JP2011095216A - Weighing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a weighing device capable of heightening furthermore weighing speed, while satisfying prescribed weighing accuracy. <P>SOLUTION: A stability discrimination reference setting means 11 of this weighing device sets a stability discrimination reference specified by an allowable value of a dispersion width of a plurality of sampling weight signals in a dispersion width evaluation time domain before an appearing time of the sampling weight signal capable of acquiring prescribed weighing accuracy from a weight signal output means 5. When the dispersion width of the plurality of sampling weight signals in a stability discrimination time domain before an output time of the newest sampling weight signal from the weight signal output means 5 becomes below the allowable value of the dispersion width shown in the stability discrimination reference, and the sampling weight signal in the stability discrimination time domain is discriminated to be stable by a stability discrimination means 12, a weight measured value acquisition means 13 acquires a weight measured value from the sampling weight signal at the latest time in the stability discrimination time domain. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a weighing device that automatically obtains a weight measurement value from a weight signal at the time when the stability of the weight signal is determined.

  Conventionally, as a method for determining the acquisition timing of a weight measurement value from a weight signal, for example, there are a stability waiting time method and a stability determination method.

  The stable waiting time method is preferably applied to (1) a weighing device having a uniform supply mode to the weighing platform, and (2) a supply hopper disposed above the weighing hopper. Examples thereof include an automatic or semi-automatic combination weigher having a structure.

  In the weighing device of (1) above, a timer for counting a stable waiting time and a timing at which the object to be weighed is placed on the weighing table immediately before being placed on the weighing table is used as the starting point of the timer count. Timer start point detecting means for detecting, and when the timer start point detecting means detects the start point of the timer count, the timer for counting the stable waiting time counts the elapsed time from the starting point, and a predetermined stable waiting time has elapsed. The weight measurement value is automatically acquired from the weight signal at the timing.

  As a specific prior art relating to the weighing device (1), there is one proposed in Patent Document 1, for example. In the weighing device according to this Patent Document 1, the time point when the article sensor detects the article is used as the starting point of the timer count, the sample article is weighed a plurality of times (m times) in the adjustment mode, and a plurality of times (m The variation of the weight measurement value is obtained from the weight measurement value of the first time, and the time when the obtained variation first enters the range of the predetermined value is used as the acquisition timing of the weight measurement value during operation (so-called stable waiting time).

  On the other hand, in the combination weigher (2), since the object to be weighed is once stored in the supply hopper and then supplied to the weighing hopper, the operation of dropping the object to be weighed supplied from the supply hopper to the weighing hopper is performed. It is almost uniform every time. Therefore, it is predicted that the time from the timing when the gate of the supply hopper is opened to the timing when the weight signal is stabilized is almost uniform every time, and therefore a constant timer for counting the stable waiting time is applied.

However, when the above-described stable waiting time method is applied to a weighing device having a structure in which an operator directly supplies an object to be measured to a weighing table or a weighing hopper, for example, a manual combination weigher, the following Problems arise.
That is, in the manual combination weigher, since the worker plays a role of supplying the objects to be weighed to the weighing platform or the weighing hopper, the manner of supplying the objects to be weighed to the weighing table or the weighing hopper is not uniform. For this reason, it takes a long time for the weight signal to stabilize when the supply mode is such that the impact load becomes large, and when the supply mode is such that the impact load does not become too large, the time until the weight signal becomes stable is compared. Short. In this way, the response status of the weight signal varies greatly each time depending on how the object is placed, so if the weight measurement value is acquired from the weight signal at the end of the stabilization wait time, the correct weight measurement value is obtained. I can't.

  Therefore, in the case of a weighing device that employs a supply method in which the difference in time from when the object to be weighed is supplied to the weighing platform or weighing hopper until the weight signal stabilizes depends on the supply mode of the object to be weighed, A stability determination method that determines stability and obtains a weight measurement value is applied.

  As a specific prior art relating to a weighing device to which the stability determination method is applied, there is one proposed in Patent Document 2, for example. In the weighing device according to this Patent Document 2, with respect to time-series weight signal data a1, a2, a3, a4,..., First the average value A1 of the data a1, a2, a3, and then the data a2, a3, a4. The average value A2 and then the average value A3 of the data a3, a4, a5 are obtained as average values at several points in time series data, and the difference between these average values (A1-A2), (A2-A3), It is determined that the weight signal has reached a stable state when... Becomes less than the allowable variation width C1, and the weight measurement value is obtained at this timing. In other words, a stability determination time region for evaluating the vibration state of the weight signal at a fixed time interval is provided, and the time point at which the weight signal in the stability determination time region reaches within an allowable value is detected, and weight measurement is performed using the weight signal at this detection time point. The value is determined.

JP-A-6-43011 JP-A-9-113348

  In the weighing device according to Patent Document 2, the stability determination time region is a time region in which the weight signals at two successive times already satisfy the predetermined measurement accuracy, and the rearmost among the stability determination time regions. The weight measurement value is determined with the weight signal at the time. That is, in FIG. 4 (a), when the difference between the weight signals A1 and A2 at time t2 and time t3 and the difference between A2 and A3 are continuously within the variation width allowable value C1, it is determined to be stable. Time t3 is set as the time for obtaining the weight measurement value.

  By the way, in the weighing device according to Patent Document 2, actually, even when the weight signal that satisfies the predetermined weighing accuracy is already obtained with the weight signal A2 at time t2, the predetermined variation width allowable value C1 is obtained. Since the basis for determining the stability is not defined in the variation width allowable value C1, the weight measurement value is further acquired with the weight signal A3 at time t3, and the weight signals A2 and A3 are within the variation width allowable value C1. We define stability as the basis for discriminating that it is stable with continuity. For this reason, there is a problem in that the weight measurement value acquisition timing is delayed by a difference (t3−t2) between the time t2 and the time t3.

  Further, in the weighing device according to Patent Document 2, if the number of data used for stability determination is too small, in other words, if the time length of the stability determination time region is too short, the weight measurement value is stable to the variation width allowable value C1. Since there is no basis for discriminating that there is a difference, in other words, it is not defined that the difference (variation) in the sampling weight signal is within the variation width allowable value C1, and therefore, as shown in FIG. In addition, in the response of the weight signal during the supply of the object to be weighed, there is a possibility that the stability signal is erroneously determined even when the weight signal is not stable. Accordingly, the vibration amplitude stability determination time region is usually formed with a longer time region weight signal. For this reason, the weight signal included in a long time interval is required for stability determination even after the weight signal actually enters a stable vibration state (after the time when accurate weight measurement values can be obtained). There is a problem that the measurement value acquisition timing is delayed.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a weighing device that can increase the measurement speed while reliably satisfying a predetermined measurement accuracy.

In order to achieve the object, the weighing device according to the present invention comprises:
Weight signal output means for outputting a sampling weight signal at a predetermined time interval in accordance with a load on the weighing platform of the object to be weighed;
A time at which a sampling weight signal capable of obtaining a predetermined weighing accuracy appears from the weight signal output means is obtained, a predetermined time region before that time is defined as a variation width evaluation time region, and a plurality of times in the variation width evaluation time region are determined. A stability criterion setting means for setting a stability criterion defined by an allowable value of the variation width of the sampling weight signal;
Before the time when the latest sampling weight signal is output from the weight signal output means, a stability determination time region having the same time length as the variation width evaluation time region is defined, and a plurality of sampling weight signals in the stability determination time region are determined. A stability determination means for determining that the sampling weight signal in the stability determination time region is stable when the variation width is equal to or less than a tolerance of the variation width indicated in the stability determination criterion;
A weight measurement value acquisition means for acquiring a weight measurement value from the sampling weight signal at the final time of the stability determination time area when the stability determination means determines that the sampling weight signal in the stability determination time area is stable; It is characterized by providing (1st invention).

  In the present invention, the stability determination criterion setting means obtains an error of the sampling weight signal with respect to the true weight measurement value of the object to be measured, and a standard deviation of the variation of the error is an allowable error with respect to the true weight measurement value of the object to be weighed. The following time is detected, and this time can be set as the final time of the variation width evaluation time region (second invention).

  In the present invention, the stability determination criterion setting means obtains a variation width of a plurality of sampling weight signals generated at different times in the variation width evaluation time region, and determines the tolerance of the variation width based on a statistical value of the variation width. The value can be determined (third invention).

In the present invention, the stability determination defined by the tolerance of the variation widths of the plurality of sampling weight signals in the variation width evaluation time region before the time when the sampling weight signal capable of obtaining a predetermined weighing accuracy from the weight signal output means appears. The reference is set in advance in the adjustment mode, for example. In operation, the variation width of the plurality of sampling weight signals in the stability determination time region before the time when the latest sampling weight signal is output from the weight signal output means is less than the tolerance of the variation width indicated in the stability determination criterion. When it is, it is determined that the sampling weight signal in the stability determination time region is stable, and the weight measurement value is acquired from the sampling weight signal at the final time of the stability determination time region. That is, an evaluation criterion for stability determination is defined as an allowable value of the variation width.
According to the present invention, since the weight measurement value is acquired from the sampling weight signal at the final time in the first stability determination time region that satisfies the stability determination criterion of the variation width defined to satisfy the predetermined measurement accuracy, It is possible to increase the measurement speed while reliably satisfying the predetermined measurement accuracy.

1 is a schematic system configuration diagram of a weighing device according to an embodiment of the present invention. The graph showing the state of the response waveform of the weight signal in the weighing device of this embodiment Explanatory drawing of the range of variation in weight signal in the weighing device of the present embodiment Graph explaining the problems of the prior art

  Next, specific embodiments of the weighing device according to the present invention will be described with reference to the drawings. The following description is an example in which the present invention is applied to a manual combination scale as a weighing device.

<Description of schematic configuration of weighing device>
The weighing device 1 according to the present embodiment is a so-called manual combination weigher, and includes a plurality (k pieces) of weighing devices 2 ₁ to 2 _k and a calculation means 3 as shown in FIG.

<Description of schematic configuration of measuring instrument>
Each of the weighing devices 2 _{1 to} 2 _k includes a weighing table 4 on which an operator can directly place the object to be weighed M by hand, and a weight signal output means 5 provided corresponding to the weighing table 4. Yes.

<Description of weight signal output means>
The weight signal output means 5 includes a load sensor 6, an A / D converter 7, and a filter 8.
The load sensor 6 outputs an analog load signal [a ′] corresponding to the load on the weighing table 4 of the object M placed on the weighing table 4.
The A / D converter 7 converts the analog load signal [a ′] from the load sensor 6 into a digital load signal [a].
The filter 8 subtracts a weight signal corresponding to the tare weight of the weighing platform 4 or the like from the digital load signal [a] from the A / D converter 7 and obtains a weight signal [b] of the object M at every predetermined time interval Δt. Output.

<Explanation of calculation means>
The calculation means 3 is mainly composed of a microcomputer, executes a combination calculation based on the weight signal [b] from each weight signal output means 5, and the combined total value is closest to the target value within a certain allowable range. Has a function of selecting a combination. Also, it has a timer function that starts from a time t0 described later and counts the elapsed time from this starting point.
Further, in the calculation means 3, a predetermined program relating to weight measurement value acquisition stored in the memory is executed by the microprocessor, whereby the stability determination reference setting means 11, the stability determination means 12 and the weight measurement value acquisition means 13. Each function is realized.

<Description of Stability Discrimination Criteria Setting Method by Stability Discrimination Criteria Setting Unit>
The stability determination criterion setting unit 11 sets the stability determination criterion based on predetermined statistical weighing accuracy in the adjustment mode. Hereinafter, a method for setting the stability determination criterion by the stability determination criterion setting means 11 will be described in detail.

<Explanation of time response of weight signal>
FIG. 2 shows a response waveform of the weight signal when the operator places the object to be weighed M on the weighing platform 4 by a normal supply operation.
When the impact load is large, the response waveform is as shown by the w1 line. When the impact load is small, the response waveform is as shown by the w3 line. In the case of an intermediate impact load, the response waveform is as shown by the w2 line. The response waveform is as shown.

<Description of starting point setting>
To determine the stability criterion for the weight signal, the time response of the weight signal must be examined. In the adjustment mode, an identification weight value Wr for recognizing that the object M is placed on the weighing table 4 is determined. The identification weight value Wr is set to an appropriate weight value between the zero point and the weight value of the workpiece M.
The time when the weight signal becomes Wr or more is set as t0, and the elapsed time is counted starting from this t0. The starting point t0 may be a local maximum immediately after the weight signal becomes larger than Wr.

<Explanation of weight signal sampling time>
t10 is a time just before the weight signal is predicted to be stable, t1n is a time at which the weight signal is predicted to be sufficiently stable, and a time interval Δt between t10 and t1n according to the output timing of the filter 8. T1n, t11, t12,.
Further, a time t1s at which an accurate weight measurement value of the object to be weighed M, that is, a static weight measurement value can be acquired, is provided further behind t1n. If the weight value of the object M is known, t1s is not set as the sampling time of the weight signal, and the known weight value may be set instead of the weight measurement value obtainable at time t1s.

<Description of creation of weight signal table data in adjustment mode>
A sample article is placed on each weighing table 4 as an object to be weighed M and is lowered. This loading / unloading operation is performed m times.
In each of the m weighing operations performed by each of the weighing devices 2 _{1 to} 2 _k , the calculation means 3 sets t0 as the time when the weight signal becomes larger than Wr for the first time, and counts the elapsed time starting from this time t0. Then, the weight signals at the respective times of t10, t11,..., T1n, t1s are stored as sampling weight signals, and table data as shown in Table 1 is created. Here, in Table 1, for example for measuring instrument _{2 1,} the first sampling weight signal of the weighing times obtained at time t10 is represented as W1011, sampling weight signal of the weighing times first obtained at the time t1s is w1s11 It is expressed. Similarly, for meter 2 _k, the m-th sampling weight signal of the weighing times obtained at time t1n is expressed as W1nmk, weighing times the m-th sampling weight signal obtained at the time t1s is expressed as w1smk ing.

<Table data of sampling weight signal>

<Description of creation of sampling weight signal error table data in adjustment mode>
After the sampling weight signal relating to m times of weighing is obtained for each of the weighing devices 2 _{1 to} 2 _k , when the stability determination criterion setting key 14 is pressed, the calculation means 3 stores the time from t10 to t1n. The absolute value of the sampling weight signal error obtained by subtracting the sampling weight signal stored at time t1s from the sampling weight signal is obtained to create table data as shown in Table 2. Here, in Table 2, for example, the meter _{2 1,} by weight signal error e1011 time t10 is determined by the following equation.
e1011 = | w1011-w1s11 |
Similarly, for the weighing instrument 2 _k , the weight signal error e1 nmk of the m-th weighing number obtained at time t1n is obtained by the following equation.
e1nmk = | w1nmk−w1smk |

<Weight measurement error table data>

<Explanation of standard deviation of variation in sampling weight signal error>
Next, from the (m · k) sampling weight signal error data of the weighing devices 2 ₁ to 2 _k at each time t10 to t1n, standard deviation values of variations in sampling weight signal error: σ10, σ11,. σ1q,... σ1n (g) is calculated.
The condition of an allowable error with respect to a true value in weight measurement is defined in advance as “u sigma condition is ± E (g) or less (usually, the value of u is set to 2 to 3)”. , Σ1n,..., Σ1n are checked for magnitude relation with E / u in order from time t10 toward time t1n, and for the first time σ1q ≦ (E / u) The time t1q corresponding to the standard deviation σ1q that satisfies the above is found.

<Explanation of variation width evaluation time area setting>
When the time t1q at which a weight signal with a predetermined weighing accuracy can be obtained is found, the variation width evaluation time for evaluating the variation width of the sampling weight signal from the timing of this time t1q to a time t1r before the predetermined time length T0. An area is set (see Table 3).
Since the variation of the sampling weight signal is due to the amplitude of the natural vibration signal meter 2 ₁ to 2 _k caused by the objects to be weighed (sample article) is supplied to the meter 2 ₁ to 2 _k, the A time region T0 that is slightly longer than one cycle of the natural vibration signal is set so that the degree of convergence of the amplitude of the natural vibration signal can be evaluated and determined.

<Table data of standard deviation value of sampling weight signal error variation>

<Description of tolerance of variation width>
If the variation width between the sampling weight signals at each time is small in the variation width evaluation time region (time t1r to time t1q) determined by the time t1q and the predetermined time length T0, the variation in the sampling weight signal at the time t1q is small. If the variation width between the sampling weight signals at each time in the variation width evaluation time region is large, the variation width of the sampling weight signal at time t1q is also large.
Therefore, the variation width of the sampling weight signal between time t1q and the previous variation width evaluation time region (time t1r to time t1q) including time t1q, which is the time at which the weight measurement value can be acquired with a predetermined probability with high probability. Is statistically obtained by using a large number of weight signal variations, and the statistically obtained value is set as an allowable value as a criterion for stability determination.

<Explanation of definition of stability criterion>
That is, the stability criterion can be defined as follows.
The stability criterion is a weight signal at a time before the time at which a weight measurement value satisfying a predetermined weighing accuracy can be obtained satisfies a weight measurement value with a predetermined weighing accuracy at a time determined by the stability criterion. It is a reference value for determining whether or not the convergence of the vibration amplitude is shown. Here, as the reference value, an allowable value for the variation width of the plurality of sampling weight signals in the variation width evaluation time region is used.

<Explanation of stability criteria setting>
In the table data shown in Table 1, the maximum variation width R11 of the time domain of the time t1r~ time t1q at the first weighing of meter 2 ₁ (variation width evaluation time domain). That is, the maximum value and the minimum value among the plurality of sampling weight signals in the variation width evaluation time region (time t1r to time t1q) are obtained, the difference between the maximum value and the minimum value is calculated, and the calculation result is maximized. The width is R11.
Similarly, it is possible to calculate the 2~m th maximum variation width R21~Rm1 measuring instruments _{2 1.}
Similar operations and calculation of the maximum variation range about the meter 2 ₁ performs for the other measuring instruments 2 ₂ to 2 _k.
In this way, data of the maximum variation widths R11 to Rmk in the variation width evaluation time region (time t1r to time t1q) related to ₁ to m measurements of all the measuring devices 2 ₁ to 2 _k can be obtained.

<Explanation of stability criteria setting>
If the average value Ra and the standard deviation Rs of the maximum variation widths of the plurality of sampling weight signals in the variation width evaluation time region are obtained based on the data of the maximum variation widths R11 to Rmk obtained as described above, the variation width is obtained. The size of the variation width of the plurality of sampling weight signals in the evaluation time region exists in the range of Ra ± u · Rs with the probability of u sigma.
Then, the stability determination criterion setting unit 11 sets the range of the variation width represented by Ra ± u · Rs as the tolerance value Re of the variation widths of the plurality of weight signals in the variation width evaluation time region (Re = Ra ± u · Rs), and an allowable value Re of the variation width is set as a reference value of the stability determination criterion.

  Up to now, the method for setting the stability determination criterion by the stability determination criterion setting means 11 in the adjustment mode has been described. In the following, the stability determination method of the weight signal by the stability determination unit 12 and the method of acquiring the weight measurement value by the weight measurement value acquisition unit 13 during operation are described in order.

<Description of stability determination method of weight signal by means of stability determination>
During the operation operation, the stability determination means 12 has a stability determination time of the same time length T0 as the variation width evaluation time area before the time (t1 <q>) when the latest weight signal is output from the weight signal output means 5. A region (time t1 <q-4> to time t1 <q>) is defined, and the variation width Rx of the plurality of weight signals in the stability determination time region is equal to or less than the tolerance value Re of the variation width indicated in the stability determination criterion. When the weight signal in the stability determination time region is determined to be stable.

<Description of Weight Measurement Value Acquisition Method by Weight Measurement Value Acquisition Unit>
The weight measurement value acquisition unit 13 determines that the stability determination unit 12 determines that the weight signal in the stability determination time region (time t1 <q-4> to time t1 <q>) is stable. Assuming that the final time (t1 <q>) corresponds to the final time t1q of the variation width evaluation time region (time t1r to time t1q) in the adjustment mode, the final time (t1 <q>) of the stability determination time region. Obtain a weight measurement from the weight signal.

<Description of the operational effects of the weighing device of the present embodiment>
In the weighing device 1 of the present embodiment, a plurality of samplings in the variation width evaluation time region (t1r to t1q) before the time (t1q) at which a sampling weight signal capable of obtaining a predetermined weighing accuracy can be obtained from the weight signal output means 5. A stability criterion defined by the tolerance value Re of the variation width of the weight signal is set. Then, a plurality of sampling weights in the stability determination time region (time t1 <q-4> to time t1 <q>) before the time (t1 <q>) at which the latest sampling weight signal is output from the weight signal output means 5. When the variation width Rx of the signal is equal to or less than the tolerance value Re of the variation width indicated in the stability determination criterion, it is determined that the sampling weight signal in the stability determination time region is stable, and the last time (time) of the stability determination time region A weight measurement is obtained from the weight signal at t1 <q>).
According to the weighing device 1 of the present embodiment, the weight measurement value is obtained from the sampling weight signal at the final time in the first stability determination time region that satisfies the stability determination criterion of the variation width defined so as to satisfy the predetermined measurement accuracy. Since it is acquired, the measurement speed can be further increased while reliably satisfying the predetermined measurement accuracy.

  Next, a more specific embodiment of the weight value acquisition method by the weighing device 1 will be described.

<Example 1 of weight value acquisition method>
When the sampling weight signal output from the filter 8 is greater than or equal to Wr during operation, the stability determination unit 12 determines that the sampling weight signal greater than or equal to Wr is W <p>, W < p + 1>, W <p + 2>, W <p + 3>, W <p + 4>... each time it is continuously output, a plurality of sampling weight signals in the stability determination time region are grouped into one group. Determines the stability of the sampling weight signal.

  For example, when the stability determination means 12 sets the time length T0 of the stability determination time region to a time length for which five sampling weight signals (T0 = 4 · Δt) are output, the object to be weighed M is placed on the weighing platform. For each of the latest 5 sampling weight signal groups, the maximum and minimum values of the sampling weight signal in the group are obtained as time elapses after loading on 4, and the variation width and variation width are as shown in Table 4 below. Is compared with the allowable value Re.

  As the group number of the sampling weight signal group increases, the vibration amplitude of the weight signal also converges, and as shown in Table 4, the (y-1) th sampling weight signal group reaches the sampling weight signal group and a plurality of sampling weight signal groups. When the variation width Ry becomes equal to or less than the variation width allowable value Re, the stability determination unit 12 determines that the plurality of sampling weight signals in the (y−1) th sampling weight signal group are stable.

  The weight measurement value acquisition unit 13 determines that the stability determination unit 12 determines that the plurality of sampling weight signals in the (y-1) th sampling weight signal group are stable, and determines the final time (t1) of the stability determination time region. The sampling weight signal W <p + y + 4> in <q>) is a sampling weight signal satisfying a predetermined weighing accuracy, and the weight measurement value of the current weighing is acquired from the sampling weight signal W <p + y + 4>.

<Example 2 of weight value acquisition method>
When the time t1q = t1 <q> at which the sampling weight signal that satisfies the predetermined weighing accuracy appears in the adjustment mode described above, the time length T0 of the stability determination time region is 4 as in the first embodiment. If it is set to Δt, the standard deviation value of the variation in absolute value of time error from time t1 <q> to T0 (= 4 · Δt) time before is time t1 <q-4>, For t1 <q-3>, t1 <q-2>, t1 <q-1>, t1 <q> = t1q, σ1 <q-4>, σ1 <q-3>, σ1 <q−, respectively. 2>, [sigma] 1 <q-1>, [sigma] 1 <q> = [sigma] 1q, these values are used for the amplitude evaluation of the vibration signal as the standard deviation value in the order of the output number of the sampling weight signal.

That is, in correspondence with the output numbers [1] to [5], the output number [1] → σ1 = σ1 <q-4>, the output number [2] → σ2 = σ1 <q-3>, the output number. [3] → σ3 = σ1 <q-2>, output number [4] → σ4 = σ1 <q-1>, output number [5] → σ5 = σ1 <q>.
Table data in which the output number is associated with the standard deviation value is stored in the memory of the calculation means 3.
When many weighings are performed, a value obtained by doubling u times the standard deviation at these times indicates the variation range of the weight signal (see FIG. 3). For example, when u = 3, 97.7% of the weight signal belongs to the hatched range in FIG. 3 at the time preceding the time t1q when the predetermined accuracy is 3 sigma.

  During the operation, the latest five sampling weight signals continuously output from the filter 8 are examined. If these sampling weight signals fall within the hatched area in FIG. 3, the sampling weight signals are stable and predetermined. A weight measurement is obtained from the most recent sampling weight signal.

  Whether or not the latest five sampling weight signals belong to the hatched area in FIG. 3 is verified as follows.

Assume that the latest five sampling weight signals at a certain time point are W <p>,..., W <p + 4> in the order of output time. These five sampling weight signals are always given output numbers [1] to [5] in the order of output.
When one sampling weight signal is newly output, the latest sampling weight signal becomes output number [5], the oldest output sampling weight signal of output number [1] is discarded, and the previous output number [ 2] Updated to the sampling weight signal which was the second.

In the stability determination time region, the maximum value and the minimum value of the sampling weight signal and the numbers x and y of the respective output orders are detected, and the variation width R (= maximum value−minimum value) of the sampling weight signal group is obtained.
A table in which the standard deviation σx of the output number [x] to which the maximum value of the sampling weight signal belongs and the standard deviation σy of the output number [y] to which the minimum value of the sampling weight signal belongs are associated with the output number and the value of the standard deviation. It is extracted from the data, and the tolerance value Rxy of the variation width is set to 2 · u (σx + σy), and the size of the variation width R of the sampling weight signal group and the tolerance value Rxy of the variation width are compared. When the value is less than or equal to the value Rxy, the stability determination unit 12 determines that the plurality of sampling weight signals in the sampling weight signal group are stable. When the stability determining means 12 determines that the plurality of sampling weight signals in the sampling weight signal group are stable, the weight measurement value acquiring means 13 is the latest weight signal of this sampling weight signal group W <p + 4>. To obtain the weight measurement value of this measurement.

  The weighing device of the present invention has been described above based on one embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and the configuration is appropriately changed without departing from the spirit of the present invention. It is something that can be done.

  Since the weighing device of the present invention has a characteristic that the weighing speed can be further increased while satisfying a predetermined weighing accuracy, it is suitably used for a manual, automatic or semi-automatic combination weigher. In addition, it can be used for applications such as weighing conveyors.

1 Weighing device 2 ₁ to 2 _k meter 3 operation means 4 weighbridge 5 weight signal output means 6 the load sensor 7 A / D converter 8 filter 11 stability determination reference setting means 12 the stability determination means 13 weight measuring value acquisition means

Claims (3)

Weight signal output means for outputting a sampling weight signal at a predetermined time interval in accordance with a load on the weighing platform of the object to be weighed;
A time at which a sampling weight signal capable of obtaining a predetermined weighing accuracy appears from the weight signal output means is obtained, a predetermined time region before that time is defined as a variation width evaluation time region, and a plurality of times in the variation width evaluation time region are determined. A stability criterion setting means for setting a stability criterion defined by an allowable value of the variation width of the sampling weight signal;
Before the time when the latest sampling weight signal is output from the weight signal output means, a stability determination time region having the same time length as the variation width evaluation time region is defined, and a plurality of sampling weight signals in the stability determination time region are determined. A stability determination means for determining that the sampling weight signal in the stability determination time region is stable when the variation width is equal to or less than a tolerance of the variation width indicated in the stability determination criterion;
A weight measurement value acquisition means for acquiring a weight measurement value from the sampling weight signal at the final time of the stability determination time area when the stability determination means determines that the sampling weight signal in the stability determination time area is stable; A weighing device comprising:   The stability determination criterion setting means obtains an error of the sampling weight signal with respect to the true weight measurement value of the object to be weighed, and a time at which the standard deviation of the variation of the error is less than an allowable error with respect to the true weight measurement value of the object to be weighed. The weighing apparatus according to claim 1, wherein the time is set as a final time of the variation width evaluation time region.   The stability determination criterion setting unit obtains variation widths of a plurality of sampling weight signals generated at different times in the variation width evaluation time region, and determines an allowable value of the variation width based on a statistical value of the variation width. Item 3. The weighing device according to item 1 or 2.

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