RU227036U1 - ANALOG FREQUENCY METER - Google Patents

Abstract

The utility model relates to electrical measuring equipment and is intended for measuring the frequency of an arbitrary waveform. The device contains a comparator, an integrator, a module extraction unit, a first and second one-shot device, an adder, a sampling and storage unit, a hyperbolic converter and a measuring device, wherein the input of the frequency meter is connected to the input of the comparator, the output of which is connected to the inputs of the first and second one-shot devices, and the integrator, the output of which connected to the input of the module extraction block, the output of which is connected to the input of the sampling and storage block, the output of which is connected to the measuring device through a hyperbolic converter, and the outputs of the first and second monostables are connected, respectively, to the first and second inputs of the adder, the output of which is connected to the control input of the sampling block and storage. The technical result of the claimed utility model is to increase the performance of the device. 2 ill.

Description

The utility model relates to electrical measuring equipment and is intended for measuring the frequency of an arbitrary waveform.

A known analog frequency meter [USSR Author's Certificate No. 943595 IPC ⁸ G01R 23/02, publ. 07.15.1982], containing a hyperbolic converter consisting of N RC circuits connected in parallel, the input of which is connected to the reference voltage bus, an input driver, the input of which is connected to the input bus, and the output is connected to the control input of the analog switch, a storage capacitor, a measuring device, an adder and a one-shot, and N switches are introduced into the hyperbolic converter, connected in parallel with the capacitors of the RC circuits, and the control inputs of the N switches are connected through the one-shot to the output of the input driver, the output of the hyperbolic converter is connected to the input of the adder, the output of which is connected through an analog switch to input of the measuring device, in parallel with which a storage capacitor is connected.

The disadvantage of this device is the insufficient accuracy of frequency measurement due to the use of the approximator as a hyperbolic converter. And increasing the number of approximation steps in order to increase the measurement accuracy certainly leads to an increase in the bulkiness of the circuit and loss of accuracy due to the large number of non-ideal keys, scatter and temporary changes in component parameters.

The closest analogue to the proposed utility model is an analog frequency meter [Patent for PM No. 169440 of the Russian Federation, IPC G01R 23/00, publ. 03/17/2017], containing a comparator, an integrator, a one-shot device, a sampling and storage unit, a hyperbolic converter and a measuring device, wherein the input of the frequency meter is connected to the input of the comparator, the output of which is connected to the inputs of the one-shot device and the integrator, the output of which is connected to the input of the sampling unit and storage, the output of which is connected to the measuring device through a hyperbolic converter, and the output of the one-shot device is connected to the control input of the sampling and storage unit.

This technical solution was chosen as a prototype.

The disadvantage of this device is its low performance, especially in transient modes.

The technical result of the claimed utility model is to increase the performance of the device.

The specified technical result is achieved by the fact that in a known analog frequency meter containing a comparator, an integrator, a first monostable, a sampling and storage unit, a hyperbolic converter and a measuring device, the input of the frequency meter is connected to the input of the comparator, the output of which is connected to the inputs of the first monostable and integrator, and The output of the sampling and storage block is connected to the measuring device through a hyperbolic converter; additionally, a module selection block, a second one-shot and an adder are introduced, and the output of the integrator through the module selection block is connected to the input of the sampling and storage block, the control input of which is connected to the output of the adder, the second input of which connected to the output of the second one-shot, the input of which is connected to the input of the first one-shot, the output of which is connected to the first input of the adder.

Significant differences of the proposed frequency meter are the additional introduction of a module selection block, a second one-shot unit, an adder, and the organization of new connections between the elements of the device. The combination of elements and connections between them ensures the achievement of a positive effect - increasing the speed of the frequency meter.

The essence of the utility model is illustrated by drawings.

In fig. 1 shows a functional diagram of an analog frequency meter;

in fig. 2 - time diagrams of voltages u _in , u ₁ -u ₇ and u _out .

The device (Fig. 1) contains a comparator 1, an integrator 2, a module isolation unit 3, the first and second monostables 4 and 5, an adder 6, a sampling and storage unit 7, a hyperbolic converter 8 and a measuring device 9.

The frequency meter works as follows.

Input voltage _uin AC of arbitrary shape with frequency ƒin _is supplied to the input of comparator 1 (Fig. 2). At its output, a rectangular voltage u ₁ is formed with the same amplitude u _1m of positive and negative pulses, which is supplied to the inputs of integrator 2 and the first and second monovibrators 4 and 5.

At the output of integrator 2, a triangular voltage u ₂ is generated with an amplitude determined by the expression:

where U _1m is the amplitude of the output voltage of comparator 1;

T - period of input voltage _uin ;

ƒ _input - frequency of input voltage u _input ;

R is the resistance of integrator resistor 2;

C is the capacitance of integrator capacitor 2.

From expression (1) it is clear that the amplitude U _2m of the output voltage u ₂ of integrator 2 is directly proportional to the period T and inversely proportional to the frequency ƒ _input voltage u _input .

The output voltage of integrator 2 is supplied to the input of the isolation block of module 3, at the output of which a unipolar voltage u ₃ of a triangular shape is formed with an amplitude U _2m and a frequency 2ƒ _input twice the frequency ƒ _input of the input signal u _input (Fig. 2). This voltage u ₃ is supplied to the input of the sampling and storage unit 7.

At the same time, monovibrator 4 generates narrow pulses u ₄ along the decline of rectangular voltage pulses u ₁ , and monovibrator 5 generates narrow pulses u ₅ along the leading edge of rectangular voltage pulses u ₁ . In the adder 6, the output pulses u ₄ and u ₅ of monostables 4 and 5 are summed and the resulting pulses u ₆ are fed to the control input of the sampling and storage unit 7.

Since the arrival times of control pulses u ₃ always coincide with the amplitude voltage u ₃ , and their duration is much less than the period T, the constant voltage u ₇ generated at the output of the sampling and storage unit 7 will be almost equal to the amplitude value U _2m of the voltage u ₃ .

The voltage u ₇ from the output of the sampling and storage unit 7 is supplied to the input of the hyperbolic converter 8, at the output of which, as in the prototype, the output voltage of the frequency meter is formed:

,

Where - proportionality coefficient.

Thus, a constant voltage U _out is formed at the output of the frequency meter, proportional to the frequency ƒ _{in of} the input signal of an arbitrary shape. Measuring device 9 records the frequency value ƒ _{input of} the input signal.

Due to the fact that the sampling frequency of the sampling and storage unit 7 is twice as high as that of the prototype, the speed of the frequency meter is doubled.

In the practical implementation of the proposed frequency meter, comparator 1 can be implemented on an operational amplifier (op-amp) with a two-way voltage limiter on a two-anode zener diode in its feedback circuit. Integrator 2 can be implemented according to a well-known circuit using an op-amp with a timing RC circuit. The isolation block of module 3 can be made in the form of a full-wave rectifier using an op-amp according to the circuit (A. J. Peyton, V. Volsh. Analog electronics on operational amplifiers. - M.: BINOM, 1994, p. 315, Fig. 11.37). One-shot 4 and 5 can be made on the K561AG1 chip. Adder 5 is a non-inverting op-amp adder. The 1100SK2 microcircuit can be used as a sampling and storage unit 7. Hyperbolic converter 8 can be made according to a well-known scheme (A. J. Peyton, V. Volsh. Analog electronics on operational amplifiers. - M.: BINOM, 1994, p. 260, Fig. 10.1,6), using an op-amp and a voltage multiplier on microcircuit KR525PS3. Measuring device 9 is a DC voltmeter, the scale of which is graduated in Hertz.

Claims (1)

An analog frequency meter containing a comparator, an integrator, a first one-shot, a sampling and storage unit, a hyperbolic converter and a measuring device, wherein the input of the frequency meter is connected to the input of the comparator, the output of which is connected to the inputs of the first one-shot and integrator, and the output of the sampling and storage unit is connected through a hyperbolic converter with a measuring device, characterized in that it additionally contains a module selection block, a second one-shot and an adder, and the output of the integrator through the module selection block is connected to the input of the sampling and storage block, the control input of which is connected to the output of the adder, the second input of which is connected to the output a second one-shot whose input is connected to the input of the first one-shot, the output of which is connected to the first input of the adder.

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