SU932654A2 - Method of absolute graduation of hydrophones in chambers controlled by elastic mass impedance - Google Patents

Description

The invention relates to measuring technique and can be used in testing hydrophones.

According to the main author. St. Ν '783595 a method of absolute graduation in chambers controlled by an elastic-mass impedance is known, which consists in installing a hydrophone in a measuring chamber filled with liquid, creating an alternating overpressure at the inlet of the tested hydrophone by vibrating the measuring chamber and determining sensitivity as the ratio of the voltage from the hydrophone output to the pressure at the inlet, and establish a hydrophone in two different cross sections of the measuring chamber, measure the distance from the hydrophone to the liquid level, After creating an alternating overpressure, the amplitudes of the voltages from the hydrophone output are determined when it is secured in these two sections, the difference in the amplitudes of the measured voltages is found, and the sensitivity is determined taking into account the above parameters.

The disadvantage of this method is the low reliability of grades · ⁵ ki in closed chambers at high hydrostatic pressures.

The purpose of the invention is to increase the accuracy of graduation in closed chambers at high hydrostatic pressures.

This goal is achieved by the fact that after creating an alternating overpressure, the phase shift between ¹⁵ strains from the outlet of the hydrophone is additionally determined, while the sensitivity of the hydrophone is determined by the formula

NC ^and 7-Ji] where * 7 is the phase shift,

- voltage output hydro 932654

LIQUID) angle of gravity;

background set at a depth of H ^, ’

- voltage from the output of the hydrophone installed at a depth of Hq V

P is the density d is the amplitude of the chamber;

qj - acceleration

UJ is the circular frequency of oscillation of the camera.

Example. A hydrophone made on the basis of a spherical piezoelectric element F 52 mm made of TsTS-19 was calibrated. The calibration was carried out in a swinging chamber. The dimensions of the liquid column are C = 840 mm, diameter f 80 mm. The signal frequency is 1.4 Hz. The working fluid is transformer oil., The density of which was 878 kg / m ^. The hydrostatic pressure in the chamber is about 10 MPa.

The hydrophone was fixed in the chamber with the ability to move in depth.

The method is as follows.

The hydrophone is fixed at a depth of H ^ = 0.523 m, the chamber is sealed, a static pressure of 10 mPa is created and the chamber is oscillated in a pendulum motion with a signal frequency of 1.4 voltage output, which equals = after the camera stops HYDROPHON To a Depth of H ^ = repeat position 2 and measure the voltage equal to Uq = 0.053 V. Record voltage oscillograms, including the first periods of vibrations when fixing hydrophones at a depth and Hjp, on an H-327 type recording device. The analysis of the waveforms shows that the amplitudes of the first oscillations have a phase shift of 180 °; therefore, the sensitivity is determined from the relation _

Hz, measuring. hydrophone, 0.024 V, move 0.723 m,

1S

In contrast to the main method, the sum of the measured voltages is found and the phase shift of the stresses is determined.

. VNIIPI Order 3803/77 "------- • Г · - · - -by. - Branch of PPP Patent, g

The sensitivity, measured taking into account the analysis of phase relations, does not go beyond the error limit of the known method. Calculation of sensitivity without taking into account phase relations leads to gross errors (i.e. when they find the voltage difference).

The choice of depths closer to the bottom of the camera has several advantages when calibrating hydrophones with low sensitivity.

The advantage of the proposed method is to obtain large levels of sound pressure at the inlet of the hydrophone. This leads to an increase in the signal-to-noise ratio.

Claims (1)

Claim The absolute calibration of hydrophones in chambers controlled by elastic-mass impedance, according to ed. St. No. 783595, characterized in that, in order to increase the accuracy of calibration in closed chambers of static variable, the shift between the hydrophone is additionally determined, and the sensitivity of the hydrophone is determined by the formula 4 [υ _α -υ at increased hydraulic pressures, after creating excess pressure, the phase voltages are determined with exit where H - phase shift; and _t <r si fluid ·, the angle of oscillation of gravity; voltage from the output of the hydrophone installed at a depth of H ^; voltage from the output of the hydrophone installed at a depth of H ^ ·, the density is the amplitude of the chamber; acceleration of the circular frequency of the camera.