On Tue, 7 Apr 1998, Bob Fehrenbach wrote:

> >1) I need to measure water level (and thus contents) in a concrete tank.
> >The tank is about 2m deep, so a float is probably not practical.
>
>     Far out idea #1.
>     If the chemical content of the water is constant, you may
>     consider the possibility of measuring the conductivity
>     between two vertical metal rods.
>
>     Far out idea #2.
>     Measure the capacitance between two *insulated*, closely
>     spaced vertical plates.

      Far out idea #3.
      Strain guage to measure flex of the bottom of the tank,
      and use it to derive weight and therefore volume.
      (I guess it is non-linear, but you could use a calibration
      table.)