SU1659894A1 - Device for comparing frequencies by a standard - Google Patents

Abstract

The invention can be used in digital measuring devices and control systems. The aim of the invention is to improve the accuracy. The purpose of the invention is achieved by introducing into the device to reduce the frequencies of the D-flip-flop 9, the one-oscillator and the counters. In addition, the device contains drivers 2, 6, keys 3, 7. counters 4, 8, and a counting trigger. An increase in the measurement accuracy is achieved by eliminating the uncertainty of the boundaries of the accumulation time intervals by counters 4, 8, the values of which are proportional to the input reference and measured frequencies. 2 Il.

Description

The invention relates to a pulse technique and can be used in digital measuring devices and control systems.

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

FIG. 1 and 2 shows a functional diagram of the device for frequency comparison.

The device contains a bus 1 reference frequency, the first driver 2, the key 3 and the counter 4, the bus 5 measured frequency, the second driver 6, the key 7 and the counter 8, D-flip-flop 9. the third counter 10, the bus 11 control, the first output bus 12 , the fourth counter 13, the counting trigger 14, the one-shot 15, the second output bus 16.

Bus 1 of the reference frequency and bus 5 of the measured frequency are connected respectively to the inputs of the first 2 and second 6 drivers, the outputs of which are connected respectively to the first inputs of the first 3

and the second 7 keys, the outputs of which are connected respectively to the counting inputs of the first 4 and second 8 meters, the bit outputs of which are connected respectively to the first 12 and second 16 output buses. The outputs of the first 3 and second 7 keys are connected respectively to the synchronous input and to the information input of the D-flip-flop 9, the reset input and inverse outputs of which are connected to the enable input of the third counter 10, the output of which is connected to the input of the D-flip-flop 9, the direct output of which is connected to the counting input of the fourth counter 13, the output of which is connected to the second inputs of the first 3 and second 7 keys and to the counting input of the counting trigger 14, the output of which is connected to the start input of the one-shot 15, the output of which is connected to the reset inputs 4, the second 8 and the third 10 counters and to the installation input of the fourth counter 13. The counting input of the third counter 10 is connected to the output of the first key 3. Control bus 11

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connected to the installation inputs of the counting trigger 14 and the one-shot 15. In this case, the counter 13, the trigger 14 and the one-shot 15 perform the function of the control unit 17.

The device works as follows.

In the initial state, the counters are 4,8,10. and the D flip-flop 9 is in the zero state. The counter 13 is in the first of its three states, characterized by a zero output signal covering the keys 3, 7.

A pulse arriving at chic 11 sets the trigger 14 to a single state and causes a pulse to form at the one-shot 15 output. The one-shot 15 output pulse confirms the initial state of the counters 4, 8. 10 and transfers the counter 13 to the next state characterized by a single output signal opening keys 3, 7.

The pulses of the reference and measured frequencies begin to be counted, respectively, in counters 4 and 8, which switch in the general case non-simultaneously.

Part of the pulses of the reference and measured frequencies due to the inequality of the magnitudes of the latter overlap in time, forming the so-called burst of coincidence pulses (in the device are not physically present).

At the moment of the first coincidence in time of the pulse of the reference frequency with the pulse of the measured frequency, the D-flip-flop 9 is triggered, switching to one state and blocking in this state with a signal from its inverse output. The signal from the direct output of the D-flip-flop 9 causes the transition of the counter 13 to the next state characterized by a single output signal holding the keys 3, 7 in the open state.

D-flip-flop 9 remains in the locked state, allowing the counter 10 to operate from the reference frequency pulses. Upon completion of the cycle of operation of the counter 10, the transfer pulse of the latter sets the D-trigger to its initial state. The duration of the specified cycle is chosen so that the return of the 6-flip-flop 9 to the initial state occurs between the bursts of coincidence pulses in the entire range of ratios of the input frequencies of the device.

With the beginning of the next batch of coincidence pulses, these processes are repeated, with the result that a zero potential is established at the output of the counter 13, which sets the counting trigger to the zero state. In this case, the one-shot 15 is started, the output impulse of which all the counters of the device set to their original state, but now at the exact moment of coincidence of the fronts of the input pulses of keys 3 and 7. Thus ends the first cycle of operation of the device.

Then the second cycle of operation of the device begins, the processes in which occur as in the first cycle. During this cycle, codes 4 and 8 accumulate codes proportional to the values of the reference and measured frequencies. These codes at the end of the second cycle are the result of the operation of the device. At the same time, unlike the first measurement cycle, the establishment of a zero potential at the end of the second cycle at the output of the counter 13 causes the counting trigger to become a single state. In this case, the one-shot 15 does not start, the contents accumulated in them are kept in counters 4 and 8, and the counter 13 remains in a state when its output signal has a zero level, which, in combination with a single signal at the output of the counting trigger 14, is a sign termination of the device.

The above is true for the case when the measured frequency is greater than the reference frequency.

It is obvious that when D-trigger 9 is triggered at the moment when the cutoff pulse of the reference frequency coincides with the pulse of the measured frequency, the device operates at the inverse ratio of the values of these frequencies.

This device eliminates the inherent device-prototype uncertainty in the moments of determining the boundaries of the bursts of coincidence pulses, which leads to an increase in measurement accuracy compared to the device-prototype.

Claims (1)

Invention Formula A device for comparing frequencies containing a counting trigger, a reference frequency bus, a measured frequency bus, a first driver, a key, a counter and an output bus, a second driver, a key, a counter and an output bus, the reference and measured frequency buses are connected to the first and second inputs respectively. The second drivers, the outputs of which are connected respectively to the first inputs of the first and second keys, the outputs of which are connected respectively to the counting inputs of the first and second counters, the bit outputs of which are connected respectively for the first and second output tires, which are due to the fact that, in order to improve the measurement accuracy, D-trigger, one-shot. the third and fourth counters and the control bus connected to the installation inputs of the counting trigger and the one-shot, the output of which is connected to the reset inputs of the first, second and third counters and to the installation input of the fourth counter, the counting input of which is connected to the direct output of the D-trigger. the inverse output and reset input of which are connected to the third input enable 0 the counter whose output is connected to the D-flip-flop installation input, the sync input and the information input of which are connected respectively to the outputs of the first and second keys, the second inputs of which are connected to the output of the fourth counter and the counting input of the counting trigger, the output of which is connected to the one-shot trigger input, the counting input The third counter is connected to the output of the first key. Phie.1