JPH0612294B2 - Electronic scales - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electronic scale capable of easily correcting a span error caused by a difference in gravitational acceleration.

(Prior Art) Since the span of the scale is affected by the acceleration of gravity on the earth,
When collectively adjusting the span of balances used in areas with different gravitational acceleration at the factory of the manufacturer, make sure that the weight of each area (hereinafter referred to as the area weight) that takes into account the gravitational acceleration of the area is used. It is necessary to prepare a large number for each scale, and when adjusting the span, check the area used for each scale and select the area weight for the scale.

For this reason, it takes a lot of time and labor for the above-mentioned manufacturer to adjust the span for each area, and especially when the usage area is changed due to fluctuations in demand, the span must be readjusted. The change of was a heavy burden on the manufacturer. In addition, the management costs of various district weights were also a heavy burden.

For this reason, the applicant of the present application has previously disclosed that, in JP-A-60-17324, the span adjustment of all scales is performed with the reference weight without using the district weight, and then the use area designated for the scale is determined by the scale. You can automatically perform span adjustment suitable for the area by simply inputting into the area. Therefore, it is not necessary to prepare the area weight for each usage area, and it is possible to change the weighing area very easily. We are proposing a new electronic scale that can be used.

This electronic scale is configured as follows.

That is, a double integral type A / which converts the weight signal into a digital value
The unknown input integration time of the D converter is controlled by a soft timer, and the output value of the A / D converter can be increased or decreased in increments of 1 count by adjusting the operating time of the soft timer. Then, the span change caused by the change of the use area of the scale is corrected by the correction of the operation time of the soft timer. That is, from the multiple districts divided by the difference in weight acceleration, the district means for designating the district where the scale is used and the soft timer for each district calculated so that the span in each district is constant It is equipped with a memory that stores the operating time and a control means that reads the operating time of the soft timer of the designated area from the memory and controls the operating time of the soft timer based on this, and The span change caused by the change is corrected. Also, in the above memory,
It is possible to store the deviation of the operating time of the soft timer of each district based on the operating time of the soft timer of the specific district, and in this case, the deviation time of the designated district is stored in the memory. It is read out, and this is added to or subtracted from the operating time of the soft timer in the specific area, and the operating time of the soft timer in the designated area is controlled by the adjusted time.

FIG. 1 is a block diagram showing the main part of such an electronic scale. In this figure, A is a sensor composed of a load cell, B is an amplifier circuit for amplifying the output signal of the sensor A, and C is a discrete integral type A / D converter.

This double integral A / D converter (C) controls an analog switch (1), an integrator (2), a comparator (3), a counter (4), and the analog switch (1). To do C
And PU (5). Analog switch (1)
Is configured to selectively input the reference voltage (Vref), the amplifier output voltage (analog signal), and the ground voltage to the integrator (2), and switching of the switch is performed by the CPU (5). Is controlled by the switching command Sa and the count stop signal Sb from the comparator (3). That is, when the count stop signal Sb is output from the comparator (3), the contact of the analog switch (1) is switched to the c terminal, the offset correction of the A / D converter (C) is performed, and the CPU (5 ), The contact of the switch (1) is switched to the terminal a and integration of the analog signal (unknown input integration) is started. And CPU
When the next switching command Sa is output from (5), the contact is switched to the terminal b this time, and the integration of the analog signal until then is switched to the inverse integration by the reference voltage (Vref). When the output voltage of the integrator (2) reaches the initial integration start voltage, the comparator (3) outputs the count stop signal Sb, whereby the contact is switched to the c terminal, and the next switching signal is output. The offset correction of the A / D converter (C) is performed until Sa is output.

Further, in the A / D converter C, a value obtained by appropriately dividing the applied voltage (V1 + V2) by the voltage dividing resistors R1 and R2 and the variable resistor Vr in order to track the weight sensor A, The reference voltage (Vref) is input.

The comparator (3) outputs a count stop signal Sb to the analog switch (1), the counter (4) and the CPU (5) when the output voltage of the integrator (2) reaches the initial integration start voltage. It is supposed to do.

The counter (4) is the CPU (5) during the unknown input integration period.
Is reset by a command Sc from the counter, and then the counting operation is started simultaneously with the start of the reverse integration by the reference voltage, and the counting operation is stopped by the count stop signal Sb from the comparator (3). Further, this counter (4) is composed of a binary counter, but here, in order to enable counting beyond its capability, the counter (4) is concerned.
When the counter (4) completes the counting operation of the counter (4) every time the counter overflows, the counter (4) determines from the output count number of the counter (4) and the counted overflow number. The total output count of is calculated. Then, the calculated total output count number is output as the output count number of the A / D converter (C) to a main CPU (not shown) that controls the entire scale.

Of course, the entire scale can be controlled by the CPU (5).

Further, the counter (4) is configured so that the count pulse Sd synchronized with the one program cycle of the program set in the CPU (5) is supplied from the CPU (5).

The CPU (5) mainly controls the unknown input integration time of the A / D converter (C).
The U (5) is provided with a soft timer that outputs the switching command Sa at a designated timing.

The operation time of the soft timer is generally given by the number of times of the process (for example, the knock process) in which one instruction cycle is constant, or the number of steps corresponding thereto, and the counter (4) is set as described above. Counts in synchronization with one instruction cycle. Therefore, for example, the second
As shown in the operation characteristic diagram of the double integral type A / D converter in the figure, the input voltage of the A / D converter (C) and the reference voltage (Vref) are equal when a weight corresponding to the weight is loaded. Adjusted to be [that is, unknown input integration time (T
1) and the inverse integration time (T2) by the reference voltage are adjusted to be equal]], the operation time is adjusted by one step of the soft timer.
The output count number of the A / D converter (C) can be adjusted in increments of one. In other words, by setting the operating time of the soft timer for loading a weight corresponding to the weighing amount to the processing time of 15000 steps, the output of the A / O converter (C) at that time can be set to 15000 counts. .

Further, in FIG. 2, the operating time of the soft timer is the time (XT) required to execute the instruction of the number of steps (XT).
s), the inverse integration time (T
2) also becomes longer by (XTs) time, and the counter at this time counts in one instruction cycle. As a result, the output number of the counter (4) increases by (X) counts.

D is a district designation means for designating a district where a scale is to be used from a plurality of districts classified by the difference in gravitational acceleration, and is constituted by, for example, a dip switch, a digital switch or the like.

By the way, a higher-precision scale with an accuracy of more than 1/3000 is divided into 16 areas throughout Japan.

E is a memory that stores the operating time of the soft timer for each district calculated so that the span in each of the districts becomes a constant value.
The operation time of the timer, or the deviation time calculated based on these, that is, the deviation of the operation time of the soft timer of each area based on the operation time of the soft timer of the specific area is stored.

F is a display device which displays a digital signal converted by the double integration A / D converter and processed.

G is a span coarse adjustment switch.
The unknown input integration time is switched stepwise to set A when the weight is loaded.
The output value of the / D converter is adjusted so that it falls within a predetermined range.

By the way, in the case of a scale whose accuracy is 1/5000, in Japan, the whole country is divided into 16 areas, and the difference in gravitational acceleration between the areas is set to 0.001 m / sec ² per area.

Therefore, the deviation value (ΔW) of the weight (W) between the first area (gravitational acceleration g ₁ ) and the second area (gravitational acceleration g ₂ ) is ΔW = {(g ₁ −g ₂ ) /9.8. } × W can be calculated. Table 1 shows the correction value of the unknown input integration time corresponding to the above deviation value for each district in correspondence with each unknown input integration time divided every 500 counts, and particularly, the first district is used as a reference. The case is shown. According to this table, for example, when the district number A is set to 1 and the unknown input integration time is set to a time corresponding to 15,000 count steps, as is clear from Table 1, 1. It is understood that the unknown input integration time should be increased by 53 counts.

(Problems to be Solved by the Invention) By the way, when the unknown input integration time is adjusted in several steps by the dip switch for the span coarse adjustment as described above, the deviation value of 1. The 53 count also changes depending on the unknown input integration time. For example, when the unknown input integration time is set to a time equivalent to 14500 count steps, the deviation value per district is 1.48 counts, and when the unknown input integration time is set to a time equivalent to 15500 count steps, the district The deviation value per hit is 1.5
8 counts. In this way, the district number A is 16, and the type n of unknown input integration time for span coarse adjustment is 0 to 8
In terms of stages, as shown in Table 1, (16-1) × 8 = 12
There is a problem in that 0 kinds of fixed data for correction are required, and the memory capacity increases.

The present invention is intended to solve the problems of the prior art and calculates the deviation value of the unknown input integration time in each area without storing the deviation value of each area with respect to the unknown input integration time. It is therefore an object of the present invention to provide an electronic balance that can be manufactured with a small memory capacity.

(Means for Solving the Problem) According to the present invention, the correction value for the unknown input integration time for eliminating the span error caused by the difference in gravitational acceleration increases at a constant rate every time the district number increases by one. A double integration type A / D converter for converting a weight signal into a digital value and a span error caused by a difference in gravity acceleration by controlling an unknown input integration time of the A / D converter. In an electronic scale equipped with a soft timer that corrects, the designated means for designating the district where the scale is used from a plurality of districts classified by the difference in gravitational acceleration and the district number difference between the specific district and the designated district , And the unknown input integration time difference caused by one district difference when the set unknown input integration time of the specific area is used as a reference, the A correction value is calculated, and the set unknown input integration time is corrected by the calculated value, and means for calculating the unknown input integration time in the designated area is provided, and the operation time of the soft timer is calculated by the calculated unknown input integration time. The above-mentioned problems are solved by controlling the. The unknown input integration time deviation can be stored in a memory in advance or can be calculated by multiplying it by a constant correction factor, and the unknown input integration time can be adjusted in several steps by the coarse span adjustment switch. In this case, the unknown input integration time deviation is stored in the memory in correspondence with the unknown input integration time deviation time of each step, or is set to the unknown input integration time set by the span coarse adjustment switch. It is possible to calculate by multiplying the correction factor.

(Embodiment) In the present invention, the hardware configuration is the same as that of the conventional mode shown in FIG. 1, and therefore description thereof will be omitted. Here, a method of span adjustment under the above configuration will be described. explain.

First, the district designation switch D is used to designate the region where the scale is currently located, and then the weight is loaded, so that the span coarse adjustment switch G is set so that the span of the A / D converter reaches a predetermined value, for example, 15000 counts. And the variable resistor Vr.
That is, when the span of the A / D converter is less than 15000 counts, the span coarse adjustment switch G is switched to increase the unknown input integration time or decrease it when the span is 15,000 counts. Close to. Next, the variable resistor Vr is operated and adjusted so that the span is exactly 15000 counts. This completes the adjustment of the scale. At this time, when the coarse span adjustment switch is set to the unknown input integration time corresponding to, for example, 14000 counts, the unknown input integration time deviation caused by increasing the area by one area is 1.43 as shown in Table 1.
Further, when the unknown input integration time corresponding to 15000 counts is set, the deviation is 1.53.
Therefore, when the setting position of the coarse span adjustment switch G is set to, for example, an unknown input integration time corresponding to 15000 counts, this 15000 counts is multiplied by a fixed correction factor, that is, (0.001 / 9. 8) × 15000 = 1.53 is calculated to calculate the unknown input integration time deviation (1.53) caused by the difference in one area, and this is multiplied by the area number difference between the specific area and the specified area to specify the area. 1500 in above
A correction value for 0 count is calculated.

That is, since the specific district in this case is set to the first district as shown in Table 1, if the designated district is, for example, the eighth district, the district number difference (8-1) = 7, and the above correction value is obtained. Is equivalent to 1.53 × 7 = 10.71 counts. Therefore, this value is added to the unknown input integration time, 15,000 count steps, and the fractional part is rounded off, and the result is set as the unknown input integration time in the eighth area.

FIG. 3 is a flowchart showing an example of such a processing procedure. Next, this flowchart will be described.

(1) The command Sa for starting the unknown input integration is output to the analog switch 1 (step a ₁ ), and the process waits until the processing for 12950 counts is completed (step a ₂ ). This is because when the unknown input integration time is set as shown in Table 1, the coarse span adjustment step is set to the first rank,
That is, if the count is set to 13000 when n = 0, the processing time thereafter is 50 counts. Therefore, in the initial setting, 12950 count is set in consideration of this time in advance.

(2) reads the setting rank n Span coarse adjustment switch (step _a 3). For example, n = 4 is read as shown in Table 1. Next, n is set to 1 every time 500 counts have passed.
When decrementing and n = 0, the process proceeds to the next process (steps a ₄ and a ₅ ). That is, 500 × 4 in the meantime
Earn time for the count.

(3) Subsequently, the district correction value M is calculated (step a
₆ ). This process is performed by the subroutine of Step _b 1 ~b _7.

Read the setting rank n of the span coarse adjustment switch. In this example, n = 4 is read (step b ₁ ). Then, the memory in advance are stored, the deviation value corresponding to n, in this example reads 1.53, which is stored in the register m and m '(Step b _2).

The setting area A of the area designation switch D is read. For example, if the district No8, reads the A = 8 (Step _b 3).

Next, the condition determination of A = 1 is performed (step b ₄ ), and NO
If so, the content 1.53 of the register m is added to the content of the register m ′, this is loaded into the register m ″, and the content of this register m ″ is loaded into the register m ′ to update the content ( Step b ₅ ) and decrement the district number by 1 (step b ₆ ).

The repeated loop process, if even a A = 1, sets the value of m 'at this time as a district correction value M (step b _7). That is, in the above example, 1.53 × 7 = 10.71 is obtained as the area correction value M by the loop processing of seven times.

(4) If the area correction value M is obtained by the processing of the subroutine and is set in the memory, the value of this area M is further counted for the area correction value (step a ₇ ). In the above example, it consumes 15000 counts the processes from step a _6, will wait 10.71 counts Following this. Therefore, if 15011 steps are counted as a whole, the unknown input integration process is stopped (step a
₈ ) The correction of the span error caused by the difference in gravitational acceleration is completed.

In the above embodiment, the unknown input integration time can be set and changed in multiple stages, but the setting is not limited to this, and one stage fixed one is also applicable. In addition, the unknown input integration time deviation caused by the difference in one area is
This can be stored in the memory in advance, or it can be calculated each time. Further, in this embodiment, the span of the A / D converter is always set to 15000 regardless of the used area, but the value is arbitrary, and when the range is switched, the unknown input integration is performed. The range can be switched by multiplying the time by an integer. Further, in this embodiment, the first area where the unknown input integration time is the minimum is set as the specific area, but this can also be set arbitrarily.

(Effects of the Invention) As described above, according to the present invention, the correction value for the unknown input integration time for keeping the span constant in each area changes by the same correction count number when the area number changes. Focusing on the fact that only the width of the change is stored in the memory or calculated to calculate the unknown input integration time in the designated area, the memory capacity becomes extremely small and the device The effect is that it becomes easy.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of an electronic scale to which the present invention is applied, FIG. 2 is an explanatory diagram of operating characteristics of a double integral A / D converter, and FIG. 3 shows a processing procedure of the present invention. It is a flowchart. A ... Weight sensor, B ... Amplifier circuit, C ... Double integration type A / D converter, D ... District designation switch, E ... Memory, F ... Display device, G ... Span coarse adjustment switch .

Claims (5)

[Claims] 1. A double integration type A / D converter for converting a weight signal into a digital value and an unknown input integration time of the A / D converter are controlled to correct a span error caused by a difference in gravitational acceleration. In an electronic scale equipped with a soft timer, from a plurality of districts divided by the difference in gravitational acceleration, district designation means for designating the district where the scale is used, and the district number difference between the specific district and the designated district, and Based on the unknown input integration time deviation caused by one district difference when the set unknown input integration time of the specific area is used as a reference, a correction value for the above-mentioned set unknown input integration time in the designated area is calculated, and the calculated value is used as the above. A means for calculating the unknown input integration time in the designated area by correcting the set unknown input integration time is provided, and the operating time of the soft timer is controlled by the calculated unknown input integration time. Electronic scales, characterized in that the so that. 2. The memory for storing the deviation of the unknown input integration time, the calculating means reads the deviation, and multiplies the deviation by the difference between the district numbers to obtain a correction value for the set unknown input integration time in the designated district. An electronic scale according to claim (1), further comprising a calculating means. 3. The span coarse adjustment switch, wherein the calculating means sets the set unknown input integration time in multiple stages, and the memory for storing the deviation in correspondence with the set unknown input integration time of each stage. It is provided with means for reading out the deviation corresponding to the set unknown input integration time that has been set, and multiplying this by the district number difference to calculate a correction value for the set unknown input integration time in the designated area. The electronic balance according to claim (1), characterized in that: 4. The calculating means calculates the unknown input integration time deviation by multiplying a set unknown input integration time of a specific area by a constant correction factor, and multiplies the calculated deviation by the area number difference. The electronic balance according to claim (1), further comprising means for calculating a correction value for the set unknown input integration time in a designated area. 5. The electronic scale according to claim 4, wherein the calculating means includes a coarse span adjustment switch for switching and setting the set unknown input integration time in multiple stages.