JPH0641881B2 - Electronic balance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to an electronic balance.

<Prior Art> Generally, in an electronic balance, the sensitivity changes depending on the device temperature, particularly in the electromagnetic force balance type electronic balance, depending on the temperature of the magnetic circuit of the electromagnetic force generating mechanism. Therefore, various measures have been taken in ordinary electronic balances so that the change in sensitivity does not become large with respect to the change in ambient temperature.

<Problems to be Solved by the Invention> The above-mentioned measures are effective when the entire balance is affected in a hidden and uniform manner due to a change in ambient temperature, but when the power is turned on, for example, It is not effective for a relatively rapid internal non-uniform temperature change due to local heat generation of an electronic circuit or heat generation of a transformer.

For this reason, the conventional electronic balance, particularly the electronic balance with high resolution, has a problem that the sensitivity is not stable and accurate measurement cannot be performed for one hour or more after the power is turned on. That is, the conventional electronic balance requires warming up for a predetermined time after the power is turned on.

An object of the present invention is to provide an electronic balance that can obtain accurate measurement results immediately after power is turned on.

<Means for Solving Problems> The configuration of the present invention will be described with reference to the basic conceptual diagram shown in FIG. 1. The present invention is based on the detection data from the load detection unit a and determines the measured value. In the balance which calculates the measured value W by the means b and displays it on the display c, a memory d for storing information relating to a temporal change in sensitivity of the load detection unit a after power-on until a preset time elapses. By providing the time measuring means e for measuring the elapsed time after the power is turned on and the correction calculating means f for correcting the measured value W calculated by the measured value determining means b from the measured result and the contents of the memory d. Characterized.

<Operation> The sensitivity of the electronic balance, as shown in FIG. 1, for example, changes with time after power is turned on due to its unique characteristics due to its structure, etc., but this change is stored in the memory d in advance. With this setting, at the time of actual measurement, the measured value W can be corrected and the correct measured value W ′ can be obtained from the elapsed time after the power is turned on by the time measuring means e and the contents of the memory d.

<Examples> Examples 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 is composed of, for example, a balance mechanism including an electromagnetic force generator, and supplies the control unit 2 with digital conversion data corresponding to a current required to generate an electromagnetic force that balances the load on the dish 1a.

The control unit 2 is mainly composed of a microcomputer, and executes a program and controls peripheral devices.
1, a ROM 22 in which a measurement program and a sensitivity information storage program to be described later are written, a RAM 2 having an area for storing a digital data group from the load detection unit 1
3, a nonvolatile RAM 24 for storing sensitivity information, which will be described later, and a key switch 25 for giving a command to the CPU 21. A display device 3 capable of digitally displaying the measured value is connected to the control unit 2.

FIG. 3 is a flow chart showing a sensitivity information storage program written in the ROM 22. This program is started by pressing the key switch 25, and is used at the time of factory shipment or by the user as needed.
In this program, the preset elapsed time t ₁ , t ₂ ... t _n after power-on is stored, and the measured value when a weight of known mass, for example 200.000 g, is placed on the dish 1a, Each time t ₁ , t _2, ... Tn elapses, they are sequentially stored in the nonvolatile RAM 24 as W ₁ , W _2, ... Wn. This data Wi is used as correction data of the weighing value in the measurement program described later as the sensitivity change data with time after the power is turned on.

FIG. 4 is a flow chart showing a measurement program written in the ROM 22. This program is executed during normal measurement. In this program, the detection data d is collected every moment from the load detection unit 1 and stored in the RAM 23,
For example, after averaging the latest predetermined number of data, the weighing value W is determined by a normal process such as multiplying by a span coefficient. After the power is turned on, the preset time tn
If has passed, the measured value is displayed on the display unit 3.
If the elapsed time T after the power is turned on is tn or less, the T is t ₁
If t ₁ or more than t ₁ and t ₂ or less if t ₂ ...
Read the corresponding data Wi in the nonvolatile RAM 24,
The measured value W is corrected by the following formula.

Next, the operation of the embodiment of the present invention will be described based on a specific example.

FIG. 5 is a graph showing an example of the change in sensitivity with time after turning on the power of the electronic balance. In this electronic balance, the sensitivity gradually approaches the steady state after the power is turned on, and the sensitivity change subsides after about 70 minutes. Therefore, in this electronic balance, as shown in the table, for example, as shown in the table, the time t _{1 to} t from ₁ minute to 100 minutes after power-on
200.000 g weight value Wi at n is stored in non-volatile RAM
It is stored in 24.

At the time of actual measurement, this Wi is read according to the elapsed time T until 100 minutes have passed after the power was turned on, and the ratio of this Wi to the true mass of 200.000 g, that is, the ratio of this Wi to the true mass 200 The measured value W is corrected by the ratio with the measured value of 200.000 g when measured with the sensitivity in the steady state. Therefore, the obtained value W'is equivalent to the measured value when measured with the sensitivity in the steady state.

If the power is accidentally turned off after a long time has passed after the power is turned on, the correction calculation may not be executed. For example, by operating a key switch, the correction may not be executed.

Further, it is also possible to correct the change with time of the zero point after the power is turned on, by the procedure and method exactly the same as the above sensitivity correction.

Further, in the above embodiment, an example in which 23 pieces of data Wi are stored in the non-volatile RAM 24 as shown in the above table is shown. However, for example, several pieces of Wi are actually measured and the sensitivity of FIG. Nonvolatile RAM
It may be stored in 24.

Furthermore, the sensitivity information storage program is not always necessary, and for example, the sensitivity change characteristics over time can be measured before shipment from the factory and written in the nonvolatile RAM 24 using a key input device or the like.

<Effects of the Invention> As described above, according to the present invention, the sensitivity change information with time after the power is turned on is stored, and the measured value is obtained by the information and the elapsed time after the power is turned on at the time of actual measurement. Since the correction is performed, the correct measured value can be obtained immediately after the power is turned on, and the warming up time is unnecessary.

[Brief description of drawings]

FIG. 1 is a basic conceptual diagram showing the configuration of the present invention, FIG. 2 is a block diagram showing the configuration of an embodiment of the present invention, and FIG. 3 is its ROM.
FIG. 4 is a flow chart showing a sensitivity information storage program written in 22. FIG. 4 is a flow chart showing a measurement program also written in ROM 22. FIG. 5 is a graph showing an example of sensitivity change with time after turning on the electronic balance. Is. 1 ... Load detection unit, 2 ... Control unit 3 ... Display unit, 21 ... CPU 22 ... ROM, 23 ... RAM 24 ... Nonvolatile RAM 25 ... Key switch

Claims (3)

[Claims] 1. Based on the detection data from the load detector,
In a balance that calculates a measured value by the measured value determination means and displays it on a display, a memory that stores information relating to the change in sensitivity of the load detection unit with time until a preset time elapses after power is turned on. An electronic balance comprising: a time measuring means for measuring an elapsed time after the power is turned on and a correction calculating means for correcting the calculated weight value based on the time measured result and the contents of the memory. 2. A program for writing the transition data into the memory when the information relating to the change in sensitivity with time is the transition data of the actual measured value after the power is turned on, and the load of the specified mass on the balance. The electronic balance according to claim 1, further comprising: 3. The memory stores the information on the change in sensitivity with time and the information on the change in zero point with time, and the correction calculation means also corrects the zero point after the power is turned on. The electronic balance according to claim 1, characterized in that the electronic balance is configured to be operated together.