Hello,
I would like to measure surface wave heights from a device floating 0.6 to 1 metre below the surface of the water accurately. The maximum wave height would be 1 meter (trough to crest). The device cannot be one the surface where it would not doubt get destroyed. Ideally, it would be plug-and-play module that has it’s own electronics already and will stream data 20 times per second or more when prompted to do so. The device will be an autonomous arduino based data logger, so power consumption is a major concern.
Measuring this distance could be done by several methods:
]Pressure[list]
]Because the device is below the surface, underwater pressure will vary as the wave passes./:m]
]However pressure will reduce with the square of the depth and careful calibration and correction tables will be required (possible to test and develop)/:m]
]The pressure device must be absolute as not to be affected by internal pressure changes inside the device./:m]
]Can the tube be simply connected to the outside (water inside the sensor) or must it be protected (mineral oil or other)/:m]/:m]
]Sonar
]Unlike other “soft” underwater objects, the surface should reflect well, giving a good hard ping./:m]
]I see waterproof transducers, but they are way too expensive for this project and probably will consume too much power/:m]
]Can low cost ultrasonic proximity sensors be used? They could be immersed in a compartiment of non-conductive mineral oil behind a thin mylar film. Of course, distances will need to be calibrated for the speed of sound in water which is 4-5 times faster./:m]
]I saw project using piezo buzzers and electret microphones, which appear to have issues of their own./:m]/:m]
]Accelerometers
]Measure the circular motion the device makes as the wave passes/:m]
]This is a clean approach, can be sealed up tight./:m]/:m]
]Other
]I doubt IR would see the water surface/:m]
]Laser? Other?/:m]/:m][/list:u]
I would appreciate advice as to the right choice of technology as to purchase the right modules to test with.
Many thanks,
Paul.