SU478242A1 - Digital Speed Meter and Ultrasound Absorption Rate - Google Patents

Description

(54) DIGITAL IZL EGRITEL SPEED

And absorption coefficient of ultrasound

one

The invention relates to a technique for studying the physicochemical properties of liquids and gases using ultrasonic waves and may find application in scientific laboratories and industry.

Known gauges of speed and coefficient. ultrasound attenuations containing a high-frequency generator, a measuring chamber with an emitter and a moving ultrasound receiver, a radio pulse amplifier with a type detector, a differentiation circuit, a software pulse counter, and a displacement pulse sensor.

However, the known devices have low productivity due to the lack of a direct reading of the measurement results.

The aim of the invention is to improve the performance of the device.

This goal is achieved due to the fact that the device is equipped with a radio pulse shaping circuit, a preselection digital frequency meter, an additional peak detector, a block

automatic adjustment of ppmlltudy. buffer amplifier differentsiplpym logarithmic amplifier, an amplitude discriminator to a source of reference voltage and high-speed digital voltmeter, the measuring input of which through a differential logarithmic amplifier connected to the output of the peak detector which is connected to an amplitude discriminator and a control input of the automatic amplitude adjusting unit, an amplifier RF pulse via a buffer an amplifier, an additional peak detector and a differentiation circuit connected to the control The pre-selection digital frequency counter input, the measurement input of the latter is connected to a displacement pulse sensor, which is connected to the trigger input of a digital voltmeter through a software counter, the high frequency generator is connected to an ultrasound emitter and an additional peak detector through an automatic amplitude control unit via a radio pulse shaping circuit .

the source of the reference voltage is connected to the second input of the differential logarithmic amplifier and to the control input of the amplitude discriminator, and the output of the latter is connected to the control input of the program counter.

FIG. 1 shows a functional diagram of the proposed device; in fig. 2 - voltage plots in individual elements of the device.

The device contains: 1 - high frequency generator, 2 -. radio pulse shaping circuit, 3 - measuring chamber, 4 - emitter, 5 - movable ultrasound receiver, 6 - amplifier of radio pulses, 7 - peak detector, 8 buffer amplifier, 9 - additional peak detector, 10 - differentiation circuit, 11 sensor of receiver movement pulses , 12 - frequency counter with pre-selection, 13 - differential logarithmic amplifier, 14 high-speed digital voltmeter, 15 - program counter, 16 - amplitude discriminator, 17 - adjustable reference voltage source, 18 - automatic unit tion adjustment amppituay,

The device works as follows.

The high frequency generator (VI) 1 produces a sinusoidal voltage, from which circuit 2 generates short radio pulses that excite the ultrasound emitter 4. It sends ultrasound waves to the test medium placed in the measuring chamber 3, which are received by the sound receiver 5, are converted into electrical pulses and arrive at the input of the amplifier 6, from the output of which to measure the ultrasound velocity, the received signal is fed to the input of the buffer amplifier 8, and then to the additional peak detector 9, the input of which is summed With a sinusoidal voltage generator HF 1, supplied through the automatic amplitude control unit 18. When you move the receiver in the medium under study, the phase of the received radio pulses changes, therefore, su.m (the dimensional signal can be recorded in the following form (neglecting the absorption in the medium and suppose that the amplitudes of both signals are equal):

Uc - UoSintOot UoSiuLcOo (, t + | -) H (i)

After conversion, we obtain

5rt

Jl. . V / l

UoCoS - Sin CoOgt -;)

(2)

and - signal amplitude;

about

WITH

- the angular frequency of the signal;

about l

- movement of the receiver;

C, L - the speed and wavelength of ultrasound;

 - phase shift, not dependent on the length of the acoustic path.

From the expression (1) it follows that the amplitude of the total signal will periodically take a zero value when moving the piezo receiver to a distance equal to the length of the sound wave.

In order to isolate the displaced component, the sum signal by the peak detector 9 is converted into a pulsating voltage and fed to a differentiation circuit 1O. It captures the interference extremes and generates short voltage pulses corresponding to the pulsation minima corresponding to the number of ultrasound waves that arrive at the control input of the digital frequency meter with preselection 12 and trigger it. Simultaneously with the arrival of the first pulse, the frequency meter 12 starts counting the pulse of movement of the sound receiver 5 generated by the sensor 11. After accumulating a predetermined number of extreme pulses, the frequency meter 12 locks up and on the digital scoreboard records the numerical value of the ultrasound velocity equal to the number of counted motion pulses. The frequency of the ultrasound and the number of waves are selected based on the expression

(3)

(µm) is the price of the impulses of the movement marks;

tt is their number; I (MGu) - ultrasound frequency;

N is the number of waves. When satisfied

f. go

- - g 10

N

where p is 0.1, 2, 3, the digital indicator will show the value of the speed of sound in cm / s. To measure the absorption, the received and amplified pulses from the output of amplifier 6 are fed to a peak detector 7, converted into a constant voltage, and fed to one input of a differential log amplifier 13, in parallel with which amplitude discriminator 16 is turned on. When the amplitude U is voltage across its input becomes equal to the reference voltage of the J-controlled source 17, the discriminator emits a short pulse, which triggers the software, the counter 15. The latter starts counting the receiver moving pulses coming from sensor 11. The same reference voltage is applied to the second input of the differential logarithmic amplifier 13, the output of which is a differential voltage proportional to the logarithm of the ratio of the amplitude of the received signal with the reference voltage. Counter 15, counting a given number of displacement pulses, is locked and gives them a pulse that triggers a fast-acting: digital voltmeter 14. The latter measures the instantaneous voltage value at the output of the differential amplifier 13, which is equal to the digital value of the measured ultrasound absorption coefficient in the medium under study. Since the voltage at the output of the logarithmic differential amplifier 13 is equal to ktn7r) iUQ where and is the current value of the voltage at the output of the peak detector 7, R is the proportionality coefficient, and when the digital voltmeter is started up, the voltage and „, also has an amplitude that and therefore. U, the expression for the amplitude absorption coefficient of ultrasound in the medium will be of the form r- (Hn | - 2a Гп Гп / .Л Ta-Ц L ® where and., And and are the amplitudes of the received signal at distances x -i o responsibly. From (6) with regard to (5) it is total that JT) -E, it follows where fn is the given number of pulses of movement of the sound receiver. Obviously, choosing k 10, where ({{O, 1, 2, 3, and the indicator of the central voltmeter, you can get the absolute digital value of the coefficient of absorption in nep / cm. For measurements in highly absorbing media, for example, in gases, The amplitude of the received signal varies significantly with the distance from the radiator.This makes it difficult to measure the ultrasound speed.To eliminate this phenomenon, an automatic voltage amplitude control circuit of the RF voltage supplied from the generator 1 to the input of the peak detector 9, is fed to the control input of the circuit voltage from the output of the detector 7 so that the amplitude of the RF voltage is always close to the amplitude of the received signal. Fig. 2 shows the voltage plots in the individual elements of the device.A Fig. 2a shows the pulsating voltage at the additional output peak detector 9, in Fig. 2 b - pulses at the output of the differentiation circuit 1O, in Fig. 2, displacement pulses at the output of sensor 11, in Fig. 2 g - displacement pulses, l, calculated by frequency meter 12, in fig. 2 d shows the voltage at the output of the peak detector 7, FIG. 2, the pulses generated by the program counter 15, in FIG. 2 l - voltage at the output of the differential logarithmic amplifier 13. Subject of the invention: Digital speed meter and ultrasound absorption factor, comprising a high frequency generator, a measuring chamber with an emitter and a movable ultrasound receiver, a radio pulse amplifier with a peak detector, a differentiation circuit, a software pulse counter and pulse sensor-. movement, characterized in that, in order to increase productivity, it is equipped with a radio pulse shaping circuit, a digital frequency meter with

a preliminary choice, an additional peak detector, an automatic amplitude adjustment unit, a buffer amplifier, a differential logarithmic amplifier, an amplitude discriminator (threshold device) with a source of reference voltage and a high-speed digital voltmeter, the measuring input of which is connected via a differential logarithmic amplifier to an output peak detector voltmeter with a peak voltmeter, which is connected to an output peak voltage detector and a high-speed digital voltmeter. which is connected to the amplitude discriminator and the control input of the automatic amplitude control unit, radio pulse amplifier via buffer amplifier, additional peak detector and differentiation circuit connected

eight

to the control input of a digital frequency meter with a preselection, the measurement input of the latter is connected to a displacement pulse sensor, which is connected to the trigger input of a digital voltmeter through a software counter, the high frequency generator is connected to an ultrasound emitter and an additional amplitude control unit through a radio pulse shaping circuit peak detector, the reference voltage source is connected to the second input of a differential log amplifier and control input of the amplitude discriminator, and the output of the latter is connected to the control input of the program counter.

kkk

6

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