JPH05149781A - Electronic balance - Google Patents

Abstract

PURPOSE:To inexpensively reduce the weight measuring error of an electronic balance at its minimum scale switching point by averaging weight measuring errors over a whole weight measuring range. CONSTITUTION:A counter value obtained when no article is placed on a balance section 9 is stored in the area 3a of a RAM 3 and the counter value obtained when the maximum weight is measured is stored in the area 3b of the RAM 3. In addition, the counter value corresponding to the weight at which the minimum scale is switched is stored in the area 3c of the RAM 3. The weight measuring error of a switched weight is calculated by calculating a theoretical count value zero-corrected for the switched weight from the counter values stored in the areas 3b and 3c and subtracting an actually measured value. Then an assumed error at the maximum weight is calculated by multiplying the calculated weight measuring error by the ratio of the maximum weight to the switching weight and a corrected span value is calculated by adding 50% of the count value to the difference between the counter values stored in the areas 3b and 3a. The corrected span value is stored in the area 3b of the RAM 3. A CPU 1 converts data converted by means of an A/D converter 10 into a weight based on the corrected span value and counter value (at zero point) stored in the area 3a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic scale that weighs an article and digitally processes the measured value.

[0002]

2. Description of the Related Art In a conventional electronic scale, the weight of an article is weighed by a scale section composed of a load cell and the voltage data output from the load cell and the like is measured by A / D (analogue / dig).
Ital) Convert to digital data by a converter. The digital data is converted into a weight value based on the zero point data and the span data.

The zero point data is digital data converted by an A / D converter in a state where no article is placed on the scale section, and the span data is the maximum weight preset by this electronic scale. The zero point data is subtracted from the maximum weight value data, which is digital data converted by the A / D converter when the article corresponding to the value is weighed.

For example, the maximum weight value (maximum weight value) is 10
If the zero point data is 10000 ct (count) and the maximum weight value data is 110000 ct in an electronic scale of Kg (10000 g), the span data is 1
If the weighing characteristic is linearly obtained, the digital data converted by the A / D converter is 1
It will be 9000 ct. Furthermore, it is converted into a weight value by the following formula. (19000-10000) ÷ (100000/10000) = 900 The first item “−10000” is zero point data, and the second
The denominator of the term is maximum weight data and the numerator of the second term is span data.

However, the weighing characteristics are not generally obtained linearly, and there is no problem in weighing the articles corresponding to the zero point data and the maximum weight value data, but in the intermediate weight of the weighing range, the load cell to be used. Due to such accuracy, a large error occurs in the + direction or the-direction.

In general, there are electronic scales in which the minimum scale of the display is switched using a predetermined weight as a switching point.
For example, with 1 Kg as the switching point, 0 Kg to 1 Kg is displayed in 1 g units, and 1 Kg to 10 Kg is 10
It is displayed in units of g. On the other hand, depending on the standard for error, 1g
In the case of the display, the error larger than ± 1g is not recognized.
In the case of 0 g display, no error larger than ± 10 g is recognized. That is, an error of up to 10 ct is recognized at 0 Kg to 1 Kg, and an error of 100 ct is recognized at 1 Kg to 10 Kg.

Then, a large error occurs in the intermediate weight of the weighing range, and the error recognized to be 1 kg or more becomes 10 times, so that 1 kg in the weighing range.
This means that the standard is practically the strictest for the weighing of articles in the vicinity of 1 kg which does not exceed the limit.

[0008]

As described above, in the conventional electronic scale, the standard is substantially strict for the measured value in that the minimum scale is changed, and the error of the measured value exceeds the standard. There was a problem that it might end up. For example, if a high-precision load cell or the like is used, this problem can be solved, but use of a high-precision load cell or the like causes a problem of cost increase.

Therefore, an object of the present invention is to provide an electronic scale capable of averaging weighing errors over the entire weighing range and reducing the weighing error at a point where the minimum scale is changed at a low cost.

[0010]

According to the present invention, there is provided a balance section for measuring the weight of an article and converting it into voltage data, a digital converting means for converting the voltage data obtained by the balance section into digital data, and a balance. Zero point storage means for storing the value of the digital data converted by the digital conversion means in a state where the articles are not weighed by the section, and the digital conversion means when the articles corresponding to the preset maximum weight value are weighed. Maximum weight value storage means for storing the value of the converted digital data, zero weight storage means and maximum weight from the digital data converted by the digital conversion means by weighing an article corresponding to the weight value whose minimum scale is changed Theory of digital data for weight value in which the minimum scale calculated based on the value of digital data stored by the value storage means is changed Scale change weight value error calculation means for calculating the error by subtracting, and virtual error calculation means for calculating a virtual error of the digital data with respect to the maximum weight value based on the error calculated by the scale change weight value error calculation means. , The value obtained by subtracting the value of the digital data stored by the zero point storage means from the value of the digital data stored by the maximum weight value storage means, and further adding the numerical value of a predetermined percentage of the virtual error, as the span value. Based on the span setting means to be set, the span value set by the span setting means, and the digital data value stored by the zero point storage means, the digital data converted by the digital converting means is converted into a weight value. And a weight value conversion means for controlling the weight value.

[0011]

In the present invention having such a structure, the weight of the article is measured by the balance section and converted into voltage data, and the voltage data is converted into digital data by the digital converting means.

The value of the digital data converted by the digital converting means before the weighing of the article is stored by the zero point storing means, and the maximum weight value storing means stores the article corresponding to the preset maximum weight value. The value of the digital data converted by the digital converting means when being measured is stored.

The scale change weight value error calculating means weighs the article corresponding to the weight value for which the minimum scale is changed, and the digital data converted by the digital converting means is stored in the zero point storing means and the maximum weight value storing means. The error is calculated by subtracting the theoretical value of the digital data with respect to the weight value for changing the minimum scale calculated based on the value of the digital data.

The virtual error calculation means calculates the virtual error of the digital data with respect to the maximum weight value based on the error calculated by the scale change weight value error calculation means, and the span setting means causes the maximum weight value storage means to operate. The value obtained by subtracting the value of the digital data stored by the zero point storage means from the value of the stored digital data and further adding the numerical value of a predetermined percentage of the virtual error is set as the span value.

The weight value converting means converts the digital data obtained by the digital converting means into the weight value based on the span value set by the span setting means and the value of the digital data stored by the zero point storing means. Converted.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 is a CPU (central processing unit) that constitutes the main body of the control unit.
ROM storing program data for processing performed by U
(Read only memory) 2 and RA in which various memory areas used when the CPU 1 performs processing are formed
An M (random access memory) 3 is connected to the CPU 1 via a system bus 4. The RAM3
Further, as shown in FIG. 2, the zero point area 3a as the zero point storage means, the maximum weight value area 3b as the maximum weight value storage means, the switching area 3c, the corrected span area 3d, and the switching count area 3e. , A first rounded-up area 3f and a second rounded-up area 3g are formed.

A keyboard controller 6 for controlling the keyboard 5 and a display controller 8 for controlling the display 7 are also connected to the CPU 1 via the system bus 4.

Further, the weighing section 9 composed of a load cell inputs the voltage data (analog data) output by measuring the weight of the article, and digitally converts it into an A / D (analogue / digital) converter. I / to which digital data (count value) output from 10 is input
An O (input / output) port 11 is also connected to the CPU 1 via the system bus 4.

It should be noted that on the display 7, the weight value of the weighed article is displayed with a small minimum scale below the preset switching weight and is displayed with a large minimum scale above the switching weight. Is becoming
Further, in the switching count area 3e formed in the RAM 3, the set value of the count value for the switching weight is stored, and the first rounding up count area 3 is stored.
In f, the rounded-up value in the smallest significant digit of the count value for the smaller minimum scale is stored, and in the second rounded-up count area 3g, the rounded-up value in the smallest significant digit of the count value for the larger minimum scale is stored. To be done. FIG. 3 shows the flow of the setting process performed by the CPU 1.

First, the counter value obtained from the A / D converter 10 is RA when the article is not placed on the balance section 9.
It is stored in the zero point area 3a formed in M3, and the balance unit 9
In the state where the article (weight) corresponding to the maximum weight (maximum weight) is placed, the count value obtained from the A / D converter 10 is stored in the maximum weight area 3b formed in the RAM 3.

Next, the count value obtained from the A / D converter 10 is stored in the RAM while the article (weight) corresponding to the switching weight whose minimum scale is changed is placed on the balance section 9.
3 is stored in the switching point area 3c formed in 3.

Therefore, the value stored in the zero point area 3a is subtracted from the value stored in the maximum weighing value area 3b, and the value is multiplied by the ratio of the switching weight to the maximum weight to perform zero correction on the switching weight. Calculate the theoretical count value. Therefore, the value stored in the zero point area 3a is subtracted from the count value stored in the switching point area 3c to calculate a zero-corrected actually measured count value for the switching weight, and from this actually measured count value, the theoretical value is calculated. The count value of is subtracted to calculate the weighing error in the switching weight. (Scale change weight value error calculation means) Further, the calculated weighing error is multiplied by the ratio of the maximum weight to the switching weight to calculate a virtual error in the maximum weight. (Virtual error calculation means)

Next, the value stored in the zero point area 3a is subtracted from the value stored in the maximum weight value area 3b, and 50% of the weighing error in the calculated maximum weight is added to calculate the span value. Then, the calculated span value is stored in the corrected span area 3d (span setting means). Then, the span value setting process is ended.

For example, the maximum weighing (maximum weight) 10 Kg,
With a switching weight of 1 kg, a minimum scale of 1 g for 0 to 1 kg
Is displayed and the minimum scale is 10g for 1Kg-10Kg.
In particular, in the case of displaying, the zero point area 3
a and the maximum weight value area 3b are stored in the switching count area 3e, 10000 ct,
The round-up count area 3f is set to 5 ct, and the second round-up count area 3g is set to 50 ct. FIG. 4 shows the flow of the weighing / displaying process performed by the CPU 1 at this time.

In the weighing / displaying process, first, the weight of the article is weighed by the weighing unit 9, and the count value obtained from the A / D converter 10 is taken in through the I / O port. The value 10000 stored in the zero point area 3a from this captured count value
ct is subtracted to perform zero correction, and the count value after this zero correction is divided by the span value stored in the corrected span area 3d, and the zero point area is calculated from the value stored in the maximum weighing value area 3b. Span correction is performed by multiplying the value stored in 3a by 100000ct.

Next, it is determined whether or not the span-corrected count value is greater than or equal to 10000 ct stored in the switching count area 3e, and it is determined whether the weight of the article is greater than or equal to 1 kg.

If the weight of the article is less than 1 kg, divide the span-corrected count value by 10 ct to obtain 1
The first weight conversion for converting to the weight value in g is performed, and it is confirmed whether or not the remainder count value in this division is 5 ct or more, and the remainder count value is 5 ct or more stored in the first round-up area 3f. Only when, the +1 is added to the smallest digit of the weight value obtained by the first weight conversion.

Here, the calculated weight value of 1 g unit is displayed by the first display for displaying 1 g unit by the display device 7, and the process returns to the first process of the weighing / displaying process.

If the weight of the article is 1 kg or more, the span-corrected count value is divided by 100 ct to perform a second weight conversion for converting the weight value into a unit of 10 g, and the remainder count in this division is calculated. It is confirmed whether or not the value is 50 ct or more, and +1 is added to the minimum digit of the weight value obtained by the second weight conversion only when the remaining count value is 50 ct or more stored in the second round-up area 3g. ..

Here, the calculated weight value in units of 10 g is displayed by the second display for displaying in units of 10 g on the display unit 7, and the process returns to the first process of this weighing / displaying process. (Weight value conversion means)

In this embodiment having such a configuration, the voltage data output from the weighing section 9 is digitally displayed in a state where no article is placed on the weighing section 9 and when an article corresponding to the maximum weight is placed. The count values obtained from the A / D converter 10 for conversion are stored in the zero point area 3a and the maximum weighing area 3b, respectively.

An article corresponding to the switching weight whose minimum scale is changed is placed on the balance unit 9 and weighed, and the count value of the A / D converter 10 obtained by the weighing is stored in the switching point area 3c. To be done. From the zero-corrected theoretical count value for the switching weight calculated from the values stored in the zero point area 3a and the maximum weighing area 3b to the switching weight calculated by the count value stored in the switching point area 3c The zero-corrected actual count value is subtracted to calculate the weighing error in the switching weight.

A virtual error at the maximum weight is calculated from the weighing error at the switching weight. And
From the value stored in the maximum weighing area 3b to the zero point area 3
To the value obtained by subtracting the value stored in a (span value for normal maximum weight), 50
Add the percentage to get the span value. This span value is stored in the corrected span area 3d.

In the actual weighing of the articles, the count value obtained by digitally converting the voltage data from the weighing section 9 by the A / D converter is zero-corrected by the value stored in the zero point area 3a. After that, span correction is performed based on the span value stored in the corrected span area 3d. The count value subjected to the span correction is converted into a weight value and displayed.

In FIG. 5, when the maximum weight (maximum weight) is 10 kg and the switching weight is 1 kg, the minimum scale of 1 g is displayed at 0 to 1 kg, and the minimum scale of 10 g is displayed at 1 kg to 10 kg. In the value setting process, the zero point is set to 10,000 ct (count) and the maximum weight is set to 110000 ct, and the zero point area 3a is set.
And a graph of the measurement error characteristic when stored in the maximum weighing area 3b.

The standard at this time is shown by a broken line A, and an assumed standard that is equal for each measured value is shown by a one-dot chain line B. When the conventional zero point setting and maximum weighing value setting are performed and the value obtained by subtracting the zero point setting value from this maximum weighing value setting value is taken as the span value, the graph of the measurement error characteristics is as shown in the curve C. Become. As shown in the conventional example, the measured weight is close to the one-dot chain line B in the vicinity of 1 kg and may exceed the standard. However, the switching weight is actually weighed, the weighing error for the switching weight is calculated, the weighing error for the maximum weight is calculated from the calculated weighing error, and 50% of the weighing error for the maximum weight is calculated. The graph of the measurement error characteristic in this embodiment, which is added to the conventional span value to obtain the span value, is 2
It becomes as shown by the dotted line D.

As described above, in this embodiment, the switching weight in which the minimum scale is actually changed is measured, and the virtual error in the maximum weight is calculated from the weighing error in the switching weight calculated from this measurement. By adding 50% of this virtual error to the conventional span value, the weighing error can be averaged over the entire weighing range as shown in FIG. 5, and the weighing error can be reduced particularly at the point where the minimum scale changes. Moreover, in this embodiment, since the setting of the span value is only improved, the above-mentioned effect can be obtained at low cost.

In this embodiment, the count value stored in the maximum weight setting is subtracted from the count value stored in the zero point setting, and the value obtained by the subtraction is used to calculate the virtual weight at the maximum weight (maximum weight). Although 50% of the error is added as the span value, the present invention is not limited to this. For example, 40% or 60% of the virtual error in the maximum weighing amount may be added.

[0040]

As described in detail above, according to the present invention,
It is possible to provide an electronic balance that can average weighing errors over the entire weighing range, and can reduce weighing errors at a point where the minimum scale changes, at low cost.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of essential parts of an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a RAM of the same embodiment.

FIG. 3 is a diagram showing a flow of span value setting processing of the embodiment.

FIG. 4 is a diagram showing a flow of weighing / display processing of the embodiment.

FIG. 5 is a diagram showing an example of a graph of the measurement error characteristic of the same embodiment.

[Explanation of symbols]

1 ... CPU, 3a ... zero point area, 3b ... maximum weighing area, 3c ... switching point area, 3d ... corrected span area, 7 ... display, 9 ... weighing section, 10 ... A / D converter.

Claims (1)

[Claims] 1. A weighing section for weighing an article and converting it into voltage data, a digital converting means for converting the voltage data obtained by the weighing section into digital data, and the article is weighed by the weighing section. Zero point storing means for storing the value of the digital data converted by the digital converting means in the absence state, and digital data converted by the digital converting means when weighing an article corresponding to a preset maximum weight value. Maximum weight value storage means for storing the value of, and the zero point storage means and the maximum weight value storage from the digital data converted by the digital conversion means by weighing an article corresponding to the weight value whose minimum scale is changed. The theoretical value of the digital data for the weight value at which the minimum scale calculated based on the value of the digital data stored by the means is changed Scale change weight value error calculation means for subtracting and calculating an error, and virtual error calculation means for calculating a virtual error of digital data with respect to the maximum weight value based on the error calculated by the scale change weight value error calculation means. , A value obtained by subtracting the value of the digital data stored by the zero point storage means from the value of the digital data stored by the maximum weight value storage means, and further adding a numerical value of a predetermined percentage of the virtual error. Span setting means set as a span value, and digital data obtained by conversion by the digital conversion means based on the span value set by the span setting means and the value of the digital data stored by the zero point storage means. An electronic scale comprising: a weight value conversion means for converting the weight value into a weight value.