Measuring device and measuring method using a three-axis acceleration sensor

Abstract

Provided is a weighing device and a weighing method that enable automatic solution of a problem caused by changes in three-axis directions by using a three-axis acceleration sensor. A weighing device (1) comprises: a weighing tray (11); a weight sensor (12) connected to the weighing tray; a three-axis acceleration sensor (20) that sets x and y on a plane parallel to the horizontal of the weight sensor and z in a direction perpendicular to the horizontal of the weight sensor, and detects acceleration changes in the three axes of x, y, and z; a storage unit (14) that stores reference outputs of the three-axis acceleration sensor along the three axes when the weight sensor is horizontally situated; and an arithmetic operation unit (13). The arithmetic operation unit compares currently-obtained outputs of the three-axis acceleration sensor in along the three axes with the reference outputs, detects existence of inclination when an output along x and / or y has been changed and existence of an installation place change when an output along z has been changed, and notifies of a user of the change.

Description

Technical Field

[0001] The present invention relates to a measuring device and a measuring method using a three-axis acceleration sensor.

Background Art

[0002] A scale, which is a measuring device, measures the component Wv of the load perpendicular to the weighing pan with a weight sensor, and obtains the mass m of the object placed on the weighing pan from Equation (1) using the gravitational acceleration g at the location where the scale is installed.

[0003]

Equation

[0004] As shown in FIG. 10(A), when the direction in which the gravitational acceleration g acts coincides with the direction perpendicular to the weighing pan, the mass measured by the scale, that is, the measured value m, can be said to be the true value. On the other hand, as shown in FIG. 10(B), when the direction in which the gravitational acceleration g acts does not coincide with the direction perpendicular to the weighing pan, a component Wh that cannot be detected by the scale is generated, and the measured value m measured by the scale becomes lighter than the true value.

[0005] From the above situation of the scale, when the following two occur, it can be said that the measured value includes an error. (i) When the scale is tilted and the perpendicular load component Wv to the weighing pan decreases (ii) When the location where the scale is installed changes and the gravitational acceleration g changes Regarding the above (i), a general scale is provided with a level (bubble vial) for detecting the inclination of the scale. For example, in Patent Document 1, a technique for detecting the bubble of the level with an optical sensor and more accurately controlling the level of the scale is disclosed.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Regarding the above (i), although there is a technology such as Patent Document 1, it is necessary to mount a plurality of optical sensors around the bubbles, and the configuration becomes complicated.

[0008] Regarding the above (ii), when asking the user to adjust the sensitivity using a counterweight when changing the installation location of the scale, the response depends on the user and may not be implemented.

[0009] Regarding these problems, the inventors considered that by detecting the acceleration in the three-axis directions of the scale, the problems of the above (i) and (ii) could be detected and solved by the scale itself.

[0010] The present invention has been made based on the above-described conventional problems and the above-described findings of the inventors, and an object thereof is to provide a weighing device and a weighing method that automatically detect acceleration changes in three-axis directions using a three-axis acceleration sensor and automatically solve problems caused by the changes.

Means for Solving the Problems

[0011] In order to solve the above problems, a weighing device according to an aspect of the present invention includes a weighing pan, a weight sensor connected to the weighing pan, x and y are set on a plane parallel to the horizontal of the weight sensor, and z is set in a direction perpendicular to the horizontal of the weight sensor, a three-axis acceleration sensor that detects acceleration changes in the three axes of x, y, and z, a storage unit that stores the reference outputs of the three axes of the three-axis acceleration sensor when the weight sensor is horizontal, and an arithmetic processing unit. The arithmetic processing unit compares the current outputs of the three axes of the three-axis acceleration sensor with the reference outputs, detects that there is an inclination when the output of x and / or y has changed, detects that there is a change in the installation location when the output of z has changed, and notifies the user.

[0012] In the above aspect, when the outputs of the x and / or y of the triaxial acceleration sensor have changed, it is also preferable that the arithmetic processing unit corrects the measured value m detected by the weight sensor to a corrected measured value m' using Equation (14).

[0013] In the above aspect, when only the output of the z of the triaxial acceleration sensor has changed, it is also preferable that the arithmetic processing unit changes the value of the gravitational acceleration used for calculating the measured value m detected by the weight sensor to the value glocal of the local gravitational acceleration obtained using the output of the z-axis of the triaxial acceleration sensor, and sets it as the corrected measured value m'.

[0014] In the above aspect, when the outputs of the z, x, and / or y of the triaxial acceleration sensor have changed, it is also preferable that the arithmetic processing unit changes the value of the gravitational acceleration used in Equation (14) to the local gravitational acceleration glocal obtained using the outputs of the three axes of the triaxial acceleration sensor, and corrects the measured value m detected by the weight sensor to the corrected measured value m'.

[0015] In the above aspect, when the corrected measured value m' of the measured object exceeds the range of the allowable threshold with respect to the reference mass of the measured object, it is also preferable that the arithmetic processing unit warns the user that the error cannot be eliminated by the correction.

[0016] Also, in order to solve the above problems, a weighing method according to an aspect of the present invention uses a weighing device including a weighing pan, a weight sensor connected to the weighing pan, a triaxial acceleration sensor that sets x and y in a plane parallel to the horizontal of the weight sensor and z in a direction perpendicular to the horizontal of the weight sensor to detect acceleration changes in three axial directions of x, y, and z, and includes: (A) a step of acquiring current outputs of the three axes of the triaxial acceleration sensor; (B) a step of comparing the current outputs with reference outputs of the three axes when the weight sensor is horizontal; (C) a step of notifying the user that there is an inclination if the outputs of x and / or y have changed in the step (B); and (D) a step of notifying the user that there is a change in the installation location if the output of z has changed in the step (B).

[0017] In the above aspect, (E) when the outputs of x and / or y have changed in the step (B), a step of correcting a measured value m detected by the weight sensor to a corrected measured value m' using the formula (14); (F) when only the output of z has changed in the step (B), a step of changing a value of gravitational acceleration used for calculating the measured value m detected by the weight sensor to a local gravitational acceleration value glocal obtained using the output of the z-axis of the triaxial acceleration sensor to obtain a corrected measured value m'; and (G) when the outputs of z, x, and / or y have changed in the step (B), a step of changing a value of gravitational acceleration used in the formula (14) to a local gravitational acceleration glocal obtained using the outputs of the three axes of the triaxial acceleration sensor and correcting the measured value m detected by the weight sensor to a corrected measured value m' are also preferable.

[0018] In the above aspect, it is also preferable to include (H) a step of weighing an object to be weighed and warning the user that an error cannot be eliminated in the correction when the corrected measured value m' of the object to be weighed exceeds a range of an allowable threshold with respect to a reference mass of the object to be weighed.

Advantages of the Invention

[0019] According to the present invention, it is possible to provide a weighing device and a weighing method that automatically detect acceleration changes in three axial directions and automatically solve problems caused by the changes.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0021] First, the inventor's considerations until arriving at a preferable embodiment of the present invention will be described with reference to the drawings.

[0022] 1. Considerations by the Inventor 1-1. Problems of a Scale As described above with reference to FIG. 10, generally, a scale includes a weighing pan and a weight sensor connected to the weighing pan, measures a load component Wv perpendicular to the weighing pan, and uses the gravitational acceleration g at the location where the scale is installed to obtain the mass m (measured value) of the object to be weighed from Equation (1).

[0023] [Number]

[0024] For this reason, when the following two situations occur, the measured value m measured by the balance includes an error. (i) When the balance is tilted and the vertical load component Wv with respect to the weighing pan decreases (ii) When the location where the balance is installed changes and the gravitational acceleration g changes

[0025] 1-2. Considerations for Problem Solving Regarding this problem, the inventors considered that by mounting a triaxial acceleration sensor on the balance, the tilt of the balance and the gravitational acceleration can be detected. First, they thought that both the above (i) and (ii) can be automatically detected by the balance. Second, the inventors considered that by using the values of the triaxial acceleration sensor, the balance can identify and automatically correct the change in the measured value caused by the decrease in the vertical load component Wv with respect to the weighing pan and the change in the gravitational acceleration g.

[0026] FIG. 1 is a diagram showing the relationship between the tilt angle and each component of the gravitational acceleration when a triaxial acceleration sensor is mounted on a certain virtual plane vp. This triaxial acceleration sensor (hereinafter referred to as the acceleration sensor) detects the acceleration in the three orthogonal directions of the virtual plane vp. The x and y of the acceleration sensor are on the virtual plane vp, and z is in the direction perpendicular to the virtual plane vp. Each component of the gravitational acceleration g with respect to this triaxial acceleration sensor is denoted as "gx, gy, gz". The gx and gy components are on the virtual plane vp, and there is a gz component in the direction perpendicular to the virtual plane vp. The tilt angle θ is the angle formed by the direction of the gravitational acceleration g and the direction of the gz component.

[0027] Let the components output by the acceleration sensor at the tilt angle θ be "Xout(θ), Yout(θ), Zout(θ)", respectively. When the gravitational acceleration g detected by the acceleration sensor is g = {gx(θ), gy(θ), gz(θ)}, gx(θ), gy(θ), and gz(θ) can be expressed by equations (2), (3), and (4) respectively using the outputs "Xout(0), Yout(0), Zout(0)" at the tilt angle θ = 0. Here, Ax, Ay, and Az are proportionality coefficients, and g = |g|.

[0028]

Number

[0029]

Number

[0030]

Number

[0031]

Number

[0032]

Number

[0033] 1-3. Correction for the Tilt of the Scale Consider the correction of the weighing value with respect to the inclination of the scale, that is, the decrease in the vertical load component Wv with respect to the weighing pan. The inclination of the scale can be detected by monitoring the x and y outputs of the acceleration sensor. Let the mass of the weighed object when the inclination angle θ of the scale is 0 be m(0), and the mass of the weighed object when the inclination angle is θ be m(θ). Let the load on the weighing pan of the scale be W, and the vertical load component with respect to the weighing pan be Wv. Here, when the virtual plane vp is set parallel to the horizontal of the weight sensor, when the inclination angle θ = 0, W = m(0) and the gravitational acceleration g = Wv, so the relationship of Equation (7) holds.

[0034]

Number

[0035] However, when the inclination angle θ ≠ 0, from Equation (6), since the gravitational acceleration gz(θ) perpendicular to the weighing pan is given by Equation (8), the vertical load component Wv with respect to the weighing pan is given by Equation (9), and

[0036]

Number

[0037]

Number

[0038]

Number

[0039]

Number

[0040]

Number

[0041]

Number

[0042] The scale obtains the mass m(θ) as the measured value. From Equation (12) and Equation (13), it can be seen that when the scale has an inclination angle θ, since a correction term including θ is multiplied by the measured value m(0) when the inclination angle θ = 0, the mass will be underestimated. Therefore, when there is an inclination angle θ, in order to obtain the correct mass (measured value), it is necessary to divide the mass m(θ) at the time of the inclination angle θ by the correction term including θ, cosθ or √1 - sin²θ.

[0043] Regarding the correction term, theoretically, the values are equal regardless of whether it is calculated using Equation (12) or Equation (13). However, in reality, since it is assumed to detect a very small inclination (0.1° or less) where θ ≃ 0, a very small angle change cannot be known by using the cosine component of Equation (12). Therefore, it is preferable to use the sine component of Equation (13) as the correction term.

[0044] Therefore, when the acceleration sensor detects the inclination angle θ, the scale corrects the measured value m (mass m(θ)) measured by the scale based on Equation (13) and Equation (5), and calculates the corrected measured value m´ using the following Equation (14).

[0045]

Number

[0046] Figure 2 is a diagram showing the result of verifying the correction using a three-axis acceleration sensor. In the verification, a scale with a weighing capacity of 10 kg and a minimum display of 0.01 g was used, and the object to be weighed placed on the weighing pan was 10000 g. Here, the inclination angle from the installation surface (which is horizontal) of the scale was changed from 0° to 0.5°, and this inclination angle was taken as θ. The measured value m of the object to be weighed was corrected using Equation (14) to obtain the corrected measured value m´. As shown in Figure 2, the corrected measured value m´ of 10000 g was obtained at any inclination angle.

[0047] 1-4. Correction for Changes in the Installation Location of the Scale Consider the correction of the measured value for changes in the acceleration due to gravity g caused by changes in the installation location of the scale due to shipping from the factory or relocation of facilities. Changes in the acceleration due to gravity g can be detected by monitoring the acceleration due to gravity gz(θ) in the direction perpendicular to the horizontal of the load cell. As described above, in the scale, the measured value m is obtained by Equation (1) using the component Wv of the load perpendicular to the weighing pan. Therefore, by changing the value of "g" used in Equation (1) from the value before the relocation of the scale to the value after the relocation of the scale (hereinafter referred to as the "local acceleration due to gravity 'glocal'"), the error caused by the change in the installation location of the scale can be eliminated.

[0048] Here, the local acceleration due to gravity glocal is obtained using the output value of the acceleration sensor. From Equation (6), glocal is Equation (15).

[0049]

Equation

[0050] When the scale detects a change in the acceleration due to gravity g by the acceleration sensor, the scale changes the value of the acceleration due to gravity g used in calculating the measured value m detected by the load cell in Equation (1) to the value of the local acceleration due to gravity glocal obtained using the output of the acceleration sensor obtained by Equation (15), and obtains the measured value. Here, in this consideration, when the installation location of the scale changes, that is, when only the z-component of the acceleration sensor changes, in Equation (15), the tilt angle θ is zero, and glocal = gz(θ = 0). In other words, when the scale detects a change in the acceleration due to gravity g by the acceleration sensor, the scale uses, as the corrected measured value m´, the value obtained by dividing the component Wv of the load perpendicular to the weighing pan measured by the load cell by the local acceleration due to gravity glocal (however, θ = 0) (Equation (16)).

[0051]

Equation

[0052] In the prior art, the local gravitational acceleration glocal was obtained by (1) storing the numerical value of the gravitational acceleration at the representative location in the memory unit of the scale (for example, 9.79952 [m / s2] in Ibaraki, 9.80478 [m / s2] in Sapporo, 9.79703 [m / s2] in Osaka, etc.) and selecting the location closest to the installation location (local) of the scale, or (2) adjusting using weights at the installation location (local) of the scale. In contrast, if the above consideration using the acceleration sensor is used, since the local gravitational acceleration glocal of the scale can be reflected by using the output value of the acceleration sensor, the measurement accuracy is improved compared to the prior art method, and there is an advantage that when the installation location of the scale is changed, the adjustment using weights that was previously performed locally is no longer required.

[0053] 1-5. Correction when both the inclination of the scale and the change in the installation location occur Consider the correction of the measured value when both a decrease in the vertical load component Wv with respect to the weighing pan and a change in the gravitational acceleration g occur. When both occur, based on the considerations in 1-3 and 1-4 above, if the value of "g" used in the equation (14) regarding the inclination is changed to the local gravitational acceleration glocal, both errors can be eliminated. glocal is equation (15), and further equation transformation to equation (17) holds.

[0054]

Number

[0055] The sine term in equation (17) is obtained from equation (5) including gx(θ) and gy(θ) detected by the acceleration sensor. Therefore, the local gravitational acceleration glocal is obtained by substituting the output values of x, y, and z of the acceleration sensor into equation (17). In other words, when both the inclination of the scale and the change in the gravitational acceleration occur, the scale corrects the measured value m (mass m(θ)) measured by the scale using the local gravitational acceleration glocal (θ≠0) with the following equation (18) to calculate the corrected measured value m´.

[0056]

Number

[0057] 1 - 6. Measurement method using a three - axis acceleration sensor From the above considerations, the inventors first mounted a three - axis acceleration sensor on the scale, and by comparing the reference outputs “Xout(0), Yout(0), Zout(0)” when the scale is horizontal (tilt angle θ = 0) with the current outputs “Xout(1), Yout(1), Zout(1)”, they thought that (i) the tilt of the scale and (ii) the changes due to the installation location could be distinguished and detected by the scale itself. Furthermore, the inventors were convinced that, second, the measured values when the scale is tilted can be corrected based on the considerations in 1 - 3 above, the measured values when the installation location of the scale changes can be corrected based on the considerations in 1 - 4 above, and the measured values when both occur can be corrected based on the considerations in 1 - 5 above.

[0058] Therefore, by mounting a three - axis acceleration sensor on the scale and detecting the following three acceleration change patterns, the scale can automatically detect the tilt of the scale and the change in the installation location, and automatically correct the error in the measured value due to the change. Pattern (1): Only z changes Pattern (2): x and / or y change (i.e., x and y change, x changes, or y changes) Pattern (3): z and x and / or y change (i.e., x, y, z all change, x and z change, or y and z change)

[0059] When pattern (1) occurs: The scale detects that the installation location has changed and notifies the user. Then, the measured value is corrected using equation (16). The gravitational acceleration g uses the local gravitational acceleration glocal. When pattern (2) occurs: The scale detects that an inclination has occurred and notifies the user. Then, the measured value is corrected using equation (14). The gravitational acceleration g uses the value used previously without change. When pattern (3) occurs: The scale detects that both the inclination and the gravitational acceleration have changed, and notifies the user. Then, the measured value is corrected using Equation (18). The gravitational acceleration g uses the local gravitational acceleration glocal.

[0060] Based on the above considerations, a preferred embodiment of the present invention will be described with reference to the drawings.

[0061] 2. First Embodiment 2-1. Configuration of the weighing device (scale) FIG. 3 is a block diagram of the configuration of the weighing device according to the first embodiment of the present invention, and FIG. 4 is a schematic perspective view of the weighing device. The weighing device is an electronic scale (hereinafter referred to as scale 1). Scale 1 includes a main body case 10, a weighing pan 11, a weight sensor 12, an arithmetic processing unit 13, a storage unit 14, an operation unit 15, a display unit 16, and a three-axis acceleration sensor 20.

[0062] As shown in FIG. 4, inside the main body case 10, a Roberval mechanism 12' for connecting the weighing pan 11 and the weight sensor 12 is accommodated. The Roberval mechanism 12' is a structure for transmitting the load received by the weighing pan 11 to the weight sensor 12. It is formed of a rectangular metal block and includes a floating part that receives the load from the weighing pan 11, a fixed part that is fixed to the main body case 10, upper and lower auxiliary rods that connect the floating part and the fixed part, and a load transmission part that transmits the load acting on the floating part to the weight sensor 12. It is a known one. The weighing pan 11 is supported by the Roberval mechanism 12' and is disposed on the main body case 10. The weighing pan 11 has a horizontal plane 11', and the object to be weighed is placed on the horizontal plane 11'. For the weight sensor 12, an electromagnetic balance type, a strain gauge type, an electrostatic capacitance type, etc. are used. The load detected by the weight sensor 12 is A / D converted and input to the arithmetic processing unit 13, and is converted into a measured value.

[0063] As described above, generally, the scale measures the vertical load component Wv with respect to the weighing pan, and uses the gravitational acceleration g at the location where the scale is installed to obtain the measured value m of the weighed object from Equation (1). To utilize this principle, as a prerequisite, when the scale 1 is assembled, the weight sensor 12 is mounted on a platform where the level is ensured, for example, while using a spirit level or the like, so that the weight sensor 12 maintains a horizontal position with respect to the main body case 10 (for example, it is mounted so that the plane provided in the Roberval mechanism 12' maintains a horizontal position). The weighing pan 11 is supported downward from a direction perpendicular to the horizontal of the weight sensor 12 by a pan boss (not shown) protruding from the Roberval mechanism 12', and is mounted so that the horizontal plane 11' of the weighing pan 11 coincides with the horizontal of the weight sensor.

[0064] The triaxial acceleration sensor 20 (hereinafter referred to as the acceleration sensor 20) is an IC module including a sensor in which a spring and a weight are integrated and an element that captures the displacement when acceleration is applied to the sensor. The acceleration sensor 20 is arranged on a virtual plane vp parallel to the horizontal of the weight sensor 12. The x and y of the acceleration sensor 20 are arranged on the virtual plane vp, and the z is arranged in a direction perpendicular to the virtual plane vp. Thereby, the acceleration sensor 20 has x and y parallel to the horizontal of the weight sensor 12, and z is set in a direction perpendicular to the horizontal of the weight sensor 12, and detects the acceleration in the three orthogonal directions (x, y, z) of the virtual plane vp. That is, the acceleration sensor 20 is mounted so that the horizontal of the acceleration sensor 20 coincides with the horizontal of the weight sensor 12. In this embodiment, since the purpose is to detect and correct the change due to the inclination of the load received by the weight sensor 12, by mounting the acceleration sensor 20 so that the horizontal of the acceleration sensor 20 coincides with the horizontal of the weight sensor 12, the origins of the inclination angles of both coincide, and the error can be reduced. The virtual plane vp on which the acceleration sensor 20 is arranged may be set at any position within the main body case 10 as long as it does not interfere with the weight sensor 12. A preferred setting of the virtual plane vp on which the acceleration sensor 20 is mounted, that is, the mounting position of the acceleration sensor 20, will be described later. Note that the settings of the x-axis and y-axis in FIG. 4 may be reversed.

[0065] After the acceleration sensor 20 is attached to the balance 1 and before the balance 1 is shipped from the factory, on a table where the horizontal level is ensured, that is, in a state where the weight sensor 12 is horizontal, the reference outputs “Xout(0), Yout(0), Zout(0)” of each component are measured and stored in the storage unit 14 described later.

[0066] The operation unit 15 and the display unit 16 are provided on the front side surface of the main body case 10 of the balance 1. From the operation unit 15, the weighing operation described later can be performed. On the display unit 16, a screen associated with the weighing described later is displayed.

[0067] The arithmetic processing unit 13 is a microcontroller in which, for example, a CPU, ROM, RAM, etc. are implemented in an integrated circuit. The arithmetic processing unit 13 has an acceleration change detection unit 131 and a change notification unit 132 for detecting an acceleration change using the acceleration sensor 20. Also, the arithmetic processing unit 13 has an inclination correction unit 133 and a gravity correction unit 134 for performing correction associated with the acceleration change. The functions of the functional units 131, 132, 133, and 134 are realized, for example, by the CPU reading and executing the programs stored in the storage unit 14. The details of the functions of each functional unit will be described in “2-2. Weighing method” described later.

[0068] The storage unit 14 is a semiconductor memory element such as a RAM or a flash memory, or a storage medium such as a memory card. Various programs for the arithmetic operation of the arithmetic processing unit 13 are stored in the storage unit 14. Further, the storage unit 14 stores the reference outputs “Xout(0), Yout(0), Zout(0)” of the acceleration sensor 20 for detecting changes using the acceleration sensor 20.

[0069] The above is the configuration of the balance 1 using the acceleration sensor 20 according to the first embodiment. Next, the weighing method using such a balance 1 will be described.

[0070] 2-2. Weighing method FIG. 5 is a flowchart of a weighing method using the weighing device according to the first embodiment. This flow is automatically started before the scale 1 shifts to the weighing mode, such as when the power of the scale 1 is turned on or when the scale 1 has not been used for a certain period of time.

[0071] When the flow starts, first, in step S101, the acceleration change detection unit 131 functions to acquire the current outputs “Xout(1), Yout(1), Zout(1)” of the acceleration sensor 20.

[0072] Next, it proceeds to step S102, where the acceleration change detection unit 131 reads out the reference outputs “Xout(0), Yout(0), Zout(0)” and compares them with the current outputs “Xout(1), Yout(1), Zout(1)”.

[0073] Next, it proceeds to step S103, where the acceleration change detection unit 131 determines which change of the following patterns it corresponds to. Pattern (1): Only z changes Pattern (2): x and / or y change Pattern (3): z and x and / or y change

[0074] If there is no change in any of patterns (1) to (3), it proceeds to step S104, where the change notification unit 132 functions to notify the user that there is no acceleration change. The change notification unit 132 displays, for example, on the display unit 16, a message indicating that there is no acceleration change, or more specifically, that there is no abnormality in the inclination of the scale or the gravitational acceleration. When the notification by the change notification unit 132 is completed, the scale 1 shifts to the weighing mode.

[0075] On the one hand, when pattern (1) is detected in step S103, the flow proceeds to steps S105 and S106. In step S106, the change notification unit 132 notifies the user that there has been a change in pattern (1). The change notification unit 132 displays, for example, on the display unit 16, a message indicating that there is a change in the acceleration in the z direction, or more specifically, that the measured value is affected by the change in the installation location.

[0076] Next, the flow proceeds to step S107, where the gravity correction unit 134 functions. The gravity correction unit 134 applies the current outputs “Xout(1), Yout(1), Zout(1)” of the acceleration sensor 20 to equation (15) to obtain the local gravitational acceleration glocal, and sets it to obtain the measured value using equation (16). When the correction setting by the gravity correction unit 134 is completed, the scale 1 shifts to the weighing mode. At this time, it is also preferable for the gravity correction unit 134 to notify the user that the correction corresponding to the change in the installation location (change in the acceleration in the z direction) has been set. In subsequent weighing, the scale 1 uses the corrected measured value m´ obtained by equation (16) as the true value, displays the corrected measured value m´ on the display unit 16, and records it in the storage unit 14 or a specified storage device.

[0077] When pattern (2) is detected in step S103, the flow proceeds to steps S108 and S109. In step S109, the change notification unit 132 notifies the user that there has been a change in pattern (2). The change notification unit 132 displays, for example, on the display unit 16, a message indicating that there is a change in the acceleration in the x and y directions, or in other words, that the measured value is affected by the inclination of the scale.

[0078] Next, the flow proceeds to step S110 where the inclination correction unit 133 functions. The inclination correction unit 133 is set to correct the measured value according to equation (14). When the setting of the correction by the inclination correction unit 133 is completed, the scale 1 shifts to the weighing mode. At this time, it is also preferable for the inclination correction unit 133 to notify the user that the correction corresponding to the inclination of the scale (change in acceleration in the x and y directions) has been set. In subsequent weighings, the scale 1 uses the corrected measured value m' corrected by equation (14) as the true value, displays the corrected measured value m' on the display unit 16, and records it in the storage unit 14 or a specified external storage device.

[0079] If pattern (3) is detected in step S103, the flow proceeds to steps S111 and S112. In step S112, the change notification unit 132 notifies the user that there has been a change in pattern (3). The change notification unit 132 displays, for example, on the display unit 16, a message indicating that there is a change in the acceleration in the x, y, and z directions, or in other words, that the measured value is affected by the change in the inclination of the scale and the installation location.

[0080] Next, the flow proceeds to step S113 where both the gravity correction unit 134 and the inclination correction unit 133 function. First, the gravity correction unit 134 functions to obtain the local gravitational acceleration glocal from the current outputs “Xout(1), Yout(1), Zout(1)” of the acceleration sensor 20 according to equation (17). Next, the inclination correction unit 133 functions to set the measured value to be obtained according to equation (18) by applying the local gravitational acceleration glocal to equation (14). When this setting is completed, the scale 1 shifts to the weighing mode. At this time, it is also preferable for the inclination correction unit 133 and the gravity correction unit 134 to notify the user that the correction corresponding to both the change in the inclination of the scale and the installation location (change in acceleration in the x, y, and z directions) has been set. In subsequent weighings, the scale 1 obtains the corrected measured value m' using equation (18), displays it on the display unit 16, and records it in the storage unit 14 or a specified external storage device.

[0081] 2-3. Effects According to the balance 1 of the present embodiment, by mounting the triaxial acceleration sensor 20 on the balance 1, (i) When the balance is tilted and the vertical load component Wv with respect to the weighing pan decreases (ii) When the location where the balance is installed changes and the gravitational acceleration g changes both problems can be detected by the balance 1.

[0082] In particular, by simultaneously monitoring the changes in the x, y, and z outputs with the triaxial acceleration sensor 20, it is possible to identify which of the problems (i) and (ii) above is the cause, and the measured value can be appropriately corrected corresponding to each problem.

[0083] Also, for the above (i), since it is only necessary to attach the triaxial acceleration sensor 20, the configuration does not become complicated. For the above (ii), the response due to the change in the installation location was left to the user, whereas now the balance itself can detect and automatically correct it.

[0084] 3. Second Embodiment In the second embodiment, the weighing method in the first embodiment is combined with daily inspection. Regarding the elements described in the first embodiment, the description will be omitted by using the same reference numerals.

[0085] 3-1. Configuration of the weighing device (balance) FIG. 6 is a configuration block diagram of the weighing device according to the second embodiment of the present invention. The balance 1 includes a main body case 10, a weighing pan 11, a weight sensor 12, an arithmetic processing unit 13, a storage unit 14, an operation unit 15, a display unit 16, a triaxial acceleration sensor 20, and further includes a built-in counterweight 17, a counterweight addition / removal unit 18, and a spirit level 19.

[0086] The built-in weight 17 and the weight addition / removal unit 18 are well-known in scales with an automatic calibration function. Before the scale 1 is shipped from the factory, the built-in weight 17 is placed on a table where the scale 1 is leveled, pre-measured, and the reference mass "mw0" is stored. The weight addition / removal unit 18 has its motor and cam controlled by the arithmetic processing unit 13, and the built-in weight 17 is placed on and removed from the weight receiving part 17' multiple times. The weight receiving part 17' is linked to the aforementioned beam, and the load of the built-in weight 17 is transmitted to the weight sensor 12. Note that a pump type may be adopted for the weight addition / removal unit 18.

[0087] The level 19 is a well-known device that allows the user to visually check whether the bubble is located at the center of the reference line. The level 19 is provided on the front side of the main body case 10.

[0088] The arithmetic processing unit 13 has a daily inspection unit 135 that executes a daily inspection application. The storage unit 14 stores a program for executing the daily inspection application, the reference mass "mw0" of the built-in weight 17, and an allowable threshold value for the reference mass "mw0".

[0089] 3-2. Weighing method FIG. 7 is a flowchart of a weighing method using the weighing device according to the second embodiment. Here, in the daily inspection of the scale, (1) confirmation of the horizontal state, (2) confirmation of dirt and foreign objects, (3) confirmation of zero return, (4) confirmation of reproducibility, (5) confirmation of offset error, etc. are performed. The scale 1 is equipped with a "daily inspection" button on the operation unit 15, and a screen for guiding the check of items (1) to (5) related to the daily inspection is displayed on the display unit 16 by the daily inspection application. Since the daily inspection application is well-known, details are omitted. The weighing method of this embodiment combines the weighing method of the first embodiment with a part of this daily inspection.

[0090] When the flow starts, the daily inspection unit 135 functions, and for item (1): confirmation of the horizontal state, at step S200, a screen is displayed to guide the user to check whether the bubble of the level 19 is within the reference line. The user adjusts an adjuster (not shown) connected to the main body case 10 to adjust the position of the bubble. However, since this operation is manual, there may be a very small inclination (0.1° or less) remaining.

[0091] After the manual horizontal adjustment in step S200 is completed, the flow proceeds to step S201. In step S201, similar to step S101, the acceleration change detection unit 131 acquires the current outputs “Xout(1), Yout(1), Zout(1)” of the acceleration sensor 20.

[0092] The subsequent steps S202 to S213 are the same as S102 to S113 in the first embodiment. In each of steps S207, S210, and S213, when the correction setting is completed, the flow proceeds to step S214.

[0093] In step S214, the daily inspection unit 135 weighs the built-in weight 17 as item (4): confirmation of reproducibility. At this time, the built-in weight 17 is measured with the corrected weighing value m´ according to the respective settings in steps S207, S210, and S213.

[0094] Next, the flow proceeds to step S215, and the daily inspection unit 135 compares the weighed value m´ of the built-in weight 17 with the reference mass mw0 to determine whether there is a problem. If the error between the weighed value m´ and the reference mass mw0 is within the allowable threshold range, the daily inspection unit 135 determines that there is no problem (YES), and considers that balance 1 has cleared items (1) and (4). After checking the remaining items, it proceeds to the weighing mode.

[0095] On the other hand, if the error between the measured value m´ and the reference mass mw0 exceeds the allowable threshold range in step S215, the daily inspection unit 135 determines that there is a problem (NO) and proceeds to step S216. In step S216, the daily inspection unit 135 determines that the error cannot be eliminated by software correction for the resolution of the scale 1, and issues a warning to the user. The daily inspection unit 135 displays a warning message on the display unit 16, for example, instructing the user to perform sensitivity adjustment again using the external partial weight.

[0096] 3-3. Effect As described above, according to the present embodiment, in addition to the effects in the first embodiment, by combining the weighing method using the triaxial acceleration sensor 20 for the daily inspection of the scale, it is possible to effectively correct for minute inclinations that cannot be eliminated by manual operation.

[0097] In this embodiment, for (4): confirmation of reproducibility, the built-in weight 17 is used as the weighed object. However, even for a scale without a built-in weight 17, the present embodiment can be implemented simply by performing item (4) using an external partial weight with a known reference mass.

[0098] 4. Mounting position of the acceleration sensor It is important to mount the acceleration sensor 20 such that the horizontal of the acceleration sensor 20 coincides with the horizontal of the weight sensor 12. The virtual plane vp on which the acceleration sensor 20 is disposed may be set at any position within the main body case 10 as long as it does not interfere with the weight sensor 12 (robust mechanism 12´). For example, it is preferably mounted in the following configuration.

[0099] FIG. 8 is a diagram showing a preferred mounting form of the acceleration sensor 20 in the first and second embodiments, and is an example in which the acceleration sensor 20 is mounted on the "lower case". FIG. 8 is a longitudinal end view of the scale 1.

[0100] The main body case 10 has a split structure of an upper case 10u and a lower case 10d, and the upper case 10u and the lower case 10d are fitted with each other via a sealing material such as silicone rubber. The acceleration sensor 20 is placed on the sensor mounting plate 21 and is preferably fixed to the inner surface of the case of the lower case 10d, for example, by screwing, via three or more mounting bosses 22 to suppress the vibration of the sensor. The sensor mounting plate 21 has a flat surface, and the sensor mounting plate 21 serves as a virtual plane vp. Note that the sensor mounting plate 21 may directly use the IC substrate of the acceleration sensor 20.

[0101] When the balance 1 is assembled, the acceleration sensor 20 is fixed to the lower case 10d after being confirmed to keep the sensor mounting plate 21 horizontal, for example, while using a spirit level on a table where the horizontal is ensured.

[0102] Here, as described above, the weight sensor 12 (robust mechanism 12´) is confirmed to keep horizontal, for example, while using a spirit level on a table where the horizontal is ensured, via the support member 10c, and is fixed to the main body case 10. Therefore, if the acceleration sensor 20 is also mounted horizontally with respect to the main body case 10, it can be mounted so that the horizontal of the acceleration sensor 20 coincides with the horizontal of the weight sensor 12.

[0103] FIG. 9 is a diagram showing a mounting form of the acceleration sensor 20 suitable for the first and second embodiments, and is an example in which the acceleration sensor 20 is mounted on the "upper case". Similarly, the acceleration sensor 20 is placed on the sensor mounting plate 21 and is fixed to the inner surface of the case of the upper case 10u by screwing via three or more mounting bosses 22. Similarly, when the balance 1 is assembled, the acceleration sensor 20 is fixed to the main body case 10 after being confirmed to keep the sensor mounting plate 21 horizontal, for example, while using a spirit level on a table where the horizontal is ensured. Therefore, the acceleration sensor 20 is mounted so that the horizontal of the acceleration sensor 20 coincides with the horizontal of the weight sensor 12.

[0104] In FIGS. 8 and 9, the weight sensor 12 is fixed to the upper case 10u, but is not limited thereto, and may be configured to be fixed to the lower case 10d. The fixed position of the acceleration sensor 20 is preferably made to coincide with the case on the side where the weight sensor 12 is fixed.

[0105] As described above, the preferred embodiments of the present invention have been described. However, the above embodiments are examples of the present invention, and it is possible to combine them based on the knowledge of those skilled in the art, and such forms are also included in the scope of the present invention.

Explanation of Reference Numerals

[0106] 1 Balance 11 Measuring Dish 11´ Horizontal Plane of Measuring Dish 12 Weight Sensor 13 Arithmetic Processing Unit 14 Storage Unit 17 Built-in Counterweight 20 Triaxial Acceleration Sensor

Claims

1. A weighing dish, A weight sensor connected to the weighing dish, Set x and y on a plane parallel to the horizontal of the weight sensor, and z in a direction perpendicular to the horizontal of the weight sensor, and a triaxial acceleration sensor that detects changes in acceleration in the three axes of x, y, and z, A storage unit that stores the reference outputs of the three axes of the triaxial acceleration sensor when the weight sensor is horizontal, An arithmetic processing unit, and The arithmetic processing unit compares the current outputs of the three axes of the triaxial acceleration sensor with the reference outputs, and if the outputs of x and / or y have changed, it detects that there is an inclination, and if the output of z has changed, it detects that there is a change in the installation location and notifies the user A weighing device characterized by the above.

2. When the outputs of x and / or y of the triaxial acceleration sensor have changed, the arithmetic processing unit corrects the measured value m detected by the weight sensor to a corrected measured value m' using Equation (14). The weighing device according to Claim 1, characterized by the above. 【Number 14】 However, g: The value of gravitational acceleration θ: The angle formed by the direction of gravitational acceleration and the z-axis detected by the triaxial acceleration sensor gx(θ): The value of the output of x detected by the triaxial acceleration sensor gy(θ): The value of the output of y detected by the triaxial acceleration sensor

3. When only the output of z of the triaxial acceleration sensor has changed, the arithmetic processing unit changes the value of gravitational acceleration used in calculating the measured value m detected by the weight sensor to the value of local gravitational acceleration glocal obtained using the output of the z-axis of the triaxial acceleration sensor, and sets it as the corrected measured value m'. The weighing device according to Claim 1, characterized by the above.

4. When the outputs of z, x, and / or y of the triaxial acceleration sensor have changed, the arithmetic processing unit changes the value of gravitational acceleration used in Equation (14) to the local gravitational acceleration glocal obtained using the outputs of the three axes of the triaxial acceleration sensor, and corrects the measured value m detected by the weight sensor to the corrected measured value m'. The weighing device according to Claim 2, characterized by the above.

5. When the corrected measured value m' of the weighed object exceeds the allowable threshold range with respect to the reference mass of the weighed object, the arithmetic processing unit warns the user that the error cannot be eliminated by correction. The weighing device according to any one of Claims 2 to 4, characterized by the above.

6. Using a weighing device comprising a weighing dish, a weight sensor connected to the weighing dish, and a triaxial acceleration sensor that sets x and y in a plane parallel to the horizontal of the weight sensor and z in a direction perpendicular to the horizontal of the weight sensor to detect changes in acceleration in the three axial directions of x, y, and z, (A) obtaining current outputs of the three axes of the triaxial acceleration sensor; (B) comparing the current outputs with reference outputs of the three axes when the weight sensor is horizontal; (C) when the output of x and / or y has changed in step (B), notifying the user that there is an inclination; (D) when the output of z has changed in step (B), notifying the user that there is a change in the installation location; A weighing method characterized by comprising the above.

7. (E) when the output of x and / or y has changed in step (B), using Equation (14) to correct the measured value m detected by the weight sensor to a corrected measured value m'; (F) when only the output of z has changed in step (B), changing the value of the gravitational acceleration used for calculating the measured value m detected by the weight sensor to the value of the local gravitational acceleration glocal obtained using the output of the z-axis of the triaxial acceleration sensor, and setting it as the corrected measured value m'; (G) when the outputs of z, x, and / or y have changed in step (B), changing the value of the gravitational acceleration used in Equation (14) to the local gravitational acceleration glocal obtained using the outputs of the three axes of the triaxial acceleration sensor, and correcting the measured value m detected by the weight sensor to a corrected measured value m'; The weighing method according to claim 6, characterized by comprising the above. 【Number 14】 However, g: Value of gravitational acceleration θ: Angle formed by the direction of gravitational acceleration and the z-axis detected by the triaxial acceleration sensor gx(θ): Value of the output of x detected by the triaxial acceleration sensor gy(θ): Value of the output of y detected by the triaxial acceleration sensor

8. (H) weighing the object to be weighed, and when the corrected measured value m' of the object to be weighed exceeds the allowable threshold range with respect to the reference mass of the object to be weighed, warning the user that the error cannot be eliminated by correction; The weighing method according to claim 7, characterized by comprising the above.

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