Ultrasonic underwater depth measurement

Abstract

It is required a precise, linear indication of the depth of water in a specific part of the sea. This demands a continuous level measurement. There are a wide variety of ways to produce a signal that tracks the depth of water in a specific part of the sea. Ultrasonic detectors find the distance between seabed to the surface of the water. To measure level, depth, with an ultrasonic range detector, the module is mounted at the bottom of the sea, seabed, looking up the surface. We must measure the time between the transmit pulse and the echo received pulses. Since the ultrasonic signal is traveling at the speed of sound, the time between transmission and echo received is a measure of the distance to the surface,water depth. A micro-controller sends a pulse to the ultrasonic module. The module is transmitting an ultrasonic wave for a short period of time and wait for receiving its echo. As soon as echo received to ultrasonic module, is sent a pulse to micro-controller, which measures the time between two pulses. There are two modes of operation, program mode and run mode. When the unit is powered. it is programmed to start up in the run mode, to detect the distance from the transducer face to a target, depth, in meter. The unit can be placed into program mode at any time by pressing the menu key to alter a value of parameters in order to better suit the application or user preferences. Unit of measurement, type of measurement, set point of alarms and factory setting are some of its parameters. The working time of transition and receiver part of the module is specifies by micro-controller normally for each second 10 ultrasonic pulses are transmitted. The measuring error is approximately 1.25%. Such an error value is acceptable with reception to wavelength of ultrasonic waves. For so many application that the precision of Cm is sufficient ultrasonic level measurement is suitable. The system protected from virtual echoed by using threshold and counting number of echo pulses. © 2002 IEEE.