Abstract:
The present invention provides a flow rate measuring device capable of simplifying calculation, reducing the amount of a memory required for the calculation, absorbing variations due to manual operation and depending on the state of ignition, and improving the accuracy of appliance identification by using a configuration in which the features of appliances are extracted. The flow rate measuring device is formed of a difference value conversion unit  112  for converting the difference values of the flow rate measured at constant time intervals by an ultrasonic flowmeter  104 ; an appliance feature extraction unit  214  for creating an appliance feature code string indicating the feature of each appliance by making comparison and judgment using the third last code, the second last code, the last code and the current code of the codes obtained at constant time intervals and by performing code deletion, etc.; and an identification unit  116  for performing appliance identification by comparing the appliance feature code string with an appliance inherent feature code string indicating the feature code string inherent in each appliance.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a technology for properly identifying an appliance that uses fluid by detecting the change of the flow rate of the fluid. 
       BACKGROUND ART 
       [0002]    Conventionally, in a fluid piping system having a gas meter instrument, as a gas meter instrument for identifying an appliance being used, an instrument described in Patent document 1 is available. Its configuration will be described referring to  FIG. 12 .  FIG. 12  is a block diagram showing a conventional gas meter. 
         [0003]    As shown in  FIG. 12 , a gas meter instrument  1  is disposed in a flow passage  6  connected to a household gas supply pipe and is equipped with a flow rate measurement unit  3  for measuring the flow rate of gas at constant time intervals; a calculation unit  4  for obtaining the difference values of flow rate values output from the flow rate measurement unit  3 ; and a comparison judgment unit  7  for comparing the difference values calculated by the calculation unit  4  with a change judgment value registered in a storage unit  5  and for judging the change of the usage state of a gas appliance. The calculation unit  4 , the comparison judgment unit  7  and a gas shut-off valve  2  are controlled by a control circuit  116 . 
         [0004]    The above-mentioned gas meter instrument  1  sequentially calculates the change of the difference values of the instantaneous flow rate output from the flow rate measurement unit  3  and judges the change of the usage state of the gas appliance according to the amount of the change, wherein registered data is compared with the change (difference values) of the gas flow rate measured, whereby the identification of gas appliances  13 ,  14  and  15  is made possible. 
         [0005]    Furthermore, as a conventional method for identifying an appliance that uses fluid, a method described in Patent document 2 is available. Its configuration will be described referring to  FIG. 13 .  FIG. 13  is a block diagram showing a conventional flow rate measuring device. 
         [0006]    As shown in  FIG. 13 , a calculation unit  108  calculates the difference values of the gas flow rate measured by an ultrasonic flowmeter  104  at constant time intervals and a difference value conversion unit  112  classifies the difference values obtained at constant time intervals into predetermined classifications using the flow rate classification table  110   a  stored in a flow rate classification table storage unit  110  and converts the classifications into predetermined codes. An appliance identification unit  116  compares the code string generated by a code string generation unit  114  using the codes converted by the difference value conversion unit  112  with an appliance inherent feature code string being inherent in each appliance and stored in an appliance inherent code string information storage unit  118  to perform appliance identification. 
         [0007]    In the above-mentioned configuration, code values obtained by coding (converting) the difference values of the flow rate are used, and the calculation is simplified when appliance identification is performed, whereby the speed of the calculation and the accuracy of the appliance identification are improved while the amount of memory required for the calculation, for example, is reduced.
   Patent document 1: Japanese Patent Application Laid-Open Publication No. 2006-313114   Patent document 2: Japanese Patent Application Laid-Open Publication No. 2008-309498   
 
       SUMMARY OF THE INVENTION 
     Problem to be Solved by the Invention 
       [0010]    However, in the conventional configuration described above, for example, in a gas table that is ignited using a pilot burner, its flow rate decreases when the user checks flame and releases his/her hand from its knob, and the time until the hand is released varies, or the slow ignition time of a fan heater, for example, varies depending on the state of ignition; hence, there is a problem that an erroneous judgment occurs when the flow rate difference values and the code string are compared with preliminarily registered data. 
         [0011]    In order to solve the conventional problem described above, the present invention is intended to simplify calculation, to reduce the amount of a memory required for the calculation, to absorb variations due to manual operation and depending on the state of ignition, and to improve the accuracy of appliance identification by using a configuration in which the feature of an appliance is extracted. 
       Means for Solving the Problem 
       [0012]    In order to solve the conventional problem described above, a flow rate measuring device according to the present invention is equipped with a flow rate measurement unit for measuring the flow rate of fluid at constant time intervals; a calculation unit for calculating the difference values of the flow rate measured by the flow rate measurement unit at constant time intervals; a flow rate classification table in which the classifications of a plurality of difference values depending on the magnitudes of the difference values are associated with codes representing the classifications; a difference value conversion unit for converting the difference values calculated by the calculation unit into codes on the basis of the flow rate classification table; an appliance feature extraction unit for generating an appliance feature code string indicating the feature of an appliance from the codes obtained at constant time intervals by the difference value conversion unit; and an appliance identification unit for performing appliance identification by comparing the appliance feature code string with an appliance inherent feature code string indicating the feature code string inherent in each appliance, wherein the appliance feature extraction unit is configured so as to create an appliance feature code string by making comparison and judgment using the fourth last code, the third last code, the second last code, the last code and the current code obtained by the difference value conversion unit and by performing code deletion, etc.; 
         [0013]    With this configuration, an appliance feature can be extracted depending on the degree of increase/decrease of the flow rate, that is, the increase/decrease of the code, and the variations thereof can be absorbed, whereby stable appliance feature extraction can be accomplished. 
       Advantageous Effect of the Invention 
       [0014]    The flow rate measuring device according to the present invention can simplify calculation, reduce the amount of a memory required for the calculation, absorb variations due to manual operation and depending on the state of ignition, and improve the accuracy of appliance identification by using a configuration in which the feature of an appliance is extracted. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a block diagram of a flow rate measuring device according to Embodiments 1 to 5 of the present invention; 
           [0016]      FIG. 2  is a view showing an example of a flow rate classification table according to Embodiments 1 to 5 of the present invention; 
           [0017]      FIG. 3(   a ) is a view showing a concept in which the flow rate difference values at the time when a gas appliance A is used are classified according to a flow rate classification table in Embodiment 1 of the present invention,  FIG. 3(   b ) is a graph showing a flow rate characteristic at the time when the gas appliance A is used,  FIG. 3(   c ) is a graph showing classified codes at the time when the gas appliance A is used, and  FIG. 3(   d ) is a graph showing a code string in which the feature at the time when the gas appliance A is used is extracted; 
           [0018]      FIG. 4(   a ) is a view showing a concept in which the flow rate difference values at the time when a gas appliance B is used are classified according to the flow rate classification table in Embodiment 1 of the present invention,  FIG. 4(   b ) is a graph showing a flow rate characteristic at the time when the gas appliance B is used,  FIG. 4(   c ) is a graph showing classified codes at the time when the gas appliance B is used, and  FIG. 4(   d ) is a graph showing a code string in which the feature at the time when the gas appliance B is used is extracted; 
           [0019]      FIG. 5(   a ) is a view showing a concept in which the flow rate difference values at the time when a gas appliance C is used are classified according to the flow rate classification table in Embodiment 1 of the present invention,  FIG. 5(   b ) is a graph showing a flow rate characteristic at the time when the gas appliance C is used,  FIG. 5(   c ) is a graph showing classified codes at the time when the gas appliance C is used, and  FIG. 5(   d ) is a graph showing a code string in which the feature at the time when the gas appliance C is used is extracted; 
           [0020]      FIG. 6(   a ) is a view showing a concept in which the flow rate difference values at the time when the gas appliance C is used are classified according to the flow rate classification table in Embodiment 1 of the present invention,  FIG. 6(   b ) is a graph showing a flow rate characteristic at the time when the gas appliance C is used,  FIG. 6(   c ) is a graph showing classified codes at the time when the gas appliance C is used, and  FIG. 6(   d ) is a graph showing a code string in which the feature at the time when the gas appliance C is used is extracted; 
           [0021]      FIG. 7(   a ) is a view showing a concept in which the flow rate difference values at the time when the gas appliance A is used are classified according to the flow rate classification table in Embodiment 2 of the present invention,  FIG. 7(   b ) is a graph showing a code string obtained by extracting the feature at the time when the gas appliance A is used,  FIG. 7(   c ) is a view showing a concept in which the flow rate difference values at the time when the gas appliance C is used are classified according to the flow rate classification table in Embodiment 1 of the present invention, and  FIG. 7(   d ) is a graph showing a code string in which the feature at the time when the gas appliance C is used is extracted; 
           [0022]      FIG. 8(   a ) is a view showing a concept in which the flow rate difference values at the time when a gas appliance D is used are classified according to the flow rate classification table in Embodiment 3 of the present invention,  FIG. 8(   b ) is a graph showing a flow rate characteristic at the time when the gas appliance D is used,  FIG. 8(   c ) is a graph showing classified codes at the time when the gas appliance D is used, and  FIG. 8(   d ) is a graph showing a code string in which the feature at the time when the gas appliance D is used is extracted; 
           [0023]      FIG. 9(   a ) is a view showing a concept in which the flow rate difference values at the time when a gas appliance E is used are classified according to the flow rate classification table in Embodiment 4 of the present invention,  FIG. 9(   b ) is a graph showing a flow rate characteristic at the time when the gas appliance E is used,  FIG. 9(   c ) is a graph showing classified codes at the time when the gas appliance E is used, and  FIG. 9(   d ) is a graph showing a code string in which the feature at the time when the gas appliance E is used is extracted; 
           [0024]      FIG. 10(   a ) is a view showing a concept in which the flow rate difference values at the time when a gas appliance F is used are classified according to the flow rate classification table in Embodiment 4 of the present invention,  FIG. 10(   b ) is a graph showing a flow rate characteristic at the time when the gas appliance F is used,  FIG. 10(   c ) is a graph showing classified codes at the time when the gas appliance F is used, and  FIG. 10(   d ) is a graph showing a code string in which the feature at the time when the gas appliance F is used is extracted; 
           [0025]      FIG. 11(   a ) is a view showing a concept in which the flow rate difference values at the time when the gas appliance C is used are classified according to the flow rate classification table in Embodiment 5 of the present invention,  FIG. 11(   b ) is a graph showing a flow rate characteristic at the time when the gas appliance C is used,  FIG. 11(   c ) is a graph showing classified codes at the time when the gas appliance C is used, and  FIG. 11(   d ) is a graph showing a code string in which the feature at the time when the gas appliance C is used is extracted; 
           [0026]      FIG. 12  is a block diagram showing the conventional gas meter; and 
           [0027]      FIG. 13  is a block diagram showing the conventional flow rate measuring device. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0028]    A first invention has a configuration equipped with a flow rate measurement unit for measuring the flow rate of fluid flowing through a flow passage at constant time intervals; a calculation unit for calculating the difference values of the flow rate measured by the flow rate measurement unit at constant time intervals; a flow rate classification table in which the classifications of a plurality of difference values depending on the magnitudes of the difference values are associated with codes representing the classifications; a difference value conversion unit for converting the difference values calculated by the calculation unit into codes on the basis of the flow rate classification table; an appliance feature extraction unit for generating an appliance feature code string indicating the feature of an appliance from the codes obtained at constant time intervals by the difference value conversion unit; and an appliance identification unit for performing appliance identification by comparing the appliance feature code string with an appliance inherent feature code string indicating the feature code string inherent in each appliance, wherein in the case that the last code of the codes obtained by the difference value conversion unit is larger than the second last code and the last code is larger than the current code or in the case that the last code is smaller than the second last code and the last code is smaller than the current code, the appliance feature extraction unit stores the current code in the appliance feature code string; and in the other cases, the extraction unit overwrites the current code on the last code stored in the appliance feature code string to compress the appliance feature code string. 
         [0029]    With this configuration, an appliance feature can be extracted depending on the degree of increase/decrease of the flow rate, that is, the increase/decrease of the code. 
         [0030]    A second invention is characterized in that the appliance feature extraction unit according to the first invention, in particular, is configured so as to add a minus sign to codes in the case that the difference values calculated by the calculation unit are minus and the codes obtained by the difference value conversion unit are other than a predetermined code and so as not to overwrite the current code on the last code stored in the appliance feature code string in the case that the last code is plus and the current code is minus. 
         [0031]    With this configuration, increase/decrease information can be added to the feature of each appliance depending on the increase/decrease of the code, whereby identification can be performed depending on the increase/decrease even if the same code is used. 
         [0032]    A third invention is characterized in that the appliance feature extraction unit according to the first invention, in particular, is configured so as to delete the last code and the second last code stored in the appliance feature code string and to overwrite the current code on the second last code stored in the appliance feature code string to compress the appliance feature code string in the case that the difference between the last code and the second last code is equal to or less than a predetermined value and the second last code is smaller than the current code when the change of the codes obtained by the difference value conversion unit has an N-shaped characteristic, that is, the second last code is larger than the third last code, the last code is smaller than the second last code, and the current code is larger than the last code, or in the case that the difference between the last code and the second last code is equal to or less than the predetermined value and the second last code is larger than the current code when the change of the codes obtained by the difference value conversion unit has an inverted N-shaped characteristic, that is, the second last code is smaller than the third last code, the last code is larger than the second last code, and the current code is smaller than the last code. 
         [0033]    With this configuration, an appliance feature can be extracted depending on the degree of increase/decrease of the flow rate, that is, the increase/decrease of the code, and the variations thereof can be absorbed, whereby stable appliance feature extraction can be accomplished. 
         [0034]    A fourth invention has a configuration wherein the last code and the second last code stored in the appliance feature code string are deleted and the current code is overwritten on the second last code stored in the appliance feature code string to compress the appliance feature code string in the case that the difference between the last code and the second last code is equal to or less than a predetermined value and the second last code is equal to the current code when the change of the codes obtained by the difference value conversion unit has an M-shaped characteristic, that is, the third last code is larger than the fourth last code, the second last code is smaller than the third last code, the last code is larger than the second last code, and the current code is smaller than the last code, or in the case that the difference between the last code and the second last code is equal to or less than the predetermined value and the second last code is equal to the current code when the change of the codes obtained by the difference value conversion unit has a W-shaped characteristic, that is, the third last code is smaller than the fourth last code, the second last code is larger than the third last code, the last code is smaller than the second last code, and the current code is larger than the last code. 
         [0035]    With this configuration, an appliance feature can be extracted depending on the degree of increase/decrease of the flow rate, that is, the increase/decrease of the code, and the variations thereof can be absorbed, whereby stable appliance feature extraction can be accomplished. 
         [0036]    A fifth invention is characterized in that the appliance feature extraction unit according to the first invention, in particular, is configured so as to delete the final code from the appliance feature code string in the case that the absolute value of the final code in the appliance feature code string is equal to or more than a predetermined value. 
         [0037]    With this configuration, the code that appears when the artificial switching of the amount of combustion is performed can be deleted from the appliance feature code string, whereby stable appliance feature extraction can be accomplished. 
         [0038]    A sixth invention provides a program for causing a computer to function as the whole or part of the flow rate measuring device according to any one of the first to fifth inventions. Furthermore, due to use of the program, at least part of the program of the present invention can be accomplished using a general-purpose computer or a server. Moreover, the program can be distributed and installed easily by recording the program on recording media or by delivering the program via a communication network. 
         [0039]    Since the object of the present invention can be attained by making the main sections of the first to fifth inventions to conform to the embodiments thereof, the details of the embodiments corresponding to respective claims will be described below referring to the drawings, and the best modes for implementing the present invention will be described. However, the present invention is not limited by the embodiments. Still further, components having the same configuration and the same working effect are designated by the same code and duplicate descriptions are not performed. 
       Embodiment 1 
       [0040]      FIG. 1  is a block diagram of a flow rate measuring device according to Embodiment 1 of the present invention. 
         [0041]    In  FIG. 1 , a gas meter  100  is equipped with a flow passage  102 , an ultrasonic flowmeter  104  serving as a flow rate measurement unit, a measured flow rate information storage unit  106 , a calculation unit  108 , a flow rate classification table storage unit  110 , a difference value conversion unit  112 , an appliance feature extraction unit  214 , an appliance identification unit  116 , and an appliance inherent feature code string information storage unit  218 . Furthermore, the gas meter  100  includes a shut-off unit  122  disposed in the flow passage  102  to shut off gas in an emergency, for example. 
         [0042]    The ultrasonic flowmeter  104  emits ultrasonic waves at constant time intervals to gas serving as fluid flowing in the flow passage  102  and measures the flow rate of the gas, and a general-purpose type can be used. The measured flow rate information storage unit  106  stores target data in which the measured flow rate values measured by the ultrasonic flowmeter  104  and the measurement times at which the measured flow rate values were measured are described while being associated with each other. 
         [0043]    The calculation unit  108  calculates the difference values of the flow rate of the gas measured by the ultrasonic flowmeter  104  at constant time intervals corresponding to the above-mentioned ultrasonic wave emitting intervals. For example, in  FIG. 3  described later, in the case that the flow rate (absolute flow rate) at a predetermined timing is 90 L/h (litters per hour) and the flow rate at the next timing is 145 L/h, the difference value at this time is calculated as 145−90=55 (L/h). The flow rate classification table storage unit  110  stores a flow rate classification table  110   a  shown in  FIG. 2  in which the classifications of a plurality of difference values, corresponding to the magnitudes of the difference values, are associated with codes representing the respective classifications.  FIG. 2  is a view showing an example of a flow rate classification table according to Embodiment 1. The flow rate classification table  110   a  plays a role of a conversion table in which the absolute values of the measured difference values are classified into predetermined classifications and converted into predetermined codes representing the classifications. The number of the classifications of the flow rate classification table  110   a  is not limited particularly;  FIG. 2  shows 16 code classifications as an example. Although a region in which the flow rate is judged zero is given, since the measured flow rate has some variations in an actual instrument, the flow rate scarcely becomes complete zero. Hence, a case in which the flow rate becomes zero includes a case in which the flow rate is nearly zero or substantially zero. 
         [0044]    Furthermore, with respect to the ranges of the respective classifications, segmentation is done while the classifications have different flow rate intervals. Fine segmentation is done for smaller flow rate difference values; for example, the interval is 10 L/h in code 1 to code 5, 25 L/h in code 6 to code B, 50 L/h in code C to code D, and 100 L/h in code E. With this configuration, since there are numerous kinds of appliances in the regions having small difference values, the accuracy of identification can be raised by making the intervals small. 
         [0045]    Since the letters A to F of the codes are hexadecimal representation of numbers 10 to 15, the codes can be used as numbers and compared in large-small relation. 
         [0046]    The difference value conversion unit  112  converts the difference values calculated by the calculation unit  108  into the codes representing the classifications in which the difference values at constant time intervals of the ultrasonic wave emission on the basis of the flow rate classification table  110   a.    
         [0047]    The appliance feature extraction unit  214  generates an extracted code string indicating the feature of an appliance from a measured code string serving as a string of codes obtained by actual measurement on the basis of a set of codes obtained at constant time intervals by the difference value conversion unit  112 . This measured code string is a pseudo-representation of the flow rate change of the fluid. The appliance feature extraction unit  214  records the extracted code string representing the feature of the appliance in a memory (not shown) as necessary. 
         [0048]    The appliance identification unit  116  identifies a gas appliance that uses gas as fluid on the basis of the extracted code string extracted by the appliance feature extraction unit  214 . At this time, the appliance identification unit  116  compares the extracted code string with an appliance inherent feature code string indicating a feature code string inherent in each gas appliance and stored beforehand in the appliance inherent feature code string information storage unit  218  for each gas appliance and then identifies the gas appliance that uses the gas according to the analogous relationship therebetween, for example. 
         [0049]    An appliance specific flow rate calculation unit  120  can also calculate the flow rate of each gas appliance identifies by the appliance identification unit  116 . In addition, the gas meter  100  is connected to a gas pipe line  19  on the upstream side and connected to various gas appliances  13 ,  14  and  15 , such as a gas table, a fan heater and a floor heating appliance, on the downstream side. 
         [0050]    In the flow rate measuring device configured as described above, its operation for appliance feature extraction processing will be described below. 
         [0051]    First, a flow rate (absolute flow rate) Q(n) measured at constant time intervals (for example, 0.5 seconds) by the ultrasonic flowmeter  104  and a flow rate Q(n−1) measured at the last time are once stored in the measured flow rate information storage unit  106 . Then, a difference value ΔQ(n)=Q(n)−Q(n−1), that is, the difference between the flow rate Q(n) and the flow rate Q(n−1) measured at the last time, is calculated by the calculation unit  108 . The constant time may be herein one or two seconds. 
         [0052]    The difference value conversion unit  112  converts the absolute values of the difference values ΔQ(n) calculated by the calculation unit  108  into classification codes representing classification in which the difference values at constant time intervals are classified referring to the flow rate classification table  110   a  of  FIG. 2 .  FIG. 3  shows an example of the conversion performed using this kind of flow rate classification table.  FIG. 3(   a ) is a view showing a concept in which the flow rate difference values at the time when a gas appliance A is used are classified according to the flow rate classification table in Embodiment 1.  FIG. 3(   b ) is a graph showing a flow rate characteristic at the time when the gas appliance A is used.  FIG. 3(   c ) is a graph showing classified codes at the time when the gas appliance A is used.  FIG. 3(   d ) is a graph showing a code string in which the feature at the time when the gas appliance A is used is extracted. When the gas appliance A (for example, a fan heater) corresponding to any one of the gas appliances  13 ,  14  and  15  of  FIG. 1  is started and a gas flow rate is generated, the flow rate to be measured changes from the flow rate Q(n)=0 to the flow rate Q(n)≠0 as shown in the graph of  FIG. 3(   b ); the flow rate changes depending on the used amount of gas. Concurrently with the flow rate measurement using the ultrasonic flowmeter  104 , the calculation unit  108  calculates the difference values and the difference value conversion unit  112  performs conversion into the classification codes. 
         [0053]    Among the codes obtained as the result of the conversion, that is, the codes converted by the difference value conversion unit  112 , in the case that the last code is larger than the second last code and the last code is larger than the current code or in the case that the last code is smaller than the second last code and the last code is smaller than the current code, the appliance feature extraction unit  214  performs processing for storing the current code in the appliance feature code string serving as a memory; and in the other cases, the extraction unit performs processing for overwriting the current code on the last code stored in the appliance feature code string. With this processing, a code string [07151] extracted from a code string [0761151111111111] at constant time intervals shown in  FIG. 3  is stored in the appliance feature code string. In other words, by virtue of this processing, it is possible to extract the peak values of the codes in the range from the start of the gas appliance A to the change point I, in the range from the change point I to the change point II and in the range from the change point II to the change point III shown in  FIG. 3(   b ). This extracted code string is shown in the graph of  FIG. 3(   d ), and the fact that the feature of the appliance is extracted sufficiently is understood more easily from this graph than from the graph of  FIG. 3(   c ) showing the code string before the extraction, although the amount of the information is compressed. 
         [0054]    Similarly,  FIG. 4  is a view showing the concept of feature extraction at the time when a gas appliance B is used.  FIG. 4(   a ) is a view showing a concept in which the flow rate difference values at the time when the gas appliance B is used are classified according to the flow rate classification table in Embodiment 1.  FIG. 4(   b ) is a graph showing a flow rate characteristic at the time when the gas appliance B is used.  FIG. 4(   c ) is a graph showing classified codes at the time when the gas appliance B is used.  FIG. 4(   d ) is a graph showing a code string in which the feature at the time when the gas appliance B is used is extracted. In the case of the gas appliance B (for example, a push-lever type gas table), a code string [061] extracted from a code string [0361111111111111] at constant time intervals, converted by the difference value conversion unit  112 , is stored in the appliance feature code string. 
         [0055]    When the extracted appliance feature code string in the case of the above-mentioned gas appliance A is herein compared with that in the case of the gas appliance B, two peaks appear in the case of the gas appliance A, that is, in the graph of  FIG. 3(   d ), but only one peak appears in the case of the gas appliance B, that is, in the graph of  FIG. 4(   d ). This is due to the fact that slow ignition operation is performed in the appliance A, and this makes it possible to clearly identify that the appliance is the appliance A different from the appliance B. 
         [0056]    The rising characteristic of each of gas appliances described above, that is, the feature code inherent in each gas appliance, is stored beforehand in the appliance inherent feature code string information storage unit  218 ; if the obtained appliance feature code string is [07151], the gas appliance being used can be identified as the gas appliance A; and if the obtained appliance feature code string is [061], the gas appliance being used can be identified as the gas appliance B. 
         [0057]    Next,  FIGS. 5 and 6  are views showing the concepts of feature extraction at the time when a gas appliance C is used.  FIG. 5(   a ) is a view showing a concept in which the flow rate difference values at the time when the gas appliance C is used are classified according to the flow rate classification table in Embodiment 1.  FIG. 5(   b ) is a graph showing a flow rate characteristic at the time when the gas appliance C is used.  FIG. 5(   c ) is a graph showing classified codes at the time when the gas appliance C is used.  FIG. 5(   d ) is a graph showing a code string in which the feature at the time when the gas appliance C is used is extracted.  FIG. 6(   a ) is a view showing a concept in which the flow rate difference values at the time when the gas appliance C is used are classified according to the flow rate classification table in Embodiment 1.  FIG. 6(   b ) is a graph showing a flow rate characteristic at the time when the gas appliance C is used.  FIG. 6(   c ) is a graph showing classified codes at the time when the gas appliance C is used.  FIG. 6(   d ) is a graph showing a code string in which the feature at the time when the gas appliance C is used is extracted. In the gas appliance C, an appliance equipped with a pilot burner (for example, a pilot-burner push-turn type gas table), the pilot burner is extinguished by releasing the hand after ignition, whereby the flow rate of gas decreases at this time. However, since the time until the hand is released varies, the code string at constant time intervals, converted by the difference value conversion unit  112 , becomes [0861131111111111] in the example of  FIG. 5  and becomes [0861111311111111] in the example of  FIG. 6 , whereby the gas appliances cannot be identified as the same gas appliance. However, by performing the feature extraction processing in Embodiment 1, the code string extracted from the code string at regular time intervals, converted by the difference value conversion unit  112 , becomes [08131] in the case of  FIG. 5 , and the extracted code string becomes [08131] in the case of  FIG. 6 ; the same code string is obtained. As a result, the gas appliances can be identified as the same gas appliance. 
         [0058]    Moreover, although two peaks appear in the graph of  FIG. 5(   d ) for the gas appliance C as in the case of the graph of  FIG. 3(   d ) for the above-mentioned gas appliance A, identification can be performed because there is a difference in the height of the second peak (the magnitude of the code). Not only the extracted appliance feature code string but also a stable flow rate value (for example, 204 L/h in  FIG. 3 , 143 L/h in  FIG. 5)  may be additionally used as an identification judgment condition. 
         [0059]    As described above, in Embodiment 1, the feature of an appliance from a code string at constant time intervals converted by the difference value conversion unit  112  is extracted by the appliance feature extraction unit  214 ; hence, accurate appliance identification can be performed, and the code string can be compressed by the feature extraction, whereby the size of the memory can be made small. 
       Embodiment 2 
       [0060]      FIG. 7  is a view showing the concept of feature extraction in Embodiment 2 of the present invention.  FIG. 7(   a ) is a view showing a concept in which the flow rate difference values at the time when the gas appliance A is used are classified according to the flow rate classification table in Embodiment 2.  FIG. 7(   b ) is a graph showing a code string obtained by extracting the feature at the time when the gas appliance A is used.  FIG. 7(   c ) is a view showing a concept in which the flow rate difference values at the time when the gas appliance C is used are classified according to the flow rate classification table in Embodiment 1.  FIG. 7(   d ) is a graph showing a code string in which the feature at the time when the gas appliance C is used is extracted. As described in Embodiment 1, appliance identification can be performed according to the appliance feature code string extracted by the appliance feature extraction unit  214 ; however, when the same gas appliance is used repeatedly and in the case that the difference flow rate values become close to the threshold value of the code classification because of variations in the flow rate, for example, there is a possibility that the appliance feature code string may become different. Hence, for example, when the appliance inherent feature code string stored beforehand in the appliance inherent feature code string information storage unit  218  is compared with the extracted appliance feature code string, the respective codes of the appliance feature code string are allowed to vary up to ±1, and it is assumed that the appliances are the same, whereby erroneous identification is prevented. 
         [0061]    When the graph of  FIG. 3(   d ) indicating the appliance feature code string of the above-mentioned gas appliance A is herein compared with the graph of  FIG. 5(   d ) indicating the appliance feature code string of the gas appliance C and in the case that the respective codes of the appliance feature code string are allowed to vary up to ±1 and in the case that the code of the second peak is 4, it is understood that there is a possibility of erroneous identification. However, this erroneous identification can be prevented by additionally using the above-mentioned stable flow rate for the identification. 
         [0062]    Hence, in addition to the feature extraction processing described in Embodiment 1, the appliance feature extraction unit  214  performs processing for adding a minus sign to codes in the case that the difference values calculated by the calculation unit  108  are minus and the codes obtained by the difference value conversion unit  112  are other than a predetermined code and for not overwriting the current code on the last code stored in the appliance feature code string in the case that the last code is plus and the current code is minus. At this time, the predetermined code assumed to be [1]. 
         [0063]    By virtue of this processing, in the case of the gas appliance A, as shown in  FIG. 7(   a ), the code string [0761151111111111] at constant time intervals converted by the difference value conversion unit  112  becomes [0761151111111111], and a code string [07151] extracted from this is stored in the appliance feature code string. 
         [0064]    Similarly, in the case of the gas appliance C, as shown in  FIG. 7(   c ), the code string [0861111311111111] at constant time intervals converted by the difference value conversion unit  112  becomes [0861111-311111111], and a code string [081-31] extracted from this is stored in the appliance feature code string. Hence, the gas appliance A and the gas appliance C can be distinguishably identified definitely. 
         [0065]    As described above, in Embodiment 2, the feature of an appliance including flow rate increase/decrease information from a code string at constant time intervals converted by the difference value conversion unit  112  is extracted by the appliance feature extraction unit  214 ; hence, accurate appliance identification can be performed, and the code string can be compressed by the feature extraction, whereby the size of the memory can be made small. 
       Embodiment 3 
       [0066]      FIG. 8  is a view showing the concept of feature extraction in Embodiment 3 of the present invention.  FIG. 8(   a ) is a view showing a concept in which the flow rate difference values at the time when a gas appliance D is used are classified according to the flow rate classification table in Embodiment 3.  FIG. 8(   b ) is a graph showing a flow rate characteristic at the time when the gas appliance D is used.  FIG. 8(   c ) is a graph showing classified codes at the time when the gas appliance D is used.  FIG. 8(   d ) is a graph showing a code string in which the feature at the time when the gas appliance D is used is extracted. In the case of the gas appliance D having the flow rate rising characteristic shown in  FIG. 8(   b ), the code string at constant time intervals converted by the difference value conversion unit  112  becomes [0768113-4-2-6111111] as shown in  FIG. 8(   a ). This is shown in the graph of  FIG. 8(   c ). 
         [0067]    When the change from the rising of the flow rate to the change point I shown in  FIG. 8(   b ) is observed, it is found that the change has a rightward rising inclination as a whole although there are differences in the inclination of the flow rate characteristic. Similarly, when the change from the change point III to the change point IV shown in  FIG. 8(   b ) is observed, it is found that the change has a rightward lowering inclination as a whole although there are differences in the inclination of the flow rate characteristic. 
         [0068]    However, the code string in the zone corresponding to the range from the rising of the flow rate to the change point I shown in  FIG. 8(   b ) is [0768] and has an N-shaped characteristic as shown in  FIG. 8(   c ). Furthermore, the code string in the zone corresponding to the range from the change point III to the change point IV shown in  FIG. 8(   b ) is [3-4-2-6] and has an inverted N-shaped characteristic as shown in  FIG. 8(   c ). 
         [0069]    In other words, although the flow rate characteristic is generally rightward rising or rightward lowering, the code string has the N-shaped characteristic or the inverted N-shaped characteristic; hence, it cannot be said definitely that there is coincidence in the feature. 
         [0070]    Hence, in addition to the feature extraction processing described in Embodiment 1 or Embodiment 2, the appliance feature extraction unit  214  performs processing for deleting the last code and the second last code if the difference between the last code and the second last code is equal to or less than a predetermined value, in the case that the change of the codes obtained by the difference value conversion unit  112  has the N-shaped characteristic, that is, the second last code is larger than the third last code, the last code is smaller than the second last code, and the current code is larger than the last code, or in the case that the change of the codes obtained by the difference value conversion unit  112  has the inverted N-shaped characteristic, that is, the second last code is smaller than the third last code, the last code is larger than the second last code, and the current code is smaller than the last code. In the case that the change of the codes has the inverted N-shaped characteristic and the last code and the second last code are deleted, the difference between the last code and the second last code is assumed to be 2 or less, for example. 
         [0071]    By virtue of this processing, the code string [0812-61] extracted from the code string [0768113-4-2-611111] at constant time intervals converted by the difference value conversion unit  112  is stored in the appliance feature code string. Hence, the N-shaped characteristic or the inverted N-shaped characteristic of the code string is absorbed, and the rightward rising or rightward lowering feature of the original flow rate characteristic can be extracted definitely. 
         [0072]    As described above, in Embodiment 3, the feature of an appliance, in which the inclination of the flow rate characteristic is reflected, from a code string at constant time intervals converted by the difference value conversion unit  112  is extracted by the appliance feature extraction unit  214 ; hence, accurate appliance identification can be performed, and the code string can be compressed by the feature extraction, whereby the size of the memory can be made small. 
       Embodiment 4 
       [0073]      FIG. 9  is a view showing the concept of feature extraction in Embodiment 4 of the present invention.  FIG. 9(   a ) is a view showing a concept in which the flow rate difference values at the time when a gas appliance E is used are classified according to the flow rate classification table in Embodiment 4.  FIG. 9(   b ) is a graph showing a flow rate characteristic at the time when the gas appliance E is used.  FIG. 9(   c ) is a graph showing classified codes at the time when the gas appliance E is used.  FIG. 9(   d ) is a graph showing a code string in which the feature at the time when the gas appliance E is used is extracted. In the case of the gas appliance E having the flow rate rising characteristic shown in  FIG. 9(   b ), the code string at constant time intervals converted by the difference value conversion unit  112  becomes [0545411111111111] as shown in  FIG. 9(   a ). This is shown in the graph of  FIG. 9(   c ). At this time, as shown in the example of  FIG. 9(   a ), when the flow rate difference value changes in the vicinity of the threshold value as in the case that the flow rate difference value changes repeatedly between 41 L/h and 40 L/h, the difference between the 41 L/h and 40 L/h is only 1 L/h; however, the code changes like [5454], although the difference is small. 
         [0074]    The code string in the flow rate rising zone is [05454] and has an M-shaped characteristic as shown in  FIG. 9(   c ). In other words, although the flow rate characteristic is generally rightward rising, the code string has the M-shaped characteristic; hence, it cannot be said definitely that there is coincidence in the feature. Hence, in addition to the feature extraction processing described in Embodiment 1, Embodiment 2 or Embodiment 3, the appliance feature extraction unit  214  performs processing for deleting the last code and the second last code and for overwriting the current code on the second last code in the case that the difference between the last code and the second last code is equal to or less than a predetermined value and the second last code is equal to the current code when the change of the codes obtained by the difference value conversion unit  112  has the M-shaped characteristic, that is, the third last code is larger than the fourth last code, the second last code is smaller than the third last code, the last code is larger than the second last code, and the current code is smaller than the last code. In the case that the change of the codes has the M-shaped characteristic and the last code and the second last code are deleted, the difference between the last code and the second last code is assumed to be 1 or less. 
         [0075]    By virtue of this processing, the rising code string [05454] of the codes converted by the difference value conversion unit  112  becomes [054], and [054111111111111] obtained by adding the subsequent codes is subjected to the processing described in Embodiment 1; as a result, the code string becomes [051] and stored in the appliance feature code string. 
         [0076]    Next,  FIG. 10  is also a view showing the concept of feature extraction in Embodiment 4 of the present invention, and the difference from  FIG. 9  will be described below.  FIG. 10(   a ) is a view showing a concept in which the flow rate difference values at the time when a gas appliance F is used are classified according to the flow rate classification table in Embodiment 4.  FIG. 10(   b ) is a graph showing a flow rate characteristic at the time when the gas appliance F is used.  FIG. 10(   c ) is a graph showing classified codes at the time when the gas appliance F is used.  FIG. 10(   d ) is a graph showing a code string in which the feature at the time when the gas appliance F is used is extracted. 
         [0077]    In the case of the gas appliance F having the flow rate rising characteristic shown in  FIG. 10(   b ), the code string at constant time intervals converted by the difference value conversion unit  112  becomes [0646561111111111] as shown in  FIG. 10(   a ). This is shown in the graph of  FIG. 10(   c ). At this time, although the flow rate rising code string [06465] has the M-shaped characteristic as shown in the example shown in  FIG. 9 , the difference between the last code and the second last code is 2, thereby not satisfying the code compression condition for the M-shaped characteristic, whereby the codes remain without being compressed. However, a code string [64656] obtained by deleting the head code and by adding the next code has a W-shaped characteristic as shown in  FIG. 10(   c ). 
         [0078]    Hence, in addition to the feature extraction processing described in Embodiment 1, Embodiment 2 or Embodiment 3, the appliance feature extraction unit  214  performs processing for deleting the last code and the second last code stored in the appliance feature code string and for overwriting the current code on the second last code stored in the appliance feature code string in the case that the difference between the last code and the second last code is equal to or less than a predetermined value and the second last code is equal to the current code when the change of the codes obtained by the difference value conversion unit  112  has the W-shaped characteristic, that is, the third last code is smaller than the fourth last code, the second last code is larger than the third last code, the last code is smaller than the second last code, and the current code is larger than the last code. In the case that the change of the codes has the W-shaped characteristic and the last code and the second last code are deleted, the difference between the last code and the second last code is assumed to be 1 or less. 
         [0079]    By virtue of this processing, the rising code string [64656] of the codes converted by the difference value conversion unit  112  becomes [646]. Furthermore, of [06461111111111] obtained by adding the head and subsequent codes corresponds to the inverted N-shaped characteristic described in Embodiment 3; hence, this code string is subjected to the processing described in Embodiment 1, whereby the code string becomes [061] and stored in the appliance feature code string. 
         [0080]    By virtue of the M-shaped and W-shaped characteristic processing, the M-shaped characteristic or the W-shaped characteristic of the code string is absorbed, and the feature of the original flow rate characteristic can be extracted definitely. 
         [0081]    As described above, in Embodiment 4, the feature of an appliance, in which the inclination of the flow rate characteristic is reflected, from a code string at constant time intervals converted by the difference value conversion unit  112  is extracted by the appliance feature extraction unit  214 ; hence, accurate appliance identification can be performed, and the code string can be compressed by the feature extraction, whereby the size of the memory can be made small. 
       Embodiment 5 
       [0082]      FIG. 11  is a view showing the concept of feature extraction in Embodiment 5 of the present invention.  FIG. 11(   a ) is a view showing a concept in which the flow rate difference values at the time when the gas appliance C is used are classified according to the flow rate classification table in Embodiment 5.  FIG. 11(   b ) is a graph showing a flow rate characteristic at the time when the gas appliance C is used.  FIG. 11(   c ) is a graph showing classified codes at the time when the gas appliance C is used.  FIG. 11(   d ) is a graph showing a code string in which the feature at the time when the gas appliance C is used is extracted. Although a case in which the gas appliance C explained in Embodiment 1 is ignited and then its heating power is switched is described, it is assumed that the change of the rising flow rate until the heating power is changed is the same as that shown in  FIG. 6 .  FIG. 11(   b ) shows the flow rate rising characteristic including the change of the heating power after the ignition, and the code string at constant time intervals converted by the difference value conversion unit  112  becomes [0861111311111133] as shown in  FIG. 11(   a ). This is shown in the graph of  FIG. 11(   c ). 
         [0083]    As described in Embodiment 1, when the code string [08611113111111] until the heating power is changed is subjected to the feature extraction processing, the code string becomes [08131]; however, if heating power change codes are included, the code string becomes [0813133] and finally becomes [081313] when further subjected to the processing of Embodiment 1. Hence, since the code string is different from the extracted code string [08131] shown in  FIG. 6  of Embodiment 1, the gas appliances cannot be identified as the same gas appliance. 
         [0084]    Therefore, the appliance feature extraction unit  214  performs processing for deleting the final code from the appliance feature code string in the case that the absolute value of the final code in the appliance feature code string is equal to or more than a predetermined value. It is herein assumed that the predetermined value according to which the final code is deleted is 2 or more. 
         [0085]    By virtue of this processing, the above-mentioned code string [081313] becomes [08131]; hence, the same code string as that in the case in which the heating power is not changed, shown in  FIG. 6 , is obtained, whereby the gas appliances can be identified as the same gas appliance. 
         [0086]    As described above, in Embodiment 5, the code that appears when the artificial switching of the amount of combustion is performed can be deleted from the appliance feature code string in Embodiment 5, and accurate appliance identification can be performed; furthermore, the code string can be compressed by the feature extraction, whereby the size of the memory can be made small. 
         [0087]    To execute the above-mentioned flow rate measurement method, a program for executing the respective steps of the flow rate measurement method is stored in the appliance identification unit  116  or a computer (arithmetic unit), not shown, of the gas meter  100 ; however, hardware, instead of the program, can also be used for the execution. 
         [0088]    In the respective embodiments described above, the case in which the ultrasonic flowmeter is used as flow rate measurement unit has been described; however, it is obvious that a similar effect is also obtained even in the case that another type of instantaneous flow rate measuring device that uses a sampling signal is used. Although the explanation of the processing that is performed after the appliance identification is omitted, it is obvious in the gas meter that an appliance specific charge based on the measurement of the integrated flow rate for each registered appliance or each classified group can be set, and that an appliance specific security function for safety control (security function) for each registered appliance or each classified group can be set. Moreover, if a transmitting and receiving unit, such as a wireless device, can be mounted on a gas meter and a gas appliance, it is obvious that the accuracy of appliance identification is improved. 
         [0089]    In the respective embodiments described above, the appliance feature extraction using codes obtained by converting flow rate difference values at constant time intervals has been described; however, more accurate feature extraction can be performed using the flow rate difference values. 
         [0090]    In the respective embodiments described above, appliance identification is performed by comparing the appliance inherent feature code string stored in the appliance inherent code string information storage unit  118  with the appliance feature code string indicating the feature of an appliance on the basis of codes obtained at constant time intervals by the difference value conversion unit; however, the appliance inherent feature code string may be corrected in consideration of variations obtained when an actual flow rate measurement is repeated. Furthermore, it may be possible, for example, that an appliance registration mode is provided, an appliance is operated repeatedly on site, the feature of the appliance is extracted and averaged, for example, and the feature is registered as an appliance inherent feature code string. Moreover, without presetting the appliance inherent feature code string, the appliance inherent feature code string may be registered automatically by learning. 
         [0091]    The respective embodiments of the present invention have been described above; however, the present invention is not limited to the matters described in the above-mentioned embodiments, but the modifications and applications thereof implemented by those skilled in the art on the basis of the descriptions of the specification and known technologies are supposed to be planned in the present invention and included in the scope of protection. 
         [0092]    The present application is based on Japanese Patent Application (Application No. 2009-048791) filed on Mar. 3, 2009 and Japanese Patent Application (Application No. 2009-212592) filed on Sep. 15, 2009, and the contents thereof are herein incorporated by reference. 
       INDUSTRIAL APPLICABILITY 
       [0093]    Since the flow rate measuring device according to the present invention can extract the features of appliances as described above, the instrument is applicable for the identification and the grouping of the appliances used and connected on the downstream side of the flow rate measuring device, as in the case of an industrial flowmeter and a water meter. 
       REFERENCE SIGN LIST 
       [0000]    
       
         
           
               13 ,  14 ,  15  gas appliance 
               19  gas pipe line 
               100  gas meter (flow rate measuring device) 
               102  flow passage 
               104  ultrasonic flowmeter (flow rate measurement unit) 
               106  measured flow rate information storage unit 
               108  calculation unit 
               110  flow rate classification table storage unit 
               112  difference value conversion unit 
               116  appliance identification unit 
               120  appliance specific flow rate calculation unit 
               122  shut-off unit 
               214  appliance feature extraction unit 
               218  appliance inherent feature code string information storage unit