From a manual I found online:
4.2 User calibration
The User calibration procedures:
• Linearise and align the wind transducer.
• Select the required wind speed units
Linearising and aligning the wind transducer
This procedure ensures that the sensors in the windvane transducer are
correctly calibrated to record rotation of the windvane, then
compensates for any small errors which may exist in the alignment of
the wind transducer.
To do this:
1. Power-up the ST60 Wind instrument.
2. Slowly turn the vessel through two complete circles. This
procedure automatically linearises the windvane. A successful
linearisation is indicated by the digital display flashing and the
buzzer sounding three beeps.
3. Hold down the disp and true/app keys for approximately
2 seconds to enter User calibration then use the disp key to select
the wind angle screen (see the User calibration flow diagram).
4. Sail directly into the wind and adjust the analogue pointer to zero,
using the vmg and tack keys. If you are unable to achieve the
required degree of accuracy due to sea conditions, and errors
become apparent during subsequent tack operations, repeat this
procedure to achieve alignment accuracy.
5. Display the wind speed units screen.
6. Use the vmg and tack keys to select the units you want, either
knots (KTS) or metres per second (M/S)