SU117386A1 - Electric frequency meter - Google Patents

Description

The proposed electrical frequency meter, based on measuring the phase difference of the voltage at the filter inlet and outlet, consists of a series of blocks defining the sign (order) of the measured value and containing each reference frequency generator with a shaping device, a mixer, a filter, and a phase meter.

The peculiarity of the proposed frequency meter, which provides an increase in measurement accuracy in a wide frequency range by detuning from neighboring combinable measurable frequencies, is the use in each of these blocks of a device for automatic switching of filters consisting of two crystalline diodes and two lamp resonant amplifiers with adjacent bandwidths, the anode loads of which are cross-connected with the said diodes, and the grids are connected to the output of the mixer with the indicated amplifiers the girls worked as a pope; It depends on the measured frequency in the first or the second half of the working range of this unit.

FIG. 1 shows a block diagram of a part of the proposed frequency meter; in fig. 2 is a schematic diagram of a device for automatically switching filters.

The frequency meter consists of a series of blocks, of which the block / (Fig. 1) is intended for rough measurement of the frequency, and the // and /// blocks determine the second, third, fourth signs of the measured value.

The unit / input: a limiting amplifier U, which receives a signal frequency / d., A calibrated filter / SF1 and a phase meter F.

Each of the same //, /// ... blocks, differing from each other only by the magnitude of the reference frequency and the parameters of calibrated filters and resonant amplifiers, includes: a generator G of the reference frequency F, a shaping device FU, a mixer C, two resonances № 117386

two power amplifiers (RU, RU2 on LL La lamps (Fig. 2)), two crystalline diodes DL, switch / (calibrated filter / SF2 and phase meter) 02.

The calibrated filter of the block / has a linear phase characteristic within the operating range from the lower / "to the upper f and the limits of the measured frequency.

The block phase meter Ji / measures the phase difference of the voltages at the input and output of the filter, which is linearly dependent on frequency. The circuit is set up so that when the measured frequency is changed from / f to f the readings of the phase meter dial indicator change from zero to the maximum value.

To ensure correct operation of unit II, it is necessary that the bandwidths of the resonant amplifiers of the switchgear and switchgear are adjacent, equal and 2 times smaller than the width of the range of measured frequencies,

f-f t e - t4-- GDR n - frequency rate multiplicity, represented by Yush

is an integer, it shows, how many subranges the block scale is divided into / for a more accurate frequency measurement by the block //.

The bandwidth of the calibrated filter KF2 should be twice as wide as the bandwidth D / of each resonant amplifier and equal to 2 D / /.

From generator G in the block, voltage is applied at a frequency F to a shaping device FU, the output of which produces pulses with a repetition frequency F and a uniform spectrum in the range from frequencies F to nF (at a decade count from F to 10 F).

These pulses are fed to mixer C, which serves for spectral transformations.

The lamp amplifiers RC: and RF and diodes Dy D form a device for automatic switching of filters (Fig. 2), which regulates the operation of the entire circuit. Depending on the nature of the spectrum of the signal taken from mixer C, either the RU amplifier or the resonance amplifier RU2 is turned on.

Switch K is controlled by this device and is intended for switching the signals of resonant amplifiers RU1 and RU2 for common load. At the same time, it is a power amplifier.

The anode loads of the resonant amplifiers RU and RU2 on JIi and JA lamps consist of dual-circuit systems providing the necessary selectivity.

The D and Yes crystal diodes are included in the amplifier circuit. The voltage from mixer C is fed simultaneously to the grids of both the lamps L1 and L.

Let frequency. the signal slowly changes from a value of " upwards. When it changes /,. from f "to /" + 0.5 F, the RU1 amplifier works and the signal from its anode load is applied to the diode D which produces a negative mixture on the resistance R, locking the Luo lamp to the amplifier RU2.

The mode of operation of the circuit is chosen so that by increasing the frequency of the input signal to a value of < + 0.5 F (which corresponds to the bandwidth limit of both amplifiers), the lamp L2 begins to slightly open due to a decrease in the negative bias. At the same time, a signal appears at its anode load, which is rectified by diode D2 and creeps up the lamp, which leads to a decrease in the alternating voltage at the anode of the lamp, and consequently, further unlocking of the lamp L2, and so on. the result of which the lamp L2 is unlocked and the lamp L1 is locked. This

the process, called internal flip, occurs when the signal passes the internal border of the passbands of the RU and amplifiers. In this case, the reading of the phase meter does not change.

With further increase in frequency. From / „+ 0.5 / to /„ + f, the amplifier RU2 works, since the specified range corresponds to its passband. The voltage from its anode load is removed by an Ich detector, which produces a negative voltage on the resistance Rz, which locks the lamp L.

As soon as the frequency / reaches the value of f - - P, which corresponds to the upper border of the transmitting band of the amplifier RU, the lamp L begins to gradually open and a combination signal with frequency / d begins to be released at its anode load. -F fn + P-Pn which appears in the zone of the amplifier band. The appearance of a signal in the anode load of the MZ lamp causes an avalanche-like process of unlocking the / 7i lamp and locking the lamp ./Ts. This process, called external perebor, occurs when the signal passes the external border of the passband of the amplifier RU, when it moves towards increasing frequency (or the external border of the passband of the amplifier Pyi when moving towards decreasing frequency). With further increase in frequency / d. there will be alternation of internal and external transfers at intervals equal to Q, 5F.

To control the commutator lamps K., the voltages produced by the D and D diodes are used, the outputs of which in the diagrams are denoted by the letters M W. N.

The jump of the phase meter readings from the maximum value to zero occurs when an external transfer occurs when the frequency changes in the direction of increasing. When the frequency changes (downwards), all processes occur in reverse order.

The remaining blocks ///, IV ... work in a similar way. Since the reference frequency in each subsequent block is n times smaller than the frequency of the previous block, the readings of the corresponding phase meter will change several times faster. Therefore, each subsequent phase meter will determine the subsequent sign of the measured frequency. Such a division can be made until the resolution of the final block is comparable with the instability of the phase characteristics of the calibrated filter.

Subject invention

An electrical frequency meter based on measuring the phase difference of the voltage at the input and output of the filter and consisting of a series of blocks determining the sign (order) of the measured value and containing each reference frequency generator with a shaping device, a mixer, a filter and a phase meter that differs By the fact that, in order to increase the measurement accuracy in a wide range of frequencies by detuning from the neighboring combinational frequencies, the device for automatic switching of filters consisting of two crystal diodes and two lamp resonant amplifiers with equal and adjacent bandwidths, the anode loads of which are cross-connected with the said diodes, and the grids are connected to the mixer output, so that these amplifiers work alternately depending on whether the measured frequency lies in or the second half of the working range of this unit.

№ 117386