SU1734034A1 - Frequency meter - Google Patents

Abstract

The invention relates to electroradiation measurements. The aim of the invention is to expand the range of measured frequencies. A device for measuring the frequency contains counters 1 and 2, elements AND 3-5, D-flip-flop 6, pulse generator 8, input 9 and Start bus 10. The addition of an additional D-flip-flop 7 and new connections ensures the formation of a measuring interval equal to the integer number of periods of the lower frequency (input or generator 8). 2 Il.

Description

FIG. one

This invention relates to a measurement technique.

The purpose of the invention is to expand the measurement range.

Figure 1 shows the functional diagram of the device; figure 2 - timing charts of his work.

A device for measuring frequency contains n-bit counters 1.2 elements And 3,4,5, D-flip-flops 6,7, generator 8 pulses, input bus 9 and Start bus 10.

The device works as follows.

With the arrival at the time (Fig. 2) of the pulse on the bus 10, the trigger 6.7 is set to 1, and the counters 1.2 are reset to O. Since the D inputs O, then the triggers 6.7 are set to O - at times ti, t2. From the moment t.2, the output of element I5 is set to 1, opening elements 3.4, and counters 1.2 begin to count the frequency of the generator 8-f0.

Since, at the time of the TZ, the most significant bit of the counter 1 will be set to 1 at the D input of the trigger 7, which at the time t / j at the C input will be set to 1. The output of the I5 element will be set to O and the count will stop

If, then at time t3, the D-input of the trigger 6 is set to 1, and at the time t4 this trigger at the C-input is set to 1, and the counting stops.

In both cases, the measurement interval is equal to an integer number of low frequency periods and the corresponding counter counts the number of these periods without error, and the code of the other counter of the high frequency counting period will have an error of the counting unit, i.e. per unit junior yes

In the first case, when the desired frequency is determined

/ 1 N1 ± 1 tx -

N2

c1.

and similarly in the second case

f

N1

N2 ± 1

fo-1

Since N1mm and N2nrnin 2 t a N2min, the maximum measurement error due to the counting resolution is

 0)

It is obvious that by choosing n sufficiently large, it is possible to ensure a constant permissible measurement error in a wide range of variation of the measured frequency.

0

The range is determined from the following obvious relationships,

If it is necessary that in one fx period there is no overflow of 5 counter 1, i.e.

- 9P - 1 f 1 °

f z Ј.I, Txmm gg

in2 -1

With f0 fx, it is necessary that in one period f о no counter 2 overflow, i.e. Ј (2n-1); fxmaxЈ 1a ()

or in the general form (2n-1) f0 $ fx, ---. .

2n-i

5 Dynamic range D will make

, L (ixmin

that is, (2n-1) times more than the dynamic range of the prototype. Thus, the proposed device provides a significant expansion of the measuring range, and, at the same time, the equipment volume practically does not exceed the prototype device: one D-trigger is introduced, and the two-input element OR and the three-input element OR are NOT excluded.

Claims (1)

Invention Formula 0 A device for measuring the frequency, containing a series-connected pulse generator, a first And element, a first counter, the output of which is the first output of the device, a serially connected second element And, and a second counter, the output of which is the second output of the device, and a third element And and D-flip-flop, the inverse output of which is connected to the first input of the third 0 of its element AND, the input bus and the Start bus are connected respectively to the first input of the second element And and the combined R-inputs of the first and second th 5 counters, the second input of the first element AND is connected to the second input of the second element AND, characterized in that, in order to expand the range of measured frequencies, a second D-trigger is additionally introduced into it, the 0-input of which is connected respectively to the high-level output the first input of the counter and the first input of the second element I, and the S input is combined with the S input of the first D flip-flop and the device Start bus, while the D input and the C input of the first D flip-flop are connected respectively to the higher-order output of the second counter and generator output imp pulses, inverted, clear output of the second D-flip-flop is connected to the second input of the third element I. I G l WITH- L "  C  l CM one  four V v