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What are Aneroid/Analog & Digital Barometers?
A barometer (baro- meaning weight or pressure) is used to measure
air pressure in weather. For tires, it's usually a tire gauge.
Barometers can be either
analog or digital. The traditional analog barometer is known as an
"aneroid barometer," the round chrome or brass type that you would
normally see on the bridge of a ship, many times accompanied by clock
and temperature/humidity gauge. For an accurate and reliable aneroid
barometer, you should expect to pay $249.00 or more. For aneroid
barometers, accuracy and reliability will wane incrementally below that
price. Scientific instruments including barometers are directly tied in
accuracy/reliability AND cost. In some cases, however, as you go up in
price, accuracy will remain stable but quality of materials and
craftsmanship will drive the pric!
e upwards (i.e. use of thick solid brass or chrome).
Digital
barometers emulate the results achieved from an aneroid barometer
(sometimes called a "nautical barometer). Their accuracy varies wildly
and is not necessarily tied to price! For example, the barometers in
even the cheapest under $100.00 La Crosse Weather Stations are exemplary
performers. Anecdotal observations by us over many, many years shows
that the La Crosse variance from NIST traceable, accurate weather
stations has been extremely minimal at ±.01. Other inexpensive
manufacturer's products have nowhere near this steady and predictable
tolerance. And many are as much as .06-.10 or 2-3mb off after initial
calibration.
All barometers are NOT the same. Most have
elevation limitations. With the Weems & Plath barometers, specific
elevations are designated by each individual product. So, be sure to
probe for this information before you buy. Some barometers can be
upgraded for high ele!
vation use. But this is relatively expensive, generally for th!
ose baro
meters to be used in over 5,000ft terrain.
Digital barometers
can have the same limitations. Again, be careful when you purchase. We
are not aware of ANY low cost digital that will function correctly over
5,000-6,000 ft elevation. For high altitudes, you must consider the
Davis, RainWise, WeatherHawk or Columbia Weather Systems, if you're a
stickler for accuracy. Do not rely on any barometer above 5,000-6,000 ft
for mission critical or safety applications unless you are absolutely
certain of its well defined and guaranteed specifications. And remember
that as you begin to challenge the stated limitations of any scientific
device, your inaccuracies will almost certainly increase as you approach
the stated threshold. For example, a stated 6,000 ft elevation limit
may function perfectly well up to 4,000 ft. Then, possibly a gradual
fall-off in accuracy between 4,000-5,000ft. But then a rapid and
possibly logarithmic increase in error % over 5,000ft. This is just an example and not meant to be a basis for calculating decreasing
accuracy in any scientific instrument.
The original analog
barometer was the water ball. This instrument features a glass reservoir
at its bottom that feeds into a narrowing tube that protrude upwards.
As atmospheric pressure increases, the water is driven upwards into the
tube, indicating a fair or improving weather prediction. Conversely, as
the air pressure lowers, the water in the tube falls, indicating a
weather change and as the water gets lower in the tube, it is an
increasing forecaster of foul weather to come.
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