JPH037247B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a zero point correction device for a measuring instrument, and particularly to one for a measuring instrument in which the amount of deposits increases as the number of measurements increases.

In general, there are various types of measuring instruments. For example, if a measuring device with a load cell installed in the measuring tank repeatedly measures and discharges powder, etc., some of the powder, etc. may be discharged. also adheres to the measuring tank,
As shown in FIG. 1, the amount of adhesion increased non-linearly as the number of measurements increased. Conventionally, in such measuring instruments, the zero point correction device used for accurate measurement has been used to temporarily stop measurement every time several measurements are performed, and calculate the amount of deposited at that time (first a ₁ , a ₂ , an shown in the figure
) is stored in the memory 2, and then the value stored in the memory 2 is subtracted by the subtractor 6 from the measurement signal of the measuring instrument 4 until the value stored in the memory 2 is updated. However, this has the problem that if the number of times of measurement is large before updating the value stored in the memory 2, the value stored in the memory 2 and the actual amount of adhesion will be too far apart, and the correction effect will be weakened. In order to prevent this, if the number of measurements taken before updating the stored value in the memory 2 is reduced, the number of stops of the weighing device will increase, resulting in a decrease in the measurement ability.

This invention was made to solve the above two problems at the same time.As shown in Fig. 1, when the amount of adhesion increases non-linearly as the number of measurements increases, is determined, and the predicted values b ₁ , b ₂ ...bn of the adhesion amount at each sample point are known, the curve representing the adhesion amount is a broken line connecting each predicted value (indicated by a dotted line in Figure 1). This method takes advantage of the fact that it can be approximated by

Therefore, the present invention includes a storage unit that stores the predicted value of the adhesion amount at each sample point, and a storage unit that stores the gradient coefficient between each sample point, n and n.
a counter that counts the number of measurements between +1 sample points; a multiplier that multiplies the count value by a gradient coefficient between n and n+1 sample points read from the storage unit; It is comprised of a subtracter that subtracts the multiplication value of the multiplier and the predicted value of the n-th sample point read from the storage unit from the measurement signal of the measuring device when counting.

With this configuration, n
Let the predicted value at the th sample point be βn, and the predicted value at the n+1th sample point be β(n+1),
The gradient coefficient αn between these two sample points is {β
(n+1)-βn}/γ. However, γ is the number of measurements between the n and (n+1)th sample points. Therefore, during the measurement between the nth and (n+1)th sample points, αn and βn are read from the storage unit, and for example, when measuring the third sample point counting from the nth sample point, Since the adhesion amount is determined by 3αn + βn, multiply the count value 3 of the counter by αn using a multiplier, and calculate the multiplied value from the measurement signal from the third measurement.
The true metric value is obtained by subtracting 3αn and βn using a subtracter.

According to this method, there is no need to take the trouble to stop the measurement and update the stored value in the memory, and the amount of adhesion is calculated using a broken line approximation, so the accuracy is very high.

In the above invention, since a predicted value is used for βn, its accuracy is somewhat low. Therefore, in another invention, only the gradient coefficient is stored in the storage section, and the actual adhesion amount at the n-th sample point is stored in another storage section, and the above multiplication value and n The actual adhesion amount at the second sample point is subtracted.

Hereinafter, these two inventions will be explained in detail based on three embodiments shown in FIGS. 4 to 6. Fourth
The figure shows a first embodiment, and in the figure 10 is a measuring instrument. Reference numeral 12 is a memory in which predicted values β1,
β2...βm and gradient coefficients α1, α2...αm between predicted values of each sample point are stored.

These predicted values and gradient coefficients are stored in the counter 14
and read out by the readout circuit 16. That is, the counter 14 counts the number of measurements based on the measurement signal generated by the measuring instrument 10. The count value C1 is supplied to the readout circuit 16, and the readout circuit 1
6 is α1 until the count value reaches N1
and β1, and if the count value exceeds N1, then N
α2 and β2 are read until the value reaches 2. Thereafter, in the same manner, αm and βm are sequentially read out. The gradient coefficient read out in this way is sent to the multiplier 18.
Then, the predicted value is provided to adder 20.

The multiplier 18 multiplies the count value C2 of the counter 22 by the gradient coefficient. The counter 22 also counts the number of times the weighing device 10 weighs based on the weighing signal, but it is different from the counter 14 in that
The count value C1 of the counter 14 is N1, N2...
Each time it reaches Nm, it is reset by a signal from the readout circuit 16. Therefore, the count value C2 of the counter 22 always represents the number of times of measurement from one sample point to the next sample point. Therefore, as described above, the value obtained by adding the predicted value to the multiplication value of the count value C2 of the counter 22 and the gradient coefficient by the adder 20 represents an approximate value of the adhesion amount at that time. Zero point correction is performed by subtracting this approximate value using a subtracter 24. It goes without saying that the counter 14 is reset when the deposit is removed.

The second embodiment differs in that the first embodiment uses the predicted value of the amount of adhesion at each sample point, whereas the actual amount of adhesion at each sample point is used. That is, as shown in FIG. 5, the gradient coefficients α1 to αm are stored in the memory 26.
When the count value C1 of the counter 14 reaches N1 to Nm, the readout circuit 1
The actual adhesion amount, which is the value under no load at that time, is stored in the memory 28 by the output of step 6, and thereafter,
A subtracter 30 subtracts the value stored in the memory 28 from the measurement signal of the scale 10, and a subtracter 32 subtracts the output of the multiplier 18 from the subtracted output of the subtracter 30. The accuracy will be higher if the actual deposition amount is used rather than the predicted value.

In contrast to the first and second embodiments, in which the gradient coefficient is predetermined, the third embodiment determines the amount of adhesion upon completion of a predetermined number of measurements and the amount of adhesion before starting this predetermined number of measurements. The difference is that the following gradient coefficient is determined from the amount of adhesion. That is, in FIG. 6, a counter 34 counts the number of measurements based on the measurement signal from the measuring instrument 10, and generates an output when the count value reaches a predetermined number of times. 36
is a memory that stores the actual amount of adhesion before the counter 34 starts counting anew. When the counter counts a predetermined number of times, the scale 10 generates a measurement signal representing the amount of adhesion at that time. The difference between this weighing signal and the value stored in the memory 36 is obtained by a subtracter 38, the difference is divided by the count value of the counter by a divider 40, and a suitable constant K1 is calculated by a multiplier 42. is multiplied to obtain the following gradient coefficient: When this is obtained, the output of the counter 34 delayed by the delay circuit 44 (the output generated by the counter 34 when the count value of the counter 34 reaches a predetermined value) is supplied to the memories 36, 46 and the counter 34, and the memory 36 The stored value is updated to the adhesion amount at that time, and the memory 46
stores the newly calculated gradient coefficient, and the counter 34 is reset.

Thereafter, when weighing is restarted, the subtracter 48 subtracts the value stored in the memory 36 from the measurement signal of the meter, and the multiplier 50 multiplies the count value of the counter 34 and the value stored in the memory 46. . A subtracter 52 subtracts the multiplication value of the multiplier 50 from the subtracted output of the subtracter 48 to perform zero point correction. Note that the changeover switch 54 interposed between the memory 46 and the multiplier 50 is initially used to use the constant K2 as the gradient coefficient since it cannot calculate the gradient coefficient.

In each of the embodiments described above, the present invention is implemented in an ordinary measuring instrument, but it can also be implemented in a measuring instrument used in a combination scale.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship between the number of times of measurement with a measuring instrument and the amount of adhesion on the measuring instrument, Fig. 2 is a block diagram of a conventional zero point correction device, and Fig. 3 is an explanation of the principle of the zero point correction device according to the present invention. Figure 4 is a block diagram of the first embodiment of the zero point correction device;
FIG. 5 is a block diagram of a second embodiment of the zero point correction device, and FIG. 6 is a block diagram of a third embodiment of the same zero point correction device. 10... Measuring device, 12... Storage unit, 18... Multiplier,
22... Counter, 24, 32, 52... Subtractor, 2
6, 46...first storage section, 28, 36...second storage section.

Claims (1)

[Scope of Claims] 1. In a measuring instrument in which even when an article to be weighed is discharged, part of it remains as deposits, and the amount of deposits increases non-linearly as the number of measurements increases, a storage unit that stores a predicted value of the amount of deposits at a number of sample points smaller than the number of times of measurement when weighing across the body, and also stores a gradient coefficient between each sample point; and an n-th sample point. a counter that counts the number of times of measurement between and the n+1th sample point, and a gradient coefficient between the count value and the nth sample point and the n+1th sample point read from the storage unit; a multiplier that multiplies the value of the multiplier, and a predicted value of the amount of the deposit at the n-th sample point read from the storage unit based on the measurement signal of the scale when the count is performed. A zero point correction device for a measuring instrument consisting of a subtracter that performs subtraction. 2 Even when the article to be weighed is discharged, some of it remains as deposits, and as the number of measurements increases, the amount of deposits increases non-linearly. a first storage unit that stores a gradient coefficient between predicted values of the amount of deposits at sample points smaller than the number of measurements; and a second storage unit that stores the actual amount of deposits at the sample points. a storage unit, a counter that counts the number of measurements at the n-th and n+1-th sampling points, and a counter that counts the number of measurements at the n-th and n+1-th sampling points read from the first storage unit; A multiplier that multiplies the gradient coefficient, and a multiplication value of the multiplier based on the measurement signal of the measuring device when the counting is performed, and the actual deposit at the n-th sample point read from the second storage section. A zero point correction device for a measuring instrument consisting of a quantity and a subtracter for subtracting the quantity.