SU1255945A1 - Method of measuring amplitude of harmonic signal with infralow frequency - Google Patents

Abstract

The invention can be used to create equipment for recording amplitudes of infra-low-frequency signals in acoustics or automation, as well as in the study of mechanical, dielectric and thermophysical properties of materials by dynamic methods using harmonic external effects of an infra-low frequency. The aim of the invention is to improve the accuracy of determining the amplitude of the harmonic signal (HS), the average level of which during the measurement time varies with a constant speed. The goal is achieved according to this method by sampling the HS with the sampling period T / 20, where T is the period of the HS, then measuring the value of the signal at the discretized points in time, determining and comparing the three extreme following values one after the other. method of successive approximations according to the formula given in the description of the invention. A device that implements the method contains an A / D converter 1, a block 2 of conjugation, a mini-computer 3 and a digitizer 4. 2 Il. (L SL with 4 SL Fig. 2

Description

The invention relates to electrical measuring equipment and can be used to create high-precision equipment for detecting the amplitude of infra-low frequency signals in a wide dynamic and frequency ranges with varying average levels of these signals to determine, for example, in acoustics or automation, the amplitude of the harmonic signal of an infra-low frequency under transient conditions, and in the study of mechanical, dielectric and thermophysical properties of materials by dynamic methods using armonicheskih external influences infra-low frequency

The aim of the invention is to improve the accuracy of determining the amplitude of the harmonic signal, the average level of which changes at a constant speed during the measurement time, is less than the product of the amplitude of this signal by its circular frequency j due to dscretizing the harmonic signal with the sampling period T

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

The measured voltage U (t) is fed to the input of an analog-to-digital converter and at sampled times the value of

0 voltages are entered through interface 2 into mini-computer 3, in which the input values are compared with each other and three extreme values are determined, following one after another

15 values Uj - Ug of the voltage U (t) (one value for each half-period of the harmonic signal), and then the amplitude of the harmonic signal is calculated using the formula

20 (1). The necessary information from the mini-computer is output to the digitizer 4.

Form la invention

25

CII i-

20

where T is the period of the mentioned signal, the signal values are measured at sampled times, MeHHj, the measured values are compared with each other and three extremal ones are determined, followed one after another, and the desired amplitude of the harmonic signal A. method of successive approximations according to the formula

. UvU;;

- .. 2tft;

where D, - U is the extreme values of the signal, A-, is the amplitude value defined in the previous cycle 5At the initial value of the amplitude lu, 2D ,, + U3i. The hell is taken equal to A –j ----.

FIG. Figure 1 shows the measured voltage U (t), which is a harmonic signal, the mean value of which varies with a constant velocity U (t) c (t) + A sin ("i +, (f); Fig. 2 - block diagram of the device that implements this method.

The method of determining the amplitude of the harmonic signal of an infra-low frequency, based on the measurement of the instantaneous values of the signal, characterized in that, in order to improve accuracy, the harmonic signal with periT is sampled

OG discretization

the period of the signal, the signal values are measured at sampled points in time, the measured values are compared with each other and r 1}, three of them are determined by one of the following extreme values, and the desired amplitude of the harmonic signal A is determined by the method of successive approximations using the formula

4S. ftU.- Zil. UvU, f7, UrU. | UrU.

,,, „.. ,,„, 5 ... jj .j,

where U, Ug, Uj are the extreme values of the signal; A ;, is the amplitude value determined in the previous cycle, with the initial value of said amplitude Hell is equal to

AO "-2Uz + U3

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

The measured voltage U (t) is fed to the input of an analog-to-digital converter and at sampled times the value of

the voltage through the interface 2 is entered into the mini-computer 3, in which the input values are compared with each other and three extreme ones are determined, following one after another

the values Uj - Ug of the voltage U (t) (one value for each half-period of the harmonic signal), and then the amplitude of the harmonic signal is calculated using the formula

(one). The necessary information from the mini-computer is output to the digitizer 4.

Form la invention

mthC (t) -f Asin ((jt i if}

Phi2.1

Claims (1)

A method for determining the amplitude of a harmonic signal of infra-low frequency, based on measuring the instantaneous values of the signal, characterized in that, in order to improve accuracy, a harmonic signal is sampled with a sampling period of € <-, where T is the period of the mentioned signal, signal values are measured at sampled times, compare the measured values with each other and determine from them three extreme values following one after another, and the desired amplitude of the harmonic signal A is determined by the method of nyh approximation formula