Simrad IS20 Manual page 65

Rudder
The rudder calibration is used to compensate for any
non-linearity in the transmission between the rudder and
the rudder feedback unit.
Adjusting the maximum rudder angle
1. Select Max starboard and press the Menu/Enter
key to start the calibration
2. Manually turn the rudder to h.o. starboard position
3. Confirm that the actual rudder angle is identical to
the readout. Adjust the reading if necessary
4. Repeat the procedure for port rudder angle
Configuration | 65