JP5583428B2 - Dummy load cell - Google Patents

Description

  The present invention relates to a dummy load cell used to compensate for noise caused by a vibration signal superimposed on a load signal of a load cell.

  The load cell is used by being attached to the measuring instrument body. When the installation base surface on which the measuring device main body is installed vibrates under the influence of some vibration source, the basic vibration force is transmitted to the load cell via the measuring device main body. Therefore, the load cell vibrates, and the basic vibration signal is superimposed as noise on the load signal of the load cell.

  As a countermeasure against attenuation of the fundamental vibration signal, a dummy load cell may be used together with a load cell used for weight measurement. The dummy load cell is arranged in the vicinity of the weight measuring load cell. The dummy load cell is formed so as to have a dynamic characteristic substantially equal to the dynamic characteristic of the weight measurement load cell in a state where the weighing table or the measurement container is attached to the weight measurement load cell. Therefore, the amplitude and phase of the basic vibration signal superimposed on the weight measurement signal output from the weight measurement load cell are substantially equal to the amplitude and phase of the basic vibration signal output from the dummy load cell. Accordingly, by subtracting the output signal for the dummy load cell from the output signal of the weight measurement load cell, the fundamental vibration signal component contained in the output signal of the weight measurement load cell can be removed.

  Such dummy load cells are, for example, manufactured as parallelogram load cells as shown in FIG. 1 of JP-A-6-317457 and FIG. 1 of JP-A-8-114493. In the vicinity of the load cell for gravity measurement. The dummy load cell may be manufactured so that the ratio between its equivalent mass and the spring constant is equal to the ratio between the equivalent weight of the weight measuring load cell and the spring constant, so that the equivalent mass and the spring constant can be reduced. It is possible to make the dummy load cell smaller than the load cell for weight measurement.

  However, it is expensive to manufacture and install a dummy load cell separately from the load measuring load cell. Furthermore, in the measuring instrument, there is often no installation space for the dummy load cell in the vicinity of the installation location of the weight measurement load cell, and it is difficult to select an appropriate installation location. Depending on the mounting location, it may not be possible to apply a fundamental vibration having the same amplitude and phase as the weight measuring load cell to the dummy load cell. A dummy load cell must be attached separately from the load cell for weight measurement, which is expensive. There are various problems like this.

  In view of this, there is one in which a dummy load cell is integrally formed with a strain-generating body for weight measurement as shown in FIG. In this dummy load cell, the strain generating portion is constituted by a single beam.

JP-A-8-114494

  The basic vibration force transmitted from the measuring instrument main body to the load cell mounting portion does not necessarily act in the vertical direction, and may act in the direction of twisting the load cell elastic body. Since the load cell for weight measurement has two parallel beams, it has high rigidity against the vibration force acting in the direction of twisting the load cell elastic body, so it acts in the direction of twisting to the load cell for weight measurement. The effect of vibration force is small. However, a single beam as disclosed in Patent Document 1 has low rigidity against vibration force acting in the twisting direction. Therefore, even if the direction of the vibration force is slightly inclined from the vertical direction, the strain generating portion is distorted by torsional vibration, and the dummy load cell and the weight measurement load cell output the same foundation vibration force. The amplitude and phase of the vibration signal may be different. Therefore, the fundamental vibration cannot be compensated accurately.

  An object of the present invention is to provide a dummy load cell that is inexpensive, does not require an installation space, and can accurately compensate a basic signal.

The dummy load cell of one embodiment of the present invention is provided in the weight measuring load cell. This load cell for weight measurement is a parallelogram made of a metal elastic body, and a mounting portion to the measuring instrument main body and a movable portion receiving the load of the object to be weighed are located apart from each other. The attachment portion and the movable portion are connected by two parallel beams. Strain portions are respectively formed on the two parallel beams. A load detecting means is provided in the strain generating portion . Due to the space penetrating in the thickness direction of the metal elastic body formed in the mounting part, the dummy load cell is integrated with the two parts of the weight measuring load cell in parallel with the part of the mounting part on the measuring instrument main body side. These two parallel beams are formed. A strain generating portion is formed in two parallel beams for the dummy load cells. In the mounting portion, at the tip of two parallel beams for the dummy load cell, the movable portion for the dummy load cell has two parallel beams for the dummy load cell, independently of the movable portion of the weight measuring load cell. It is formed integrally with a simple beam. Both ends of the movable portion for the dummy load cell are respectively spaced from the two parallel beam-side portions of the load measuring load cell of the mounting portion. The load cell for the dummy load cell so as to form a vibration system having substantially the same dynamic characteristics as the vibration system formed by the equivalent mass of the movable part in the load cell for weight measurement and the spring constant of the strain generating part of the load cell for weight measurement. The equivalent mass and spring constant are set.

  In the dummy load cell configured as described above, since the dummy load cell is formed in a parallelogram shape, the dummy load cell has two beams, and has high rigidity against a force acting in the direction of twisting the dummy load cell. Therefore, the strain generating part is less likely to be distorted due to torsional vibration, and the amplitude and phase of the output fundamental vibration signal are substantially the same for the dummy load cell and the weight measurement load cell for the same basic vibration force, and the basic vibration is accurately determined. Can be compensated. Moreover, since the dummy load cell is formed integrally with the load cell for weight measurement, it is possible to reduce the cost, and it is not necessary to secure the installation space for the dummy load cell, and it is not necessary to install the dummy load cell. is there. Further, since the same vibration force is applied to the dummy load cell and the weight measuring load cell, the amplitude and phase of the fundamental vibration signal component generated by both of them are substantially the same, and the fundamental vibration can be accurately compensated.

The dummy load cell according to another aspect of the present invention is also provided in the load measuring load cell. The load cell for weight measurement is also a parallelogram made of a metal elastic body, and the attachment portion to the measuring instrument main body and the movable portion receiving the load of the object to be weighed are located apart from each other. The attachment portion and the movable portion are connected by two parallel beams. Strain portions are respectively formed on the two parallel beams. A load detecting means is provided in the strain generating portion . Two beams for the dummy load cell extend from the mounting portion in parallel with the two parallel beams of the weight measuring load cell and integrally with the mounting portion. A strain generating portion is formed in two parallel beams for the dummy load cells. A load detecting means is also provided in this strain generating portion. At the ends of the two parallel beams for the dummy load cell, the movable portion for the dummy load cell is integrated with the two parallel beams for the dummy load cell independently of the movable portion of the load cell for weight measurement. Is formed. The load cell for the dummy load cell so as to form a vibration system having substantially the same dynamic characteristics as the vibration system formed by the equivalent mass of the movable part in the load cell for weight measurement and the spring constant of the strain generating part of the load cell for weight measurement. The equivalent mass and spring constant are set. The load cell for weight measurement is formed by forming the attachment portion, the two parallel beams, and the movable portion by forming a space penetrating the metal elastic body in the thickness direction. In this case, three holes penetrating in the thickness direction are formed in a row in the vicinity of the space in the mounting portion at intervals along the direction in which the load is applied to the movable portion. Of the two parallel beams, the strain-generating portion and the movable portion for the dummy load cell, by passing through the through-groove connecting the space at both ends of the load application direction in the thickness direction, It is formed. As the three through holes, those having various shapes can be used. For example, a figure of 8 or a circular shape can be used.

  If comprised in this way, a movable part can be formed between three through-holes and the space of the load cell for weight measurement, and a beam is comprised by the through-hole of the center of three through-holes, and the through-hole of the both sides, respectively. In addition, the strain-generating portion is also constituted by the through hole. Further, the beam of the dummy load cell and the movable portion can be formed in the portion that is originally the mounting portion, and it is not necessary to increase the size of the metal elastic body in order to form the dummy load cell. Is formed, and the through-groove is only provided, so that the manufacturing is easy.

  By forming the three holes at both ends in the load application direction, the strain-generating portion of the weight measuring load cell can also be formed. With this configuration, it is not necessary to separately form the strain-generating portion of the load cell for weight measurement, the manufacturing process can be reduced, and the cost can be reduced.

  The movable portion for the dummy load cell may be provided with a mass adjusting hole or a mass adjusting component. Thereby, the equivalent mass of the dummy load cell can be adjusted. Moreover, since the hole for mass adjustment or the component for mass adjustment is provided in the movable part for dummy load cells, mass adjustment can be performed easily.

  An annular groove for adjusting a spring constant may be formed on the outer periphery of at least one of the three holes. When the annular groove is formed in this way, the spring constant of the dummy load cell can be reduced, and the ratio of the equivalent mass to the spring constant can be easily made the same in the dummy load cell and the weight measuring load cell.

  Two strain-generating portions for dummy load cells can be provided for one dummy load cell beam, but only one can be provided. In the dummy load cell, no movement of the load occurs, so that no distortion stress due to the movement of the load occurs in the two beams. Accordingly, as described above, only one strain generating portion can be provided, the structure becomes simple, and the manufacture thereof becomes easy.

  As described above, according to the present invention, the basic vibration can be accurately compensated, the cost can be reduced, the installation space for the dummy load cell is not required, and the dummy load cell is attached. Is also unnecessary.

It is a front view of the load cell for weight measurement provided with the dummy load cell of the 1st Embodiment of this invention. FIG. 2 is an enlarged front view of the dummy load cell of FIG. It is a front view of the load cell for weight measurement provided with the dummy load cell of the 2nd Embodiment of this invention. It is sectional drawing which follows the front view of the load cell for weight measurement provided with the dummy load cell of the 3rd Embodiment of this invention, and the bb line and cc line in a front view. It is a partial omission front view of the load cell for weight measurement provided with the dummy load cell of the 4th Embodiment of this invention. It is a partial omission front view of the load cell for weight measurement provided with the dummy load cell of the 5th Embodiment of this invention.

  The dummy load cell 2 according to the first embodiment of the present invention is provided in a weight measuring load cell 4 as shown in FIG. The load cell 4 for weight measurement is of a parallelogram type, and a space 8 penetrating in the thickness direction is formed in a rectangular parallelepiped metal elastic body 6 having a predetermined thickness in the front and back direction of the paper surface. The mounting portion 10, the movable portion 12, the two beams 14, and the four strain generating portions 16 are formed.

  The attachment part 10 is for attaching the load cell 4 for weight measurement to an installation reference plane, for example, the measuring instrument main body 18. A movable portion 12 is arranged on the substantially same straight line as the mounting portion 10 at a distance from the mounting portion 10. The movable part 12 has a measuring table or a measuring container (not shown) attached to the surface opposite to the measuring instrument main body 18. When an object to be weighed is loaded on these weighing platforms or weighing containers, a load is applied to the movable portion 12 from the upper side to the lower side along the vertical direction in FIG. The two beams 14 connect the fixed portion 10 and the movable portion 12 at their upper and lower ends, respectively, and are positioned in parallel to each other with an interval in the vertical direction. A total of four strain-generating portions 16 are formed by reducing the thickness in the vertical direction at two locations spaced apart in the length direction of each of the beams 14. Each of the strain generating portions 16 is provided with load detecting means, for example, a strain gauge 20. Thus, in order to form the mounting portion 10, the movable portion 12, the beam 14, and the strain-generating portion 16, the front shape of the space 8 is such that both ends of the upper side of the rectangle are curved upward in an arc shape, and both ends of the lower side are downward. The shape is curved in an arc shape. Each curved portion is the same arc.

  In the dummy load cell 2, as shown in an enlarged view in FIG. 2, three through holes 22, 24, 26 are formed in the vicinity of the space 8 in the mounting portion 10, and a through groove 28 is formed in each of the through holes 22, 26. Thus, two dummy load cell beams 30a and 30b, four strain generating portions 32, and a movable portion 34 are formed to form a parallelogram shape.

  The three through holes 22, 24, and 26 are eight-shaped ones that are laid sideways, and penetrate through the metal elastic body 6 in the thickness direction. That is, the three through-holes 22, 24, and 26 have a front shape in which two circles having the same diameter are moved by a predetermined distance from a state in which both circles contact each other. The three through holes 22, 24, and 26 are arranged at a predetermined interval in a line in the load application direction of the weight measuring load cell 4, in this embodiment, in the vertical direction of FIGS. 1 and 2. The through holes 22, 24, and 26 are installed at the same distance from the end surface of the fixing portion 10 on the side opposite to the space 8. Among these three through holes 22, 24, 26, the through holes 22, 26 at both ends in the load application direction are arranged in line symmetry with the central axis of the through hole 24 (the central axis in the horizontal direction in FIG. 2) as the symmetry axis. Has been.

  A through groove 28 is formed at the end of the through holes 22 and 26 on the space 8 side. The through groove 28 is formed in a straight line so as to communicate with the space 8 and penetrates the metal elastic body 6 in the thickness direction. These through holes 28 are arranged in line symmetry with the central axis of the through hole 24 as the axis of symmetry at a position closer to the central through hole 24 side than the central axis of the through holes 22 and 24.

  By forming the through holes 22, 24, 26 and the through groove 28 in this way, a movable portion 34 independent of the movable portion 12 of the weight measuring load cell 4 is formed between the through grooves 28, and the through holes 22, 24 are formed. Forming one beam 30a, and forming the through holes 24, 26 forms the other beam 30b. A portion from the end of the through hole 22, 24, 26 on the side opposite to the space 8 in the weight measuring load cell 4 to the measuring instrument body 18 is shared as the mounting portion 10 for the weight measuring load cell 4 and the dummy load cell 2. Is done. A total of four strain generating portions 32 are formed on each of the beams 30a and 30b, two each. A load detecting means such as a strain gauge 36 is attached to these strain generating portions 32.

  Since the weight measurement load cell 4 and the dummy load cell 2 share the mounting portion 10, the weight measurement load cell 4 and the dummy load cell 2 are affected by the basic vibration force under exactly the same conditions.

The equivalent mass when the weight measuring load cell 4 operates as a vibration system is a mass by a measuring container or a mounting bracket (not shown) attached to the movable part 12, and this is M, the spring system of the weight measuring load cell 4 Assuming that the spring constant is K and the damping ratio is ζ _K , the amplitude transmission rate T _K of the vibration signal of the mounting portion 10 is, as is well known, T _K = [1+ {2 · ζ _K · (ω / ωn)} ² ] ^1/2 / [{1- (ω / ωn)} ² + 2 · ζ _K · (ω / ωn) ² ] ^1/2
The phase delay angle φ _K is expressed as
φ _K = tan ⁻¹ [2 · ζ _K · (ω / ωn) ³ / {1+ (4 · ζ _K ² −1) · (ω / ωn) ² }]
It is represented by

On the other hand, when the equivalent mass as a spring system of the dummy load cell is m, the spring constant is k, and the damping ratio ζ _k , the amplitude transmission rate T _k of the vibration signal of the mounting portion 10 is
T _k = [1+ {2 · ζ _k · (ω / ωn)} ² ] ^1/2 / [{1- (ω / ωn)} ² + 2 · ζ _k · (ω / ωn) ² ] ^1/2
And the phase lag angle φ _k is
φ _k = tan ⁻¹ [2 · ζ _k · (ω / ωn) ³ / {1+ (4 · ζ _k ² −1) · (ω / ωn) ² }]
It is expressed. Here, ωn is a natural frequency, and regarding the natural frequency ωn of the load cell 4 for weight measurement and the dummy load cell 2,
ωn = (K / M) ^1/2 = (k / m) ^1/2
The dummy load cell 2 is formed so that. That is, the ratio of the equivalent mass m of the dummy load cell 2 to the spring constant k is equal to the ratio of the equivalent mass M of the weight measuring load cell 4 to the spring constant K, in other words, the natural frequency of the dummy load cell 2 The spring constant k and the equivalent mass m of the dummy load cell 2 are selected so that the natural frequency of the weight measuring load cell 4 to which the weighing container and the mounting bracket are attached is equal. In this case, the dummy load cell 2 is formed so that K> k and M> m and K / M = k / m is established.

When the dummy load cell 2 is formed in this way, the damping ratios ζ _K and ζ _k that are parameters of the amplitude transmission rate and the phase delay angle are expressed as follows, where the viscosity coefficients are C _K and C _k , respectively.
ζ _K = C _K / 2 · (M · K) ^1/2
ζ _k = C _k / 2 · (m · k) ^1/2
It is expressed.

The coefficient by which the displacement speed of the load cell 4 for weight measurement or the dummy load cell 2 is converted into a viscous damping force is attached to the physical properties of the metal elastic body 6 used for the strain-generating portions 16 and 32 and to the strain-generating portions 16 and 32. The resin material of the strain gauges 20 and 36, the air resistance, and the like, but the physical properties of the resin material of the strain gauges 20 and 36 and the influence of the air driving force are influenced by the viscosity coefficients C _K and C _k of the metal elastic body 6. In comparison, it can be ignored, and the influence of the metal material of the strain generating portions 16 and 32 is large.

The dummy load cell 2 is made of the same metal elastic body 6 as the load measuring load cell 4, and the viscous damping force of the strain generating portions 16, 32 is smaller as the strain generating portions 16, 32 are lowered more thinly. That is, the smaller the spring constants K and k, the thinner the strain-generating portions 16 and 32, so C _K > C _k .

Moreover, since M / K = m / k as described above, the values of ζ _K and ζ _k are close to each other, and the viscous damping force itself of the strain-generating portions 16 and 32 of the load cells 2 and 4 made of metal elastic body itself. Ζ _K and ζ _k are usually 0.1 or less.

On the other hand, ωn / ω is 1/5 because, for example, ωn is 40 Hz and ω is 8 Hz. Therefore, the values of {2 · ζ _K · (ω / ωn)} ² and {2 · ζ _k · (ω / ωn)} ² are sufficiently smaller than 1 in the amplitude transfer rates T _K and T _k . Since the difference between the damping ratios ζ _K and ζ _k is also small, the influence of the difference between the damping ratios ζ _K and ζ _{k on} the amplitude transmission rates T _K and T _k is small. Similarly, the values of 2 · ζ _K · (ω / ωn) ³ and 2 · ζ _k · (ω / ωn) ³ are close to zero, and there is almost no delay difference. In addition, the difference between the damping ratios ζ _K and ζ _k is also small. Therefore, the influence of the difference between the damping ratios ζ _K and ζ _{k on} the phase delay angles φ _K and φ _k is small.

Therefore, the influence of the damping ratios ζ _K and ζ _{k on} the amplitude and phase of the fundamental vibration signal included in the gravity measurement value of the weight measurement load cell 4 and the amplitude and phase of the fundamental vibration output from the dummy load cell 2 is ignored. it can. Therefore, the vibration signal included in the load signal of the weight measuring load cell 4 can be canceled by the load signal output from the dummy load cell 2.

  Unlike the one shown in FIG. 1 of JP-A-6-317457 and FIG. 1 of JP-A-8-114493, the dummy load cell 2 is not formed separately from the load cell for weight measurement, but the load cell 4 for weight measurement. And is integrally formed. Therefore, the production cost is low and the installation cost of the dummy load cell is also unnecessary. Since it is not necessary to secure the mounting location of the dummy load cell, the weighing device is compact, and the mounting location of the dummy load cell and the load cell for weight measurement is the same, so that the basic vibration force received by both does not differ.

  As in Patent Document 1, a dummy load cell is formed in a parallelogram type using two beams 30a and 30b without using a single beam to form a dummy load cell. Since the torsional rigidity with respect to the vibration force in the inclined direction is large, the dummy load cell 2 generates a load signal having substantially the same amplitude and phase as the vibration signal included in the weight measurement load cell 4 even if such vibration force acts. Output, and a high compensation effect can be obtained.

  The dummy load cell 2 is designed and manufactured so that the ratio k / m between the spring constant k and the equivalent mass m is equal to the ratio K / M between the spring constant K and the equivalent mass M of the weight measuring load cell 4. If there is a slight deviation and m needs to be reduced, a hole having an appropriate size may be formed in the movable portion 34. As the hole, a plurality of holes 38 of the same system penetrating in the thickness direction can be formed as indicated by broken lines in FIG. 2, and have a predetermined diameter and depth from both sides of the movable portion 24 in the thickness direction. One or more holes may be provided. When it is necessary to increase the equivalent mass m, the mass adjusting member 40 is added to the movable portion 34 as shown by the broken line in FIG.

  FIG. 3 shows a dummy load cell 102 of the second embodiment. In this dummy load cell 102, circular through holes 122, 124, 126 are formed, beams 130a, 130b are formed, and strain-generating portions 132 are formed on the beams 130a, 130b one by one. Since other configurations are the same as those of the first embodiment, the same parts are denoted by the same reference numerals, and the description thereof is omitted.

  In the load cell 4 for weight measurement, the position of the article to be weighed loaded on the weighing container or the weighing table may change every time the weighing is performed. In accordance with this change in position, an extensional strain stress is generated in the strain-generating portion 16 of the upper beam 14 among the beams 14 and 14, and a compressive strain stress is generated in the strain-generating portion of the lower beam 14. In order to cancel these strain stresses, it is necessary to provide a total of four strain-generating portions 16, two for each of the two beams 14. However, in the dummy load cell 102, since the load does not move, it is not necessary to cancel the strain stress as described above. Therefore, only one strain-generating portion 132 is formed in each of the two beams 130a and 130b. Therefore, since the through holes 122, 124, and 126 to be formed have a simple circular shape, the structure is simple and the manufacture thereof is easy.

  FIGS. 4A to 4C show a dummy load cell 202 according to the third embodiment. In this dummy load cell 202, there is a limit to processing the strain-generating portion 232 into a thin wall in order to make the spring constant k sufficiently smaller than the spring constant K of the load cell 4 for weight measurement. An annular circular groove 240 is formed on the outer periphery of 124, and the thickness dimension t of the strain generating portion 232 of the dummy load cell is made smaller than the thickness T of the strain generating portion 16 of the weight measuring load cell 4. Since other configurations are the same as those of the second embodiment, the same parts are denoted by the same reference numerals, and the description thereof is omitted. In addition, if it is a cyclic | annular groove | channel, it does not need to be limited to circular.

  FIG. 5 shows a dummy load cell 302 of the fourth embodiment. In this embodiment, the through groove 328 is also configured in the same manner as in the second embodiment except that it is formed by round hole machining. Equivalent parts are denoted by the same reference numerals and description thereof is omitted. If comprised in this way, since a linear process will become unnecessary and all will be a round hole process, a process cost can be reduced.

  FIG. 6 shows a dummy load cell 402 of the fifth embodiment. In this dummy load cell 402, the through holes 122 and 126 are formed close to the upper and lower surfaces of the metal elastic body 6, so that the formation of the through holes 122 and 126 not only forms the strain-generating portion 432 of the dummy load cell 402. The strain generating portion 416 of the load cell 4 for weight measurement is also formed. Reference numeral 418 indicates a through groove, which is also formed by round hole machining. Thus, as in the fourth embodiment, it is only necessary to perform round hole processing, and from the contact surface to the measuring instrument main body 18 of the mounting portion 10 of the load cell for weight measurement 4 to the through holes 122, 124, 126. The distance can be shortened, the size can be reduced, and the number of processing steps can be reduced.

DESCRIPTION OF SYMBOLS 2 Dummy load cell 4 Weight measurement load cell 6 Metal elastic body 10 Mounting part 12 Movable part of weight measurement load cell 14 Beam of load cell for weight measurement 16 Strain part of load cell for weight measurement 30a 30b Beam of dummy load cell 32 Dummy load cell Deformation part 34 Movable part of dummy load cell

Claims (6)

The attachment part to the main body of the measuring instrument and the movable part that receives the load of the object to be weighed are located apart from each other, and the attachment part and the movable part are connected by two parallel beams. In the parallelogram weight measuring load cell made of metal elastic body, each of which is formed with a strain-generating portion in parallel beams,
Due to the space penetrating in the thickness direction of the metal elastic body formed in the mounting part, the dummy load cell is integrated with the two parts of the weight measuring load cell in parallel with the part of the mounting part on the measuring instrument main body side. Of two parallel beams,
A strain generating part is formed in two parallel beams for these dummy load cells,
In the mounting portion, at the tip of two parallel beams for the dummy load cell, the movable portion for the dummy load cell has two parallel beams for the dummy load cell, independently of the movable portion of the weight measuring load cell. And both ends of the movable portion for the dummy load cell are respectively spaced from the two parallel beam-side portions of the weight measuring load cell of the mounting portion,
The equivalent mass of the load cell for the dummy load cell and the equivalent mass of the load cell for the weight measurement so as to form a vibration system having substantially the same dynamic characteristics as the vibration system formed by the spring constant of the strain-generating portion of the load cell for weight measurement. Dummy load cell with spring constant set. The attachment part to the main body of the measuring instrument and the movable part that receives the load of the object to be weighed are located apart from each other, and the attachment part and the movable part are connected by two parallel beams. In the parallelogram weight measuring load cell made of metal elastic body, each of which is formed with a strain-generating portion in parallel beams,
Two beams for the dummy load cell extend from the mounting portion in parallel with the two parallel beams of the load cell for weight measurement and integrally with the mounting portion,
A strain generating part is formed in two parallel beams for these dummy load cells,
At the ends of the two parallel beams for the dummy load cell, the movable portion for the dummy load cell is integrated with the two parallel beams for the dummy load cell independently of the movable portion of the load cell for weight measurement. Formed into
The equivalent mass of the load cell for the dummy load cell and the equivalent mass of the load cell for the weight measurement so as to form a vibration system having substantially the same dynamic characteristics as the vibration system formed by the spring constant of the strain-generating portion of the load cell for weight measurement. Set the spring constant,
The weight measuring load cell is formed with a space penetrating in the thickness direction in the metal elastic body, thereby forming the attachment portion, the two parallel beams, and the movable portion,
Three holes penetrating in the thickness direction are formed in a row in the vicinity of the space in the mounting portion at intervals along the direction in which the load is applied to the movable portion, and among the three holes, the load A dummy in which two parallel beams, a strain generating portion and a movable portion for the dummy load cell are formed by penetrating through grooves in the thickness direction of the through grooves that connect both ends of the application direction to the space. Load cell.   The dummy load cell according to claim 2, wherein a strain-generating portion of the weight measuring load cell is also formed by forming one of the three holes at both ends in the load application direction.   The dummy load cell according to claim 2, wherein a hole for mass adjustment or a part for mass adjustment is provided in the movable portion for the dummy load cell.   The dummy load cell according to claim 2, wherein an annular groove for adjusting a spring constant is formed on an outer periphery of at least one of the three holes.   3. The dummy load cell according to claim 2, wherein one or two strain generating portions for the dummy load cell are provided for one dummy load cell beam.

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