Developing Measurement System for Sea Waves Height

Abstract

The study of underwater acoustic channels is important for applications such as telemetry between underwater vehicles. There are fundamental limitations associated with underwater communication channels in common with other communications media (i.e, spreading noise, Doppler shift of 1%, signal fading and multipath propagation). These limitations, multipath propagation caused by reflections from the sea surface and sea floor is particularly extreme. An important consideration when dealing with the multipath reflections is the movement of the sea surface, as this can affect the way in which acoustic signals travel. It is therefore necessary to have a good record of the surface conditions during experiments using acoustic communications. There are various methods and transducers that can be used to measure the surface variation. The developed system described in this paper (stepped-contact staff and a MATLAB simulation) is capable of measuring small and high frequency surface waves to a high degree of accuracy. It can operate in water with high impedance (up to 700kΩ per 5) and consists of a simple design. A DC Whetstone Bridge was used to modulate the sea surface movement, a voltage follower operational amplifier was used due to the high impedance of the output of the bridge and a TC500EV A/D converter was used with a micro-controller interfaced to a PC using its RS232 serial port. A MATLAB program simulated and plotted the variation of the depth of the wave staff in centimetres.