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Questions and Answers
What is the primary function of the transducer in an echo sounder?
What is the primary function of the transducer in an echo sounder?
- To amplify the received signal
- To convert electric pulses into sound waves (correct)
- To display the depth information
- To generate electric pulses
Depth measurement in an echo sounder is calculated using the total distance travelled by the sound pulse.
Depth measurement in an echo sounder is calculated using the total distance travelled by the sound pulse.
False (B)
What speed is associated with sound waves in seawater?
What speed is associated with sound waves in seawater?
1500 m/s
The control unit in an echo sounder is responsible for generating electric ______ and measuring the time.
The control unit in an echo sounder is responsible for generating electric ______ and measuring the time.
Match the following components of an echo sounder with their functions:
Match the following components of an echo sounder with their functions:
What range of frequencies do echo sounders typically use for sound waves?
What range of frequencies do echo sounders typically use for sound waves?
Where is the transducer typically located on a ship?
Where is the transducer typically located on a ship?
Digital echo sounders provide a paper recording of depth information.
Digital echo sounders provide a paper recording of depth information.
Which control is responsible for adjusting the range scale and clutter level according to depth?
Which control is responsible for adjusting the range scale and clutter level according to depth?
The Time Variable Gain (TVG) control is used to increase sensitivity at greater depths.
The Time Variable Gain (TVG) control is used to increase sensitivity at greater depths.
What might happen if the Gain control is set too low?
What might happen if the Gain control is set too low?
The control that allows the navigator to set a warning for shallow areas is known as the ______.
The control that allows the navigator to set a warning for shallow areas is known as the ______.
What is the maximum depth that Time Variable Gain (TVG) can work on echo sounders operating at 200 kHz?
What is the maximum depth that Time Variable Gain (TVG) can work on echo sounders operating at 200 kHz?
Match the control with its function:
Match the control with its function:
Transducer placement has no impact on the accuracy of depth measurements.
Transducer placement has no impact on the accuracy of depth measurements.
What impacts the location of the bow wave on a ship?
What impacts the location of the bow wave on a ship?
What should be considered when installing a transducer?
What should be considered when installing a transducer?
An increase in temperature, salinity, or pressure results in a decrease in the speed of sound through water.
An increase in temperature, salinity, or pressure results in a decrease in the speed of sound through water.
What is the assumed speed of sound waves through water for echo sounder calculations?
What is the assumed speed of sound waves through water for echo sounder calculations?
The indicated depth by an echo sounder may be about ___ less than the actual depth in the Red Sea.
The indicated depth by an echo sounder may be about ___ less than the actual depth in the Red Sea.
Which of the following is an example of an instrument inaccuracy related to echo sounders?
Which of the following is an example of an instrument inaccuracy related to echo sounders?
False echoes are a type of error that can affect the navigational accuracy of an echo sounder.
False echoes are a type of error that can affect the navigational accuracy of an echo sounder.
What is one method navigators must use to verify echo sounder readings when errors occur?
What is one method navigators must use to verify echo sounder readings when errors occur?
Match the errors related to echo sounders with their descriptions:
Match the errors related to echo sounders with their descriptions:
What may cause unknown errors in the depth measured in seawater?
What may cause unknown errors in the depth measured in seawater?
Sound waves will not be affected if the seabed is horizontal.
Sound waves will not be affected if the seabed is horizontal.
What is a double echo?
What is a double echo?
The phenomenon where seawater creates bubbles that distort sound waves is known as __________.
The phenomenon where seawater creates bubbles that distort sound waves is known as __________.
What can navigators do to eliminate the impact of double echoes?
What can navigators do to eliminate the impact of double echoes?
Match the following types of echoes with their descriptions:
Match the following types of echoes with their descriptions:
Turbulence and aeration can enhance an echo sounder's capability of depth measurement.
Turbulence and aeration can enhance an echo sounder's capability of depth measurement.
What is the Pythagoras Error in echo sounders?
What is the Pythagoras Error in echo sounders?
Study Notes
Echo Sounder Operation
- An echo sounder sends sound waves to the seabed and measures the time it takes for the sound waves to return.
- Transducers convert electric pulses into sound waves and vice versa.
- The speed of sound in seawater is used to calculate depth: Depth = Speed of sound waves x time / 2
- Display unites show the depth on a paper or digital display.
- Some echo sounders use different colors on the display to indicate seabed composition.
Echo Sounder Controls
- Auto: Automatically adjusts range and clutter level based on depth.
- Gain: Adjusts the sensitivity of the instrument.
- TVG (Time Variable Gain): Similar to STC in radar. Reduces surface noise by compensating for sound wave attenuation.
- Echo Offset: Adjusts weak or strong echoes.
- Depth Alarm: Warns the navigator when the ship enters shallow water.
- Draught: Allows the navigator to input the ship's current draught for accurate depth measurements.
- Dimmer Control: Controls the screen brightness and keypad illumination.
Transducer Location
- The transducer should be located in a place with minimal aeration and interference from engine or propeller vibration.
- The bow of the ship is prone to aeration and should be avoided for transducer placement.
Echo Sounder Errors
Instrument Inaccuracies
- Speed Error: The speed of sound in seawater varies with temperature, salinity, and pressure.
- Second Transmission Error: In deep water, the echo sounder may receive a delayed echo from the previous transmission,resulting in an inaccurate depth reading.
- Refraction and Reflection of Sound Waves: Variations in temperature and salinity can cause sound waves to reflect and refract, leading to inaccurate depth readings.
- Reflection from Sloping Seabed: If the seabed is not horizontal, sound waves may be reflected unevenly, leading to inaccurate or absent depth readings.
False Echoes
- Double Echo: Sound waves reflecting off the ship's hull and then the seabed create a double echo on the display.
- Multiple Echoes: Similar to a double echo, but with multiple reflections between the hull and seabed.
- Echoes from other objects in seawater: Plankton, fish, or seaweed can produce echoes that the echo sounder may interpret as the seabed.
- Turbulence and Aeration: Air bubbles caused by turbulence can disrupt echo signals and lead to false readings.
- Pythagoras Error: When the transducer and receiver are a distance apart, the sound wave travels a longer distance than the direct path to the seabed, leading to an inaccurate measurement. Modern echo sounders are designed to account for this error.
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Description
This quiz explores the principles and controls of echo sounders used in nautical applications. It covers the operation of echo sounders, including how sound waves measure seabed depth and the various controls that adjust the instrument's performance. Test your knowledge of the key concepts involved in using echo sounders effectively.
