Doppler Log and Emlog Quiz

What is the primary principle behind the Doppler log?

• Reflection of ultrasonic waves

• Change in frequency of sound waves due to motion

• Measurement of time delay between echoes

• Variation in pressure with depth

What frequency range is typically used in Doppler logs for underwater applications?

• 20-30 Hz

• 200-600 Hz

• 20-30 kHz

• 200-600 kHz

Which parameter does the Doppler log directly measure?

• Absolute speed

• Relative speed to water or ground

• Wind speed

• Water current speed

In a Doppler log system, the term 'transducer' refers to the device that:

• Measures pressure

• Converts electrical signals to sound waves and vice versa

• Measures water temperature

• Calculates the vessel's heading

A Doppler log measures speed over the ground by sending signals in which direction(s)?

• Forward

• Downward

• Aft

• Forward and aft

What happens to the frequency of the signal when the vessel is moving toward the signal source?

• It increases

• It decreases

• It remains constant

• It fluctuates randomly

Which physical principle does a Doppler log utilize to calculate speed?

• Pascal's Law

• Bernoulli's Principle

• Doppler Effect

• Snell's Law

Which part of the Doppler log system emits the ultrasonic signals?

• Receiver

• Sensor

• Oscillator

• Transducer

What is a key limitation of a Doppler log when measuring speed over ground in shallow water?

• Reduced signal clarity

• Signal interference

• Signal scattering due to the seabed

• Increased drag on the vessel

In a Doppler log, how does the angle of signal transmission affect accuracy?

• It does not affect accuracy

• Smaller angles increase accuracy

• Larger angles increase accuracy

• It only affects accuracy in shallow waters