JPH0746060B2 - Electronic balance - Google Patents

Description

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

<Prior art and its problems> Generally, for electronic balances with a small reading limit for the weighing capacity or for electronic balances with a reading limit of 0.01 mg or less, which is absolutely small, place the DUT on the measuring pan. There is a case where the previous zero point does not match the zero point after the object to be measured is unloaded from the measuring dish. In such a case, it is highly possible that the zero point has already drifted at the time when the measured value of the measured object is read, and therefore the measured value includes an error due to zero drift.

An object of the present invention is to provide an electronic balance capable of correcting a measurement value error due to the zero drift as described above and obtaining a more accurate measurement value.

<Means for Solving Problems> A configuration for achieving the above object will be described with reference to the basic conceptual diagram shown in FIG.
In the balance in which the measured value is determined by the measured value determining means b on the basis of the detection data from
A stability determining means d for determining whether or not the data from the load detection unit a is in a stable state, and a _first storing the measured value W ₁ in the data stable state before the object to be measured is placed on the load detection unit a. _Second memory e and _second weight value W ₂ for storing the measured value W ₂ in the data stable state with the object to be measured placed on the load detection unit a
Memory f, a third memory g for storing the measured value W ₃ in the data stable state after the object to be measured is unloaded from the load detection part a, and contents W ₁ and W of the first and third memories.
₃ and the zero point at the time of storing the measured value W ₂ in the second memory f, based on the elapsed time at the time of storing the measured values in the first to third memories e to g, respectively. The present invention is characterized in that it is provided with a calculating means h for correcting the content W ₂ of the second memory, and the measured value W ₂ ′ after the correction by the calculating means h can be displayed on the display c according to a command.

<Operation> The zero point before measurement is stored in the first memory e, and the zero point after measurement is stored in the third memory g. When this zero point changes over time as shown in FIG. 3, the content W ₂ of the second memory f is the actual measured value.
The value includes the error of W ₂ ′ and δ.

The error due to such zero drift is usually changed by the calculating means h as a linear function with the passage of time as shown in FIG. 3, and therefore the error δ contained in W ₂ which is the measured value of the object to be measured. Are the values of W ₁ and W ₂ , and the first to third memories e to
It can be easily estimated from the elapsed time at each time point when W ₁ , W ₂ and W ₃ are stored for g. Therefore, correct W ₂ by that value
W ₂ ′ can be obtained.

<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 is mainly composed of, for example, an electromagnetic force balancing mechanism, and can detect the load on the dish 1a and supply the digital conversion data to the control unit 2 at every predetermined minute time.

The control unit 2 is mainly composed of a microcomputer, and in addition to the CPU 21, the ROM 22, the RAM 23 and the input / output port 24, a display 25 capable of digitally displaying the measured value in response to a command from the CPU 21 is connected. The input / output port 24 of the control unit 2 is connected to a tare key 3 for giving a tare erase command, and a correction command key 4 for giving a command to display a corrected weighing value which will be described later on the display 25.

The RAM 23 will be described later in addition to an area for storing the latest predetermined number of load detection data collected every moment and an area as a tare amount memory for storing the weighing value at the time when the tare key 3 is pressed. Before measurement zero point data W ₁ ,
Weighed value data W ₂ of measured object, zero point data W ₃ and W ₁ after measurement
It has areas as first to fifth registers for storing the time data t ₁ between the sampling time point and the W ₂ sampling time point and the time data t ₂ between the W ₂ sampling time point and the W ₃ sampling time point, respectively. There is.

Each time the load detection data is collected in the ROM22, the latest specified number of load detection data in the RAM23 is averaged, multiplied by the span coefficient, and the tare amount memory content is subtracted from the value to determine the weighing value. Each time the load detection data is collected, the latest n pieces of load detection data are compared with each other, and whether or not they are all within the preset range is written. A stability determination routine for determining the stability of the data is included depending on whether the data is stable or not. Based on this stability determination result, as described later, the data storage timings to the above-mentioned first to fifth registers are given.

In addition to the weighing program, the ROM 22 is activated by pressing the correction command key 4 and corrects and displays the measured value by the correction formula described later using the contents of the first to fifth registers. A calculation program has been written.

Next, a method of storing data in the first to fifth registers and a correction calculation method will be described with reference to FIG. FIG. 3 is a graph showing an example of changes over time of measured values. If it is determined that the data is in a stable state before the object to be measured is placed on the dish 1a, the measured value W ₁ at that time is stored in the first register.
By monitoring the load detection data, the data W ₁ is updated every moment until just before it is determined that the object to be measured is placed on the dish 1a. Next, the time t ₁ from the time when it is determined that the DUT is placed on the dish 1a to the time when it is determined that the data has entered the stable state is measured, and the value is stored in the fourth register. Store. At the same time, the measured value W ₂ at that time is stored in the second register. When it is determined that the data has entered the stable state after the object to be measured is placed, a display permitting is displayed on the display 25, which is publicly known.

This display allows the operator to read the weight value W ₂ and
The object to be measured is lowered from above 1a, but the time t ₂ from when the measured value W ₂ is first stored in the second register to when it is determined that the data has entered the stable state again after the object to be measured is lowered.
Is stored in the fifth register, and the measured value W ₃ at that time is stored in the third register.

In the above process, the display 25 displays W _{1 to} W _{2 to} W ₃ respectively.
Is displayed, but when the correction command key 4 is pressed while W ₃ is displayed, the operation of the following equation (1) is executed using the contents of the first to fifth registers. Result W ₂ ′
Is displayed on the display unit 25.

In equation (1), a (W ₃ -W ₁₎ is a variation of the zero point before and after the measurement, (t ₁ + t ₂₎ is the time elapsed between. Time (t ₁ + t ₂₎ with the passage of (W ₃ -W ₁₎ If the zero point only to have drifted, the change process can be estimated as indicated by the broken line in Figure 3. As a result, the measured value W ₂
The amount of change δ of the zero point with respect to W ₁ at the time of storage of Can be sought by. Therefore, W ₂ ′ obtained by the equation (1) is a metric value closer to the true value, with the zero point drift corrected.

The correction formula in the present invention is not limited to the above formula (1), and the drift can be corrected also by the following formula (3), for example.

That is, assuming that the object to be measured is smoothly placed on and off from the dish 1a, t ₁ ≈t _2. Therefore, if the correction is valid only in this case, the formula (1) can be calculated from the formula (3). The formula can be derived.

Further, in the above embodiment, the correction command key 4 is pressed to calculate and display W ₂ ′. However, the correction command key 4 is not particularly provided, for example, the existing tare key 3 or the like. Can be used also as the correction command key, and the tare erase command or the correction command can be generated by an operation of, for example, less than or equal to a predetermined time. Furthermore, the contents of the first register and the third register
Compare W ₁ and W ₃ and issue an alarm when the difference exceeds a predetermined amount, and at this time voluntarily issue a correction command to execute correction calculation and display the result. It can also be configured.

<Effects of the Invention> As described above, according to the present invention, the zero points before and after the measurement are stored, and these storage time points and the elapsed time at the time point when the measured value of the measured object is stored, Since the amount of change in the zero point when the measured value is obtained is estimated and the command value is used to correct and display the measured value based on the estimated value, the measured object can be displayed on the plate. After lowering, by giving a command as required, it is possible to know the correct weighing value that is not affected by zero drift.
Especially, the effect is great in a high-precision electronic balance having a small reading limit.

[Brief description of drawings]

FIG. 1 is a basic conceptual diagram showing the constitution of the present invention, FIG. 2 is a block diagram showing the constitution of the embodiment of the present invention, and FIG. 3 is an operation explanatory diagram of the embodiment of the present invention. It is a graph which shows an example. 1 …… Load detection unit 1a …… Plate 2 …… Control unit 21 …… CPU 22 …… ROM 23 …… RAM 25 …… Display unit 4 …… Correction command key

Claims (1)

[Claims] 1. A balance determining means for determining whether or not the data from the load detecting section is in a stable state in a balance for determining a measured value based on the detection data from the load detecting section and displaying it on a display. And a first memory for storing the measured value in the data stable state before placing the object to be measured on the load detection unit, and the above-mentioned in the data stable state with the object to be measured placed on the load detection unit. For the second memory for storing the measured value, the third memory for storing the measured value in the stable state of the data after lowering the object to be measured from the load detection unit, and the first to third memories And a calculation unit for correcting the contents of the second memory by estimating the zero point at the time when the measurement value is stored in the second memory, based on the elapsed time at the time when the measurement value is stored respectively. Command Electronic balance, wherein more that the weight value after the correction by said calculation means is configured to display on the display device.