Underwater speed?

[Demon]

What about 2 pressure sensors front and back? The difference tells you velocity.

Robert

[Acetronics2]

Nice thing ...

@ 2000 Euros per piece ( 2500 US $ ) ...

Alain

[AvionicsMaster1]

Wow! Seems like such a simple question but I think it might require a complicated answer.

This site http://www.engineeringtoolbox.com/dy...re-d_1037.html can get you close but you've got to know density. This wiki site http://en.wikipedia.org/wiki/Density has a chart that shows water density at temperature.

So if you subsitute the fluid density p(rho) with the equation m/V your equation would be pd = 1/2 (m/V) v2. Solving for velocity would be, well I can't figure out how to write that here but you get the idea. What all this is trying to say is you'll have to get temperature somewhere.

I agree with all in that I'd like to see how you solve this problem.

[Demon]

(Talking out my wazoo on this)

But would density have a huge impact?

Is the sub going to be used in extreme temps, or only between ~15C - 20C?

Personally, I'd use it in temps and depths that I could dive to get it back (got no diving suit). But if you want to set a record crossing the English Channel, that's different.

Robert

[tasmod]

Hmm, your driving it with a propeller. Why not a small free rotating prop on conning tower and measure rotations.

There's example code on here somewhere for wind speed anenometer, which is basically same.

Rob

[Demon]

Won't work when surfaced.

Robert

[tasmod]

Conning tower location was just a suggestion, it could just as easily be on hull etc.

KISS. Small prop with photo reflector for pulse count. Mounted in small tube.

Easier to get going, then maybe try sophisticated solutions.

Rob