SU485579A1 - Hydrophone Calibration Device - Google Patents

Description

The invention relates to hydroacoustic measurements and can be used for graduating hydrophones by the method of piezocompensation in the range of sound frequencies. . / A device for calibrating hydrophones is known, which includes a measuring chamber with a sound pressure emitter, a J-coupled at the bottom of the cameo, and a piezoelectric compensator by the former. However, in the known device, increasing the frequency decreases the measuring accuracy. This is explained by the fact that the sound field excited in the chamber by a single emitter is a kind of standing wave, the amplitude of which is non-uniform along the axis of the chamber, and this non-uniformity increases with increasing "intensity." In this case, in order to provide the equal for its correct graduation equal to its sound pressure acting on the compensation transducer and on the graduated hydrophone, it is necessary to combine the plane of acoustic symmetry G1 of the microphone and the transducer, which position is not always is known. In addition, as a result of the measurements, additional errors are introduced due to the computers in the upper chamber, making it difficult for the air bubbles to be detected and removed from the cavity of the chamber. The purpose of the invention is to improve the accuracy of the situation. : This is achieved by the fact that the device is equipped with a second radiator, located in the upper part of the chamber, and a phase shifter connected between the inputs from the tutorials, and the measuring chamber is performed; .en as an open top cylinder. ; The drawing shows a block diagram of the proposed device. G The device includes a measuring camera 1, into the internal cavity of which. A graduated hydrophone 2 is inserted, which is mounted on a special bracket 3. The IB upper and lower parts of the internal Jaosti camera have two identical

cylindrical radiators 4 and 5 of piezoelectric ceramics, whose inputs are interconnected through a phase shifter 6. In the middle part of the chamber there is a piezoelectric compensa- tion converter 7 built in. In addition, the device has an electronic measuring unit 8, which consists of a master oscillator (a 9, fv The detector 10, the attenuator 11, the preamplifiers 12 and 13, and the recording oscilloscopes 14 and 15.

The proposed device works as follows.

The emitters 4 and 5 from the electronic measuring unit are supplied with the voltage of the frequency at which it is necessary to perform calibration. Using a phase shifter 6, the relative values of the voltages Ui and 1/2 supplied to the lower and upper radiators, respectively, are adjusted in such a way that the ratio:

1- (hh --- | -),

Ifa

UiCh

fl, is the height of the emitters,

Where

Ufe

- full height of the cavity of the camera - the wave number.

With this, the sound field in the chamber between the radiators takes the form of a flat traveling wave. The calibration method after the establishment of the traveling wave mode does not differ from the usual method used in the graduation of hydrophones by the method of piezoelectric compensation.

The magnitude of the compensation voltage 1l supplied from the master oscillator 9 through the phase shifter 1O to the inner shell of the compensation converter is adjusted so that the signal from the outer shell of the transformer recorded on the oscilloscope 15 becomes zero. In this mode, called the compensation mode, a voltage is applied with voltage Uj with voltage from a graduated Vr hydrophone. Comparison n} is produced by visualization on the oscilloscope screen 14, where the voltages are alternately supplied with a per-switch

preamplifier 12. The hydrophone jf output voltage is memorized, and then using the attenuator 11 on the screen of the oscilloscope 14 sets the same voltage. In this case, the sensitivity of the calibrated hydrophone is read directly from the attenuator scale,

Since the amplitude of the sound pressure in the traveling wave does not depend on the smooth coordinate, regardless of the mutual arrangement of the calibrated hydrophone and the compensating transducer, the average pressure acting on them is one. In this case, there is no need to combine the acoustic symmetry planes of the hydrophone and the compensation transducer, which allows extending the measurement range to the side

higher frequencies and improve the accuracy and performance.

The absence of the top cover of the chamber simplifies and accelerates the operation of replacing hydrophones, the time for which in this case

is determined by the design of the bracket and takes no more than a few minutes, and also allows you to visually monitor the presence of air bubbles in the cavity of the chamber and take timely cameras to remove them, which also leads to a measurement accuracy.

Subject invention

A device for grounding hydrophones includes a measuring chamber with a sound pressure emitter installed in the lower part of the chamber and a piezoelectric compensating transducer, characterized in that, in order to improve the measurement accuracy, it is equipped with a second emitter located in the upper part of the chamber and a phase shifter connected between emitters, and the measuring chamber is made in the form of a cylinder open at the top.