B&G H5000 Analogue Expansion - Manual (Page 58)

58 | Sensor calibration | H5000 Operation Manual
True Wind Angle calibration
There are two methods of calibrating TWA, monitoring true wind direction from tack to tack
or use the compass to verify the angles the yacht is tacking or gybing through.
Start the TWA calibration process for either method by setting the boat up to do a number of
tacks upwind or gybes downwind in as steady conditions as possible.
Method 1 - Monitor True Wind Direction changes
If an error is seen in true wind direction, then the following rule applies:
• If true wind direction is being shown as a lift each time you tack then True Wind Angle is
reading too wide, half the error must be subtracted from the TWA correction table.
• If true wind direction is being shown as a header each time you tack then True Wind Angle is
reading too narrow, add half the error to the TWA correction table.
Method 2 - Monitor tacking angles
If according to the compass you are tacking through an angle diff erent than the sum of the
True Wind Angles on each tack (Port TWA + Starboard TWA) then the following rule applies:
• If the tack angle < the sum of the TWA’s, the True Wind Angle is reading too wide, half the
error must be subtracted from the TWA correction table.
• If the tack angle > the sum of the TWA’s, the True Wind Angle is reading too narrow, add half
the error to the TWA correction table.
¼ Note:
Ensure your compass is correctly calibrated before carrying out TWA calibration using
either method.
True Wind Speed calibration
True Wind Speed errors are seen from sailing upwind to downwind. This is due to the
acceleration of the airfl ow over the top of the mast and around the sails when sailing
downwind. -10% is the default value for TWA calibration. Monitoring the change in True Wind
Speed from close hauled to broad reaching will enable further refi nement of this calibration
value.
Auto Calibration via webserver
It is possible to auto calibrate both tables via the Webserver. See the Webserver help fi les for
more details.
Heading (compass)
Auto Cal
The compass Auto Cal process records the magnetic fi elds in the yacht that cause deviation
errors. It calculates the corrections when the compass calibration is started provided the
following conditions are met:
• The 360º turn - RC42 compass or 2 x 360º turn Halcyon Gyro Stabilized compass is completed
in the same direction.
• The rate of change of heading does not exceed 3º/s; i.e. the turn should take about 2 minutes
to complete.
• The rate of change of heading must not fall below 0.2 °/s during the 360° turn, i.e. the turn
must not take longer than 12 minutes.
• The rate of change in heading is reasonably constant.
• The compass is installed in a location a safe distance from magnetic interference such as iron
keels, engines, loudspeakers etc.
• Consideration should also be given to electrical cables which may carry high currents (e.g.
large motors).
• The compass is installed in a location as close to the centre line of the boat as possible. Avoid
areas such as the fore peak and the sides of the hull where the eff ects of pitch and roll are at
their greatest.
• On steel hulled vessels, the compass will need to be installed above decks away from the
eff ects of the hull.