54 ST4000 PlusWheel & Tiller AutopilotsOwner’sHandbookNote: A label is supplied to warn people that the compass is mountedbehind or below the bulkhead. This label should be attached where itcan be clearly seen.Correct positioning of the fluxgate is crucial if ultimate autopilotperformance is to be achieved.The fluxgate should, to minimise gimbal disturbance, be positioned asnear as possible to the pitch and roll centre of your boat.ï It is important to ensure that the fluxgate compass is sited at least0.8†m (2.5†ft) away from the steering compass to avoid deviation ofboth compasses.ï The fluxgate must also be positioned as far away as possible fromlarge iron masses, such as the engine and other magnetic devices,which may cause deviation and reduce the sensitivity of the sensor.ï If any doubt exists over magnetic suitability of the chosen site, theposition may be surveyed using a simple hand bearing compass. Thehand bearing compass should be fixed in the chosen position and thevessel swung through 360∞.ï Relative differences between the hand bearing compass and thesteering compass should ideally not exceed 20∞ on any heading.Mounting location for steel-hulled vesselsIf you have a steel-hulled vessel and mount the compass in theconventional location, you will obtain significant deviation due to theeffects of steel on the Earthís magnetic field.To minimise this effect, you should raise the compass transducer abovethe main deck or wheelhouse. However, the higher above the waterline
