JPH0795001B2 - Load cell scale - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a load cell balance capable of preventing an output change due to drift.

(Prior Art) A conventional load cell balance using a plurality of load cells detects a weight value of an object to be weighed by adding detection values output from each load cell when the object to be weighed is placed.

(Problems to be Solved by the Invention) However, the above-mentioned conventional load cell balance has a problem that a drift such as a temperature change and a temporal change is also added, and a temperature change at a zero point becomes large.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a load cell balance capable of suppressing a zero point change and the like due to drift.

[Structure of Invention]

(Means for Solving the Problem) The load cell balance according to claim 1 is a load cell balance in which detection values according to weights output from a plurality of load cells are added to calculate a weight value, and the load cells output from each load cell. A change direction discriminating means for discriminating the temporal change direction of the detected value, and a drift detecting means for not changing the weight value when the changing direction of the detected value of each load cell discriminated by the change direction discriminating means is not constant. It was done.

The load cell balance according to claim 2 is the load cell balance according to claim 1, further comprising an analog-digital conversion means for converting the detection value output from each load cell into an analog-digital conversion, and the changing direction determination means is the analog-digital conversion means. The change is determined by counting a predetermined number of conversion means.

The load cell balance according to claim 3 is the load cell balance according to claim 1 or 2, further comprising a test switch for instructing a state in which no load is applied to each load cell, and an alarm means for issuing an alarm. In this case, the warning means issues an alarm when the change direction determination means determines that the change direction is not constant.

(Operation) In the load cell balance according to the first aspect, the weight value is calculated by adding the detection values according to the weights output from the plurality of load cells. Then, the change direction determination means determines the time-dependent change direction of the detection value output from each load cell, and when the change direction is not constant, the arithmetic processing means does not change the weight value.

According to a second aspect of the load cell scale of the first aspect, in the load cell scale of the first aspect, the detection value output from each load cell is analog-digital converted by an analog-digital conversion means, and the change direction determination means is the analog-digital conversion means. When a predetermined number of counts are output from, a change is detected and a minute change below a predetermined value is not detected.

According to the load cell balance of claim 3, in the load cell balance of claim 1 or 2, when an instruction is given by a test switch, the alarm means issues an alarm when the change direction is fixed by the change direction determining means.

(Example) Hereinafter, a load cell balance of one example of the present invention will be described with reference to the drawings.

In FIG. 2, reference numeral 1 denotes a quadrangular base body formed of an aluminum material or the like, and load cells 2a, 2b, 2c, 2d are attached to the four corners of the top surface of the base body 1. The load cells 2a, 2b, 2c, 2d are formed in a substantially rectangular Roberval mechanism having a communication hole of a substantially 8-shape communicating between the side surfaces. In addition, four strange gauges 3a, 3b, 3c, 3d are attached to each of the load cells 2a, 2b, 2c, 2d at two locations on the upper surface of the thin portion above the communication holes. On the other hand, one end of the lower surface of the load cells 2a, 2b, 2c, 2d is fixed to the mounting bases 4a, 4b, 4c, 4d provided on the base 1, and the lower surface of the other end is an overload stopper provided on the base 1. 5a, 5b, 5
It faces c and 5d. Also, load cell 2
Projections 6a, 6b, 6c, 6d are attached to the other ends of the upper surfaces of a, 2b, 2c, 2d. The tips of the protrusions 6a, 6b, 6c, 6d are opened at the lower surface and come into contact with the inside of the plate 7 as an object holder slightly larger than the base 1 to support the plate 7 so as to be vertically movable. is doing.

Further, the base body 1 is provided with a storage case 8 in which electronic parts and the like are stored.

Further, the base 1 has legs 9a, 9b, 9c, 9d whose height can be changed.
Is provided to hold the base 1 horizontally.

Then, as shown in FIG. 1, the load cells 2a, 2b, 2c, 2d
Is an analog-to-digital converter (analog-to-digital converter) as an analog-to-digital converter that converts an analog value into a digital value via amplifiers 11a, 11b, 11c, and 11d that amplify detection values from these load cells 2a, 2b, 2c, and 2d. A / D converter) 12a, 12
The analog / digital converters 12a, 12b, 12c and 12d are connected to the microcomputer system 13. Further, the microcomputer system 13 includes analog / digital converters 12a and 12a.
b, 12c, 12d, connected to an adder 14 that adds the detected values from these analog-to-digital converters 12a, 12b, 12c, 12d to calculate the total load. It is connected to part 15. Further, the analog-to-digital converters 12a, 12b, 12c, 12d is connected to a changing direction discriminating section 16 having a memory as a changing direction discriminating means, and the changing direction discriminating section 16 functions as a drift detecting means. It is connected to the arithmetic processing unit 15 included therein. Further, the microcomputer system 13 displays a weight and the like and has a function as an alarm means.
18 and keyboard for input with test switch 17
Are connected. A test value output section 19 as a test value output means is connected to each of the amplifiers 11a, 11b, 11c and 11d.

Next, the operation of the above embodiment will be described with reference to the flowchart shown in FIG.

First, it is initialized by turning on the power (step).

Next, at the time of weighing, the object to be measured is placed on the tray 7 and detected by the strain of each load cell 2a, 2b, 2c, 2d, and the output detection value is detected by each amplifier 11a, 11b, 11c, 11d. After amplification, the analog / digital converters 12a, 12b, 12c, 12d convert the analog signals into digital signals, and the data D ₁ (t) ~ D
₄ (t) is obtained (step).

In addition, D ₁ (t), D is stored in each memory of the change direction determination unit 16.
₂ (t), D ₃ (t) and D ₄ (t) are stored (step). Then, the sum S of the detected values by the adder 14
Let (t) be _St (t) = D ₁ (t) + D ₂ (t) as shown in Table _1.
It is calculated from + D ₃ (t) + D ₄ (t) (step).

Next, in the changing direction discriminating unit of the microcomputer system 13, the present data D _{n for} each load cell 2a, 2b, 2c, 2d.
The data D _n (t-1) one sample before is subtracted from (t) to obtain the first from d _n (t) = D _n (t) -D _n (t-1).
Obtain d _n (t) shown in the table (step). In this case, data is accepted as a predetermined count number, for example, when there is a change of 2 counts or more, the data is changed.
If the change is less than the count, do not import the data.

When d _n (t)> 0, dan (t) = 2, when d _n (t) <0, dan (t) = 1, and when d _n (t) = 0, dan (t) = 1 (T) = 0 is set, and is stored in the changing direction discriminating unit 16 as shown in Table 2 (step). Then, these d ₁ (t) to d ₄
(T) is added and P _t (t) = da ₁ (t) + da ₂ (t) +
P _t (t) is calculated from da ₃ (t) + da ₄ (t) (step).

Here, the value of the P _t (t) is, (1) when P _t (t) = 8, change load in an increasing direction, (2) 4 <When P _t (t) <8, due to drift Change, (3) When P _t (t) = 4 and P ₁ (t) × P ₂ (t) × P ₃ (t) × P ₄ (t) = 1,
When the load changes in a decreasing direction (4) P _t (t) = 4 and P ₁ (t) × P ₂ (t) × P ₃ (t) × P ₄ (t) ≠ 1,
Change due to drift, (5) Change due to drift when O <P _t (t) <4, (6) No change when P _t (t) = 0. .

Further, the difference between the current total weight value S _t (t) and the weight value S _t-1 (t-1) one sampling before is obtained (step).

Then, it is judged whether or not P _t (t) = 8 (step). When P _t (t) = 8, it is considered that the weight increases normally, so W _t (t) = St (t) And (step), P
_{When t} (t) = 8 is not satisfied, it is determined whether 4 <P _t (t) <8 (step). Here, when 4 <P _t (t) <8, it is considered that the change is caused by drift.
_t (t) = _St-1 (t-1) (step), 4 < _Pt
If (t) <8 is not satisfied, then it is determined whether _Pt (t) = 4 (step). When P _t (t) = 4, da ₁ (t) × da ₂ (t) × da ₃ (t) × d.
Determine whether a ₄ (t) = 1 (step), da
_{When 1} (t) × da ₂ (t) × da ₃ (t) × da ₄ (t) = 1, it is considered that the weight has decreased, so W _t (t) = S
_{Let t} (t) (step). Also, when not _{P t (t) = 4,} 0 < it is determined whether the P _{t (t)} <4 (step), when the _{0 <P t (t) <} 4, da in step ₁ (t) × da ₂ (t) × da ₃ (t) × da ₄ (t) = 1
If not, it is considered that the change is caused by drift, so Wt (t) = St _-1 (t-1) is set (step). Further, when 0 <P _t (t) <4 is not satisfied, it is considered that there is no change, so W _t (t) = S _t-1 (t-1) is set (step). And set by step, step, step, step or step
W _t (t) is displayed (step), the process returns to the step again, and is repeated every predetermined time.

Here, P _t (t) is set in Table 3 as follows, for example.

P ₁ (1): 0 <4 P ₂ (2): 0 <4 P ₃ (3): 0 <4 P ₄ (4): 8 P ₅ (5): 0 P ₆ (6): 8 P ₇ (7): 0 In this case, P ₁ (1), P ₂ (2) and P ₃ (3) change due to drift, P ₄ (4) and P ₆ (6) increase, P
_{Since 5} (5) and P ₇ (7) are considered unchanged,
As shown in FIG. 5, it changes only at P ₄ (4) and P ₆ (6), and it changes at P ₁ (1), P ₂ (2), P ₃ (3) and P
_{When 7} (7), U _t (t) does not change, and changes due to drift can always be corrected to zero.

If you want a price for weight, use the keyboard 17
The unit price is input by, the multiplication is performed by the arithmetic processing unit 15 of the microcomputer system 13, and the weight and the price are displayed on the display 18.

Further, when performing a test with the test switch, the test is instructed by the test switch of the keyboard 17 and no load is applied to each load cell 2a, 2b, 2c, 2d. Then, the output at this time is discriminated by the change direction discriminating unit 16, and P _t (t) =
8 and P _t (t) = 4 and da ₁ (t) × da ₂ (t) ×
When da ₃ (t) × da ₄ (t) = 1, it should be unchanged, but since it is changing, it is detected that it has drifted in the same direction. 11b, 11c,
11d or analog / digital converter 12a, 12b, 12c, 1
The drift due to 2d can be inspected.

〔The invention's effect〕

According to the load cell balance of claim 1, the changing direction determining means determines the changing direction of the detection value output from each load cell, and when the changing direction of the detection value of each load cell is not constant, the weight value is detected by the drift detecting means. Does not change, it is possible to suppress the zero point change due to drift.

Further, according to the load cell balance of the second aspect, when the output from the analog / digital conversion means is equal to or more than the predetermined count, the changing direction determining unit determines the changing direction, so that a minute change is not detected and is stable. And can cope with drift.

Further, according to the load cell balance of the third aspect, when an instruction is given by the test switch, the alarm is issued by the alarm means when the changing direction is constant, so that the drift can be easily found.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the load cell of the present invention, FIG. 2 is a perspective view of the same as above, FIG. 3 is a flow chart of the same as above, and FIG. 4 is a graph showing weight with and without correction. . 2a, 2b, 2c, 2d ... load cell, 12a, 12b, 12c, 12d ... analog-digital converter as analog-digital conversion means, 15 ... arithmetic processing section having a function as drift detection means, 16 ... Change direction determination unit as change direction determination means, 17 ... Keyboard having test switch,
18 ... Display as alarm means, 19 ... Test output section as test value output means.

Front page continuation (72) Inventor Koji Izumida 6-78 Minamimachi, Mishima-shi, Shizuoka Tokyo Electric Co., Ltd. Mishima factory (72) Inventor Ryuji Yamashita 6-78 Minamimachi, Mishima-shi, Shizuoka Tokyo Electric Co., Ltd. Mishima factory (72) Inventor Shinichi Mori 6-78 Minamimachi, Mishima City, Shizuoka Prefecture, Mishima Plant, Tokyo Electric Co., Ltd. (56) References JP-A-58-75035 (JP, A) JP-A-62-228121 (JP, A)

Claims (3)

[Claims] 1. A load cell balance for calculating a weight value by adding detection values according to weights output from a plurality of load cells, and a change for discriminating a direction in which the detection values output from each load cell change with time. A load cell balance comprising: a direction determining unit; and a drift detecting unit that does not change the weight value when the changing direction of the detected value of each load cell determined by the changing direction determining unit is not constant. 2. An analog / digital conversion means for analog / digital converting the detection value output from each load cell is provided, and the change direction determination means determines a change by counting a predetermined number of the analog / digital conversion means. The load cell balance according to claim 1, wherein 3. A test switch for instructing a state in which no load is applied to each load cell, and an alarm means for issuing an alarm, and when the test switch is instructed, the change direction is determined by the change direction determination means. The load cell balance according to claim 1 or 2, wherein an alarm is issued by an alarm means when it is determined not to be.