I can't imagnine why nobody has suggested this yet--come to think of it,
I can't imagine why it took me so long to think of it either :-)

A differential pressure transducer with one inlet at the bottom of the
ballast tank and the other at the top would be perfect.  You can get 1PSI
transducers, which is about 15 cm of water.  Maybe you need a 2PSI
transducer, but I doubt it.

I looked at your pix--looks nice!  Quite a lot of work, I bet.   But it's
a lot smaller than I imagined when you said 30 cm of ballast tank depth!
It looks like its only about 13 cm in diameter. How do you get 20 cm (was
30) of water in the tank?

Don

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