Re: measuring depth

[shawl@torchlake.com (Jonathan Shawl)]

Jolyonp@aol.com wrote:

> Hello everybody,
> I certainly have enjoyed all the great e-mail on this site.  However, I have a
> question that I hope some of you can help with.  I've been building unmanned
> submersibles for a few years...each one is a bit better than the last.  I
> operate them from a boat on the surface...I hope to make one good enough to
> investigate sunken ships at some point.  My question is this:  I need a device
> that measures the depth that my sub is operating at and then transmits the
> information to a display on the surface.  This isn't a remote controled
> boat...it is "hard wired".
> Any ideas?
> Thanks very much,
> Jolyon Pegis

Hi, Jolyon
I can think of 2 ways to do that easly.
1- Put a electronic pressure transducer on the ROV and use wire to send the signal
to the surface.
This can get expensive depending on how acurate you need it, and how long a wire
you are running.
or
2- Run a small cheep clear plastic or rubber tube down along with your power
wires, attach one end to the Rov. The other end you connect to a air or nitrogen
gas source that has a flow regulator, (you will need a pressure regulator ahead of
flow regulator if using HP gasses) Set it so that the air is flowing a very small
amount out the tube throughout the dive, just enough to keep the tube full of
water when diving down. Then with a accurate dial type or electronic pressure
guage, T it into the line,  you get a pressure reading equal to the water pressure
at the ROV.  Then calabrate the guage system for feet of water, or just calculate
the depth from PSI. You can get pressure guages that are calabrated to feet of
water. Remember to recalabrate if you switch from fresh to salt water or back.
Jon Shawl