JP2011133485A - Rotating type weighing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotating type weighing apparatus frequently acquiring a sufficiently stable zero point signal. <P>SOLUTION: A plurality of measuring devices 2-1 through 2-n are disposed rotatably around the rotation center. A carrying-in position A where articles are sequentially carried into the measuring devices 2-1 through 2-n and a carrying-out position B where articles are sequentially carried out of the measuring devices 2-1 through 2-n are disposed at a distance in a predetermined direction on a rotation trajectory drawn by rotation of the measuring devices 2-1 through 2-n in the predetermined direction. A zero point weight signal is compensated based on the deviation of output acquired by each of the measuring devices 2-1 through 2-n whenever each of the measuring devices 2-1 through 2-n rotates a plurality of times from a carrying out position B to carrying in position A. The compensation is performed while the amount of deviation is reduced. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rotary weighing device that weighs a loaded article while a load detection means rotates, and more particularly to zero point adjustment.

  Conventionally, as zero-point adjustment technology in a rotary weighing device, for example, there are those disclosed in Patent Documents 1 and 2.

  In the technique of Patent Document 1, a plurality of load detection means are provided so as to be rotatable around the center of rotation, and a carry-in position for sequentially carrying articles to each load detection means on a rotation locus drawn by the rotation of each load detection means. And an unloading position for sequentially discharging articles from each load detecting means, and the output of the load detecting means when the article passes from the unloading position to the loading position without being loaded is used as a zero point signal. It is.

  In the technique of Patent Document 2, load detection means is provided along the circumferential direction of the rotating body, and the output of the load detection means when no article is loaded on all of the load detection means is used as a zero signal. It is.

Japanese Patent No. 2756849 JP 2004-189248 A

  In the technique of Patent Document 1, when each load detection means rotates at high speed, the time for the load detection means to pass from the carry-out position to the carry-in position is short, so the output of the load detection means is not sufficiently stable, and the zero signal May vary. Also, with the technique of Patent Document 2, it is possible to obtain a stable zero signal. However, the state in which the article is not loaded on the total load detecting means is, for example, only before the start of the production of the article by the apparatus using the technique of Patent Document 2. The load detection means drifts in response to changes in ambient temperature and humidity. In addition, if an article loaded on the load detection means is wet, water will stay in the load detection means every time an article is loaded, and the zero signal will also drift. Therefore, if the zero point signal is acquired only once before the start of production and the zero point signal is continuously used as it is, accurate weight measurement cannot be performed. If an attempt is made to put the full load detection means in the state of no article loading during production, production must be forcibly stopped, resulting in a reduction in production efficiency.

  An object of the present invention is to provide a rotary weighing device capable of frequently obtaining a sufficiently stable zero signal.

  In the rotary weighing device of one aspect of the present invention, a plurality of load detection means are provided so as to be rotatable around the rotation center, and each load detection means rotates on a rotation locus drawn by rotating in a predetermined direction. A loading position for sequentially loading articles into the load detecting means and a loading position for sequentially unloading the articles from the load detecting means are provided at intervals in the predetermined direction. Further, the no-load state determination means determines whether or not each load detection means is unloaded. Zero point adjustment means performs zero adjustment on the load detection means determined to be unloaded by the no load state determination means during rotation. The zero-point adjusting means is configured such that the no-load load detecting means is operated while the no-load load detecting means, which is the load detecting means determined as no load by the no-load state determining means, rotates from the loading position to the unloading position. At least a part of the generated output signal is a zero point weight signal. When the load detection means rotates a plurality of times without load from the carry-out position to the carry-in position, the corresponding zero point weight is based on the deviation of the output of the load detection means obtained from the load detection means at different times. The signal is zero point weight signal correction means. to correct. The zero-point weight signal correcting means corrects the zero-point weight signal by reducing the deviation.

  If no container is loaded on the load detection means, the zero point weight value storage may be updated by the output of the load detection means. However, this is not possible with a filled container. By the way, the load detection means is unloaded while rotating from the carry-out position to the carry-in position. During this time, the filled container is always discharged. It is conceivable to correct the stored zero signal using the signal of the load detection means in this case. However, since the section from the carry-out position to the carry-in position is short, the output of the load detection means during one rotation from the carry-out position to the carry-in position includes a vibration signal component due to container carry-out. Therefore, when the rotation from the carry-out position to the carry-in position is performed a plurality of times, the deviation of the output of the load detection means obtained at the plurality of times is obtained. Since the amount of vibration noise caused by carrying out the filled container is the same, this deviation cancels out the vibration signal component and includes only the drift of the output of the load detection means due to temperature change and water droplet adhesion. Therefore, the zero point signal is corrected based on this deviation, and the influence of drift is removed.

  The vibration signal component included in the output of the load detection means between the carry-out position and the carry-in position may vary in value, and the output of the load detection means obtained each time the load detection means passes a plurality of times during this period. There may be variations in the deviation. Therefore, the zero signal is prevented from being excessively corrected by correcting the zero signal with the reduced value of the deviation.

  For example, when the deviation obtained as described above is compared with a predetermined value and the deviation is smaller than this value, the zero signal is corrected by this deviation, and the deviation is larger than the predetermined value The zero point signal can be corrected by the predetermined value, or the obtained deviation can be multiplied by a coefficient smaller than 1 and the zero point signal can be corrected by the multiplication value.

  As described above, according to the present invention, the zero signal can be frequently adjusted, and the influence of drift can be eliminated.

1 is a schematic plan view of a rotary weighing device according to an embodiment of the present invention. It is explanatory drawing of the rotation state of the measuring instrument in the rotary type weighing device of FIG. It is a block diagram of the rotary weighing device of FIG. It is a flowchart of the zero point adjustment in the rotary weighing device of FIG. It is a flowchart of the zero point correction | amendment in the rotary weighing device of FIG. It is explanatory drawing of the rotation state of the measuring instrument in the rotary weighing device of other embodiment of this invention.

  A rotary weighing device according to an embodiment of the present invention is implemented, for example, in a weight-type filling device, and includes a plurality of weighing devices 2-1 to 2-n as shown in FIG. These weighing devices 2-1 to 2-n have platforms 4-1 to 4-n on which articles are loaded, and weigh the articles loaded on these platforms 4-1 to 4-n. Load detecting means, for example, load cells 6-1 to 6-n. These weighing devices 2-1 to 2-n are arranged at predetermined angles on a circumference that can be drawn around a certain rotation center, and are arranged so as to rotate around the rotation center. For example, it arrange | positions along the periphery of the disk-shaped rotary body which is not shown in figure. This rotating body is driven at a constant speed, for example, by a driving means (not shown) such as a motor.

  At one place on the circumference, there is a loading position A where the container 8 is loaded every time each of the platforms 4-1 to 4-n reaches the position. A carry-in device, for example, a star wheel 10 is arranged at this carry-in position. Further, there is a carry-out position B at a position away from the carry-in position by a predetermined angle along the circumference in the direction opposite to the rotation direction of the weighing devices 2-1 to 2-n. In the carry-out position B, a carry-out device such as a star wheel 12 is arranged.

  The container 8 loaded on any of the platforms 4-1 to 4-n from the loading position A is filled in the container 8 with a filling device (not shown) while rotating in a predetermined direction indicated by an arrow in FIG. 1. When the filling weight reaches a predetermined weight, the filling is finished and the material is unloaded from the unloading position B. While the platforms 4-1 to 4-n rotate from the carry-out position B to the carry-in position, the platforms 4-1 to 4-n are in an unloaded state.

  Specifically, as shown in FIG. 2, the section d1 from the loading position A is a transition of the weighing signal of the load cells 6-1 to 6-n when the container 8 gets on the platforms 4-1 to 4-8. This is a section in which the container 8 moves during the time t1 for waiting for the response to converge. The section d2 is a section in which the container 8 moves during the container weight measurement time t2 for obtaining the weight of the container 8. d3 is a section in which the container 8 moves during the filling / weight measurement time t3 when the weight is measured while filling the article into the container 8 and the filling is finished when the weight reaches a predetermined weight. d4 is the distance that the container 8 moves during the time t4 waiting for the transient response of the weighing signals of the load cells 6-1 to 6-n generated at the end of filling to converge. d5 is a section in which the container 8 moves during the filled weight measurement time t5 in which the weight of the filled container 8 is measured. d6 is a time period t6 for waiting for the transient response generated in the weighing signal of each load cell 6-1 to 6-n to converge when the filled container is unloaded from the platforms 4-1 to 4-n. This is a section in which the container 8 moves. d7 is a section in which the container 8 moves during the no-load time t7.

  As shown in FIG. 3, the weighing signals of the load cells 6-1 to 6-n are respectively supplied to filter means, for example, low-pass filters 14-1 to 14-n, and amplifying means, for example, amplifiers 16-1 to 16-n. n is supplied to A / D conversion means, for example, A / D converters 18-1 to 18-n. The digital measurement signals of the A / D converters 18-1 to 18-n are supplied to an arithmetic circuit, for example, the CPU 22 via the I / O circuit 20. The A / D converters 18-1 to 18-n perform predetermined sampling so that a digital weighing signal can be obtained a predetermined number of times in each of the container weight measurement time, the filling / weight measurement time, and the filled weight measurement time. Digital conversion is continued every period.

  The CPU 22 uses the RAM 24 as a working area in accordance with a program stored in the ROM 24, and controls the weight measurement of each container 8 based on each digital weighing signal and the start and end of filling of each container 8 with a predetermined weight of an article. Measure the weight of the container after filling and adjust the zero point.

  Such control requires knowing the rotational position of each of the measuring devices 2-1 to 2 -n, so that every time a predetermined measuring device, for example, the measuring device 2-1 reaches a predetermined position, for example, the loading position A. Is provided with a pulse generator 28 for generating an initial pulse signal and generating a rotation pulse signal at a predetermined angle each time each of the measuring devices 2-1 to 2-n reaches a predetermined position, for example, the carry-in position A. . The initial pulse signal and the predetermined angle rotation pulse signal are supplied to the CPU 22 via the I / O circuit 20, and the CPU 22 constitutes a counter by a program, and this counter is reset every time the initial pulse signal is supplied. The predetermined angle rotation pulse signal is counted. The position of each weighing device 2-1 to 2-n is acquired by using the count value of this counter.

  In the following description, the zero point measurement and zero point correction processing performed by the CPU 22 will be described focusing on one weighing instrument in order to avoid confusion with the explanation, but the same applies to other weighing instruments. The CPU 22 performs this process.

  In the state where each measuring device 2-1 to 2-n is stopped at the time of zero adjustment or before the start of production operation, the measuring device to be adjusted, for example, the platform 4-1 of the measuring device 2-1, is not used. A load is applied, and the operator operates a zero-point storing key for zero-point adjustment (not shown), and the digital weighing signal obtained by digitizing the weighing signal of the load cell 6-1 is stored in the RAM 26 as the zero-point weight value Wzi. . Alternatively, each weighing device 2-1 to 2-n is rotated a predetermined number of times in a state where each weighing device 2-1 to 2-n is unloaded, and the weighing signal of each load cell 6-1 to 6-n is digitized. The average values of the digital weighing signals are obtained, and these average values are set as the zero point weight values of the weighing devices 2-1 to 2-n.

  In the state where the measuring devices 2-1 to 2-n are rotated and in production, when the measuring device of interest, for example, the measuring device 2-1, is at the container weight measuring time t2, the measurement is performed at that time. When the container 8 is loaded on the container 2-1, the digital weighing signal Wx obtained from the weighing instrument 2-1 (this is obtained from the A / D converter 18-1 a plurality of times at the container weight measurement time t2. The obtained digital weighing signal is obtained by performing a filtering process or the like) is a value obtained by combining the weight of the container 8 and the zero point weight value Wz (Wzi described above in the initial state). Therefore, the weight Wn of the container 8 can be obtained by subtracting Wz from Wx.

  Therefore, it is possible to determine whether or not the weighing device 2-1 is unloaded using Wn obtained at the container weight measurement time t2. For example, since the weight of the container 8 is known in advance, the no-load determination reference value Wt and Wn that are smaller than the weight are compared with each other, and if Wn is smaller than the no-load determination reference value Wt, It is determined that there is no container 8 on 4-1 and there is no load. When Wn is equal to or greater than the no-load determination reference value, it is determined that the container 8 is loaded on the platform 4-1. In this way, no-load determination means is realized.

  If it is determined that the weighing device 2-1 is unloaded, it can be determined that the container 8 has not been loaded from the loading position A. Therefore, the digital weighing is performed every time a predetermined sampling time elapses from time t2 to t7. The signal is stored in the RAM 26, and a new zero weight signal, for example, a zero weight value Wz is determined based on these digital weighing signals. For example, an average value of these digital weighing signals is set as a new zero point weight value Wz. Since the period from the time t2 to the time t7 is sufficiently longer than the period of the time t7 in which each of the measuring devices 2-1 to 2-n is always unloaded, the average value of each digital weighing signal obtained in these periods In this case, even if vibrations with a long period are included, the influence of these vibrations can be eliminated, and a stable and accurate zero weight value Wz can be determined. Note that these vibration components can also be removed by digital filtering, rather than simply averaging.

  FIG. 4 is a flowchart showing detailed steps when the CPU 22 performs the above-described processing (automatic zero adjustment processing). This processing is executed every time one of the measuring instruments reaches the section d2. . First, it is determined which measuring instrument is the measuring instrument located in the section d2 (step S2). Assume that this measuring instrument is a measuring instrument 2-1. Next, based on the digital weighing signal from the A / D converter corresponding to the weighing instrument, the above-described Wx in the weighing instrument is acquired (step S4). Thereafter, Wn in this measuring instrument is subtracted from Wx to calculate Wn (step S6). It is determined whether Wn is smaller than Wt (step S8). If the answer to the determination is no, the container 8 is loaded on the measuring instrument, and other processing is performed. If the answer to this determination is yes, since the container 8 is not loaded on the measuring instrument, the digital measuring signal Wx is acquired (step S10), and it is determined whether this measuring instrument has reached the end point of the section d7. (Step S12). If the answer to this determination is no, steps S10 and S12 are repeated until the answer to the determination is yes. If the answer to the determination in step S12 is yes, a new Wz for this measuring instrument is determined using the values of Wx acquired so far (step S14).

  Thus, even when the measuring devices 2-1 to 2-n are rotating, when the measuring device 2-1 rotates from the loading position A toward the unloading position B with no load, a new one is generated during that time. A zero point weight value Wz is acquired, and zero point adjustment is performed. During production, it is much more likely that the scales 2-1 to 2-n are unloaded on separate occasions than the total scales 2-1 to 2-n are unloaded. high. Therefore, every time there is such an opportunity, the influence of drift can be eliminated by acquiring a new zero point weight value Wz and adjusting the zero point for the weighing instrument that has become unloaded.

  In the above example, the zero weight value Wz is determined using the digital weighing signal between the section d2 and the section d7. However, the digital weighing signal in the section d1 is also stored in the RAM 26 in advance, When it is determined, a new zero-point weight value Wz can be determined using the digital weighing signal in the section d1 and the digital weighing signals obtained during the sections d2 to d7.

  In the production process, there may be a measuring instrument that does not easily become unloaded. Therefore, since each of the weighing devices 2-1 to 2-n is surely unloaded from the carry-out position B to the carry-in position A, the zero point weight value is obtained using the digital weighing signal obtained in the section d7 included in this section. It is possible to correct.

  However, since the section d7 is immediately after the filled container is carried out, the vibration signal component remains. Therefore, the zero weight value obtained during the section d2 to the section d7 is different from the zero weight value obtained only in the section d7. Further, the number of samples of the digital weighing signal obtained only in the section d7 is much smaller than the number of samples of the digital weighing signal obtained in the section d2 to the section d7. Therefore, there is a possibility that the influence of the noise signal due to the vibration of the rotating body that rotates each weighing device 2-1 to 2 -n cannot be sufficiently removed only by the digital weighing signal in the section d 7. Therefore, even if the zero-point weight value obtained in the sections d2 to d7 is replaced with the zero-point weight value obtained using the digital weighing signal only in the section d7, the zero-point accuracy is lowered.

  As a countermeasure, the digital weighing signal is passed when the measuring instrument passes through the section d7 (in this case, it passes in an unloaded state) on the condition that the container is filled before reaching the section d7. To obtain the unloaded section weight value Wy1, and when another weighing machine, for example, Wy1 is acquired, when the same measuring instrument passes the section d7, the digital weighing signal is obtained and the unloaded section is obtained. The weight value Wy2 is obtained, and the deviation between Wy1 and Wy2 is detected as the change amount of the zero point weight value, thereby correcting the zero point weight value Wz based on the digital weighing signal obtained between the section d2 and the section d7. . The above deviation represents the amount of change in the zero point weight value immediately after the object to be weighed is removed from the load detecting means when the same weighing instrument passes through the section d7 at different times. If drift occurs due to a factor other than this, the amount of change due to the drift is indicated. Therefore, even if the container 8 is continuously carried into the weighing instrument at the carrying-in position A, the influence of the zero point drift can be eliminated.

  FIG. 5 is a flowchart showing each step when the CPU 22 performs such processing (automatic zero correction). This processing is executed every time one of the measuring instruments reaches the section d7. First, it is determined which measuring instrument is the measuring instrument that has reached the section d7 (step S16). Then, it is determined whether the value of the counter C that is set to 0 in the initial state and corresponds to the determined measuring instrument is 0 or 1 (step S18). If the value of the counter C is 0, since the determined no-load section weight value Wy1 of the measuring instrument has not yet been acquired, the no-load section weight value Wy1 is acquired (step S20). Then, the value of the counter C is incremented by 1 (step S22), and this process ends.

  Next, when the same measuring instrument reaches the section d7 again, if it is determined in step S18 that Wy1 has been acquired first, the value of the counter C is 1 or 0 in step S18. Is judged. Since the value of the counter C is 1 this time, the no-load section weight value Wy2 of this measuring instrument is acquired (step S24), and the counter C is set to 0 (step S26).

  Then, a deviation Wd between Wy2 and Wy1 is calculated, and the current zero point weight value Wz is corrected with this deviation Wd (step S26). For example, Wd is added to or subtracted from Wz.

  In this way, even when the measuring instrument does not rotate in the no-load state from the section d2 to the section d7, the influence of the zero point drift can be eliminated.

  In the above example, since the time t7 passing through the no-load section d7 is short, there is a possibility that Wy1 and Wy2 have variations due to various noises. Therefore, an average value of M unloaded section weight values obtained while a certain measuring instrument passes through the unloaded section d7 a predetermined number of times, for example, M times is set to Wya1, and then the same measuring instrument is unloaded over M times. The average value of the M unloaded section weight values obtained while passing through the section d7 is defined as Wya2, and the deviation Wda is obtained. Since this deviation Wda represents the average drift amount, it may be used to correct the zero point weight value Wz of the measuring instrument.

  The zero point weight value Wz is corrected every time the measuring instrument rotates M times, with the average value obtained in the current M times as Wya2 and the average value obtained in the previous M times as Wya1. May be.

  Even if the zero point weight value is corrected using the deviation between the M average values in this way, the time t7 for the measuring instrument to pass through the no-load section d7 is short. In some cases, it cannot be attenuated. In this case, the zero point weight value Wz is not directly corrected by Wda, but the maximum correction amount is set to a predetermined value Wd. If the absolute value of Wda is larger than Wd, the zero point correction amount Wf is set to Wd. If the absolute value of Wda is equal to or less than Wd, Wda may be corrected as the zero point correction amount Wf, and the zero point weight value Wz may be corrected as the zero point correction amount Wf. For example, the calculation of Wz−Wf = Wx or Wz + Wf = Wz may be performed.

  As another method for reducing the correction amount in this way, Wf = r * Wda can also be considered by multiplying the value of Wda by a coefficient r smaller than 1. As the coefficient r, for example, 1σ of the obtained Wda is regarded as a drift component, and r = 0.65 can be set.

  In the above example, Wda is obtained based on the average values Way1 and Way2 obtained by dividing M times into a total of two times, and the zero point weight value Wz is corrected by Wda or a zero point correction amount Wf obtained by correcting Wda. However, for the third time, for example, M unloaded section weight values are determined to determine the unloaded section weight Way3, Wf1 or Wda is added to Wya1, and the reduced reduced unloaded section weight Wya2 ′ is determined. The calculation of Wya2 ′ may be performed to obtain the deviation amount Wda ′, and the zero point weight value Wz may be corrected by the deviation amount Wda ′.

  In either case, the zero point weight value Wz is not corrected by the total amount of deviation calculated, but the correction amount is reduced, so that overcompensation can be avoided as much as possible.

  In addition, when the case where the container 8 is not carried into the measuring instrument in the middle of calculating the unloaded section weight value over M times, the zero point correction is stopped and, as described above, between the section d2 and the section d7. Zero adjustment is performed using the latest zero weight value based on the digital weighing signal.

  As described above, according to this embodiment, even during production on the production line, a no-load state in a long section from the d2 section to the d7 section that occurs in any of the measuring devices 2-1 to 2-n. A stable zero-point weight value is obtained based on a plurality of digital weighing signals of the measuring instrument obtained in Step 1, the zero is automatically adjusted, and in preparation for the emergence of a measuring instrument that does not become unloaded for a long period of time. Since the zero point drift correction is performed so as not to be overcompensated based on the digital weighing signal in the section d7, an accurate and stable zero point weight value can always be obtained.

  In the above embodiment, the case where the zero point adjustment is performed as described above has been described. However, after the zero point is determined in advance as described above before starting the production, the zero point is not adjusted and then the zero point is adjusted as described above. It is also possible to perform only correction. In this case, the zero point drift can be corrected.

  In the above embodiment, the present invention is implemented in a weight-type filling device that carries a container and fills the container with the article. However, the present invention is not limited to this, while carrying the article from the loading position and rotating it. The present invention can also be implemented in a rotary weight sorter that measures the weight and sorts articles based on the weight.

  In this case, as shown in FIG. 6, while the article passes through the section D1 starting from the carry-in position A, the vibration generated in the weighing signal of the load cell is converged when the article is carried in at the carry-in position A. While the article passes through the section D2 following the section D1, the weight of the article is measured. In the subsequent section D3 (section starting from the unloading position B), the vibration generated in the weighing signal of the load cell converges when the article is unloaded from the unloading position B. A subsequent section D4 is a no-load section in which the load cell weighing signal is substantially stabilized and no load is applied. A time T1 corresponding to D1 is a transient response convergence time, a time corresponding to D2 is an article measurement time, a time T3 corresponding to D3 is a transient response convergence time, and a time T4 corresponding to D4 is a no-load time. The zero adjustment described above is performed based on each digital weighing signal while the weighing instrument passes through the sections D2, D3, and D4. Of course, if stored in advance, the digital weighing signal in the section D1 can also be used for zero adjustment.

  In the above embodiment, the weighing value Wn in the section d2 is compared with the no-load determination reference value Wt in order to determine whether or not the weighing instrument is unloaded. However, the present invention is not limited to this. Alternatively, for example, a sensor may be provided at the carry-in position A, and it may be determined whether there is no load depending on whether the sensor detects the container.

2-1 to 2-n weighing device 4-1 to 4-n platform 6-1 to 6-n load cell (load detection means)
22 CPU (zero adjustment means, zero correction means)

Claims (2)

A plurality of load detection means are provided so as to be rotatable around the center of rotation, and on the rotation trajectory drawn by the rotation of each load detection means in a predetermined direction, a carry-in position for sequentially carrying articles into the respective load detection means And a rotary weighing device provided with an unloading position for sequentially unloading the article from each load detecting means with an interval in the predetermined direction,
No-load state determination means for determining whether or not each load detection means is unloaded;
Zero-point adjusting means for performing zero-point adjustment on the load detecting means determined to be unloaded by the no-load state determining means during rotation,
Equipped,
The zero-point adjusting means is configured such that the no-load load detecting means is operated while the no-load load detecting means, which is the load detecting means determined as no load by the no-load state determining means, rotates from the loading position to the unloading position. At least part of the generated output signal is a zero weight signal,
When the load detection means rotates a plurality of times without load from the carry-out position to the carry-in position, the corresponding zero point weight is based on the deviation of the output of the load detection means obtained from the load detection means at different times. Having zero point weight signal correction means for correcting the signal;
The zero-point weight signal correcting means is a rotary weighing device that corrects the zero-point weight signal by reducing the deviation. A plurality of load detection means are provided so as to be rotatable around the center of rotation, and on the rotation trajectory drawn by the rotation of each load detection means in a predetermined direction, a carry-in position for sequentially carrying articles into the respective load detection means And a rotary weighing device provided with an unloading position for sequentially unloading the article from each load detecting means with an interval in the predetermined direction,
When the load detecting means rotates a plurality of times without load from the carry-out position to the carry-in position, a corresponding zero-point weight signal is obtained based on the deviation of the output of the load detection means obtained from the load detection means at different times. Provide zero point weight signal correction means to correct,
The zero-point weight signal correction means is a rotary weighing device that corrects the zero-point weight signal by reducing the deviation amount.

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