JPH11201838A - Load cell and method for compensating temperature of load cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a load cell which compensates effectively a primary component and a secondary component of temperature characteristic of zero point. SOLUTION: A nickel line 8 affecting mainly a primary component of temperature characteristic of zero point of a load cell and a copper wire 7 affecting mainly a secondary component of the temperature characteristic of zero point similarly are prepared. An output voltage of a bridge circuit 1 at the time of a no-load is measured at three points on sides of specified low and high temperatures and near a normal temperature located at a middle point of the both, and an upper copper wire 7 is added to a specified position of the bridge circuit 1 so that a difference between a differential amount between an output value on the high temperature side at a high temperature side measuring point and a normal temperature output value at a normal temperature measuring point; and a differential amount between a normal temperature output value at a normal temperature measuring point and an output value on the low temperature side at a low temperature side measuring point is set in the specified allowable range. Next, the other nickel wire 8 is added to a specified position of the bridge circuit 1 so that a differential amount between the high temperature side output value and the low temperature side output value is set in the specified allowable range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load cell used for an electronic balance and the like, and a temperature compensation method for the load cell, and belongs to the field of load measurement technology.

[0002]

2. Description of the Related Art In some cases, a load cell A as shown in FIG. 11 is used as a load detector in an electronic balance. This load cell A has a hollow rectangular parallelepiped strain-generating body F composed of two beam parts D and E provided vertically parallel between a fixed rigid body B at one end, a movable rigid body C at the other end, and rigid bodies at both ends. And strain gauges G1, G provided on the surfaces of the strain-generating portions D1, D2, E1, E2 of the strain-generating body F in which the thicknesses of the beam portions D, E are reduced, and converting the strain into electric signals.
2, G3 and G4.

As shown in FIG. 12, a bridge circuit H is formed by using these strain gauges G1, G2, G3 and G4, and a constant voltage Vin is applied to one of two sets of opposing vertices. The output voltage Vout of the other set in the state is extracted as a load detection signal.

According to the load cell A, the movable rigid portion C
When a load is applied to the strain generating portions D1, D2, E1, E
2 occurs, and the output voltage Vou corresponding to the distortion is generated by a change in the resistance value of the strain gauges G1, G2, G3, G4.
t will be detected.

Incidentally, this type of load cell has a property that the output voltage Vout changes due to a change in ambient temperature even when there is no load (hereinafter referred to as a zero-point temperature characteristic). Therefore, when the electronic device is incorporated in an electronic balance or the like as it is, there is a problem that the zero point fluctuates due to a change in ambient temperature, and a measurement error occurs.

In order to solve this problem, conventionally, for example, the following method has been used to compensate for the temperature characteristic of the zero point.

That is, a constant voltage Vin is applied to the bridge circuit H.
Is applied, a predetermined low-temperature side measurement point Tl (for example,
The no-load output voltage Vout is measured at −10 ° C.) and the high-temperature side measurement point Th (for example, 50 ° C.). In this case, the output voltage Vout (= Vl) at no load at the low-temperature measurement point Tl and the output voltage Vout (= Vh) at no-load at the high-temperature measurement point Th are plotted on the horizontal axis with respect to temperature, for example, in FIG. , The temperature characteristic of the zero point of the load cell A is approximated by a straight line I passing between the two points, and the low-temperature no-load output value Vl is subtracted from the high-temperature no-load output value Vh. The calculated value (Vd = Vh-Vl) is defined as the “total drift amount” of the load cell A.
Then, the temperature compensation resistor J made of copper or nickel and having a predetermined resistance value is provided at a predetermined position of the bridge circuit H as shown by a two-dot chain line in FIG. 12 so that the total drift amount Vd falls within a predetermined allowable range. Is added.

As a result, for example, as shown by a solid line in FIG. 14, a graph plotting the high-temperature-side no-load output value Vh and the low-temperature-side no-load output value Vl after the temperature compensation becomes substantially horizontal, and the difference between the two is obtained. Is within a predetermined allowable range (for example, ± 3 μV), and the zero point fluctuation is suppressed.

[0009]

However, when the temperature characteristic of the zero point before the temperature compensation of the load cell includes a second-order component with respect to the temperature as shown by a two-dot chain line in FIG. 13, for example, the following problem occurs. Can occur.

That is, when the secondary component amount is large,
As shown in FIG. 15, even if the high-temperature-side no-load output value Vh and the low-temperature-side no-load output value Vl after the temperature compensation fall within the allowable range, there is no load around 20 ° C. which is a normal use temperature. Output voltage Vout greatly changes, which may not be suitable for practical use.

Accordingly, the present invention provides one of the zero point temperature characteristics.
It is an object to provide a load cell in which a second-order component and a second-order component are effectively compensated.

[0012]

Means for Solving the Problems In order to solve the above problems, the present invention is characterized in that it is configured as follows.

That is, in the invention according to claim 1 of the present application (hereinafter, referred to as a first invention), an output voltage of a bridge circuit composed of a plurality of strain gauges fixed to a flexure element is extracted as an output signal. In the load cell, a first component that affects a first-order component of a temperature characteristic of a zero point of the output voltage.
The bridge circuit is set so that the difference between the high-temperature side no-load output value at a predetermined high-temperature side measurement point and the low-temperature side no-load output value at a predetermined low-temperature side measurement point falls within a predetermined allowable range. And a second compensating resistor which affects the second-order component of the temperature characteristic of the zero point is connected to a high-temperature-side no-load output value at the high-temperature-side measurement point and a normal-temperature non-load value at a predetermined normal-temperature measurement point. The difference between the load output value and the difference between the normal temperature no-load output value at the normal temperature measurement point and the low temperature no-load output value at the low temperature measurement point falls within a predetermined allowable range. Preferably, the bridge circuit is added to a predetermined position of the bridge circuit.

According to a second aspect of the present invention, there is provided a load cell in which an output voltage of a bridge circuit composed of a plurality of strain gauges fixed to a flexure element is taken out as an output signal. The first compensating resistor which mainly affects the primary component of the temperature characteristic of the zero point of the output voltage is connected to a high-temperature no-load output value at a predetermined high-temperature measurement point and a low-temperature non-load value at a predetermined low-temperature measurement point. A second compensating resistor, which is added to a predetermined position of the bridge circuit so that a difference amount from the load output value falls within a predetermined allowable range, and mainly affects a secondary component of the temperature characteristic of the zero point, The difference between the high-temperature side no-load output value at the high-temperature side measurement point and the normal-temperature no-load output value at a predetermined normal temperature measurement point, the normal-temperature no-load output value at the normal temperature measurement point, and the low-temperature side measurement point Definitive as the difference between the difference amount between the low-temperature side no-load output value is within a predetermined permissible range, characterized in that added to the predetermined position of the bridge circuit.

The invention according to claim 3 (hereinafter referred to as third invention)
The invention is characterized in that in the load cells of the first and second inventions, nickel is used as the first compensation resistor and copper is used as the second compensation resistor.

On the other hand, the invention according to claim 4 of the present application (hereinafter referred to as the invention)
The fourth invention) relates to a load cell temperature compensation method for suppressing a zero-point temperature characteristic of an output voltage of a bridge circuit composed of a plurality of strain gauges fixed to a flexure element. The first that affects the primary component
A compensating resistor and a second compensating resistor that also affects the second-order component of the temperature characteristic of the zero point are prepared, and the high-temperature side no-load output value at a predetermined high-temperature side measurement point and the predetermined normal temperature measurement point The difference between the normal temperature no-load output value and the difference between the normal temperature no-load output value at the normal temperature measurement point and the low temperature no-load output value at the predetermined low temperature side measurement point is within a predetermined allowable range. The second compensation resistor is added to a predetermined position of the bridge circuit so that the difference between the high-temperature-side no-load output value and the low-temperature-side no-load output value falls within a predetermined allowable range. The other first compensation resistor is added to a predetermined position of the bridge circuit so as to be accommodated.

The invention according to claim 5 (hereinafter referred to as a fifth invention) is a load cell for suppressing a temperature characteristic of a zero point of an output voltage of a bridge circuit constituted by a plurality of strain gauges fixed to a flexure element. The present invention relates to a temperature compensation method, in which a first compensation resistor mainly affects a first-order component of a temperature characteristic of a zero point, and a second compensation resistor mainly affecting a temperature characteristic of a zero point.
While preparing a second compensation resistor that affects the next component, the difference between the high-temperature side no-load output value at a predetermined high-temperature side measurement point and the normal temperature no-load output value at a predetermined normal temperature measurement point, The second temperature is set so that the difference between the normal temperature no-load output value at the normal temperature measurement point and the low temperature no-load output value at the predetermined low temperature side measurement point falls within a predetermined allowable range.
A compensation resistor is added to a predetermined position of the bridge circuit, and the other first compensation is performed so that the difference between the high-temperature-side no-load output value and the low-temperature-side no-load output value falls within a predetermined allowable range. A resistor is added to a predetermined position of the bridge circuit.

The invention according to claim 6 (hereinafter referred to as a sixth embodiment)
The invention relates to the load cell temperature compensation methods of the fourth and fifth inventions, wherein the temperature compensation for the secondary component of the zero point temperature characteristic using the second compensation resistor is performed by the first compensation resistor. Is performed prior to the temperature compensation for the first-order component of the zero-point temperature characteristic, and the difference between the high-temperature-side no-load output value and the normal-temperature no-load output value; Until the difference between the difference value from the side no-load output value falls within a predetermined allowable range, and the difference amount between the high temperature side no-load output value and the low temperature side no-load output value falls within a predetermined allowable range. The temperature compensation for the secondary component and the temperature compensation for the primary component are performed alternately.

Furthermore, the invention according to claim 7 (hereinafter referred to as a seventh aspect)
The invention relates to the load cell temperature compensation methods of the fourth and fifth inventions, wherein nickel is used as the first compensation resistor and copper is used as the second compensation resistor. I do.

Now, as shown in FIG.
1, a graph plotting the respective measurement results of the output voltage Vout at the normal temperature measurement point Tn (for example, 20 ° C.) and the high temperature side measurement point Th with the temperature T as a horizontal axis is the low temperature side no-load output value Vl, the normal temperature If it is indicated by a polygonal line a passing through the three points of the no-load output value Vn and the high-temperature-side no-load output value Vh, this polygonal line shows a curve A indicating the temperature characteristic of the zero point of the load cell as the low-temperature side measurement point Tl. High temperature side measurement point Th
Can be regarded as an approximation between

Here, the difference ΔVh (= Vh−Vn) between the high temperature side no-load output value Vh and the normal temperature no-load output value Vn.
Is defined as the “high-temperature-side drift amount”, and the difference ΔVl (= the difference between the normal-temperature no-load output value Vn and the low-temperature-side no-load output value Vl)
Vn−Vl) is defined as the “low temperature side drift amount”, and the low temperature side drift amount ΔV is calculated from the high temperature side drift amount ΔVh.
If the value Vc (= △ Vh- △ Vl) obtained by subtracting 1 is defined as “curvature amount” for convenience, as shown in FIG. When shown, the curvature amount Vc has a positive value. Conversely, when the curve showing the temperature characteristic of the zero point is convex upward and the broken line is convex upward, the curvature amount Vc becomes a negative value, and the high-temperature side drift amount ΔVh and the low-temperature side drift amount ΔVl
Is satisfied, and the polygonal line becomes a straight line, the curvature amount Vc becomes zero. That is, the amount of curvature Vc can be regarded as geometrically equivalent to the "curvature" in the normal temperature no-load output value Vn of the curve A indicating the temperature characteristic of the zero point. Therefore, if the curvature amount Vc falls within a predetermined allowable range, the secondary component of the temperature characteristic at the zero point is suppressed.

The difference Vd (= Vh-Vl) between the high-temperature-side no-load output value Vh and the low-temperature-side no-load output value Vl is given by:
Since it is defined as the total drift amount of the load cell, if this total drift amount Vd falls within an allowable range,
The first-order component of the zero-point temperature characteristic is also suppressed.

As a result, the temperature characteristic of the zero point of the load cell becomes flat over the entire range from the low-temperature side measurement point Tl to the high-temperature side measurement point Th, so that high measurement accuracy can be obtained.

As described above, according to the first aspect, the first compensating resistor which affects the first-order component of the temperature characteristic of the zero point,
Similarly, a load cell with little zero point fluctuation can be obtained only by adding a second compensating resistor, which similarly affects the secondary component of the zero point temperature characteristic, to a predetermined position of the bridge circuit.

According to the second aspect of the present invention, the first compensating resistor which mainly affects the first-order component of the temperature characteristic of the zero point,
Similarly, by simply adding a second compensating resistor, which mainly affects the secondary component of the temperature characteristic of the zero point, to a predetermined position of the bridge circuit, a load cell with a small zero point fluctuation can be obtained in the same manner as in the first invention. Become.

According to the third invention, when the nickel is used as the first compensation resistor and the copper is used as the second compensation resistor, the effects of the first and second inventions can be obtained. become.

On the other hand, according to the fourth aspect, the first compensating resistor that affects the primary component of the zero-point temperature characteristic, and the second compensating resistor that also affects the secondary component of the zero-point temperature characteristic, Is added to the predetermined position of the bridge circuit, it is possible to effectively compensate for both the first and second components of the temperature characteristic of the zero point of the load cell.

According to the fifth aspect of the present invention, the first compensating resistor which mainly affects the primary component of the temperature characteristic of the zero point,
Similarly, by adding a second compensating resistor, which mainly affects the second-order component of the temperature characteristic of the zero point, to a predetermined position of the bridge circuit, one component of the temperature characteristic of the zero point of the load cell and the second component are added similarly to the fourth invention. Both of the secondary components can be effectively compensated.

In any of the fourth and fifth aspects of the present invention, the output voltage of the load cell when there is no load is measured only at three points near the normal temperature, which is located between the low temperature side, the high temperature side, and between them. Both the primary component and the secondary component of the temperature characteristic of the zero point of the load cell can be easily and accurately suppressed.

According to the sixth aspect, the temperature compensation for the second-order component of the zero-point temperature characteristic using the second compensation resistor is performed for the first-order component of the zero-point temperature characteristic using the first compensation resistor. Since the temperature compensation is performed prior to the temperature compensation, the temperature compensation for the secondary component is effectively performed.

Further, according to the seventh invention, when nickel is used as the first compensation resistor and copper is used as the second compensation resistor, the effects of the fourth and fifth inventions can be obtained. become.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A load cell temperature compensating method according to an embodiment of the present invention will be described below.

The following description relates to the load cell temperature compensating method according to the present invention. The load cell in which the compensating method is implemented is an embodiment of the load cell according to the present invention.

That is, although not shown, the flexure element of the load cell in which the temperature compensation method according to the present embodiment is performed has the same configuration as that of the conventional example shown in FIG.
Strain gauges provided on the surface of each strain generating portion of the strain generating element are connected, for example, as shown in FIG.

That is, the bridge circuit 1 is connected to each other at the connection points j1, j2, j3, j4 such that the four strain gauges R1, R2, R3, R4 are located on each side of the square. , Two sets of connection terminals 2, 2, 3, 3 for additionally connecting a compensation resistor near the connection point j2 on the bridge side where the strain gauge R2 is provided, are arranged in series,
Also, a connection point j on the bridge side where the strain gauge R4 is provided.
Two sets of connection terminals 4, 4, 5, and 5 for additionally connecting a compensation resistor closer to the second side are arranged in series.
The connection terminals 2, 2, 3, 3, 4, 4, 5 and 5 are connected in advance by wiring members 6.

A constant voltage Vi is applied to the connection points j1 and j3.
n is applied, and the output voltage Vout is output from the connection points j2 and j4.
The circuit is configured so that is extracted.

Next, the temperature compensation method according to the present embodiment will be described.

First, the load cell is set in a constant temperature bath, and the output voltage Vout under no load when a constant voltage Vin (for example, 12 V) is applied to the bridge circuit 1 is measured at a predetermined low-temperature side measurement point Tl (for example, -10 ° C.), at the high-temperature side measurement point Th (for example, 50 ° C.), and at around room temperature (for example, 20 ° C.) which is located between the two.

Then, the output value Vh at no load on the high temperature side at the measurement point Th on the high temperature side, the output value Vl at no load on the low temperature side at the low temperature measurement point Tl, and the output value Vn at normal temperature at the normal temperature measurement point Tn are shown below. By substituting into the relational expressions (1) and (2), the total drift amount Vd and the curvature amount Vc are calculated respectively.

Vd = Vh−V1 (1) Vc = (Vh−Vn) − (Vn−V1) (2) Here, (Vh−Vn) of the first item on the right side of the above equation (2)
Indicates the above-mentioned high-temperature side drift amount ΔVh, and similarly, the second item on the right side (Vn−Vl) indicates the above-mentioned low-temperature side drift amount ΔVl.

In this case, the low-temperature side no-load output value Vl,
Normal temperature no-load output value Vn and high temperature side no-load output value Vh
Assuming that the temperature characteristic of the zero point passing through the three points has a downwardly convex characteristic as shown by the broken line in FIG. 3, both the entire drift amount Vd and the curvature amount Vc have positive values.

Now, in the bridge circuit shown in FIG. 4, a voltage change ΔV when the temperature compensation resistor Rx changes by ΔR due to a temperature change is given by the following equation (3).

ΔV = ΔR · Vin / (4 · Rg) (3) Further, the temperature coefficient of resistance (TCR) of the temperature compensation resistor Rx is α
Then, the resistance change △ R when the temperature changes by △ T
Is represented by the following equation (4).

ΔR = α · Rx · ΔT (4) Therefore, the output compensation ΔV of the load cell when the temperature changes by ΔT (total drift amount Vd) The value is calculated by the above equation (3),
It is given by the following equation (5) obtained from (4).

Rx = 4 · ΔV · Rg / (ΔT · α · Vin) (5) On the other hand, in a state where the applied voltage is set to 12 V, a resistance value required to change the curvature amount Vc by 1 μV Is a copper wire (resistance value per unit length: 0.54 Ω / m, TCR: 3900 pp), for example, when the resistance values of the strain gauges R1, R2, R3, and R4 are 350Ω.
m / ° C) is about 0.014Ω,
When a nickel wire (resistance value per unit length: 1.66 Ω / m, TCR: 5060 ppm / ° C.) is used as the compensation resistor, the value is about 0.036 Ω, and the curvature of the copper wire is higher than that of the nickel wire. The amount Vc can be largely changed. Therefore, a nickel wire is selected as the first compensation resistor, and a copper wire is selected as the second compensation resistor.

As for the relationship between the total drift amount Vd and the curvature amount Vc, when the total drift amount Vd is changed to the plus side, the curvature amount Vc changes to the minus side, and conversely, the total drift amount Vd is changed to the minus side. , The curvature amount Vc changes to the plus side.

Based on such a relationship, the curvature Vc (second-order component) is compensated using a copper wire as the first step. In this case, since the broken line corresponding to the characteristic curve is convex downward and the curvature amount Vc is positive as shown in FIG. 3, the wiring member 6 is connected between the connection terminals 5 and 5 in the bridge circuit 1 of FIG. After removal, a copper wire having a predetermined resistance value is connected. Here, as described above, the resistance value required to change the curvature amount Vc by 1 μV is about 0.014 Ω. For example, when the curvature amount Vc is 2 μV, the resistance value used is about 0 μm. .028Ω. Thereby, the curvature amount Vc (second order component) is compensated as shown in FIG. 5, and the characteristic curve becomes linear. When the curvature amount Vc is minus,
A copper wire will be connected between the connection terminals 3 and 3.

In the second stage, in order to remove the influence of the addition of the copper wire and the total drift amount Vd on the total drift amount Vd, a nickel wire is connected between the connection terminals 2 and 2 in the bridge circuit 1 by a wiring material. After removing 6, a nickel wire having a predetermined resistance value is connected. The resistance value in that case is calculated by the above equation (5).

On the other hand, when the value obtained by adding the total drift amount Vd and the effect on the total drift amount Vd due to the addition of the copper wire is a negative value, a nickel wire is connected between the connection terminals 4 and 4 of the bridge circuit 1. Connecting.

When the curvature amount Vc deviates from an allowable range (for example, ± 1.5 μV) when a nickel wire is connected, a copper wire is additionally connected so as to compensate for the deviation.

By repeating such a procedure, as shown in FIG. 6, the copper wire is connected with the copper wire until the temperature characteristic at the zero point becomes flat over the entire range from the low-temperature measurement point Tl to the high-temperature measurement point Th. Nickel wires are connected alternately.

As shown in FIG. 7, when the copper wire 7 and the nickel wire 8 are connected to the bridge circuit 1 and the temperature characteristics as shown in FIG. 6 are obtained, the total drift amount Vd and the curvature are obtained. Both the amount Vc and the amount Vc fall within a predetermined allowable range.

FIG. 8 shows an example of a simulation result using the temperature compensation method according to the present embodiment.

That is, the curvature amount Vc is larger than that before the temperature compensation.
Is within ± 1 μV, and the total drift amount V
d is also greatly improved.

Here, in this embodiment, a copper wire and a nickel wire are used as the compensation resistors. However, the compensation resistors are not limited to wires, but may be chip resistors, foil resistors, or thin films. It is also possible to use resistors.

When a foil or thin film resistor is used as a compensation resistor, a resistor pattern is formed using these resistors, and these patterns are replaced by bridges instead of the wiring members 6 shown in FIG. The resistance value of the resistor pattern may be incorporated in the circuit 1 in advance and changed by trimming during temperature compensation. In this case, for example, the connection terminals 2 and 2 and the connection terminals 4 and 4 have a first compensation resistor pattern, and the connection terminals 3 and 3 and the connection terminals 5 and 5 have a second compensation resistor pattern. Will be incorporated.

The circuit configuration of the bridge circuit 1 is shown in FIG.
May be changed as shown in FIG. In that case, two sets of connection terminals 2 ′, 2 ′, for additionally connecting a compensation resistor near the connection point j4 on the bridge side where the strain gauge R3 is provided.
2 ′, 3 ′, 3 ′ are arranged in series, and the strain gauge R
2 sets of connection terminals 4 ′, 4 ′ for additionally connecting a compensation resistor near the connection point j 4 on the bridge side where 1 is provided;
5 ′, 5 ′ are arranged in series. In this case, also in this case, the connection terminals 2 ', 2', 3 ',
3 ', 4', 4 ', 5', 5 'are connected in advance by wiring members 6 ... 6.

Next, still another embodiment of the load cell according to the present invention will be described.

That is, as shown in FIG. 10, for example, the load cell 10 according to this embodiment is provided vertically parallel between a fixed rigid body 11 at one end, a movable rigid body 12 at the other end, and rigid bodies at both ends. It has a hollow rectangular parallelepiped strain generator 15 composed of two beam sections 13 and 14, and the upper and lower two beam sections 13 and 14 in the strain generator 15 are respectively provided at two locations in the longitudinal direction. Flexure portion 13 with reduced thickness
a, 13b, 14a and 14b are provided.

In this embodiment, the strain generating portion 13 of the upper beam portion 13 in the strain generating body 15 is used.
For example, the four strain gauges R1, R2, R constituting the bridge circuit 1 shown in FIG.
3, R4 are provided. In this case, for example, a strain gauge R is provided on the strain-generating portion 13a located on the fixed rigid body portion 11 side.
1 and R4 are provided in parallel in the width direction, and a strain gauge R is provided on a strain-generating portion 13b located on the other movable rigid body portion 12 side.
2, R3 are provided in parallel in the width direction. Then, these strain gauges R1, R2, R3, R4 are connected to the connection points j1, j so as to be located on each side of the square as shown in FIG.
2, j3, j4, and two pairs of connection terminals 2, 2, 3, for additionally connecting a compensation resistor near the connection point j2 on the bridge side where the strain gauge R2 is provided.
3 are arranged in series, and two sets of connection terminals 4, 4, 5 and 5 for additionally connecting a compensation resistor are arranged in series near the connection point j2 on the bridge side where the strain gauge R4 is provided. Configuration.

In the load cell 10 according to this embodiment, temperature compensation is performed by the above-described method.

Incidentally, four strain gauges R1, R2, R3, R4 may be provided on the surface of the strain generating portions 14a, 14b of the lower beam portion 14 in the strain generating body 15. In this case, for example, the strain gauges R1 and R4 are provided in parallel in the width direction on the strain generating portion 14a located on the fixed rigid portion 11 side, and the strain generating portion 14b positioned on the other movable rigid portion 12 side. , Strain gauges R2 and R3 are provided in parallel in the width direction.

[0063]

As described above, according to the present invention, since the primary component and the secondary component of the temperature characteristic at the zero point of the load cell are suppressed, the temperature characteristic becomes flat over a wide range of the normal use temperature range. Thus, a load cell corrected in characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a relationship between a temperature and an output voltage under no load for explaining the principle of the method of the present invention.

FIG. 2 is a diagram illustrating a bridge circuit of a strain gauge used in the load cell according to the embodiment;

FIG. 3 is a diagram showing a relationship between a temperature before temperature compensation and an output voltage at no load.

FIG. 4 is a diagram for explaining a method of calculating a resistance value when a temperature compensation resistor is connected to a bridge circuit.

FIG. 5 is a diagram illustrating a relationship between a temperature in an intermediate stage of temperature compensation and an output voltage at no load.

FIG. 6 is a diagram showing a relationship between a temperature after temperature compensation and an output voltage at no load.

FIG. 7 is a diagram showing a bridge circuit after temperature compensation.

FIG. 8 is a table showing simulation results of temperature compensation.

FIG. 9 is a diagram showing a bridge circuit of a strain gauge used in a load cell according to another embodiment.

FIG. 10 is a perspective view showing a load cell according to still another embodiment.

FIG. 11 is a perspective view showing a conventional load cell.

FIG. 12 is a diagram showing a bridge circuit of a strain gauge used in a conventional load cell.

FIG. 13 is a diagram showing a relationship between a temperature before temperature compensation and an output voltage at no load in a conventional load cell.

FIG. 14 is a diagram showing a relationship between a temperature after temperature compensation and an output voltage at no load in a conventional load cell.

FIG. 15 is an explanatory diagram of a conventional problem.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bridge circuit 7 Copper wire 8 Nickel wire R1-R4 Strain gauge

Claims (7)

[Claims] 1. A load cell for taking out an output voltage of a bridge circuit composed of a plurality of strain gauges fixed to a flexure element as an output signal, wherein a first-order component of a temperature characteristic of a zero point of the output voltage is obtained. The first compensating resistor that influences the difference between the high-temperature no-load output value at a predetermined high-temperature measurement point and the low-temperature no-load output value at a predetermined low-temperature measurement point falls within a predetermined allowable range. The second compensating resistor, which is added to a predetermined position of the bridge circuit and affects the secondary component of the temperature characteristic of the zero point, as described above, is connected to the high-temperature side no-load output value at the high-temperature side measurement point by a predetermined value. The amount of difference between the output value at normal temperature and no load at the normal temperature measurement point,
The bridge circuit is added to a predetermined position of the bridge circuit so that the difference between the output value at normal temperature at no load and the output value at normal temperature at no load and the low temperature output value at low temperature at no load falls within a predetermined allowable range. A load cell, wherein 2. A load cell for taking out an output voltage of a bridge circuit composed of a plurality of strain gauges fixed to a flexure element as an output signal, wherein a primary component of a temperature characteristic of a zero point of the output voltage is mainly included. The first compensating resistor that influences the difference between the high-temperature no-load output value at a predetermined high-temperature measurement point and the low-temperature no-load output value at a predetermined low-temperature measurement point falls within a predetermined allowable range. A second element, which is added to a predetermined position of the bridge circuit so as to be contained and affects mainly a secondary component of the temperature characteristic of the zero point.
The compensation resistor has a difference between the high-temperature side no-load output value at the high-temperature side measurement point and the normal-temperature no-load output value at a predetermined normal temperature measurement point, and the normal-temperature no-load output value at the normal temperature measurement point. A load cell, wherein the load cell is added to a predetermined position of the bridge circuit so that a difference between the low-temperature side no-load output value and a low-temperature side no-load output value falls within a predetermined allowable range. 3. The load cell according to claim 1, wherein nickel is used as the first compensation resistor and copper is used as the second compensation resistor. . 4. A load cell temperature compensation method for suppressing a zero-point temperature characteristic of an output voltage of a bridge circuit constituted by a plurality of strain gauges fixed to a flexure element. A first compensating resistor that affects the temperature and a second compensating resistor that also affects the second-order component of the temperature characteristic of the zero point are prepared. The difference between the normal temperature no-load output value at the normal temperature measurement point and the difference between the normal temperature no-load output value at the normal temperature measurement point and the low-temperature no-load output value at the predetermined low-temperature measurement point. The second compensation resistor is added to a predetermined position of the bridge circuit so that the value falls within a predetermined allowable range, and the difference between the high-temperature-side no-load output value and the low-temperature-side no-load output value is reduced. Others within the specified tolerance Wherein the first compensation resistor is added to a predetermined position of the bridge circuit. 5. A load cell temperature compensation method for suppressing a zero-point temperature characteristic of an output voltage of a bridge circuit constituted by a plurality of strain gauges fixed to a flexure element, wherein a primary component of the zero-point temperature characteristic is mainly provided. And a second compensating resistor, which also affects the second-order component of the temperature characteristic of the zero point, and outputs a high-temperature-side no-load output value at a predetermined high-temperature-side measurement point. And the difference between the normal-temperature no-load output value at the predetermined normal-temperature measurement point, and the difference between the normal-temperature no-load output value at the normal-temperature measurement point and the low-temperature no-load output value at the predetermined low-temperature measurement point. The second compensation resistor is added to a predetermined position of the bridge circuit so that the difference between the two falls within a predetermined allowable range, and the difference between the high-temperature side no-load output value and the low-temperature side no-load output value is added. Volume is within specified tolerance A temperature compensation method for a load cell, characterized in that the other first compensation resistor is added to a predetermined position of the bridge circuit so as to fall within the range. 6. The temperature compensation for the second-order component of the zero-point temperature characteristic using the second compensation resistor is performed prior to the temperature compensation for the first-order component of the zero-point temperature characteristic using the first compensation resistor. Together, the difference between the high-temperature no-load output value and the normal-temperature no-load output value and the difference between the normal-temperature no-load output value and the low-temperature no-load output value are within a predetermined allowable range. The temperature compensation for the second-order component and the temperature compensation for the first-order component are alternately performed until the temperature falls within a predetermined allowable range and the difference between the high-temperature side no-load output value and the low-temperature side no-load output value falls within a predetermined allowable range. 6. The temperature compensation method for a load cell according to claim 4, wherein the temperature compensation is performed. 7. The temperature compensation method for a load cell according to claim 4, wherein nickel is used as the first compensation resistor, and copper is used as the second compensation resistor. .