Study On Key Techniques For Calibration Of The Sound Velocity Profiler

As the light wave and electromagnetic wave can not propagate in long range,the sonar instruments are widely used in the areas of detection,location,navigation,communication,even in inland waterways.The speed of sound in seawater is a function of temperature,salinity,and pressure.A correction of the measuring data by depth meter,side-scan sonar and other sonar instruments is needed according to the real-time speed of sound.Now days,the speed of sound in water can be calculated from an equation of state using real-time observations of temperature,pressure,and salinity.The calibration of sound velocity profiler is relying on the speed of sound by the correlation,and the speed of sound by CTDs is also calculated by the correlation.The speeds of sound have a great distance between different correlations,which cannot satisfy the needs of the accuracy measurements.It is necessary to research a new method for determination of speed of sound and calibration of the sound velocity profiler.The following work is described in this paper:1.The fundamental theory of the ultrasonic wave propagating in the liquid is studied.The vibration and attenuation model of the transducer excited by different signal is established.The influence of the viscous dissipation and heat conduction in Newtonian fluids is analyzed.The calculation method of diffraction correction to the time of flight was established.2.An apparatus for absolutely determination of the speed of sound is consists of circuit board,the double beam interference,the precision electric displacement platform.The circuit board which is based on the tapped delay line method is used to measure the time of flight;the double beam interference is used to measure the pathlength different of the acoustic waves;the precision electric displacement platform is used to control the place of the receiving transducer.This apparatus can be used in ambient pressure,and the uncertainty is calculated.3.A X-cut quartz transducer was designed based on the research of the piezoelectric material properties;the vibration of the quartz transducer obeys Gaussian distribution when excited by a sine signal.The speed of sound sensor is consists of quartz transducer and several stainless steel parts.The different of acoustic path length in varies temperature and pressure and the diffraction correction to the time of flight are studied.The method of time of flight is based on the cross correlation function.The method of calibration for the speed of sound sensor was studied,by which the acoustic path length and the delay time can be calculated.4.A high accuracy calibration apparatus of the sound velocity profiler is realized,the calibration method of the sound velocity profiler in ambient pressure is studied.