If the magnitude of the magnetic field measured by Ruby's magnetometer is substantially different from the earth's field calculated by Ruby for your location, Ruby will wag the aileron 5 times at the end of preflight, and will display "Warning Magnetometer" on the OSD.
The solution is to remove or move away from whatever is creating the distortion in the magnetic field, or to re-calibrate the magnetometer.
Ruby uses a 3 dimensional magnetometer to measure the earth's magnetic field vector. This is required not just for navigation, but for attitude artificial horizon. It is located on the airspeed / magnetometer sensor.
If the field measuremente is not accurate, performance may be degraded. Ruby may still perform fairly well, but with more severe inaccuracy, erratic or oscillating heading and roll, and inaccurate loiter and landing may occur.
Causes:
Ferrous or magnetic objects on the airframe:
examples:
- steel screw within 1/2 inch
- control rod within 1 inch
- servo within 2 inches
- magnetic canopy latch within *12 inches*
Ferrous objects in vicinity:
- inside or near "rebar" reinforced concrete structure such as basement or hi-rise building
- metal desk
- metal tools
- steel watchband
- car within 20 feet
- on top of metal such as trash can
Poor calibration:
If you're sure there's nothing that could be distorting the field around Ruby, then the magnetometer needs to be recalibrated. You'll need to take a few minutes to collect and send me data. Please see:
http://uthere.com/products/ruby/documentation/tuning/magnetometer_recalibration.html
You'll probably never have to do this more than this one time for the life of your Ruby.
Note that the calibration information for the magnetometer and the accelerometer is contained in the ".utcfg" file that was provided for your Ruby. If you switch to a different Ruby Controller or a different airspeed / magnetometer unit, you'll need a different ".utcfg" file. |
