In order to obtain accurate barometric pressure measurements, a barometer needs to be both stable and calibrated against a known reference atmospheric pressure source, i.e. one that is professionally maintained. Without calibration, air pressure measurements from home weather stations have little value other than in identifying pressure trends.
Most weather stations house their barometric pressure sensor within the weather station display console. Therefore, placement of the weather station console receiver is an important consideration since the physical environment of the console will influence air pressure measurement readings. If possible, install the console at an indoor location where the temperature is as constant as practical, i.e. not affected by home heating, drafts, or the sun.
Station elevation, or the height of your location above sea level, is also a factor influencing barometric pressure measurements. Since all barometric pressure measurements are referenced to sea level pressure, the effect of the higher elevation needs to be removed so that readings are comparable, whether they're taken on top of a mountain or at the seashore. The National Weather Service (NWS) defines this standard as: "A pressure value obtained by the theoretical reduction of barometric pressure to sea level. Where the Earth's surface is above sea level, it is assumed that the atmosphere extends to sea level below the station and that the properties of that hypothetical atmosphere are related to conditions observed at the station."
As mentioned above, the barometer needs to be calibrated against a professionally maintained, known reference pressure source. This can generally be done with ease on most home weather stations, ensuring consistent performance. The NWS tests their pressure gauges annually using calibrated instruments from the National Pressure Standards Laboratory. Taking the altitude of your instrument into account, calibrating your barometer using the air pressure measurement of the nearest NWS automated weather station is highly recommended. To find the nearest ASOS station to you, visit NOAA's National Weather Service and enter your zip code.
Please be aware that most manufacturers provide an altitude rating for the barometer in their weather stations. Many are limited to operating at 6,000 feet or below and using the station above the maximum rated altitude will likely result in erroneous barometer pressure readings. If your weather station is going to be installed above 6,000 feet elevation be sure to check the altitude rating before making your purchase.
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