JPH0749991B2 - Electronic balance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an electronic balance.

<Prior art> Generally, in electronic balances, in order to stabilize the weighing display value against a disturbance such as vibration, it is performed to average a large number of load data from the load detecting unit to obtain a weighing value. ing. The number of times of averaging or the time for averaging data to be used for averaging (average time) is usually configured so that it can be selected according to the magnitude of disturbance in the installation environment, required measurement accuracy, and the like. It is needless to say that the installation environment should be in a place where there is as little disturbance as possible, such as vibration, and the less disturbance there is, the more accurate the measured value is in the state where the averaged number is reduced and the response is improved. Can be obtained.

<Problems to be solved by the invention> From the above, when installing an electronic balance, it is first necessary to determine which place is the most suitable place with the least disturbance such as vibration. Conventionally, humans often make their decisions by relying on intuition based on the feeling of touch.
However, even if it is not felt by humans, there is a degree of disturbance that affects a high-precision electronic balance, and thus the conventional method for determining the installation location as described above has a great problem.

In addition, next, in terms of how much the data averaging number or averaging time should be set at the installation location to obtain the desired accuracy of the measured value, it is virtually dependent on human intuition. Many. Furthermore, the disturbance situation in the place where it is once installed is not always constant, and from these points, it is possible to obtain a measured value with the accuracy required conventionally in the shortest measurement time. It is often hard to say that a balance is used.

The present invention has been made in view of the above, detects the degree of disturbance in the installation environment, from the input accuracy and the degree of the disturbance, to obtain a weighing value that satisfies the accuracy in the installation location The purpose of the present invention is to provide an electronic balance capable of obtaining and displaying an optimum averaged number.

<Means for Solving Problems> The configuration of the present invention will be described based on the functional block diagram shown in FIG.

The load detection unit a generates an electric signal corresponding to the mounting load,
The digital conversion data is supplied to the average value calculating means b at predetermined time intervals. The average value calculation means b determines the metric value by averaging the data based on the selected average number. The measured value is displayed by the measured value display means c. With respect to the digital conversion data from the load detection unit a, the data variation calculation means d also calculates the magnitude of the variation in the preset number. The calculated magnitude of the variation is supplied to the optimum averaged number calculating means e.

On the other hand, the accuracy required for the measured value is input by the accuracy input means f, and the input value is also supplied to the optimum averaged number calculation means e. In the optimum averaged number calculation means e,
The optimum value of the average number of data by the average value calculating means b is calculated from the input value of the accuracy and the value calculated by the data variation calculating means d. The calculated optimum averaged number is displayed together with the precision input by the precision input unit f and the precision / optimal averaged number display unit g.

<Operation> In a state where the load placed on the load detection unit a does not change,
The variation of the load data from the load detection unit 1 is in correlation with the magnitude of the disturbance acting on the electronic balance. Therefore, from the magnitude of the variation and the required accuracy of the measured value, the accuracy can be determined at the installation location. The minimum necessary for obtaining the metric value to satisfy, that is, the optimum number of data averaged can be statistically calculated. If this calculation result is displayed together with the required accuracy that has been input, the balance user is informed of the minimum number of averaged data required to satisfy the required accuracy. By setting the averaged number according to the displayed contents, the balance user can use the balance in the optimum condition to meet the required accuracy at the installation location, and at the same time input the same required accuracy. Just by installing a balance at a place, the magnitude of the disturbance at each place can be quantitatively grasped from the displayed contents, and it becomes possible to easily select the optimum place for installation.

<Example> An example of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram showing the configuration of the embodiment of the present invention.

The load detection unit 1 outputs an electric signal corresponding to the load placed on the dish 1a, and its digital conversion data is taken into the control unit 2 at every predetermined minute time. The control unit 2 is composed of a microcomputer, and executes a CPU 21 for executing various calculations and programs and controlling each peripheral device, a ROM 22 in which a measurement program and an optimum averaged number calculation program described later are written, and a load detection unit 1 A RAM 23 having an area for storing digital converted data and an area for storing various calculation results, an input / output port 24 for connecting to an external device, and the like are provided, and these are connected to each other by a bus line.

At the input / output port 24 of the control unit 2, in addition to the load detection unit 1, a key switch 3 for giving a command to the control unit 2 and a display for digitally displaying a measured value and the like according to a command from the control unit 2. 4 is connected.

As shown in FIG. 3, a front view of the display unit 4 includes a weighing value display section 4a for displaying weighing values, an optimum averaging number n calculated by an optimum averaging number calculation program described later, a standard deviation σ, A condition data display unit 4b for displaying the input accuracy p, the set average number n ', etc. is provided.

Next, the operation will be described. The measurement program is executed in the normal measurement mode. In this measurement program, RA
Of the data from the load detector 1 stored in M23, the latest value of the averaged number n'selected by the key switch 3 is averaged to determine the weight value of the load on the plate 1a. And display it on the display unit 4.

Now, when the optimum averaged number calculation mode is selected by the key switch 3, the optimum averaged number calculation program as shown in the flowchart of FIG. 4 is executed.

In the optimum averaged number calculation program, first, it is determined whether or not the data from the load detection unit 1 is changing. This is because the step response of the output of the load detection unit 1 due to the loading and unloading of the load on the plate 1a is not contained. During the data change, the standard deviation σ described later has a correlation with the magnitude of the disturbance. Since it is not, the step response is completely settled, and the data becomes stable, and the process proceeds to the next step. This determination can be performed using a known stability determination method. For example, when the value of each piece of data is within a predetermined width with respect to the average value of a predetermined number of data, the data is stable. It can be determined that there is a state.

In the data stable state, preset N pieces of data are taken in from the data group from the load detection unit 1 stored in the RAM 23, and the standard deviation σ of the N pieces of data is calculated. Since the variation of the data in the stable state of the data is considered to be caused by the disturbance acting on the electronic balance, the standard deviation σ thereof represents the magnitude of the disturbance at the installation place.

Next, when the precision p required for the measured value is input from the key switch 3, the optimum averaged number n is calculated from the value p and the standard deviation σ described above by the following equation (1).

That is, the standard deviation σ based on the above N data and n
The following equation (2) holds true with the standard deviation σ of the average value of the data.

Therefore, the required confidence level of the precision p, for example, the value at 95.4% is p = 2σ (3). From these (2) and (3), the averaged number of data to achieve the accuracy p at the confidence level of 95.4%, in other words, the minimum data that can achieve the accuracy p under the confidence level of 95.4%. The averaged number, that is, the optimal averaged number is
It can be obtained by the equation (1).

For example, if the precision p is 1 mg and the standard deviation σ is 1.9 mg, then n = 14.4 is obtained from the equation (1). And
This n is displayed on the display 4 together with σ and p.

The average number n'is set by the key switch 3 based on the value of n obtained as described above. If the selectable average number is, for example, 4,8,16,32 ... 16 which is the closest to the average number of 14.4 and is larger than that value
By selecting, the measurement value accuracy of 1 mg is guaranteed at a confidence level of 95.4% or higher.

It is preferable that the averaged number n'set in this way and the inputted precision p are held by backup or the like even when the power is turned off.

According to the embodiments of the present invention described above, first, when determining the installation location of the electronic balance, the electronic balance is installed at each of the plurality of candidate locations, and the standard deviation σ at each location or its σ By comparing the optimum averaged number n having a correlation with the input accuracy p in, it is possible to find the optimum installation location with the smallest disturbance. That is, the optimum average number n is directly proportional to the square of the standard deviation σ if the input required accuracy p is constant, as is clear from the above formula (1), and
Since the standard deviation σ is proportional to the magnitude of the disturbance at the place where the balance is installed, the balance is placed at each candidate position with the required accuracy p kept constant, and the optimum average number n at each place is compared. By finding the place where the value n is the smallest, the place where the disturbance is the smallest can be found. Then, by setting the averaging number n ′ based on the optimum averaging number n at that location, the desired accuracy p
It is possible to obtain the measured value of with good responsiveness in a short time.

In the above embodiment, the standard deviation σ is displayed together with the optimum averaged number n, but as described above, as long as the input precision p is the same, that is, the display value of p is As long as it is constant, the display of the optimum averaged number n is a parameter that quantitatively represents the magnitude of the disturbance at the installation location, and thus the display of the standard deviation σ is not always necessary.

Further, the optimum averaged number calculation program in the above embodiment can be configured to be executed, for example, every time the power is turned on, and the averaged number n can be detected by detecting a change in the disturbance situation at this place or installation place. ′ Can be used for resetting, etc.

<Effect> As described above, according to the present invention, the magnitude of variation in N pieces of digital conversion data from the load detection unit 1 is calculated, and from the value and the input weighing value accuracy p,
The optimum average number n is calculated, and the calculation result n
Is displayed together with the input weighing precision p,
By these indications, without relying on intuition as in the past,
It is possible to determine an appropriate installation location according to quantitative information, and to set an optimum averaged number to obtain a measurement value that satisfies the accuracy p at that installation location. It has become possible to use electronic balances.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing the configuration of the present invention, FIG. 2 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 3 is a front view of its display unit 4, and FIG. 7 is a flowchart showing an optimum averaged number calculation program written in a ROM 22. 1 ... Load detection unit 2 ... Control unit 21 ... CPU 22 ... ROM 23 ... RAM 24 ... Input / output port 3 ... Key switch 4 ... Display 4a ... Weighing value display 4b ... Condition data display

Claims (1)

[Claims] 1. A weighted value is determined and displayed by sampling digital conversion data from a load detection unit at predetermined time intervals and calculating an average value of the data based on the selected averaged number. In the balance, from the means for calculating the magnitude of the variation of the above-mentioned predetermined number of data, the means for inputting the precision required for the weighing value, and the precision of the input and the magnitude of the variation of the data. An electronic balance comprising means for calculating an optimum averaged number for calculating the average value, and means for displaying the optimum averaged number together with the entered accuracy.