RU1817056C - Device for measuring time interval - Google Patents

Abstract

The invention relates to measuring technique and can be used to measure the time interval. The device for measuring the time interval contains: 1 pulse generator (1), 1 RS-trigger (2), 3 D-triggers (3,4,8), 2 OR elements (7,5), 1 counting trigger (5), 1 pulse counter (9), 1 element And (10), 1 - 10 1 - 3 5 - 6 - 4 - 8 - 10 - 9; 4 - 5 .. 5 ill.

Description

The invention relates to measuring equipment and can be used in automation, computer engineering and instrumentation.

. The purpose of the invention is to simplify the device by reducing the amount of equipment.

Fig. 1 is a functional diagram of a device for measuring a time interval; figure 2-5 - timing diagrams of the operation of the device. ..

The device for measuring the time interval contains a pulse generator 1, RS-trigger 2, D-triggers Z, 4, element 5 OR, counting trigger 6, element 7 OR, D-trigger 8, counter 9 and element 10 I.

The direct output of the generator 1 is connected to the C-input of the trigger 3 and to the first input of the element 10, and the inverse output to the C-inputs of the triggers 4.8. The S-input of trigger 2 is connected to the 11 Start bus, and the R-output to the 12 Stop bus. The output of trigger 2 is connected to the D-inputs of triggers 3, 4. The inputs of element 5 are connected respectively to the inverse output of trigger 4 and to the direct output of trigger 3, and the output is connected to the C-input of trigger 6 AND to the first input of element 7, the output of which is connected to the R-input of trigger 4, the output of the D-trigger 8 is connected to the second input of the element 10, and the D-input is connected to the output of the trigger. The output of element 10 is connected to the counting input of the counter 9, the zeroing input of which is connected to the reset bus 13 and to the S-input of the trigger 6. The output bus 14 of the integer part of the measurement result is connected to the information outputs of the counters 9, and the bus 15 of the fractional part of the measurement result is connected to to the output of trigger b and to the second input of element 7.

The device operates as follows. zom.

Generator 1 generates direct and inverted impulse sequences of the meander type with period r at its outputs. Trigger 2 is in the O state, providing O on the D inputs of triggers 3, 4, which are also set under the influence of their C inputs of the pulse sequence in O, which goes to the D-input of trigger 8. Since the C-input of trigger 8

(L

WITH

00

Xi o o o o

the pulse sequence also arrives, it will also be set to O, closing the element 10 for the pulses of the generator 1. Before measuring the pulse on the bus 13, the counter 9 will be reset to zero, and the trigger b at the S-input will be set to 1.

At the time of the measured Tx interval, a start pulse arrives at bus 12, setting trigger 2 to 1, and at the moment of Tx completion, a stop pulse arrives at bus 11, returning trigger 2 to its initial state. Thus, a strobe pulse is generated at the direct output of trigger 2, the duration of which is equal to the duration Tx. The case where the start and end of the strobe pulse is in the zero state of the forward pulse sequence is illustrated by the timing diagrams of Fig. 2, the start of the strobe pulse is in the region ti-t2, and the end is in the region. It is easy to calculate that the maximum and minimum strobe durations, expressed through a period, are

part of the measurement result is O, then the measurement result will be

 g

(2)

Based on (1) and (2), the measurement error

D 4 t-3.5 t 0.5 t D 4 t -4.5 g -0.5 g I DI 0.5 t

(3)

Fig. 3 illustrates the case where the start of the strobe pulse falls to the zero state of the forward pulse sequence (interval ti ... t2 (and the end to the single state of this pulse sequence (interval t6 .., t). and the minimum value of the measured interval, obviously.

 7-tl 4T Tmin t b - t2 ZT

(4)

 8 -, 5r 1, 5r

(1)

Consider the formation of a measurement result.

With the start of the strobe pulse, D will be set to 1 at the D inputs of triggers 3, 4 and at time ta, under the influence of a 0/1 edge of the direct pulse sequence, trigger 3 will be set to 1 at the C input. Trigger 4 is set to 1 at time ta as a result of exposure to its C input of a 0/1 edge inverse pulse sequence. From time t3, potential 1 comes to the D-input of trigger 8 from the direct output of trigger 4. Therefore, at time ts, trigger 8 is set to 1 similarly to trigger 4, opening pulse element 10. Regarding the direct pulse sequence, 4.8 triggers at the C input are triggered by a 1/0 differential. At the end of the strobe pulse, the D inputs of trigger 3, 4 will be set to O, and at time te trigger 3, and at time tg trigger 4, it will return to its original state. In the interval te ... tg at both inputs of the OR element 5, the potential O and a negative impulse are generated at its output, under the influence of which the trigger b will overturn, becoming in the zero state. Since from the moment tg at the D-input of the trigger. then it returns to the zero state at the moment tn, closing element 10. As can be seen from diagram 8, four counting pulses will arrive at the input of counter 9. Since the bus 15 is fractional

Similarly to the previous case, at time t2, trigger 3, and at time ts, trigger 4 is set to 1, at time tg to 1, trigger 3 is set to 8, opening element 10 for a direct pulse sequence.

After the strobe pulse ends, trigger 4 is first set to O at time t, and trigger t is set to 0 at ta. As you can see from the diagrams at the output of element 5, the logical state (logical 1) does not change during the measurement, and trigger 6 during this time also does not change its initial state. From the moment ty at the D-input of the trigger 8-О, and it returns to the initial state at the moment tg, closing element 10. As can be seen from the diagram, three counting pulses were formed at the output of element 10. Since T is supplied to bus 15, the measurement result will be

 0.5 t 3.5 t

(5)

Based on (4) and (5), the measurement error will be

A, 5t 0.5t D -3.5t-0.5t, 5g

(6)

Figure 4 illustrates the case where the start of the strobe pulse is in the single state (interval t2 ... ta) and the end is in the zero state (interval ty ..ta) of the forward pulse sequence. Here

the maximum and minimum value of the measured interval is t:

 8 - t2 4G Tmin t - t3 3G

(7)

As can be seen, the diagram with the start of the strobe pulse in the single state is set by trigger 4 at the time ta. and trigger 3 - at time t4. And in the interval t3 ... t4, a negative pulse of duration g / 2 is formed at the output of element 5, the differential 0/1 of which will overturn trigger 6 at the C-input at time t4. those. set to O. Trigger 8 will be set to 1 at time t5, opening element 10.

At the end of the strobe, trigger 3 at time ts will be set to O at the C-input. O will be output at the output of element 5. OR will be set at A. At the output of element 7, O will also be set, which will set trigger 4 at the R-input to O. 5 will be set to 1 again, i.e. at the output of element 5, a short negative pulse is generated, the duration of f 5 of which is equal to the sum of the delays of element 7, trigger 4, and element 5 itself. The minimum pulse duration from which the elements (logic elements, triggers, counters, etc.) of this series are reliably triggered (for example, series 155), there must be at least a logical element AND or OR. In this case, we have the duration r5 several times longer than Tz, especially if we take into account that the D-trigger has a delay of 2 tz ... 3 tz. This means that from this pulse a reliable triggering will occur at the C-input of trigger b, which will again be set to 1. Since by the time tg the trigger has 8 O at the D-input, it will be set to O at that moment, closing element 10.

As can be seen from the diagram, at the output of element 10 three counting pulses are formed, and taking into account the single state of trigger b, the measurement result will be

 + 0.5 g 3.5 t

(8)

Based on (7) and (8), the measurement error will be

I D | 0.5t

ABOUT)

5, the start and end of the strobe pulse are in the single state of the forward pulse sequence

 5r Tmln t6-t3 2,5r

(10)

Here, as in the previous case, an impulse is generated in the interval t3 ... t4 at the output of element 5, since first (at time ts) trigger 1 is set to 1, and then (at time to) trigger 3. At time t4 trigger 6 is set to O. Element 10 by trigger 8 opens at the time of dz. At the end of the strobe, trigger 4 first returns (time t). and then trigger 3 (moment te), and trigger b remains in the zero state until the end of measurement. At time tg, trigger 9 also returns to its original state.

As can be seen from the plot, three counting pulses will be formed at the output of element 10, and the measurement result will be

(eleven)

Based on (1) and (11), the measurement error will be

I DI 0.5 t

The measurement error does not exceed 0.5 g and in those cases when the beginning or end of the strobe pulse coincides (almost coincides) with the moments of the change in the logical state of the pulse sequence of the generator 1.

Let the beginning of the strobe occur at time t2, and the end at time t. The duration of the variable interval will be

TX ty-t2 3,5r

(12)

At time t2, the triggering of trigger 3 is probabilistic, i.e. trigger 3 trigger at the time of t.4 is not predictable.

At time t, the triggering of trigger 4 has a probabilistic nature.

If trigger 3 fires at time ta, and trigger 4 at time t fails to fire, then the device operates in accordance with the diagrams of FIG. 2 and the measurement result

fifty

Nu 4G

(thirteen)

If trigger 4 manages to fire at time t, then the device operates in accordance with Fig.Z. The measurement result in this case

Nu 3.5 g (14)

If at time t, 2 trigger 3, and at time t - trigger 4, do not have time to fire, then

the measurement result is generated in accordance with figure 4

5r

(fifteen)

If the trigger 3 at the time ta did not work, and the trigger 4 at the time t manages to fire, then the device operates according to the diagrams of Fig. 5 and the measurement result is

Nu Zg

(sixteen)

Comparing the measured Values (13), (14), (15), (16) with the actual values (12), we see that the measurement error does not exceed ± 0.5 t.

Thus, the proposed device provides the measurement accuracy the same as the prototype device, while it has a smaller amount of equipment - eliminates one element I.

A device for measuring a time interval, comprising a pulse generator, an RS trigger, three D triggers, two OR elements, an AND element, a counting trigger, and a pulse counter, moreover the direct output of the generator is connected to the first input of the And element and the clock input of the first D-flip-flop, and the inverse output is connected to the clock inputs of the second and third D-flip-flops, the direct output of the last of which is connected to the second input of the And element, the output of which is connected to the counting pulse counter input, information outputs of which are the outputs of the integer part of the measurement result and are connected to the output bus of the device, and the zeroing input is connected to

the Reset device input and the S-input of the counting trigger, the direct output of which is the output of the fractional part of the measurement result and is connected to the output bus of the device and to the first input of the first OR element, and the clock input of the counting trigger is connected to the second input of the first OR element and to the output the second OR element, the first input of which is connected to the inverse output of the second D-trigger, and

the second input is to the direct output of the first D-flip-flop, the D-input of which is connected to the D-input of the second D-flip-flop and to the direct output of the RS-flip-flop, the S- and R-inputs of which are connected to the Start and Stop buses, respectively, about t l and t that in that. in order to simplify the device, the direct output and the inverted R-input of the second D-flip-flop are connected respectively to the second input of the third D-flip-flop and to the output of the first OR element.

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tj tz is fy ts

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ts t is t $ tjo ti FIG. I