Altitude number (in eet)
In ^ xxx v
(Where Altitude is the sensed altitude in eet, and xxx is the current calibration value.)
Writ down th calibration valu so it can b r -s t if n d d!
The In is above the Units button. Press this button when ready to input the selected
correction value, as described in the next step.
6. Go to a pressure that corresponds to the selected calibration point (re erenced rom
29.92 inHg/ 0 eet), as read rom a pressure standard. When the altitude is stable or
approximately 15 seconds, note the altitude displayed on the ALT-621 display in
calibration mode.
I the displayed altitude is lower than the standard, press the Exit button as needed to
incrementally raise the altitude to be equivalent to the standard.
I the displayed altitude is higher than the standard, press the Leak Check button as
needed to incrementally lower the altitude to be equivalent to the standard.
As the altitude is adjusted, note that the displayed correction actor also changes, and the
change is in increments smaller than the altitude. Use this to ine-tune the altitude as
close as you can to the standard.
When the ALT-621 altitude matches the standard as close as possible, wait another 15
seconds to ensure that the internal mathematical iltering corrections have been done. I
satis ied with the results, press the Units button to save the selected correction, and the
display will automatically proceed to the next calibration level.
7. Repeat the procedure in step 6 at each requested altitude: 10000, 20000, 30000, 40000,
45000, and 50000 eet as needed
8. A ter entering the calibration value o the highest altitude, pressing the Units button
will change the calibration to the VSI calibration mode. Select a vertical descent speed
(5,000 eet is suggested) on the calibration test equipment and activate it. The ALT-621
will indicate the calculated VSI value. Adjust i needed by pressing the Exit or Leak
Check buttons. When inished, press the Units button. The VSI calibration value will be
saved.
9. A ter the VSI calibration has been entered, the display will brie ly read “Finish d Cal”
and then re-start. There is no need to re-cycle power.
H lpful Not s: By pressing the Light button the calibration can be cycled through the
various calibration points o 0, 10,000, 20,000 eet, etc. This is handy or use in those
cases when only one range is in need o calibration. Note, however, that the unit must be
within less than 5,000 eet o the selected range in order to save the new value. This
eliminates accidentally saving a value when in the incorrect pressure range.
