Setra System Model 370 - Manual (Page 26)

5.2 DISPLAYING TRUE ALTITUDE
The Model 370 can function as an altimeter displaying true altitude by
correcting the above Standard Atmosphere conversion for the local barometric
pressure. This correction can be setup two ways.
If you are starting at a known station elevation, use the following procedure:
1. Press CONV until the gage is displaying pressure units (make sure not to
select "ft" or "meters").
2. Press SETUP, then press the f(p) key. The display will read "CAL FP".
3. Enter the station elevation and press SETUP. The display will read
"units ft".
4. Press CONV to select the desired units of elevation, either "ft" or "meters".
5. Press SETUP. The gage will accept the station elevation and display
"SEA LEVEL" corrected pressure (as in Section 4.2).
6. Press the ZERO key. The display indicates the difference between the
current pressure and the sea level pressure.
7. Press the CONV key until the desired altitude units (ft or meters) appear in
the display. The display will now indicate the true altitude above sea level.
8. The gage is now functioning as a corrected altimeter, and will indicate true
altitude as it is moved from one location to another.
CAUTION: In any true altimetry application, the accuracy of the measure-
ment is dependent on the quality of the correction made for local barometric
pressure.
Barometric pressure changes often, and so the reading will drift over time as
the sea level corrected pressure drifts. To recalibrate the true altimeter, repeat
the above procedure at a known starting elevation often.
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