Furuno DS-80 Remarks on Usage, Conditions Affecting the Accuracy, Beware of Transducer Location

REMARKS ON USAGE

Remarks on Usage

The DS-80 measures ship’s speed by detecting the Doppler shift frequency of the echo reflected by a watermass (water layer containing plankton and other micro- organisms) located within the measuring area, which is usually about 2 m. In some instances, however, no signal is returned because of too few plankton in the sensing depths. This phenomenon can occur in particular areas in particular seasons. The probable cause is the plankton are lying in deep water because an ice-melted cold water mass covers the sea surface. Similar cases may also occur in a freshwater lake. Under these circumstances the DS-80 will not show the correct ship’s speed.

Conditions Affecting the Accuracy

(with ref to IMO A.824/3.3)

The Doppler speed log DS-80 is designed for reliable and accurate performance through FURUNO’s long experience and advanced technology. It operates on the best choice of system frequency and power output. As far as the sonic energy is used, the performance (accuracy) may be reduced or even lost under:

•rough weather (may be sea state 6 or severer)

•improper location of sensor, e.g., too close to the propeller, thrusters, drain tubes, echo sounder transducer

•depth under the keel if less than 3 m

The accuracy will not be affected by:

•- water temperature (sound velocity)

•salinity

•pitch/roll ±10°

Beware of Transducer Location

The transducer may be damaged if it hits the dry dock blocks. Take the following measures to prevent damage to the transducer.

1.Before delivering the ship, draw up a suitable docking plan taking into account the dimensions and location of the transducer. Store the plans onboard the ship.

2.Place the dry dock blocks according to the plan.

3.Have a diver check the position between the transducer and the blocks before removing the water. Confirm that the transducer will not touch the blocks.

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