured a predetermined number of times is less than the negative specified flow rate. Thereby, it is possible to improve the determination accuracy when less than a predetermined amount of water has entered.

  In particular, when the user uses a gas stove or the like, the instantaneous flow rate may increase, and the difference between the maximum flow rate and the minimum flow rate among the predetermined number of measurements may increase. For this reason, when the instantaneous flow rate is less than the negative specified flow rate, it is determined that less than a predetermined amount of water has entered the gas flow path, so that the accuracy of detecting a small amount of water can be avoided without misjudging even when using gas. Can be improved.

  Further, when water enters, the instantaneous flow rate is disturbed due to refraction and scattering of ultrasonic waves as described above. For this reason, the electronic gas meter 1 easily enters the limit mode. Therefore, the CPU 14a can improve the detection accuracy of a small amount of water by determining that less than a predetermined amount of water has entered the gas flow channel only when the current mode is the limit mode.

  Next, the detailed operation of the electronic gas meter 1 according to the present embodiment will be described with reference to a flowchart. FIG. 5 is a flowchart showing processing related to water detection of the electronic gas meter 1 according to the present embodiment.

  As shown in FIG. 5, the CPU 14a first starts a timer (S1). Next, the CPU 14a determines whether or not a predetermined period has elapsed since the timer start (S2). When it is determined that the predetermined period has not elapsed (S2: NO), the CPU 14a determines whether or not the amplification degree is equal to or less than a value obtained by subtracting the specified value from the initial amplification degree (S3).

  If it is determined that the value is not equal to or less than the value obtained by subtracting the specified value from the initial amplification degree (S3: NO), the CPU 14a determines whether or not the current mode is the limit mode (S4). If it is determined that the mode is not the limit mode (S4: NO), the process proceeds to step S2. On the other hand, when it is determined that the limit mode is selected (S4: YES), the CPU 14a determines whether or not the amplification degree is equal to or greater than a value obtained by adding a predetermined value to the initial amplification degree (S5).

  If it is determined that the value is not equal to or greater than a value obtained by adding a predetermined value to the initial amplification degree (S5: NO), the process proceeds to step S2. On the other hand, if it is determined that the initial amplification degree is equal to or greater than the value obtained by adding a predetermined value (S5: YES), the CPU 14a determines that the difference between the maximum and minimum of the instantaneous flow rates measured a predetermined number of times is obtained. It is determined whether the flow rate is equal to or greater than a predetermined flow rate (S6). Here, a GHP (gas heat pump) is connected to the electronic gas meter 1, and pulsation may occur due to vibration caused by the GHP, and the instantaneous flow rate may fluctuate. Therefore, it is desirable that the predetermined flow rate be a value that is equal to or greater than the pulsation caused by GHP. This is because it is possible to prevent the difference between the maximum instantaneous flow rate and the minimum instantaneous flow rate from exceeding a predetermined flow rate by GHP.

  If it is determined that the difference between the maximum instantaneous flow rate and the minimum instantaneous flow rate is not equal to or greater than the predetermined flow rate (S6: NO), the process proceeds to step S2. On the other hand, when it is determined that the difference between the maximum instantaneous flow rate and the minimum instantaneous flow rate is greater than or equal to the predetermined flow rate (S6: YES), the CPU 14a determines whether or not the minimum instantaneous flow rate is less than the negative specified flow rate. (S7). Here, the negative specified flow rate is desirably set to a value less than the lower limit value due to the pulsation of GHP. This is because it is possible to prevent the minimum instantaneous flow rate from becoming less than the negative specified flow rate by GHP.

  If it is determined that the minimum instantaneous flow rate is not less than the negative specified flow rate (S7: NO), the process proceeds to step S2. On the other hand, when determining that the minimum instantaneous flow rate is less than the negative specified flow rate (S7: YES), the CPU 14a increments the value of the counter (S8). Then, the CPU 14a determines whether or not the counter value has reached a specific value (the specific value is an integer equal to or greater than 2 and is, for example, “15”) (S9).

  If it is determined that the specific value has not been reached (S9: NO), the process proceeds to step S2. On the other hand, if it is determined that the specific value has been reached (S9: YES), the CPU 14a determines that a small amount of water less than the predetermined amount has been detected (S10). Thereafter, the CPU 14a drives the gas shut-off valve 10 to shut it off (S11). Then, the process shown in FIG. As described above, in this embodiment, the gas cutoff valve 10 is not driven by detecting water less than a predetermined amount only once, and the gas cutoff valve 10 is driven when water less than a predetermined amount is detected a plurality of times. I am letting. Thereby, the situation where the gas cutoff valve 10 is driven and shut off due to erroneous determination is prevented.

  In particular, gas should not be used when water enters. For this reason, the gas shut-off valve 10 should not be easily opened when water enters, and there is a possibility that the user cannot easily open the valve. For this reason, if it is interrupted due to an erroneous determination, the user cannot open his / her own, which is very disadvantageous. Therefore, when the amount of water less than a predetermined amount is detected a plurality of times as described above, the gas shutoff valve 10 is driven to prevent the blockage due to a misjudgment when the influence by the misjudgment of the blockage at the time of water detection is large. it can.

  By the way, when it is determined in step S3 that the value is equal to or less than a value obtained by subtracting the specified value from the initial amplification degree (S3: YES), the CPU 14a determines whether the propagation time is equal to or less than a predetermined time (S12). . If it is determined that the propagation time is not less than the predetermined time (S12: NO), the process proceeds to step S2.

  On the other hand, when determining that the propagation time is equal to or shorter than the predetermined time (S12: YES), the CPU 14a increments the value of the counter (S13). Then, the CPU 14a determines whether or not the counter value has reached a specific value (the specific value is an integer equal to or greater than 2 and is, for example, “15”) (S14). If it is determined that the specific value has not been reached (S14: NO), the process proceeds to step S2. On the other hand, if it is determined that the specific value has been reached (S14: YES), the CPU 14a determines that a large amount of water equal to or greater than the predetermined amount has been detected (S15).

  Thereafter, the CPU 14a drives the gas shut-off valve 10 to shut it off (S11). Then, the process shown in FIG. As described above, in the present embodiment, even when a predetermined amount or more of water is detected, the gas cutoff valve 10 is driven by detecting water less than the predetermined amount a plurality of times, thereby preventing a blockage due to an erroneous determination. Similarly, by driving the gas shut-off valve 10 when water of a predetermined amount or more is detected a plurality of times, when the influence due to the misjudgment of the shut-off at the time of water detection is extremely large, the blockage by the misjudgment is prevented Yes.

  If it is determined in step S2 that a predetermined period has elapsed since the timer start (S2: YES), the CPU 14a clears the value of the counter (S16). Thereafter, the process proceeds to step S1. Thus, in this embodiment, the value of the counter is cleared every time a predetermined period has elapsed. Here, when the value of the counter is not cleared, there is a possibility that the counter is incremented and the gas shut-off valve 10 is shut off every time an intrusion of water is erroneously determined. However, since the counter value is cleared, it is possible to prevent interruption due to accumulation of erroneous determinations.

  The predetermined period is desirably one week (168 hours). The gas usage pattern is typically one cycle per week. Therefore, by setting the predetermined period to one week, it is possible to reliably detect water intrusion without erroneous determination.

  Thus, according to the electronic gas meter 1 according to the present embodiment, when the amplification degree is equal to or greater than the value obtained by adding the predetermined value to the initial amplification degree, less than a predetermined amount of water has entered the gas flow path. Judge. Here, the present inventor has found that the degree of amplification tends to be as follows during water intrusion. That is, when a small amount of water enters the gas flow path, the ultrasonic waves are scattered, refracted, attenuated, etc. at the boundary surface between water and gas, and the propagation becomes unstable. For this reason, the received ultrasonic signal tends to be small, and the amplification degree tends to increase. For these reasons, the present inventors have found that the amplification degree tends to increase when a small amount of water enters. For this reason, when the amplification degree is equal to or greater than a value obtained by adding a predetermined value to the initial amplification degree, it is determined that less than a predetermined amount of water has entered the gas flow path, thereby detecting the entry of a small amount of water. Can do.

  Further, when the amplification degree is equal to or less than a value obtained by subtracting the specified value from the initial amplification degree, it is determined that a predetermined amount or more of water has entered the gas flow path. Here, when a large amount of water enters the gas flow path and becomes nearly full, one acoustic transducer TD1, TD2 to the other acoustic transducer TD1, TD2 are filled with the same medium. Scattering, refraction, attenuation and the like are less likely to occur. For this reason, when a large amount of water permeates, the degree of amplification tends to decrease. Therefore, when the amplification degree is equal to or less than the value obtained by subtracting the specified value from the initial amplification degree, it is possible to detect the entry of a small amount of water by determining that a predetermined amount or more of water has entered the gas flow path. The electronic gas meter 1 that can detect even a large amount of water can be provided.

  Further, when the propagation time of the ultrasonic signal is equal to or shorter than a predetermined time, it is determined that a predetermined amount or more of water has entered the gas flow path. Here, when a large amount of water enters the gas flow path, the propagation time tends to decrease. For this reason, when the propagation time is equal to or shorter than the predetermined time, it is possible to improve the detection accuracy for a large amount of water by determining that the water has entered the gas channel in a full state.

  If the difference between the maximum and minimum instantaneous flow rates measured a predetermined number of times is greater than or equal to the predetermined flow rate, it is determined that less than a predetermined amount of water has entered the gas flow path. Here, the electronic gas meter may be equipped with a function of determining a mixed gas that is a mixed state of gas and water or determining the intrusion of dust based on the amplification degree. For this reason, it is possible to reduce the possibility of misjudgment by using the difference in instantaneous flow rate without determining the ingress of water only by the amplification degree. In the electronic gas meter 1 for determining mixed gas and dust, Intrusion of a small amount of water can be detected.

  Further, if the minimum flow rate among the instantaneous flow rates measured a predetermined number of times is less than the negative specified flow rate, it is determined that less than a predetermined amount of water has entered the gas flow path. Here, when the user uses a gas stove or the like, the instantaneous flow rate increases and the difference between the maximum flow rate and the minimum flow rate among the predetermined number of measurements increases. For this reason, when the instantaneous flow rate is less than the negative predetermined flow rate, it is determined that less than the predetermined amount of water has entered the gas flow path. Can be improved.

  Also, it is determined that less than a predetermined amount of water has entered the gas flow path only when the current mode is the limit mode. Here, when a small amount of water enters, the measured instantaneous flow rate tends to increase or decrease. In particular, the limit mode is not a rush mode unless pulsation occurs, and only when a limit mode occurs, it is determined that less than a predetermined amount of water has entered the gas flow path. Can be improved.

  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 above embodiment, each value is not limited to the above value, and can be changed as appropriate. Further, it is desirable that each value for judging the ingress of water can be changed in the electronic gas meter 1. Thus, for example, in a gas meter to which no GHP is connected, it is considered that there is little pulsation. For example, in determining whether the difference between the maximum value and the minimum value of the instantaneous flow rate is greater than or equal to a predetermined flow rate, the value of the predetermined flow rate is decreased. It is also possible to do.

  Furthermore, in this embodiment, when water is detected and the gas shut-off valve 10 is shut off, various displays may be performed, and the shut-off return can be returned only on the center side so that the user cannot easily return. You may leave it.

It is a lineblock diagram showing the electronic gas meter concerning the embodiment of the present invention. FIG. 2 is a configuration diagram showing the inside of μCOM shown in FIG. 1. FIG. 3 is a state transition diagram illustrating modes determined by a CPU illustrated in FIG. 2. It is a figure which shows the experimental result which measured the amplification degree at the time of flowing gas of arbitrary flow rates, instantaneous flow rate, and propagation time for every inundation amount. It is a flowchart which shows the process in connection with the water detection of the electronic gas meter which concerns on this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electronic 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 (determination means, measurement means, mode determination means)
14b ... ROM
14c ... RAM
14d ... bus line 15 ... display TD1, TD2 ... acoustic transducer (transmitting means, receiving means)

Claims (6)

Transmission means for intermittently transmitting ultrasonic signals in the gas flow path;
Receiving means for receiving the ultrasonic signal;
Amplifying means for amplifying the signal received by the receiving means to a predetermined strength;
Determination means for determining whether water has entered the gas flow path based on the amplification degree of the signal received by the amplification means,
The electronic gas meter, wherein the determination means determines that less than a predetermined amount of water has entered the gas flow path when the amplification degree is equal to or greater than a value obtained by adding a predetermined value to the initial amplification degree. The determination means determines that a predetermined amount or more of water has entered the gas flow path when the amplification degree is equal to or less than a value obtained by subtracting a specified value from the initial amplification degree. An electronic gas meter as described in 1. The determining means determines that a predetermined amount or more of water has entered the gas flow path when the propagation time of the ultrasonic signal transmitted from the transmitting means and received by the receiving means is equal to or shorter than a predetermined time. The electronic gas meter according to claim 2. Further comprising a 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,
The determination unit determines that less than a predetermined amount of water has entered the gas flow path when the difference between the maximum and minimum flow rates measured by the measurement unit a predetermined number of times is equal to or greater than a predetermined flow rate. The electronic gas meter according to any one of claims 1 to 3, wherein the electronic gas meter is provided. The determination unit determines that less than a predetermined amount of water has entered the gas flow path when the minimum flow rate among the flow rates measured by the measurement unit a predetermined number of times is less than a negative specified flow rate. The electronic gas meter according to claim 4. Further comprising mode determining means for determining the current mode based on the flow rate measured by the measuring means;
The mode determining means determines that the current mode is a limit mode when the increase and decrease in flow rate of a specific amount or more are repeated a specific number of times in the measurement of the specified number of times by the measurement means,
6. The method according to claim 4, wherein the determination unit determines that less than a predetermined amount of water has entered the gas flow path only when the current mode is a limit mode. The electronic gas meter as described.

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