SU744997A2 - Frequency counter - Google Patents

Description

(54) FREQUENCY COUNTER

The invention relates to a pulse technique and can be used in electrical measuring instruments, which are valuable for measuring frequency, are continuous pulse-modulated and frequency-controlled signals. On the main auth, sv. No. 41O561 is known a device comprising a reference oscillator, electronic keys, a time interval driver consisting of a frequency divider and a trigger, a decade counter and electronic keys Su. A disadvantage of the known device is the high measurement error due to the discreteness of the measured signal. The whole invention is to improve the accuracy of the measured. This goal is achieved by the fact that a frequency counter containing a series-connected pulse generator, the first key and shaper of the interval, the output of which is connected to the control input of the second key, to the signal input of which the output of the third key is connected, the control inputs of the first and The third keys are combined, the output of the second key is connected to the input of the decade counter, three keys are additionally introduced, the signal input of each of which is connected to the inverse output ss of the corresponding primary key The main control keys are combined with the control inputs of the corresponding control keys, the outputs of which are connected respectively to the inputs of the first main key, the driver of the time interval and the decade counter. FIG. 1 is a block diagram of a frequency counter; FIGS. 2-4 are time diagrams of cases of possible frequency counter operations. The frequency counter contains a generator of 1 pulses, the main electronic switches 2-4, the driver 5 time inter-. shaft, consisting of frequency divider 6 and trigger 7, decade counter 8, additional electronic keys 9-11.

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: The counter works as follows. Consider the formation of a time interval when the duration of the envelope of the LM pulses is multiple to the period of the reference generator, but the beginning of the AM signal pulse does not coincide with the beginning of the pulse of the reference generator (Fig. 2 a, b, c, d, d). As can be seen from the timing diagram {FIG. 4, d) after passing an additional

of key 9, the duration of the time trigger will be equal to 11 periods of the reference oscillator, as well as for the ideal case, when the duration of an AM or FM envelope pulse is a multiple of the period of the isisable signal and the beginning of the signal envelope pulse coincides with the beginning of the AM signal. As can be seen from the timing diagram in FIG. 3, the number of pulses at the output of key 3 in each packet will be equal, i.e. the number of pulses accurately determined by the pulse AM. However, such a coincidence is extremely rare.

When the duration of the AM envelope is a multiple of the period of the measured signal, But the beginning of the pulse of the signal and the pulse of the AM envelope do not coincide. As a view of the timing diagram of FIG. 3 (d, s, i), the number of pulses at the output of the key 3 Sfig. 2) in this case will be equal to () - (5 + 1), those. per pulse more than the number of pulses, determined by the pulse duration of the AM signal envelope.

When multiplying in the key 4 of this number of pulses with a pulse of the time interval (Fig. 3k), 14 pulses fall to the input of counter 8, i.e. 3 pulses more than the ideal case (fig.Zp),

Consider the signal passing through the keys 3, 1О and 4, 11 of FIG. 1 for the case when the duration of the pulse envelope of an LM or FM signal is a multiple of the period of the measured signal, but the beginning of the pulse of the envelope does not coincide with the beginning of the signal.

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As can be seen from the timing diagram of Fig. 4, in the case of repeated multiplication in the key 3 of an already inverted number (/ + 1) of pulses with the same pulse (Fig. 46)

The envelope of an AM or FM signal is obtained from P 5 pulses (FIG. 4, C).

When multiplying these pulses in key 4 and 11 (Fig. 1) with a pulse of the time interval (Fig. 4 d) at the input

the counter will be 11 pulses (fig. 4, k), as in the ideal case.

Thus, the introduction of additional keys eliminates the error due to the measurement discreteness.

The proposed frequency counter circuit can be used to measure the frequency of continuous pulse-modulated and frequency-manipulated signals and does not require synchronization of the onset of the AM envelope pulses of the AM signal and the pulses of the time interval with the beginning of the measured signal.

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Claims (1)

Invention Formula Frequency counter aut. St. No. 410561 characterized in that, in order to improve the measurement accuracy, three keys are additionally introduced in it, the sipnal input of each of which is connected to the inverse output of the corresponding primary key, the control inputs of the main keys are combined with the control inputs of the corresponding additional keys, the outputs of which are connected respectively, to the inputs of the first primary key, the time maker, and the decade counter. Sources of information taken into account in the examination 1. Copyright Certificate of the USSR № 410561, cl. H 03 K 23/02. 1971.