JPH05133794A - Weighing device and calibration method for it - Google Patents

Abstract

PURPOSE:To make span calibration with weights as heavy as one fraction, whose denominator consists of an integer, of the max. scale while the resolution at the max. load is secured substantially. CONSTITUTION:At the time of span calibration, a reference weight as heavy as 1/N (N is a positive integer) of the max. load which is measurable is placed on a weighing tray, and the weight data as digital data from an analog-digital converter 4 is accommodated one by one in a memory 7. When N pieces of data accommodated in this memory 7 are one by one moved and added by a calculator circuit 8, weight measuring data is acquired which is equal to the resolution given at the max. load. Span adjustment can be done with the same accuracy as when the reference load at the max. load is used by means of adjusting the coefficient of a coefficient circuit 6 on the basis of the data acquired, and labor in placing and removal of weights can be reduced in span adjusting works for a large-sized weighing device which requires a particularly large reference load.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a span calibration technique in a weighing device for converting an analog signal from a weight detecting means into a digital signal.

[0002]

2. Description of the Related Art For span adjustment, a weight having a known weight is mounted on a weighing pan, and a coefficient is multiplied so that the measured value at this time is equal to the weight of the weight. In such a case, it is necessary to use the weight of the maximum load (weighing value) that can be weighed in order to ensure the calibration accuracy. However, in the weighing device that measures the weight in tons, the weight of the weight is also large. Therefore, a great deal of labor is required for the work of mounting and removing the weight on the weighing pan. In order to solve such a problem, there has been proposed a method in which a span is adjusted by using a weight having a weight which is about a half of a measured value of a measuring device (Japanese Patent Laid-Open No. Sho-06-1999).
60-236035).

[0003]

However, in a digital type weighing device which converts an analog signal from the weight detector of the load cell into a digital signal by the analog-digital conversion means, the resolution in the same measurement range,
In other words, since the number of bits per unit weight is the same, for example, the resolution at half the maximum load is 1/2 the resolution at the maximum load, so if span adjustment is performed with a weight that is half the maximum load. However, since the calibration is performed in a state where the resolution is substantially low, there is a disadvantage that sufficient accuracy cannot be secured. The present invention has been made in view of such a problem, and its object is to ensure the same accuracy as the calibration at the maximum load by using a weight having a weight smaller than that of the maximum load that can be measured. The present invention is to provide a new weighing device that can do this. Another object of the present invention is to propose a span calibration method using the above weighing device.

[0004]

In order to solve such a problem, in the present invention, load detection means for converting the weight of the object to be measured into an analog electric signal and outputting the analog electric signal, and the analog electric signal are digital signals. A weighing device comprising analog-to-digital conversion means for converting into digital data and coefficient means for multiplying the digital signal by a predetermined coefficient to convert into weight data, wherein the data from the analog-to-digital conversion means is changed with time. Storage means for storing a plurality of means, means for moving and adding the data in the storage means, operation means for multiplying the number of data added to the load, and dividing the multiplied value by the moving addition value to obtain the coefficient of the coefficient means. I was prepared.

[0005]

The standard load W of 1 / N of the maximum load that can be measured during span calibration is mounted on the weighing pan, and the weight data at this time is sequentially stored in the storage means. When N pieces of data (Wn, Wn-1, ..., W1) stored in the storage means are sequentially moved and added, the weight measurement data (Ws = Wn + Wn-1 +) equivalent to the resolution expressed by the maximum load W × N is obtained. ... + W1) can be obtained. By dividing the maximum load W × N by this data Ws and adjusting the coefficient of the coefficient means based on the result of the division, span adjustment can be performed with the same accuracy as when using the reference weight of maximum load. In particular, it is possible to reduce the labor for mounting and removing the weight in the span adjustment work of a large-scale weighing device that requires a particularly large reference weight.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will now be described based on the illustrated embodiments. FIG. 1 shows an embodiment of the present invention, in which reference numeral 1 is a load cell for outputting an analog electric signal proportional to the applied load, and a weighing pan 2 is provided at its detection end. It is configured as a load detection device. Reference numeral 3 is a preamplifier that amplifies the analog electric signal output from the load cell 1 to a predetermined magnification, and 4 is an analog-to-digital converter that converts the analog electric signal output from the preamplifier 3 into a digital signal. .. The digital signal output from the analog-digital converter 4 is output to the coefficient circuit 6 via the changeover switch 5, where it is multiplied by a predetermined coefficient and displayed on the display 11 as a weight.

At the other contact of the change-over switch 5, a memory 7 for storing the weight data output from the analog-digital converter 4 in synchronization with the sampling period, and an arithmetic circuit for moving and adding N pieces of the data in the memory 7 are added. 42 is connected, and the output of the arithmetic circuit 42 is output to the display 11 via the OR circuit 10. Data from the weighing value setting circuit 9 storing the maximum load (weighing value) is input to the arithmetic circuit 8.

Next, the operation of the thus constructed apparatus will be described. When the object to be weighed is mounted on the weighing pan 2 in this embodiment, a weight signal composed of an analog voltage signal proportional to this is output from the load cell 1. The weight signal is converted into a digital signal by the analog-digital converter 4, multiplied by a predetermined coefficient by the coefficient circuit 6, and displayed on the display 11 as the weight. When the span adjustment becomes necessary, the switch 5 is switched to the memory 7 side, and 1 / N (however, N represents an integer of 2 or more) of the maximum load that the weight measuring device can measure, for example, 1 A weight of / 4 is mounted on the weighing pan 2. This makes the load cell 1
Produces a strain proportional to the weight of the weight and outputs a weight signal proportional to the weight of the weight. This weight signal is converted into a digital signal by the analog-to-digital converter 4, converted into the number of pulses, and stored in the memory 7. The memory 7 sequentially stores the weight data output in the sampling cycle of the analog-digital converter 4.

By the way, if the number of counts at the maximum load Wm is set to 4000, the internal resolution becomes 1/4000, and the weight Wm / 4 of 1/4 of the maximum load Wm is measured. When mounted on the dish 2, the analog-digital converter 4 outputs a pulse signal for 1000 counts, and the resolution at that time is 1/10.
00, the resolution is reduced to 1/4 of the maximum load. In other words, the weight of the weight corresponding to the maximum load is 1/40
If it changes by 00, the analog-to-digital converter 4 changes by 1 count, but 1/4 of the maximum load.
When measuring with a load of 1, the same ratio 1 /
Even if the weight changes by 4000, the weight of this change is 1
/ 4 counts only. Needless to say, since the analog-to-digital converter 4 outputs a signal in units of 1 count, this 1/4 count weight change is not reflected in the output data as a digital signal.

However, even in the case of measuring the load of 1/4 of the maximum load, the analog-to-digital converter 4 is affected by the change amount of the weight signal corresponding to the 1/4 count amount, and therefore the reference Load Wn / 4 is 1000
If it corresponds to the number of pulses for the count, it is always 100
Rather than outputting 0 count pulses, if the weight is less than 1 count due to the influence of fluctuation, the ratio to the weight corresponding to 1 count is used as the generation frequency to obtain 1 count data. Will be converted to, and 1001 counts will also be output. In other words, if 1000 counts are output three times, such as 1000 1000 1000 1001 1000 1001 1000 1000 1000 1000 1000 1000, then 1001 counts, which is one more count, will be output once. These data that change with time are sequentially stored in the memory 7. The arithmetic circuit 8 sequentially reads N pieces of data stored in the memory 7, in this case, four pieces of data which are temporally consecutive, in the order in which they are stored, and (1000 + 1000 + 1000 + 1001) = 4001 (1000 + 1000 + 1001 + 1000) = 4001 (1000 + 1001 + 1000 + 1001) = 4002 (1001 + 1000 + 1001 + 1000) = 4002 (1000 + 1001 + 1000 + 1000) = 4001 (1001 + 1000) + 1000 + 1000) = 4001 (1000 + 1000 + 1000 + 1000) = 4000 (1000 + 1000 + 1000 + 1000) = 4000 The moving addition operation is performed.

As a result, data that is one count more than the regular count value 4000, that is, equivalent to the resolution 1/4000 at the maximum load, that is, the measurement range resolution of 1/4 of the maximum load is increased four times. It is possible to obtain the measurement data with the same resolution as that of the other. In this way, the added value Ws = Wn + Wn-1 + Wn-2 + W of the weight four times
At the stage of obtaining n-3, the maximum value (Wm = 4W) obtained by multiplying the added value Ws and the weight of the weight by 4 is obtained from the weighing value setting circuit 9, and the ratio α = Wm / Ws of these is calculated, This is the span coefficient.

When the microcomputer executes the above-described span configuration calculation step, the procedure shown in the flow chart of FIG. 2 is performed. That is,
Set the required number M of data and mount a weight with a weight of 1 / N of the weighing value on the weighing pan (step a). In this state, the analog electric signal output from the load cell 1 is converted into a digital signal (step B). When the digital signal is output, the previous data stored in the memory is shifted and the digital signal Wn output now is stored in the memory (step C). N pieces of data are read in the order stored in the memory, moving addition is performed, the addition result Ws is stored in the memory (step E), and it is determined whether the weighing device is in a stable state (step E). If it is not in a stable state, since the added value Ws just calculated is meaningless data, the number of data M is initialized (step
F, G), and the steps from (B) to (E) are repeated again. On the other hand, when data is collected while the weighing device is stable, the number of data M is decremented by 1 and the process from (step B) is repeated. In this way, the number M of data becomes zero, and the coefficient α is calculated with the predetermined number of addition results Ws as XR (step N,
Le). The coefficient α obtained by the calculation is stored in the memory and used as the coefficient at the time of weighing (step E). In this embodiment, the case where the weight of 1/4 of the maximum load Wm is used is described as an example, but the weight of 1/2, 1/3, 1/5 etc. of the maximum load is used. It is obvious that the same effect is obtained. In these cases, the number of data to be added is 2, 3, 5 and the added values are Ws = Wn + Wn-1, Ws = Wn + Wn-1 + Wn-2, Ws = Wn + Wn-1 + Wn-2 + Wn, respectively. -3 + Wn-4.

[0013]

As described above, according to the present invention,
Load detection means for converting the weight of the object to be measured into an analog electric signal and outputting it, analog-digital conversion means for converting the analog electric signal into a digital signal, and digital signal multiplied by a predetermined coefficient to be converted into weight data In the weighing device equipped with the coefficient means, the storage means for storing a plurality of data from the analog-digital conversion means over time, the means for moving and adding the data in the storage means, and the number of data added to the load are multiplied. Since the multiplication value is divided by the moving addition value to obtain the coefficient of the coefficient means, the measurement data equivalent to the resolution at the maximum load can be obtained, and the integral weight of the maximum weight that can be measured. A weight of 1 can be used to perform span calibration with the same resolution as the maximum weight, and loading and unloading of the weight can be performed without degrading the accuracy of the span configuration. It is possible to significantly reduce the effort of work.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart showing a procedure for executing span calibration by a microcomputer.

[Explanation of symbols]

 1 load cell 2 weighing pan 3 preamplifier 4 analog-digital converter 5 changeover switch 6 coefficient circuit 7 memory 8 arithmetic circuit 11 indicator

Claims (2)

[Claims] 1. A load detecting means for converting the weight of an object to be measured into an analog electric signal and outputting the analog electric signal, an analog-digital converting means for converting the analog electric signal into a digital signal, and a predetermined coefficient for the digital signal. A weighing device having coefficient means for multiplying and converting to weight data,
Storage means for storing a plurality of data from the analog-digital conversion means over time, means for moving and adding the data in the storage means, and multiplying the number of data added to the load,
A weighing device, comprising: a calculating means for dividing the multiplication value by a moving addition value to obtain a coefficient of the coefficient means. 2. A load detecting means for converting the weight of the object to be measured into an analog electric signal and outputting the analog electric signal, an analog-digital converting means for converting the analog electric signal into a digital signal, and a predetermined coefficient for the digital signal. A step of applying a reference load of 1 / N (N represents an integer of 2 or more) of a maximum load that can be measured by the weighing device to a weighing device provided with a coefficient means for multiplying and converting into weight data; A step of sequentially storing the weight data from the analog-to-digital conversion means with time, a step of moving and adding the stored weight data by N while shifting the time by a time, a weight data obtained by the moving addition, and a maximum load. A calibration method comprising the step of adjusting the coefficient of the coefficient means according to the ratio of