JP2002098580A - Output adjustment method for multi-load cell scale - Google Patents

Abstract

(57) [Summary] [Problem] To reduce the load of a known load on a mounting table for span adjustment by one.
Provided is an output adjustment method for a multi-load cell scale that can obtain an accurate span coefficient after adjustment of an eccentric error by performing the adjustment only once. SOLUTION: The number of digital load cells is n, and each output value of each digital load cell at no load is Wz1,.
Wzn, Ws1,... Wsn, the output values of the digital load cells under a known load for span adjustment, and P1 ′,.
S = [｛(Ws1−Wz1) where n ′ is a temporary span coefficient and S ′ is a true eccentric error correction coefficient.
× P1 ′｝ +... + ｛(Wsn−Wzn) × P
n ′｝] × S ′ / [{(Ws1-Wz1) × P1} + ·
.. + {(Wsn−Wzn) × Pn}] to calculate the true span coefficient S.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting the output of a multi-load cell type balance for performing eccentricity error adjustment and span adjustment.

[0002]

2. Description of the Related Art A multi-load cell scale in which a stage is supported by a plurality of digital load cells is already known. FIG. 4 is a perspective view of the scale, in which four digital load cells 1a to 1d are arranged at four corners on the back side of the mounting table 2, and
I support. When a load is applied to the mounting table 2, each of the digital load cells 1a to 1d outputs each detected value as a digital value.

A method for processing the output values of the digital load cells 1a to 1d will be described with reference to FIG.

When the load is applied to the mounting table 2, the output values of the digital load cells 1a to 1d are represented by W1 to W4,
Assuming that the output values of the digital load cells 1a to 1d when no load is applied to the mounting table 2 are Wz1 to Wz4, their respective differences (W1 to Wz1) to (W4 to Wz)
4) is multiplied by eccentric error correction coefficients (four-corner correction coefficients) P1 to P4, which are obtained in advance and stored in the memory, to individually correct the respective output values of the digital load cells 1a to 1d. (Four corner correction) is performed. Then, the sum of these multiplication values [｛(W1−Wz1) × P
1｝ + ｛(W2-Wz2) × P2｝ + ｛(W3-Wz
3) × P3 {+ {(W4-Wz4) × P4}] is multiplied by a span coefficient S obtained in advance and stored in a memory to perform span correction, and further perform various corrections such as temperature correction. The result is digitally displayed on the indicator as a measured weight value of the object placed on the platform 2.

Conventionally, the span coefficient S has been determined by the following procedure.

After the balance is installed at the place of use, for example, when the weighing capacity (maximum allowable mass that can be measured) is 4 tons, 4 tons as a known load for span adjustment is placed on the center R5 of the mounting table 2 shown in FIG. (1)
First, a temporary span coefficient S 'is obtained based on the equation. Ws
1 to Ws4 indicate output values of the digital load cells 1a to 1d when the weight load of 4 tons is applied,
Wz1 to Wz4 indicate output values of the digital load cells 1a to 1d when no load is applied to the mounting table 2, and P1 'to P4' are temporary or initial set four-corner correction coefficients. That is, when a load of 4 tons is applied to the mounting table 2 and the scale outputs 40000 as a correct value corresponding to 4 tons, [{(Ws1−Wz1) × P1 ′} in equation (1). + ｛(Ws2-Wz
2) × P2 ′｝ + ｛(Ws3-Wz3) × P3 ′｝ +
{(Ws4−Wz4) × P4 ′}] is determined to be a temporary span coefficient S ′ so as to be 40000.

Therefore, at this time, an accurate balance output cannot be obtained only when a load is applied to the center of the mounting table 2, and the object to be weighed is placed at other places, for example, at the four corners of the mounting table 2. The output value when mounted is somewhat inaccurate.

Next, true four-corner correction coefficients P1 to P4 are obtained as follows.

When the number of digital load cells is four, a weight (1 ton), for example, one-fourth of the weighing capacity, is first used as a known load for adjusting the eccentricity error, as shown in FIG.
At the specific location R1. Here, the first specific portion R
1 is an intersection of a straight line connecting the middle point N1 of the upper side of the mounting table 2 and the middle point N4 of the right side and a diagonal line Q1 connecting the upper right corner and the lower left corner of the mounting table 2 in the vicinity of the digital load cell 1a. is there. At this time, the output values of the digital load cells 1a to 1d are Ws11 to Ws41, and the true four-corner correction coefficient is Ps.
Assuming that the weight is 1 to P4 and the weight is M, the equation I shown in FIG.
Can be set up.

Next, the same 1-ton weight is used in the second step shown in FIG.
At a specific location R2. Here, the second specific portion R
2 is an intersection of a straight line connecting the middle point N1 of the upper side of the mounting table 2 and the middle point N2 of the left side and a diagonal line Q2 connecting the upper left corner and the lower right corner of the mounting table 2 in the vicinity of the digital load cell 1b. is there. At this time, the output values of the digital load cells 1a to 1d are represented by Ws12 to Ws42, and the true four-corner correction coefficient is represented by P.
Assuming that the weight is 1 to P4 and the weight is M, the equation II shown in FIG.
Can be set up.

Next, the same 1-ton weight is used in the third step shown in FIG.
At the specific location R3. Here, the third specific portion R
Reference numeral 3 denotes an intersection of a diagonal line Q1 near the digital load cell 1c and a straight line connecting the middle point N2 and the middle point N3 on the left side of the mounting table 2 in the figure. At this time, the output values of the digital load cells 1a to 1d are represented by Ws13 to Ws4.
3. Assuming that the true four-corner correction coefficients are P1 to P4 and the weight of the weight is M, Equation III shown in FIG. 2 can be established.

Next, the same 1-ton weight is used in the fourth step shown in FIG.
At the specific location R4. Here, the fourth specific portion R
Reference numeral 4 denotes an intersection of a diagonal line Q2 near the digital load cell 1d and a straight line connecting a middle point N4 on the right side of the mounting table 2 and a middle point N3 on the lower side. At this time, the output values of the digital load cells 1a to 1d are represented by Ws14 to Ws4.
4. Assuming that the true four-corner correction coefficients are P1 to P4 and the weight of the weight is M, Equation IV shown in FIG. 2 can be established.

In order to form these four formulas I to IV,
A weight for adjusting an eccentric error is placed on each of the specific locations R1 to R4, and the output values Ws11 to Ws41, Ws12 to Ws42, and Ws1 of the digital load cells 1a to 1d at this time are placed.
When obtaining 3 to Ws43 and Ws14 to Ws44, the temporary span coefficient is determined in advance, so that the scale is almost weight load M
Shows a value close to. Therefore, when the scale shows a value that is significantly different from the weight M when the eccentricity error adjustment weight is placed, it is determined that there is an error in the placement work or that an abnormality has occurred in the load cell or the signal processing circuit. it can.

By solving these quaternary linear equations, true four-corner correction coefficients P1 to P4 are obtained. Alternatively, Ws11 to Ws41, Ws12 to Ws42,
Of the values of Ws13 to Ws43 and Ws14 to Ws44, P1 to P4 are adjusted so as to reduce the large value and increase the small value, and repeat the adjustment until the error between the right sides of the formulas I to IV is within the reference. The four corner correction coefficients P1 to P4 may be obtained.

When the true four-corner correction coefficients P1 to P4 are obtained,
The temporary four-corner correction coefficients or the initial set values P1 ′ to P4 ′ stored in the memory are rewritten to true four-corner correction coefficients P1 to P4. However, since the span as the whole scale may change (almost in many cases) due to the change of the four-corner correction coefficients, it is necessary to confirm whether the temporary span coefficient S ′ obtained earlier is appropriate. Therefore, conventionally, a work of mounting a 4 ton weight for span adjustment again on the center position R5 of the mounting table 2 shown in FIG. 5 is used to check whether or not the span has changed, and if the span has changed,
The true span coefficient S that satisfies the equation (2) has been determined.

[0016]

That is, conventionally,
The work of loading and unloading the weight on the mounting table is performed using the temporary span coefficient S '.
When obtaining true four corner correction coefficients P1 to P4,
This has been performed three times when determining the true span coefficient S. However, the work of loading and unloading weights on and from the platform 2 takes time and effort, and especially on a truck scale that weighs a vehicle by placing the vehicle on the platform 2, the weight of the weight to be loaded can be tens of tons. In this case, for example,
The operation is performed by stacking a plurality of weights having a relatively small weight on the top, and performing such an operation three times is a great effort.

The present invention has been made in view of the above-described problem, and only requires a single load of a known load for span adjustment on a mounting table.
An object of the present invention is to provide an output adjustment method for a multi-load cell scale that can obtain an accurate span coefficient after eccentricity error adjustment.

[0018]

In order to solve the above-mentioned problems, the present invention applies a known load for span adjustment to a platform supported by a plurality of digital load cells, and sets the number of digital load cells to n, The output values of each digital load cell when no load is applied to Wz1 and Wz
2,... Wzn, each output value of each digital load cell when a known load for span adjustment is applied to the mounting table is represented by Ws.
.., Wsn,... Wsn, the tentative or initially set eccentricity error correction coefficient set for each load cell is P
1 ′, P2 ′,... Pn ′, [{(Ws1−Wz1) × P1 ′} +.
n−Wzn) × Pn ′｝] × S ′ = tentative span coefficient S ′ is obtained from the known load for span adjustment, and a known load for eccentricity error adjustment is sequentially applied to a plurality of places on the mounting table. , Pn for individually correcting each output value of each load cell, S = [{(Ws1−Wz1) × P1 ′} +... +
{(Wsn−Wzn) × Pn ′}] × S ′ / [｛(Ws
1−Wz1) × P1｝ +... + ｛(Wsn−Wzn)
× Pn｝] to calculate the true span coefficient S.

That is, according to the present invention, it is possible to confirm the correctness of the span coefficient after obtaining the eccentricity error correction coefficient without applying a load to the mounting table using a weight or the like. Since the calculation only needs to be performed using a known value, the time and labor can be greatly reduced.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

Also in this embodiment, as shown in FIG. 4, four digital load cells 1a to 1d are arranged at the four corners on the back side of the mounting table 2 and support the mounting table 2. When a load is applied to the mounting table 2, each of the digital load cells 1a to 1d outputs each detected value as a digital value. The provisional span coefficient S ′ and the true eccentric error correction coefficients (four corner correction coefficients) P1 to P4 are obtained in the same manner as in the above-described conventional example.

After obtaining the temporary span coefficient S ', the four corner correction coefficients are changed to temporary values or initial set values P1' to P4 '.
Is updated to true four-corner correction coefficients P1 to P4 from
The true span coefficient S is obtained as follows.

That is, since the right sides of the equations (1) and (2) shown in FIG. 2 are equal, the left side of the equation (1) = the left side of the equation (2) as shown in the equation (3) of FIG. The true span factor S is defined. Here, the temporary span coefficient S ′ previously obtained, the output values Ws1 to Ws4 of the digital load cells 1a to 1d under a known load (4 tons of weight),
, The output values Wz1 to Wz4 of the digital load cells 1a to 1d when no load is applied, the true eccentric error correction coefficients P1 to P4, the temporary eccentric error correction coefficients or the initial set values P1 'to P4'. Are all known values, the true span coefficient S is obtained by substituting these values into the equation (3).
If the denominator of the first equation on the right side of equation (3) is equal to the numerator, S =
S ′, and the temporary span coefficient S ′ can be used as it is as a true span coefficient without change in the span correction shown in the equation (4). As described above, in the present embodiment, it is possible to confirm whether the temporary span coefficient S ′ is correct or not and to obtain the accurate span coefficient S without performing the operation of placing the 4 ton weight on the mounting table 2 again. it can. Then, using the true span coefficient S and the true four-corner correction coefficients P1 to P4, each output of each of the load cells 1a to 1d at the time of actual weighing when the object to be weighed is mounted on the mounting table 2. Span correction and four-corner correction of the values W1 to W4 are performed by the calculation of equation (4), and various corrections such as temperature correction are performed. The correction is digitally displayed on the indicator as a measured load of the object to be weighed.

Although the embodiments of the present invention have been described above, the present invention is, of course, not limited thereto, and various modifications can be made based on the technical concept of the present invention.

In the above embodiment, the number of digital load cells is four, but the number is not limited to this, and may be eight, for example. Also in this case, the digital load cells are arranged at predetermined intervals with respect to the mounting table 2.

The present invention can be applied not only when the balance is installed at the place of use, but also when re-adjusting the scale which has been installed and has been used for a certain period of time.

[0027]

As described above, according to the present invention, the calculation of the true and accurate span coefficient after obtaining the eccentricity error correction coefficient can be performed without placing the weight on the mounting table, so that it is troublesome and time consuming. Can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a flow of processing of each output value of each digital load cell.

FIG. 2 is a diagram describing various relational expressions for obtaining a span coefficient and an eccentricity error coefficient.

FIG. 3 is a diagram showing a definition expression of a true span coefficient S and an operation expression showing span correction and eccentricity error correction.

FIG. 4 is a perspective view of a multi-load cell scale.

FIG. 5 is a plan view of the same.

[Explanation of symbols]

1a to 1b Digital load cell 2 Mounting table P1 to P4 True eccentric error correction coefficient P1 'to P4' Temporary eccentric error correction coefficient (initial setting value) S True span coefficient S 'Temporary span coefficient W1 to W4 Each output value Ws1 to Ws4 of each digital load cell when an object to be weighed is placed on the table Each output value Wz1 to Wz4 of each digital load cell when a known load for span adjustment is applied to the table Output value of each digital load cell when no load is applied to

Claims (1)

[Claims] 1. A method for adjusting the output of a multi-load cell scale in which a mounting table is supported by a plurality of digital load cells for outputting respective detection values as digital values, wherein a known load for span adjustment is applied to the table. The number of the digital load cells is n, and the output values of the digital load cells when no load is applied to the table are Wz1, Wz2,.
n, when the known load for the span adjustment is applied to the stand, the output values of the digital load cells are represented by Ws1 and Ws, respectively.
s2,... Wsn, tentative or initially set eccentricity error correction coefficients set for each load cell are P1 ′, P2 ′,.
n ′, [｛(Ws1−Wz1) × P1 ′｝ +... + ｛(Ws
n−Wzn) × Pn ′｝] × S ′ = Temporary span coefficient S ′ is determined from the known load for span adjustment, and a known load for eccentricity error adjustment is sequentially applied to a plurality of locations on the table. .., Pn for individually correcting the output values of the load cells.
S = [{(Ws1−Wz1) × P1 ′} +... +
{(Wsn−Wzn) × Pn ′}] × S ′ / [｛(Ws
1−Wz1) × P1｝ +... + ｛(Wsn−Wzn)
× Pn｝], and the true span coefficient S is calculated and obtained from the multi-load cell scale output adjustment method.