SU1287095A1 - Method of measuring duration of periodic pulses - Google Patents

Abstract

The method relates to a pulse technique, in particular, to a technique for measuring time intervals. The aim of the invention is to improve the measurement accuracy. The method is as follows. From the sequence of measured rectangular pulses, separate sequences of pointed pulses are formed, corresponding to the front and rear edges of the pulses of the studied signals. The same sequences form a Lusk bode of pulses with a reference frequency close to the frequency of the signals under study. Only fully matched central pulses of coincidence packets are selected by determining the moments of the mutual transition of the leading edges of the pulses of the signals under investigation relative to the leading edges of the reference sequence pulses and the moments of mutual transition of the leading edges of the pulses of these sequences. The time intervals for determining the pulse duration are formed by counting the fully matched central pulses in the coincidence packet and the reference frequency pulses in the interval between the first and second packet. The device that implements this method contains 1 and 2 pulse formers, 3 reference frequency generator, 4, 5, 11, 15, and 16 pointed pulse formers, RS 6, 7, and 1.7 triggers, 8, 9, and 14 triggers with counting input, element 10 matches, elements 4, 13, 18 and 20, counters 19 and 21, microprocessor 22. 3 Il. (L N9 00 O SO eaten

Description

The method relates to a pulse technique, in particular to a technique for measuring time intervals.

The aim of the invention is to improve the measurement accuracy.

Figure 1 shows the block diagram of the device for implementing the method; Fig. 2 shows charts for forming time intervals for determining the duration of periodic pulses; FIG. 3 shows a fragment of the formation of central pulses of a packet.

The essence of the method is as follows.

From the sequence of measured rectangular pulses of duration that follow with the period Ti (fig.2o), separately form the sequence of pointed pulses corresponding to the front (fig.2b) and rear (fig.2) fronts of the pulses of the signals under study. The same sequence of pointed pulses, corresponding to the front and rear edges, are formed from pulses with a duration o of the reference frequency f o close to the frequency f i, 1 / Tz of the signals under investigation (Fig. 2, P).

Then, the leading edge of the coincidence packet of the central pulses is formed, i.e. reference frequency pulses (as a rule), which completely coincide with the pulses of the sequence under study. For this purpose, the logical elements intended for the formation of the leading front of a packet of central pulses fall into sequences of pointed pulses corresponding to the leading edges of the pulses of the test and reference sequences, and the pulses of these sequences are determined by the moment of mutual transition of pointed pulses of one other (Fig. 2x ().

To form the leading edges of the packets of central pulses, the moment of mutual transition of one relative to the other pointed pulses, corresponding to the back edges of the pulses of the test and reference sequences (Fig. 2), is determined. Extended, rectangular pulses of coincidence packets of central pulses form PS pulses before

ABOUT

0

0 5

0 5

him and the rear edges of the packages (figure 2; 1).

If the pulse durations of the signals under study and the reference frequency signal t ,, and their periods / f c and / fo, then in the coincidence process it was possible to distinguish the transition moments of sharp-pointed front pulses relative to each other, it is enough to ensure that the condition and + 2 1Ti-T-oG. (one)

At the same time, in the extreme case, only two coincidence impulses are formed, and practically, when the duration of the pulses used is much longer than the value TQ /, not one pair of coincident pulses is formed, but a burst of pulses. On the other hand, to implement the proposed method, it is also necessary that

and 2 Uy - T., 1 (2) where t-, T «.

In this case, even with the continuous coincidence of the pulses, it is possible to single out the transition moments of both the front and rear edges of the pulses of the studied sequence and the reference frequency relative to each other.

If t, t i3, then in the process of coincidence a series of central pulses (central pulse pulses) is formed, the duration of which corresponds to the duration of the shorter of the participants in the coincidence (i.e., duration o) S and their number in one packet is defined by the following expression

N - and JliiJ L ,, 1%: º ° №o and .04

4-dt - where DT TV, - - fwl / fo f a. ffi fw

Ha FIG. 3 shows a fragment of the formation of the first central pulse of the packet, which illustrates in an unprecedented way the expression dpi Nji obtained above. From the same fragment, the following relation is obvious for determining the pulse duration v,:

„O + (Cc - 1) L T (4) Substitute the value of DT in expression (4), we get

  () (five)

Go In

It is known from the properties of the coincidence method 13 that if the measurement time is taken to be equal to the difference period, often m;

(6)

Thats

As the next packet match matches, then the following relationship between fo and fy

N, f N, f, (7)

where Np and Nj are the number of frequency periods fg and f between the coincidence packets. Taking into account relations (6) and (7), expression (5) is converted to

 o + ();

(eight)

NM fo

Since, for the coincidence method, for the interval Tr, the number of pulses of both frequencies differs by one (the diagrams of Fig. 2), then 1 N - N foTRa the final expression for η will look like

  “:. f

 Г „-1;

The process of measuring the duration of periodic pulses consists in the formation of two time intervals: Tc - the duration of a packet of cent-pulses and T - the period of the following packets of central pulses

measured by the beginning of the packet (Fig. 2 liters) and determining the desired value of i according to the following expression:

+

NH N

T n.

(ten)

where N and N

fc

about

H.

- digital equivalents of known and given values. and fo. Thus, pulses of coincidence packets are used as the boundaries of the obtained time intervals, which are formed directly at the moments of complete coincidence, the pulses of the studied sequence and the pulses of the reference frequency, i.e. at the moments of mutual transition of the fronts of the pulses of the indicated sequences relative to each other. These time intervals T and T are filled with a reference frequency and by the number of periods T "at these intervals and

digital equivalents of N

and nr

determine the value of the pulse duration. In this case, the error of quantization of the time intervals Tc and T by a sequence of impulses of a support of the frequency f (, is absent).

The quantization decay of ng is practically imperceptible, since its value is less than the value of LT.

The device contains (figure 1) the first and second formers 1 and 2 according to

g

ten

870954

the front and rear edges of the studied sequence, the reference frequency generator 3, the third and fourth formers 4 and 5 pointed pulses on the front and rear edges of the reference frequency pulses, the first and second RS-triggers 6 and 7, the first and second triggers 8 and 9 with a clock input , coincidence element 10, fifth pointed pulse shaper 11 on the leading edge, trigger 12, first element 13, third trigger 14 with a counting input, sixth and seventh shaper 15 and 16 pointed edges on the front and rear edges, respectively etstvenno third RS-trigger 17, a second element and the cop 18, the first counter 19, the third

Element I 20, second counter 21, micro 20 processor 22.

15

-

0

The device input bus is connected respectively to the inputs of drivers 1 and 2, to the first S input of trigger 6, to the first R input of trigger 7, I output of the generator 3 is connected respectively to the inputs of drivers 4 and 5, to the first R input of trigger 6, with the first S-input of the trigger 7, with the first inputs of the elements 18 and 20, the output of the imaging unit 1 is connected to the second R-input of the trigger 6, the second S-input of which is connected to the output of the imaging device 4, the output of the imaging unit 2 is connected to the second S -the trigger input 7, the second R-input of which is connected to the output of the driver 5, e inichny output latch 6 is connected to the counting input of the flip-flop 8, a single output

0 which is connected to the first direct input of the trigger 8, the unit output of which is connected to the first direct input of the coincidence element 10, the second inverse input of which is connected

5 with one -1th output of the trigger 9, the counting input of which is connected to the single output of the trigger 7, the output of the coincidence element 10 is connected to the second input of the element AND 20 and the input

0 form1 {rotator 1 1, the output of which is connected to the first input of the element I 13, the second input of which is connected to the single output of the trigger 12, the S-input of which is connected to the Start bus, output of the element And 13 is connected with the input of the trigger 14, single output which is connected respectively to the inputs of the formers 15 and 16, the output of the former 15 is connected to

512

S-input trigger 17, the R-input of which is connected respectively to R-BXO-house of the trigger 12, to the output of the driver 16 and the first input of the microprocessor 22, the second input of which is connected to the output of the counter 19, the input of which is connected to the output of the And 18 element, the second the input of which is connected to the unit output of the trigger 17 and the third input of the element. AND 20, the output of which is connected to the counting input of the counter 21, the output of which is connected to the third input of the microprocessor 22. The device works as follows.

The sequence of measured pulses (Fig. 2a) from the input bus enters the formers of 1 and 2 pointed pulses, respectively, along the front and rear edges of the pulses under study (in the simplest case, these are chains differentiating the original pulses). The generator 3 generates pulses of a given spacing, the frequency of which is followed (f d Spop frequency) is given and close to the frequency f i of the input pulses under study. The pulses from the output of the generator 3 arrive at shapers 4 and 5 of the pointed pulses on the front and rear edges of the reference frequency pulses. From outputs of shapers 1 and 2, 4 and 5

Counting the number of central pulses in the MC package in the device is as follows. Continuous rectangular pulses of duration T, from the output of the trigger 17 are sent to the third input of the element I 20. To the other two inputs of the element

impulses are sent to the information pj -20, envelope pulses are received, the pa- and clock inputs of the flip-flops 6 and /,

ket.a central and fflyuls in exit; the element 10 coincidences and the impulses of the reference frequency from the generator 3. In the counter 21, in this case, the pulse of the pulses is recorded, with this completely

the output of the trigger 6 is formed by a sequence of pulses (Fig.), the leading edge of each of which corresponds to the leading edge of the packet 40 of the central pulses.

From the output of the trigger 7, a sequence of pulses is obtained, the leading edge of each of which corresponds to the falling front of the packet of central pulses (Fig. 2).

Counting triggers 8, 9 and the element 10 matches with one inverse input finally form the packets

ket.a central and fflyuls in exit; the element 10 coincidences and the impulses of the reference frequency from the generator 3. In the counter 21, in this case, the pulse of the pulses is recorded, with this completely

the possibility of recording not all the bundles of central pulses, but its parts when the Start command is sent to the device during the formation of the packet itself is excluded.

The trigger 12 returns to its initial state with a pulse from the driver 16, i.e. on the arrival of the second pulse of the leading edge of the packet. This

central pulses (figure 2 /). Eaten

. „„ - the impulse arrives at the microprocessor of the element 10 coincidence impulses, „t

- „rub //, permitting the input and processing of the corresponding envelope of the packet of central pulses, 11 sharp-pointed impulses arrive at the formatter (g)

radiated N

C and NT- and available codes in accordance with the formula

The one that marks the front of the packet.

At the start command, arriving at the S input of trigger 12, the latter is tilted, allowing passage through

55

Claims (1)

Invention Formula A method for measuring the duration of periodic pulses, based on five 0 5 o element 13 of the pulse of the leading edge of the packet from the imager 11. The first such impulse after the Start command will overturn the trigger 14 with the counting input to the unit state, and the second such impulse will return it to the initial state. At the same, the imagers 15 and 16 separate the first and second impulses from the imaging unit 11 in the form of pointed impulses of the front and rear edges, respectively. These pulses are fed to the information inputs of the trigger 17, which, upon arrival of the pulse from the imaging unit 15, is set to one state, and allows the reference frequency pulses to the counting input of the counter 19 through the And 18 element. The trigger 17 remains in the single state until the R input of the trigger 17 will not receive a pulse from the former 16. Thus, in the counter 19 there will be recorded N pulses of the reference frequency, which determine the period of the packets of central pulses along the beginnings of these packets (N. NV,). Counting the number of central pulses in the MC package in the device is as follows. Continuous rectangular pulses of duration T, from the output of the trigger 17 are sent to the third input of the element I 20. To the other two inputs of the element  pj -20 enters the envelopes, pa- pj -20 enters the envelopes, pa- ket.a central and fflyuls in exit; the element 10 coincidences and the impulses of the reference frequency from the generator 3. In the counter 21, in this case, the pulse of the pulses is recorded, with this completely the possibility of recording not all the bundles of central pulses, but its parts when the Start command is sent to the device during the formation of the packet itself is excluded. The trigger 12 returns to its initial state with a pulse from the driver 16, i.e. on the arrival of the second pulse of the leading edge of the packet. This and NT and available according to the formula 55 Invention Formula A method for measuring the duration of periodic pulses, based on transformations to a low frequency of time intervals that determine the duration of the pulses by comparing in time the sequences of pulses of the studied signals with a reference sequence of pulses and the subsequent time by pulse converting these time intervals, characterized in that, in order to improve the accuracy of the measurement, only completely matched central pulses of coincidence packets by determining the moments of the mutual transition of the leading edges of the pulses of the investigated signals relative to The leading edges of the pulses of the reference sequence and the moments of mutual transition of the leading edges of the pulses of these sequences, and the time intervals for determining the duration of periodic pulses are formed by counting fully matched central pulses in the coincidence packet and pulses of the reference frequency from the beginning of the first packet of central pulses to the beginning of the next followed by the second package .: I I I And 1 one.. Gi