JP2001013001A - Electronic weighing apparatus with built-in weight - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reliability in calibration by a built-in weight by providing compatibility between the on-pan load of a weighing pan and a measured value of the built-in weight at each temperature. SOLUTION: When environment temperature at which an electronic weighing apparatus is disposed in changed by a predetermined amount, an external reference weight is placed on a weighing pan 1 at the temperature to calibrate the electronic weighing apparatus. In this state, a built-in weight receiving part 4 is loaded with a built-in weight 5 to obtain the measured value of the built-in weight 5. Temperature data and the measured value of the built-in weight 5 after calibration by the external reference weight at every temperature are stored in memory 15. In the case that calibration by the built-in weight 5 is necessary in measuring the load of an object to be weighed, the built-in weight receiving part 4 is loaded with the built-in weight 5 and temperature is measured by a temperature sensor 18 to perform calibration by the built-in weight 5 by the measured value of the built-in weight 5 stored in the memory 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic balance having a built-in weight for calibration, and more particularly to a method for calibrating the built-in weight with respect to a change in a physical quantity of an environment in which the electronic balance is placed, such as a temperature change. The present invention relates to an electronic balance that is properly performed.

[0002]

2. Description of the Related Art In an electronic balance having high weighing accuracy, such as an electromagnetic balance type electronic balance, in order to maintain the accuracy, a weighing device has a built-in calibration weight, and the built-in weight is added to and removed from a load measuring mechanism. In many cases, a built-in weight adding / removing mechanism is provided, and the apparatus user performs calibration using the built-in weight as appropriate or automatically according to a fixed amount of temperature change.

In an electronic balance having the above-mentioned built-in weight, an external reference weight whose exact mass is known is placed on a weighing pan, calibration is first performed in this state, and the built-in weight is set by a calibrated weighing device. There has been proposed a weighing device configured to load a weight onto a load measuring mechanism, measure the weight, and store the measured value. According to this device, the internal weight is weighed in a state where it has been calibrated in advance with the external reference weight, and thereafter the internal weight is calibrated based on the weighed value. It is no longer necessary to accurately adjust the mass to a constant value, and it is possible to use a built-in weight for coarse adjustment, which is advantageous in terms of cost.

[0004]

FIG. 7 shows an example of the configuration of an electromagnetic balance type electronic balance (electronic balance) having a built-in weight. As is well known, in an electronic balance, the load of a weighing object loaded on the weighing pan 1 is transmitted to the electromagnetic unit 3 via a load transmission mechanism applying the principle of leverage, and tends to be displaced with the load of the weighing object. The load of the weighed object is calculated from the amount of electricity output to the feedback circuit that generates a force that balances the electromagnetic unit with the weighing object.

On the other hand, the built-in weight 5 is placed on the built-in weight receiving section 4 different from the weighing pan 1 by a built-in weight adding and removing mechanism (not shown). Since the built-in weight receiver 4 is connected to the load transmitting mechanism 2 via a link mechanism,
The load of the internal weight 5 applied to the internal weight receiving section 4 is transmitted to the electromagnetic section 3. On the other hand, the external reference weight is naturally placed on the weighing dish 1. That is, the load transmission path of the external reference weight and the load transmission path of the built-in weight are not the same, and this causes the reliability of the calibration using the built-in weight to decrease in practical use of the electronic balance.

For example, a mechanism for transmitting a load from the weighing pan 1 to the electromagnetic unit 3 and a change in the internal weight receiving unit 4 to the electromagnetic unit 3 due to changes in physical quantities such as temperature, humidity, and atmospheric pressure inside and outside the electronic balance.
The transmission mechanism of the load that reaches is changed according to the configuration of each mechanism. If this is described as a physical quantity as temperature and the change is taken as an example of the coefficient of linear expansion of each member, the members constituting the load transmitting mechanism, and the load transmitting mechanism constituted by a combination of different configurations of these members, respectively, Each has a unique coefficient of linear expansion with respect to a change in temperature. In other words, the load transmission path from the weighing pan 1 to the electromagnetic unit 3 and the load transmission path from the built-in weight receiving unit 4 to the electromagnetic unit 3 show their own linear expansion coefficients with temperature changes. The compatibility between the value and the measured value of the internal weight is established only at the temperature when the external reference weight is loaded, and there is no compatibility at other temperatures. That is, even if the calibration is performed using the external reference weight and the measured value of the internal weight is stored, the reliability of the calibration using the internal weight cannot be obtained except at a temperature other than the temperature using the external reference weight. Means As described above, the temperature change is taken as an example. For the wear, oxidation and the like of the internal weight, time is also a parameter in addition to the change in the physical quantity such as the temperature and humidity.

FIG. 8 shows a configuration in which the difference between the load applied to the external reference weight and the load applied to the internal weight 5 is minimized. That is, the built-in weight 5 applies the load placed on the weighing pan 1 to the electromagnetic unit 3.
In the middle of the mechanism for transmitting the load to the position where the load is applied. With this configuration, the compatibility between the load of the external reference weight and the load of the internal weight is almost achieved. However, in this configuration, the built-in weight 5 needs to be placed directly below the weighing pan 1, and it is difficult to incorporate the built-in weight adding / removing mechanism, and the entire weighing device must be of a thick type that goes against the demands of the times. Absent. In addition, since the built-in weight adding and removing mechanism is generally more complicated than the configuration shown in FIG. 6, the reliability of the mechanism tends to decrease.

Further, in a large-scale electronic weigher such as a weigher of 300 kg, for example, in order to set a large leverage ratio, a lever 6 having a weighing dish 1 at one end as shown in FIG. A multi-lever configuration, such as the connecting lever 7, is employed. The built-in weight 5 is configured, for example, to be loaded on the lever 7 side. In this configuration, similarly to the configuration of FIG. 7, the transmission path of the load applied to the weighing pan 1 is different from the transmission path of the load of the internal weight 5, and the same problem as described above occurs. In this configuration, the weighing dish 1
If an internal weight is to be placed immediately below the internal weight, an internal weight having an extremely large mass close to the weighing of the electronic balance is required.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and is an electronic balance having a built-in weight, and a transmission path of a load applied to a weighing pan and a built-in weight. An electronic balance configured so that at least a part of the load transmission path is different, wherein even if there is a change in physical quantity such as a change in temperature or a change over time, an electronic balance configured to perform calibration with the built-in weight properly. It is.

That is, the electronic balance according to the present invention is provided with a means for measuring a change in a physical quantity such as temperature, and the load measuring mechanism is calibrated by an external reference weight for each preset change. An electronic balance having a built-in weight that measures and stores the value of the built-in weight by a measuring mechanism, and thereafter performs calibration using the built-in weight based on the stored value of the built-in weight. A sensor for measuring, means for operating the built-in weight adding / removing mechanism when the amount of change in the physical quantity becomes a predetermined value, means for storing the measured value of the physical quantity and the measured value of the built-in weight at this time, Means for calculating and storing the correlation between the measured value of the internal weight and the measured value of the internal weight. After the correlation between the measured value of the internal weight and each measured value of the physical quantity is determined, calibration using the internal weight is performed. Sometimes, to give the internal mass weighing by using the correlation with the measured value of the physical quantity at the time of the calibration, which is an electronic weigher configured to perform calibration of the load measuring mechanism by using this value.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A sensor for measuring a physical quantity (hereinafter, temperature is taken as an example) in an environment where an electronic balance is arranged is arranged, and if a change in temperature changes by a predetermined amount, for example, 2 ° C. At that temperature, the electronic balance is calibrated with an external reference weight. When the calibration using the external reference weight is completed, the built-in weight is loaded on the built-in weight receiving section to obtain a measured value of the built-in weight, and the measured value is stored in association with the measured temperature.

The above operation is performed for each temperature, and the measured value of the built-in weight in a state where the calibration is performed with the external reference weight at each temperature is stored. In measuring the load of the weighed object, first, the temperature is measured at the time of the measurement, and it is determined whether or not this temperature has already been calibrated with the external reference weight. If the temperature has been calibrated with an external reference weight, the load measurement mode is entered.

On the other hand, if the measured temperature is not the temperature calibrated by the external reference weight, a calibration mode using the external reference weight is entered, and the calibration of the internal weight is performed with the calibration performed using the external reference weight as described above. Obtain a value and store this metric with the measured temperature. In addition, since the calibration with the external reference weight is basically not performed again at the specific temperature after the calibration at the specific temperature is completed,
As the calibration data for each temperature using the external reference weight is stored and accumulated, the operation of entering the calibration mode using the external reference weight does not occur.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 shows an electronic balance according to the present invention, and the structure as a mechanism is the same as that of a conventional electronic balance having a built-in weight. In the weighing mode for measuring the load of the weighed object, the same operation as that of the conventional device is performed. That is, the weighing object load applied to the weighing pan 1 is analog-outputted as load data via a load sensor unit 10 such as an electromagnetic unit or a load cell, and is subjected to A / D conversion by the A / D conversion unit 11 for calculation and calculation. The processing unit 12 calculates the weighed value of the weighed object and displays it on the display 13.

On the other hand, the calibration operation using the built-in weight 5 is also performed automatically by the user of the electronic balance through an external input means such as the key switch section 14 or automatically by a constant temperature change, etc. The setting can be the same as that of the conventional device. That is, the present invention is not at the timing of calibration with the built-in weight, but at the point of improving the reliability of calibration at the time of calibration with the built-in weight.

Reference numeral 18 denotes a temperature sensor for detecting a temperature as a physical quantity in an environment where the electronic balance is arranged. The temperature data output from the temperature sensor 18 is calculated via a temperature A / D converter 20 by the above-mentioned arithmetic operation. And a digital output to the processing unit 12. In the illustrated configuration, a physical quantity is a temperature, and a temperature sensor 18 for measuring the temperature is provided. However, instead of or in addition to the temperature sensor 18, a sensor for measuring another physical quantity such as a humidity sensor or an atmospheric pressure sensor is provided. May be provided. Reference numeral 16 denotes a motor drive circuit, and 17 denotes a built-in weight adding and removing mechanism. In general, an electronic balance is provided with a function of correcting sensitivity based on temperature data. Therefore, when a temperature sensor is provided in advance for sensitivity correction, the temperature data of the temperature sensor is used. Therefore, it is not necessary to separately provide a temperature sensor.

Next, FIG. 2 shows the result of an examination of the relationship between the temperature forming the basis of the present invention and the measured value of the internal weight. As shown in FIG. 1, the electronic balance used for the test has a configuration in which the load of the built-in weight 5 is output to the load sensor unit 10 via a different path from the load applied to the weighing pan 1. It is a balance. In the room where the electronic balance is arranged, as shown in the diagram on the left side of the figure, the temperature is about 12 between 9 am and 6 pm, which is the use time period of the electronic balance.
C. to about 25.degree. The result of weighing the load of the internal weight every time the temperature changes by, for example, 2 ° C. is the right diagram. In this diagram, the temperature is 1
The weight value of the internal weight at 2 ° C. was 99.99999 g and 100.0001 g at 25 ° C.

The change in the measured value of the built-in weight with respect to the temperature change is considered to be caused by slight expansion and contraction (positive and negative linear expansion) of the transmission path of the load of the built-in weight. The change in the weighing value is different from the change in the weighing value of the load applied to the weighing pan 1 (load on the pan), and therefore, corresponds to the change in the weighing value of the internal weight corresponding to the predetermined temperature change and the predetermined temperature change. There is no compatibility with the change in load on the dish. The term `` compatibility '' hereafter means that the same weight is applied to the weighing pan and to the built-in weight receiver, no matter how the temperature changes, the same under the same temperature It is used as a word that means that there is a relation to output a weighing value.

Next, an example of an operation state of the electronic balance of the present embodiment will be described mainly with reference to FIGS. First, the flow shown in FIG. 3 is based on the premise that the electronic balance uses a device that is infrequently used or that is unused after purchase. In addition, temperature is set as the measurement target as a physical quantity to be measured in the environment where the electronic balance is arranged.

When the electronic balance is operated, first, the temperature sensor 1
8 measures the temperature T ₁ of (S1), the temperature T ₁ is judged already whether the temperature has been completed the calibration of the electronic balance using an external calibration weight (S2). The measured temperatures T ₁ , T ₂
... is, for example, 16 ° C, 18 ° C, 20 ° C, etc. 2 ° C
It is set in advance to check each time. If the measured temperature T ₁ has already been calibrated by the external reference weight and the measured value of the internal weight of the temperature T ₁ is stored, the temperature T ₁ is set as the measured temperature Ta (S11), The weighing mode for weighing the weighed object is entered.

On the other hand, if the measured temperature T ₁ is a temperature at which the calibration with the external reference weight has not been completed, a warning (S
Issue 3) to notify that the electronic balance enters the calibration mode using the external reference weight, that is, that normal weighing of the weighing object cannot be performed. Incidentally, in the case of an electronic balance that has not been used at all, since the calibration using the external reference weight has not been performed at all, this warning is always issued. When the external reference weight calibration mode (S4) is entered, an external reference weight having a mass of, for example, 100,000 g is loaded on the weighing dish of the electronic balance (S5). In this state, the electronic balance is calibrated with the external reference weight. Perform (S6).

When the calibration using the external reference weight is completed, the built-in weight adding / removing mechanism 7 is operated to load the built-in weight 5 into the built-in weight receiving section 4 (S7), and the built-in weight 5 is weighed. The measured value W1 of _No. 5 is stored in the memory 15 (S8). At this stage, the temperature T ₂ is measured again by the temperature sensor 18 (S9 / FIG. 4), and whether the temperature T ₂ has changed from the measured temperature T ₁ by a predetermined temperature change amount TS (for example, 2 ° C.) or more. It is determined whether or not it is (S10). For example, there is a case where the measured temperature T ₁ is 18 ° C. and the measured temperature T ₂ is 20 ° C. In this case, return to if the set value changes TS above step (S2), to determine the necessity of calibration by external calibration weight on the basis of the temperature T _2, the external reference weight by the steps described above, if necessary Calibration by weighing and weighing the internal weight.

The above steps are repeated for each of the different measured temperatures to calibrate with the external reference weight corresponding to each of the measured temperatures T _{1 to} T _n , and to carry out the calibration of the internal weight corresponding to the temperatures T _{1 to} T _n . to store the weighing value W ₁ ~W _n (S1
2). Since the storage of the weight value of this built-in weight only requires one calibration of the external reference weight for each temperature,
As the usage time of the electronic balance increases, the situation of entering the calibration mode using the external reference weight rapidly decreases, and once the storage value of the internal weight at each temperature has been stored, the calibration mode using the external reference weight will not be entered. Thereafter, proper calibration can be performed in the calibration mode using the internal weight as described later.

Next, a normal load measuring mode is entered (S1).
3). At this time, the temperature Ta is measured by the temperature sensor 18 (S14), and it is determined again whether the measured temperature Ta has already been calibrated by the external reference weight (S15). This is because if the measured temperature changes significantly in the normal load measurement mode, the calibration may be performed with the internal weight even though the calibration with the external reference weight has not been performed on the measured temperature. is there. For example, in summer, an electronic scale was used in a cooled environment until now, but for some reason cooling was stopped, the room temperature was measured by the temperature sensor 18, and the temperature was calibrated with an external reference weight. It is possible that the temperature exceeds the maximum temperature. Therefore, if the step shown in S15 is provided for the measured temperature Ta in the normal load weighing mode, it is warned that the calibration using the external reference weight at the measured temperature Ta is not completed (S3), and the apparatus is warned. Reliability can be further improved.

Further, when the measured temperature Ta is the temperature at which the calibration with the external reference weight has been completed, the amount of change of the measured temperature Ta with respect to the previous measured temperature T (a-1) is a predetermined value TS. (For example, 2 ° C.) is determined (S16 / FIG. 5). If not, the weighed object is placed on the weighing pan 1, weighed (S24), and the weighed result is displayed. (S25).

On the other hand, if the variation of the measured temperature Ta exceeds a predetermined value TS, a warning is issued (S17).
The operation enters the built-in weight calibration mode (S18). In this state, the internal weight adding / removing mechanism 17 operates via the motor drive circuit 16 to load the internal weight 5 into the internal weight receiving portion 14 (S1).
9) The electronic balance is calibrated with the built-in weight 5. From this, the measured value Wa 'of the internal weight 5 is obtained (S20). Next, the weighing value Wa of the internal weight 5 corresponding to the measured temperature Ta stored in the memory 15 is selected (S21), and the electronic balance is calibrated based on the selected weighing value Wa. Thus, the calibration using the built-in weight 5 having a different load transmission path can be performed with the built-in weight 5 having compatibility with the load on the plate at the temperature Ta. After the calibration (S23), the weighing object is placed on the weighing dish 1 and weighed (S24, S2).
5). Since the calibration of the external reference weight in a wider temperature range is completed each time the electronic balance is used, after the electronic balance has been used for a certain period of time, in most cases (S1), the normal load measurement mode (S13) is directly started. From step S25), only this load weighing mode is operated, and the trouble of placing the external reference weight is eliminated.

FIG. 6 shows another operation state. When the electronic balance is operated, first, the temperature sensor 18 measures the temperature Tx (SA1). The temperature Tx is either the temperature T ₁ through T _n, it is determined whether the temperature Tx is a temperature which has already completed the calibration of the electronic balance using an external calibration weight (SA
2) If the temperature is already measured, the above-mentioned load weighing mode is entered and the weighed value is displayed (SA10).

On the other hand, if the temperature has not been calibrated, a warning is issued (SA3), and the electronic balance enters the calibration mode using the external reference weight, that is, the built-in weight is used in the normal weighing operation. Warns that correct weighing is not displayed even after calibration. Depending on the usage conditions of the electronic balance, it may be desired to ignore the warning and obtain the weighed value.Therefore, when the warning is issued, the user of the electronic balance determines whether the electronic balance enters the calibration mode using the external reference weight according to the warning. Is determined (SA4).

Calibration mode with external reference weight (SA5)
Once it has entered, for example, 100.00
An external reference weight having a mass of 00 g is loaded (SA
6) In this state, the load weighing mechanism of the electronic balance is calibrated (SA7). When the calibration is completed, the built-in weight is loaded on the load measuring mechanism (SA8), the built-in weight is measured, and the built-in weight value Wx (x = 1 to n) at the temperature Tx is stored. When the external reference weight calibration mode ends, the electronic balance returns to the normal weighing mode and displays the weighing value (S
A10).

In each of the above embodiments, the temperature was described as an example of the physical quantity around the electronic scale. However, instead of or in addition to the temperature, other physical quantities such as humidity and atmospheric pressure are measured, or wear and oxidation are performed. In consideration of the above, time may be inserted as a calibration parameter. However, since it is difficult to obtain an appropriate calibration timing only by a change over time, it is used together with the change in the physical quantity, and after the completion of the acquisition of the calibration data corresponding to the change in the physical quantity, a warning is issued, for example, every month. Command the calibration using the external reference weight, and make sure that the temperature at the time of calibration with the external reference weight and the weight value of the internal weight at this temperature after calibration match the weight value of the internal weight at the same temperature in the previous calibration. To determine if they are If they do not match, the compatibility between the load transmission system on the weighing pan and the load transmission system on the built-in weight may be lost due to wear, oxidation, etc., for example, calibration with an external reference weight at each temperature Is performed again to cope with the change with time, and the reliability of the calibration using the internal weight is maintained.

In both cases where the time as a calibration parameter is included and when it is not included, if the relationship between the physical quantity around the electronic balance and the measured value of the built-in weight is obtained in advance, this relationship is obtained. By correcting the measured value of the internal weight as a correction value using the value that holds, it is expected that proper calibration can be performed without actually using an external reference weight.

[0032]

According to the present invention, as described in the above embodiment, the electronic balance is calibrated with an external reference weight in response to a change in a physical quantity such as temperature, and the measured value of the internal weight is stored together with the physical quantity. Therefore, when performing calibration using the internal weight, the compatibility of each load transmission path is maintained even if the load transmission path of the internal weight is different from the load transmission path of the weighing pan. Calibration for the upper load can be performed accurately.

Further, since there is no need to dispose the built-in weight directly below the weighing pan, the degree of freedom in designing the built-in weight adding / removing mechanism is high, and the entire electronic balance can be formed into a thin and small one corresponding to the needs of the times. Even with a load transmitting mechanism having a plurality of levers, proper calibration can be performed with a built-in weight having a small mass relative to weighing.

[Brief description of the drawings]

FIG. 1 is a block diagram of an electronic balance showing a configuration example of the present invention.

FIG. 2 is a diagram showing a relationship between a temperature change and a change in a built-in weight value.

FIG. 3 is a part of a flowchart showing an example of an operation state of the electronic balance of the present invention.

FIG. 4 is a part of a flowchart continuing from FIG. 3;

FIG. 5 is a part of a flowchart continuing from FIG. 4;

FIG. 6 is a flowchart showing another example of the operation state of the electronic balance of the present invention.

FIG. 7 is a schematic view of an electronic balance having a configuration in which a load transmission path from a weighing pan and a load transmission path from a built-in weight receiving portion are different.

FIG. 8 is a schematic diagram of an electronic balance having a configuration in which a load transmission path from a weighing dish and a load transmission path from a built-in weight receiving portion are substantially equal.

FIG. 9 is a schematic view of an electronic balance in which a load transmission mechanism is a double lever.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Weighing pan 2 Load transmission mechanism 3 Electromagnetic part 4 Built-in weight receiving part 5 Built-in weight 16 Motor drive circuit 17 Built-in weight adding and removing mechanism

Claims (5)

[Claims] An internal weight and an internal weight adding / removing mechanism for adding or removing the internal weight to / from a load measuring mechanism are provided, the load measuring mechanism is calibrated by an external reference weight, and the internal weight is calibrated by the calibrated load measuring mechanism. In an electronic balance with a built-in weight that is measured and stored, and then the calibration with the built-in weight is performed based on the measured value of the stored built-in weight, changes in physical quantities such as temperature in the environment where the electronic scale is placed And a means for determining whether the physical quantity measured by the sensor is a temperature at which calibration using an external reference weight is performed, and after calibration using an external reference weight at a predetermined physical quantity. Means for storing the measured value of the measured internal weight together with the measured physical quantity, so that when calibrating with the internal weight, only the measurement after calibration with the external reference weight is performed. An electronic balance having a built-in weight, wherein the load measuring mechanism is calibrated by the built-in weight using a value corresponding to the measured value of the physical quantity among the stored measured values of the built-in weight. 2. A built-in weight adding and removing mechanism for automatically adding and removing the built-in weight to and from the load measuring mechanism, and activating the built-in weight adding and removing mechanism when the measured change in the physical quantity becomes a predetermined value. The built-in weight is configured to be calibrated, and when it is determined that calibration using the built-in weight is necessary based on the measured physical quantity, the built-in weight is automatically loaded on the load measuring mechanism to perform the calibration. An electronic balance having a built-in weight according to claim 1. 3. A physical quantity such as temperature is measured when weighing a load on a weighing object placed on a weighing pan, and the value of the physical quantity is already calibrated by an external reference weight and the measured value of the built-in weight after the calibration. 3. An electronic balance having a built-in weight according to claim 1, further comprising means for judging whether or not the value is a value when stored. 4. A means for measuring time is provided in addition to the means for measuring the physical quantity, and a command is issued to perform the calibration with the external reference weight again after a lapse of a fixed time since the last time when the measured value of the internal weight is stored. Is provided, and a means for storing the measured value of the internal weight when the internal weight is loaded after calibration using the external reference weight according to the command, and the measured value of the physical quantity at the time of measuring the internal weight, and Means for comparing the measured value of the built-in weight corresponding to the measured physical quantity with the measured value of the built-in weight measured after the previous calibration using the external reference weight under the same measured physical quantity as the measured physical quantity. When the previous internal weight value and the current internal weight value under the same physical quantity are different from each other by a predetermined value or more, the internal weight value corresponding to the physical quantity is used as the internal weight value. 4. The method according to claim 1, wherein by adopting the current measured value, the compatibility between the load transmitting mechanism from the weighing pan and the load transmitting mechanism of the built-in weight is maintained again. Electronic balance with built-in weight. 5. The electronic balance according to claim 1, wherein the physical quantity of the measurement target is a temperature.