SU1250854A1 - Device for measuring increment of propagation velocity of ultrasound - Google Patents

Abstract

The invention relates to a measurement technique and can be used in measuring the increment of the velocity of propagation of ultrasound. The aim of the invention is to increase the sensitivity and accuracy of measurements by measuring the phase difference of the received signals in the standing wave mode. In the device for measuring the increment of the ultrasound propagation velocity, the alternating voltage with frequency f from the generator output is fed to the second input of the first mixer, to the first input of which alternating voltage f j is fed from the output of the controlled generator. At the first and second outputs of the first mixer, an alternating voltage is output at a frequency f) fi - fj. From the first output of the first mixer, the alternating voltage is supplied to the radiating electroacoustic converter, and from the second output of the first mixer to the third input of the phase detector, to the first input of which the voltage is supplied from the receiving electroacoustic converter. A phase shift, proportional to the change in speed, is measured in a discrete manner at the difference frequency Af, (f. Is the voltage at the output of the heterodin), which is obtained by supplying the second mixer to the second input of the phase detector through a frequency shifter .- fj ( fi is the frequency of the voltage at the output of the controlled generator). At the output of the second arm of the phase detector, pulses of the same frequency as at the output of the first arm are received, only in time corresponding to the phase delay of the signal in the measuring chamber at the frequency Vi li - fj, but transferred to the frequency dG –f; When measuring the propagation speed of ultrasound, a voltage is generated at the first output of the phase detector, which is proportional to the phase shift of the signal with frequency V at the difference frequency l, which is fed to the processing and display unit. 1 il. and $ (L to ate about SH) SP

Description

The invention relates to a measurement technique and can be used in measuring the increment of the velocity of propagation of ultrasound.

The aim of the invention is to increase the sensitivity and accuracy of measurements by measuring the phase difference of the received signals in the standing wave mode.

The drawing shows a device for measuring the increment of the velocity of propagation of ultrasound.

The device for measuring the increment of the ultrasound propagation velocity includes a measuring chamber 1 with radiating and receiving electroacoustic transducers (not indicated in the drawing) generator 2, local oscillator 3, processing and display unit 4, phase detector 5, the first input of which is connected to the output of the receiving electroacoustic transducer ( not shown in the drawing), and the first output is connected to the input of the processing and display unit 4, / the generator 6 is connected to the first output of the first mixer 7, the second input is connected connected to the output of the generator 2, the first output to the input of the radiating electroacoustic converter (not indicated in the drawing), the second mixer 8, the first input connected to the output of the controlled generator 6, the second input to the output of the local oscillator 3, the multivibrator 9, the phase shifter 10, the first the input connected to the output of the multivibrator 9, the second input to the output of the second mixer 8, the output to the second input of the phase detector 5, the third input to the second output of the first mixer 7, meter 11 frequency deviation, the input connected to the three the output of the first mixer 7, the frequency meter 12, the input connected to the fourth output of the first mixer 7, the output to the second input of the processing and display unit 4, the amplitude detector 13, the input connected to the output of the receiving electroacoustic converter (not indicated in the drawing), switch 14, an input connected to the second output of the phase detector 5, and an output to the input of a controlled oscillator 6.

A device for measuring the increment of the speed of ultrasound propagation works as follows.

Frequency-stabilized alternating voltage with frequency f, from the output of generator 2 is fed to the second input of the first mixer 7, to the first input of which alternating voltage fj is fed from the output of the controlled generator 6. At the first and second output of the first mixer 7 an alternating voltage is output f fj-Гз. The use of such a scheme allows one to obtain a frequency tuning in he5.

how many ten kilohertz high stability. From the first output of the first mixer 7, the alternating voltage is supplied to the radiating electroacoustic converter, and from the second output of the mixer 7 to the third input of the phase detector 5, the first input of which is supplied from the receiving electroacoustic converter.

A phase shift, proportional to the change in speed, is measured in a discrete manner at the difference frequency dG (fj is the voltage frequency at the output of the heteroid 3), which is obtained by applying the voltage from the second mixer 8 to the second input of the second mixer 8 through the phase shifter 10 f fj -. (l-frequency voltage at the output of the generator 2).

Two voltage variables are supplied to the first arm (not shown in the drawing) of phase detector 5, o.o of which frequency fj 1 - fj directly from the second output of the first mixer 7, the other - from the second mixer 8 through the phase shifter 10. At the output of this arm (not indicated in the drawing) of the phase detector 5, pulses with a frequency fj - fx / if are received. The second arm (not indicated in the drawing) of the phase detector 5 is supplied with a variable voltage of frequency 0 fl coming from the receiving electroacoustic converter, and the alternating voltage of frequency f is output from the second mixer 8 through the phase shifter 10. The output of the second arm of the phase detector 5 produces the pulses of the same frequency as 5 and at the output of the first arm, only in time, corresponding to the phase delay of the signal in the measuring chamber at a frequency fi f. - fj but ported to frequency

M fi fz When the ultrasound propagation velocity changes, a voltage is generated at the first output of the phase detector 5, which is proportional to the phase shift of the frequency signal fi at the difference frequency l f, which is fed to the processing and display unit 4, which also receives a control signal from the output frequency meter 12 measuring the voltage frequency at the fourth output of the first mixer 7.

The processing and display unit 4 provides an indication of the magnitude of the increment of the speed of ultrasound propagation in the test medium.

Before measuring the magnitude of the propagation velocity increment in the medium, first manually adjusting the controlled oscillator 6 by the maximum of the signal on the amplitude detector 13 is performed. Then the multivibrator 9 is activated, which controls the phase shift. At the same time due to negative

0

The feedback signal from the output of the phase detector 5 controls the frequency through the switch 14 of the controlled oscillator 6, and the average frequency and frequency deviation at the outputs of the first mixer 7 is changed. Manual adjustment of the phase shifter 10 achieves a minimum of the readings of the meter 11 frequency deviation, which corresponds to the maximum slope of the phase-frequency characteristic of the measuring chamber.

Then the auto-tuning frequency is disabled.

Claims (1)

Invention Formula An apparatus for measuring the increment of the ultrasound propagation velocity, comprising a measuring chamber with radiating and receiving electroacoustic transducers, a generator, a local oscillator, a processing and display unit, a phase detector, the first input of which is connected to the output of the receiving electroacoustic transducer, and the first output to the input of the unit processing and display, characterized in that, in order to increase sensitivity and measurement accuracy, it is equipped with a controlled generator, connected to its first output by a first mixer, a second input connected to the generator output, a first output to an input of an emitting electroacoustic converter, a second mixer, a first input connected to the output of a controlled generator, the second input - with the output of the local oscillator, multivibrator, phase shifter, the first input connected to the output of the multivibrator, the second input - with the output of the second mixer, the output - with the second input of the phase about the detector, the third input connected to the second output of the first mixer, the frequency deviation meter, the input connected to the third output of the first mixer, the frequency meter, the input connected to the fourth output of the first mixer, the output to the second input of the processing and display unit, the amplitude detector, the input connected to the output of the receiving electroacoustic converter, a switch connected to the second output of the phase detector, and the output to the input of a controlled oscillator.