JPH076828B2 - Automatic zero point correction method for combination weighing device - Google Patents

Description

The present invention relates to an automatic zero point correction method for a combination weighing device.

(Prior Art) The weight value of an article put in a plurality of weighing machines is measured, and the weight value obtained by each weighing machine is input to an arithmetic and control unit composed of a microcomputer, etc. The combination calculation is executed with the values, and the combination weight value is equal to the target weight value, or the optimum combination with the combination weight value within the range of the upper limit and the lower limit is selected, and the optimum combination is selected. A combination weighing device that discharges articles from a selected weighing machine is in practical use.

Each weighing machine is provided with a weight detection unit such as a load cell, which converts a weight signal obtained as an analog value into a digital value and performs predetermined arithmetic processing with a microcomputer or the like. Since the dust and the like of the articles to be weighed adhere to the machine and the zero point is displaced, it is necessary to perform the zero point correction every predetermined weighing cycle.

(Problems to be solved by the invention) As described above, the correction of the zero point is performed every constant weighing cycle, but this is based on the assumption that the movement of the zero point is almost proportional to the passage of time. There is.

However, when weighing the article to be weighed, there may be a difference in the shape and properties of the article to be weighed depending on the weighing time. For example, the property of the item to be weighed differs depending on the temperature during processing of the item to be weighed and the state of the manufacturing machine, and the amount of adhered weighing debris changes. There is also a difference in the adhesion state of the weighing residue after weighing. FIG. 4 is a characteristic diagram showing a change in the zero point movement amount with time. Conventionally, the zero point correction is
Although it was performed at time intervals equal to t ₁ , t ₂ , ... T _n , as shown in the figure, the zero point movement amount is not constant over time.

Therefore, if the zero point correction is performed at fixed time intervals, there is no problem if the amount of movement of the zero point is large, but if the zero point correction is performed even when the amount of movement of the zero point is small, the weighing accuracy is rather improved. There was a problem of lowering. That is, a weighing machine that performs zero point correction does not perform weighing in its weighing cycle, and therefore the number of weighing machines that participate in combination weighing decreases. there were. Therefore, the present invention provides an automatic zero-point correction method for a combination weighing device, in which the zero-point correction interval is variable, with the object of solving the problems of the prior art.

(Means for Solving Problems) In the present invention, the weight values obtained by a plurality of weighing machines are combined and calculated, and a weighing machine that is an optimum combination with respect to a target weight value is selected and selected. In a combination weighing device that discharges articles from a specified weighing machine, when the zero point movement is automatically performed due to the adherence of weighing residue on the articles to be weighed, the time interval for zero point correction according to the movement amount of the zero point. The present invention provides an automatic zero point correction method for a combination weighing device that changes

(Operation) The present invention determines the time interval of the zero point correction of the combination weighing device,
Since it changes according to the magnitude of the zero point movement amount of each weighing machine, it can quickly respond to the zero point movement due to the rapid adhesion of weighing debris, and does not unnecessarily perform the zero point correction of the weighing machine. The number of weighing machines participating in the combination weighing can be prevented from decreasing, and the weighing accuracy is improved.

Example An example of the present invention will be described below with reference to the drawings. Third
The figure is an illustration of the zero-point correction method of the present invention. According to the present invention, the zero-point correction time interval t ₃ ′, t ₄ ′ is short when the zero-point movement amount is large, and the zero-point correction time interval t ₃ ′ is small when the zero-point movement amount is small. ₁ ′, t ₂ ′,
This is characterized by lengthening t _n-1 ′ and t _n ′.

FIG. 1 is a schematic configuration diagram of a control portion for performing zero point correction of a combination weighing device to which the present invention is applied. In the figure, a is a weighing machine consisting of W ₁ , W ₂ , ... W _n and n units, b is a multiplexer, c is a zero-point correction subtractor, d is a sample hold circuit, and e is an analog signal converted into a digital signal. AD converter, f is a central processing unit (CPU) such as a microcomputer, g is a DA converter that converts a digital signal into an analog signal, h is a zero point adjustment flag, a supply flag of the article to be weighed, a zero point adjustment count , A memory having areas for counting the number of weighings, set weight, upper and lower weights, etc., i is an indicator using a lamp, j is a key input section, k
Is a packaging machine. Further, a setting unit (not shown) for setting the set weight, the upper limit and the lower limit is provided.

Next, the operation of this control device will be described. Packing machine k
When the timing signal from the CPU is input to the CPUf, the switching signal is input from the CPU to the multiplexer b, and the weight value obtained by the weighing machine a is sequentially output from the multiplexer, AD
It is taken into the CPU through the converter e. Here, when executing the zero point adjustment for a certain weighing machine, a command signal is generated from the CPU, this signal is converted into a digital signal by the DA converter g, and the zero point correction subtractor c is used. Input to the + terminal. An output signal from the multiplexer is applied to the minus side terminal of the subtractor, and the deviation signals of both are input to the sample hold circuit d. A sample and hold command signal is input from the CPU to the sample and hold circuit, and the signal sampled at a predetermined cycle is input to the CPU through the AD converter, and the time interval is changed according to the zero point movement amount as shown in FIG. The zero point correction is performed by changing. The correction of the zero point according to the present invention is specifically performed as follows.
For example, three types of intervals of 2,8,16 are prepared as zero-point correction time intervals (incoval). Here, if the interval is "2", the zero point correction is performed once every two weighing cycles, and the interval "16" is the weighing cycle.
Zero point correction shall be performed once every 16 times.

When starting the weighing machine for the first time, preset “2” and make sure that the zero point shifts when performing zero point adjustment.
If it is within 0.1g, it is judged that the deviation of the zero point is small,
Next, "8" is set. Furthermore, even if the zero point shift is within 0.1g even with the interval of "8", the interval of zero point adjustment is set to "16" and the time interval of zero point adjustment is increased. If the deviation of the zero point becomes 0.1g or more, immediately reset the preset value of the interval to "2", increase the frequency of zero point adjustment, and quickly respond to the movement amount of the zero point. After that, if the movement amount of the zero point changes, the frequency of the zero point adjustment is changed accordingly.

The preset value of the zero point adjustment interval may be three or more, and the interval value can be set arbitrarily. further,
It is also possible to use a preset value corresponding to the shift of the zero point when adjusting the zero point. For example, if the zero point movement amount is less than 0.1g, set the preset value as "16", if 0.1g or more and less than 0.5g, set the preset value as "8", and if 0.5g or more, set the preset value as "2". Remember.

FIG. 2 is a flowchart showing the processing procedure of the present invention. Next, this flowchart will be described.

(1) Check the timing signal generator from the packaging machine (step P _1), and sequentially input weight of all of the weighing machine and stored in the memory (Step P _2). Next, zero point adjustment (zero adjustment)
Combined calculation with a weighing machine whose flag is "L", and equal to or closest to the target amount above the target weight and below the upper limit weight 1
Find the combination of pairs (step P ₃ ). As long obtained optimal combination (Step P _4), according to the resulting combined to discharge articles from the weighing machines corresponding (Step P _5), the supply flag of the weighing machine to "H" (step P _6).

(2) The value of all zero adjustment count memories is incremented by 1 (step P ₇ ). Next, the zero adjustment flag is "H"
Check the presence or absence of the weighing machine (step
P _8), if there is no corresponding weighing machine, to determine whether metering number count memory value is 0 (step
P ₉ ). If the determination is NO, the value of the metric number count memory 1 Dekurinmento (Step P _10), and supplies the product supply flag is the weighing machine of the "H" (step P _11).

(3) In the process of step P ₉ , if the weighing count memory value is 0, it corresponds to one weighing machine with the largest zero adjustment memory value among the weighing machines that have discharged the item. Set the zero adjustment flag to "H" (step
P ₁₂ ). Then, the supply flag of the weighing machine which zero-adjustment flag corresponds to "H" to "L" (step P _13), followed by
Zero adjustment flag to zero clears the zero adjustment count memory of the weighing machine of the "H" (step P _14), the process proceeds to step P _11.

(4) In the processing of step P _8, when the zero-adjustment flag is the weighing machine of the "H" is zero adjustment flag is "H"
Perform zeroing the weighing machine (step P _15), the deviation of the zero point before the zero adjustment, stores a value corresponding thereto to the metering number count memory (step P _16). Then, the zero adjustment flag is a weighing machine supply flag of "H" to "H" (step P _17), the zero adjustment flag to "L" (step P _13). Hereinafter, the process proceeds to the following processing steps P _9.

Although the gist of the present invention has been described above with reference to the specified embodiment, it is apparent that various changes and modifications can be made to the present invention based on what has already been described.

(Effect of the Invention) As described above, according to the present invention, when the automatic zero point correction is executed in the combination weighing device, the time interval for performing the zero point correction is changed according to the movement amount of the zero point. The zero point can be corrected quickly even if the measurement residue of the article is rapidly attached, and if the amount of movement of the zero point is small, the time interval for performing the zero point correction is lengthened, so unnecessary zero It is possible to eliminate the point correction and increase the number of weighing machines participating in the combination weighing to improve the weighing accuracy.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a control portion of a combination weighing device to which the present invention is applied, FIG. 2 is a flowchart, FIG. 3 is an explanatory diagram of the present invention, and FIG. 4 is an explanatory diagram of a conventional example. a ... Weighing machine, b ... Multiplexer, c ... Subtractor for zero point correction, d ... Sample and hold circuit, e ... AD converter, f ... CPU, g ... DA converter, h ... Memory i
…… Display, j …… Key input section.

Claims (1)

[Claims] 1. A weight value of an article loaded in a plurality of weighing machines is measured, the weight value obtained by each weighing machine is input to an arithmetic control unit, and a combination operation is executed by the weight value. , The combination weighing value is equal to the target weight value, or the optimum combination within the range of the upper limit value and the lower limit value that is closest to the target weight value is selected, and the combination weighing device that discharges the articles from the selected weighing machine is selected. In the automatic zero point correction method for automatically performing the zero point correction at a predetermined time interval, the combination weighing is characterized in that the time interval of the zero point correction is changed according to the magnitude of the zero point movement amount of each weighing machine. Automatic zero point correction method for equipment.