SU1674004A1 - Method for determination of amplitude of infralow frequency harmonic signal - Google Patents

Abstract

The invention relates to electrical measuring and information measuring equipment and can be used in equipment for recording the amplitude of harmonic infra-low frequency signals with varying average levels of these signals arising in acoustics, automation, studies of the mechanical, dielectric and thermal properties of materials using dynamic methods using harmonic external influences. infra-low frequency. In order to improve the accuracy of determining the amplitude of the sample, the instantaneous values of the input signal are made after a quarter of a period, and the processing of measurement results is performed according to the algorithm described in the description. The device for implementation contains an analog-to-digital converter (ADC) 1, a conjugation unit 2, a mini-computer 3 and a digital printing unit 4. According to computer commands 3, the ADC 1 samples the instantaneous values, which are processed by the appropriate algorithm in computer 3. 1 sludge.

Description

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U (t) B (t) + AMfat +

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The invention relates to electrical measuring and information measuring equipment and can be used to create high-precision equipment for recording the amplitude of infra-low-frequency signals with varying average levels of these signals, for determining, for example, in acoustics or automation, the amplitude of the harmonic signal of the infra-low frequency at transient regimes, as well as in the study of the mechanical, dielectric, and thermophysical properties of materials by dynamic methods using harmonic external effects of infra frequency

The aim of the invention is to improve the accuracy of determining the amplitude of a harmonic signal, during which the average level varies either linearly with a speed exceeding the product of the amplitude of this signal by its circular frequency, or monotonously with a variable speed.

The method for determining the amplitude of the harmonic signal of the infra-low frequency is as follows.

A harmonic signal with a varying average level can be represented analytically in the form

U (t) B (t) + Asln (wt + ip). where A, (p. (a In / T is constant, B (t) is a monotonically changing value during the measurement time).

In this case, the instantaneous values of the measured signal are recorded after a quarter of a period, and the AN is calculated by the formula:

AN Ysfc + Cfc (-1) l || (KKLl) -U2, -f-i

1 0,1,2, ...,

Cni% -A (-i) J

2 J -O U2J +2

k and m are the whole part of (N-1J / 2 and (N-2) / 2, respectively, N 2 is the number of measurements, and the value of the determined amplitude of the harmonic signal is taken to be the value AN, which differs from the value of AN-I by smaller preset.

The drawing shows a block diagram of a device for implementing a method for determining the amplitude of a harmonic signal of an infraslow frequency.

The device contains serially connected analog-to-digital converter 1, interface 2, mini-computer 3, and digital printing unit 4.

The device works as follows.

The measured voltage U (t) is fed to the input of the analog-digital converter 1. At fixed points in time,

asked by the mini-computer 3, the values of this voltage are entered through the interface 2 into the mini-computer, which after each measurement calculates the values of AN using the formulas produced, compares the values of AN and Am-1, chooses the value of AN, which is different from the value of the harmonic signal, AN-I by an amount less than a given E (for example, 0.1%). The necessary information from the mini-computer is output to the digital printing unit 4.

Claims (1)

The invention The method for determining the amplitude of the harmonic signal of infra-low frequency consisting in measuring the instantaneous values of the signal, characterized in that, in order to increase the accuracy of determining the amplitude of the harmonic signal, which has an average the level varies either linearly with a speed greater than the product of the amplitude of this signal by its circular frequency, or monotonously with variable speed, the instantaneous the UN values of the signal under study at intervals of a quarter of the harmonic signal period, calculate the AN values using the formula 40 AN VSiT + CiT Where 45 r -l $ r 1v. t | . . - Lm 2mjt J (m-J) 50 2J + 2 J 0,1,2, ... m; k and m are the whole part of (N-1) / 2 and (N-2) / 2, respectively; N 2 is the number of measurements, and the value AN, which differs from the AN-I value by an amount less than the set value, is taken as the value of the detectable amplitude of the 55 harmonic signal.