... And on a similar topic, if anyone has devised a tide height and wave
height sensor which can be protected from spray without affecting
performance, and is not subject to marine fouling, I'd like to hear
about it.
Hello Dereck,
decades ago I saw a device that was made by Adelaide
University that measured wave or swell heights.
I am a bit hazy as to the exact workings of the device.
Visualise a small piece of pipe several inches in diameter
and several inches long with flanges at both ends with
lots of holes around the flange ring. The sort of pipe
fitting you would see laying around at an oil refinery
or in a boiler makers shop.
Inside the pipe is an audio oscillator.
One end of the pipe was made of some sort of hard
rubber or hard plastic type material. I can't remember.
This hard rubber material worked like your ear drum.
As the pressure on it increased it moved in microscopically.
Attached on the inside was some sort of gearing and levers
that you find in bourdon tube pressure gauges. I am hazy,
I can't remember how the movement of the drum changed
the frequency of the oscillator, a pot or capacitor, I can't
remember. Anyway this pipe assembly was sealed up
with a heavy brass end plate with wires coming out of
a heavy duty gland. It was placed in a pressure chamber
and the frequency of the oscillator was recorded for various
increments of pressure. A calibration chart was drawn up
frequency versus pressure. The boffins new already that
a certain head of water represents a certain pressure.
So with this transducer laying on the seabead near the
beach or jetty with a frequency meter attached via long
cables, the wave peaks and troughs could be read as
frequency readout.
The calibration chart can then be looked up to give height
of peak and height of trough above the sea bed.
Sorry for being so long winded.
Regards.
John Crighton
Hornsby
