Setra System Model 370 - Manual (Page 23)

4.2 DIGITAL ALTIMETER SETTING INDICATOR
The Model 370 may be used to display corrected sea-level pressure by
"reducing" true barometric pressure at a known elevation to what the pressure
would be at sea-level at the same latitude and longitude.
This function is only available on gauges with barometric or absolute pressure
sensors.
Before using the "SEA LEVEL" correction mode, you must first determine and
enter the station elevation, which is the altitude above sea level at which the
gauge is installed.
1. Press CONV until the gauge is displaying pressure units (make sure it is not
displaying in "ft" or "meters").
2. Press "-", then Clear to make sure the tare/zero registers are empty.
3. Press SETUP, then press f(p). The display will read "CAL FP".
4. Enter the station elevation and press SETUP. The display will read
"units ft".
5. Press CONV to select the units of elevation, either "ft" or "meters".
6. Press SETUP. The gauge will accept the station elevation and display
"SEA LEVEL" corrected pressure.
Once you have entered that station elevation, you can switch quickly and easily
from true barometric pressure to corrected sea level pressure and back by
pressing f(p).
The terms "Station Elevation" and "Reduction of Pressure" have very specific
meanings in the jargon of Altimeter Setting Indicators and the actual
calculations performed by the Model 370 are fairly complex. For further details,
consult: "Smithsonian Meteorological Tables, Vol. 114", NACA Report #1235,
or contact a Setra Applications Engineer.
NOTE: When the f(p) key is pressed in order to begin displaying pressure
corrected to sea level, the zero/tare value described in Section 3.7 is cleared
automatically to assure that absolute sea level pressure is displayed.
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