KD7LMO - Payload Computer


Payloads Payload Comp Overview Block Diagram Processor GPS TNC Local I/O Repeater Diplexer Commands Source Code Mechanical Telemetry Data Logger Micro Beacon Cut Down HF-APRS Video Link Pico Beacon NSRV Beacon APRS Beacon

Data Logger

The Payload Computer contains an on board FDR (Flight Data Recorder). The FDR saves information to a 384K byte block of battery backed memory. Information is saved once a second. Once recovered on the ground, the data is extracted from the FDR, processed, and saved in a comma separated text (ASCII) file. This file is suitable to read directly with common spread sheet, mapping, and scientific applications.

The following table contains the header name and description of each telemetry measurand.

Measurand	Description
UTC - hours	Time of log entry in UTC hours
minutes	Time of log entry in UTC minutes
seconds	Time of log entry in UTC seconds
latitude	Latitude in decimal degrees where + is north and - is south
longitude	Longitude in decimal degrees where + is east and - is west
altitude	Altitude in centimeters
altitude (ft)	Altitude in feet (calculated from reported altitude in cm)
1 = 3D lock	1 if the 3D GPS fix, otherwise 0 for 2D or no fix
vdop/hdop	GPS Dilution of Position
visible sats	Number of visible satellites that could be used in GPS fix solution.
tracked sats	Number of tracked satellites used in the GPS fix solution.
baro sensor	Barometric pressure sensor in raw ADC units¹ using SenSym ASCX15AN by Honeywell.
pitot sensor	Pitot tube sensor in raw ADC units¹.
internal temp 1	Internal temperature in degrees Fahrenheit.
internal temp 2	Radio base plate temperature in degrees Fahrenheit.
external temp	External temperature in degrees Fahrenheit.
bus voltage	Battery voltage in DC volts.
dist from lift off (nm)	Distance from start of flight in nautical miles.
heading (true)	Heading from start of flight in true (non-magnetic) degrees.
dist from last fix	Distance from last fix in nautical miles

Telemetry Measurands

Notes

¹ Raw ADC Units - A 24-bit ADC is used to measure common analog voltage devices. Although the ADC provides a 24-bit result, only 16-bits are logged to memory. To convert the raw ADC value to a voltage using the following formula:

Voltage = 5.0 * (ADC Value / 65536)

Using the device's manual or data sheet, a formula is typically provided to convert units of voltage to a device, engineering unit.

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