GP940E 01/97
27.02.97
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12. Calibration chart for altimeter of GP940:
According to FAI rules an altimeter calibration chart of the recorder must be used for altitude evalua-
tion of recorded flights.
If altitude differences are relevant to a claimed flight, the calibration chart must not be older than one
year or a calibration must be done within one month after the flight. Altitude differences are important
for all flights, where the difference between release altitude and landing altitude is not much less than
1000m and for altitude gain flights. These flights are normally all aero tow flights and the 3000m /
5000 m gain flights.
If absolute altitude is concerned, the calibration chart must be not older than one year and a calibrati-
on must be done within one month after the flight. This is important only for absolute altitude world
records.
The calibration chart can be done by the manufacturer of the recorder or by any institution certified by
the national aero club.
To get an altitude trace of the GP940, the recorder must be put into a vacuum chamber and be su-
plied with 12V / 170mA (minus = pin 2, plus = pin 5 of 9 pin plug at the rear of the box besides the
antenna connector - see 11. Pin assignments of connectors). The GPS antenna is not connected.
When power is applied the GP940 starts recording. Now the ambient pressure is changed in steps
from 0m to 11000m. As the recording rate of the GP940 is one sample every four seconds, the am-
bient pressure should stay enough stable at each step to get a good reading.
If it can be managed to operate the marker switch from the outside, the altitudes can be marked with
one second acuracy. These marks can easily be found later in the data file for evaluation.
After all altitude steps were recorded, a PC can be connected to the 9 pin socket at the front besides
the red light. If the internal rechargeable battery of the GP940 is charged, the power supply can be
disconnected or not. If the internal battery is empty, the power supply must be on during data transfer
to the PC. For data transfer use program ZANxxE.EXE or DATA-ZAN.EXE .
Flight data can be evaluated using WINDOWS program WinFDR or the flight data file *.ZAN is
converted to IGC file *.IGC . The IGC file is an ASCII file where altitude readings can be found easily.
If the marker switch is used, the altitude belonging to the mark is always the last reading before the
mark. Each B line represents a reading:
B hhmmss ggmm.ddd N gggmm.ddd E V hhhhh ggggg iii nnn rr
(hhmmss = time, hhhhh = altitude reading)
