124 User’s Manual Innomar SES Parametric Sub-bottom Profilers
124 Innomar Technologie GmbH (2020-09)
7.8 Signal detection problems
7.8.1 No seafloor on the screen
The system is running, transmitters are switched on, but there is no echo on the screen repre-
senting the seafloor.
One reason for that might be that the range and / or the range start have been set improp-
erly. Modify the range settings. Choose at first a longer range to find the seafloor and de-
crease the range then to the interesting length. Often it is better to look for the bottom signal
in the HF channel at first.
The gain might be too low. Modify the gain settings.
7.8.2 The echo signal is too small
If the received signal is too small, there are several possibilities:
Weak bottom material (mud) If there is a layer of mud or fluid mud, the LF bottom signal
is very weak. Check the amplifier settings and look at the HF channel, if you can get there
a better seafloor signal.
Survey areas with steep slopes If you are working in an area with steep slopes of the
bottom, you can have small signals from the sea bottom due to the narrow sound beam.
Use the AGC function in such areas while operating in a long range.
Dirty water (dredging activities) You are working in an area with very dirty water, for
instance during dredging activities. Such conditions cause a very bad signal to noise ratio
and you will get a high noise level at normal gain settings. To get a better signal to noise
ratio and therefore a better picture you should increase the stacking rate and you should
slow down the ship.
Dirty active area of the transducer You have clear water and flat bottom and you cannot
get the sea bottom signal with common gain settings. If the transducer is situated in water
for a longer time please check if the active area of the transducer is clean. The transducer
can be damaged if you work with it and there are for instance mussels, seaweeds, filth or
mud on the active area! You will have a high loss of the acoustical power.
Be careful during cleaning the active area of the transducer. Don’t use sharp tools. The
surface of the transducer must not be damaged! Furthermore, no oil or grease should be
on the active area of the transducers.
Transmitters might not work If you have checked all items above and you cannot get a
better signal then a transmitter board might be faulty. Switch off the system and wait for at
least 3 minutes. Check the fuses at the rear panel. If a fuse has blown, replace it. Make
sure you feel a slight 'click' when the fuse is pushed in to guarantee a good contact. Switch
on the system to see if there is a better result. If the fuse is blown again please contact
INNOMAR or an authorized person.
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