Calibration and Accuracy:
The barometric sensor used in the Raven is a digital-output sensor that contains the entire
analog measurement chain on one chip. The sensor is factory-calibrated over a wide
range of temperatures and pressures to provide exceptional accuracy under any rocketry
conditions. The combination of individual chip calibration and end-to-end temperature
compensation provides barometric accuracy that raises the bar for rocketry altimeters.
The Raven has less than 1 mbar (0.1% full-scale) pressure error over most conditions,
and less than 3 mbar pressure error (0.3%) the temperature range from -40C to 85C, and
from 1.1 Atm (2500 feet below sea level) to 0.3 Atm (30,000 feet above sea level).
Keep in mind that however accurately the Raven measures pressure, converting pressure
to altitude results in additional error. The Raven uses the International Standard
Atmosphere (ISA) model, which uses 3 different formulas for different altitude ranges
between sea level and 104,987 feet to compensate for the temperature behavior of
different parts of the atmosphere. The standard atmosphere model is implemented in the
Raven with full ANSI-C floating point calculations to avoid errors from numerical
approximations. The standard atmosphere model, however, is an approximation to
typical conditions for mid-latitude locations. It assumes a temperature profile that is
likely to be colder than typical rocketry conditions. For example, the standard
atmosphere model assumes that the sea-level temperature is 59 F, and that the
temperature at 5400 feet ASL is 40F. Errors caused by the atmosphere being warmer
than the standard atmosphere can result in reported altitudes that are low by 10% or more.
For the most accurate conversion between the pressure and altitude, use the twice-daily
balloon sounding data measured by NOAA and conveniently available at
http://weather.uwyo.edu/upperair/sounding.html
. Future versions of the FIP may include
an option for automated lookup and correction based on this data.
Specifications:
Contact Information:
Email:
Brand
Featherweight
Model
Raven3
Axial Accel range and
frequency
105Gs, 400Hz
Axial Accel resolution
0.045 Gs
Lateral Accel range and
frequency
105 Gs, 200 Hz
Lateral Accel Resolution
0.09 Gs
Download Interface
USB mini
Baro Range (kft)
100
Baro resolution
0.00004 atm
Pyro Outputs
4
Single-battery max output
Amps
22
2-battery max output Amps
22
Other recorded
measurements
Temperature, 4
continuity voltages,
all event logic,
battery V
High-rate recording time
480 seconds
Low-rate recording time
35 minutes
Size
0.8" x 1.8" x 0.5"
Mass
6.6 grams
