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What is a Barometer?

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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