JP2014102223A - Weighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a weighting device for enabling a user to accurately have a clear view of a period when a load sensor reaches a use limit.SOLUTION: The weighting device includes: a load sensor 2 for supporting holding means 1 which holds an object to be weighted; an A/D converter 4 for A/D converting the output signal of the load sensor 2; a control device 5; and a display part 7. The control device 5 performs processing of converting the output value of the A/D converter 4 into a measured value corresponding to the weight of the object to be weighted, and when the measured value obtained by converting the output value of the A/D converter 4 when the object to be weighted is not held by the holding means 1 is not zero, performs zero adjustment processing to set the measured value to zero, and when the zero adjustment processing is performed, calculates at least one of a lower limit margin value as a difference between the lower limit values of two ranges, that is, the output range of a digital value at a current point of time of the A/D converter 4 corresponding to a measurable weight range and the range of a specified digital value which can be output and an upper limit margin value as a difference between the upper limit values of those two ranges, and allows a display part 7 to display information related to the calculated margin value.

Description

  The present invention relates to a weighing device using a load sensor such as a load cell.

  Examples of a weighing device that measures the weight of an object to be weighed using a load sensor such as a load cell include a platform scale, a charge scale, a weight sorter, and a combination scale.

  In such a conventional weighing device, for example, an abnormality at the zero point of the weighing device is detected based on a weight value (zero point weight value) measured in a state where an object to be weighed is not placed on the weighing table, and an abnormality alarm is displayed. It is comprised so that it can display on a container and alert | report to a user (for example, refer patent document 1). The abnormality of the zero point is detected by, for example, detecting that the zero point weight value is outside the allowable range.

JP-A-2005-147920

  In such a weighing device, zero point adjustment is possible even after the abnormality of the zero point is notified, and if there is no fluctuation in the span of the load sensor (when the span is normal), the zero point adjustment is performed for the time being. In some cases, the weight of the object to be weighed can be measured correctly.

  In the above-mentioned conventional weighing device, it is possible to recognize the necessity of replacing the load sensor that causes the zero point abnormality by notifying the user of the zero point abnormality. I do not know if a load sensor can be used. Even after the zero point abnormality is notified, the user does not replace the load sensor for the time being (for example, until preparations for replacement of the load sensor, etc.) and does not replace the load sensor while adjusting the zero point. You may want to use it.

  However, as mentioned above, the user does not know how long the load sensor can be used, and if it is used as it is, there is a risk of erroneous weighing, so the zero point abnormality was reported. After that, I tried not to use the weighing device. That is, even when the zero point abnormality is notified, it has not been possible to determine when the load sensor reaches the use limit.

  In addition, even when the zero point abnormality is not reported, it is useful for performing maintenance and the like to determine when the load sensor reaches the use limit, but this has not been possible with conventional weighing devices. .

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a weighing device that enables a user to determine when a load sensor reaches a use limit.

  In order to achieve the above object, a weighing device according to an aspect of the present invention supports holding means for holding an object to be measured and outputs an analog load signal voltage corresponding to a load to be loaded. A load sensor, an analog voltage range that can be input, and a digital value range that can be output corresponding to this range are defined, and the analog load signal voltage output from the load sensor is A / D converted to obtain a digital value. A / D converter to output, weighing value conversion means for converting a digital value output from the A / D converter into a weighing value corresponding to the weight of the weighing object, and the weighing object is held by the holding means If the measured value obtained by converting the zero-point A / D converted value, which is a digital value output from the A / D converter when the measured value is not converted, by the measured value conversion means is not zero, the measured value is zero. To be A zero point adjusting means for performing point adjustment processing, and the A / D converter corresponding to a predetermined measurable weight range based on the zero point A / D conversion value when the zero point adjustment processing is performed. A lower limit margin value which is a difference between lower limit values of two ranges of an output range of digital values at the present time and a range of digital values which can be output; and an upper limit margin value which is a difference between upper limit values of the two ranges; Margin value calculating means for calculating at least one of the above and margin value notifying means for notifying information on the lower limit margin value and / or the upper limit margin value calculated by the margin value calculation means.

  According to this configuration, since the information regarding the lower limit margin value and / or the upper limit margin value is notified to the user by the margin value notification means, the user can use the load sensor based on the lower limit margin value and / or the upper limit margin value. Therefore, it is possible to determine the time to replace and repair the load sensor.

  The margin value notifying means may comprise first display means for displaying a lower limit margin value and / or an upper limit margin value calculated by the margin value calculation means on the screen.

  Further, the apparatus further comprises margin value conversion means for converting the lower limit margin value and / or the upper limit margin value calculated by the margin value calculation section into a weight value, and the margin value notification section is converted by the margin value conversion section. You may consist of the 2nd display means which displays the conversion weight value of a lower limit margin value, and / or the conversion weight value of an upper limit margin value on a screen.

  According to this configuration, since the value obtained by converting the lower limit margin value and / or the upper limit margin value into the weight value is displayed, the user can easily grasp the time when the load sensor reaches the use limit.

  The margin value calculating means subtracts a value obtained by subtracting a lower limit value of the output digital value range from the zero point A / D conversion value which is a lower limit value of the output range of the digital value at the present time. You may be comprised so that it may calculate as a margin value.

  In addition, the lower limit margin value calculated by the margin value calculation means is compared with a preset first tolerance value to determine whether the lower margin margin value is less than the first tolerance value. And a first alarm output means for outputting a first alarm when the lower limit margin value is determined to be less than the first allowable value by the first determination means. Also good.

  According to this configuration, by outputting the first alarm, the user can easily know that the load sensor must be replaced and repaired.

  In addition, the margin value calculation means sets the zero point A / D conversion value, which is a lower limit value of the output range of the digital value at the present time, in advance corresponding to the size of the measurable weight range. The upper limit value of the output range of the digital value at the present time is calculated by adding the maximum change amount of the output digital value of the / D converter, and the upper limit value of the output range of the digital value is calculated as the digital value that can be output. A value subtracted from the upper limit value of the range may be calculated as the upper limit margin value.

  In addition, the upper limit margin value calculated by the margin value calculation means is compared with a preset second tolerance value to determine whether or not the upper margin margin value is less than the second tolerance value. And a second alarm output unit for outputting a second alarm when the second determination unit determines that the upper limit margin value is less than the second allowable value. Also good.

  According to this configuration, by outputting the second alarm, the user can easily know that the load sensor must be replaced and repaired.

  Further, a first function for obtaining a first function for predicting a future value of the lower limit margin value based on the lower limit margin value calculated by the margin value calculation means within a predetermined period before the current time point. A first time period for calculating a future value of the predicted lower limit margin value to be less than a preset first allowable value from the current time point based on the first function and the derivation means. You may further provide a period calculation means and the 1st alerting | reporting means which alert | reports the information regarding the period calculated by the said 1st period calculation means.

  According to this configuration, the information regarding the above-described period (for example, the number of days) is notified, so that the user can easily grasp the time when the load sensor should be replaced and repaired.

  Further, a second function for obtaining a second function for predicting a future value of the upper limit margin value based on the upper limit margin value calculated by the margin value calculation means within a predetermined period before the present time. A second time period for calculating a future value of the predicted upper limit margin value to be less than a second allowable value set in advance from the current time point based on the second function; You may further provide a period calculation means and the 2nd alerting | reporting means which alert | reports the information regarding the period calculated by the said 2nd period calculation means.

  According to this configuration, the information regarding the above-described period (for example, the number of days) is notified, so that the user can easily grasp the time when the load sensor should be replaced and repaired.

  Further, the weight value conversion means for further converting the weight value converted by the weight value conversion means into a weight value, and the weight value display means for displaying the weight value converted by the weight value conversion means on the screen. You may have.

  The present invention has the above-described configuration, and provides an effect that it is possible to provide a weighing device that allows the user to determine when the load sensor reaches the use limit.

It is a block diagram which shows an example of a structure of the weighing | measuring apparatus of embodiment of this invention. It is a flowchart which shows an example of operation | movement of the weighing | measuring apparatus of embodiment of this invention. It is a flowchart which shows an example of operation | movement of the weighing | measuring apparatus of embodiment of this invention. (A) shows the output possible digital value range etc. of the A / D converter in the weighing device of the embodiment of the present invention, (b) shows the input possible analog voltage range etc. of the A / D converter, (C) is a figure which shows the measurable weight range of the weighing device. It is a figure which shows an example of the method of calculating the days required until the predicted value of a lower limit margin value becomes less than a lower limit allowable value using the prediction function of a lower limit margin value in the weighing | measuring apparatus of embodiment of this invention.

  The present invention relates to a weighing device equipped with a load sensor such as a load cell. In such a weighing device, for example, the output voltage of the load sensor is amplified by an amplifier circuit, and then converted into a digital value by an A / D converter. Is converted to That is, the output voltage of the load detection means having the load sensor and the amplifier circuit is converted into a digital value by the A / D converter. This digital value is further converted into a weight value and displayed on a display, for example.

  The load sensor deteriorates (output characteristics change) depending on the use environment, use period, and the like. For example, in the case of a strain gauge type load cell in which a strain gauge is affixed to a metal elastic body (straining body), there are changes in insulation resistance due to moisture and the like, corrosion of the strain gauge, deterioration due to plastic deformation of the metal elastic body, etc. . When the load sensor deteriorates, the output voltage range of the load sensor corresponding to the measurable weight range of the weighing device moves in the load load direction or in the reverse direction, and accordingly, load detection means (amplification) input to the A / D converter. Circuit) output voltage range moves in the load direction or in the opposite direction. In the A / D converter, an analog voltage range that can be input normally and a digital value range that can be output corresponding to the analog voltage range are defined. The weighing device is manufactured with some margin so that the output voltage range of the load detection means is within the range of the analog voltage range that can be input to the A / D converter. When the output voltage range of the load detection means moves due to deterioration and the upper limit value exceeds the upper limit value of the analog voltage range that can be input to the A / D converter, or the lower limit of the output voltage range of the load detection means When the value is less than the lower limit value of the analog voltage range that can be input to the A / D converter, normal A / D conversion cannot be performed and erroneous weighing occurs, so that it cannot be used as a weighing device. In such a case, the load detection means (load sensor) must be replaced and repaired.

  Based on the above, the present invention realizes a weighing device that enables the user to determine when the load detection means (load sensor) reaches the use limit.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the following description, the same or corresponding elements are denoted by the same reference symbols throughout all the drawings, and redundant description thereof is omitted. Further, the present invention is not limited to the following embodiment. Moreover, the numerical value illustrated below is an example, and is not limited to the numerical value.

(Embodiment)
The present invention can be applied to various weighing devices such as a platform scale, a fee scale, and a weight sorter. For example, in this embodiment, a case where the weighing device is a platform scale will be described.

  FIG. 1 is a block diagram illustrating an example of a configuration of a weighing device according to an embodiment of the present invention.

  The weighing device includes a holding means 1 for holding an object to be weighed, a load sensor 2, an amplifier circuit 3, an A / D converter 4, a control device 5, an operation input unit 6, a display unit 7, A clock 8 is provided. Here, the weighing unit 11 includes the holding means 1, the load sensor 2, the amplifier circuit 3, and the A / D converter 4. The holding means 1 in the weighing device (table scale) is, for example, a weighing table whose planar shape is a square or substantially square plate member, and the weighing table (plate member) is a load sensor from below. 2 is supported by 2. This is a well-known configuration, and an object to be weighed is placed on a weighing table and its weight is measured.

  The load sensor 2 is composed of, for example, a strain gauge type load cell, supports the holding unit 1, and outputs an analog load signal (voltage) corresponding to a load applied to the amplifier circuit 3. The amplifier circuit 3 amplifies the analog load signal input from the load sensor 2 and outputs it to the A / D converter 4. In the A / D converter 4, the analog load signal (voltage) input from the amplifier circuit 3 is A / D converted into a digital value Wad and output to the control device 5. Here, the analog load signal input to the A / D converter 4 is generated by the load detection means 12 including the load sensor 2 and the amplifier circuit 3.

  The operation input unit 6 includes an operation unit that performs operations such as turning on and off the weighing device and an input unit that inputs a set value of an operation condition of the weighing device. The display unit 7 includes a display device that displays a weight value or the like on a screen (display screen). For example, the operation input unit 6 and the display unit 7 may be integrated by a touch screen display.

  The clock 8 is formed of a real time clock, for example, and provides date information (year, month, day, etc.) to the control device 5.

  The control device 5 is constituted by, for example, a microcontroller or the like, and includes an arithmetic control unit 5a including a CPU and the like, and a storage unit 5b including a RAM and a ROM. The arithmetic control unit 5a controls the entire weighing device by executing an execution program of the CPU stored in the storage unit 5b by the CPU.

  The control device 5 includes a weight value conversion means, a zero point adjustment means, a margin value calculation means, a margin value conversion means, first and second determination means, first and second function derivation means, first and second. It functions as a period calculation means, weight value conversion means, and the like. The display unit 7 functions as a margin value notification means (first and second display means), first and second alarm output means, first and second notification means, weight value display means, and the like.

  Next, an example of the operation of the weighing device will be described. Note that all the information and the like necessary for the control device 5 to control the operation of the weighing device are stored in the storage unit 5b, and all the information to be stored during the operation is stored in the storage unit 5b.

  First, the normal weighing operation of the weighing device will be described.

  When the user places an object to be weighed on the holding means 1, the load sensor 2 supporting the holding means 1 outputs an analog load signal corresponding to the load applied, and the signal is amplified by the amplifier circuit 3. . The analog load signal amplified by the amplifier circuit 3 is A / D converted into a digital value Wad by the A / D converter 4 and input to the control device 5. The control device 5 converts the output signal (Wad) of the A / D converter 4 into a weight value (Wd), and displays the weight value on the screen of the display unit 7.

  Here, the operation (processing) of the control device 5 will be described in detail.

  The control device 5 converts the output digital value Wad of the A / D converter 4 into an internal measurement value (measurement value) Wn based on a conversion equation represented by the following equation (1).

Wn = k (Wad−Wi) −Wz (1)
Here, k is a span coefficient, which is a preset value. Wi is a zero initial value, and Wz is a zero adjustment value. The zero-point initial value Wi is a preset value, and the zero-point adjustment value Wz is initially set to 0 (for example, when the weighing device is shipped from the factory) and is updated by a zero-point adjustment process described later.

  The digital value Wad in the equation (1) may be an average value of a plurality of output values output continuously from the A / D converter 4 at a predetermined time (for example, 200 ms) interval. A value obtained by smoothing the output value of the A / D converter 4 with a digital filter may be used.

  Further, the control device 5 converts the internal measurement value Wn into a weight value Wd based on the equation (2), and displays the weight value Wd on the screen of the display unit 7.

Wd = Wn / D (2)
In equation (2), the value of Wn / D on the right side is rounded (rounded off after the decimal point) to calculate the weight value Wd. Here, D is a conversion coefficient (predetermined value), for example, D = 4. This means that the internal weighing value Wn is calculated with an accuracy (resolution) of D times (for example, 4 times) the displayed weight value Wd.

  The following equation (3) is obtained from the above equations (1) and (2). In the equation (3), the weight value Wd can be calculated by performing the above-described fraction processing on the value on the right side.

Wd = {k (Wad−Wi) −Wz} / D (3)
In the present weighing device, for example, at the time of factory shipment, the zero point initial value Wi and the span coefficient k are set, and the respective values are stored in the storage unit 5b. In this setting process, in the above-described equation (1), Wz = 0, and the zero-point initial value Wi is set so that the internal measurement value Wn becomes 0 when the object to be measured is not placed on the holding means 1, that is, The value of the output digital value Wad at that time is set to the zero initial value Wi.

  After the zero-point initial value Wi is set as described above, when a sample product having a known weight value M is placed on the holding means 1, in equation (1), Wz = 0 and the internal weighing value Wn is D The value of the span coefficient k is set so as to be × M.

  Next, an example of the characteristic operation of the weighing device will be described. 2 and 3 are flowcharts showing an example of this operation. Here, in the control device 5, the respective values of the span coefficient k, the zero initial value Wi, and the conversion coefficient D are stored in advance in the storage unit 5b. Further, the value of the zero point adjustment value Wz, for example, “0” is stored when it is an initial set value, but is updated each time a zero point adjustment process described later is performed.

  In the present weighing device, when the user performs an operation for adjusting the zero point on the operation input unit 6, a zero-point adjustment command signal is input from the operation input unit 6 to the control device 5, and the control device 5 performs zero-point adjustment processing. Made.

  Here, the user confirms that there is no object to be weighed in the holding means 1, and performs an operation for adjusting the zero point on the operation input unit 6. As a result, a zero adjustment command signal is output from the operation input unit 6 to the control device 5. The operation input unit 6 is provided with, for example, a zero adjustment key, and a zero adjustment command signal is output to the control device 5 when the zero adjustment key is depressed.

  When the zero adjustment command signal is input, the control device 5 starts a series of processes shown in FIGS. 2 and 3 and first performs a zero adjustment process (step S1). That is, the control device 5 starts a series of processes shown in FIGS. 2 and 3 each time a zero adjustment command signal is input.

  In this zero point adjustment processing, the control device 5 uses the value of the output value Wad (zero point A / D conversion value ADZ) of the A / D converter 4 when there is no object to be weighed in the holding means 1 as described above. Then, the internal weighing value Wn is calculated based on the equation (1), the calculated internal weighing value Wn and the zero adjustment value Wz are added, and this addition value is stored as a new zero adjustment value Wz. . As a result, when the calculated internal weighing value Wn is not zero, the value of the zero adjustment value Wz included in the equation (1) is changed (updated) so that the internal weighing value Wn becomes zero. .

  Next, the control device 5 performs a margin value calculation process (step S2). In this margin value calculation process, the above-described zero point A / D conversion value ADZ is used to calculate the lower limit margin value PL1, the weight converted lower limit margin value PL2, the upper limit margin value PU1, and the following equations (4) to (7). The weight conversion upper limit margin value PU2 is calculated. Further, the margin values PL1 and PU1 are stored in a predetermined area (margin value storage area) of the storage unit 5b together with the date (year / month / day) acquired from the clock 8 at that time. Here, the date and the margin values PL1 and PU1 are stored in association with each other.

PL1 = ADZ-ADL (4)
PL2 = k · PL1 / D (5)
PU1 = ADU− (ADZ + ADM) (6)
PU2 = k · PU1 / D (7)
Here, ADL in the equation (4) is a lower limit value (minimum value) of the digital value range (outputtable digital value range) XD that can be output by the A / D converter 4. In addition, ADU in the equation (6) is an upper limit value (maximum value) of the output possible digital value range XD of the A / D converter 4.

  FIG. 4 shows the relationship between input / output signals and the like of the A / D converter 4. 4A shows the output possible digital value range XD of the A / D converter 4 and FIG. 4B shows the possible input range of the analog voltage of the A / D converter 4 (input possible). Analog voltage range) XA and the like are shown, and FIG. 4C is a diagram showing a measurable weight range (measurable weight range) α of the weighing device.

  The A / D converter 4 has an input possible analog voltage range XA (a range where the lower limit value is AL and the upper limit value is AU) and a corresponding output possible digital value depending on the specifications. A range XD is defined. Therefore, in this weighing device, the lower limit value ADL and the upper limit value ADU of the output possible digital value range XD of the A / D converter 4 are stored in advance in the storage unit 5 b of the control device 5.

  Further, ADM in the equation (6) is an output change amount (maximum output change amount) of the output digital value of the A / D converter 4 determined in accordance with the size of the measurable weight range α of the weighing device. The ADM value is also stored in advance in the storage unit 5b of the control device 5. In this weighing device, as in a general weighing device, the maximum weight value Adm and the measurable weight range α (range of 0 to Adm) that can be measured are determined in advance. Here, the size (size) of the measurable weight range α is also indicated by Adm, and the output change amount ADM of the A / D converter 4 corresponding to the size Adm of the range α is expressed by the following equation (8). It can be calculated.

ADM = D · Adm / k (8)
This equation (8) is obtained as follows, for example.

  For example, consider a case where the zero adjustment value Wz is set to 0 at the time of factory shipment or the like. In this case, the output digital value Wad of the A / D converter 4 when the object to be weighed having the maximum value (Adm) in the measurable weight range α is weighed is defined as Wadm, and the weight value calculated at that time When Wd is Wdm, the following equation (3-1) is established from the equation (3).

Wdm = {k (Wadm−Wi)} / D (3-1)
In addition, when the zero-point adjustment value Wz is set to 0, the A / when the weighing object having the minimum value (0) of the measurable weight range α is measured (that is, when there is no weighing object) If the output digital value Wad of the D converter 4 is Wads and the weight value Wd calculated at that time is Wds, the following expression (3-2) is established from the expression (3).

Wds = {k (Wads−Wi)} / D (3-2)
Here, the size Adm of the measurable weight range α is Wdm−Wds, and the output change amount ADM of the A / D converter 4 corresponding to the size Adm of the range α is Wadm-Wads. Therefore, the magnitude Adm of the measurable weight range α is expressed by the following formula based on the formulas (3-1) and (3-2).

Adm = Wdm−Wds
= K (Wadm-Wads) / D
= K · ADM / D
Here, if Adm = k · ADM / D is modified, equation (8) is obtained.

  In the present weighing apparatus, for example, by inputting the maximum weight value Adm from the operation input unit 6 in advance, the control device 5 calculates and stores the value of ADM based on the equation (8). Note that the ADM value may be calculated in advance, and the calculated value may be input to the control device 5 and stored.

  In the present weighing device, as shown in FIG. 4, the planned output voltage range of the load detecting means 12 corresponding to a predetermined measurable weight range α, that is, the planned input voltage range β of the A / D converter 5 is For example, the range β (0) is set so as to be within the range of the analog voltage range XA that can be input to the A / D converter 5. However, if the output range of the load sensor 2 is changed due to the movement of the zero point of the load sensor 2 due to deterioration of the load sensor 2 or the like, the input voltage planned range β of the A / D converter 5 also changes. For example, the range β (0) originally planned may change to the range β (1). In this case, the planned output range XO of the A / D converter 5 changes from the planned output range XO (0) corresponding to the first planned input voltage range β (0) to the planned input voltage range β (1) after the change. It changes to the corresponding scheduled output range XO (1).

  When the planned output range XO further changes (moves) and the upper limit value ADH of the planned output range XO exceeds the upper limit value ADU of the output possible digital value range XD, for example, the maximum measurable weight range α A value corresponding to the value (Adm) cannot be output, and normal A / D conversion operation cannot be performed.

  Further, when the output range of the load sensor 2 changes in the opposite direction due to the zero point of the load sensor 2 moving in the opposite direction due to deterioration of the load sensor 2 or the like, the expected input voltage range β of the A / D converter 5 is also changed. In some cases, it changes in the reverse direction and the planned output range XO moves in the reverse direction so that the lower limit value ADZ of the planned output range XO is less than the lower limit value ADL of the output possible digital value range XD. For example, a value corresponding to the minimum value (0) of the measurable weight range α cannot be output, and normal A / D conversion operation cannot be performed.

  Therefore, in the present embodiment, the lower limit margin value PL1 and the weight conversion lower limit margin value PL2 calculated in step S2, and the upper limit margin value PU1 and the weight conversion upper limit margin value PU2 are displayed on the screen of the display unit 7 (step S3). ). Thereby, the user can grasp the degree of deterioration of the load sensor 2 from the displayed margin value, can determine the time when the load sensor 2 becomes the use limit, and can easily replace and repair the load sensor 2. Can be determined.

  Note that either the lower limit margin value PL1 or the weight conversion lower limit margin value PL2 may be calculated and displayed. Similarly, either the upper limit margin value PU1 or the weight conversion upper limit margin value PU2 may be calculated and displayed. Here, since the lower limit margin value PL1 and the upper limit margin value PU1 are values of the output level of the A / D converter 4, the weight conversion lower limit margin value PL2 and the weight conversion upper limit margin value PU2 are calculated and displayed. However, since the value converted into the weight is displayed, the user can conveniently recognize that the load sensor 2 cannot be used if the zero point changes by several tens of grams.

  Next, the control device 5 determines whether or not the lower limit margin value PL1 is less than the lower limit allowable value (first allowable value) PLE. If the lower limit margin value PL1 is less than the lower limit allowable value PLE, display is performed. The alarm is output (displayed) to the unit 7 (steps S4 and S5).

  Further, it is determined whether or not the upper limit margin value PU1 is less than the upper limit allowable value (second allowable value) PUE. If the upper limit margin value PU1 is less than the upper limit allowable value PUE, an alarm is output to the display unit 7. (Display) (steps S6 and S7).

  The lower limit allowable value PLE and the upper limit allowable value PUE are set in advance and stored in the storage unit 5b of the control device 5. The lower limit allowable value PLE and the upper limit allowable value PUE may be equal, and if the output possible digital value range XD of the A / D converter 4 is, for example, 200,000, for example, a value of 1/2000 thereof (100) or the like may be set.

  As an alarm in steps S5 and S7, for example, the display unit 7 displays a message such as “The load sensor is approaching its limit. Please replace and repair the load sensor.” In the case of the alarm in step S5, the content indicating that the lower limit margin value is small may be additionally displayed, and in the case of the alarm in step S7, the content indicating that the upper limit margin value is small may be additionally displayed. .

  When displaying the alarm of steps S5 and S7, this flow (a series of processes shown in FIGS. 2 and 3) is terminated, and when the alarm of steps S5 and S7 is not displayed, that is, the lower limit margin value PL1. Is not less than the lower limit allowable value PLE and the upper limit margin value PU1 is not less than the upper limit allowable value PUE, the process proceeds to the next step S9 (step S8).

  In step S9, the date stored today (today's date) stored together with the margin value in the margin value storage area of the storage unit 5b is compared with the date stored last time, and whether these dates have changed. If the date is not changed, this flow is terminated. If the date is changed, the process proceeds to step S10.

  In step S10, the average value PLa of all lower limit margin values PL1 of the previously stored date (for example, yesterday's date) stored in the margin value storage area of the storage unit 5b is calculated, and the upper limit margin value PU1 is set. The average value PUa is calculated, these average values are stored together with dates in a predetermined area (representative value storage area) of the storage unit 5b, and the margin values PL1 and PU1 used for calculating the average values PLa and PUa and the date are margined. Erase from the value storage area. In this flow, the average value is used as the representative value of the lower limit and upper limit margin values PL1 and PU1 in one day, but a median value may be used.

  Next, in step S11, it is determined whether or not the average value PLa of the lower limit margin value PL1 and the average value PUa of the upper limit margin value PU1 equal to or greater than a predetermined number of days (n days, n ≧ 2) are stored. If it is less than the number of days, this flow is ended, and if it is stored for a predetermined number of days or more, the process proceeds to step S12.

  Next, in step S12, a function for predicting the future value of the lower limit margin value PL1 (prediction function of the lower limit margin value PL1) is obtained, and a function for predicting the future value of the upper limit margin value PU1 (upper limit margin). A prediction function of the value PU1).

  Specifically, an approximate function having the number of days Td as an independent variable is obtained by, for example, the least square method using the average value PLa of the lower limit margin value PL1 for the latest predetermined number of days (n days), and the function is used as the lower limit margin. Let it be a prediction function of the value PL1. This prediction function is expressed by equation (9). Similarly, using the average value PUa of the upper limit margin value PU1 for the latest predetermined number of days (n days), an approximate function having the number of days Td as an independent variable is obtained by, for example, the least square method, and the function is determined as the upper limit margin value PU1. Is a prediction function. This prediction function is expressed by equation (10).

PL1 = f (Td) (9)
PU1 = g (Td) (10)
These functions are obtained as a linear function, for example. Note that it may be obtained as a function other than a linear function (for example, a quadratic function).

  Next, in step S13, for the lower limit and upper limit margin values PL1 and PU1, the predicted values of the lower limit and upper limit margin values PL1 and PU1 are set to the lower limit and upper limit within a predetermined prediction period (Tp) using the respective prediction functions. The number of days (x) required to become less than the allowable values PLE and PUE is calculated. Here, the number of days x is calculated by counting the present day (today) as the first day.

  FIG. 5 is a diagram illustrating an example of a method for calculating the number of days x. FIG. 5 shows the lower limit margin value PL1, but the same applies to the upper limit margin value PU1.

  In the case of FIG. 5, a linear function (approximation) having the number of days Td as an independent variable by the least square method using the average value PLa of the lower limit margin value PL1 for seven days (n = 7) (that is, seven average values PLa). Function), which is used as a prediction function of the lower limit margin value PL1 [see equation (9)]. The prediction period Tp is 23 days from now (8 ≦ Td ≦ 30).

  In this case, within the forecast period Tp, the minimum number of days is calculated if there is a number of days Td in which the lower limit margin value PL1 (predicted value) is less than the lower limit allowable value PLE, and if the minimum number of days is Td1, , X = Td1-n. In the case of FIG. 5, since Td1 = 20 and n = 7, the number of days x can be calculated as 13 (days).

  Similarly, a prediction function [see equation (10)] is obtained for the upper limit margin value PU1, and if there is a number of days Td in which the upper limit margin value PU1 (predicted value) is less than the upper limit allowable value PUE within the prediction period Tp. The minimum number of days is calculated. If the minimum number of days is Td2, the number of days x is calculated by x = Td2-n.

  Further, in each of the expressions (9) and (10), for example, using Te as a variable, instead of Td, Te + n (n is a predetermined value, “7” in the above example) is substituted, and (9 ) (Formula 1) corresponding to Formula (1) and Formula (Formula 2) corresponding to Formula (10) may be created, and Formula 1 and Formula 2 may be used as prediction functions. In this case, if there is a number of days Te that is less than the allowable values PLE and PUE within the prediction period, the minimum number of days is calculated, and the minimum number of days becomes the number of days x.

  When the lower limit margin value PL1 decreases with the passage of days, the upper limit margin value PU1 increases with the passage of days, and when the lower limit margin value PL1 increases with the passage of days, The upper limit margin value PU1 decreases with the passage of days. Therefore, the number of days x is not calculated simultaneously for both the lower limit margin value PL1 and the upper limit margin value PU1, and when calculated, only one of them is calculated.

  Further, in this example, the number of days x is not calculated unless any margin value PL1, PU1 is less than the allowable values PL1, PUE within the prediction period Tp.

  Next, when the number of days x can be calculated in step 13, the process proceeds to step S15, and when it cannot be calculated, this flow is ended (step S14).

  In step S15, when the number of days x is obtained in step 13, the display unit 7 is notified of information related to the number of days x. This notification is displayed on the screen of the display unit 7 such as, for example, “The usage limit of the load sensor is approaching. Replace the load sensor within x days.”

  In the above, the data collection period for calculating the average values PLa and PUa of the lower limit and upper limit margin values is set as one day unit, and the period until the margin values PL1 and PU1 are less than the allowable values PL1 and PUE. However, the period may be changed, for example, in units of one week each.

  In addition, the prediction period Tp is not necessarily set. However, by setting the prediction period Tp, it is possible to notify when the load sensor 2 cannot be used only in the near future (within the prediction period Tp). Useful. When the prediction period Tp is not set, for example, it is possible to notify about months or years ahead, and in such a case, the user recognizes that preparation for replacement of the load sensor 2 is not yet necessary. it can.

  In the above, every time the date is changed so that the storage capacity of the storage unit 5b is small, the margin values PL1, PU1 of the immediately preceding date are calculated and stored, and the date The margin values PL1 and PU1 are erased. And although each prediction function of a lower limit and an upper limit margin value is calculated | required using each average value PLa and PUa for predetermined days, it does not restrict to this.

  For example, when the storage capacity of the storage unit 5b is sufficiently large, when the calculated margin values PL1 and PU1 are stored in the margin value calculation process in step S2, the date (year / month / day) and time from the clock 8 are stored. Date and time information is acquired, and the margin values PL1 and PU1 are stored in the margin value storage area together with the date and time information.

  When the date is changed, the lower limit margin value PL1 is predicted using the date and time (time) as an independent variable using all the lower limit margin values PL1 for a predetermined number of days stored in the margin value storage area. Similarly, a prediction function of the upper limit margin value PU1 having the date and time (time) as an independent variable may be calculated using all the upper limit margin values PU1 for a predetermined number of days.

  If these prediction functions are used, for example, in step S13, it is possible to calculate until the time when the lower limit and upper limit margin values PL1, PU1 are less than the permissible values PLE, PUE. Therefore, information regarding the number of days x may be notified as in step S15.

In the present embodiment, every time the zero adjustment process is performed, the lower limit margin values PL1, PL2 and the upper limit margin values PU1, PU2 are calculated and displayed on the display unit 7, so that the user is displayed. It becomes possible to determine the time when the load sensor 2 reaches the use limit from the margin value, and the time for replacement and repair of the load sensor 2 can be easily determined.
In the present embodiment, when the lower limit margin value PL1 is less than the lower limit allowable value PLE, and when the upper limit margin value PU1 is less than the upper limit allowable value PUE, an alarm is displayed on the screen of the display unit 7. Therefore, the user can easily know that the load sensor 2 must be replaced and repaired. Further, the user can determine the time when the load sensor 2 reaches the use limit from the margin value displayed at this time, and can use the measuring device while performing the zero point adjustment processing until then.

  Further, in the present embodiment, a prediction function of the lower limit and upper limit margin values PL1, PU1 is obtained, and the number of days x until the lower limit margin value PL1 (predicted value) becomes less than the lower limit allowable value PLE or the upper limit margin value PU1. By displaying information regarding the number of days x from when the (predicted value) becomes less than the upper limit allowable value PUE, the user can easily grasp the time when the load sensor 2 should be replaced and repaired.

  In this embodiment, each time the zero adjustment process is performed, a series of processes shown in FIGS. 2 and 3 are performed. Here, in the present embodiment, the zero point adjustment process is started manually. However, when the object to be weighed is not held by the holding means 1, the zero point adjustment process is automatically started at a predetermined timing. May be.

  Moreover, although this embodiment demonstrated the case where a weighing | measuring apparatus was a platform scale, it is the same also in the case of a fee scale. When the weighing device is a fee scale, the holding means 1 is constituted by, for example, a weighing pan on which an object to be weighed is placed.

  In addition, the weighing device is a weight sorter that measures the weight of an object to be transported on a conveyor and sorts, for example, a standard product (non-defective product) or a non-standard product (defective product) based on the weight. May be. In this case, the holding means 1 is configured by the conveyor, and the conveyor is supported by the load sensor 2. In the case of this weight sorter, the control device 5 detects the object to be weighed on the conveyor based on the output signal of the load sensor 2 (the output signal of the A / D converter 4), the detection signal of the object to be weighed sensor and the like. It may be configured to detect the presence / absence, automatically start the zero point adjustment process at a predetermined timing when there is no object to be weighed on the conveyor, and perform a series of processes including the zero point adjustment process.

  Also, a weighing device provided with a plurality of weighing units 11 may be used. In this case, the plurality of A / D converters 4 are replaced with one A / D converter 4, and the outputs of the plurality of load detection means 12 are input to one A / D converter 4 via a multiplexer. It may be configured to be. For example, when the weighing device is a combination weigher, each of a plurality of hoppers (weighing hoppers) is supported by a load sensor (load cell) and is configured to measure the weight of an object to be weighed in each hopper. Is selected so that the object to be weighed is within a predetermined weight range, and the object to be weighed is discharged from the hopper holding the object to be weighed. In this case, each hopper serves as the holding means 1 and has a configuration in which a plurality of weighing units 11 are provided. In such a combination weigher, when a supply device (for example, a supply hopper) for an object to be weighed is provided for each of the hoppers (weighing hoppers) described above, the control device, for example, sequentially feeds the weighing hoppers one by one. The supply of the object to be weighed may be stopped, the zero point adjustment process may be automatically started for the empty weighing hopper, and a series of processes including the zero point adjustment process may be performed. Further, even when the weighing device is a track scale, a configuration in which a plurality of weighing units 11 are provided is provided.

  That is, the present invention can be applied to various weighing devices configured to convert an analog load signal voltage output from a load sensor into a digital value using an A / D converter.

  INDUSTRIAL APPLICABILITY The present invention is useful as a weighing device that enables a user to determine when the load sensor reaches the use limit.

DESCRIPTION OF SYMBOLS 1 Holding means 2 Load sensor 3 Amplifying circuit 4 A / D converter 5 Control apparatus 6 Operation input part 7 Display part 8 Clock 11 Weighing unit 12 Load detection means

Claims (10)

A load sensor that supports a holding means for holding an object to be measured and outputs an analog load signal voltage corresponding to a load applied;
An analog voltage range that can be input and a digital value range that can be output corresponding to this range are defined, and an analog load signal voltage output from the load sensor is A / D converted to output a digital value. A D converter;
Weighing value conversion means for converting a digital value output from the A / D converter into a weighing value corresponding to the weight of the object to be weighed;
When the object to be weighed is not held in the holding means, the measurement value obtained by converting the zero point A / D conversion value, which is a digital value output from the A / D converter, by the measurement value conversion means is zero. Is not zero point adjustment means for performing zero point adjustment processing so that the measurement value becomes zero,
When the zero point adjustment process is performed, based on the zero point A / D conversion value, the output range of the current digital value of the A / D converter corresponding to a predetermined measurable weight range and the output A margin value for calculating at least one of a lower limit margin value that is a difference between lower limit values of two ranges with a range of possible digital values and an upper limit margin value that is a difference between upper limit values of the two ranges. A calculation means;
A measuring apparatus comprising: margin value notifying means for notifying information on a lower limit margin value and / or an upper limit margin value calculated by the margin value calculating means. The margin value notification means includes:
Comprising a first display means for displaying a lower limit margin value and / or an upper limit margin value calculated by the margin value calculation means on the screen;
The weighing device according to claim 1. A margin value conversion means for converting the lower limit margin value and / or the upper limit margin value calculated by the margin value calculation means into a weight value;
The margin value notification means includes:
It comprises second display means for displaying the converted weight value of the lower limit margin value and / or the converted weight value of the upper limit margin value converted by the margin value conversion means on the screen.
The weighing device according to claim 1. The margin value calculating means includes:
A value obtained by subtracting the lower limit value of the digital value range that can be output from the zero point A / D conversion value that is the lower limit value of the output range of the digital value at the present time point is calculated as the lower limit margin value. ,
The weighing device according to claim 1. A first determination for determining whether or not the lower limit margin value is less than the first tolerance value by comparing the lower limit margin value calculated by the margin value calculating means with a preset first tolerance value. Means,
A first alarm output means for outputting a first alarm when the lower limit margin value is determined to be less than the first allowable value by the first determination means;
The weighing device according to any one of claims 1 to 4. The margin value calculating means includes:
The zero point A / D conversion value, which is the lower limit value of the output range of the digital value at the present time, is set to the output digital value of the A / D converter that is determined in advance corresponding to the size of the measurable weight range. A value obtained by calculating the upper limit value of the output range of the digital value at the present time by adding the maximum change amount and subtracting the upper limit value of the output range of the digital value from the upper limit value of the range of the digital value that can be output Is calculated as the upper limit margin value,
The weighing device according to any one of claims 1 to 5. A second determination for determining whether or not the upper limit margin value is less than the second tolerance value by comparing the upper limit margin value calculated by the margin value calculation means with a preset second tolerance value. Means,
A second alarm output means for outputting a second alarm when the second determination means determines that the upper limit margin value is less than the second allowable value;
The weighing device according to any one of claims 1 to 6. First function deriving means for obtaining a first function for predicting a future value of the lower limit margin value based on the lower limit margin value calculated by the margin value calculation means within a predetermined period before the present time. When,
First period calculation means for calculating a period required from the present time until a future value of the predicted lower limit margin value is less than a preset first allowable value based on the first function; ,
A first notification means for notifying information related to the period calculated by the first period calculation means;
The weighing device according to any one of claims 1 to 7. Second function derivation means for obtaining a second function for predicting a future value of the upper limit margin value based on the upper limit margin value calculated by the margin value calculation means within a predetermined period before the present time. When,
Second period calculating means for calculating a period required from the present time until a future value of the predicted upper limit margin value is less than a preset second allowable value based on the second function; ,
A second informing means for informing information related to the period calculated by the second period calculating means;
The weighing device according to any one of claims 1 to 8. A weight value conversion means for further converting the measurement value converted by the measurement value conversion means into a weight value;
A weight value display means for displaying the weight value converted by the weight value conversion means on a screen;
The weighing device according to any one of claims 1 to 9.

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