On Wed, 1 Jun 2005, Bill & Pookie wrote:

> The gentleman who was going to look at his altimeter in his plane may have
> the best information.  I assume that the instrument would be adjustable to
> any pressure at any airport prior to starting a flight.  So the range of
> adjustment would cover all "flying" weather.

Yes but since the op wants something that can be left in place for a 
while the airplane gentleman should also obtain the fastest recorded 
barometer *change* observed over time. 50 mbar in 1 hour I have seen 
myself (corresponds to about 0.5 meters of water column).

I still think ultrasound is valid and easily done for 2 meters of depth. 
A collision detector circuit made for car parking could be adapted, 
complete with sensor.

Peter
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