SU1273821A2 - Instrument amplifier - Google Patents

Abstract

The invention relates to the field of electrical measurements and is a further invention to the author. St. H 364073. Can be used to transfer measurement information between circuits requiring galvanic isolation. The purpose of the invention is the expansion of the operating frequency band, an increase in accuracy, a reduction in mass w and dimensions — the modulated carrier oscillation is transmitted through a resonant circuit. To do this, parallel to the secondary winding of separation transformer 2 and the input of amplifier 3, a capacitor 8 is connected, forming an oscillating circuit with this winding, tuned to carrier frequency. The drawing also shows: an input modulator 1, a synchronous demodulator 4, a generator 5 carrying a clock, a filter 6 low tactoT, a modulator 7 feedback. In the device, due to the conversion of the rectangular form 9 of the carrier voltage into a sinusoidal by an oscillating circuit, the conversion error decreases (caused by the influence of the instability of the switching time of the keys from modulators 1 and 7. 2 ill.

Description

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The invention relates to electron measurements and can be used to transfer measurement information between circuits requiring galvanic isolation.

The purpose of the invention is to expand the operating frequency band, improve accuracy, reduce mass and size by passing the modulated carrier oscillation through a resonant circuit.

FIG. 1 shows the structural diagram of the measuring amplifier; in fig. 2 - time diagrams, p. his work.

The measuring amplifier contains an input modulator 1, the output of which is connected to the primary winding of isolation transformer 2, the secondary winding of which is connected to the input of the amplifier 3, the output of which is connected to the input through a synchronous demodulator A, as well as a generator 5 of the carrier frequency and a low-frequency filter 6. The input of which is connected to the output of demodulator 4. The output of the low frequency filter is connected to the output bus and the input of the feedback modulator 7, the output of which is connected to the feedback winding of the transformer 2, K iodulator 1 and modulator 7. feedback and synchronous demodulator A moves are connected to the generator frequency 5 of the carrier frequency. 1m / parallel to the secondary winding of the transformer 2 is connected a capacitor 8, which forms with it an oscillating circuit tuned to the carrier frequency.

The measuring amplifier works as follows.

The input signal is fed to the input of the modulator 1, to the control input of which a carrier frequency signal is supplied from the generator 5. The MB1 generator generates an amplitude modulated carrier voltage, the amplitude of which varies in proportion to the change in the input signal (Fig. 2a). Amplitude modulated voltage is transmitted through transformer 2 (Fig. 2, b). The oscillating circuit formed by the secondary winding of the transformer 2 and the capacitor 8 separates from the voltage of the secondary winding a sinusoidal voltage with a carrier frequency, which is its first harmonic (Fig. 2c). Sinusoidal

the voltage is rectified by the pho-modulator 4 (Fig. 2, d). From this low-pass phi-voltage 6, a voltage modulated by a voltage that is proportional to the input voltage is modulated. A feedback modulator 7 converts the output voltage of the converter into an amplitude modulated carrier frequency as well. as

converts input modulator 1 input voltage. The amplitude-modulated voltage. With the output of the modulator 7 is fed to the feedback winding of the transformer 2. The magnetizing force of the feedback winding balances the magnetized force of the primary winding, and their difference determines the voltage on the secondary winding. The presence of an oscillating circuit in the input circuit of demodulator A allows increasing the carrier frequency, which allows reducing the size and weight of transformer 2. Increasing the carrier frequency also provides the possibility of increasing the input signal's chitote, i.e. allows to expand the operating frequency band. In the measurement amplifier, the conversion error caused by the instability of the switching time of the keys of the modulators 1 and 7 is reduced by the oscillating contour of the rectangular form of the carrier voltage into sinusoidal, because such instability affects the sinusoidal pulse area to a lesser degree (Fig. 2, e) and less changes its energy. The error due to the instability of the switching time of the keys decreases by 7.4 times the time where T is the period of the modules.

t, and is the switching time of the modulator keys. By adjusting the oscillating circuit, which includes the secondary winding of the isolation transformer, to the carrier frequency, the disturbance penetrating from the control circuit through the electrode capacitance of the modulator keys is shifted in phase by 90 ° with respect to the input signal and the demodulator control signal. As a result, the mean value of the interference from de-modulation and filtering is zero .;

Thus, the use of isobenon provides the expansion of the operating frequency band, a decrease in the mass of dimensions and an increase in accuracy. invention invention Measuring amplifier according to the authors. St. No. 364073, distinguished by the fact that, in order to expand the operating frequency band, reduce the weight and size, to build precision, a capacitor is connected parallel to the secondary winding of the isolation transformer and the amplifier input, which forms an oscillatory circuit tuned to the secondary winding.

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Claims (1)

Claim Measuring amplifier according to ed. St. N "-364073, distinguishing I have a theme that, in order to expand the working frequency band, reduce weight and dimensions, improve accuracy, 1 27382 1 parallel to the secondary winding of the power transformer and the amplifier input, a capacitor is connected, which forms an oscillating circuit with a secondary winding, tuned to the applied frequency. Figure 2