SU447623A1 - The method of measuring the current voltage infra-low frequency - Google Patents

Description

one

The invention relates to electrical measuring equipment and can be used to automatically measure the effective value of an alternating voltage in the range of 0.01-1 Hz.

Methods are known for measuring the effective voltage of an infra-low frequency, based on the approximate replacement of a voltage envelope with a broken line and then integrating this line by filling its segments with pulses of varying frequency and counting these pulses. The accuracy of this method is limited by the accuracy of the approximation and the effect of high-frequency interference on the measurement result.

The purpose of the invention is to increase the accuracy of measuring the current voltage of infra-low frequency.

For this, according to the proposed method, by repeated double integration, the measured voltage is first converted into a time interval proportional to the sum of squares of instantaneous values, then into a time interval proportional to the square of the effective value, and thereafter into the time interval proportional to the directly acting value of the measured voltage, and fill these intervals with pulses of a fixed frequency.

The essence of the proposed method is as follows.

The effective voltage of alternating current Uz can be defined as the sum of the squares of the instantaneous values of the voltages Uxi taken n times in a period

2

 Have

i l

(one)

In order to obtain the number of pulses proportional to the current voltage, integrate the measured voltage Ux by one integrator over a time interval (here T is the period of the measured voltage), then the second integrator over the time interval determined by the discharge time of the capacitor the reference voltage UQ, then the discharge time i of the integrator capacitor voltage UQ will be proportional to the square of Uxi

t -.jl ,,

(2)

25 ul

Such integration re times for the period T p filling the time interval ti pulses of a fixed frequency fo with summation

thirty

e ",., - - v .-.

them in the counter at the end of period T gives the sum of pulses L

l

ul

proportional to the sum of the squares of the Uxi values of the measured voltage.

The division of L by the number of integration cycles p for the period T is carried out by integrating the reference voltage UQ over the interval

L time -, after which the capacitor integra / 0

tori are discharged by a voltage proportional to the number of clock cycles and the reference voltage Uo, which, for example, can be obtained using a code to voltage converter,

and p and -K, (4)

where X is the proportionality coefficient.

The number of pulses received in the counter during the discharge time of the integrator capacitor is equal to

BUT.()

lg-p-s / o

A measurement result, proportional to the effective value of Them, is obtained by applying to the integrator over a voltage time t / jv, and

Ui, K-U, -N,

when the integrator capacitor discharges by a linearly increasing voltage Uz proportional to t / o and fo.

447623

U, CJ, hiK

(6)

and filling the pulses with a fixed frequency / o of the discharge time interval, the meter will record the sum of the pulses proportional to the current voltage.

. 1/22 y,

1 I /

(7) and

about GK-p

Voltage Integration Well, reduces

the effect of interference with a period less than to

measurement accuracy, integrating directly Ux also has a positive effect on

measurement accuracy.

Subject invention

A method of measuring the effective voltage of infra-low frequency, based on converting the instantaneous values of the measured voltage to the time interval, filling this interval with pulses and summing these pulses, characterized in that, in order to improve the accuracy, by repeated double integration, the measured voltage is first converted into a time interval proportional to the sum of squares of instantaneous values, then to a time interval proportional to the square of the effective value, and then to the interval webbings proportional to the rms value of the measured voltage, and filled into these intervals of fixed frequency pulses.