SU1499252A1 - Apparatus for comparing amplitudes of a.c. signals - Google Patents

Abstract

The invention relates to electrical measuring equipment and can be used to measure the difference in amplitudes of the first harmonics of weak signals of a distorted shape or weak harmonic signals under conditions of noise and interference. The aim of the invention is to improve the accuracy, which is provided by the introduction of switches 3 and 5, a selective amplifier 4, a pulse generator 12, counting triggers 13 and 14, thereby maintaining the amplitude value of the envelope of the input signals during the conversion process, which ensures a constant signal / ratio noise for input signals. In addition, the device contains a switch 1, a selective amplifier 2, a switch 3, a detector 6, a low-pass filter 7, a filter 8 for extracting a rectangular-shaped envelope signal, an envelope signal amplifier 9, a synchronous detector 10, a measuring device 11. 2 Il.

Description

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The invention relates to electrical measuring technology and can be used to measure the difference in the amplitudes of the first harmonics of variable signals of a distorted shape or harmonic signals, under the conditions of noise and interference.

The purpose of the invention is to improve the accuracy by ensuring that the amplitude value is kept around the input signals during the conversion process, which allows the signal-to-noise ratio for the input signals to remain unchanged.

Figure 1 shows a block diagram of a device for comparing amplitudes of variable signals; figure 2 is a temporary diagram of the work of its nodes.

The device contains a serially connected switch 1 and a selective amplifier 2 of a carrier frequency signal, as well as a serially connected switch 3 and a selective amplifier 4 of a carrier frequency signal, the first inputs of switches 1 and 3 are combined and are the first input of the device, the second ones are also combined and are the second input of the device, the outputs of the selective amplifiers 2 and 4 are respectively connected with the first and second inputs of the switch 5, the output of which through the serially connected detector 6, filter 7 a low pass filter 8 for extracting a rectangular-shaped envelope signal, an amplifier 9 for the envelope signal, a synchronous detector 10 connected to the input of the measuring device 11, as well as a pulse generator 12, a counting trigger 13 and a counting trigger 14, the generator and the output 12 pulses are connected to the third control input of the switch 5 and the input of the counting flip-flop 13, the output of which is connected to the third control input of the switch 1.

The inverse output of the pulse generator 12 is connected to the input of the counting trigger 14, the output of which is connected to the corresponding control inputs of the second switch 3, the filter 8 to share the signal by the frequency square rectangle B, and the synchronous detector 10..

The device operates in the following way.

Comparative signals U (and U (fig, 2c, d) simultaneously arrive

the corresponding inputs of the switches 1 and 3. The direct and inverse pulses (figa, b) from the output of the generator 12 pulses arrive at the inputs, respectively, of the counting trigger 13 and 14, from the outputs of which the signals (fig. 2d and fig.2z) arrive to the corresponding control inputs, respectively, of switches I and 3.

At the moment to, the transducer of switch 1 is connected to its first input, the input signal IJ is fed to the selective amplifier 2 and the transition process starts in it (Fig. 2g). In addition, at the moment to, under the action of the output signals of the pulse generator 12, the spincode of the switch 5 is connected to its second input and the output voltage of the selective amplifier 4 is set to the input of the detector 6 (Fig.2l). This state is maintained until time t (Fig.26). During this time, the transition process ends in the selective amplifier 2.

At time t | (Fig. 26) The output voltage of the selective amplifier 2 kiU / is set at the output of the switch 5, which. enters the input of the detector 6 (Fig. 2l). At the same time t, the output of the switch 3 is connected to its second input and the input voltage Uj, disconnected from the input of the selective amplifier 4, and the input voltage U is connected (j. In the selective amplifier 4, the transient process ends by the time t. ( figa, k).

At time t, the output of the switch 5 is disconnected from the upper input and connected to the lower input. The signal Uf is disconnected from the input of the selective amplifier 2, and the signal Ug is connected, and a transient begins in the selective amplifier 2, which ends at time tj. From the output of the selective amplifier 4, the steady-state voltage kgUft is fed to the input of detector b (Fig.2l).

At time tj, the output of switch 5 is disconnected from the lower input and connected to the upper and installed output voltage of the selective amplifier 2 is fed to the input of the detector 6, and the output of switch 3 is connected to its upper

its input and from the input of the selective amplifier 4 is disconnected from the signal U, and connected to the U, and in it begins the transition process, which ends at time t.

Thus, switch 5 always connects the outputs selectively: x amplifiers 2 and 4 to detector 6 only when the transients in them are completed and therefore they do not affect the measurement result.

At the same time, a periodic signal is formed at the input of the detector 6, one period of which is a successively arranged equal duration of a packet of signals kgU ,, k (, (Lig. 2n). This signal is detected by the detector 6 (Fig. 2m) and after filtering 7 low frequencies (fign) it can be represented by the expression

and

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iS. and J.t-yi + Is,

 yi-i- i sign sin (ftt + iP)

ki

- ka and 2 2

U-2

sign sin 2 (Jlt + iO

CO

where k, are transmission coefficients of selective amplifiers 2 and 4, respectively, Л is the angular frequency of the signal, v is the phase of the signal.

Filter 8 for extracting a rectangular waveform from the signal (1) selects only the second term; the second one is represented in Fig. 2o, and the rest suppresses. The amplitude of the output signal of the filter 8 is proportional to the difference of the amplitudes of the input signals. The output of filter 8 is amplified by amplifier 9, rectified by synchronous detector 10, and measured by measuring device 11, whose readings are proportional to

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amplitudes of the compared signals of the invention A device for comparing the amplitudes of variable signals, comprising a serially connected first switch, whose inputs are the inputs of the Device, and a first selective carrier signal amplifier, serially connecting i, a non-specified detector, low-pass filter, dp filter of a square wave, the envelope of the signal envelope. a synchronous detector and measuring device, a pulse generator, is distinguished by the fact that, in order to increase accuracy, it additionally

0 entered in series the second switch, the second selective carrier signal amplifier and the third switch, as well as the first and second counting triggers, when the first and second inputs of the second

switch connected to the corresponding; The first and second selective inputs of the carrier are connected to the first and second inputs of the third switch, the output of which is connected to the detector input, and the direct and inverse outputs of the pulse generator are connected to the inputs of the first and second counting triggers, the direct output is connected to the third control input of the third switch, the output of the first counting trigger is connected to the third control input (the first switch, the output of the second counting t the rigger is connected to the corresponding control inputs of the second switch, the filter for

5 selection of the envelope signal of the rectangular frame and the synchronous detector.

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Claims (1)

Claim! A device for comparing the amplitudes of alternating signals, comprising a series-connected first switch, the inputs of which are inputs of the device, and a first selective amplifier of a carrier frequency signal, connected in series. a detector, a low-pass filter, a filter for isolating the envelope signal of a rectangular shape, amplify the envelope signal, a synchronous detector and measuring device, a pulse generator, characterized in that, in order to increase accuracy, they are additionally introduced into it connected in series to the second switch, the second selective amplifier of the carrier frequency signal and the third switch, as well as the first and second counting triggers, the first and second inputs of the second switch connected to the corresponding inputs of the first to mmutator, the outputs of the first and second selective amplifiers of the carrier frequency are connected respectively to the first and second inputs of the third switch, the output of which is connected to the detector input, the direct and inverse outputs of the pulse generator are connected respectively to the inputs of the first and second counting triggers, in addition, the direct output is connected with the third control input of the third switch, the output of the first counting trigger is connected to the third control input of the first switch, the output of the second counting trigger is connected to tvetstvuyuschimi second switch control inputs, a filter to extract the signal envelope of rectangular shape and which are proportional to the synchronous detekzaniya different .tora.