SU898339A1 - Frequency meter - Google Patents

Description

(54) FREQUENCY METER

one

The invention relates to a measurement technique and can be used to digitally measure the frequency of electrical signals in devices operating autonomously with limited power resources, such as field geophysical equipment.

A device for digital frequency measurement is known, based on the counting method 1.

The disadvantage of this device is the need to use highly stable, accurate reference frequency generators, and the temperature control of the generators is necessary to measure the frequency over a wide range of temperatures. Thermostating is associated with a significant consumption of electrical energy, the resources of which are limited in field conditions.

The closest in technical essence to the invention is a frequency meter containing an electronic key, a driver, a pulse counter, a reference frequency generator and a frequency divider, the driver output is connected to the first input of an electronic switch, whose input is connected to the input of a pulse counter, the output of the reference frequency generator is connected to the input of the frequency divider, the output of which is connected to the second input of the electronic key 2.

A disadvantage of the known frequency meter is the high power consumption and low measurement accuracy when measuring over a wide range of temperature variations.

ten

The purpose of the invention is to improve the measurement accuracy and reduce power consumption.

The goal is achieved by the fact that in a frequency meter containing a pulse generator, the output of which is connected to the first key input, a pulse generator, the output of which is connected to the second key input through the frequency divider,

20 is connected to the counter input, a key, a counter, a computing unit and a pulse generator and a frequency divider connected in series are added, the output of the pulse former is connected to the first input of the additional terminal, the second input of which is connected to the output of the additional frequency divider, and the output additional counter, the outputs of the main and

additional counters are connected to the inputs of the computing unit. The drawing shows a block diagram of the frequency counter.

The frequency meter contains a driver 1 pulses, keys 2 and 3, counters 4 and 5 pulses, generators 6 and 7 pulses with different frequency-temperature characteristics, dividers B and 9 frequencies, computing unit 10.

The essence of the invention is that the number of periods of the measured frequency is counted over the measurement intervals formed by two different frequency generators having any different dependencies of the frequency on the temperature. When the ambient temperature changes, the frequencies of both oscillators change, which leads to a change in the duration of the measurement time intervals and, accordingly, to a change in the number of counted periods of the measured frequency during these time intervals. The measured periods of the measured frequency for the two measuring time intervals are processed in the computing unit 10 using the functional dependences of the frequencies of both generators on the ambient temperature, with the result that the output frequency code is formed at the output of the computing unit 10. In this case, the processing operator depends on the specific frequency-temperature characteristics. Thereby, the invariance of the frequency meter to a change in the ambient temperature is achieved, which leads to an increase in the measurement accuracy.

The device works as follows.

The measured frequency is fed to the input of the pulse former 1, the generated pulses through the keys 2 and 3 arrive at counters 4 and 5, respectively. With this, key 2 is opened to the measuring interval formed by generator b and divider 8,.

(one)

.

.

TO

frequency generator 6; the conversion factor of the divider 8. opens to the measuring

interval tj ,, formed by torus 7 and divisor 9,

.four

. one

one -

H - t IN

H

(2)

"but

where f g) frequency generator 7;

K ft - the coefficient of conversion of the divider 9.

The number of counted pulses N and N, j in counters 4 and 5 for measuring

intervals t and

tjj respectively is equal to:

H-- -t;

(3)

l l

  AND)

The frequencies of oscillators b and 7 are described by the following equations: Q f ol) (5);

f, (t) (6)

where f j, and the nominal frequencies of the generators 6 and 7, respectively, 5 df, (t) and

ifij (t) - frequency-temperature characteristics of the generators 6 and 7, respectively.,

0 Availability l. (t) and if | (t) leads in known frequency meter designs to the instability of the frequencies f and f. from temperature, and accordingly, to instability of measuring time intervals t y, and t.

Using expressions (-5) and (6), expressions (3) and (4) can be represented as

f.

N

- EX -. () o -, + u € -, i)

TO,

N, 4

(t)

The output signals of counters 4 and 5, i.e. NX, and N ij, are fed to the inputs of the computing unit 10, in which, after solving the system of equations (3) and (4), a code of the measured frequency value f is generated. Generators b

0 and 7 must have different frequency-temperature characteristics, and the nominal frequencies may be the same.

This frequency meter allows you to PRODUCE a highly accurate frequency measurement using non-temperature controlled oscillators, which reduces power consumption and expands the range of application of the frequency meter, allows

use it in field geophysical equipment and in laboratory measurements.

Claims (2)

Invention Formula A frequency meter containing a pulse shaper, the output of which is connected to the first key input, a pulse generator, the output of which is connected through the frequency divider to the second key input, the output of which is connected to the counter input, characterized in that, in order to improve the measurement accuracy and reduce power consumption, a key, a counter, a calculator block and a series connected pulse generator and a frequency divider are additionally entered, the output of the pulse generator connected to the first input of the additional key, the second input of which is connected to the output of the additional frequency splitter the input of the additional counter, the outputs of the main and additional counters are connected to the inputs of the computing unit. Sources of information taken into account in the examination 1, the frequency meter electron-counting 43-38. Technical description and operating instructions, 1976. 2. Shl Ndin V.I. Digital electrical measuring instruments. M., Ener (Guy, 1972, p. 65.