The method of calibration of hydrophones

 

(57) Abstract:

The method of calibration of hydrophones is implemented by a device containing a measuring chamber with water, in which is fixed a calibrated hydrophones. The measuring chamber is connected by a flexible hose with an auxiliary vessel with water. When periodic sinusoidal movement of the auxiliary vessel in the vertical direction by means of an electrical actuator in the measuring chamber occasional change of pressure, which is converted into an output signal. Along with hydrostatic pressure, which is calculated by a simple formula, the hydrophone operates another component of the pressure caused by the inertia. This component determines the accuracy of the calibration. The inertial component depends on the frequency of oscillation of the auxiliary receptacle and opposite in sign to the hydrostatic pressure. So at a certain frequency they compensate each other and the output of the hydrophone will be a zero signal. The resulting value of the zero frequency signal is substituted in the formula of measurement to determine the calibration factor. Because of the frequency measurements are the most precision, the calibration of geetali, this allows you to automate the process of absolute calibration of hydrophones, which also increases the reproducibility of the results of calibration. 1 Il.

The invention relates to the field of hydroacoustic measurements of infrasound frequencies and can be used for absolute calibration of hydrophones.

There is a method of calibration of hydrophones in the infrasonic frequency by vertical, sinusoidal oscillations under a free surface of the stationary fluid. Periodic changes in the depth of the hydrophone lead to the influence of an alternating hydrostatic pressure (Golenkov A. N. "Absolute calibration of the receivers infrasonic pressure", J. Measuring range. technology. N 5, 1965, S. 42).

This method of calibration has poor accuracy due to the presence of relative displacement of environment and hydrophone with low-precision measurements of the depth of the dive.

The closest technical solution of the present invention is a method of calibration of hydrophones, based on the fact that in a stationary measuring chamber with water fix calibrated hydrophones and is connected to the measuring chamber of the auxiliary vessel with flexible t the th components in this way the calibration is carried out by changes in water level followed by its dimension (Cm. Golenkov A. N. "Absolute calibration of the receivers infrasonic pressure", J. Measuring range. t., N 5, 1965, S. 43).

This method has poor accuracy due to the additional error of measurement of water levels.

The aim of the present invention is to improve the accuracy of the calibration of hydrophones at infrasonic frequencies.

The method involves measuring the amplitude of the vertical displacement hoauxiliary vessel with water relative to the measuring chamber with the hydrophone, then determine the frequency fomove auxiliary vessel, in which the output signal of the hydrophone U is equal to zero, and the calibration coefficient M of the hydrophone at the frequency f is determined from the ratio

(1)

where q is the acceleration of free fall,

- the density of water,

fpresonance frequency of the camera with auxiliary vessel.

The figure schematically depicts a device implementing the invention.

In the measuring chamber 1 is fixed hydrophones 2 connected to device 3 output signal U. the Measuring chamber by a flexible hose 4 is connected to the auxiliary vessel 5, which performs sinusoidal.

Uscsa water, auxiliary vessel 5 by the action of the actuator begins to perform sinusoidal oscillations having a vertical component, the value of which howhen this shall take readings of the output signal U of the hydrophone 2 using a recording device 3. Changing the frequency f of the sinusoidal oscillations of the auxiliary vessel 5, to achieve the zero value of the output signal of the hydrophone, locking the oscillation frequency of the auxiliary vessel foin which the inertial component of the pressure changes in the measuring chamber is completely compensated by the hydrostatic pressure. After that, the hydrophone graduate on any frequency range, and calibration factor M is determined from the relation (1).

The proposed method for the calibration of hydrophones has high accuracy due to the fact that the frequency of the zero signal foquickly determined with negligible error, and because the calibration process is simple to implement, it allows you to automate the process of absolute calibration of hydrophones, which also increases the reproducibility of the results of calibration.

The method of calibration of hydrophones, which consists in measuring the amplitude of Verona, characterized in that, to improve calibration accuracy, determine the frequency faboutmove auxiliary vessel, in which the output signal of the hydrophone U is equal to zero, then the calibration factor M of the hydrophone at the frequency f is determined from the ratio

< / BR>
where q is the acceleration of free fall;

is water density;

fpresonance frequency of the system consisting of the measuring chamber and the auxiliary vessel.

 

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