JP2001343278A - Weight measuring apparatus of combination weighting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce consumption power to load cells. SOLUTION: This weight measuring apparatus of a combination weighing apparatus supplies articles which are supplied sequentially, to a specific number of weighing hoppers 7 via a diffusion feeder 4, measures the weight of the articles 2 accommodated in the respective hoppers 7 with weighing machines 10, and combines the articles accommodated in the hoppers, on the basis of the respective measured values. The weight measuring apparatus is equipped with load cells 14 built in the respective weighing machines, a multiplexer 18 which performs time division of measured signals of the load cells and leads out the signals, a load cell power supply circuit 15a for supplying power source to the load cells, plural switches interposed between the power source circuit 15 and the respective load cells, and a switch changing-over means 29 which closes the respective switches in a selection interval to measured signals of the respective load cells in the multiplexer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combination weighing machine for combining loose articles sequentially supplied from the outside according to a prescribed weight, and more particularly to a combination weighing machine which is incorporated in the combination weighing machine and stored in a weighing hopper. The present invention relates to a weight measuring device of a combination weighing machine for measuring weight.

[0002]

2. Description of the Related Art A packaging system that automatically packs various articles into bags by a specified weight is equipped with a combination weighing machine that sorts each of the loose articles sequentially supplied from the outside by a specified weight.

This combination weighing machine supplies sequentially supplied articles to a predetermined number of weighing hoppers via a dispersion feeder.
The weight of the articles stored in each of the weighing hoppers is measured by a weighing scale, and the total weight of the articles stored in a plurality of weighing hoppers arbitrarily combined among a predetermined number of weighing hoppers is a predetermined weight value. Has the function of collecting the articles stored in the plurality of weighing hoppers and discharging them so that they can be stored in one bag.

FIG. 11 is a schematic sectional view of the combination weighing machine. Above the inverted conical frame 1, a funnel 3 for gathering loose articles 2 such as confectionery and caramel supplied from the outside is provided. The articles 2 gathered by the funnel 3 are radially dispersed by the dispersion feeder 4 and, along a plurality of rectilinear feeders 5 radially arranged on the frame 1, along the outer peripheral surface of the inverted conical frame 1. Is supplied to a plurality of stock hoppers 6 arranged in the same manner.

After a plurality of articles 2 supplied to each stock hopper 6 are temporarily held by the stock hopper 6, the shutter 6a is opened and moved to the lower weighing hopper 7. The weights of the plurality of articles 2 moved to the weighing hopper 7 are collectively weighed by the weighing hopper 7. A plurality of articles 2 are weighed by a plurality of weighing hoppers 7 arranged along the outer peripheral surface of the inverted conical frame 1 respectively.

[0006] The respective weighing hoppers 7 storing the respective articles 2 whose total weight obtained by combining the respective weights of the respective articles 2 for each of the weighing hoppers 7 matches or approximates a predetermined specified weight are selected.
The shutter 7a is opened, and each article 2 is guided to the collecting chute 8. Therefore, the article 2 of a specified weight is stored in the bag placed below the collecting chute 8 and is automatically packed.

A plurality of motors 9a for controlling the opening and closing of shutters 6a attached to the lower end openings of the stock hoppers 6 and the shutters 7a attached to the lower end openings of the weighing hoppers 7 are provided in the inverted conical frame 1. A plurality of motors 9b for opening / closing control and a plurality of weighing meters 10 for measuring the weight of the articles 2 stored in the respective weighing hoppers 7 are provided.

FIG. 12 is a block diagram showing a schematic configuration of a weight measuring device incorporated in the combination weighing machine. For example, a weighing control unit 12 that reads each measurement value from a measurement signal a of a load cell 14 incorporated in each weighing scale 10 and shutters 6a and 7a of each hopper 6 and 7 are provided to a main control unit 11 including a computer. A shutter control unit 13 that drives and controls the motors 9a and 9b that open and close is connected.

In the balance controller 12, each load cell 14
Is supplied with a DC drive voltage Vcc from the load cell power supply circuit 15.
Is supplied. After the measurement signal a output from each load cell 14 is amplified by the amplifier 16, the noise component is removed by the LPF 17 and input to the multiplexer 18.

The multiplexer 18 sequentially selects the measurement signals a output from the load cells 14 in synchronization with the clock of the clock signal b output from the measurement value acquisition control unit 19, and sends the selected signals to the common amplifier 20. The measurement signal a output from each load cell 14 that has been time-division multiplexed is amplified by the common amplifier 20 and then input to one terminal of the adder 21. The other terminal of the adder 21 receives the digital bias value output from the measurement value acquisition control unit 19 as D / A.
It is applied in a state where it is converted to analog by the converter 22.
The bias value indicates a measured value in a state where the article 2 is not stored in the weighing hopper 7, and the adder 21 determines a state in which the article 2 is not stored in the weighing hopper 7 based on the value of the input measurement signal a. Is subtracted from the measured value, and corresponds to the weight value of the article 2 itself.

The time division multiplexing of each load cell 14 is measured.
Constant signal a₁Is converted to a digital measurement value D by the A / D converter 23.
It is converted and input to the measurement value acquisition control unit 19. Measurement
The value acquisition control unit 19 controls each weighing device 10 (low
Measured value D (D ₁, D_Two, D_Three, ...)
To the control unit 11.

The main controller 11 stores the weight value (measured value D (D ₁ , D ₂ , D ₃ ,...) Of each article 2 stored in each weighing hopper 7 obtained by one measurement (one cycle). ), The total weight value of the articles 2 stored in a plurality of weighing hoppers 7 arbitrarily combined among a predetermined number of weighing hoppers 7 such as eight, for example, falls within a predetermined allowable range of a prescribed weight value. When entering, a shutter opening command for opening the shutters of the plurality of weighing hoppers 7 is sent to the shutter control unit 13. As a result, the article 2 of a specified weight is stored in the bag placed below the collecting chute 8.

A temperature sensor 24 and a temperature detection circuit 25 are incorporated in the scale control unit 12. The temperature near the load cell 14 detected by the temperature sensor 24 is converted into a digital temperature by the temperature detection circuit 25 and sent to the main control unit 11. The main controller 11 stores the detection sensitivity of each load cell 14 and each amplifier 16 and each temperature characteristic synthesized with respect to the amplification factor (gain). Then, the main control unit 11 receives the respective measurement values D (D ₁ , D ₂ ,
D ₃ ,...) Are corrected using the respective temperature characteristics and used as official weight values for calculation of subsequent combinations of the articles 2.

[0014]

However, FIG.
However, the following problems still need to be solved in the weight measuring device of the combination weighing machine shown in FIG.

That is, as shown in FIG. 12, a direct-current drive voltage Vcc is constantly applied from the load cell power supply circuit 15 to each load cell 14. However, each load cell 1
4 is time-division multiplexed by the multiplexer 18, so that the DC driving voltage Vcc is applied to the load cell 14 even during the period when the multiplexer 18 does not select itself. Wasteful power consumption. As a result, the running cost (maintenance cost) of the entire combination weighing machine increases.

Further, the power capacity required by the load cell power supply circuit 15 also increases, and the manufacturing cost of the entire combination weighing machine increases.

In particular, in recent years, the size of the combination weighing machine has been increased, and the number of the stock hoppers 6 and the weighing hoppers 7 has been increasing. As described above, when the number of the weighing hoppers 7 is increased, the number of the weighing meters 10 is also increased, so that the running cost (maintenance and management cost) and the manufacturing cost of the entire combination weighing machine further increase.

The load cell 14 of the weighing scale 10 of each weighing hopper 7 disposed along the peripheral surface of the inverted conical frame 1 has a strain gauge generally attached to a metal member to which a load is applied. They are connected in a shape. Therefore, even if the load cell 1 has the same specifications,
4, the signal level of the measurement signal a with respect to the applied load is significantly different. Further, in the load cell 14 formed by connecting the strain gauges in a bridge shape, the signal level of the measurement signal a greatly changes individually when the ambient temperature changes. Furthermore, the amplification factors of the amplifiers 16 that amplify each measurement signal a and the temperature dependence of the amplification factors also differ depending on each amplifier 16.

Therefore, each temperature characteristic indicating the detection sensitivity of each load cell 14 and each amplifier 16 at each temperature and the amplification factor at each temperature is measured in advance, and the main control unit 1
A temperature characteristic of a state in which each load cell 14 and each amplifier 16 are combined is stored and held in 1.

Each load cell 14 and each amplifier 16
The reason for individually determining the temperature characteristics is that, for example, when each load cell 14 and each amplifier 16 fail alone, instead of replacing the load cell 14 and the amplifier 16 with a set, the failed load cell 14 or the amplifier 16 alone is used. This is because, in some cases, replacement is required, and it is necessary to individually obtain and combine them.

The procedure for measuring the temperature characteristics of each load cell 14 and each amplifier 16 is as follows. First, in a state where the articles 2 are not stored in the weighing hopper 7, the ambient temperature is measured.
The load cell 14 of one channel to be measured is removed from the scale controller 12, and the measured value Da of the corresponding channel in this state is read. Next, the load cell 14 is moved to the balance controller 12.
And the measured value Db of the corresponding channel in this state
Is read. Then, a value DL (= Da−Db) obtained by subtracting the measured value Db from the measured value Da is set as the calibration value of the load cell 14 alone of the corresponding channel at the corresponding temperature. Further, the measured value Da is set as a calibration value of the amplifier 16 alone of the corresponding channel at the corresponding temperature. Next, the same operation is repeated while changing the ambient temperature.

However, every time a calibration value for one temperature is obtained, the load cell 14 must be manually attached to and detached from the weighing controller 12, so that the calibration operation is complicated, and a great deal of time and time is required. It took effort.

The present invention has been made in view of such circumstances, and by inserting a switch in the power supply path of each load cell, it is possible to supply power to each load cell only when necessary, thereby reducing power consumption. It is an object of the present invention to provide a weight measuring device of a combination weighing machine that can be manufactured and that can reduce manufacturing costs.

Further, by interposing a switch in the power supply path of each load cell, the temperature characteristics of each load cell and each amplifier can be easily obtained individually, and the combination weighing can greatly improve the efficiency of the calibration work. An object of the present invention is to provide a device for measuring the weight of a machine.

[0025]

According to the present invention, articles sequentially supplied are supplied to a predetermined number of weighing hoppers via a dispersion feeder, and the weight of the articles stored in each weighing hopper is measured by a weighing scale. The present invention is applied to a weight measuring device of a combination weighing machine that combines articles stored in each weighing hopper based on each measured value.

In order to solve the above problems, a weight measuring device for a combination weighing machine according to the present invention includes a load cell incorporated in each weighing scale, a multiplexer for extracting a measurement signal of each load cell in a time-division manner, A load cell power supply circuit for supplying power to each load cell, a plurality of switches interposed between the load cell power supply circuit and each load cell, and switch switching for closing each switch during a selection period for a measurement signal of each load cell in the multiplexer. Means.

In the weight measuring device of the combination weighing machine configured as described above, the load cell of each channel is supplied with power during a period when its own measurement signal is selected by the multiplexer, and is not supplied with power during a non-selection period. . Therefore, power consumption can be suppressed. Also, since power is not supplied to a large number of load cells at the same time, the power capacity of the load cell power circuit can be reduced.

According to another aspect of the present invention, there is provided a weight measuring device for a combination weighing machine according to the present invention, further comprising a plurality of sample-hold circuits interposed between each load cell and a multiplexer; And a sample-and-hold circuit switching circuit that causes the load cell to sample during a selection period for a measurement signal of each load cell in the multiplexer and hold the sampling signal during a non-selection period for the measurement signal.

In the weight measuring device of the combination weighing machine configured as described above, each measurement signal output from the load cell of each channel is, during the non-selection period, the signal level of the measurement signal in the previous selection period. Is maintained, the measurement signal does not suddenly rise from the 0 level in the next selection period, so that the measurement signal is stabilized in a short time within the selection period.

According to another aspect of the present invention, in the weight measuring device for a combination weighing machine according to the present invention, a selection period for a measurement signal of each load cell for closing a switch is set at a constant period in the measurement signal of the load cell.

According to another aspect of the present invention, in the weight measuring device for a combination weighing machine according to the present invention, the selection period for the measurement signal of each load cell for closing the switch includes a selection period for the measurement signal of the corresponding load cell in the multiplexer.

According to another aspect of the present invention, in the weight measuring device for a combination weighing machine according to the present invention, a sampling period of the sample and hold circuit for the measurement signal of each load cell is included in a period in which a switch for the load cell is closed.

By setting each selection period and sampling period as in each of the above-mentioned inventions, the operation of each part in this weight measuring device can be made more reliable.

According to another aspect of the present invention, in the weight measuring device for a combination weighing machine according to the present invention, an amplifier is interposed between each load cell and each sample-and-hold circuit, and power supplied to each amplifier is used to open and close a switch. Regardless, it is always controlled to be ON.

According to still another aspect of the present invention, there is provided a weight measuring device for a combination weighing machine according to the above-mentioned invention, further comprising a plurality of amplifiers interposed between each load cell and a multiplexer, and a state in which articles are not stored in a weighing hopper. Reading the measured value of the measurement signal of the load cell selected by the multiplexer as the first measured value in a state where the switch corresponding to the designated load cell is forcibly opened according to the calibration command input specifying the load cell and the amplifier. A second reading means for reading a measurement value of a measurement signal of the load cell selected by the multiplexer as a second measurement value in a state in which the forced open of the switch corresponding to the designated load cell is released;
And the first measurement value read by the first measurement value reading means is subtracted from the second measurement value read by the second measurement value reading means, and a subtraction value is designated. Calibration value calculating means for setting the first measured value as the calibration value of the designated amplifier as well as the calibration value of the load cell.

In the weight measuring device of the combination weighing machine configured as described above, the measurement value of the measurement signal of the load cell selected by the multiplexer with the switch corresponding to the designated load cell being forcibly opened, that is, the first value,
Is a calibration value when no load is applied only to the amplifier to which the load cell is not connected.

On the other hand, the measurement value of the measurement signal of the load cell selected by the multiplexer in a state where the switch corresponding to the designated load cell is released from the forced open state, that is, the second measurement value is obtained by comparing the calibration value of the load cell with the amplifier value. Since the calibration value and the calibration value are the added calibration values, the calibration value of only the load cell is obtained by subtracting the first measurement value from the second measurement value.

[0038]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a combination weighing machine in which a weighing device according to an embodiment of the present invention is incorporated. FIG. 1A is a top view, and FIG. 1B is a schematic sectional view. The same parts as those of the conventional combination weighing machine shown in FIG. 11 are denoted by the same reference numerals, and detailed description of the overlapping parts will be omitted.

In the combination weighing machine of this embodiment,
Eight stock hoppers 6 and eight weighing hoppers 7 are arranged along the outer peripheral surface of the frame 1. Each of the articles 2 assembled by the funnel 3 is radially dispersed by the dispersion feeder 4, and is disposed along the outer peripheral surface of the frame 1 by a plurality of linear feeders 5 radially disposed on the frame 1. It is supplied to a plurality of stock hoppers 6.

The plurality of articles 2 supplied to each stock hopper 6 are temporarily held by the stock hopper 6, and then moved to the lower weighing hopper 7 by opening a shutter 6a having a lower end opening by a motor 9a. . The weights of the plurality of articles 2 moved to the weighing hopper 7 are collectively weighed by the weighing hopper 7 by the weighing device 10.

Each of the weighing hoppers 7 containing the articles 2 whose total weight, which is the combination of the weights of the respective articles 2 for each of the weighing hoppers 7, matches or approximates the specified weight, is selected, and the shutter 7 a having the lower end opening is driven by a motor. Opened at 9b, each article 2 is guided to the collecting chute 8. An article 2 of a specified weight is stored in a bag placed below the collecting chute 8 and is automatically packed.

FIG. 2 is a block diagram showing a schematic configuration of a weight measuring device incorporated in the combination weighing machine. The same parts as those of the weight measuring device of the conventional combination weighing machine shown in FIG. Therefore, the detailed description of the overlapping part will be omitted.

For example, a main controller 11a composed of a computer and a scale controller 12a for reading each measured value from the measurement signal a of the load cell 14 incorporated in each weighing scale 10.
And a shutter control unit 13 that drives and controls motors 9a and 9b that open and close the shutters 6a and 7a of the hoppers 6 and 7,
The display unit 26 and the printer 27 are connected.

In the scale controller 12a, CH1 to CH8
The load cell 14 of each channel is supplied with a DC drive voltage Vcc from the load cell power supply circuit 15a through a switch 28.
Is supplied. The switches 28 of the channels CH1 to CH8 are switched by the switch
8 is closed by closing time T ₁ of the provisions shown in Figure 4 including the selection period for measuring Shingo a load cell 14 for each channel. The operation of the switch switching circuit 29 is controlled by the measured value acquisition control unit 19a.

In each load cell 14, FIG.
As shown in (a) and (b), four resistors R ₁ , R ₂ , R ₃ , and R _{4 each} composed of a strain gauge attached to a metal member to which a load is applied are connected in a bridge shape. . A DC driving voltage Vcc is applied to both ends of the bridge from the load cell power supply circuit 15a via the switch 28. Between the ground and the bridge end of the switch 28, a ground resistor R ₅ of the high resistance is inserted. The potential difference at the midpoint of the bridge is input to the amplifier 16 as the measurement signal a. As shown, the amplifier 16 always has a DC drive voltage ± V
cc is supplied and the ON state is maintained.

FIG. 3A shows a state where the switch 28 is opened. In this state, since the drive voltage Vcc is not applied to both ends of the bridge, the signal level of the measurement signal a is 0 level. FIG. 3B shows a state where the switch 28 is closed. In this state, since the drive voltage Vcc is applied to both ends of the bridge, a measurement signal a having a signal level corresponding to a load or a temperature change is output.

The measurement signal a output from the load cell 14 of each channel is input to the sample-and-hold circuit 30 after being amplified by the amplifier 16. Sample-and-hold circuit 30 for each channel CH1~CH8, at the sample hold circuit switching circuit 31, multiplexer 18 hold time defined as shown in FIG. 4 in the non-selection period for the measurement signal a load cell 14 of each channel T ₂ only it works to hold the signal level of the measurement signal a at closing time T ₁ of the switch 28 contained in the hold time T _2. The operation of the sample and hold circuit switching circuit 31 is controlled by the measured value acquisition control section 19a.

The measurement signal a output from the load cell 14 of each channel via the sample hold circuit 30 is L
The noise component is removed by the PF 17 and the multiplexer 18
Is input to

The multiplexer 18 sequentially selects the measurement signals a output from the respective load cells 14 in synchronization with the clock of the clock signal b output from the measurement value acquisition controller 19a, and sends out the selected signals to the common amplifier 20. . The measurement signal a of each channel output from each time-division multiplexed load cell 14 is amplified by the common amplifier 20 and then added to the adder 21.
To one terminal.

To the other terminal of the adder 21, a digital bias value output from the measured value acquisition control section 19 a is applied in a state where the digital bias value is converted into an analog signal by the D / A converter 22. The bias value indicates a measured value in a state where the article 2 is not stored in the weighing hopper 7, and the adder 21 determines a state in which the article 2 is not stored in the weighing hopper 7 based on the value of the input measurement signal a. subtracting the measured value at the measuring signal a ₁ which corresponds to the weight value of the article 2 itself.

The time division multiplexed output from the adder 21
Measurement signal a of each load cell 14 ₁Is A / D converter 2
3. Converted into a digital measurement value D at 3 and the measurement value acquisition control unit
19a. The measurement value acquisition control unit 19a
Measurement value D of each weighing scale 10 (load cell 14)
(D₁, D_Two, D_Three, D_Four, D_Five, D₆, D₇, D₈) The main
Send it to the control unit 11a.

The measured value acquisition control unit 19a sends a clock signal to the multiplexer 18 to execute selection control of each channel of the multiplexer 18 and synchronizes each channel of the multiplexer 18 with the selection operation of each channel. The operation timing of the switch switching circuit 29 and the sample and hold circuit switching circuit 31 is controlled so that the switch 28 and the sample and hold circuit 30 of each channel operate.

[0053] The main control unit 11a, based on one (1 cycle T) measured in housed in each of the weighing hoppers 7 obtained weight value of each article 2 (measured value D (D ₁ ~D ₈₎₎ , When the total weight of the articles 2 stored in the plurality of weighing hoppers 7 arbitrarily combined among the eight weighing hoppers 7 falls within an allowable range of a predetermined specified weight value. To the shutter control unit 13 for opening the shutter 7a. As a result, the article 2 of a specified weight is stored in the bag placed below the collecting chute 8.

Further, a temperature sensor 24 and a temperature detection circuit 25 used for calibrating each load cell 14 and each amplifier 16 are incorporated in the scale control section 12a.

FIG. 4 is a time chart showing the operation of the weight measuring device shown in FIG. The weight measurement for the article 2 is performed as one cycle T (= 11 × T ₀ ) in 11 cycles (11 × T ₀ ) of the clock signal b having the cycle T ₀ . Then, the multiplexer 18 sequentially selects the measurement signals a of the channels CH1 to CH8 in synchronization with the clock signal b from the second clock to the ninth clock in the one cycle T period. The A / D converter 23 outputs C
Bias values for each channel of H1~CH8 outputs a measured value D ₁ to D ₈ of each channel from the measurement signal a ₁ after being subtracted CH1 to CH8.

The drive voltage Vcc for the load cell 14 of the channel 1 (CH1) rises at the first clock (time t ₀ ) in the first cycle T, and only for the closing time T _{1 which} is slightly longer than two clock cycles (T ₀ × 2). continue to be, it falls at time t _3.

As described above, each channel (CH1 to CH)
The load cell 14 of 8) rises at the start of the period T ₀ immediately before the clock period T ₀ at which the multiplexer 18 has selected its own channel, and falls after the end of its own clock period T ₀ .

Therefore, each channel (CH1 to CH
In the load cell 14 of 8), during one cycle T (= 11 × T ₀ ) during which one combination process is performed on the article 2, during most of the period when the multiplexer 18 does not select its own channel. Since the driving voltage Vcc is not supplied, the power consumption is greatly reduced.

The sample and hold circuit 30 of the channel 1 (CH1) rises at the third clock (time t ₂ ) of the first cycle T and has a hold time T _{1 which} is slightly longer than nine clock cycles (T ₀ × 9). continue to be, it falls at time t _4.

As described above, each channel (CH1 to CH
8) The sample and hold circuit 30 includes the multiplexer 1
8 rises after the end of the clock period T ₀ that has selected its own channel, and falls after the start of the period T ₀ immediately before the next own clock period T ₀ .

Therefore, each channel (CH1 to CH
8) Each measurement signal a output from the load cell 14 is
During the non-selection period by the multiplexer 18,
Since the signal level of the measurement signal a in the previous selection period (clock period T ₀ ) is maintained, the measurement signal a suddenly rises from the 0 level in the next selection period (clock period T ₀ ). Therefore, the measurement signal a stabilizes in a short time within the selection period (clock cycle T ₀ ). Therefore, by shortening the period T ₀ of the clock signal b, each weight of the article 2 stored in each weighing hopper 7 can be measured in a short time.

Next, each of the channels (CH1 to CH8) implemented by the main control unit 11a and the measured value acquisition control unit 19a.
The calibration processing operation for the load cell 14 and the amplifier 16 will be described with reference to the flowchart of FIG. This flow chart shows a case where the calibration command is input by designating the load cells 14 of all the channels CH1 to CH8 and the amplifiers 16 of all the channels.

First, the temperature C near each load cell 14 and each amplifier 16 is read via the temperature sensor 24 (S
1). Next, the operation of the switch switching circuit 29 is stopped. In this state, the switch 28 of each load cell 14 is open. Therefore, each load cell 14 is equivalently disconnected from each amplifier 16. Note that the sample-and-hold circuit switching circuit 31 maintains a normal operation (S2). In this state, which first measurement reads the measured value of each channel of CH1~CH8 in the first one cycle (T) th DA _1, DA _2, D
A ₃ , DA ₄ , DA ₅ , DA ₆ , DA ₇ , DA ₈ (S
3).

Next, the operation of the switch switching circuit 29 is returned to a normal state (S4). In this state, the switch 28 of each load cell 14 is closed in a state where the switch 28 is selected by the multiplexer 18. In this state, the measured values of the channels CH1 to CH8 in the next first cycle (T) are read and are read as the second measured values DB ₁ and D 2.
_{B 2, DB 3, DB 4} , DB 5, DB 6, DB 7, the DB ₈ (S5).

The second in each of the channels CH1 to CH8
Measured values DB ₁ , DB ₂ , DB ₃ , DB ₄ , DB ₅ , DB ₆ ,
First measured value DA in each channel from DB ₇ and DB _{8
1, DA 2, DA 3,} DA 4, DA 5, DA 6, DA 7, DA 8
And the calibration values DL ₁ , DL ₂ , DL ₃ , DL ₄ , DL ₅ , DL ₆ , D of each load cell 14 alone in each channel
L _7, and DL ₈ (S6).

The first measured values are set as the calibration values DA _{1 to} DA ₈ of each amplifier 16 alone, and the calibration values DA
₁ to DA ₈ and the load cell 14 alone calibration value DL ₁ through DL ₈
Is stored in the memory together with the measured temperature C (S
7).

[0067] If not calibration value DA ₁ to DA ₈ and the load cell 14 alone calibration value DL ₁ through DL ₈ of each amplifier 16 alone measurements for temperature C prescribed number (S8), the load cell 14 and the amplifier Temperature C near 16 (temperature condition)
The change (S9), the process returns to S1, and starts the calculation of the calibration value DA ₁ to DA ₈ and the load cell 14 alone calibration value DL ₁ through DL ₈ of each amplifier 16 alone at a temperature C was changed.

[0068] with respect to the temperature C of the predetermined number when the calibration value DA ₁ to DA ₈ and calibration value DL ₁ through DL ₈ of the load cell 14 alone of each amplifier 16 alone is measured (S8), each load cell 14 alone calibration value calculates the temperature characteristic shows the temperature dependence of the DL ₁ ~DL ₈ (S10). Similarly, to calculate the temperature characteristic showing a temperature dependence of the amplifier 16 alone calibration value DA ₁ ~DA ₈ (S11). Then, the calculated temperature characteristics are displayed on the display unit 26 and printed out by the printer 27 (S12).

FIG. 6 is a time chart showing the operation of the weighing device when the calibration command is input by designating the load cells 14 of all the channels CH1 to CH8 and the amplifiers 16 of all the channels.

As shown, the first cycle (T)
At first, the drive voltage Vcc is not supplied to each load cell 14, and the starting voltage Vcc is supplied to each load cell 14 in the next one cycle (T).

As described above, each load cell 14 is connected to the amplifier 1
6, the temperature characteristic is measured by each load cell 14 alone, and the temperature characteristic is measured by the amplifier 16 alone. Therefore, it is possible to easily create a temperature characteristic by combining the load cell 14 and the amplifier 16 of each channel.
Even when one of the load cell 14 and the amplifier 16 of each channel is replaced due to a failure or the like, the load cell 14 and the amplifier 16 whose temperature characteristics have already been measured.
, The synthesized temperature characteristic after replacement can be easily obtained. Therefore, the efficiency of the calibration work of the load cell 14 and the amplifier 16 incorporated in the weight measuring device of the combination weighing machine is greatly improved.

In the time chart of FIG. 4, when the ON period of the drive voltage Vcc for the load cell 14 and the sampling period of the sample-and-hold circuit 30 are verified, the following is obtained: [drive voltage ON → sampling ON → own channel CH selection → own channel If the sequence of “channel CH end → sampling OFF (hold ON) → drive voltage OFF” is maintained, the ON period of the drive voltage Vcc for the load cell 14 described above may be lengthened. That is, the rise timing of the driving voltage Vcc may be two or more previous period of its own clock period T _0.

Further, in the flowchart of FIG. 5 and the time chart of FIG. 6, the case where the calibration command is inputted by designating the load cells 14 of all the channels CH1 to CH8 and the amplifiers 16 of all the channels is shown. It is also possible to input a calibration command by designating the load cell 14 and the amplifier 16 of a specific channel (CH).

In this case, in the first cycle (T),
If the switch 28 of the load cell 14 of the designated channel is maintained in the open state and the switch 28 of the load cell 14 of the designated channel is returned to the normal state in the next one cycle (T), Each temperature characteristic of the load cell 14 and the amplifier 16 is obtained independently.

The present invention is not limited to the embodiment described above. In the embodiment device, the power supply circuit for each load cell 14 is configured as shown in FIG. However, the power supply circuit can be configured as shown in FIGS.

[0076] Power supply circuit for the load cell 14 shown in FIG. 7 is a circuit obtained by removing the ground resistance R ₅ of the high-resistance from the power supply circuit shown in FIG. Load cell 1 shown in FIG.
In the power supply circuit for the battery 4, one battery 3
2 supplies the drive voltage Vcc to the load cell 14 via the switch 28. In this case, there is no ground resistance for removing the residual charge of the bridge when the power is shut off (OFF) by opening the switch 28.

In the power supply circuit for the load cell 14 shown in FIG. 9, a driving voltage is supplied from the two batteries 32 to both ends of the bridge of the load cell 14 via the respective switches 28a and 28b. In this case, when the switches 28a and 28b are opened,
Both ends of the bridge in the load cell 14 are grounded simultaneously. Therefore, the residual charge of the bridge when the power is turned off (OFF) is instantaneously eliminated.

The power supply circuit for the load cell 14 shown in FIG. 10 is similar to the power supply circuit of FIG.
Individual switches 28a from the batteries 32,
A drive voltage is supplied to both ends of the bridge of the load cell 14 via the respective terminals 28b. In this case, when the switches 28a and 28b are opened, one end (upper end) of the bridge in the load cell 14 is grounded, but the other end (lower end) of the bridge is opened.

[0079]

As described above, in the weight measuring device of the combination weighing machine according to the present invention, the switch is inserted into the power supply path of each load cell, and the power is supplied to each load cell only when the own channel is designated by the multiplexer. Has been supplied. Therefore, power consumption and manufacturing cost can be reduced.

Further, a switch is interposed in the power supply path of each load cell, and each measured value in a state where the switch is opened and a state where the switch is closed is obtained. Therefore, the temperature characteristics of each load cell and each amplifier can be easily obtained, and the work efficiency of the calibration work can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a combination weighing machine in which a weight measuring device according to an embodiment of the present invention is incorporated.

FIG. 2 is a circuit block diagram of a weight measuring device of the combination weighing machine.

FIG. 3 is a diagram showing a power supply circuit for a load cell incorporated in the weighing device.

FIG. 4 is a time chart showing a normal operation of the weighing device.

FIG. 5 is a flowchart showing a calibration operation in the weighing device.

FIG. 6 is a time chart showing a calibration operation in the weighing device.

FIG. 7 is a diagram showing another power supply circuit for a load cell incorporated in the weighing device.

FIG. 8 is a diagram showing another power supply circuit for a load cell incorporated in the same weighing device.

FIG. 9 is a diagram showing another power supply circuit for the load cell similarly incorporated in the weighing device.

FIG. 10 is a diagram showing another power supply circuit for the load cell incorporated in the same weighing device.

FIG. 11 is a diagram showing a schematic configuration of a general combination weighing machine.

FIG. 12 is a circuit block diagram of a weight measuring device incorporated in the general combination weighing machine.

[Explanation of symbols]

 2 ... Articles 4 ... Dispersion feeder 5 ... Linear feeder 6 ... Stock hopper 6a, 7a ... Shutter 7 ... Weighing hopper 8 ... Collecting chute 9a, 9b ... Motor 10 ... Weighing scale 11a ... Main control unit 12a ... Weighing control unit 13 ... Shutter Control unit 14 Load cell 15a Load cell power supply circuit 16 Amplifier 18 Multiplexer 19a Measured value acquisition control unit 24 Temperature sensor 28 Switch 29 Switch switching circuit 30 Sample hold circuit 31 Sample hold circuit switching circuit

Claims (7)

[Claims] An article (2) sequentially supplied is supplied to a predetermined number of weighing hoppers (7) via a dispersion feeder (4),
Weigh the weight of the articles stored in each weighing hopper (10)
In the weight measuring device of the combination weighing machine that combines the articles stored in each of the weighing hoppers based on the measured values measured in the weighing hopper, a load cell (14) incorporated in the weighing scale; A multiplexer (18) for extracting a measurement signal of the load cell in a time-division manner; a load cell power supply circuit (15a) for supplying power to each of the load cells; A weight measuring device for a combination weighing machine, comprising: a switch (28); and switch switching means (29) for closing each switch during a selection period for a measurement signal of each load cell in the multiplexer. 2. A plurality of sample-and-hold circuits (3) interposed between each of said load cells and said multiplexer.
0), and a sample and hold circuit switching circuit (31) for sampling each sample and hold circuit during a selection period for a measurement signal of each load cell in the multiplexer and holding the sample and hold circuit during a non-selection period for the measurement signal. A weight measuring device for the combination weighing machine according to the above. 3. The weight measurement of the combination weighing machine according to claim 1, wherein the selection period for the measurement signal of each load cell for closing the switch is set at a constant period in the measurement signal of the load cell. apparatus. 4. The weight measurement of the combination weighing machine according to claim 1, wherein the selection period for the measurement signal of each load cell for closing the switch includes a selection period for the measurement signal of the load cell in the multiplexer. apparatus. 5. The weight measuring device for a combination weighing machine according to claim 2, wherein the sampling period of the sample and hold circuit for the measurement signal of each load cell is included in a period for closing a switch for the corresponding load cell. 6. An amplifier (16) is interposed between each of the load cells and each of the sample and hold circuits, and a power supply to each of the amplifiers is controlled to be always in an ON state irrespective of opening and closing operations of the switches. The weight measuring device for a combination weighing machine according to claim 2, characterized in that: 7. A plurality of amplifiers (16) interposed between each of the load cells and the multiplexer, and a calibration command input specifying the load cell and the amplifier in a state where no articles are stored in the weighing hopper. First measurement value reading means (S3) for reading a measurement value of a measurement signal of the load cell selected by the multiplexer as a first measurement value while forcibly opening a switch corresponding to the designated load cell; Second measurement value reading means (S5) for reading the measurement value of the measurement signal of the load cell selected by the multiplexer as a second measurement value in a state in which the forcible opening of the switch corresponding to the designated load cell is released; Subtract the first measurement value read by the first measurement value reading means from the second measurement value read by the second measurement value reading means. 2. The combination weighing machine according to claim 1, further comprising a calibration value calculating means (S6) for setting a value as the calibration value of the specified load cell and for setting the first measured value as a calibration value of the specified amplifier. Weight measuring device.