SU1019355A1 - Phase shift measuring method - Google Patents

Description

The invention relates to electrical measuring equipment and can be used in the development of phase meters.

A known method for measuring phase shifts is based on an intermediate conversion of a phase shift to a constant voltage by averaging rectangular pulses of constant amplitude and duration,. equal to the time interval proportional to the phase shift f1 3

The disadvantage of this method is dependence; the measurement result from the amplitude of rectangular pulses, which limits its accuracy.

The closest in technical essence and the achieved result to the invention is a method of measuring the phase shift, based on the main and additional integration of the input signal, the beginning of the additional integration is fixed in time, and the end of the additional integration is the carrier time coordinate 23.

Nedos, such a method is as follows. Firstly, it is inherently not high enough due to the need to measure the signal amplitude and the presence of two integration operations. This non-wealth is especially noticeable in the low and infra-low frequencies. The errors resulting from this are then not compensated either. Secondly, the measurement result depends on the frequency of the input signal, which complicates both the measurement process and additional error due to frequency measurement or frequency instability, if it is considered fixed.

The aim of the invention is to improve the measurement accuracy and eliminate the dependence of the measurement result on the frequency of the input signal.

This goal is achieved by the fact that, according to the method of measuring the phase shift based on integrating the input signal, two time intervals are formed, one between the zero transitions of the reference signal and the measured signal through the maximum, and the second between the reference and measured signals the maxima, during each of the time intervals, strobe the measured signal and thereby form two piecewise harmonic signals, measure the average values of these signals and with respect to The desired values are the phase shift being sought.

Fig; 1 shows time diagrams explaining the proposed method; in fig. 2 - block diagram of the device that implements the method.

Let it be necessary to measure the phase shift between two sinusoidal voltages (Fig. 1о |), which are described by the expressions and:, UjTi sinuA

U2 UfT, sin (wt -CH) (1) where H is the measured phase shift; and - voltage amplitude (for

simplifying the recording, it is assumed to be the same for both signals (since the final result does not change from this).

From one of these signals, suppose the signals Ug form two piecewise harmonic signals (Fig, 1.5, b) described by the expressions U2tf (u) t-4).

at 2ЛК-f (+), where К 0,1,2 ...; , 2C, with the other values of the OA;

29

at 2J / K + 7r / 24wt g (+ tf); (2

   F remaining ctit values. Determine the average value of each of these signals W + H (u) t - H) a (IL)

and „2fc

about osw

(3)

jr / 2-t-if

S

one

(wt - f) ta (ujt)

2JT

USH.e} pH

(M

 23G

If we take the ratio of average values, we get

U25

(five)

 tg

U2C

4 arctg f. .

where t2C

Thus, the phase shift can indeed be determined by the ratio of constant voltages proportional to the average values of the piecewise harmonic signals. 3/101 As follows from the above cases, the error of the proposed method practically does not depend on voltage instability. In addition, when implementing the proposed method, there is generally no need to form square impulses, which greatly simplifies the measurement process, and ultimately, its implementation. 8 the device, the implementation of the proposed method includes the keys 1 and 2, the time frame 3, the integrators k and 5, the arithmetic unit 6 and the indicator 7 The voltage Uf. (T) is fed to the keys 1 and 2 and on the time interval 3, on which voltage U (t) is also supplied. The shaper 3 highlights the moments of the voltage transition U; (t) through zero and maximum, and 5 voltages Uy (t) through a maximum and forms control signals, the duration of which is determined by lowering (2). Keys 1 and 2 are opened with these signals, and as a result, piecewise-harmonic signals are output at their outputs to integrators 4 and 5. At the outputs of the integrators, Ojs and 02c signals are generated and fed to arithmetic unit 6, where the phase shift is determined. Thus, the proposed set of operations on the inputs and signals in the proposed method eliminates the measurement error due to the uncertainty of the amplitudes of the input signals, as well as eliminates the frequency measurement deletion.

Claims (1)

METHOD OF PHASE SHIFT MEASUREMENT, based on the integration of the input signal, characterized in that, in order to increase the accuracy and eliminate the dependence of the measurement result on the frequency of the input signal, two time intervals ^ are formed, one between the transitions of the reference signal through zero and the measured signal through maximum, and ... second - between the transitions of the reference and measured signals through the same maxima, the measured signal is gated during each of the time intervals, thereby forming two piecewise harmonic signals, the average values of these signals are measured, and the desired phase shift is found from the average values.