JPS62228118A - Electronic balance - Google Patents

Abstract

PURPOSE:To measure an accurate weighed value without receiving the effect of zero-drift, by correcting the error of the weighed value on the basis of the estimated change quantity of a zero point at the point of time when the weighed value is obtained. CONSTITUTION:Digital conversion data is sent to a control part 2 at every minute time from a load detection part 1 detecting the load on a tray 1a. In RAM23 of the control part 2, zero point data W1 before measurement, the weighed value data W2 of an article to be measured, zero point data W3 after measurement, the time data t1 between the sampling points of time of the data W1, W2 and the time data t2 between the sampling points of time of the data W2, W3 are stored and displayed on a display device 25. If a correction order key 4 is pushed when the data W3 is displayed, the correction operation program of ROM22 is started and operation is carried out using the contents of first-fifth registers and a weighed value corrected in the drift of the zero point of W2 and near to a true value is displayed on the display device 25.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to electronic balances.

<Conventional technology and its problems> In electronic balances that have a small reading limit relative to their weighing capacity, or an electronic balance that has an absolutely small reading limit of 0.01 mg or less, the object to be measured is generally placed on a measuring pan. The zero point before placing the object on the measuring pan and the zero point after removing the object from the measuring pan may not match. In such a case, there is a high possibility that the zero point has already drifted when the measured value of the object to be measured is read, and therefore, the measured value will include an error due to zero drift.

An object of the present invention is to provide an electronic balance that can correct errors in weighed values due to zero drift as described above and obtain more accurate weighed values.

<Means for Solving the Problems> The configuration for achieving the above object will be explained based on the basic conceptual diagram shown in FIG.
In the balance, the weighing value is determined by the weighing value determining means and displayed on the display C based on the detected data from the
a stability determination means d for determining whether the data from the load detection section a is in a stable state; and a first stability determination means d for storing the weighing value W1 in the data stable state before the object to be measured is placed on the load detection section a. A memory e, a second memory r that stores the measured value W2 in a data stable state with the object to be measured placed on the load detection section a, and a second memory r that stores the measured value W2 in a data stable state with the object to be measured placed on the load detection section a, and rirIffi that stores the data stability after the object to be measured is removed from the detection section a. From the third memo 'Jg that stores the measured value W3 in the state and the contents Wl and W3 of the first and third memories, estimate the zero point at the time when the measured value W2 is stored in the second memory r. The present invention is characterized in that it is provided with a calculation means for correcting the content W2 of the second memory, and is configured such that the measured value w2' corrected by the calculation means 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 W2 of the second memory f becomes a value containing an error of δ from the actual measured value W2'.

Using the calculation means, the value of the zero point at the time when W2 is stored, that is, the value of δ, is estimated from Wl and W3 by interpolation, etc., and by correcting w2 using that value, the correct metric value w2' can be obtained. You can ask for it.

<Example> Embodiments of the present invention will be described below based on the drawings.

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

The load detection IT is mainly composed of, for example, an electromagnetic force balance mechanism, and can detect the load on the dish la and supply the digital conversion data to the control unit 2 at predetermined minute intervals.

The control unit 2 is mainly composed of a microcomputer, and includes a CPU 21 . ROM22. In addition to the RAM 23 and the input/output port 24, a display 25 is connected which can digitally display a weight value according to a command from the CPU 21. Connected to the input/output boat 24 of the control unit 2 are a tare key 3 for issuing a tare deletion command, and a correction command key 4 for issuing a command to display a corrected weighing value on a display 25, which will be described later.

The RAM 23 includes 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, as will be described later. Pre-measurement zero point data Wl, measurement value data of the object to be measured W2, post-measurement zero point data W3, time data tl between W1 sampling time and W2 sampling time, and between W2 sampling time and W3 sampling time. It has areas as first to fifth registers that respectively store time data t2.

RA is stored in the ROM22 every time load detection data is collected.
A weighing program is written that determines a weighing value by averaging the latest specified number of load detection data in M23, multiplying it by a span coefficient, and then subtracting the contents of the tare weight memory from that value. In this method, each time load detection data is collected, the latest n load detection data are compared with each other, and the stability of the data is determined based on whether or not all of these data are within a preset range. Contains routines.

Based on this stability determination result, the timing for storing data in the first to fifth registers is given, as will be described later.

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

Next, a method of storing data in the first to fifth registers and a correction calculation method will be explained with reference to FIG.

FIG. 3 is a graph showing an example of changes in measured values over time. If it is determined that the data is in a stable state before the object to be measured is placed on the plate la, the measured value W+ at that time is stored in the first register. This data W1 is updated every moment by monitoring the load detection data until just before it is determined that the object to be measured is placed on the plate la. Next, measure the time t] from the time when it is determined that the object to be measured is placed on the plate la until the time when it is determined that the data has entered a stable state,
Store that value in the fourth register. At the same time, the measured value W2 at that time is stored in the second register. When it is determined that the data has entered a stable state after the object to be measured is placed, a reading permission indication is displayed on the display 25, and this display is well known.

With this display, the operator reads the weight value W2 and lowers the object to be measured from the pan la, but since the weight value W2 was first stored in the second register, the data becomes stable again after the object to be measured is lowered. The time t2 until it is determined that the state has entered is stored in the fifth register, and the measured value W3 at that time is stored in the third register.

In the above process, the display unit 25 displays W1 to W, respectively.
2 to W3 are displayed, but if you press the correction command key 4 while Wa is displayed, the following tl1 formula calculation is executed using the contents of the first to fifth registers, and the The result W2' is displayed on the display 25.

In this equation (11), (Wa-W+) is the amount of change in the zero point before and after the measurement, and (1++12) is the elapsed time during that time.As the time (tl tl2) passes, (
Assuming that the zero point has drifted by Wa −W+ ), the change process can be estimated as shown by the broken line in FIG. As a result, the amount of change δ of the zero point with respect to wl at the time of storing the measured value W2 can be determined by the interpolation method. Therefore, W2' obtained by equation (1) becomes a metric value closer to the true value, with the drift of the zero point corrected.

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

W2' = W2 (W
a −W+ ) −・−(U) That is,
Assuming that the object to be measured is placed and unloaded onto the plate la smoothly, tl#t2 will be obtained, so if the correction is valid only in this case, equation (3) can be derived from equation (1). I can do it.

Further, in the above embodiment, W2' is calculated and displayed by pressing the correction command key 4, but the correction command key 4 is not particularly provided, and for example, the existing tare key 3 etc. It can also be used as the correction command key, so that a tare erase command or a correction command can be generated by operating the key for less than or more than a predetermined time, for example. Further, the contents W and Wa of the first register and the third register are compared, and when the difference exceeds a predetermined amount, an alarm is generated, and at this time, a correction command is spontaneously issued, It can also be configured to perform correction calculations and display the results.

<Effects of the Invention> As explained above, according to the present invention, the amount of change in the zero point at the time when the measured value is obtained is estimated from the zero point before and after the measurement, and the measured value is corrected by that value. Since it is configured so that it can be displayed, accurate weighing values can always be obtained without being affected by zero drift. especially,
This effect is significant in high-precision electronic balances with small reading limits.

[Brief explanation 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 an explanatory diagram of the operation of the embodiment of the present invention. Figure 2 is a graph showing an example. ■--Load detection section la--Plate 2-Control section 21-CPU 22-ROM 23--RAM 25-Display 4--Correction command key

Claims (1)

[Claims] In a balance that determines a weighing value based on detection data from a load detection section and displays it on a display, a stability determination means for determining whether the data from the load detection section is in a stable state; a first memory for storing the measured value in a stable data state before the object to be measured is placed on the load detection section; and a second memory for storing the measured value in the stable data state with the object to be measured on the load detection section. 2 memory and
A third memory stores the measured value in a data stable state after the object to be measured is unloaded from the load detection section, and the measured value is stored in the second memory from the contents of the first and third memories. has a calculation means for estimating the zero point at the time when the value is stored and corrects the contents of the second memory, and is configured to be capable of displaying the measured value after the correction by the calculation means on the display according to a command. An electronic balance that is characterized by: