RU1837241C - Method of determining phase shift between two harmonic signals - Google Patents

Description

: The invention relates to measuring technique and can be used to create digital phase meters for measuring or controlling the phase angle between harmonic signals, including high-frequency ones.

 The aim of the invention is to increase the accuracy and speed of measurement tftvie

phase shift and expansion of the field of application.

The essence of the invention lies in the fact that the desired time interval proportional to the phase shift is measured as the time interval determined by the number of quantization intervals of the studied signals between the nearest values of the first and second signals after changing their sign and refined by the measured modules of the values quantized in time signals immediately before and after changing their signs. Moreover, as shown below, to ensure similar accuracy, the quantization frequency of the signals is two orders of magnitude lower than the reference frequency fo. In addition, the phase shift range is determined from the sequence of changes in the signs of the first and second signals: from 0 to 180 ° or from 180 to 360 °. To implement the method, current and previous samples of the signals are stored and the signs of these samples are compared. If the characters are equal, information about previous readings is replaced with information about current readings, etc. When you change the sign of the current count of the first signal, a pair of corresponding samples of this signal and the moment of the current count are fixed. Next, a pair of samples of the second signal having different signs and the moment of the corresponding current sample are recorded, the first in time after changing the sign of the first signal. The obtained information, after determining the modules of the fixed signal values, is sufficient to determine, with any a priori specified accuracy, the time interval tytx between the moments of transition of the signals through the zero level and, accordingly, the phase angle

(trtx); j60. (nx +

t

I) L + Ј (1 +

lYil - | Y2I IY2I + IY2 |

) n l A, h iXil -IX21 L1 -nxA-j (1+ | Yil + | Y2l} 1

 360An ... 1 f lYil - | Y2 | T l 2l | Yi + | Y2 |

| Xil - | X2I IXil + | X2 |

)) where T is the period of oscillations of harmonic signals; .

A quantization interval;

nx is the number of quantization intervals (from the start of the measurement) to the moment of the fixed current count of the first signal;

I is the number of quantization intervals between the fixed current signal samples.

The fixed sequence of changing the signs of the first and second signals (from + to - or vice versa) and nslgnY are compared. If the sequences are the same, then the phase shift is in the range up to 180 °, if

different, then in the range from 180 to 360 °. In this case, 180 ° is added to the cn measurement obtained in accordance with (1).

is formalized as follows:

$ extra

: 18001signXAnslgnY V nsignX AnsignY),

(2)

where the sequence of character changes 5 is assigned the value of a logical variable, for example, according to the rule

nslgnU 1 when changing sign from - to +

nslgnU 0 when changing sign to 0 -. .

Figure 1 presents a block diagram of a variant of the device that implements the proposed method; figure 2 - calculated curves illustrating the effectiveness 5 of the proposed method.

Figure 1 marked:

1 - first quantizer (KBI),

2 - second quantizer (Kv2),

3- generator of clock pulses (GTI). 0 4 - measuring and computing unit

(TRS).

The device operates as follows. The inputs X and Y of the devices, which are the first inputs of quantizers 1 and 2, are connected to the first X and second Y harmonic signals, respectively. The input signal source — a sine wave generator — is not, in principle, part of the device, however, information about the current value of the period T of the test frequency oscillations is available and is input through the first input of the IVB A. Generator 3 generates clock pulses, which are fed to the second inputs of quantum5 1 and 2 and to the third input of the IVV 4. Clock pulses are generated through a predetermined interval D, information about the value of which comes from the second output of the GTI to the fourth input of the IVB, Quantized

0 signals X (K) and Y (K) come from quantizers to the second and fifth inputs of the IVB, respectively. In the measuring and computing unit, information on the last two samples of each signal with

5 by replacing at each measure of the previous count with the current. It also determines and compares the signs of the last two samples for each signal. At the moment of quantization, when the sign of the current sample of the signal X for the first time after turning on the device in the measurement mode does not coincide with the sign of the previous sample, this pair of samples and the serial number of the current | bills. Likewise, the operations of fixing the samples of the signal JY are performed, but immediately after the change | the sign of the signal X, and the increment of the sequence number of the current reference | is determined when the sign of the signal is changed with respect to | to the current sample when changing the signal | X sign. After determining the modules | values of the fixed samples in block 4, the basic value of the phase shift of the signals is calculated. In addition, | in block 4, a sequence of changing the signs of the X and Y signals is determined, stored and compared, and for different j sequences of the change of sign, 180 ° is added to the main value of the phase shift.

i The positive effect of using-: neither the proposed method can be evaluated as follows. The only methodological error of the proposed method is the error of the refinement of the interval (time between intersections of the zero level (addition to the number of quantization intervals I), which determines the approximation error | of the sinusoid (in areas adjacent to its zero value) ) | direct line. Since the specified interval is specified on both sides, the total maximum possible error is determined by increasing the maximum error on one side in Y / Graz. In Fig. 2, curve 1 displays the dependence number of samples per period of the test frequency I y | (-t) of the maximum possible approximation error. Note that even with six quantizations per period, the measurement error does not exceed 1.5 °, and for ten - only 0.3 °. Curve 2 shows how many times the quantization frequency should be higher in methods based on digital coding of time intervals proportional to the phase shift with respect to the quantization frequency of the proposed method for the same maximum errors (the maximum error in these methods

ID

appreciated by

j 360). So with

the maximum permissible error of measuring the phase shift of 0.3 ° using the proposed method allows to reduce the quantization frequency by 120 times. Obviously, the indicated effect is all the more significant, the higher the frequency of the test signal and the higher the requirements for

accuracy. The prototype method also allows to increase the accuracy of the reference by a specified m times. However, as noted above, this is associated with a simultaneous increase in time

measurement. It is of interest to compare the methods by the quality criterion determined by the inverse of the product of the measurement time and the corresponding error, i.e.

1

TO

1ism b

For the prototype method at 1ism TT and 15, 360 A -yyyy

Kgshot -

1

prot 360 A.

(3)

For the proposed method, T. Ism T and

i1,7 A, s

((expression for a further 1-4, 4 T

but as a result of approximation of curve 1 of figure 2)

Kizobr

1-4.4 1.7 A

(4)

From a comparison of (3) and (4) it follows that at -t 4.5 the coefficient of Kizobr. Kprot. and

T

at -10 this excess is estimated at

one to two orders of magnitude. Such a significant reduction in the required quantization frequency and improved accuracy allows us to expand the scope of the method and, in particular, to realize digital multi-channel phase meters that measure simultaneously the phase shifts of several harmonic signals.

Thus, the technical advantage of the proposed method is to increase the accuracy and speed associated with the exception of the error of the direct fixation of the moments of passage of the signals of zero level and the ability to accurately measure the time interval between these moments at a very low (countable units)

the number of quantizations of the output signal per oscillation period of the test signal. These advantages make it possible to expand the application of the proposed method for studying high-frequency signals, as well as for simultaneously determining the phase shift of several signals simultaneously.

Claims (1)

SUMMARY OF THE INVENTION A method for determining a phase angle between two harmonic signals, comprising determining transition times by zero level signals, forming a time interval between them, measuring it, measuring the period of input sip 1s and determining a phase shift sign, characterized in that, in order to improve accuracy and speed, sequentially measure and store successively the current and previous values of the first X and second Y signals shifted by the quantization interval D, determine the identity of the signs for each last pair of values, the values of the first signal are recorded before Xi and after X2 the sign changes and the next ones. after them the values of the second signal before YI and after Ya the sign changes, the number I of quantization intervals between the fixed current values is calculated the first and second signals, determine the sequence of changes in the signs of the fixed values, respectively, of the first and second signals, and determine the phase shift between the signals by the formula / 8 T 2 -i f-1x | | + | x2 g nsignx v VnsignXAnsIgn Y, where T is the period of oscillation of harmonic signals; ris.ignU is the sequence of changing the sign of the signal U; moreover, flslgnU 1 when changing the sign with +, FlslgnU 0 when changing the sign with +. Figure 1 / OwO )