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.

Bill

----- Original Message ----- 
From: "Peter" <plp@actcom.co.il>
To: "Microcontroller discussion list - Public." <piclist@mit.edu>
Sent: Wednesday, June 01, 2005 6:58 AM
Subject: Re: [EE] Atmospheric Pressure Ranges


>
> On Tue, 31 May 2005, Mike Hord wrote:
>
> > I'm trying to get a feel for the "normal" range of atmospheric
> > pressure.
> >
> > Wikipedia tells me that the highest and lowest ever recorded
> > barometric pressures are 108.57 kPa and 86.996 kPa,
> > respectively.  It also tells me that "standard" atmospheric
> > pressure is 101.325 kPa.  What it does NOT tell me (nor
> > does anywhere else) is what the "normal" range is; that is,
> > if a good, strong thunderstorm passes through, what can
> > I expect the pressure to be?  Likewise, in a typical high
> > pressure area, what can I expect the pressure to be?
>
> It depends at what altitude you are.
>
> > I'm trying to develop a water depth gauge, and if possible,
> > I'd like to get some feel for the variation of pressure based
> > on atmospheric variations.  The highest to lowest cited
> > above would represent a 2.2 meter(!) fluctuation in the
> > depth of a body of water, if one were basing the depth on
> > the pressure at the bottom.  Needless to say, that
> > kind of variation would render the information useless.
>
> Pressure based depth gauges use a differential transducer. One end is
> exposed to the air. This removes the problem you describe and adds the
> problem of having two tube openings to keep clean.
>
> > Normal diurnal cycles are <.5 kPa, which corresponds
> > to approximately 5 cm of water depth.  No info on
> > typical changes outside those variations, however.
> >
> > Differential measurement is NOT an option for this
> > application.
>
> You can measure depth pretty accurately using ultrasound from below. The
> water/air interface bounces it back strongly. But if you have waves it
> will be hard anyway.
>
> Peter
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