SU1208505A1 - Arrangement for measuring ultrasound velocity - Google Patents

Abstract

The invention relates to the technique of acoustic control and can be used to measure the velocity of propagation of ultrasonic oscillations in liquid media. The aim of the invention is to improve measurement accuracy and sensitivity by reducing the systematic error. The device forms a pulse reflected from the boundary of the protector-controlled medium to delay the leading edge of the pulse at the output of the pulse distributor 14 by an amount equal to the parasitic time delay by means of a secondary start of the generator 1 of the exciting pulse at the moment corresponding to the leading edge of the pulse at the output of the distributor 14 pulses. At the inputs of the discriminator 8, two time intervals are compared, one of which is determined by the leading edge of the first R5 - trigger 7, and the second leading edge of the pulse at the output of the second RS trigger 20. As a result, the comparable frequency of the controlled oscillator 11 will vary so that in the steady-state mode, the indicated time intervals became equal. In this case, the information on the recorder 12 will be adjusted from parasitic time delays. An introduction to the device of the logic unit 28, the control unit 6, the second RS trigger 20, limiter 15, comparator 16, and AND circuit 21 allow the described algorithm to be performed and to improve measurement accuracy and sensitivity. 1 il. (L g N5 O 00 SP ate

Description

The invention relates to acoustic control technology and can be used to measure the speed of propagation of ultrasonic oscillations in liquid media.

The purpose of the invention is to improve measurement accuracy and sensitivity by reducing the systematic

errors.

The drawing shows a block diagram of a device for measuring the speed of ultrasound.

The device contains a series of electro-acoustically connected excitation-pulse generator 1, radiating 2 and receiving 3 piezo-converters, first limiter 4, first comparator 5, control unit 6, first RS trigger 7, discriminator 8, switch 9, whose control input is connected to the output of the first RS trigger 7, the integrator 10, the controlled oscillator 11 and the recorder 12, the frequency divider 13 connected in series, the input connected to the output of the controlled oscillator 1 1, the distributor 14 pulses, the first output is connected A second limiter 15 connected in series to the R input of the first RS flip-flop 7, connected to the output of the generator 1, and a second comparator 16 connected in series with the first inverter 17, connected to the second output of the pulse distributor 14, one-vibrator 18, first circuit 19 And, the second input of which is connected to the output of the second compressor 16, the second RS - trigger 20, S-input connected to the output of the first circuit 19 And, and output to the second input of the discriminator 8, and circuit 21 P1I ,, output connected to the input generator 1, b The control box 6 is made in the form of a second inverter 22 connected in series, the input of the frequency divider 13 connected to the second one, the second circuit 23 AND, the third RS trigger 24 and the third circuit 25 AND, the second input connected to the output of the first comparator 5, and the output to S-input of the first RS-trigger 7, the third inverter 26, the input of the frequency divider 13 connected to the first output, and the output to the second input

the second circuit 23 AND, the third input of which is connected to the third output of the distributor 14 pulses connected to the first input of the circuit 21 OR, the fourth circuit 27 AND, the first input connected to the output of the second inverter 22, the second inputs to the first output of the frequency divider 13 the third entrance to the second

the output of the distributor 1-4 pulses connected to the second input of the circuit 21 OR. Position 28 denotes a logic block from the first inverter 17, the one-shot 18 and the first circuit 19 I.

The device works as follows. ,

The output pulses of the controlled oscillator 11 are fed to the input of the frequency divider 13. From the first output of the frequency divider 13, the pulses arrive at the input of the distributor 14 pulses, which determines the sequence of operation of individual functional units of the device.

A pulse C of the third output of the distributor 14 pulses through the circuit 21 OR starts the generator 1 of the excitation pulses, forming a short pulse that goes to the radiating piezoelectric transducer 2, where an ultrasonic pulse is formed, which, after successive passage

the waveguide of the radiator, the controlled medium, the waveguide of the piezoelectric transducer 3 is converted into an electrical impulse arriving at the input of the first limiter 4. For

the impulse through the first comparator 5 ,. performing a temporal reference of the receiving signal and its normalization in amplitude, is fed to the input of the player’s control unit

the role of temporary gates for the output pulse of the first comparator 5. After block 6, the signal enters the 5th input of the first RS, trigger 7. Thus, the sounding process

the controlled medium is completed by the formation of the first RS trigger 7 and the leading edge of the pulse applied to the first input of the discriminator 8.

The duration of the I "and the time interval counted from the moment of the formation of the leading edge of the pulse at the third output of the distributor 14 pulses to the time of the formation of the pulse front by the first RS trigger 3 is defined by the formula

NM L, + Lj +., O,

de L is the delay time of the electric pulse in the generator, re 1; 10

Lj, -, - the delay times in the piezoelectric elements of the radiating and receiving piezo transducers;

, the delay times of the ultrasonic pulse in the waveguides of the radiating and receiving piezoelectric transducers;

Tg, is the delay time of the ultrasound 2o. covy pulse in a controlled environment; t is the delay time of the electric pulse in the first limiter 4; 25

LP - electric time delay °

whom impulse 4 in primary commander 5;

 tj is the rem of the electric impulse delay in the control unit JQ;

 - the delay time of the electric pulse in the first RS-trigger 7; "

When using identical piezo -, elements and waveguides can be considered

l - h- -n:

l

k -5 wave

Then the duration of the probing time interval consists of the informative C formative component t and the non-informative component ti ((parasitic time delay) equal to t.

g, yy ,, - 2gb ,, / 4-g8 gd-ts,

Ch. -v in -6-n A pulse from the second output of the distributor 14 pulses through the circuit 21 OR the generator 1 is restarted, forming a short pulse arriving at the piezoelectric element of the radiating piezoelectric transducer 2.

The ultrasonic impulse formed at the same time after propagation

ten

2 25

Jq

"

-,

40

45

50 55

through the waveguide of the radiator partially passes into the controlled medium, and partially, reflecting from the waveguide-medium boundary, due to the difference in their acoustic impedances. returns back through the waveguide to the piezoelectric element radiating the piezoelectric transducer 2 and is transformed last into an electrical impulse arriving at the input of the second limiter 15.

The specified receiving signal after passing through the second limiter 15 is normalized in amplitude by the second, comparator 16, which also time-locks the latter, and is fed to the input of logic unit 28, performing the role of temporary gates and controlled by a pulse from the second output of the pulse distributor 14. Having passed the logic block 28, the pulse arrives at the S input of the second RS trigger 20, changing its state. The second sounding process is completed by forming the leading edge of the pulse at the forward output of the second RS trigger 22.

The duration of the second probe interval is determined by the following formula

r; n, + vVt..ts-u- - ,.

Based on the practical identity of the parameters of the first and second limiters, comparators and RS-triggers, it can be assumed that the duration of the second probing time interval is almost equal to the duration of the non-informative component t, the probing time interval of the controlled medium.

The duration of the time interval., "Counted from the moment

tflil

forming the leading edge of the pulse at the third output of the distributor 14 pulses until the second RS-trigger 20 forms the leading edge of the pulse, is determined by the expression

 )

where T is the period of the pulses following at the input of the distributor 14 pulses. Impulse formed first

f.S-trigger 7, enters simultaneously

The first input of the discriminator 8 and the second input of the coaxial switch 9. The impulse, formed by the second P, 5 -triger 20, is fed to the second input of the discriminator 8.

The discriminator 8 compares the duration of the time interval 1 c with the duration, T l, and analyzes the temporal location of the leading edge of the pulse at the forward output of the first RS trigger 7 relative to the leading edge of the pulse generated at the output of the second KS trigger, 20

If the leading edge of the pulse at the output of the first RS trigger 7 is ahead of the leading edge of the pulse generated at the output of the second RS trigger 20, then the output of the discriminator 8 generates a logical 1 signal (high level).

If the leading edge of the pulse at the output of the first RS trigger 7 lags behind the leading edge of the pulse generated by the second RS trigger 20, then the output of the discriminator 8 generates a logical O signal (low level).

High or low logic signals are generated at the output of the switch 9 in the presence of a high level, voltage, at the control second input. The logic levels from the output of switch 5 are fed to the input of integrator 10, connecting its input either to a high potential power bus (for logical 1) or to a low potential power bus (for logical O

The specified input switches: integrator 10 is called appropriately. increase or decrease in voltage at the integrator output. The absolute value of the output voltage of the integrator 10, which is controlling for the controlled generator 11, increases in the case when the leading edge of the pulse of the first RS trigger 7 advances in time the leading edge of the second RS trigger 20, and decreases otherwise

In the steady state operation of the device is met, the condition

- ll

IC un te-tH - T + t

 the frequency of the pulses at the output of the controlled oscillator 11;

- the division ratio of divi bodies 13,

kc L

Where

L is the speed of sound in a controlled environment;

the acoustic base of the device is the distance between the radiating and receiving piezoelectric transducers.

As follows from the above formula, the value of the frequency of the electrical pulses at the output of the controlled oscillator 11 is practically determined only by the value of the velocity of propagation of ultrasonic oscillations, since the values of the coefficient K and the base distance L are constant values.

Thus, a higher measurement accuracy is achieved in the device due to the exclusion of the parasitic (i) delay from the time interval, which leads to an error

(&about)

measure 0

STC

100%.

Moreover, with higher accuracy, sensitivity is maintained high.

Claims (1)

Invention Formula A device for measuring the speed of ultrasound, containing a series of electro-acoustically connected excitation pulse generator, radiating and receiving piezo transducers, the first limiter and comparator, the first RS-trigger in series, the discriminator, a switch, the control input of which is connected to the output of the first RS — trigger, integrator , controlled oscillator and recorder, serially connected frequency divider, input connected to the output of controlled oscillator, distributor pulse ow, the first output connected to the R input of the first R S trigger, which is similar to the fact that, in order to reduce accurate measurement and sensitivity, it is equipped with series-connected second cutter, the input connected to the output of the excitation pulse generator, and a comparator connected in series by the first inverter I, the input connected to the second output of the pulse distributor, one-shot, the first And circuit, the second input of which is connected to the output of the second comparator, the second RS trigger, the S input connected to the output of the first circuit AND, and the output to the second input of the discriminator, the OR circuit, the output connected Valid generator excitation pulses and a control unit, configured as a second inverter connected in series, the input podklyuSostavitel I.Ardasheva Editor L.Avramenko Tehred S.Migunova Corrector Order 252/55 Circulation 778 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Branch PPP Patent, Uzhgorod, st. Project, 4 208305 -8 of the second splitter And, the third RS-flip-flop and the third And circuit, the second input connected to the output 5 of the first comparator, and the output to the S-input of the first RS-trigger, the third inverter connected to the first frequency divider to the output, and output to 10 to the second input of the second circuit AND, the third input of which is connected to the third output of the pulse distributor connected to the first input of the OR circuit, the fourth AND circuit, and the first: 15 input connected to the output of the second inverter, the second input - to the first output of the frequency divider, the third input - to the third output of the pulse distributor, 20 connected to the second input of the OR circuit,