Flight 2002A - Upgraded Altimeter
By Tom Dawson, WB3AKD, Chairman, Balloon Committee
Saturday, July 06, 2002 8:36 PM
2002A electronics package was placed in the Tenney Junior Temperature chamber and DC power, and "vacuum" was applied through the Access port in the chamber. The vacuum hose was connected directly to the port on the sensor.
A special Calibration program was loaded into the processor so it would transmit only the Baro counts.
Vacuum was measured by means of a vacuum thermocouple gauge for altitudes above 80K and a large face Bourdon Tube gauge was employed for lower altitudes.
Once the electronics stabilized at a given temperature, the vacuum was adjusted to the proper levels to simulate the appropriate altitude and the counts sent by the package were recorded.
The two curves are the upper and lower limit (3 sigma) over temperature (-30 to +20 C)
The plotted data is the average of all the measurements for a given altitude, plus and minus 3 times the standard deviation. In most cases, the 3 sigma level is less than 1 percent. There does not appear to be a systematice variation with temperature now that the supply voltage to the sensor has been increased to 8 Volts.