Echo Sounder Flashcards
What’s the equation of the echo sounder?
RANGE = speed x time / 2.
Speed is known as 1500m/s.
Echo sounds record depths from?
2m to 400m
When setting up a echo sounder, what 4 things are you going to consider.
Alarms
Gain (sensitivity)
Discriminator
Datum
Why do you set up alarms on echo sounder when setting up?
Set alarms that are preset to warn of depths less then expected.
Why set up the gain when setting up the echo sounder?
- It controls the receiver sensitivity.
- Must be set correctly for accurate results.
Why set up the discriminator?
- Helps distinguish bottom returns from noise and fish etc.
- Shortens pulse length.
Why set up the datum?
- Echo sounder a allow offset correction
- therefore sounder shows DBK for safety.
Name 3 echo sounder errors
- Aeration due to air bubbles - serverly effect the depth sounder
- propergation error - speed of sound changes with temp
- Noise error - possible transmisions close to the transducer
Name some false echoes
- -Multiple echos (may bounce number of times between sea bed and surface/hull.
- Cone effect
- Side echoes
- Fish shoals
- Fresh water springs
- Kelp
- Turbulence from other ships wash.
List the steps to set up the echo sounder
- check the depth
- switch on and select suitable range scale
- adujust gain for optimum picture
- verify depth being displayed
- set shallow water alarms
- check printer
what are the dual frequencys for an echo sounder
200 KHZ good for shallow water = shorter pulse length
50 KHZ good for deepwater = longer pulse length
where is the transducer normally located
at the bottom of the ships hull and along the centre line of the vessel
outline the echo ranging principle
- A signal is transmitted
- The singal hits and obstruction, sending an echo back
- The time dfifference between sedning and receiving is meassured
- The range of the obstruction can be found by D = S x T / 2
S = 1500 m/s
