SU805073A1 - Low-frequence hydrophone calibrator - Google Patents

Description

The invention relates to a measurement technique and can be used to determine the sensitivity of low frequency hydrophones. A device for gradient and low-frequency hydrophones is known, comprising a drive, a water-air chamber with a pinch and a piston system connected with it, including a piston body and a rod interacting with the piston 13. A disadvantage of this device is the low graduation accuracy due to a design flaw. The purpose of the invention is to improve the accuracy of calibration. This goal is achieved by the fact that the device is equipped with a coupling, two cylindrical coil springs mounted on the rod, a flexible connecting tube, one end of which is fixed on the neck of the water-air lid, the other on the piston body, which is made in the form of a tube and fixed with the possibility of axial movement in the drive housing through an elastic sleeve and a support bracket, the piston is made in the form of a hollow cylinder with a deaf bottom, one end of which interacts with a coupling connecting black without threaded connection with rod. FIG. 1 shows the device, a section of FIG. 2 - oscillograms with the recording of the graduation of the hydrophone, where: a) the calibration curve of the hydrophone at a frequency of 0.05 Hz; b) a function characterizing the operation of the piston system at a frequency of 0.05 Hz; c) the generator output signal with a frequency of 0.05 Hz; g) the output signal of the generator with a frequency of 20 Hz; e) calibration curve of the hydrophone at a frequency of 20 Hz; The device for graduating low-frequency hydrophones contains an actuator 1, a water-air chamber 2 with a cover 3 and a piston system connected with it, comprising a housing 4, a piston 5 and a rod 6 interacting with a piston 5, a coupling 7, two cylindrical helical springs 8 and 9, mounted on the rod b, a flexible connecting pipe 10, one end of which is fixed on the neck of the cover 3 of the water-air chamber 2, the other on the piston body 4 of the system which is made in the form of a tube and fixed with the possibility of axial movement on the body of the drive 1 through the elastic sleeve 11 and the support bracket 12. The piston 5 is made in the form of a hollow cylinder with a blind bottom, one end of which interacts with the coupling 7 connected through the threaded connection with the rod 6.

The device also contains a cable 13, a shock absorber 14 and a clamp 15, by means of which the hydrophone 16, the gland 17 is suspended, the recording system includes a preamplifier 18, a recorder 19, a switch, 20, a generator 21, a flywheel 22, which serves to enter the piston 5 inside housing 4, a tachometer 23 for controlling the speed of rotation of the gearbox, a screw 24 limiting the oscillation amplitude, and an eccentric mechanism 25.

The device works as follows.

Graduated hydrophone 16 is lowered into the open water-air chamber 1, which is three-quarters flooded with water, so that it does not touch the bottom. Then, using a cable .13 and a shock absorber 14, it is suspended from the bracket 15. Hydrophone 16 output via gland 17 is connected to the input of the preamplifier 18, the output of which is connected to the recorder 19.

Switch 20 disconnects the generator 21 from the hydrophone circuit 16 and measures the pressure in the water-air chamber 2. For this, the piston 22 introduces the piston 5 into the housing 4 and only then seals the cover of the water-air chamber 2. Thus, a discharged mode is created. the gap in the water-air chamber, and the piston 5 works to change this discharge.

By setting the desired frequency using a fixed and smooth adjustment of the speed of the gearbox (not marked) and controlling it with a tachometer 23, and the required amplitude of oscillations by a screw 24 associated with a scale indicator (not indicated in the drawing), produced in units of pressure, t change pressure and regulate it. At a known pressure set on a scale of eccentric mechanism 25, double amplitude is recorded on recorder recorder 19 and drive 1 is turned off. After that, using an equivalent replacement circuit, a generator 21 is sequentially connected to the hydrophone circuit 16 and preamplifier 18. Setting the same frequency as and when measuring the pressure in the chamber, the voltage of the signal from the generator 21 is changed until the double ar / 1 at the recorder 19 reaches a value equal to that obtained by measuring the pressure in the water-air chamber 2. and the equality of the amplitudes of the voltage generator 21 corresponds to the voltage zheniyugidrofona 16, acting at the moment of measuring pressure.

To determine the sensitivity of the hydrophone at the selected frequency, the voltage obtained on the generator is divided by the pressure set on the scale of the eccentric mechanism 25, calibrated in units of pressure according to the formula

. R.

where DR is the pressure in the water-air

chamber 2;

g is the radius of the piston; E - linear displacement of the piston (from the maximum of the positive half period to the maximum of the negative half period

V is the air volume of the pipe 10 and the water-air chamber 2. Springs 8 and 9 eliminate the influence of backlash. The equipment is powered from the unit.

In the same way, the all-frequency response is recorded in a given frequency range.

The main advantage of the method is an increase in the accuracy of the calibration of hydrophones.

Claims (1)

1. Bober R. Hydroacoustic measurements. M., Mir, 1974, p. 6566 (prototype). - smith n-ltlnnru 1f-ivH. -V g Ictk