CN102661781A - Sensitivity testing apparatus for hydrophone - Google Patents

Abstract

The invention belongs to the underwater sensing field, and especially relates to a sensitivity testing apparatus for a hydrophone. The apparatus comprises a shake table, a rigid wall circular pipe containing a measure medium, an accelerometer, a support and a computer, wherein one end of the rigid wall circular pipe is open and the bottom of the rigid wall circular pipe is fixedly connected onto the shake table and is fixed with the accelerometer. The hydrophone which needs to be tested is hanged on the support and perpendicularly hanged on central axis of a liquid column of a container. The computer controls the shake table through a signal-generator and a power amplifier. An output signal of the accelerometer and an output signal of the hydrophone which needs to be tested are sent into the computer after conditioning respectively by two signal conditioning circuits. The computer computes the sensitivity of the hydrophone based on the value of the two input signals. The invention can reduce the error range and raise the accuracy of sensitivity testing.

Description

A kind of nautical receiving set sensibility testing arrangement

Technical field

The invention belongs to underwater sound sensory field, particularly relate to a kind of nautical receiving set sensibility testing arrangement.

Technical background

Nautical receiving set is called underwater microphone again; Be underwater signal change into electric signal transducer; According to the difference of action principle, transduction principle, characteristic and structure etc., the branch of acoustic pressure, vibration velocity, undirected, sensing, piezoelectricity, magnetostriction, electronic nautical receiving sets such as (moving-coils) is arranged.Nautical receiving set and microphone have a lot of similarities on principle, performance, but because the difference of sound bearing medium, nautical receiving set has firm waterproof structure, and must adopt the water-proof cable of corrosion-resistant material.

Nautical receiving set is as using the most extensive, most important a kind of device in the underwater acoustics; In being usually used in sea floor exploration equipment and various cable machinery; These equipment require therefore before nautical receiving set uses, need test its sound pressure sensitivity than higher to its sound pressure sensitivity.

Common method is a relative method in the acoustic pressure sensitivity of hydrophone method of testing; Relatively ratio juris is: the sensitivity of an at first known standard hydrophone; Signal generator provides the signal of different frequency and amplitude for sound case (above be a vertical cylinder); Fixing prime amplifier above the cylinder of sound case, the output terminal of prime amplifier connects oscillograph.Under the signal of certain frequency and amplitude; At first put into cylinder to standard hydrophone; Write down the amplitude of signal through oscillograph, put into cylinder (height is consistent with the height that standard hydrophone is placed) to nautical receiving set to be measured then, write down the amplitude of signal through oscillograph; Just can calculate the sensitivity of nautical receiving set to be measured according to formula through the range value that measures for this twice; General for accuracy can be provided with several different frequencies more, calculate several times Sensitirity va1ue more and average then, draw the sensitivity of nautical receiving set to be measured.The defective of relative method is that accuracy is low; Because the test height of nautical receiving set to be measured and standard hydrophone must be consistent, just have comparability, and can there be error highly usually in this; But also need under lab to accomplish sensitivity test by oscillograph, there is inconvenient part.

Summary of the invention

Based on above problem, it is good that the present invention proposes a kind of accuracy, and volume compact is convenient to portable nautical receiving set sensibility testing arrangement.Technical scheme of the present invention is following:

Claims

A kind of nautical receiving set sensibility testing arrangement; The involving vibrations platform, in fill rigid walls pipe, accelerometer, support, capture card and the computing machine of measuring medium, wherein, an end opening of rigid walls pipe; The bottom is connected on the shaking table; And be fixed with an accelerometer, need the nautical receiving set of measurement sensitivity to be suspended on the support, and vertically hang on the central axis of fluid column in the container; Computing machine is through signal generator and power amplifier control Vib.; The output signal of accelerometer and need the output signal of the nautical receiving set of measurement sensitivity to become digital signal through capture card after the conditioning through two signal conditioning circuits respectively; Be transferred to computing machine through usb bus, computing machine calculates the sensitivity of nautical receiving set according to the size of two input signals.

Above-mentioned proving installation, when low frequency, according to

Calculate the sensitivity of nautical receiving set; When high frequency, according to $M_j=\frac{M_a}{\mathrm{\ρ\; h}}\×\frac{U_J}{U_a}\left(\frac{\mathrm{Kh}\mathrm{Cos}\mathrm{Kl}}{\mathrm{Sin}\mathrm{Kh}}\right)$ Calculate the sensitivity of nautical receiving set,

In the formula: M _j---the sound pressure sensitivity of nautical receiving set;

U _J---the open-circuit voltage of nautical receiving set output terminal;

ρ---density of liquid;

H---the degree of depth of the nautical receiving set acoustic centre of source to liquid level;

M _a---the sensitivity of accelerometer;

U _a---the open-circuit voltage of accelerometer output terminal;

K---wave number (=w/c, w=2 π f);

The frequency of f---liquid vibration;

C---the velocity of sound in the fluid column;

The height of l---fluid column.

Proving installation of the present invention; Method relatively, without the amplitude of measurement standard nautical receiving set output signal, the output voltage of directly testing nautical receiving set to be measured just can be in the hope of its Sensitirity va1ue; So just lacked the link of a step through the oscillograph reading; Because can have certain error in the time of through the oscillograph reading, thereby dwindle error range, improve the accuracy of sensitivity test.Simultaneously also lacked the link of comparing, improved testing efficiency with standard hydrophone.

Description of drawings

Fig. 1 is the structural representation of the fluid column test container of nautical receiving set sensibility testing arrangement employing of the present invention.

Fig. 2 is the structured flowchart of the circuit part of nautical receiving set sensibility testing arrangement of the present invention.

Embodiment

Below in conjunction with accompanying drawing and embodiment, the present invention is done explanation.

Referring to Fig. 1, nautical receiving set sensibility testing arrangement of the present invention at first comprises a fluid column test container that is placed on the shaking table 6; It comprises internal diameter liquid wave length of sound in the pipe; The rigid walls pipe 1 of one end opening, in fill certain altitude liquid as measuring medium, whole fluid column test container is driven by shaking table 6 that can sinusoidal vibration; Need the nautical receiving set 3 of measurement sensitivity be suspended on a support on, and vertically hang on the central axis of fluid column in the container.Be fixedly connected through flange 4 between the bottom of shaking table 6 and rigid walls pipe 1.At accelerometer of the bottom of rigid walls pipe 1 fixed installation; Be used for measuring the acceleration of rigid walls pipe 1; When rigid walls pipe 1 vibrates with shaking table 6; The acoustic pressure of nautical receiving set 3 positions changes, and this acoustic pressure can be calculated through formula by height, the nautical receiving set degree of depth and the accelerometer of fluid column.Measuring principle is following:

Suppose that whole fluid column does vertical vibration integrally with respect to its equilibrium position, then the degree of depth is the h place under the liquid level, and the acoustic pressure p that is produced by pressure change is:

p＝ρx|g-hw ²| (1)

w＝2πf

In the formula: ρ---fluid density, kg/m ³

The vibration displacement of x---container bottom, m;

G---acceleration of gravity, m/s ²

The frequency of f---liquid vibration, Hz;

When frequency high to making: hw ²＞＞g, then formula (1) becomes:

In the formula: ---the vibration acceleration of container bottom, m/s ²

If the vibration acceleration of container bottom is measured with accelerometer, the sound pressure sensitivity that then can get nautical receiving set by formula (2) is:

$M_j=\frac{U_J}{\mathrm{\ρh}}\×\frac{M_a}{U_a}---\left(3\right)$

When high frequency, the acoustic pressure in the fluid column is:

Then formula (3) should be:

$M_j=\frac{M_a}{\mathrm{\ρh}}\×\frac{U_J}{U_a}\left(\frac{\mathrm{kh}\cos \mathrm{kl}}{\sin \mathrm{kh}}\right)---\left(5\right)$

In the formula: M _j---the sound pressure sensitivity of nautical receiving set, V/P _a

U _J---the open-circuit voltage of nautical receiving set output terminal, V;

ρ---density of liquid, kg/m ³

H---the degree of depth of the nautical receiving set acoustic centre of source to liquid level, m;

M _a---the sensitivity of accelerometer, Vs ²/ m;

U _a---the open-circuit voltage of accelerometer output terminal, V;

K---wave number (=w/c, w=2 π f), m ^-1

The frequency of f---liquid vibration, H _z

C---the velocity of sound in the fluid column, m/s;

The height of l---fluid column, m.

By on can know, the pressure change that the sound pressure sensitivity of nautical receiving set can belong to fluid column degree of depth place according to nautical receiving set with record the nautical receiving set output terminal the ratio of open-circuit voltage (when the nautical receiving set output terminal does not have electric current to flow out, the instantaneous voltage that appears at this point) obtain.Concrete circuit design is: the frequency of being controlled shaking table by computing machine through signal generator and power amplifier; The output voltage of accelerometer modification amplifier and tested nautical receiving set open-circuit voltage are respectively through after the amplification and filtering of two signal conditioning circuits; Be transferred to computing machine through capture card again, according to formula (3) or (5) (adopting a back formula in the time of the above high frequency of 2kHz) meter sensitivity.

The prime amplifier that signal conditioning circuit adopted of nautical receiving set of the present invention is: differential signal amplifier, common-mode rejection ratio are greater than 110dB, and the short circuit noise is less than 1uV; Direct current offset is less than 10Uv; Capture card adopts independently binary channels synchronous collecting card, and sampling precision is 24, and the amplitude of the smallest effective signal that can collect has reached 0.5uV; Sampling rate is 500KS/s, interchannel crosstalking less than-100dB.The interface of capture card and computing machine is a USB interface, supports hot plug, the convenient connection, has improved work efficiency.

Claims (2)

1. nautical receiving set sensibility testing arrangement; The involving vibrations platform, in fill rigid walls pipe, accelerometer, support and the computing machine of measuring medium, wherein, an end opening of rigid walls pipe; The bottom is connected on the shaking table; And be fixed with an accelerometer, need the nautical receiving set of measurement sensitivity to be suspended on the support, and vertically hang on the central axis of fluid column in the container; Computing machine is through signal generator and power amplifier control shaking table; The output signal of accelerometer and need the output signal of the nautical receiving set of measurement sensitivity to be admitted to computing machine after the processing through two signal conditioning circuits respectively, computing machine calculate the sensitivity of nautical receiving sets according to two input signals.

2. nautical receiving set sensibility testing arrangement according to claim 1; It is characterized in that; When low frequency, calculate the sensitivity of nautical receiving set according to ; When high frequency; Calculate the sensitivity of nautical receiving set according to

In the formula: M _j---the sound pressure sensitivity of nautical receiving set;

U _J---the open-circuit voltage of nautical receiving set output terminal;

ρ---density of liquid;

H---the degree of depth of the nautical receiving set acoustic centre of source to liquid level;

M _a---the sensitivity of accelerometer;

U _a---the open-circuit voltage of accelerometer output terminal;

K---wave number (=w/c, w=2 π f);

The frequency of f---liquid vibration;

C---the velocity of sound in the fluid column;

The height of l---fluid column.

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