SU1075184A1 - Phase meter for low and infra-low frequencies - Google Patents

Abstract

PHASOMETER LOW AND INFRASTRUCTURE FREQUENCIES, containing a series-connected generator / key, counter and display unit, the first and second drivers connected to the corresponding key inputs, as well as the first and second terminals for connecting the measured and reference signals / different - in that in order to expand the frequency range and shorten the measurement time, the third and fourth formers are entered into it, the inputs of which are connected to the first and second terminals, respectively, the first and second multipliers that control the cat inputs respectively, the adder, the inputs of which are connected to the outputs of the multipliers, and the output - to the input of the second generator, a frequency divider, the input of which is connected to the generator output, a bandpass filter, the input i of which is connected to the frequency divider, and with inputs (L of the first imager and the reference input of the second multiplier, phase shifter, the input of which is connected to the output of the band-pass filter, and the output with the reference input of the first cleaver and the input of the first forming body. eo 4

Description

The invention relates to a radio metering technique and can be used to measure phase shifts of harmonic signals in determining phase characteristics.

A digital frequency conversion phase meter is known for measuring high frequencies from about 1 to 150 MHz. In a known phase meter, the phase shift is shifted to a low frequency (fixed ij, - f ,; -if In view of the frequency change of the signal f over a wide range, the heterodyne frequency tp must also be tuned over a wide range. The fixed frequency values are chosen so that the numerical result of quantization of time intervals, proportional to the phase shifts at a given T (c, -j-, was numerically equal to the value of the desired phase shift in degrees l.

A disadvantage of the known device is the inability to measure the phase shift in the low and infra-low frequency range, since transferring the measurement to a lower frequency (e.g., 0 Hz) results in a large measurement time, and if the frequencies of the measured phase shifts are transferred to high frequency, it is difficult to separate the sum of i, (- ь) and the difference (ix-irV intermediate frequencies, so for example at x 0.01 Hz, and if - - 10 kHz cyMiia will be 100000.01 Hz). and the difference is 9999, 99 Hz, which, when measured, will introduce a large error, and changing the frequency of the local oscillator when changing the measurement frequency leads to inconvenience in the work and the complexity of the design.

The closest to the invention to the technical essence is a phase meter containing a series-connected generator, a key, a counter and a display unit, the first and second drivers connected to the corresponding key inputs, as well as the first and second terminals for connecting the measured and reference signals 2. Time phase shift measurements vary with the duration of the period of the studied signals. If the time between two characteristic points corresponding to zero crossing of instantaneous values of voltages U (and I 2 is calculated by the pulse rate, and one pulse corresponds to one period (time interval) of the sample generator, then the measured shift az is determined; -.

 Nor qi uNuTr co -360 J-7; .

where CO is the circular frequency,

Tr - the period of oscillation of the reference

generator;

Nq is the number of counted pulses

i is the frequency at which the measurements are made. Those. In this case, it is necessary to know the frequency of the investigated signals, for which the frequency of the investigated signal is measured by a frequency meter, which leads to an increase in the measurement time. Since the frequency of the counting pulse generator is constant, when measuring phase shifts over a wide frequency range, the number of pulses arriving is different for the same phase angle for different frequencies. In addition, the capacity of the counter. must be very large, for example, as the frequency changes from up to 100 Hz, the number of pulses for the same phase angle changes by four orders of magnitude, i.e. a large capacity counter is needed here, which causes certain technical difficulties. The error in measuring phase shifts is uneven. It is very small, approximately 0, 5, in the frequency range up to 10 Hz, in the frequency range up to 300 Hz - approximately 1.5. With an increase in the frequency of input signals above 300 Hz, the error increases, and the frequency of 500 Hz reaches bB. Measurements with such a phase meter are not recommended.

The disadvantages of this phase meter are the limitation of the frequency range due to a significant increase in measurement error and a long phase measurement time, since it is first necessary to measure the frequency of the signal under study, and then calculate the measured phase shift angle using the formula.

The purpose of the invention is to expand the frequency range and reduce the measurement time.

The goal is achieved by the fact that a phase meter with low and infra-low frequencies, containing a series-connected generator, a key, a counter and a display unit, the first and second drivers connected to the corresponding key inputs, as well as the first and second terminals for connecting the measured and reference signals, are entered the third fourth shapers, the inputs of which are connected to the first and second terminals, respectively, the first and second multipliers, the control inputs of which are connected to the outputs of the third fourth shapers, respectively ,. an adder, the inputs of which are connected to the outputs of the multipliers, and the output.- to the input of the second driver, a frequency divider, the input of which is connected to the generator output, a band-pass filter whose input is connected to the frequency divider, and the output to the inputs of the first driver and support of the second multiplier , the phase shifter, the drive of which is connected to the output of the band-pass filter, and the output - to the reference input of the first multiplier and the input of the first shaper. . .

The drawing shows the block diagram of the device ..

The phase meter contains the first and second terminals 1 and 2 for connecting the measurement signal and the reference signal, the third and fourth drivers 3 and 4, which form signals of the form Uj cosfx X ifl x first and second multipliers 5 and b, generator 7, frequency divider 8, band-pass filter 9, phase shifter 10 on 90 adder 11, first and second drivers 12 and 13 (for controlling the operation of the key), key 14, pulse counter 15, display unit 16.

The first terminal 1 is connected to the first inputs of the third and fourth drivers 3 and 4, the second inputs of which are connected to the second terminal 2, and the outputs through the first and second multipliers 5 and b are connected to the inputs of the adder 11. The generator 7 is connected to the key 14 and through a serially connected frequency divider 8, a band-pass filter 9 and a phase shifter 10 with a first multiplier 5. The output of a bandpass filter is connected by a coping input of a multiplier 6, an output of the phase shifter 10 through the first driver 12, and an output of the accumulator 11 through the second form Vatel 13 are connected to key input 14 the output of which through the counter 15 with the block 16 soednen indication. . Phase meter works as follows.

: The measured signal of the type Ux sin {(ot-t |, is fed to the first terminal 1, from where it goes to the first inputs of drivers 3 and 4. The reference signal of the form UoSitiwt is fed to the second terminal from where it goes to the second inputs of drivers 3 and 4.

At the output of the imaging unit 3, a sig "al of type 11" (CDS C1x

At the output of the imaging unit 4, a signal of the form n p tf x is formed. The voltage of the signals of the types U iiUy.ein Cf is supplied respectively to the control inputs of the first and second multipliers 5 and b. The generator 7 generates pulses that arrive at the input of the divider 8 frequency and key 14. From the output of the divider 8 frequency pulses of a frequency equal to

- ,,,,

-3.6.10 where gr - generator frequency 7,

P is a positive integer, whose value is chosen from the required accuracy

and resolution of phase meter and q 2.. The band-pass filter 9 generates a harmonic signal with a frequency f. Of a smaller frequency of the generator 7 P in 3.6 u. The voltage of the form UQsinflt, where Si is the circular frequency, is 57 20f, from the output of the filter 9 is applied to the reference input of the second multiplier b and to the input of the phase shifter 10 (90 °) at the output of which the voltage is UoCosSft

The voltage of the type OC b is fed to the input of the first multiplier 5. The voltage at the output of the multiplier 5 is

8biX5-4Cos x UoCOSSlt y, (5ll-4,

cosCsit + c,).

(2)

The output voltage of multiplier 6 is

, 8biX6 Jx i M xUo5in U lJoUxLco5 (, y-cosiSlt + t,) -. (3)

At adder 11, the form voltage (2) is added to the form voltage (3).

At the output of the sug-chator 11, the voltage is

Bbix, rUxUoCOB (lt-q,). (four)

Thus, the measured phase shift (y) (transferred to the reference frequency i formed by the band-pass filter 9.

The first and second formers 12 and 13 form, from harmonic signals of the UocosSZt and ioso5 types (), the pulses controlling the operation of the key 14. The voltage of the first driver 12 opens the key 14, and the voltage of the second driver 13 closes the key 14.

The number of pulses counted by the counter 15 during the opening time of the key 14 is proportional to the measured phase shift.

The pulses from the first driver 12 unlock the key when the voltage across the cable vanishes, i.e. with SVi, hence the time t (opening the key 14 is defined as

G1G

C5)

The shapers of the second driver 13 close the key 14 when a voltage of the form Ux 5 n passes (wt - (|; () through zero, i.e. when Jit - CCx -, hence the closing m tj is used - the key 14 is defined as

(6J

t., - fi The time during which the key 14 is open is determined as 2tft (t During the time ui, through key 14 on the account CH1-1K 15, N pulses will pass in, the number of which is determined by the following ф | S) where Tj. Is the period of the generator pulses 7,,.. Substituting (7) into (8;) is obtained. -.) And since the ratio F and i Fr 7 is 3.6.10, the measurement result on the display unit 16 is fixed in degrees (n) -CH), with n 2, we get; "C" Thus, compared with E, the actual measurement time was reduced due to direct C) measurement of the measured phase shift and no need to preliminarily measure the frequency of the signal under study. The increase in roscopicity 11 is due to the fact that at any measured frequency the phase shift at this frequency is transferred to a fixed reference frequency and at the same angle of phase shift at different measured frequencies the number of counting pulses will be the same, i.e. limits the frequency range, as in the base unit, and has an optimal value calculated on the number of pulses for maximum phase shift. Depending on the accuracy required, this optimal value can be chosen from the following number of numbers; 360, 3600 or 36000s. The frequency range of the proposed phase meter depends on the types of operational amplifiers used in the phase meter units and is approximately 0-100000 Hz. The error of the measured phase shifts in this phase meter is mainly determined by analog multipliers. Considering the fact that that one of the factors is a constant component, and the frequency of the reference oscillator is small, for example, 1 kHz, and the input signal levels do not exceed + 2V, the multiplication error is no more than 0.1%, which gives the maximum error and Merényi 2,5 °, use of more precise multipliers, for example based on multiplying ILP, allows to reduce the measurement error to 0.8%.

Claims (1)

LOW AND INFRANIZED FREQUENCY PHASOMETER, comprising a series-connected generator, a key, a counter and an indication unit, the first 'and second drivers, connected to the corresponding key inputs, as well as the first and second terminals for connecting the measured and reference signals, characterized in that, in order to expand the frequency range and reduce the measurement time, the third and fourth shapers are introduced into it, the inputs of which are connected to the first and second terminals, respectively, the first and second multipliers, the control inputs of which are combined with the outputs of the third and fourth shapers, respectively, an adder whose inputs are connected to the outputs of the multipliers, and the output is connected to the input of the second shaper, the frequency divider, the input of which is connected to the output of the generator, a band-pass filter, the input of which is connected to the frequency divider, and the output to the inputs the first driver and the reference input of the second multiplier, a phase shifter, the input of which is connected to the output of the bandpass filter, and the output - with the reference input of the first multiplier and the input of the first driver. SU „1075184