SU426186A1 - METHOD FOR DETERMINING THE DISPERSION CHARACTERISTICS OF THE ENVIRONMENT - Google Patents

Description

one

The invention relates to a measurement technique and can be used, for example, to experimentally determine the main characteristic of a dispersive acoustic delay LINE - the dependence of the delay time on the frequency of the signal components.

Methods are known for determining the dissonance characteristic of a medium by measuring the delay time of the components of an acoustic signal transmitted through it, based on radiation of an elastic pulse into the medium, receiving a frequency-modulated pulse, adding the output signal to the auxiliary electric harmonic signal of the required phase, visualizing it with an oscilloscope, and measuring time interval on its screen.

The accuracy of determining the dispersion characteristic of the medium by such methods is determined by the frequency dependence of the propagation of the WAVE in the medium. The stronger this dependence, the lower the accuracy of the method.

The purpose of the invention is to increase the accuracy of the measurement of the delay time.

This is achieved by changing the frequency of the sum signal by a constant and multiplying it. By changing the phase of the auxiliary signal, the minimum amplitude of the converted sum signal with the smallest envelope in its vicinity is required to register the amplitude.

In practice, it is often necessary to determine the dispersion characteristic of a medium at relatively high frequencies. In this case, it is not possible to construct a multiplier for measurements due to the fact that the frequency of the signal after multiplying is unacceptably high.

It is known that the main element of the frequency multiplier is a cell that increases the frequency by a factor of 2, and the condition must be met to perform the multiplication operation.

/at

/ n

where / n and / in, respectively, the lowest and highest frequencies in the frequency band of the signal spectrum emitted into the medium under study. Since for measurements it is necessary to use signals having a finite width of the frequency spectrum, frequency multiplication is difficult if the ratio fn / fii is close to two

To eliminate this, but the proposed method, the frequency of the total signal is first changed to a constant value and then multiplied. In the nerve case, this change is expressed in that the frequency of the total signal is reduced, and in the second, it is increased.

FIG. 1 shows a block diagram of an apparatus for carrying out the method.

The block diagram contains the generator 1, the generating untimely voltage frequency /,

connected to the phase shifter 2 and block 3,

forming rectangular pulses with zapolpepy, electro-acoustic transducer 4, emitting an elastic pulse into the test environment 5, electro-acoustic receiver 6, receiving an elastic frequency-modulated pulse, amplifier 7, amplifying the received signal, adder 8, from the output of which Relieve the voltage of the total signal, mixer 9, changing the frequency of the total signal supplied to its input from the output of the adder 8, generator 10, generating an alternating voltage, frequency multiplier 11, electronically ray oscilloscope 12, pas input of which is fed the sum voltage signal output from the voltage multiplier 11. The oscilloscope is triggered .korotkimi Scan pulses from block 3 in the medium pulse radiation time of 5.

The method is carried out as follows.

By adjusting the elements of the adder 8, the amplitudes of the variable depressions supplied from the output of the amplifier 7 and the output of the phase rotator 2 to the adder 8 are achieved. from the multiplier output is fed to the input of the oscilloscope 12.

Using the phase shifter 2, the zero or minimum amplitude of the total signal envelope is observed on the oscilloscope screen. The waveform on the oscilloscope screen in this case is similar to the graph shown in Figure 10 in FIG. 2. The delay time LL / is found by the position of the pool or the minimum envelope amplitude and by the calibration sweep speed of the oscilloscope 12, and the delay time is determined by the zero or minimum amplitude of the total signal with the smallest envelope in its vicinity. By changing the frequency of the generator 1 and repeating the described operations, find the delay times for other frequencies in the studied Dianazone, thus determining the dispersion characteristic of the medium.

Subject invention

The method of determining the dispersion characteristic of the medium by measuring the delay time of the components of the acoustic signal passing through it, based on the irradiation of the elastic pulse to the medium, receiving the frequency-modulated pulse, adding the output signal to the auxiliary electric harmonic signal of the required phase, visualizing it with an oscilloscope, and measuring the time signal interval on its screen, characterized in that, in order to increase the accuracy of the measurement of the delay time, the frequency of the total signal from change to a constant value and multiply,

after that, changing the phase of the auxiliary signal, the minimum of the amplitude of the converted total signal with the smallest envelope in its vicinity is required to register the amplitude.