JPH0192665A - Measuring method for peak value - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial application field This invention samples a measurement signal such as a load that is continuously input in, for example, an electronic balance, captures a data string, and uses this data string to , relates to a peak value measurement method for determining the peak value of a measurement signal.

(b) Conventional technology Conventionally, in order to measure the peak value of a load signal, sampling is performed, the local maximum value (or minimum value) in the captured data string is extracted, and that data value is used as the peak value of the measurement signal. It is said that For example, each data of the load value a read in time sequence at the sampling period Δt is not shown in FIG.
, ..., al4, the load a7 becomes the peak value.

(c) Problems to be solved by the invention Generally, the sampling period Δt is never O,
Requires a certain finite value. On the other hand, when the rate of change of the load is fast, the peak point almost always occurs between one sampling point and the next sampling point, and the peak value rarely coincides with the sampling point. Therefore, when extracting a peak value from sampled data as in the conventional method, the peak value is often a value that is far from the true peak value, making it impossible to measure the correct peak value. Once the sampling period is determined, the rate of change in load is also limited to a certain level or less. For example, using a balance with a sampling period of 0.1 seconds, ±1 mg
In order to measure the peak value with an accuracy of , the rate of change of the load must be Imglo, 1 s - 0.

It needed to be 0.01 g/sec or less.

In order to shorten the measurement time of the peak value, it is effective to increase the rate of change of the load, but this has been difficult to achieve due to the above-mentioned limitations. Furthermore, since the rate of load change is limited, there is a problem in that the influence of creep of the material under test cannot be ignored.

In view of the above, it is an object of the present invention to provide a peak value measuring method that can obtain accurate peak values even if the rate of change in load is higher than conventional methods.

(d) Means and action to solve the problem When measuring the peak value of actual load, the state of the object to be measured often differs significantly before and after the occurrence of the peak value, such as fracture, collision, buckling, etc. The generation status of load symbols also differs greatly. Focusing on this point, each approximate curve for the data string before and after the peak value is a completely different time function f (t), g (
t), and it can be said that the intersection point Amax is closest to the true peak value (see FIG. 5).

The peak value measurement method of the present invention adopts the above principle, in which a continuously input measurement signal is sampled at a predetermined period, a measurement data string is captured, and a measurement signal is generated based on the measurement data string. A method for measuring the peak value of the measured data string, the method includes determining the extreme value of the measured data string, generating two different approximate curves of the measured data string before and after this extreme value, and extracting the intersection of these two approximate curves. The level value at this intersection is taken as the peak value.

In this peak value measurement method, for example, as shown in FIG. 5, the data string alsa2, .
..., obtain a14. And the extreme value of this data string,
For example, find a7. Data strings before and after this extreme value a7,
For example, alsa2,..., a7 and aB, a9,...
..., from a14, two different approximate curves f(t) and g
(t). And these two approximate curves f
The intersection point Amax of (t) and g(t) is found, and this is taken as the peak value. From this, a peak value Amax closer to the true value than a7 can be obtained.

(e) Examples The present invention will be explained in more detail with reference to Examples below.

FIG. 2 is a block diagram of an electronic balance in which the present invention is implemented. In the figure, a load signal detected by a load sensor 1 is sampled every ΔL by an A/D converter 2, taken into a CPU 3, and stored in a RAM 4.

The CPU 3 executes the program stored in the ROM 5.
Execute peak value detection processing. That is, CPU3 is
A function to import a data string from the A/D converter 2 and store it in the RAM 4, a function to extract the extreme value of the data string from the stored data string, and two different near-A curves before and after the extracted extreme value. , a function to find the intersection of these two approximate curves, and a function to output the level of the found intersection as a peak value. The peak value output from the CPU 3 is displayed on the display 6. The generation of the approximate curve by the CPU 3 is performed using, for example, the least squares method or the Lagrange interpolation method.

Next, the peak value measurement operation in the electronic balance of this embodiment will be explained with reference to the flowchart shown in FIG.

In FIG. 1, when the operation starts, the variable i is first set to 1 [step ST (hereinafter abbreviated as ST) 1]. This variable i indicates the number of data to be sampled and input. Then, this time it is input and the A/D converter 2
The measurement signal converted into a digital value is stored as a (Sr1).

Next, the current measurement value a (and the previous measurement value a, -3 are compared, and it is determined that a , <a; -1 (Sr1)
.

If the measurement signal is rising, this determination becomes No, and then it is determined whether i=k (Sr4). k is a constant that defines the number of measurement data stored, and at the beginning of measurement, N
In this case, the variable j is incremented by +1 and (Sr
1), return to Sr2, continue measurement, and change from Sr2 to ST3
→ Repeat the process of Sr4 → ST6 → ST2. Measured value a,
If it becomes i- before moving down, the judgment of Sr4 is Y.
ES, then stored data a2, a3,..., a
Shift k, aI, a2,..., ak-1
, erase the original al, and store 11 as new data (Sr5).

Next, when the measured value a starts to fall, that is, as in the example shown in FIG. H<
a ++-++" is YES. Therefore, the process moves to Sr7, and it is determined whether or not i=k. This judgment is normally YES, and the process moves to Sr1, but if the judgment is No, the process proceeds to Sr1. Displays an error.

In Sr1, the variable j is set to 1, and then the measured data is stored as bJ (STIO). , i is a variable indicating the measurement data number after descending. After storing the current measurement data b1, it is determined at 5TII whether or not i=L. L is a constant that defines the number of measurement data stored after falling. At the beginning when the measured data shifts from rising to falling, j = 1, so the judgment is No. At 5T12, j is increased by +1 step and returns to 5TIO. From then on, until i = L, 5TIO → 5TII → 5
Continue processing from T12→5TIO and continue collecting measurement data.

When j=L, the judgment of 5TII becomes YES, and 5T
Move on to 13. Then, according to the data of a1 to ah-+,
The approximation function f (t) is generated, and the approximation function g(t) is generated using the data b, ~bL. In the example shown in FIG. 3, the function fo(t) is generated by a4, as, , ab, and the function g is generated by aB, a9, a IQ, al. (1
) is generated. Thus, here the function f. (t
), go (t), the extreme value a7 (ai
+) is removed. For convenience, f is obtained by excluding the extreme value a7. (
The intersection point Amax (see FIG. 3) of t) and go(t) may be determined and used as the peak value. But in the middle of nowhere,
The question is whether a7 is included in the earlier curve or in the later curve; in other words, has it not yet reached the true peak value at time L7, or has it already reached the true peak value? The problem remains. Therefore, in this example, in order to obtain a peak value closer to the true peak value, in 5T14, l ah f+t=+r+ l and fa
A comparison of l is made to irg +t=. For example, in the example of FIG. 3, the difference value Eg between go (t, l and a7)
o, a, 7. and f. (The difference value g of t7+ is compared. Then, in l ah − f tt=, l≦ l
ah g <If t=+n1, ak is f(t
), and re-create the function f (t) using data from a1 to aa5T15).
The intersection of g(t) and g(t) is set as a peak value, and this is displayed on the display 6 (ST17). In the example shown in Figure 3, since Cgo>Cfo, a new curve f+(t) is created assuming that a7 is included in fo(t) (Figure 4), and the curve f+(t) and curve go Let the intersection point Amax + of (t) be the beat value.

If 5T14, l ak f+t=h+ l>la
If kg Lt= + l, then ak is f (t)
, g(t) is regenerated using the data of ak , I) I-b, (ST16), and g(t) after this regeneration and the original f (t) Find the intersection of
This level value will be taken as the peak value. (STI7
).

In the above description, the case where the local maximum value is determined is explained, but the present invention can also be applied to the case where the local minimum value is determined. Further, in the above embodiment, the sampling period is constant, but in the present invention, it does not need to be constant, and it is sufficient if each sampling time is clear.

Further, in the above embodiment, a method for measuring a load peak value in an electronic balance has been described, but the present invention is applicable not only to load peak values but also to various methods for measuring peak values.

(f) Effects of the Invention According to the present invention, an extreme value of a data string is first obtained from sampling data, and then two different approximate curves are obtained from the data strings before and after this extreme value. Since the intersection point is found and the level value thereof is taken as the peak value, an accurate peak value can be obtained even if the peak value is within the sampling period. Therefore, if the sampling period is the same, for example, the load change rate can be increased and the measurement time can be shortened compared to the conventional method. Furthermore, it is not necessary to make the sampling period extremely short in order to improve measurement accuracy.

[Brief explanation of the drawing]

FIG. 1 is a flow diagram for explaining the peak value measurement operation of an electronic balance according to an embodiment of the present invention, FIG. 2 is a block diagram of an electronic balance in which the present invention is implemented, and FIGS. 3 and 4 are ,
FIG. 5 is an exemplary explanatory diagram for explaining the peak value measuring operation of the electronic balance, and FIG. 5 is an exemplary explanatory diagram for explaining the peak value measuring method of the prior art and the present invention. 1: Sensor, 2: A/D converter. 3: cPU, 6: Display unit. Patent Applicant Shimadzu Corporation Representative Patent Attorney Shigeru Nakamura 8!

Claims (2)

[Claims] (1) A method of sampling a continuously input measurement signal at a predetermined period, capturing a measurement data string, and measuring the peak value of the measurement signal based on this measurement data string, the method comprising: determining the extreme value of the column, generating two different approximate curves of the measurement data column before and after this extreme value,
A peak value measurement method that extracts the intersection of these two approximate curves and uses the level value at this intersection as the peak value. (2) The two approximate curves are generated using other data strings excluding the extreme values of the measured data string, and then the difference between the extreme values of the data string and the level values of the two approximate curves at that point. A patent claim in which a value is determined, a new approximate curve is generated by including the extreme value in the approximate curve with the smaller difference value, and an intersection point between this new approximate curve and another approximate curve is determined. The method for measuring the peak value according to item 1.