SU849092A1 - Digital frequency meter - Google Patents

Description

(54) DIGITAL FREQUENCY

I

The invention relates to measurement technology and can be applied in measuring systems with frequency sensors.

Digital frequency meters are known in which the frequencies are measured by counting the number of periods of the frequency being measured during the reference time interval 1.

The disadvantage of these frequency meters is low speed in the low frequency region. .

The closest in technical essence is the frequency), which contains a series frequency generator, an element AND, a pulse counter connected in series a second generator, a second element AND, a controlled divider, other inputs connected to the OUTPUT M of the first counter, and a second counter pulses, the input of which is connected to the input of the controlled divider, and the output to the input of the control unit, the first and second output of the last are connected respectively to the second inputs of the first and second elements And, the third Meters withstand {2).

A disadvantage of the known frequency meter is that the measurement error increases with an increase in the measured frequency, and this limits the measurement range on the high frequency side.

This disadvantage is due to the fact that the degree of filling of the first counter decreases with increasing Frequency, while the counting error is equal to one unit, remains unchanged, since the error results

The 10 meter measurements stored in this meter will increase with increasing frequency. Consequently, the final measurement result, which is obtained by

ts is the invoice number recorded in the first counter.

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

Set} enna goal is achieved by the fact that

X digital frequency meter, containing a series-connected reference frequency generator, the first And element and the first counter, the Tlts generator connected in series, the second And element and controlled, the divider, the code inputs of which are connected to the output of the first counter, the second counter, whose input is connected to the control input delggegel, and the output to the first input of the control unit, the first and second outputs of which are connected to the second inputs of the first and second elements, respectively, and the third counter, additionally in The controllable divider, counter, trigger and two elements are And, whose outputs are connected respectively to the input of an additional controlled divider and counter whose outputs are connected to the code inputs of the additional sent divider, the input of which is connected to the input of the third counter, the first input of the first additional item and connected to. the trigger output, nqpvy and second inputs of which are connected respectively to the outputs of the main and additional controlled dividers, the output of the first counter is connected to the second input of the control unit, the first output of which is connected to the first input of the second additional element And, the second input of which is connected to the third input of the control unit and the input bus, and the second input of the first additional element I is connected to the output of the pulse generator.

The drawing shows a block diagram of the device.

The digital frequency meter contains 1-pulse counters, a main controlled frequency divider 5, an additional controlled frequency divider 6, a reference frequency generator 7 and an imguls generator 8, first and second elements 9 to 10, additional elements AND 12, trigger 13 and control unit 14 IN the initial STATE elements And 9-12 are closed, at the output of the trigger .3 - zero potential. 8, when the first pulse of the frequency fx arrives at the output of the block, the unit potential appears in unit, the element 9 and the additional element 32 are opened. Counter 1 counts the reference frequency pulses from the generator 7, and counter 4 - shifts measured frequency fx. After the number of pulses K arrives in counter 1 (where K is a constant number smaller than the capacitance of the counter), a signal appears at its output, which is fed to the input of control unit 14. As a result, the control unit 14 at the time of the occurrence of the next frequency pulse fx closes: elements 9 and an additional element 12. To this, the pulse counter 1 receives NI n-Tx-f3T pulses fjTt and counter 4 - is the frequency of fx, where

TX is the period of the measured signal; 1et - the frequency of the generator 7; n is a number from the row 1,2. Next, the signals from output 2. of control block 14 open element 10. The pulses from generator 8 begin to arrive at the input of an utphrallized frequency divider 5 and counter 3. The division ratio of the controlled voltage S is equal to the number NI recorded in counter 1. After the arrival of the controlled, splitter 5 Nj pulses, a signal appears at its output, which sets the trigger 13 to the state 1. The trigger 13 opens an additional AND element and the pulses from the generator 8 also begin to flow to the input of the controlled divider 6 and input counter 2. Ko ffitsient dividing controllable divider 6 is equal to the number n. After arrival at the input controlled divider 6 n pulses at its output on is a signal that sets the trigger 13 to its original state, and the AND II closed. Thus, by the signal from the output of the controlled divider 5, the trigger 13 is set to state 1 and by the signal of the controlled divider 6 to the state O. After entering the counter 3, it is set; A constant number of pulses Ng on the signal from its output, the control unit closes the element AND 10. Next, the signal from the output of the divider 6 trigger 13 is set to the state O and the additional element 11 is closed. This is where the conversion process ends. The number of pulses received in counter 2 is equal to

NONO

Nf

n-Tx- fl

Tet

Since NO and far are constant values, the number Nf is proportional to the measured frequency fx. In the proposed device, the counter 1 records the result of measuring the duration of n periods, where n is an integer, depending on the frequency fx

i) f, i.e. "|

/ at FROM

9T

and the magnitude

- const et

at

Consequently, the error of: discreteness, is equal to -r- ii prn measurement. the values of n TX, not the equivalent of fx. Inverting the result of measuring the value of n TX increases the error of maximum. pt at „

the value of which | avnoe (

Claims (2)

IF. also does not depend on fy. Multiplication by the value of n does not cause an additional error. Thus, the measurement error in the proposed device practically does not depend on fx, which allows expanding the frequency measurement range. DETAILED DESCRIPTION OF THE INVENTION A digital frequency meter containing a successively connected reference frequency generator, a first element AND and a first counter are connected in series to a pulse generator, a second: H and A and a controlled divider, the code inputs of which are connected to the outputs of the first counter, a second counter whose input is connected to the input controlled divider, and the output to the first input of the control unit, the first and stopOH inputs of which are connected to the second inputs of the first and second And elements, respectively, and the third counter, is different teM that, in order to expand the measurement range, it additionally contains a controllable divider, counter, trigger, and two inputs, the outputs of which are connected respectively to the input of an additional controllable divider and counter whose outputs are connected to code inputs of the additional control divisible divider, the input of which is connected to the input of the third counter, the first input of the first additional element I is connected to the output of the power supply, the first and second inputs of which are connected respectively to the outputs of the main and complement The first counter is connected to the second input of the first module, the first output of which is connected to the first input of the second additional element And, the second input of which is connected to the third control unit and the input bus, and the second input of the additional element And connected to you go genfagora pulses. Sources of information accepted in the introduction at the conclusion 1. Ermolov R. S; Numeric frequency meters. M., Erga, 1972. 2. Electronics, 1976 N 5, p. 55 fig. 2