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Pressure Measurement: Difference between revisions
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==Locating the Barometer== | ==Locating the Barometer== | ||
For most personal weather stations, the barometer is in the console, usually attached to the printed circuit board. These barometers are very cheap devices that simply record the load on a diaphragm. Unlike the barometer in | For most personal weather stations, the barometer is in the console, usually attached to the printed circuit board. These barometers are very cheap devices that simply record the load on a diaphragm. | ||
Unlike the barometer in a professional automatic weather station, they have no temperature compensation. Therefore, for best pressure readings, you should locate the console in a place where the temperature is reasonably constant, not in direct sunlight or near a heater. | |||
==Units== | ==Units== | ||
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** In those sites following USA guidance, the SLP pressure is reported in the Remarks Group of the METAR. There are METAR readers available that extract the SLP wherever it is within a METAR, but Saratoga does not. | ** In those sites following USA guidance, the SLP pressure is reported in the Remarks Group of the METAR. There are METAR readers available that extract the SLP wherever it is within a METAR, but Saratoga does not. | ||
* A further complication is that QFE is defined in two ways: | * A further complication is that QFE is defined in two ways: | ||
*# In USA, | *# In USA, ''Field elevation in pilot terms'' is at a height equal to 10 feet above the mid point of main runway (a typical cockpit height) when reporting QFE. That reports 0.3 mBars above international standard. | ||
*# The international standard, used elsewhere in world, uses the airport ( | *# The international standard, used elsewhere in world, uses the true ''airport field elevation'' (i.e. runway height with no correction for height of cockpit) when reporting QFE. | ||
* Finally, it should be noted that all METAR pressures in Pressure Group are rounded down to nearest mBar, so may read up to 0.9 mBar out from a reading expressed to nearest tenth of millibar. | * Finally, it should be noted that all METAR pressures in Pressure Group are rounded down to nearest mBar, so may read up to 0.9 mBar out from a reading expressed to nearest tenth of millibar. | ||