Abstract:
A game controller including multiple sensors for detecting a pressure load of a user for use as an input device of a game apparatus. The game controller includes a load platform adapted to receive the pressure load of the user; a plurality of load sensors arranged in the load platform for detecting the pressure load of the user, each load sensor generating an independent detected load signal; and a connector to operationally connect the plurality of load sensors to the game apparatus for transmitting a transmission signal to the game apparatus to facilitate gameplay. The transmission signal includes the independent detected load signal of at least one load sensor such that the transmission signal includes at least one independent detected load signal corresponding to at least one load sensor of the plurality of load sensors.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 12/010,033, filed Jan. 18, 2003, now pending, which claims priority to the disclosure of Japanese Patent Application No. 2007-283445, filed Oct. 31, 2007. The entire content of both of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a calibration of a weight measuring apparatus, and more particularly to a weight applying unit for performing a calibration on a weight measuring apparatus comprising a plurality of load sensors and a weight applying method of performing the same. 
         [0004]    2. Description of the Background Art 
         [0005]    In a weight measuring apparatus, using a load sensor, which is typified by a scale or the like, a calibration is performed on a load sensor-integrated weight measuring apparatus as a finished product, in order to improve an accuracy of measurement results. As a calibration method used for a weight measuring apparatus using a single load sensor, for example, a specific load of a weight is placed on a load platform at a center position thereof, and a calibration is performed based on a detected output of the load sensor. Also, there may be another weight measuring apparatus in which a single load platform is supported by a plurality of load sensors, and detected outputs of the plurality of respective load sensors are added to each other so as to obtain a weight value. Similarly to the weight measuring apparatus using the single load sensor, as a calibration method used for said another weight measuring apparatus comprising the plurality of load sensors, a specific load of a weight is placed on the load platform at a center position thereof, and a calibration is performed based on a total value of the detected outputs of the respective load sensors. Furthermore, as another calibration method, specific loads of weights are respectively placed on a load platform at predetermined positions such as four corners of the load platform, thereby performing a calibration based on detected outputs of the respective load sensors (Japanese Laid-Open Patent Publication No. 3-25325, for example). 
         [0006]    In recent years, in the field of home fitness apparatuses or video games, when using the weight measuring apparatus comprising the plurality of load sensors, for example, it is requested that the weight measuring apparatus not only output the weight of a to-be-measured object placed on a load platform, but also recognize a balance state of the to-be-measured object such as the postural balance of a person on the load platform. In order to recognize the balance state of the to-be-measured object (e.g., a state where a human stands on his or her right foot and a greater amount of load is applied to a right side of the load platform), loads applied to the plurality of load sensors must be individually obtained. Further, in order to improve an accuracy of measurement results detected by the respective load sensors, a calibration must be performed on each of the load sensors, instead of performing the calibration based on the total value of the detected outputs of the respective load sensors. 
         [0007]    In such a weight measuring apparatus integrated with the plurality of load sensors, as a method of performing a calibration on each of the load sensors, there may be a method in which the specific loads of the weights are placed on a load platform in respective four corners thereof, thereby performing the calibration on each of the load sensors based on an output of each of the load sensors (not based on the total value of the outputs of the respective load sensors), as disclosed in Japanese Laid-Open Patent Publication No. 3-25325. 
         [0008]    However, in the aforementioned calibration method in which the weights are respectively placed in the four corners of the load platform, the weights are placed on the load platform, and therefore a load of each of the weights, which naturally should be applied in a perpendicular direction, is to be dispersed in other directions. For example, in the case of a weight measuring apparatus in which a load platform is supported by two load sensors  91  and  92  as shown in  FIG. 17 , it is assumed that a weight of 50 kg is placed on the load platform at a right side thereof. In this case, a value of 40 kg is detected in the load sensor  92  located under the weight, while a value of 10 kg is detected in the other load sensor  31 , for example. That is, a load of 50 kg is distributed between the two load sensors. Furthermore, the value of 40 kg or 10 kg is used as an example in  FIG. 17  in order to facilitate the description. In practice, however, it is difficult to accurately recognize how and in which direction the load of 50 kg is dispersed. Therefore, in such a calibration method, when a calibration is performed on each of the load sensors, it is extremely difficult to perform a proper calibration. 
       SUMMARY OF THE INVENTION 
       [0009]    Therefore, an object of the present invention is to provide a weight applying unit for calibration and a weight applying method for calibration, both of which are capable of performing, in a weight measuring apparatus comprising a plurality of load sensors, a proper calibration on each of the load sensors. 
         [0010]    The present invention has the following features to attain the object mentioned above. Note that reference numerals and figure numbers are shown in parentheses below for assisting a reader in finding corresponding components in the figures to facilitate the understanding of the present invention, but they are in no way intended to restrict the scope of the invention. 
         [0011]    A first aspect is a weight applying unit for calibration used for performing a calibration on a weight measuring apparatus in which a load platform is supported by a plurality of load sensor sections and a weight of a measurement target object placed on the load platform is measured based on a load value detected by each of the plurality of load sensor sections, the weight applying unit for calibration comprising: a support section ( 51 ) and a weight applying section ( 53 ). The support section supports the weight measuring apparatus. The weight applying section applies predetermined loads to the plurality of load sensor sections, respectively. 
         [0012]    According to the first aspect, a load can be individually applied to each of the plurality of load sensor sections. 
         [0013]    In a second aspect based on the first aspect, the support section supports a load platform surface of the weight measuring apparatus such that the load platform surface is in a horizontal position. The weight applying section applies the predetermined loads to the plurality of load sensor sections, respectively, in a direction perpendicular to the load platform surface. 
         [0014]    According to the second aspect, the load is applied in the direction perpendicular to the load platform surface. Thus, the load can be prevented from being dispersed, thereby making it possible to easily and assuredly apply the load. 
         [0015]    In a third aspect based on the second aspect, the support section supports the weight measuring apparatus such that the load platform surface of the weight measuring apparatus faces a gravitational direction. The weight applying section applies the predetermined loads in a downward direction. 
         [0016]    According to the third aspect, the load is applied in the gravitational direction. Thus, the load is not to be dispersed, thereby making it possible to more assuredly apply the load. 
         [0017]    In a fourth aspect based on the first aspect, values of the predetermined loads applied by the weight applying section to the plurality of load sensor sections, respectively, are the same as one another. 
         [0018]    According to the fourth aspect, the loads having the same value as one another are applied to the plurality of load sensor sections, respectively. Thus, it becomes possible to perform a calibration on each of the load sensor sections under the same condition. 
         [0019]    In a fifth aspect based on the first aspect, the weight applying unit for calibration further comprises a deflection generating portion ( 61 ) for generating deflection by applying a predetermined pressure to a load platform surface of the weight measuring apparatus. 
         [0020]    According to the fifth aspect, the load can be applied assuming a condition where the weight measuring apparatus is actually used (i.e., where the deflection is generated). Thus, it becomes possible to perform a more proper calibration. 
         [0021]    In a sixth aspect based on the fifth aspect, the support section has a placement table for placing the weight measuring apparatus thereon. The weight measuring apparatus is placed on the placement table such that the load platform surface of the weight measuring apparatus and a load surface of the placement table face horizontally toward each other. Further, the deflection generating portion is a elastic body disposed so as to be interposed between the load surface of the placement table and the load platform surface of the weight measuring apparatus. 
         [0022]    According to the sixth aspect, the condition where the weight measuring apparatus is actually used can be easily created. Furthermore, since the elastic body is used, even if a press is applied to an end of the deflection generating portion, the generated deflection of the weight measuring apparatus can be prevented from being hampered. Still furthermore, it becomes possible to prevent the load platform surface of the weight measuring apparatus from being damaged through calibration steps. 
         [0023]    In a seventh aspect base on the sixth aspect, the deflection generating portion is an elastic body having a shape simulating an area in which the measurement target object contacts the load platform. 
         [0024]    In an eighth aspect based on the sixth aspect, the deflection generating portion is an elastic body having a Shore hardness of Shore A70. 
         [0025]    According to the seventh and eighth aspects, the deflection more similar to that under actual usage conditions can be generated. 
         [0026]    In a ninth aspect based on the sixth aspect, the deflection generating portion is made of ester polyurethane. 
         [0027]    According to the ninth aspect, even if a pressure is applied to an end of the deflection generating portion, the generated deflection of the weight measuring apparatus can be prevented from being hampered. Furthermore, it becomes possible to prevent the load platform surface of the weight measuring apparatus from being damaged through the calibration steps. 
         [0028]    In a tenth aspect based on the second aspect, the weight applying unit for calibration further comprises a deflection generating portion ( 61 ) for generating deflection by applying a predetermined pressure to a load platform surface of the weight measuring apparatus. 
         [0029]    According to the tenth aspect, it becomes possible to obtain an effect similar to that of the fifth aspect. 
         [0030]    In an eleventh aspect based on the tenth aspect, the support section has a placement table for placing the weight measuring apparatus thereon. The weight measuring apparatus is placed on the placement table such that the load platform surface of the weight measuring apparatus and a load surface of the placement table face horizontally toward each other. Furthermore, the deflection generating portion is an elastic body disposed so as to be interposed between the load surface of the placement table and the load platform surface of the weight measuring apparatus. 
         [0031]    According to the eleventh aspect, it becomes possible to obtain an effect similar to that of the sixth aspect. 
         [0032]    In a twelfth aspect based on the eleventh aspect, the deflection generating portion is an elastic body having a shape simulating an area in which the measurement target object contacts the load platform. 
         [0033]    According to the twelfth aspect, it becomes possible to obtain an effect similar to that of the seventh aspect. 
         [0034]    In a thirteenth aspect based on the third aspect, the weight applying unit for calibration further comprises a deflection generating portion ( 61 ) for generating deflection by applying a predetermined pressure to the load platform surface of the weight measuring apparatus. 
         [0035]    According to the thirteenth aspect, it becomes possible to obtain an effect similar to that of the fifth aspect. 
         [0036]    In a fourteenth aspect based on the thirteenth aspect, the support section has a placement table for placing the weight measuring apparatus thereon. The weight measuring apparatus is placed on the placement table such that the load platform surface of the weight measuring apparatus and a load surface of the placement table face horizontally toward each other. Furthermore, the deflection generating portion is an elastic body disposed so as to be interposed between the load surface of the placement table and the load platform surface of the weight measuring apparatus. 
         [0037]    According to the fourteenth aspect, it becomes possible to obtain an effect similar to that of the sixth aspect. 
         [0038]    In a fifteenth aspect based on the fourteenth aspect, the deflection generating portion is an elastic body having a shape simulating an area in which the measurement target object contacts the load platform. 
         [0039]    According to the fifteenth aspect, it becomes possible to obtain an effect similar to that of the seventh aspect. 
         [0040]    In a sixteenth aspect based on the fourth aspect, the weight applying unit for calibration further comprises a deflection generating portion ( 61 ) for generating deflection by applying a predetermined pressure to a load platform surface of the weight measuring apparatus. 
         [0041]    According to the sixteenth aspect, it becomes possible to obtain an effect similar to that of the fifth aspect. 
         [0042]    In a seventeenth aspect based on the sixteenth aspect, the support section has a placement table for placing the weight measuring apparatus thereon. The weight measuring apparatus is placed on the placement table such that the load platform surface of the weight measuring apparatus and a load surface of the placement table face horizontally toward each other. Furthermore, the deflection generating portion is an elastic body disposed so as to be interposed between the load surface of the placement table and the load platform surface of the weight measuring apparatus. 
         [0043]    According to the seventeenth aspect, it becomes possible to obtain an effect similar to that of the sixth aspect. 
         [0044]    In an eighteenth aspect based on the seventeenth aspect, the deflection generating portion is an elastic body having a shape simulating an area in which the measurement target object contacts the load platform. 
         [0045]    According to the eighteenth aspect, it becomes possible to obtain an effect similar to that of the seventh aspect. 
         [0046]    In a nineteenth aspect based on the first aspect, the weight applying unit for calibration further comprises a detection value obtaining section and a setting section. The detection value obtaining section obtains a detection value outputted from each of the plurality of load sensor sections to which the predetermined loads are applied, respectively, by the weight applying section. The setting section sets the detection value obtained by the detection value obtaining section in the weight measuring apparatus so as to be associated with each of the load sensor sections which has outputted the detection value. 
         [0047]    In a twentieth aspect based on the nineteenth aspect, the weight applying section can calibrate the load value applied to each of the plurality of load sensor sections. The setting section sets, in the weight measuring apparatus, data detected based on a plurality of load values by applying loads having values different from each other. 
         [0048]    According to the nineteenth and twentieth aspects, it becomes possible to cause the weight measuring apparatus to store calibration results, thereby improving usability of the weight applying unit for calibration. 
         [0049]    A twenty-first aspect is a weight applying method for calibration used for performing a calibration on a weight measuring apparatus in which a load platform is supported by a plurality of load sensor sections, and a calculation process is performed on a load value detected by each of the plurality of load sensor sections so as to measure a weight of a measurement target object placed on the load platform, the weight applying method for calibration comprising: a supporting step (step  1 ); and a weight applying step (step  4 ,  5 ). The supporting step supports the weight measuring apparatus. The weight applying step respectively applies predetermined loads to the plurality of load sensor sections included in the weight measuring apparatus supported by the supporting step. 
         [0050]    According to the twenty-first aspect, it becomes possible to obtain an effect similar to that of the first aspect. 
         [0051]    According to the present invention, a load can be applied individually to each of the plurality of load sensor sections. Thus, it becomes possible to perform a more proper calibration on each of the load sensor sections. 
         [0052]    These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0053]      FIG. 1  is a diagram describing a principle of a weight applying/calibration method according to the present invention; 
           [0054]      FIG. 2  is another diagram describing the principle of the weight applying/calibration method according to the present invention; 
           [0055]      FIG. 3A  is a diagram illustrating an example of an external view of a weight measuring apparatus  10  according to embodiments of the present embodiment; 
           [0056]      FIG. 3B  is a diagram illustrating the example of the external view of the weight measuring apparatus  10  according to embodiments of the present embodiment; 
           [0057]      FIG. 3C  is a diagram illustrating the example of the external view of the weight measuring apparatus  10  according to embodiments of the present embodiment; 
           [0058]      FIG. 3D  is a diagram illustrating the example of the external view of the weight measuring apparatus  10  according to embodiments of the present embodiment; 
           [0059]      FIG. 3E  is a diagram illustrating the example of the external view of the weight measuring apparatus  10  according to embodiments of the present embodiment; 
           [0060]      FIG. 3F  is a diagram illustrating the example of the external view of the weight measuring apparatus  10  according to embodiments of the present embodiment; 
           [0061]      FIG. 3G  is a diagram illustrating the example of the external view of the weight measuring apparatus  10  according to embodiments of the present embodiment; 
           [0062]      FIG. 3H  is a diagram illustrating the example of the external view of the weight measuring apparatus  10  according to embodiments of the present embodiment; 
           [0063]      FIG. 4A  is a diagram illustrating an example of a structure of a load sensor section  12 ; 
           [0064]      FIG. 4B  is a diagram illustrating the example of the structure of the load sensor section  12 ; 
           [0065]      FIG. 4C  is a diagram illustrating the example of the structure of the load sensor section  12 ; 
           [0066]      FIG. 4D  is a diagram illustrating the example of the structure of the load sensor section  12 ; 
           [0067]      FIG. 5  is a diagram illustrating the interior of the weight measuring apparatus  10  according to the embodiments of the present invention; 
           [0068]      FIG. 6  is a diagram illustrating an example of an electrical configuration of the weight measuring apparatus  10  according to the embodiments of the present invention; 
           [0069]      FIG. 7A  is a diagram schematically illustrating an example of a weight applying unit  50  according to the embodiments of the present invention; 
           [0070]      FIG. 7B  is a diagram schematically illustrating the example of the weight applying unit  50  according to the embodiments of the present invention; 
           [0071]      FIG. 7C  is a diagram schematically illustrating the example of the weight applying unit  50  according to the embodiments of the present invention; 
           [0072]      FIG. 7D  is a diagram schematically illustrating the example of the weight applying unit  50  according to the embodiments of the present invention; 
           [0073]      FIG. 8A  is a diagram illustrating a state where the weight measuring apparatus  10  is placed on a placement table  51 ; 
           [0074]      FIG. 8B  is a diagram illustrating the state where the weight measuring apparatus  10  is placed on a placement table  51 ; 
           [0075]      FIG. 9  shows an example of data stored in a microcomputer  31 ; 
           [0076]      FIG. 10  is a schematic diagram illustrating a state where the weight measuring apparatus  10  is actually used; 
           [0077]      FIG. 11  is a schematic diagram illustrating a state where a load cell is actually used; 
           [0078]      FIG. 12  is a schematic diagram illustrating a state where the weight measuring apparatus  10  is placed on the placement table  51  with a deflection generating member  61  interposed therebetween; 
           [0079]      FIG. 13  is a schematic diagram illustrating a state where a load is applied with the deflection generating member  61  interposed between the weight measuring apparatus  10  and the placement table  51 ; 
           [0080]      FIG. 14  is a diagram illustrating an example of the deflection generating member  61 ; 
           [0081]      FIG. 15  is a table showing measurement results obtained when using the weight measuring apparatus  10  on which a calibration is performed by a method according to a first embodiment; 
           [0082]      FIG. 16  is a table showing measurement results obtained when using the weight measuring apparatus  10  on which the calibration is performed by a method according to a second embodiment; and 
           [0083]      FIG. 17  is a diagram illustrating an example of values detected by load sensors when a weight is placed on a load platform. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
       [0084]    Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the embodiments to be described below are not limited to the present invention. 
         [0085]    Firstly, a principle of a weight applying/calibration method according to a first embodiment will be described. As shown in  FIG. 1 , in a conventional weight applying/calibration method in which a weight is placed on a load platform with a plurality of load sensors (i.e., leg portions) of a weight measuring apparatus facing downward, one load is distributed among the plurality of load sensors, and thus a proper calibration cannot be performed. On the other hand, according to the present invention, instead of performing a calibration by placing a weight on the load platform so as to indirectly apply weight to the load sensors, the calibration is performed by directly applying the weight to load sensor sections  12 . That is to say, as shown in  FIG. 2 , the calibration is performed by applying weight to one load sensor in such a manner that the weight applied to the one load sensor is assuredly not to be distributed with the other load sensor. 
         [0086]    Hereinafter, the weight applying/calibration method according to the first embodiment will be described in detail.  FIG. 3A  is a diagram illustrating an example of an external view of a weight measuring apparatus  10  (a scale, typically).  FIG. 3B  is a left side view illustrating the example of the external view of the weight measuring apparatus  10 .  FIG. 3C  is a right side view illustrating the example of the external view of the weight measuring apparatus  10 .  FIG. 3D  is a front view illustrating the example of the external view of the weight measuring apparatus  10 .  FIG. 3E  is a back view illustrating the example of the external view of the weight measuring apparatus  10 .  FIG. 3F  is a bottom view illustrating the example of the external view of the weight measuring apparatus  10 .  FIG. 3G  is a perspective view as viewed from a top of the weight measuring apparatus  10 .  FIG. 3H  is a perspective view as viewed from a bottom of the weight measuring apparatus  10 . The weight measuring apparatus  10  comprises a load platform  11  on which a user stands, the four load sensor sections  12  respectively provided on a bottom surface of the load platform  11  in four corners thereof, and a connector  13  connectable to a predetermined external apparatus. 
         [0087]    Each of the load sensor sections  12  detects a load applied to the load platform  11 .  FIG. 4A  is an exploded view illustrating an example of a structure of each of the load sensor sections  12 .  FIG. 4B  is a perspective view illustrating the example of the structure of each of the load sensor sections  12 .  FIG. 4C  is a top view illustrating the example of the structure of each of the load sensor sections  12 .  FIG. 4D  is a cross-sectional view along lines A-A shown in  FIG. 4C . In  FIGS. 4A to 4D , each of the load sensor sections  12  includes an upper plate  22 , a load cell  23 , a lower plate  24 , screws  21  and  25 , a load receiving plate  26 , a housing  27 , and a rubber leg  28 . As shown in  FIG. 4A , the load cell  23  is disposed so as to be interposed between the upper plate  22  and the lower plate  24 . The screw  21  is inserted so as to pass through a hole provided with the upper plate  22  and a hole, corresponding to the hole of the upper plate  22 , which is provided with the load cell  23 . Similarly, the screw  25  is inserted so as to pass through a hole provided with the lower plate  24 , and a hole, corresponding to the hole of the lower plate  24 , which is provided with the load cell  23 . Thus, the load cell  23  is fixed by means of the upper plate  22  and the lower plate  24 . Furthermore, the load receiving plate  26  is disposed in a center portion of the interior of the housing  27 , and the load cell  23  fixed by means of the upper plate  22  and the lower plate  24  is disposed above the load receiving plate  26 . The rubber leg  28  is disposed in a center portion of a bottom surface of the housing  27 . 
         [0088]    The load cell  23  is a strain gage type load cell, for example. The load cell  23  is a load conversion unit for converting an inputted load into an electrical signal. In the load cell  23 , a strain element  23   a  is deformed in accordance with the inputted load, thereby generating a strain. A strain sensor  23   b  attached to the strain element  23   a  converts the strain into a value indicating an electrical resistance change so as to be further converted into a value indicating a voltage change. Therefore, the load cell  23  outputs a voltage signal indicating the inputted load from an input terminal when a voltage is applied from a power terminal. 
         [0089]    The housing  27  is formed so as to have a substantially bottomed cylindrical shape by plastic molding, for example. 
         [0090]      FIG. 5  is a perspective view illustrating the interior of the weight measuring apparatus  10 . In  FIG. 5 , a frame  15 , disposed along the periphery of the weight measuring apparatus  10 , acts as a skeletal structure of the weight measuring apparatus  10 . Furthermore, a microcomputer board  14 , on which a microcomputer  31  to be described later is mounted, is located in the interior of the weight measuring apparatus  10 . The microcomputer board  14  is electrically connected to the four load sensor sections  12  (more precisely, the load cells  23 ) respectively provided in the four corners of the weight measuring apparatus  10  and the connector  13 . 
         [0091]      FIG. 6  is a diagram illustrating an example of an electrical configuration of the weight measuring apparatus  10 . In  FIG. 6 , solid-line arrows indicate signal and communication flows, and dashed-line arrows indicate a power supply. 
         [0092]    The weight measuring apparatus  10  further comprises the microcomputer  31  for controlling an operation thereof. The microcomputer  31  includes a ROM, RAM and the like, all of which are not shown, and controls the operation of the weight measuring apparatus  10  in accordance with a program stored in the ROM. Further, the RAM is, for example, a nonvolatile memory such as a flash memory. 
         [0093]    An AD converter  32 , the connector  13  and a DC-DC converter  33  are connected to the microcomputer  31 . The load cells  23  included in the load sensor sections  12 , respectively, are connected to the AD converter  32  via respective amplifiers  34 . 
         [0094]    The connector  13  is provided so as to allow the weight measuring apparatus  10  to communicate with the predetermined external apparatus such as a personal computer or a game apparatus. 
         [0095]    Furthermore, a battery  35  is mounted in the weight measuring apparatus  10  for a power supply. In the present embodiment, the external apparatus connected to the weight measuring apparatus  10  by means of the connector  13  controls a power supply to the microcomputer  31 . On the other hand, the microcomputer  31  controls a power supply to the load cells  23 , the amplifiers  34  and the AD converter  32 . To the load cells  23 , the amplifiers  34 , the microcomputer  31  and the AD converter  32 , a power is supplied from the battery  35  via the DC-DC converter  33 . The DC-DC converter  33  converts a voltage value of a DC current drawn from the battery  35  into a different voltage value, so as to be outputted to the load cells  23 , the amplifiers  34 , the microcomputer  31  and the AD converter  32 . 
         [0096]    When a power is supplied, each of the load cells  23  outputs a signal indicating the inputted load. The signal is amplified by each of the amplifiers  34 , and the amplified analog signal is converted by the AD converter  32  into a digital signal so as to be inputted to the microcomputer  31 . Identification information of each load cell  23  is assigned to a detection value of the load cell  23  so as to be distinguishable from detection values of the other load cells  23 . As described above, the microcomputer  31  can obtain data indicating the detection values of the four respective load cells  23  at the same time. Then, the data indicating the detection values of the respective load cells  23  is transmitted from the microcomputer  31  to the external apparatus via the connector  13 . 
         [0097]    Next, a weight applying unit used in the first embodiment will be described. The weight applying unit is used for applying weight to the load sensor sections  12 .  FIG. 7A  is a front view schematically illustrating a weight applying unit  50 .  FIG. 7B  is a plan view schematically illustrating the weight applying unit  50 .  FIG. 7C  is a right side view schematically illustrating the weight applying unit  50 .  FIG. 7D  is a left side view schematically illustrating the weight applying unit  50 . 
         [0098]    In  FIGS. 7A to 7D , the weight applying unit  50  comprises a placement table  51 , leg portions  52  for supporting the placement table  51 , four hook portions  53   a  to  53   d  mounted so as to perpendicularly penetrate the placement table  51 , a plurality of weights  54   a  to  54   d  detachable from the four hook portions  53   a  to  53   d , respectively, and four hoisting and lowering mechanisms  55   a  to  55   d  disposed at positions corresponding to the hook portions  53   a  to  53   d , respectively. 
         [0099]    Furthermore, as shown in  FIG. 7B , the placement table  51  has four through holes  56   a  to  56   d  provided therethrough. Each through hole  56  is provided at a position corresponding to each of the four corners of the weight measuring apparatus  10  placed on the placement table  51 , that is, a position corresponding to a position of each of the load sensor sections  12 . 
         [0100]    The four hook portions  53   a  to  53   d  have circular shaped load applying plates  531   a  to  531   d , and attachment portions  532   a  to  532   d  for attaching the weights  54  thereto, respectively. As shown in  FIG. 7A  or the like, each of the hook portions  53  is disposed through the through hole  56  such that the load applying plate  531  is located above the placement table and the attachment portion  532  is located below the placement table  51 . That is, when each of the weights  54  is attached to the attachment portion  532 , the entirety of the hook portion  53  is perpendicularly lowered by the weight of the attached weight  54 . 
         [0101]    Each of the weights  54  is detachable from the attachment portion  532 . Furthermore, each weight  54  is formed of a plurality of weight parts ( 541  to  544  in  FIG. 7A ), and the weight applied to the hook portion  53  is adjustable depending on the number of the weight parts attached to the attachment portion. 
         [0102]    Each of the hoisting and lowering mechanisms  55  is used to carry the weight  54  in an up and down direction when performing a process of attaching the weight  54  to the attachment portion  532 . 
         [0103]    Next, the weight applying/calibration method according to the first embodiment will be described. In the first embodiment, a load is directly applied to each of the load sensor sections  12  in such a manner as described above so as to cause the microcomputer  31  of the weight measuring apparatus  10  to store a value outputted from each of the load sensor sections  12 , thereby performing a calibration. 
         [0104]    Firstly, the weight measuring apparatus  10  is placed on the placement table  51  with a load platform surface of the weight measuring apparatus  10  facing downward (i.e., in an inverted position) (step  1 ). At this time, the weight measuring apparatus  10  is placed on the placement table  51  such that the load sensor sections  12  are located at positions where the through holes  56   a  to  56   d  are provided, respectively. In other words, the weight measuring apparatus  10  is placed on the placement table  51  such that the load sensor sections  12   a  to  12   d  are located under the load applying plate  531   a  to  531   d  of the hook portions  53   a  to  53   d , respectively.  FIG. 8A  is a front view illustrating a state where the weight measuring apparatus  10  is placed on the placement table  11 .  FIG. 8B  is a plan view illustrating the state where the weight measuring apparatus  10  is placed on the placement table  11 . 
         [0105]    Then, the connector  13  is connected to the external apparatus (step  2 ). The external apparatus is used for monitoring a load value outputted from the weight measuring apparatus  10  and causing the microcomputer  31  to write the load value, for example. 
         [0106]    Next, in a state where no load (i.e., 0 kg) is applied to each of the load sensor sections  12 , a detection value thereof is obtained. Thereafter, the external apparatus causes a RAM of the microcomputer  31  to store the detection value so as to be associated with each of the load sensor sections  12  (step  3 ). 
         [0107]    Then, each of the hoisting and lowering mechanisms  55  is used to lift the weight  54 , and the weight  54  having a predetermined weight (e.g., 17 kg) is attached to the attachment portion  532  of each of the four hook portions  53  (step  4 ). In this state, the weight  54  is supported by each of the hoisting and lowering mechanisms  55 . Note that it is preferable that the weights  54  attached to the hook portions  53 , respectively, have the same weight as one another. 
         [0108]    Next, after attaching the weights  54  to the hook portions  53 , respectively, the hoisting and lowering mechanisms  55  are used to simultaneously bring down the weights  54  attached at four locations, respectively (step  5 ). In this state, the weight  54  attached to each of the hook portions  53  is not supported by the hoisting and lowering mechanism  55 . As a result, each of the hook portions  53  is lowered by the weight of the weight  54 , and the load applying plate  531  contacts each of the load sensor sections  12  located so as to be opposed thereto, thereby pressing down each of the load sensor sections  12 . Thus, it becomes possible to directly apply a load corresponding to the weight of the weight  54  attached to each of the hook portions  53  to each of the load sensor sections  12 . 
         [0109]    Then, the external apparatus obtains the detection value outputted from each of the load sensor sections  12 . Thereafter, the external apparatus causes the RAM of the microcomputer  31  to store the detection value as information on the weight of the currently attached weight  54  (i.e., as a detection value obtained when a load of 17 kg is applied) so as to be associated with each of the load sensor sections  12  (step  6 ). 
         [0110]    Such a process of applying a desired load to each of the load sensor sections  12  and causing the microcomputer  31  to store a detection value of each of the load sensor sections  12  to which the desired load is currently applied (steps  4  to mentioned above) is repeated by using a load having a desired weight value. For example, loads of 34 kg, 68 kg and 102 kg are sequentially applied to each of the load sensor sections  12 , and the microcomputer  31  is caused to store a detection value detected when each of the loads is applied to each of the load sensor sections  12 .  FIG. 9  shows an example of data stored in the RAM of the microcomputer  31  as a result of such a process. In  FIG. 9 , data, indicating a detection value outputted from each load cell  23  each time a load having a predetermined weight is applied, is stored for each of the load sensor sections  12 . Note that in  FIG. 9 , the data indicating the detection value outputted from the load cell  23  is represented as an AD converted value. As such, the calibration according to the first embodiment is finished. 
         [0111]    When the weight measuring apparatus  10  calibrated in such a manner as described above is actually used, a value detected by each of the load sensor sections  12  and the data as shown in  FIG. 9  are used. For example, in the external apparatus (e.g., a game apparatus) connected to the weight measuring apparatus  10 , the detection value of each of the load sensor sections  12  and the data shown in  FIG. 9  are obtained from the weight measuring apparatus  10 . Thereafter, a predetermined calculation process is performed based on the aforementioned value and data, thereby calculating the weight. 
         [0112]    As described above, in the present embodiment, a load can be independently applied to each of the four load sensor sections  12 . Thus, a more proper calibration can be performed on each of the load sensor sections  12 , thereby making it possible to improve a measurement accuracy of the weight measuring apparatus  10 . As a result, in the case where a balance state of a measurement target object is detected based on an output value of each of the load sensors, for example, it becomes possible to more accurately recognize the balance state of the measurement target object. 
         [0113]    In the above embodiment, as a mechanism to apply a load to each of the load sensor sections  12 , the weight measuring apparatus  10  is placed on the placement table  51  in an inverted position, and then the weight  54  is attached to the hook portion  53 , thereby applying a load to each of the load sensor sections  12 . However, the present invention is not limited thereto. Other mechanisms may also be used if they directly apply a load to each of the load sensor sections  12 . For example, the weight measuring apparatus  10  may be placed on the placement table  51  without being inverted such that a load is applied to each of the load sensor sections  12  through the through hole  56  so as to press up the weight measuring apparatus  10  from below. 
         [0114]    In the above embodiment, the external apparatus is used to cause the microcomputer  31  to store the data indicating the detection value outputted from the load cell  23 . However, a function corresponding to the external apparatus may be embedded in the weight applying unit  50 . For example, a connection section electrically connectable to the connector  13  of the weight measuring apparatus  10 , a control section having a calculation control function such as a CPU, and an operation section for transmitting an instruction to the control section may be mounted in the weight applying unit  50 . Then, a process as shown in step  6  mentioned above may be performed by means of the control section. In such an example as described above, it is unnecessary to prepare an external apparatus in a separate manner. 
       Second Embodiment 
       [0115]    Next, a second embodiment of the present invention will be described with reference to  FIGS. 10 to 16 . In the first embodiment described above, a load of the weight  54  is applied to each of the load sensor sections  12  so as to perform a calibration. In the case where the calibration is performed in such a manner as described above, a measurement error can be substantially suppressed as compared to when using a conventional calibration method. However, under actual usage conditions, in the case where the weight measuring apparatus  10  is mounted in the place of use and a person, for example, steps onto the load platform  11 , the load platform  11  is more or less deflected due to the weight of the person, as shown in  FIG. 10 . That is, the frame  15  forming the weight measuring apparatus  10  is deformed due to the weight of the person, and each of load sensor sections  12  is accordingly slightly inclined in its entirety. As a result, as shown in  FIG. 11 , the load cell  23  is to be accordingly slightly inclined in its entirety. When the measurement is performed in a state described above, the measurement error would be more or less generated even if the calibration according to the first embodiment is performed. 
         [0116]    Specifically, the calibration according to the first embodiment assumes that a load applied to each load sensor section  12  (load cell  23 ) is measured when the load sensor section  12  is in a horizontal state. However, under actual usage conditions, the load applied to each load sensor section  12  is measured when the load cell  23  is inclined in its entirety due to the aforementioned deflection. Therefore, since the calibration is performed assuming that the load sensor section  12  is in a horizontal state, a measurement error between an actual weight and a detection value thereof is generated. Thus, in the second embodiment, a calibration is performed in a state where the aforementioned deflection is taken into consideration, in other words, in a state similar to an actual usage state where the load cell  23  is inclined in its entirety. 
         [0117]    Next, a principle of the weight applying/calibration method according to the second embodiment will be described. Note that the weight applying unit  50  according to the second embodiment is the same as that of the first embodiment except for a deflection generating member  61  to be described below. Therefore, the same components as those of the first embodiment will be denoted by the same reference numerals and will not be further described below. In the second embodiment, when the weight measuring apparatus  10  is placed on the placement table  51  in such a manner as described above, the deflection generating member  61  (to be described later in detail) is disposed so as to be interposed between the placement table  51  and the weight measuring apparatus  10 .  FIG. 12  is a schematic diagram illustrating a state where the deflection generating member  61  is disposed so as to be interposed between the weight measuring apparatus  10  and the placement table  51 . In this state, similarly to the first embodiment, the weight  54  is attached to each of the hook portions  53 , thereby applying the weight of the weight  54  to each of the load sensor sections  12 . Therefore, as shown in  FIG. 13 , it is possible to create a state where the deflection as mentioned above is generated in the weight measuring apparatus  10 . Thus, a proper calibration can be performed taking into consideration the deflection generated under actual usage conditions. 
         [0118]    Hereinafter, the deflection generating member  61  will be described in detail.  FIG. 14  is a diagram illustrating an example of an external view of the aforementioned deflection generating member  61 .  FIG. 14  includes seven images: (A) is a plan view; (B) is a left side view; (C) is a right side view; (D) is a front view; (E) is a back view; (F) is a bottom view; and (G) is a perspective view. As shown in  FIG. 14 , the deflection generating member  61  has a rectangular plate-like shape. The rectangular plate-like shape is a shape simulating an area in which a weight measurement target object contacts the load platform (i.e., an area to which a load is applied). In the present embodiment, it is assumed that the aforementioned area is a sole of the foot. Considering variations in size of a sole of the foot among individuals and preventing an applied load from being concentrated onto one spot, the deflection generating member  61  has a rectangular shape having a substantial area. In the present embodiment, it is also assumed that one deflection generating member  61  is one foot. Therefore, a total of two deflection generating members, as both feet, are used. 
         [0119]    Next, a material of the deflection generating member  61  will be described. The material used for the deflection generating member  61  has preferably elasticity to some extent. This is because even when a stress is applied to an end of the deflection generating member  61  in a state where a load is applied to the weight measuring apparatus  10  and deflection is generated, the stress would be dispersed if the deflection generating member  61  had the elasticity, thereby not hampering the deflection of the weight measuring apparatus  10 . Furthermore, with the elasticity, the load platform surface of the weight measuring apparatus  10  can be prevented from being damaged through calibration steps. In the present embodiment, the deflection generating member  61  is made of ester polyurethane as an example. Specifically, the ester polyurethane has a specific gravity of 1.20, a Shore hardness of Shore A70 (i.e., approximately a hardness of a rubber ball used in baseball), a tensile strength of 31.3 Mpa, an elongation of 650%, a heat resistance of 70° C., and a cold resistance of −20° C. 
         [0120]    Then, a difference between an effect produced when a calibration is performed with the deflection generating member  61  and an effect produced when a calibration is performed without the deflection generating member  61  will be described with reference to  FIGS. 15 and 16 .  FIG. 15  is a table showing results detected by a test unit other than the weight applying unit  50  when weights of 34 kg, 68 kg, 102 kg and 136 kg are placed on the load platform of the weight measuring apparatus  10  on which a calibration is performed without the deflection generating member  61  (i.e., by using the method of the first embodiment). Also,  FIG. 16  is a table showing results detected by the test unit other than the weight applying unit  50  when the weights of 34 kg, 68 kg, 102 kg and 136 kg are placed on the load platform of the weight measuring apparatus  10  on which a calibration is performed with the deflection generating member  61  (i.e., by using the method of the second embodiment). In each of  FIGS. 15 and 16 , the measurement is performed ten times for each of the weights (“sample No” indicates an Nth measurement (N is an integer of 1 to 10)). Also, a maximum value, a minimum value and an average value among values obtained by ten measurements are indicated as “MAX”, “MIN” and “AVG”, respectively. A difference between the average value AVG and the weight of an actually placed weight (a reference value) is indicated as “difference from reference value”. 
         [0121]    For example, when the weight of 34 kg is placed, “difference from reference value” is “−0.191” in  FIG. 15 , while the value is “−0.027” in  FIG. 16 . That is, an error between the weight of an actual measurement object and a detection value thereof is smaller when using the weight measuring apparatus  10  on which a calibration is performed with the deflection generating member  61 . 
         [0122]    Also, in  FIG. 15 , “difference from reference value” obtained when the weight of 34 kg is placed is “−0.191” while the value obtained when the weight of 136 kg is placed is “−0.504”, and a difference between the aforementioned two values is “0.313”. On the other hand, in  FIG. 16 , “difference from reference value” obtained when the weight of 34 kg is placed is “−0.027” while the value obtained when the weight of 136 kg is placed is “0.133”, and a difference between the aforementioned two values is “0.106”, which is smaller than “0.313” in  FIG. 15 . That is, in both cases shown in  FIGS. 15 and 16 , “difference from reference value” tends to be greater as the weight of a measurement object is increased. However, the fluctuation of “difference from reference value” varied in accordance with the weight of the measurement object is smaller in the case shown in  FIG. 16 . That is, a more accurate measurement can be performed when using the weight measuring apparatus  10  on which a calibration is performed with the deflection generating member  61 . 
         [0123]    As described above, in the present embodiment, a calibration is performed with the deflection generating member  61 , thereby making it possible to create a state more similar to actual usage conditions. Therefore, a proper calibration can be performed, and thus a measurement accuracy of the weight measuring apparatus  10  also can be improved accordingly. 
         [0124]    In the second embodiment, the aforementioned deflection is generated by interposing an elastic member (the deflection generating member made of polyurethane) between the placement table  51  and the weight measuring apparatus  10 . However, the present invention is not limited to the above example of such a member interposed between the placement table  51  and the weight measuring apparatus  10  if the deflection is generated. For example, a through hole may be provided through the placement table  51  at a position where the deflection generating member  61  is to be disposed, so as to create a mechanism to mechanically apply pressure to the load platform  11  through the through hole from below. 
         [0125]    While the invention has been described in detail, the foregoing description is in all aspects illustrative and not restrictive. It is understood that numerous other modifications and variations can be devised without departing from the scope of the invention.