Digital scale

Example 1 of the present invention exemplifies a digital scale (hereinafter simply referred to as “scale”) which acquires a highly reliable body weight value in a short measurement time by switching scale intervals which are minimum indicated values representing weight measurement accuracy which have been set at multiple levels in advance according to the degree of variation of sampled body weight digital data (hereinafter simply referred to as “data”).

Hereinafter, Example 1 will be described with reference to the drawings. FIG. 1 is a block diagram illustrating an overview of the configuration of electrical circuit incorporated in a scale 1 which is an example of the present invention. FIG. 2 is a flowchart illustrating the operation of the scale 1 . FIGS. 3(A) and 3(B) are graphs illustrating time-series fluctuation of body weight value when a subject stands on the scale 1 . FIG. 3(A) is a graph illustrating the time-series fluctuation when the subject stands on the scale 1 in a normal state. FIG. 3(B) is a graph illustrating the time-series fluctuation when the subject stands on the scale 1 immediately after exercise.

As shown in FIG. 1 , the scale 1 comprises a load sensor 2 , an A/D converter 3 , a control section 4 , a computing section 5 , a judgment section 6 , a scale interval switching section 7 , a storage section 8 , a display section 9 and a power supply 10 . The load sensor 2 is connected to the control section via the A/D converter 3 and constitutes data acquiring means for acquiring data about the body weight of a subject who stands on the scale 1 . The computing section 5 computes a data fluctuation range based on a variation of the above acquired data, a body weight value according to a scale interval, and the like. The judgment section 6 determines which of allowable ranges of the data fluctuation range that have been set for multiple levels of scale intervals the data fluctuation range falls within by comparing the allowable ranges with the data fluctuation range and also makes a determination associated with display of the body weight value. The scale interval switching section 7 switches the scale interval according to the result of the determination. The storage section 8 stores the above data, computed data fluctuation range and body weight value, scale intervals set at multiple levels that are to be bases for the accuracy of the body weight value and allowable ranges of the data fluctuation range that correspond to the above scale intervals. The display section 9 displays at least the body weight value computed based on the above scale interval. The power supply 10 supplies electric power to the scale 1 .

The scale 1 operates as follows. That is, as shown in FIG. 2 , when the power of the scale 1 is turned on and a measurement is started, the scale 1 samples and acquires data about a body weight value imposed on the scale 1 by the data acquiring means and stores the data in the storage section 8 in STEP S 1 . In STEP S 2 , it is determined whether the above acquired data has reached a predetermined number of data. In this case, sampling time is 50 milliseconds, and the above predetermined number of data refers to the number of data acquired per second. In the above STEP S 2 , when the acquired data has not reached the predetermined number of data, the scale 1 proceeds to “NO” and returns to STEP S 1 and repeats sampling, while when the acquired data has reached the predetermined number of data, the scale 1 proceeds to “YES” and computes a variation in data acquired for the predetermined number of data in the computing section 5 in STEP S 3 . In this case, a data fluctuation range A (g) is calculated from the difference between the maximum and minimum values of the data.

In each of subsequent STEPS S 4 to S 7 , the degree of variation of the above data fluctuation range A is determined in the judgment section 6 . More specifically, the judgment section 6 compares the data fluctuation range A with each of allowable ranges of the data fluctuation range which have been set for multiple levels of scale intervals, starting from the narrowest allowable range, and determines which of the allowable ranges the data fluctuation range A falls within. In the present example, the above scale interval is set at multiple levels of 10 g, 20 g, 50 g and 100 g and stored in the storage section 8 together with allowable ranges of the data fluctuation range for ensuring the reliability of a body weight value computed based on each scale interval. Further, the above allowable range of data fluctuation range which is stored for each scale interval is less than a half of each scale interval.

First, in STEP S 4 , it is determined whether the data fluctuation range A satisfies 0≦A<5. This allowable range ensures the reliability of a body weight value computed based on a scale interval of 10 g. When the data fluctuation range A is within this allowable range, the scale 1 proceeds to “YES” and the scale interval is switched to 10 g in the scale interval switching section 7 in STEP S 8 . Meanwhile, when the data fluctuation range A is equal to or larger than 5 g, the scale 1 proceeds to “NO”, and the data fluctuation range A is compared with the next allowable range in STEP S 5 . In STEP S 5 , it is determined whether the data fluctuation range A satisfies 5≦A<10. This allowable range ensures the reliability of a body weight value computed based on a scale interval of 20 g. When the data fluctuation range A is within this allowable range, the scale 1 proceeds to “YES” and the scale interval is switched to 20 g in the scale interval switching section 7 in STEP S 9 . Meanwhile, when the data fluctuation range A is equal to or larger than 10 g, the scale 1 proceeds to “NO” and the data fluctuation range A is compared with the next allowable range in STEP S 6 . In STEP S 6 , it is determined whether the data fluctuation range A satisfies 10≦A<25. This allowable range ensures the reliability of a body weight value computed based on a scale interval of 50 g. When the data fluctuation range A is within this allowable range, the scale 1 proceeds to “YES” and the scale interval is switched to 50 g in the scale interval switching section 7 in STEP S 10 . Meanwhile, when the data fluctuation range A is equal to or larger than 25 g, the scale 1 proceeds to “NO” and the data fluctuation range A is compared with the next allowable range in STEP S 7 . In STEP S 7 , it is determined whether the data fluctuation range A satisfies 25≦A<50. This allowable range ensures the reliability of a body weight value computed based on a scale interval of 100 g. When the data fluctuation range A is within this allowable range, the scale 1 proceeds to “YES” and the scale interval is switched to 100 g in the scale interval switching section 7 in STEP S 11 .

Meanwhile, when the data fluctuation range A is equal to or larger than 50 g, the scale 1 proceeds to “NO” and returns to STEP S 1 to carry out sampling of data again because a body weight value cannot be computed based on the above provided scale intervals due to an excessively large variation of the data. At that time, the oldest data out of the data stored in the storage section 8 is deleted, and newly acquired data is stored.

Next, an example of the relationship between the magnitude of the data fluctuation range A and the scale interval will be specifically described by use of experimentally acquired data illustrated in FIGS. 3(A) and 3(B) . According to a graph in FIG. 3(A) illustrating time-series fluctuation of body weight value measured when a subject is in a normal state, because the fluctuation range A of data sampled in 1 second between 10.6 seconds and 11.6 seconds (sampling time: 50 ms) is 3(g) and is within a range of 0≦A<5, the scale interval can be switched to 10(g). Further, according to a graph in FIG. 3(B) illustrating time-series fluctuation of body weight value measured immediately after the subject has finished exercising, because the fluctuation range A of data sampled in 1 second between 10.6 seconds and 11.6 seconds (sampling time: 50 ms) is 42(g) and is within a range of 25≦A<50, the scale interval is switched to 100(g).

When the scale interval is switched in the scale interval switching section 7 in each of the above STEPS S 8 to S 11 , a body weight value is computed based on the above scale interval in the computing section 5 . In this case, the average of the predetermined number of data stored in the storage section 8 is computed as the body weight value, and the body weight value and the scale interval are stored in the storage section 8 . In subsequent STEP S 13 , it is determined in the judgment section 6 whether the scale interval that has been used as a basis for the computation to obtain the above stored body weight value is the smallest scale interval (in this case, 10 g) out of the scale intervals which have been set at multiple levels and stored in advance. When it is the smallest scale interval, the scale 1 proceeds to “YES” and displays the above body weight value and scale interval in the display section 9 in STEP S 16 and ends the measurement regardless of predetermined measurement time to be described later. Meanwhile, when it is not the smallest scale interval, the scale 1 proceeds to “NO” and it is determined in the judgment section 6 whether the predetermined measurement time required until the body weight value is displayed has been reached in STEP S 14 . When the predetermined time has not been reached, the scale 1 proceeds to “NO” and returns to STEP S 1 to carry out sampling of data again. In this case as well, the oldest data out of the data stored in the storage section 8 is deleted, and newly acquired data is stored, as described above. Meanwhile, when the predetermined measurement time has been reached, the scale 1 proceeds to “YES”, selects the smallest scale interval out of the scale intervals stored together with the body weight value in the above STEP S 12 and reads out the body weight value from the storage section 8 in STEP S 15 , and displays the body weight value and scale interval in the display section 9 in STEP S 16 . However, when no body weight value is stored in the storage section 8 , a measurement error is displayed in the display section 9 to explain that the body weight value cannot be computed and stored with the above provided scale intervals because the above fluctuation range A is too large.

The above Example 1 performs determination and switching of scale interval and computation of body weight value based on the scale interval for each sampling. Meanwhile, Example 2 of the present invention switches a scale interval based on a predetermined number of data acquired after passage of predetermined time in which a body weight is expected to become stable after a subject stands on a scale.

The constitution of the present Example 2 is the same as that of the scale 1 described by use of FIG. 1 in Example 1 and is therefore not illustrated. However, since some of the processes in the sections are different, the scale in the present Example 2 will be referred to as a body scale 101 .

Hereinafter, the operation of the scale 101 will be described by use of a flowchart in FIG. 4 illustrating the operation of Example 2. When the power of the scale 101 is turned on and a measurement is started, the scale 101 samples and acquires data about a body weight value imposed on the scale 101 by the data acquiring means and stores the data in the storage section 8 in STEP S 101 . In STEP S 102 , it is determined in the judgment section 6 based on the acquired data whether the load is equal to or larger than a predetermined value. In this case, it is determined whether a subject has stood on the scale 101 . When the load is smaller than the predetermined value, the scale 101 proceeds to “NO” and returns to STEP S 101 and continues sampling, while when the load is equal to or larger than the predetermined value, the scale 101 proceeds to “YES”, and it is determined in STEP S 103 whether a predetermined time has elapsed since it was detected that the load was equal to or larger than the predetermined value, i.e. that the subject stood on the scale 101 . In this case, the above predetermined time is time in which the body weight is expected to become stable after the subject stands on the scale 101 and is set in advance. When the predetermined time has not elapsed, the scale 101 proceeds to “NO” and returns to STEP S 101 and stands by while repeating sampling, while when the predetermined time has elapsed, the scale 101 proceeds to “YES” and counts the above data in STEP S 104 .

Descriptions of the operations in STEPS S 105 to S 115 are omitted because they are the same as those in STEPS S 2 to S 12 illustrated in the flowchart of FIG. 2 in Example 1. However, in STEP S 110 of FIG. 4 , the scale 101 displays a measurement error in the display section 9 for the reason that the above fluctuation range A is too large when the result of determining whether 25≦A<50 holds is “NO”, while in the corresponding STEP S 7 of FIG. 2 , the scale 1 returns to STEP S 1 and carries out sampling again. In subsequent STEP S 116 , the body weight value computed based on the switched provided scale interval in the above STEP S 115 is displayed in the display section 9 .

Further, it is also possible that in STEP S 1 of Example 1 and STEP S 101 of Example 2, sampled data is subjected to a moving average procedure and the fluctuation range A is determined based on each value subjected to the moving average procedure.

Further, although a computed or stored body weight value and a scale interval which is a basis for computation of the body weight value out of preset scale intervals are displayed in the display section 9 in Examples 1 and 2, the data fluctuation range A may also be displayed in the display section 9 as the magnitude of body motion (e.g. “body sway A (g)”).