SU757922A1 - Liquid media density measuring method - Google Patents

Description

The invention relates to means of ultrasonic measuring equipment and can be applied to measure the density of a liquid. five

Known ultrasonic densitometer based on measuring the attenuation of ultrasound transmitted through a controlled medium and containing a piezoelectric transducer, operating and compensating ultrasonic cameras located on opposite sides of a piezoelectric transducer with reflective screens installed at different distances from the piezoelectric transducer, and in the compensation chamber between the piezoelectric transducer and reflective screen. is located driven in rotation 2θ by a synchronous motor modulating disk - obturator U.

In this device, the density of the controlled medium is judged on the basis of a comparison of the amplitudes of the 25 ultrasonic waves that have passed the controlled and the reference medium, respectively. However, the amplitude of ultrasound depends not only on the density, but also on other acoustic parameters of the medium, for example.

measures, the absorption coefficient, therefore, an unambiguous determination of the density is possible only for a certain class of substances for which the dependence of amplitude on density is known. This narrows the scope of application tightly and is a source of error.

The closest technical solution to the present invention is a device for measuring the absorption coefficient of ultrasound, containing a measuring chamber with two transducers connected in series, an amplifier, a 0.707 level determination unit and a generator, a control unit, an indicator and a driver, and a frequency deviation meter connected frequency-voltage converter, low-frequency amplifier-detector, indicator, and connected to the generator output, and the converter Is the frequency-voltage made in the form of a serially connected driver, a single pulse selector and a low-frequency filter, and the second input of the single pulse selector

3

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through the second driver is connected

to the output of the high frequency generator.

The indicator readings are proportional to the passband of a resonant system consisting of both transducers and a column of the medium under study between them. On lane ³ propus- Kania affects both the absorption of ultrasound in the medium, and the reflection properties of transducers which zavisyat'takzhe from specific acoustic. "Cesky resistance, i.e. from the density ^and of the medium and the velocity of ultrasound in it. Influence of reflective properties. more when the ultrasound frequency lies in the resonance region of the transducers, and absorption in the medium is small. Thus, the known device can give information about the density, but only for certain liquids, which is its disadvantage. In addition, its 20 output signal is analog [2].

The aim of the invention is to expand the range of measured densities and provide a digital measurement of signal acquisition. 25

This goal is achieved by introducing a digital integrator, a mixer, the first and second elements AND, an OR element, an inverter and a trigger, the input of which is connected to the first output of the indicator-counter, the second input and the second output of which are connected respectively to the first output and the second input of the control unit, the second output of which,

connected to the first inputs of the first ³³

and the second elements And, the second inputs of which are connected respectively to the first and second outputs of the trigger, while the third inputs of the elements And are connected respectively to the input and output of the inverter, to the input of which the output of the driver is connected, the input of which is connected to the output of the mixer, the first input which is connected to the output of the amplifier, and the second input of the mixer is connected to the Second output of the modulated signal generator, and the outputs of the first and second elements AND are connected respectively to the first and second inputs of the OR element, the output The one of which is connected to the first control input of the digital inverter, whose information input is connected to the third output of the modulated signal generator, and the second input of the first element I is connected to the ³³ second control input of the digital integrator, the output of which is connected to the third input of the control unit.

FIG. 1 shows a block diagram of the device; in fig. 2 - diagrams 60 voltage and frequency in a number of points of the scheme.

A band generator with a frequency modulator 1 through pulse modulator 2 is connected to a piezo emitter 5

3, located in the measuring chamber 4. The piezotron receiver 5 is connected to the input of the amplifier 6, and the output of the amplifier is connected to the level determining unit 7 0.707. The output of block 7 is connected to the 5th input of the generator 1 setting, also to the counter indicator 8 and to the ^ block of the board 9, the indicator counter 8 is also connected to the control unit 9 and to the trigger input 10. The outputs of the generator 1 and the amplifier 6 are connected to the mixer inputs 11, the output of which is connected to the serial circuit from the driver 12 and the inverter 13. The video pulse output of the pulse modulator 2 is connected to the input 5 of the digital integrator composed of a key 17, a switch 18 and a reversible counter 19. The control output 17 is connected to control the key 17 16, the outputs of three-input coincidence circuits 14 and 15. The outputs of the coincidence circuits are connected to the output of the control unit 9, the output of the driver 12, the output of the trigger 10 25 and the output of the control unit 9, the output of the inverter 13, another output of the trigger 10 The output of the reversible counter 19 is connected to the control unit 9, and the other output of the trigger 10 is also connected to the mode switch 18.

FIG. 2 graph 20 shows the dependence of the frequency of the generator 1 on the time. Charts 21 and 22 are output voltages (video pulses)

2 $ of the amplifier 6 and the mixer 11. The output voltages of the driver 12 and the inverter 13 are shown by graphs 23 and 24, and the trigger 10 by the graph 25. Packs of pulses arriving at the input of counter 19 in addition mode,

40 are depicted in graph 26, and those entering in the subtraction mode are shown in graph 27.

The device works as follows. Generator 1 generates a voltage of $ 5, which is the frequency voltage, which can change under the influence of signals from block 7. Modulator 2 produces radio pulses from the voltage applied to the piezoelectric generator 3, which

mounted in chamber 4. The 3 packs of ultrasonic waves produced by the emitter are distributed in the test substance located in the chamber 4 4. The activity of the pulse selects ³³ wounds less than the time of a double run of the distance between piezoelectric transducers 3 and 5, and the period is longer. time of complete absorption of ultrasound due to repeated mileage, so that wave interference is absent. With the passage of the ultrasound frequency, its values, equal to the resonant frequency of the piezo emitter 3, received by the piezoelectric receiver 5 and amplified by radio amplifier 6, bu5

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1 will be modulated according to the law of the resonant characteristics of the radiator 3, so

as a piezo receiver 5 broadband.

In the simplest case, a higher-frequency transducer operating out of resonance is used as a piezo-receiver. The block 7 for determining the level of 0.707 produces a pulse each time the amplitude of the output pulses of the piezo receiver 5 decreases to 0.707 from the maximum resonance value. This impulse changes the direction of the frequency tuning of the generator 1, which is triangularly modulated within the passband of the piezo emitter (plots 20, 21). Ultrasonic waves reach the piezoelectric receiver 5 with a delay equal to the travel time of the distance between the transducers, therefore a beat signal is emitted at the mixer output, i.e. a sequence of pulses modulated by a beat signal (Figure 22). The shaper 12 produces pulses from the beat signal equal in duration to a given integer number of 25 beat half-periods (graph 23). These pulses are inverted by inverter 13 (graph 24). At the moment of the appearance of a certain impulse of the block 7, the control unit 9 starts the counter 8, 30

counting the pulses of the block 7. At the same time, the control unit 9 outputs a resolving level to the matching circuits 14 and 15. The circuit 15 receives the resolving level of the trigger 10. In this way, the output of the circuit 15 during each pulse of the inverter 13 produces a level that through the collecting circuit 16 Includes key 17 digital integrator. The counter 19, rear, adds up the pulses coming from the output of modulator 2 (plot 26). The process proceeds as described above, until the moment when the specified number η of pulses from block 7 is counted by counter 8. The output pulse of indicator-counter 8 flips trigger 10. The signals of trigger 10 switch mode switch 18 to the subtraction position, the enabling level is removed from the input of circuit 16, and on the contrary, this level is fed to the circuit 14 .. At the output of the collecting circuit 16, the level, which closes the key 17, is now obtained during the pulses of the driver 12 (see Fig. 55). The measurement ends when the contents of the reversible counter 19 is reduced to zero and the counter 19 outputs a pulse to the control unit 9.

During η pulses of block 7, the digital integrator counter 19 gains a sum of pulses proportional to (T-e) p, where T is the period of a single frequency tuning of the generator 1, 65

those. pulse repetition period of block 7; - with the duration of the output pulses of the driver 12. With each successive period T, the contents of counter 19 decrease and become zero after w periods, i.e. (T-) l =

"ь. Hence we find that the indications of the indicator-counter 8 at the end of the measurement can be calculated by the formula

w + n = (1)

On the other hand, the quality factor O of the piezo emitter 3 is associated with the density p of the medium under study by the following dependence;

or ; (2)

· * C £ _o

where is the resonant frequency of the piezo emitter;

its bandwidth; ultrasound velocity in the test medium;

coefficient of proportionality.

In turn, the bandwidth & G at a constant rate of change of frequency is proportional to the period T: Db = = k _g T. The interval "c is associated with the speed by the following relationship: c = k _e с syo ₁ where V is the distance between the piezo transducers. Substituting these relations in the formula (2), we get

(h)

From the formula (1) and (2) it can be seen that the indications of the indicator-counter 8 with the appropriate selection of the values included in the formula (3) are equal to the digital density value in certain units.

The absorption of ultrasound is reflected only in the amplitude of the signal of the amplifier, but not at the frequency that is the carrier of information. The speed of ultrasound in the medium is automatically taken into account, since the period of beats at the mixer output is directly proportional to the speed.

Claims (1)

Claim A device for measuring the density of liquid media, consisting of a series-connected modulated signal generator, an emulator camera with transducers, an amplifier, a 0.707 level detection unit, an indicator, a counter, the input of which is connected to the first input of the control unit and the first control input of the modulated signal generator, and shaper, characterized in that, in order to expand the range of measured densities and ensure digital pickup of the signal, a digital input is introduced 757922 tegrator, mixer, first and second elements AND, element OR, inverter and trigger, the input 'of which is connected to the first output of the meter indicator, the second input and the second output of which are connected respectively to the first output and the second input of the control unit, the second output of which is connected with the first inputs of the first and second elements And, the second inputs of which are connected respectively to the first and second outputs of the trigger, while the third inputs of the elements And are connected respectively to the input and output of the inverter, to the input of which is connected the output driver, the input of which is connected to the output of the mixer, the first input of which is connected to the output of the amplifier, and the second input of the mixer is connected to the second output of the modulated generator signals, the outputs of the first and second elements And are connected respectively to the first and second inputs of the OR element, the output of which is connected to the first control input of the digital integrator, whose information input is connected to the third output of the modulated signal generator, and the second input of the first And element is connected to the second Ιβ control input of a digital integrator, the output of which is connected to the third input of the control unit.