JPH0550690B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a combination weighing device that improves weighing accuracy and speed.

(Prior Art) Conventionally, when performing so-called quantitative weighing, in which a fixed amount of objects to be weighed whose unit weights vary slightly has been measured, combination weighing has been performed. Therefore, as shown in Figure 6, multiple input signal analog/digital (hereinafter referred to as A/
Using a conversion circuit (referred to as D), a large number of weighing data D ₁ to _Do are obtained from load cells placed in each of a number of weighing machines (not shown), and this weighing data D ₁ to _Do is input to a multiplexer and sequentially taken out. The data is passed through a sample hold circuit, converted into a digital value by an A/D converter, and then input to a calculation device consisting of a microcomputer (not shown), etc., and the combination closest to the target measurement value is determined by digital calculation. is being carried out.

Furthermore, since the combination weighing device is based on static weighing, each weighing machine is required to be in a static and stable state at the timing of reading the weighing data of each weighing machine. Therefore, in the past, a timer was set for the estimated time that the weighing machine would reach a stable state, and the timer was started as soon as the loading of the object to be weighed was completed, and the weighing data of each weighing machine was read using the timer's timeout signal. That's what I was doing.

(Problems with the Prior Art) In such a multi-input signal A/D conversion circuit, each measurement data is sequentially output in time series from a multiplexer, and each measurement data is sampled and held by one sample-hold circuit. /D converter, there is an inconvenience that the capacitor cannot be charged to improve sampling accuracy unless the sampling time is lengthened to a certain extent, and the sampling time (approximately several tens of microseconds)
The A/D converter will not operate during this period. For this reason, there was a problem in that an A/D converter capable of high-speed processing could not be effectively utilized.

In addition, in order to maintain weighing accuracy, the timer setting time described above must be set with safety in mind, so even if it actually becomes stationary and stable earlier, the set time may elapse. Until now, it was not possible to read the weighing data. Therefore, the conventional weighing speed is limited by the time set by the timer, and it is difficult to increase the weighing speed without reducing the weighing accuracy. On the other hand, conventionally, when reading weighing data, the static stability of each weighing machine is not checked, so even if the static stability is disturbed by disturbances such as floor vibration when reading weighing data, Reading could not be prohibited.

(Object of the Invention) The present invention solves the problems of the conventional technology, effectively utilizes an A/D converter capable of high-speed processing, A/D converts multiple input signals, and improves the performance of the conventional technology. This is a new combination weighing device that can improve both weighing accuracy and weighing speed, and also does not cause weighing errors even if the static stability is disturbed by floor vibration etc. when reading weighing data. It is intended for the purpose of providing.

(Summary of the Invention) The combination weighing device of the present invention improves weighing accuracy and speed by having the following structural requirements. A multiplexer into which the output data of multiple weighing machines is input, two sample-and-hold circuits that receive output signals from the multiplexer and repeat sampling and holding; A changeover switch that holds the circuit, an analog-to-digital converter that digitizes and outputs the signals output from the two sample-and-hold circuits, a means for constantly reading the output data from the analog-to-digital converter, and the read output data. A storage means for storing a predetermined number of items for each weighing machine, and each time the output data of each weighing machine is updated, the average value of the latest output data of a predetermined number of pieces is calculated, and the previous average value and the current average value are calculated. a detection means that detects whether each weighing machine is stable when the comparison value is within a predetermined range; and a calculation means that reads weighing data of the weighing machines in a static and stable state from the storage means and performs a combination calculation. .

(Example) An example of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic block diagram of one embodiment of the present invention. In the figure, a signal detected by a weight detector consisting of a load cell a of each weighing machine passes through an amplifier b and a filter c, and is input to a multiplexer d as weighing data D ₁ to _{D o} . The output signal of the multiplexer d is input to sample and hold circuits f ₁ and f ₂ through a zero-point coarse adjustment subtractor e ₁ and a zero-point fine adjustment subtractor e ₂ . When adjusting the zero point of the weighing machine, data and a chip selection signal are generated from the weight monitor microcomputer k based on the command from the combination calculation microcomputer m, which is the main computer, to adjust the zero point. D/A converter i ₁ for coarse adjustment and D/A converter for fine adjustment
Adjustment signals are output from i and ₂ , respectively. This adjustment signal is input to subtracters e ₁ and e ₂ through level shift g and level shift h, and a zero point signal with the output when no load is almost zero is output from the CD terminal of fine adjustment subtractor e ₂ . can get. This zero point signal is inputted to an A/D converter j through a sample and hold circuit, converted into a digital signal, and the weight is inputted to a weight monitoring microcomputer k.

Also, when adjusting the span of a measuring instrument, the signal obtained from the span adjustment D/A converter _i3 is
Input to subtractor _e3 , and from the E-F terminal of subtractor _e3 ,
The obtained reference voltage is input to the A/D converter j and the weight of the output relative to the input of the A/D converter is changed to adjust the span of the scale.

Now, changeover switches S _{1 and} S ₂ are provided on the output sides of the sample and hold circuits f ₁ and f ₂ , and one of the sample and hold circuits f 1 and f ₂ switches the sample of the other during sampling. Two sample and hold circuits f ₁ and f ₂ are made to operate differently at the same time so that the hold circuit is held. The output signal of the sample and hold circuit is the A/D
It is converted into a digital value by a converter j and inputted to a weight monitoring microcomputer k.

Next, the operation of the sample and hold circuit will be explained. Based on the commands from the combination calculation microcomputer m, which is the main computer, the weight monitor microcomputer k sends a multiplexer d, sample and hold circuits f ₁ , f ₂ , changeover switches S ₁ , S ₂ , and A/D converter j. Switching signals SC ₁ , SC ₂ and starting signal SC ₃ which are synchronized with each other are outputted. Then, multiple input signals are output from multiplexer d.
D ₁ to D _o are sequentially selected and input to the sample and hold circuit. The switching signal SC ₂ given to the sample and hold circuits f ₁ and f ₂ is input to one of the sample and hold circuits (f ₂ in the example) through the inverter L.
While the measurement data is held in either f ₁ or f ₂ , the subsequent input signal is sampled in the other sample hold circuit f ₂ or f ₁ . Furthermore, when the A/D conversion is completed, holding of the subsequent input signal starts, and the A/D conversion is started by the activation signal SC ₃ inputted to the A/D converter j.
At the same time, sampling of the next input signal starts.
By repeating such operations, the A/D conversion operation continues seamlessly at high speed, and digital calculations are performed. Further, the same method is used when sampling a plurality of pieces of weighing data from one weighing machine and then switching the multiplexer to sample the weighing data from the next weighing machine.

The output signal of the A/D converter j is input to the weight monitoring microcomputer k, which constantly grasps the weighing status (operating status) of each weighing machine. Reading means k ₁ for reading the output data of the weighing machine at room temperature
and detection means _k2 for detecting the static stability of each weighing machine.

Each time the output data of each weighing machine is updated, the detection means k ₂ calculates the average value of a predetermined number of latest output data up to a certain period of time, and calculates the average value of the previous time (before updating the memory). The stationary stability of each weighing machine is detected by comparing the obtained average value of a predetermined number of output data with the current average value.

The storage means RAMl stores the latest output data of each weighing machine, a predetermined number of output data (for example, 2 or 4, etc.) stored through multiple samplings up to a certain time before the latest output data, and the predetermined number of output data. The average value of the output data (weighing data) is stored for each weighing machine. This storage means 1 is normally under the control of the weight monitoring computer k, but the combinational calculation computer m, which is the main computer, is configured to be able to freely read the contents of the storage means 1 as necessary. By adopting such a multiprocessor system, the weight monitor computer k
m can accurately grasp the weighing status (operating status) of each weighing machine at all times, and can also be used as a computer for combination calculations. The weighing data of each weighing machine with improved performance can be used immediately. In addition, this storage means 1 stores various flags (under flag, over flag, minus flag, empty flag) that indicate the static stability of each weighing machine, and a stability flag that indicates complete static stability of each weighing machine. It is being memorized every time.

The combination calculation computer m functions as a main computer and controls the entire device. Therefore, when a start command is output from a packaging machine (not shown), the weighing data of the weighing machine with the stability flag set is read out from the storage means l.
These are combined to find the optimal combination that is equal to or closest to the target weight. Therefore, even if some of the weighing machines are unstable, if the other weighing machines are stationary and stable, a combination calculation is performed using the weighing data of these weighing machines.

The remote control box n is equipped with an input key, a display device printer, a zero point adjustment/span adjustment switch, etc., and a computer m for combinational calculations.
performs input operations, displays predetermined items, prints, etc.

FIG. 2 is a flowchart showing an example of the basic operating procedure of the weight monitoring computer k, in which steps P ₁ , P ₂ , and P ₄ correspond to the reading means k ₁ , and step P ₃ corresponds to the detection means Compatible with _k2 .

First, in step _P1 , a switching signal _SC1 specifying a specific weighing machine is output to the multiplexer, and in step _P2 , the data of the specific weighing machine (designated weighing machine) converted into a digital value is read. Next, in step _P3 , a detection process is executed, and when it is completed, the switching signal _SC1 is switched to the next one in step _P4 . Then, the process returns to step _P1 again and outputs the switched switching signal _SC1 to the multiplexer. The above process is repeated to sequentially read the output data of each weighing machine.

FIG. 3 is a flowchart showing the operating procedure of the weight monitor microcomputer. next,
This flowchart will be explained.

(1) After the initial settings (step _A1 ), the weight monitor computer k sends a request signal to the combination calculation computer m, which is the main computer.
Send RQ (Step _A2 ). When the combination calculation computer m receives the request signal RQ, it sends a bus request signal BUSRQ to the weight monitoring computer k.

When the weight monitor computer k receives the BUSRQ signal, it sends the bus acknowledge signal BUSAK.
is made active to notify computer m for fabrication calculations that the bus has been opened. When the combination calculation computer m confirms the BUSAK signal, it directly writes the necessary data into the memory l of the weight monitor computer k. When the BUSRQ signal becomes inactive, the weight monitor computer k moves to the next step and checks reception of the initial signal (step
_A3 ). Note that the BUSRQ signal is processed as an interrupt with the highest priority. Therefore, when this signal is received, the operation is temporarily stopped, but when this signal becomes inactive, the original operation is resumed.

(2) When initial data is received, check for a command requesting reading of A/D converter data in the data (step _A4 ), and if there is a command, move to data reading process of the weighing machine. (Step _A5 ). The processing at step _A5 will be described later. If this command is not present, check whether a manual (step A ₆ ) or automatic (step A ₇ ) zero adjustment command has been issued, and if either method of zero adjustment is specified, zero adjustment is performed. Move to processing (step
_A8 ).

Also, if there is no zero point adjustment command, check whether there is a span adjustment command (step
_A9 ). If there is such a command, the process moves to span adjustment processing (step _A10 ).

(3) If there are no commands listed above, check whether there is a mode change command (step _A11 ), and if a mode change is necessary, reset the mode change command (step _A12 ). In this case, to change the mode, the combination calculation computer sends a BUSRQ signal to the weight monitor computer k, confirms the BUSAK signal from the computer, and then writes a mode change command directly to the memory of the weight monitor computer. So, BUSRQ
Make the signal inactive. When the weight monitor computer confirms this mode change command in step _A11 , the process returns to step _A2 . FIG. 4 is a flowchart illustrating the process of step _A5 in FIG. 3 (input of weighing machine data). Next, this flowchart will be explained.

(1) Reset the reading command of the A/D converter (step B ₁ ), then set the input port number of multiplexer d, that is, the weighing machine number n into which weight data is input, to 1 (step B ₃ , _B4 ). This designates the first weighing machine.

(2) Data ZD _o for determining the zero point of computer number n is preset in the zero point adjustment D/A converter (step _B5 ). In addition, data SD _o that determines the span of the weighing machine number n is stored in the span adjustment D/A converter.
(Step _B6 ).

(3) Output a set signal to the sample and hold circuit (step B ₇ ), and send a start signal to A/D converter j (step B ₈ ). Next, the first output of A/D converter j is read (step B ₉ ), and the first output D _sun is stored (step B ₁₀ ). Subsequently, a reset signal is output to the sample and hold circuit (step B ₁₂ ), and a start signal is sent to the A/D converter (step B ₁₂ ). That is, step
As in the process _B11 , a set signal and a reset signal are alternately input to the sample and hold circuit.

(4) In the present invention, for one weighing machine,
By successively reading the data a predetermined number of times and finding the average value, one measurement value of the weighing machine is obtained, but in this embodiment, data is read two or four times. Therefore, in step _B13 , it is checked whether the output has been read twice, and if so, the process moves to steps _B22 and below, and if the output has not been read twice, it is determined that the output has been read four times. Read the second output of the A/D converter (step _B14 ).

(5) Update D _sun to the value obtained by adding the second output (step B ₁₅ ), set the signal for the sample and hold circuit (step B ₁₆ ), and send a start signal to the A/D converter (step B ₁₇ ). ), read the third output of the A/D converter (step B ₁₈ ), and update D _sun to the value adding the third output (step B18).
_B19 ) and move on to the next process.

(6) Output a reset signal to the sample and hold circuit (step B ₂₀ ), start the A/D converter (step B ₂₁ ), and read the fourth output of the A/D converter (step B ₂₂ ). . That is, when calculating the average value by reading the output twice, the first output and the fourth output of the weighing machine are used. Next, D _sun is updated to the value obtained by adding the fourth output (step B ₂₃ ), and the average value D _AVE is calculated (step B ₂₄ ). This average value is the average value of two output readings, so if the output reading is four times (step B ₂₅ ), the average value D _AVE of four times is further calculated (step B ₂₆ ).

(7) Previous average value data of weighing machine number n D _AVE・
Set n to _PAVE (step _B27 ). Further, the deviation value is set to D _DEV (step B ₂₈ ). Next, calculate the absolute value and deviation value D _DEV of the difference between the previous average value data P _AVE and the current average value data D _AVE for weighing machine number n.
(Step _{B 29} ), and if the condition _of |P _AVE - _{D AVE |}

Claims (1)

[Claims] 1. A multiplexer into which output data from a plurality of weighing machines is input, two sample-and-hold circuits that receive output signals from the multiplexer and repeat sampling and holding, and one sample-and-hold circuit that performs sampling and holding. Inside, there is a changeover switch that holds the other sample and hold circuit, an analog-to-digital converter that digitizes and outputs the signals output from the two sample-and-hold circuits, and a device that constantly reads the output data from the analog-to-digital converter. a storage means for storing a predetermined number of read output data for each weighing machine; and a storage means for storing a predetermined number of read output data for each weighing machine, and calculating an average value of a predetermined number of latest output data each time the output data of each weighing machine is updated. detection means for detecting the static stability of each weighing machine when the comparison value between the average value of and the current average value is within a predetermined range, and reading out the weighing data of the weighing machines in a static and stable state from the storage means. 1. A combinational weighing device comprising: calculation means for performing combinational calculations. 2. The combination weighing device according to claim 1, wherein the storage means is configured to store a predetermined number of latest output data. 3. The weighing data of each weighing machine participating in the combination calculation is the average value of the latest output data of a predetermined number of weighing machines in a static and stable state.
A combination measuring device according to claim 1.