JPH0552887A - Retrieving method for period of waveform data taken in for measurement of harmonic by use of memory recorder - Google Patents

Abstract

PURPOSE:To enable accurate measurement of a high frequency by specifying a data train to be retrieved of which the difference sum in the relation of the period of waveform data taken in with a reference data train is the minimum. CONSTITUTION:A large number of sampling points are set for waveform data 3 taken in and a reference data train SDATA(N) is specified out of discrete data trains positioned between the adjacent sampling points. Each other data train corresponding to this reference data train SDATA(N) is made to be a data train to be retrieved, a difference sum between this and the reference data train SDATA(N) is determined discretely, the data train DATA(N) to be retrieved of which the difference sum is the minimum is detected, a sampling point A at which the beginning-end data thereof are positioned is specified, and the number of sampling points between the above sampling point A and a sampling point P at which the beginning-end data in the reference data train SDATA(N) are positioned is made to be one period of the waveform data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a period search method for waveform data acquired for measuring harmonics by a memory recorder.

[0002]

2. Description of the Related Art Harmonic measurement is performed by obtaining frequency components by Fourier transform of waveform data of one cycle. It is known that the Fourier transform in this case can be processed at high speed by using the FFT algorithm. However, the number of sampling points of the waveform data that can be efficiently calculated by the FFT algorithm is always limited to a power of 2.

Therefore, even if the period of the waveform 1 to be measured is the number of sampling points corresponding to exactly the power of 2 (for example, data for points of 2 ⁷ = 128, 2 ⁸ = 256, 2 ⁹ = 512, ...). If there is no problem.

However, when the sampling speed is fixed as in the existing memory recorder, it is difficult in almost all cases to match the sampling data to the power of 2.

On the other hand, a conventional harmonic measuring device can obtain a clock obtained by dividing an input signal frequency into an arbitrary number including a power of 2, and thus the clock frequency that determines the sampling rate can be changed. Therefore, it was possible to adjust so that the power of 2 data was sampled in one cycle.

[0006]

By the way, according to the above harmonic measuring device, since the clock frequency for determining the sampling speed can be changed, one cycle is equal to the number of sampling points of power of 2. It is possible to get familiar with FFT operation.

However, unlike the above-mentioned harmonic measuring device, in the case of the memory recorder, the clock frequency is fixed, so that the sampling speed cannot be made variable according to the waveform data to be taken.

For this reason, in the FFT operation, it is necessary to first accurately search one cycle of the waveform data and to perform a necessary correction process in relation to the searched one cycle.

In this case, a trigger level is set in advance for one cycle of waveform data taken in as an input signal on the side of the equipment main body, and the waveform data crosses this trigger level again and then again. It is searched by finding the time to pass through the same pattern and the number of data.

However, when the waveform data to be taken in contains noise, this noise component may exceed a preset trigger level, so that the cycle accuracy searched by the above method is deteriorated. There was an inconvenience.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems found in the conventional method, and its structural feature is that stored data can be transmitted / received to / from a device body. In a memory recorder provided with an external storage medium formed, for a series of waveform data captured on the device body side, first, according to the program stored in the external storage medium, a large number of samplings are performed. By setting points, specify the reference data string that is determined by the relationship with the concrete waveform pattern from among the individual data strings that are located between the adjacent sampling points at these many sampling points. Each of the other data strings corresponding to the reference data string is individually used as a searched data string to obtain a sum of differences between the reference data string and
The search data string having the smallest sum of differences is detected, the sampling point A at which the start end data is located is specified, and sampling between this sampling point A and the sampling point P at which the start end data is located in the reference data string is performed. The number of points is one cycle of the waveform data.

[0012]

Therefore, even with the conventional type memory recorder, the cycle of the waveform data fetched as an input signal to the device body side specifies the searched data string having the smallest sum of differences in relation to the reference data string. You can easily search by doing.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a block diagram showing a schematic configuration of a memory recorder used for implementing the present invention. The device body 11 includes an analog unit 15 and a logic unit 16.
The input data is provided to the input unit 17, and the input data is arithmetically controlled via the CPU 12 operated by the program stored in the ROM 25 by the operation of the operation unit 19, and measured to the output unit 18 such as a printer or an LCD display. The output display of the result is possible.

An external storage medium 20 such as a RAM card, a ROM card or an IC card can be attached to the device body 11, and the device body 11 side of the data stored in the external storage medium 20 can be mounted. Is formed to allow loading into.

In the figure, reference numeral 13 is a clock.
4 is a frequency dividing circuit, 21 is an interface, 22 is a memory controller, 23 is a built-in RAM,
Reference numerals 24 respectively indicate trigger parts.

FIG. 1 is a flow chart showing a processing procedure as an embodiment of the method of the present invention which is carried out via a memory recorder as shown in FIG. 3, for example.

As shown in the figure, first, a reference data string (SDATA [N]) consisting of N pieces suitable for searching the cycle of the waveform data 3 is specified.

The details of the processing here will be specifically described with reference to the waveform data 3 of the sine wave pattern shown in FIG. 2 as an example. Large reference data string (SDATA
[N]), for example, for N data strings existing between the sampling point P and the sampling point P + N on the horizontal axis 1, the start end data where the sampling point P is located and the end data where the sampling point P + N is located The data string having the largest numerical difference (absolute value) on the vertical axis 2 and thus the largest slope is searched for, and this is the reference data string (SDATA [N]).
Is specified as.

In this way, the reference data string (SDATA
After [N] is specified, this reference data string (SDA
The search start point P + K for shortening the search time is set on the horizontal axis 1 based on the sampling point P in TA [N]) where the start point data is located, and the search start point P + K is set to the subsequent position. The number of consecutive continuous data is set in the counter.

Thus, until the counter in which the number of data is set indicates "0", the search target data string (DATA) is sequentially divided from the search start point P + K by N pieces.
[N]) and the corresponding individual data in the reference data string (SDATA [N]) are calculated as absolute values, and all the differences as absolute values are calculated. The sum of differences (SA [K]) is obtained by adding.

The difference sum (SA
[K]) is the searched data string (DATA) immediately before that.
The difference sum (SA [K] already calculated for [N])
−1]) is compared with the magnitude, and when it is determined to be small, a variable maxCYCLE indicating the difference between the sampling point P and the sampling point A when the difference sum is the minimum.
Is set to K indicating the number of sampling points at that time, K = K + 1 is set, the process returns to the counter determination step again, and the same processing is performed.

When SA [K] <SA [K-1] is not satisfied, SA [K] has SA [K- so that the minimum sum of differences is always included in SA [K-1]. 1],
After setting K = K + 1, the process again returns to the counter determination step and the same processing is performed.

On the other hand, when the counter is judged to be "0" in the counter judging step, the cycle =
The maxCYCLE processing is performed, and the waveform data 3
One cycle is searched, and a series of processing ends.

Since the present invention is configured as described above, the waveform data 3 fetched on the side of the device main body 11 has the reference data string (SD) in advance as shown in FIG. 2, for example.
ATA [N]), which is a data string existing between sampling points P and sampling points P + N, and N points from the search start point P + K are set as one segment, and subsequently, each searched data determined for each sampling point. Sum of differences (SA with column (DATA [N])
[K]) will be required respectively.

The calculated reference data string (SDATA
[N]) and each difference sum (SA [K])
The searched data string (SDATA [N]) having the smallest sum of differences (SA [K]), for example, the searched data string (SDATA [N]) located between two points shown as sampling point A and sampling point A + N in the figure ( SDATA [N])
Is specified.

After specifying the searched data string (SDATA [N]) having the smallest sum of differences (SA [K]) in this way, the start data of the reference data string (SDATA [N]) is located. From the sampling point P to the sampling point A where the start end data of the searched data string (SDATA [N]) is located, one cycle of the waveform data 3 is searched.

Therefore, even if the waveform data 3 fetched on the device body 11 side contains noise or is accompanied by distortion, these noise and distortion components are sum of differences (SA). [K]) to be absorbed,
Since the influence can be lost, one cycle of the waveform data 3 can be accurately obtained.

Therefore, even if harmonic measurement is performed using a conventional memory coder, the device body 1
By supplying the external storage medium 20 in which the processing program for that is stored to 1, it is possible to accurately search one cycle of the waveform data 3, and as a result, the FFT calculation for calculating the harmonics. Can be done more accurately.

[0030]

As described above, according to the present invention, even in the conventional type memory recorder, the cycle of the waveform data taken in as an input signal on the device body side is the sum of the differences in relation to the reference data string. It is possible to easily search by specifying the searched data string having the minimum value, which can be a help for realizing accurate harmonic measurement by the memory recorder.

[Brief description of drawings]

FIG. 1 is a flowchart showing a processing procedure as an embodiment of the present invention.

FIG. 2 is an explanatory view for clarifying the relationship of the explanatory views showing the correspondence between the waveform data and the method of the present invention.

FIG. 3 is a block diagram showing an outline of a device body used for carrying out the method of the present invention.

[Explanation of symbols]

 3 waveform data 11 device body 17 input unit 20 external storage medium

Claims (1)

[Claims] 1. A memory recorder provided with an external storage medium capable of transmitting and receiving stored data to and from a device body, wherein a series of waveform data captured on the side of the device body is: According to the program stored in the external storage medium, first, a large number of sampling points are set, and from among the individual data strings located between the adjacent sampling points at the large number of sampling points, Specify a reference data string determined by the relationship with a specific waveform pattern, and individually obtain the sum of differences between the reference data string and each other data string corresponding to this reference data string as a searched data string, this house,
The search data string having the smallest sum of differences is detected, the sampling point A at which the start end data is located is specified, and sampling between this sampling point A and the sampling point P at which the start end data is located in the reference data string is performed. A period search method for waveform data taken in for harmonic measurement by a memory recorder, wherein the number of points is one period of the waveform data.