RU2244270C1 - Device for measuring sound speed in liquid environment - Google Patents

Abstract

FIELD: acoustic measurements.

SUBSTANCE: device has acoustic transmitting converter, one reflector, power amplifier and preliminary amplifier, input of which is connected to power amplifier output and connected to transformer. Additionally inserted are second reflector, generator, strobe generator, comparator, microcontroller, temperature sensor and display. First, second and third inputs of generator are connected respectively to comparator output, first input of which is connected to output of preliminary amplifier, first input of strobe generator being connected concurrently to second output of generator and to one of microcontroller inputs, other its input is connected to temperature sensor, second input of strobe generator is connected to second output of microcontroller, third output of which is connected to display input. First and second reflectors are made in form of plates rigidly fixed on same base with transmitting converter and in parallel to it, perpendicularly to plane of base and symmetrically relatively to line on base plane, parallel to axis of direction diagram. Area of reflection of second reflector surpasses, by height, first reflector in no less then two times.

EFFECT: higher precision.

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Description

The invention relates to acoustic measurements and can be used to determine the speed of sound in liquids and water in studies of the oceans on moving objects, as well as in current liquids and bulk media.

A device for measuring the speed of sound (AES) [1, p. 83-84], based on the fact that when the acoustic signal is emitted into the studied liquid medium between the transducer and the reflector located at a distance L ₁ , a standing sound wave is set at a frequency f, then the reflector is moved a distance l _k and N peaks or minima of the standing wave are counted, and the speed of sound is determined by the formula

The disadvantage of this device is the need to search and install the reflector in a position in which there is a maximum or minimum of a standing sound wave during each measurement, which makes it impossible to use digital methods for processing sound velocity measurements and automate the process, and also reduces the performance and accuracy of the measurement process.

The device closest in structure is an AES based on the ring method of measuring the pulse repetition rate F, Hz, determined by the formula [2, p. 107]

where L is the distance between the emitter-receiver and the reflector, m;

C is the speed of sound in a liquid medium, m / s;

τ _s - the time delay of the pulses in the electrical circuits of the sound velocity meter, s.

The disadvantage of this prototype device is the presence of an additional time delay τ _s , which introduces an error in the value of the speed of sound and leads to a nonlinear dependence of the pulse repetition rate on the speed of sound.

The objective of the present invention is to improve the accuracy of measuring the speed of sound in a liquid medium.

The essence of the claimed invention lies in the fact that in the satellite selected as a prototype and containing an acoustic transceiver, a first reflector, a power amplifier and a preliminary amplifier, the input of which is connected to the output of the power amplifier and connected to the converter, a second reflector, generator, generator are additionally introduced strobe, comparator, microcontroller, temperature sensor and display, and the first, second and third inputs of the generator are connected respectively to the output of the comparator, the first output m of the microcontroller and the first output of the strobe generator, the second output of which is connected to the input of the comparator of the same name, the first input of which is connected to the output of the pre-amplifier, the first input of the strobe generator is connected simultaneously with the second output of the generator and one of the inputs of the microcontroller, its other input is connected to the temperature sensor, the second input of the strobe generator is connected to the second output of the microcontroller, the third output of which is connected to the display input.

The first and second reflectors are made in the form of plates rigidly mounted on one base with a transceiver and parallel to it, perpendicular to the plane of the base and symmetrically with respect to the line on the base plane parallel to the axis of the radiation pattern, while the reflection area of the second reflector exceeds the first reflector in height not less than than twice.

Figure 1 shows a functional diagram of the inventive meter of sound speed, where the following notation:

1 - power amplifier;

2 - acoustic transceiver;

3 - the first reflector;

4 - pre-amplifier;

5 - second reflector;

6 - base;

7 - generator;

8 - strobe generator;

9 - a comparator;

10 - microcontroller;

11 - medium temperature sensor;

12 - display.

Figure 2 shows a functional diagram of a speed meter of sound - a prototype of the invention, where the following notation:

1 - power amplifier;

2 - acoustic transceiver;

3 - reflector;

4 - pre-amplifier;

5 - key;

6 - multivibrator.

The operation of the sound velocity meter includes three stages.

At the first stage, when power is supplied from the microcontroller 10 to the generator 7, a program start command is received, and to the strobe generator 8, a command determines the length of the strobe, i.e. by what reflector will auto-circulation take place. The generator 7 generates a probe pulse with a high-frequency filling and starts the strobe generator 8. The probe pulse is supplied to a power amplifier 1 and then to a converter 2 for radiation into the medium under investigation. The acoustic signal from the transducer 2 passes the path to the first reflector 3 and, reflected from it, goes to the transducer 2 and to the pre-amplifier 4 for filtering and amplification. The amplified signal is fed to the comparator 9, gated by a pulse from the gate generator 8. The comparator 9 compares the signal amplitude with the reference voltage and, when it exceeds the reference voltage, switches and thereby triggers the formation of the probe signal in the generator 7. Then the radiation again occurs and the auto-circulation process is established . The output signal from the strobe generator 8 allows the signal to pass from the comparator 9 to the generator 7 only after the expected arrival time of the signal and thereby prevents interference and repeatedly reflected signals from disrupting the auto-circulation process.

The expected time of arrival of the signal T _ozh , s, is determined by the formula

where L _{1 (2)} is the distance from the transducer 2 to the reflector 3 (5) (first or second), m;

With _sounds - the maximum specified value of the speed of sound in the medium, m / s.

After the autocirculation process is established, the microcontroller calculates the period of the probe pulses by the autocirculation frequency from the first and second reflectors.

When reflected from the first reflector (first stage)

where t _L1 is the propagation time of the acoustic signal in the medium from the emitter to the first reflector and further to the receiving transducer;

τ _s - time delays in all electrical circuits and devices of the satellite.

Then, at the second stage, the microcontroller programs the strobe generator for autocirculation by the second reflector and, like the process described above, the period of the probe pulse is measured during autocirculation by the second reflector T ₂

T ₂ = T _L2 + τ _s

where T _L2 is the propagation time of the acoustic signal in the medium from the emitter to the second reflector and further to the receiving transducer.

At the third stage, the microcontroller starts calculating the speed of sound. The distance between the first and second reflectors (acoustic base L) is measured and its value is recorded in the memory of the microcontroller. The difference between the periods of the probe pulse during autocirculation in the first and second reflectors depends only on the parameters of the medium, i.e. from the speed of sound in it.

T = T ₂ -T ₁ = T _L2 -T _L1

Delays in electrical circuits automatic circulation ring subtracted and are excluded from the calculation formula of the sound velocity C _ulcers

where L is the distance from the first reflector to the second reflector.

Since the base material is subject to linear expansion due to temperature fluctuations, at the third stage the microcontroller receives information from the temperature sensor about the temperature of the medium under study and calculates it. Therefore, taking into account the temperature of the medium, the formula for calculating the speed of sound C _sv , m / s, takes the form

where α is the coefficient of linear expansion of the base material, 1 / ° C;

t is the temperature of the medium, ° C;

K is the temperature at which the length of the acoustic base was measured, i.e. the distance between the first and second reflector, ° C.

After calculating the speed of sound, the microcontroller displays its value on the display.

The power amplifier 1 is made traditionally [4, p. 28, fig. 1.22, 1.23].

Acoustic transducer 2 is an oscillatory structure with a flat piezoceramic plate [3, p.104-109].

The first and second reflectors 3, 5 are made in the form of plates rigidly mounted plane-parallel on one base 6 with a transceiver 1.

The preamplifier 4 contains an amplifier with a bandpass filter and is made traditionally [4, p. 219, Fig. 7.12].

Generator 7 contains a pulse generator, a high-frequency generator for filling pulses, made traditionally [4, p.134, Fig.4.5, p.147, Fig.4.15].

The strobe generator 8 is made traditionally [5, p.274, Fig.6.83].

The comparator 9 is made traditionally [4, p.159, Fig.5.5].

Microcontroller 10 is a chip type 80C51 from Intel or similar, which is a single-chip microcomputer with a set of different interfaces.

The temperature sensor 11 has a frequency output and is made on a chip TMP04 firm Analog Devices.

Display 12 is a traditional LCD.

The use of the proposed sound velocity meter eliminates the influence of errors in the measurement of sound speed caused by a time delay in the electrical circuits of the satellite. The accuracy of measuring the speed of sound depends only on the accuracy of the installation and measuring the distance between the first and second reflectors.

The proposed satellite allows you to exclude the process of calibration of the product and reduce the complexity of maintenance during operation.

The absence of the influence of the delay time in the electrical circuits τ _s allows you to choose a lower satellite operating frequency than in a ring-based satellite, and thereby increase the permissible cable length between the converter and the satellite’s hardware without losing the useful signal.

The proposed satellite can be operated on moving objects or measure the speed of sound in flowing liquids, since the influence of the Doppler effect on the measurement accuracy is excluded.

The automatic measurement process allows you to remotely and programmatically control the operation of the satellite.

Literature

1. Nosov V.A. Design of ultrasonic measuring equipment. Moscow, Mechanical Engineering, 1972

2. Yu.F. Tarasyuk, G.N. Seravin. Hydroacoustic telemetry. Leningrad, Shipbuilding, 1973

3. Underwater electro-acoustic transducers. Ed. V.V. Bogorodsky. Directory. Leningrad, Shipbuilding, 1983

4. A.G. Alekseenko, E.A. Kolombet, G.I. Starodub. The use of precision analog microcircuits. Moscow, Radio and Communications, 1985

5. Yu.N. Erofeev. Impulse technique. Moscow, Higher School, 1984

Claims (1)

A sound velocity meter in a liquid medium containing an acoustic transceiver and a first reflector, a power amplifier and a pre-amplifier, the input of which is connected to the output of a power amplifier, which is connected to the converter, characterized in that a second reflector, a generator, a strobe generator, a comparator are inserted into it , a microcontroller, a temperature sensor and a display, and the first, second and third inputs of the generator are connected respectively to the output of the comparator, the first output of the microcontroller and the first the output of the strobe generator, the second output of which is connected to the input of the comparator of the same name, the first input of which is connected to the output of the pre-amplifier, the first input of the strobe generator is connected simultaneously with the second output of the generator and one of the inputs of the microcontroller, its other input is connected to the temperature sensor, the second input of the strobe generator connected to the second output of the microcontroller, the third output of which is connected to the input of the display, the first and second reflectors are made in the form of plates rigidly fixed to one with a transceiver transducer and parallel to it, perpendicular to the plane of the base and symmetrically with respect to a line on the base plane parallel to the axis of the radiation pattern, while the reflection area of the second reflector is at least twice as high as the first reflector.

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