2021-06-24
Page 19 of 38
CU-M001 User manual
Things that may effect performance
:
The system sends acoustic beams into the water. These need reflections from the bottom for SOG
and from particals in the water for STW. If the bottom is out of range then the bottom track will fail. If
there are very few particals in the water, the signal may also be weakened.
If the vessel bow is breaching the surface, so that there is air in front of the sensor, then the system
may temporarily loose the signal. Increasing the averaging will stabilise this data.
Interpretation of the IEC61023 standard can vary, and generally it is expected that the STW
parameter should be measured within 3m of the vessel. In some cases the vessel may drag water
with it, and this is compensated by calibration. This unit meausres within the first 3 m, but if required
the sampling volume can be moved out from the vessel in the DL2 setup pages to give better results.
At low depths the system will adjust its sampling volume down to be within the water volume. This
may increase the STW noise.
Depth
Depth is calculated from the bottom track (SOG) signal. Depth from each individual beam can be
plotted on a depth plot and the average of both can also be displayed. These depths are default from
the sensor, and the draught setting must be used to make them display from the surface or from the
hull bottom. There is no calibration for this sensor, however it is important the tilt and temperature are
correct to allow the best possible correction for beam bending and soundspeed in water.
