Functional Limitations; Stw; Sog - JRC JLN-900 Installation And Instruction Manual

Travelled distance
2 to 10 NM
10 to 50 NM
Over 50 NM

Functional limitations

2.3

2.3.1 STW

The STW part of the system is in operation when speed and distance is shown on the master
display.
The speed measurement influence is within IEC 61023 specifications for pitching up to +/- 5
degrees and rolling at +/- 10 degrees.
The STW speed sensor is sensitive to the water flow at the transducer position. The ideal
water flow is parallel with the longitudinal/keel line and non-turbulent. Air bubbles or ice will
reduce or completely block the acoustic transmission making measurement impossible.
Reduced STW performance may occur when many acoustic reflectors are present in the water,
such as muddy water in rivers and canals, river inlets, harbour areas and similar shallow water
areas with soft bottom structures. When normal conditions are not met, the STW may indicate
zero speed at low speed or invalid status with digital indicators displaying "---".

2.3.2 SOG

The SOG part of the system is in operation when SOG speed is shown on the master display.
The speed measurement influence is within IEC 61023 specifications for pitching up to +/- 5
degrees and rolling at +/- 10 degrees.
The SOG sensor is using acoustic signals, thus sensitive to blocked acoustic transmission.
Moderate amount of air bubbles or ice will have a minor influence on measurement, but
excessive amount makes measurement impossible. When normal conditions are not met, the
SOG indication will show invalid status and digital indicators indicate "---".
Error
0.2 %
0.1 %
0.05 %
3-4