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Re: absolute pressure



interleaved below:

Herbert H Gottlieb wrote:

On Wed, 05 Jun 2002 11:04:26 -0700 Bernard Cleyet <anngeorg@PACBELL.NET>
writes:
Why do they call it a "mercury" barometer?
as aposed to the original Torricelli barometer? (water)
http://www.islandnet.com/~see/weather/history/barometerhistory1.htm

Until the advent of S.S. electronics, neroid barometers were
significantly more efficient (cost per performance) than the
mechanical ones (aneroid).

A lab. mercury barometer (still ~ $100?) has a vernier scale resulting
in a precision of 1/10 mm. I claimed that an aneroid of this precision
would be considerably more than $100. Now with chip amps. and Hall
devices, wrist watch altimeters are less expensive. The geologists'
altimeter I saw was very large with a dial of ~ ten inches in diameter.

*** Please explain what you mean by the above sentence.

Geologists use(d) aneroids for mapping. Their
resolution is ~ one foot. (memory) The pilot on this list can
compare this to his. [What does he use now?]

*** Pilots are more likely to use either altimeters, which are
specially calibrated aneroid barometers, or radar devices.

Here's my question: more (likely to use ...) than what?

bc


Herb Gottlieb from New York City
(Where we have found ingenious ways to measure the heights of our
buildings with mercury barometers)