Prerequisites
The physical properties of the hull unit installation are known.
The correct type of hull unit is selected.
The vessel is berthed or at sea.
Context
The middle position is not a fixed length. The physical middle position depends on which type of hull unit you are using with the SU90 system.
Retracting the transducer to a middle position may be useful if you use the SU90 system simultaneously with other sonars. A higher position will permit you to increase the vessel speed. If you operate in very shallow waters, you may also reduce the risk of hitting bottom. However, placing the transducer immediately under the hull may increase the flow noise.
CautionIf the transducer hits larger objects or bottom, the transducer shaft may be bent, or - in worst case - it can be broken off.
A broken transducer shaft will cause water leakage through the top of the shaft. If you suspect that the transducer shaft
is seriously damaged with holes, do not retract the transducer to its upper position.
To prevent serious damage to the vessel or the vessel stability, you must have a water pump and a warning system in the sonar
room.
Select the middle position carefully. The position is normally selected to place the transducer just under the keel, but low enough to prevent echoes from the trunk. Once the position is selected, make sure that the system protection functionality does not inhibit transmission.