Barometers General Information
From
the Greek word meaning "measurer of weight or pressure."
The
first barometer was invented by Torricelli in 1648 and indicated
changed in atmospheric pressure by virtue of a fluctuation column of
mercury. In 1847, Vidie developed the aneroid barometer which
is still in use today. It is a closed box with a flexible
bottom which registers even the slightest changes in atmospheric
pressure. The top and the bottom of the box are held apart by
a spring. Whenever atmospheric pressure increases, pressure is
exerted on the box, and consequently the spring. The degree of
pressure is transmitted to an indicator needle. Rises and
falls in atmospheric pressure provide a reliable indication of
approaching changes in the weather within the next 24 to 48 hours.
The most used unit of measurement for atmospheric pressure today is
the hekto-Pascal, abbreviate hPa, which can be compared to millibar
(mb). One inch
of mercury is approximately 33.86388 hecto pascals (hPa).
