SU1465806A1 - Phase shift measuring device - Google Patents

Abstract

The invention relates to measuring instruments: a technique and can be used to control the properties of substances using phase measuring circuits. The invention makes it possible to increase the measurement accuracy by multiplying and transferring the multiplied phase shifts to the frequency of the investigated signals. Consistently form m additional measuring signals by mixing multiplied n1 times the reference signal and n times

Description

one

The invention relates to means for measuring electrical and magnetic quantities and can be used to accurately measure the phase difference of two alternating voltages, in particular to study the properties of substances using phase measurement circuits, one of whose elements is a capacitive, inductive or resistive sensor. go type in robotics.

The purpose of the invention is to increase the accuracy of phase shift measurement by multiplying and transferring the multiplied phase shifts to the frequency of the signals being inspected.

The final measurement result is presented in the sum of the phase shifts measured in each of the measurement channels multiplied by the corresponding coefficient 4). The formula is:

  p-n,

and

(one)

The drawing shows a block diagram of a device for measuring phase shift.

The device for measuring the phase shift contains the first and m additional measuring channels, each of which includes a phase meter 1, a state of the first 2 and the second

five

3 drivers connected in series to trigger 4, the inputs of which are connected to the outputs of drivers 2 and 3, logic element 5 and counter 6, the output of which is the output of phase meter 1, unit 7 for forming the measurement result, the inputs of which are connected to the output of phase meter 1 each channel, the generator of 8 packets of quantizing pulses, consisting of a counting trigger 9, the input connected to the output of the third

shaper 10, the input of which receives the reference signal of the reference signal frequency connected in series to the multiplier 11, amplitude limiter 12 and logic element 13, the second input of which is connected to the forward output of the counting trigger 9, and output to the second input of the logic element AND 5 phase meter 1, the multiplier 14 of the frequency of the reference signal n-1 time, the storage unit 15, the driver 16 correction pulses, the input of which

connected to the inverse output of the counting trigger 9, and the last output Q to the control-input unit 7 forming the measurement result, in each additional measuring channel - serially connected frequency multiplier 17 n times, the mixer

0

five

18, the second input of which is connected to the output of the multiplier 14 of the frequency of the reference signal is n − 1 times, and the band-pass filter 19, the output of which is connected to the input of the second shaper 3 of phase meter i and the input of the multiplier 17 n times of the next channel, the first 20 and second 21 digital comparison elements, each of which is connected by one input to the output of phase meter J, and the other to the corresponding output of storage unit 15, and in each measuring channel, except for the latter, a correction signal generator 22 containing series-connected trigger 23, one input of which is connected to the output of the fourth driver 24, the second input through the delay element 25 to the output of the first driver 26, the input of which is connected to the output of the band-pass filter 19, the logical element AND 27, the second input connected to the output of the logical element And 13 of the generator 8 bursts of quantizing pulses, counter 28, the third digital comparison element 29, the second input of which is connected to the output of the phase meter 1, the first logic element AND 30 and the second logic element And 31, one of the inputs connected to the second output of the third qi the second comparison element 29, the second inputs of the first 30 and second 31 logic elements are connected to the output of the first 20 and second 21 comparison elements of the next channel, the combined third inputs of the first 30 and second 31 logic elements AND are connected to the output fo1) of the equalizer 16 correction pulses, and the outputs - to the control inputs of the registering counter 6 of the phase meter 1, while the input of the correction signal of the first measuring channel is input to the input of the frequency multiplier 17 n times of the first additional channel and to the second input of the former 22 measuring signal, and the input of the first phase meter formirova bodies 1 and 2 to a first input driver 22 in each channel - the reference signal.

The phase shift DF between two periodic signals to be measured can be represented as

& H COtj 27 ftq ,,

(2)

5806

Where

f is the frequency of the analyzed signals; t - time shift between nimio

When using quantizing pulses in a phase meter with a frequency n times the frequency of the signal, expression (1) can be represented as:

 btf,.

nf

- N "n °

(3)

where 2

NO - 7 / P

0

five

phase meter readings; phase quantum;

ULP - unaccounted phase shift, which does not exceed the phase quantum.

Then, an additional measuring signal is formed, by applying to the mixer signals obtained by multiplying the frequency of the measuring signal by n times, and the frequencies of the reference signal by n-1 times. As a result, a signal is obtained whose frequency coincides with the frequency of the reference signal, but the phase difference between the reference and additional measurement signals turns out to be n times larger due to multiplying n times the frequency of the measuring signal and transferring the multiplied phase shift to the original frequency. Then the phase difference between the reference signal and the additional measurement signal, if you do not take into account an integer number of periods:

 27 NO + nuM, V where brackets} mean the subtraction of an integer number of periods, which is cleared and 40 occurs when measured with a phase meter, and the subtracted number of integer periods is NO if О De,: 1.2 «/ п. . ,

This phase shift is recorded by means of a counter with a capacitance n of the second phase meter. If the readings of this counter are equal to N, then

45

nbif

nuCf.

F-.

+ utf. . (four)

When multiplying the frequency of the first additional measuring signal of the previous channel by n times, and the frequency of the reference signal by n -1 times, the phase difference between the reference signal and

The new measuring signal does not take into account whole periods:

, - f m g p

About n / Kfi.-i 2 and.

if a

Similarly, by continuing to generate additional measuring signals t -1 times, you can get the phase shift (the t-th signal relative to the reference signal, taking into account the readings, the counter of the corresponding phase meter

., lj plM „, (5)

and t-th additional measuring signal

(6)

 - nq

WI-H 5

where ЦЦ | „.ц- is the residual phase that is not taken into account in the channel phase meter t. Using successive substitutions and lowering braces,

2 / It, since it is assumed that, hp, obtain a measurable phase shift d., 2 1. V-. ....

 p about G1 l P P

P

2

 f-n-n ..

P

1. +

t-,

 P

2 „1

"M ... 4

P

,,

P

about/

P

t

L ni

ten

-5cf,

(7)

where N (- readings of i-th phase meter; n - frequency multiplication factor;: i 0,1,2, m - number of additional

measuring signals; ...

A & C, Phase Shift Error

Since it was accepted that the value of the unaccounted LO phase is positive and does not exceed 2 u / n, the maximum shift in the measurement of the phase shift

Stf,

1 max

, mi-i

(eight)

The device works as follows.

The input reference 11 (, “and measurement signals in the form of phase-shifted alternating voltages are fed to the inputs of the formers 2 and 3 of the phase meter 1 in the first measuring channel, which form short pulses at the instants of transition of the tested alternating voltages through zero. These pulses are tilting trigger 4, from the output of which a logical element AND 5 receives a pulse whose duration is equal to the times

,

25

- GA658066

the shift between the stresses under study. Simultaneously, the reference signal and fed to the inputs of the multiplier 11

from the frequency of the reference signal n times and turns the counting trigger 9 into one state, opening the logic element I 13o From the output of the multiplier, the variable signal frequency nf (f 10 the frequency of the tested voltages) is fed to the input of the amplitude limiter 12, which converts this signal to rectangular pulses of the same frequency and transmitting them through

15 An open element AND 13 at the second input of the logical element 5, through which the quantizing pulses arrive at the input of the registering counter 6, in which the number of pulses of 20 pulses is placed in the time phase interval between the reference and input measurement signals.

In addition, the reference and measurement signals are fed to the inputs of the frequency multiplier 14 n-1 times and the frequency multiplier n times A multiplication of the frequency of the measuring signal n times occurs and the multiplication is the same time the phase shift. The received signals are fed to a mixer 18, at the output of which a difference frequency signal appears, which is filtered out using a band-pass filter 19o.

35 of filter 19 receive an additional measurement signal, the frequency of which is equal to the frequency of the voltages under study, and the phase shift relative to the reference signal is n times larger

40 Similarly, the phase difference of the received and reference signals is measured with a phase meter 1 of the first additional channel.

I

After the formation of the first additional measuring signal, the second, third, etc. are similarly formed. and finally, the wth signal. The signal is fed to the input of the multiplier 17 of the next channel, the phase shift of the received signal relative to the reference signal is n times the phase shift of the previous signal. The phase difference of the received signals relative to the reference signal is measured in each case using a phase meter K In the counter 6 of each phase meter, the number of pulses NJ is recorded. In this case, 30

50

55

natural pulses N; in each channel, it exceeds p.

With the arrival of the second period of the voltage being investigated, the counting trigger is overturned to zero, closing the And 13 element. The device goes into correction mode. Necessity correction received. the values of N are explained by the fact that in the case / when the number of registered pulses N ;, in the next channel is close to n, then the probability that the number of pulses, N, is increased; registered on this channel, either one less or one more than the true value. To do this, correct the obtained value of M. based on the obtained value of N: the next channel. For this channel each device has a correction signal generator 22 which can change the contents of counter 6 of phase meter 1 in each channel by one. There is no such block in the last channel m. At the end of the correction cycle, the control input of the result generation unit 7 from the last output of the imaging unit 16 correction pulses will receive a pulse allowing reading: corrected N value of all counters 6, Block 7 according to the expression (O calculates the final result With the arrival of a third of its reference signal period, the device again goes into measurement mode, with the arrival of the fourth — into the correction mode of the resultant

tata and todo

five

The correction signal generator 22 operates as follows: the formers 24 and 26 generate short pulses when the reference and the corresponding measuring signals go through zero. The pulse from the output of the former 24 tilts the trigger 23 into one state, and the pulse delayed by the delay element 25 by means of the delay element 25 26 returns it to the zero state. As a result, the duration of the pulse at the output of the trigger 23 is by the time / it, longer than the pulse duration; at the output of the flip-flop 4 of the corresponding phase liter 1 and is. + & t ,,. Brem

ten

-

806 00

bt in each driver 2.2. signal signals. correction is the same

KPK (Q

 x L -, -. - - f

5 PCh L- where K is an integer

O i K | - "

(ten)

about

10 During + t ,, through the logic element AND 27, the number of pulses goes to the counter 28, the code of which is compared in the digital comparison element 29 with the counter code 6 of the phase-15 meter 1. If the counter code 6 is less than the counter code 28, the comparison element 29 gives the voltage level 1 to the input of the element AND 30, if the codes of the contactors 6 and 28 are equal, then the element 20 29 outputs the level 1 to the input of the element AND THEN Depending on what number N ;, the quantizing pulses are recorded in the counter 6 of the following channel, the corresponding voltage level 25 comes to the second input 30 and 31. If N ;, K, then level 1 from the output of element-20 is present at the second input of the element 30, if N, -, p-K, then level 30 1 from the output of element 21 is at the second input of the element I 31; if K N p-K, then on the second inputs of the elements And 30, 31 there is a level O.

, d. The described transformations of the result-flow in the driver 22 of the correction signal during the measuring cycle. During the correction mode the formation of the former 16 is formed at the outputs. Corrective: impulses that in a certain sequence arrive at shaper 22 in each channel. First, a correction pulse is applied to the third input of logic elements AND 30 and 31 shaper 22, the last. his channel, i.e. channel t-1, then channel t-2, etc., and finally, the first measuring channel. Thus, the correction of the result is made, starting with the least significant bits, consistently approaching the older ones. If at the other two inputs of the elements And 30 and 31 there are levels i,. then the correction pulse increases or decreases by one the contents of the counter 6 of the phase meter 1 of the corresponding channel. If at one of the inputs of the elements And 30 and 31 there is a level o, the contents of the counters 6 in each phase meter I remain unchanged.

Thus, it does not impose significant requirements on the resolution of phase meters, which should be about ZlT / n for each channel, the device allows to achieve a significant increase in the resolution of phase shift measurements compared to the known frequency multiplied phase meters by measuring the multiplied phase shifts all the time at the frequency of the measuring signal when using relatively simple measuring equipment,

Claims (3)

Invention Formula 1 o A device for measuring the phase shift, containing the terminals of the reference and measuring signals, hectares of multipliers, n times the frequency of the measuring signal, the first of which is connected to the terminal of the measuring signal, phase meter, driver of control pulses, one of the outputs of which is connected to the block start input forming the measurement result, so that, in order to improve the measurement accuracy, the phase meter contained in it is equipped with the fourth and fifth (correcting) inputs and a multiplier is added to it n-1 times the frequency of the reference signal, the input connected to the reference signal terminal and the output - with the first inputs m of the input frequency mixers, the second inputs of which are connected to the outputs m of the multipliers, n times the frequency of the measuring signal, m bandpass Filters, inputs connected to the outputs of each from m mixers, w additional phase meters m correction signal formers, m pairs of comparison code elements, minders. block, a generator of quantizing pulse trains, the input of which is connected to the reference signal terminal, to which the first inputs m + 1 of phase meters are also connected, the first inputs of m correction signal conditioners, the measuring signal terminal is connected to the second input of the first phase meter and the second input of the first correction signal generator, the outputs from the first to (ml) -ro bandpass filters are connected respectively to the inputs from the second to the tth intelligent g inhabitants at times the frequency of the measuring signal, and also respectively to the second inputs from the second to the tth phase meters and second inputs from the second to the sh-th formers of the correction signals, the output of the second filter is connected to the second input of the m + 1 -ro phase meter, the first output of the generator of quantizing pulses is connected to the third inputs m + l 5 phase meters and m correction signal formers, the first and second outputs of which are connected respectively to the fourth and fifth inputs from the first to the th phase meters, outputs 0 which are connected respectively to the fourth inputs of each of the m correction signal formers, the fifth and sixth inputs of each of which are connected to the outputs of each co5 of the corresponding pair of code comparison elements, the first inputs of each specified pair are connected to the output of each subsequent phase meter, and the second inputs of each pair - respectively, with the first and second outputs of the storage unit, the outputs m + I of phase meters are connected respectively to the (t + 1) th input of the measurement result generator, the second output of the generator of the packs to the quantum boiling pulse shaper connected to the input control pulses, m outputs of which are connected respectively to the seventh input of each of m formation 0 correction signals. 2b A device according to Po1, about tl and the fact that the generator of bundles from quantizing pulses contains serially connected multipliers in n times the frequency of the reference signal, the amplifier-limiter and the element And, the second input of which is connected to the direct output of the trigger, input which through the pulse shaper 0 is connected to the input of the multiplier n times the frequency of the reference signal, which is the input of the said generator, the output of the element I is the first output, and the inverse output of the trigger 5 is the second output of the mentioned generator. 3. The device according to A.1, about tl and h ach e with the fact that the driver 11 1465806 Correction Signals Contained, Successive-Yen with a B ..; RIGGE R connected, formatively, the cdG is connected to the second, m input of the impulse impulse, the trigger, the first lemme I. the fourth input — with element I. counter and element comparing. „“ OM element comparing conen codes, output Less than kotoro- “Li input - with the second input Go is connected to the first "" - "-. f ;; ° Г. I. the sixth entrance - from element I. and output, Equal to the first input of the third element I. “move. „D - with third entrances the driver of the reference pulse, the ip of the third element I. th pulse and the delay line of the Com.