RU2814647C1 - Device for calibrating hydroacoustic receivers in small-volume chamber using parametric resonance - Google Patents

Abstract

FIELD: measurement.

SUBSTANCE: invention relates to measuring equipment, namely to devices for measuring sensitivity of electromechanical transducers in a small-volume chamber based on parametric resonance of standing waves. Device for calibrating hydroacoustic receivers in a small-volume chamber using parametric resonance comprises a vertical-type small-volume chamber, made with possibility of placing in it a calibrated hydroacoustic receiver and its fixation on coordinate device, signal from which is transmitted through an amplifier and a low-pass filter to a voltmeter and an analogue-to-digital converter (ADC) connected to a PC. An accelerometer is additionally attached to the lower end of the small-volume chamber, which is connected to the ADC, which provides measurement of the oscillation frequency in the small-volume chamber.

EFFECT: increased volume of working space, reduced irregularity of hydroacoustic field and increased accuracy of oscillations formation in chamber of small volume.

1 cl, 1 dwg

Description

The invention relates to measuring technology, namely to installations for measuring the sensitivity of electromechanical transducers in a small volume chamber based on parametric resonance of standing waves.

A known installation is a non-standardized installation UVG-1 (Gordienko V.A. Vector-phase methods in acoustics. - M.: FIZMATLIT, 2007. - 480 pp. - ISBN 978-5-9221-0864-5), taken as a prototype, designed for calibration of vector receivers and sound pressure receivers (hydrophones) using the absolute method in a vertically oscillating column of liquid. The installation includes a working chamber in the form of a section of a vertical pipe with a feedback hydrophone installed in it, amplifiers, narrow-band filters, a phase meter, a voltmeter, a feedback circuit regulator, a generator, a digital program unit, a power amplifier, a vibration exciter and a PC with an analog-to-digital circuit board. converter (ADC).

The base of the chamber is a rigid piston, the excitation of which is carried out using an electrodynamic vibration exciter.

A coordinate device is used to secure a calibrated vector receiver or sound pressure receiver and move it in the vertical and horizontal directions.

The main disadvantages of the installation are: limitation of the working space and unevenness of the hydroacoustic field of a small volume chamber due to the presence of a feedback hydrophone in it, and the presence of nonlinear elements in the generator circuit for generating oscillations of the vibration exciter.

A new technical solution is aimed at eliminating these shortcomings: an installation for calibrating hydroacoustic receivers in a small-volume chamber using parametric resonance, the technical task of which is to increase the working space of the small-volume chamber, reduce the unevenness of the hydroacoustic field of the small-volume chamber and increase the accuracy of the generated oscillations in the small-volume chamber.

An accelerometer can be used as a device for measuring the vibration exciter frequency. An accelerometer is a converter of mechanical vibrations into an electrical signal proportional to vibration acceleration. Inside the accelerometer is a mass attached to a spring or other elastic element. As the vibration of an object changes, the mass shifts, causing a change in some physical parameter (such as resistance, capacitance, inductance, or an optical signal), which is then converted into an electrical signal proportional to the acceleration. The frequency and other frequency characteristics are measured from the received signal. Frequency range from 0 to 1/3 of the accelerometer resonant frequency (typically 30 kHz). they have linear amplitude sensitivity in the operating range and operate stably for a long time.

There are 2 ways of external influence on the oscillatory system: force and parametric.

A classic example of force acting on an LC circuit is a generator connected to the circuit circuit. It sets oscillations at a certain frequency p with the occurrence of forced oscillations in the LC circuit.

Parametric action is characterized by a periodic change in any parameter of the system, as a result of which reactive energy arises.

A parametric generator is used to excite resonant oscillations in the system. This allows you to isolate the excitation circuit of the emitter from various frequency components caused by the presence of nonlinear elements in the system and increase the accuracy of the generated signals.

The principle of operation of a parametric generator is that an additional capacitor with a nominal value three times larger than a similar element of the circuit is connected to the main oscillatory circuit using thyristors, which changes the parameters of this circuit during each oscillation depending on the presence of a positive control voltage on the thyristors supplied on them at the moment of maximum current and removed at its zero value. In this case, the duration of the positive control voltage pulse for the additional capacitance is half the period of the main oscillation frequency of the circuit, and the duration of the negative pulse in both capacitors is a quarter of this period to create periodic changes in the circuit parameters during each oscillation and, thereby contributing to the excitation of parametric resonance and generation electrical power in the device. The source of oscillations is completely functionally independent of the influence of any external forces or the attraction of other types of energy.

The implementation of the task allows us to achieve the following total technical result:

- increasing the volume of the working space and reducing the unevenness of the hydroacoustic field in a small-volume chamber;

- increasing the accuracy of generated vibrations in a small-volume chamber through the use of a parametric generator.

The specified technical result is achieved by the fact that the claimed Installation for calibrating hydroacoustic receivers in a small-volume chamber using parametric resonance contains a small-volume vertical-type chamber, made with the possibility of placing a calibrated hydroacoustic receiver in it, and fixing it on a coordinate device, the signal from which is transmitted through an amplifier and the low-pass filter is supplied to a voltmeter and an analog-to-digital converter (ADC), connected to a PC, which controls, through a digital program unit, a parametric generator connected to a vibration exciter and ADC.

The fundamental difference between the claimed invention and the prototype is that an accelerometer is additionally attached to the lower end of the small-volume chamber, connected to an ADC, which provides measurement of the oscillation frequency in the small-volume chamber.

The essence of the invention is illustrated by the drawing:

Fig. 1 Installations for calibrating hydroacoustic receivers in a small-volume chamber using parametric resonance. Functional diagram.

In fig. Figure 1 shows a functional diagram of the Installation for calibrating hydroacoustic receivers in a small volume chamber using parametric resonance.

Installation includes:

1. Small volume chamber.

2. Calibrated hydroacoustic receiver.

3. Amplifier.

4. Low pass filter (LPF).

5. Voltmeter.

6. Analog-to-digital converter (ADC).

7. PC.

8. Digital program block.

9. Parametric generator.

10. Vibration exciter.

11. Accelerometer.

12. Coordinate device.

All blocks are connected by electrical connections.

The calibrated hydroacoustic receiver 2 is placed in a small volume chamber 1 of a vertical type and mounted on a coordinate device 12.

The calibrated hydroacoustic receiver 2 is connected through an amplifier 3 and a low-pass filter 4 to a voltmeter 5 and an ADC 6. An ADC 6 is connected to a PC 7, which controls a parametric generator 9 through a digital program unit 8. The outputs of a parametric generator 9 are connected to an ADC 6 and a vibration exciter 10, which forms a hydroacoustic field in a small volume chamber 1. The signal from the accelerometer 11 is supplied to the PC 7 through the ADC 6.

The device works as follows.

The hydroacoustic receiver 2 under study is placed in a small volume chamber 1 and fixed to a coordinate device 12.

From the PC 7, a start signal and a signal of vibration parameters are supplied through a digital program unit 8 to a parametric generator 9. The parametric generator 9 is started and generates highly stable electrical oscillations, which are supplied to the vibration exciter 10.

The vibration exciter 10 converts electrical vibrations into mechanical ones, thereby generating vibrations in the liquid column in the small volume chamber 1. A hydroacoustic field of a standing wave is formed in small volume chamber 1. Accelerometer 11 measures the vibration acceleration of the lower end of small volume chamber 1. The signal from accelerometer 11 is fed to ADC 6 and then to PC 7, in which the hydroacoustic field of a standing wave in small volume chamber 1 is calculated.

The signal from the calibrated hydroacoustic receiver 2 is amplified by the amplifier 3. Then it is fed to the input of the low-pass filter 4. Next, it is recorded by the voltmeter 5 and goes to the input of the ADC 6 for further processing on the PC 7.

During the measurement cycle, a discrete change in frequencies is carried out using a digital program unit 8 controlled by a PC 7.

Using a PC 7, the signal frequency and harmonic level are determined, and the characteristics of the hydroacoustic field of a standing wave in a small volume chamber 1 are calculated from the oscillation frequency value recorded by the accelerometer 11 and the height of the liquid column:

where p is the amplitude of sound pressure;

u - oscillatory speed;

d - distance from the water surface;

- wave resistance;

ρ - density of water;

c is the speed of sound in water;

k is the wave number, which is calculated by the formula:

where λ is wavelength;

ƒ - vibration frequency measured by the accelerometer.

By placing the calibrated hydroacoustic receiver 2 at a depth d and measuring its output voltage U, we obtain the ratios for its sensitivity in units:

- equivalent sound pressure of a plane traveling wave:

- oscillatory acceleration for the pressure gradient receiver (PGD):

- oscillatory speed:

where: P _d =P _o ⋅p(d) - calculated absolute value of sound pressure at depth d;

- calculated absolute value of the oscillatory velocity at depth d.

At low frequencies, the calibrated hydroacoustic receiver 2 is subject to additional acoustic pressure caused by fluctuations in hydrostatic pressure. Therefore, when calibrating a hydroacoustic receiver (hydrophone), a correction factor should be entered

The absolute value of pressure P _o at a depth d _o is determined once during metrological certification of the installation using a standard first-class measuring hydrophone.

The technical result of the invention is to create a new device “Installation for calibrating hydroacoustic receivers in a small-volume chamber using parametric resonance,” which allows to increase the working space of a small-volume chamber, reduce the unevenness of the hydroacoustic field of a small-volume chamber and increase the accuracy of the generated oscillations in a small-volume chamber.

The claimed installation is industrially applicable, since in its manufacture widespread devices and components can be used, such as: PC, accelerometer, small-volume camera, vibration exciter, ULF, low-pass filter.

Claims (1)

An installation for calibrating hydroacoustic receivers in a small-volume chamber using parametric resonance, containing a small-volume vertical-type chamber designed to accommodate a calibrated hydroacoustic receiver in it and attach it to a coordinate device, the signal from which is fed through an amplifier and a low-pass filter to a voltmeter and an analog-to-digital converter (ADC) connected to a PC, which controls, through a digital program unit, a parametric generator connected to a vibration exciter and an ADC, characterized in that an accelerometer is additionally attached to the lower end of the small-volume chamber, connected to an ADC, which provides measurement of the oscillation frequency in a small volume chamber.

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