Tuning the HydroLite-Plus Dual Frequency (DFX) Transducer

If you haven't connect the HydroLite-Plus to the Echologger control program before, please follow the steps in Trimble Access Setup.

1. Tuning should be completed prior to survey for each different body of water. If you are returning to the same location in the future write down the tuned parameters to easily apply them for the next time you visit the site.
2. Ideally tuning should be completed in the deepest part of the body of water that you will be surveying.
3. Open the DFX control program.
   
4. If both frequencies are to be used, ensure that the frequency option is set to duel mode.
5. The tuning is done by adjusting the Echosounder Parameters accessed by pressing detail settings (parameter definitions can be found at the end of this article). On the right is an echogram displaying the bottom tack of the system returns which gives a visual aid to better tune the system.
6. The default starting parameters advised by Seafloor are as follows: 
   

   	Low Frequency	High Frequency
   Range	100000	100000
   Interval	0.05
   Tx Length	50	50
   Tx Power	0
   Gain	+6	+6
   TVG spread coef.	15	10
   TVG absorb	.05	.05
   -20dB Attenuator	0	0
   Deadzone	800	800
   Threshold	10	10
   Offset	0	0
   Sound Speed	1500
   Median filter	OFF
   Average filter	OFF

    

7. Like the picture shown below, frequent spikes on the echogram typically indicate excessive noise within the system. Adjustments to parameters are necessary to filter out this noise and improve the system's capability to detect echoes from the water bottom.
   
8. The main parameters to adjust are:
   • Range, m - The distance between the transducer and the object. From the above example the range was set to 20m as the known maximum depth was 10m.
   • Deadzone, mm - The area surrounding the transducer where the sonar system is unable to detect echoes due to too much noise in the water or the sonar is still transitioning between sending out a signal and listening for echoes.
   • Gain, dB - The amplification of the received acoustic signal. By adjusting the gain you are adjusting the sensitivity of the transducer in receiving the sound wave echoes that it is emitting. By increasing the gain you are amplifying weak echoes, making them more detectable, while decreasing the gain reduces sensitivity to prevent saturation from strong echoes or background noise.
   • Altimeter Threshold, % - It refers to a predefined level set for the return signal strength from the water bottom. Think of the altimeter like a filter. It's a level set to determine which signals are strong enough to be considered reliable measurements. Setting this too high might mean missing weak echoes from softer bottoms, so it's about finding the right balance for accurate readings.
9. Continuously tweak and test these values until the echogram displays smoother and more sensible curves.
10. It is recommended to maintain default values for the remaining parameters.
11. After adjusting the parameters, the control program can be closed. The depth measurement will take place in Trimble Access.

Parameter Definitions

• Range, m - The distance between the transducer and the object.

• Interval, sec - Interval (repetition rate) between pulses in seconds. (From 0.1 to 3600 (1 Hour)) It refers to the time interval in seconds between successive transmissions of sonar pulses.

• Tx length, μsec - Set transmitted pulse length in microseconds (up to 100 μsec) It refers to the duration of time in microseconds (μsec) during which the sonar system emits a sound pulse into the water.

• Tx Power, dB - Transmit power of the sonar system, measured in decibels (dB). Transmit power determines the strength of the sound waves emitted by the sonar system.

• Gain, dB - It refers to the amplification of the received acoustic signal. Sonar systems emit sound waves into the water, which then bounce off objects and return as echoes. The gain setting on a sonar system adjusts the sensitivity of the receiver to these echoes.

• TVG spread coef - Spreading coefficient of transmission losses for time variable gain (TVG). TVG is a technique used to compensate for the decrease in received signal strength over time and distance.

• TVG absorb, dB/m - Coefficient of absorption used in the Time-Varying Gain (TVG) function of a sonar system, measured in decibels per meter (dB/m). It measures how quickly sound waves lose their strength as they travel through water.

• Attenuator, µs - It adjusts how quickly the system compensates for attenuation. A shorter duration means the system adjusts more quickly to changes in signal strength, while a longer duration means the adjustment occurs more gradually.

• Deadzone, mm - Area surrounding the transducer where the solar system is unable to detect echoes due to too much noise in the water or device is still transitioning between sending out a signal and listening for echoes. The deadzone value can be increased to block any unwanted surface noise that may be affecting the true bottom surface return.

• Offset, mm - Vertically offset the position of the device in millimetres.

• Altimeter threshold, % - Altimeter threshold percentage of full scale (return sensitivity) It refers to a predefined level set for the return signal strength from the water bottom. Think of the altimeter threshold in sonar like a filter. It's a level set to determine which signals are strong enough to be considered reliable measurements of depth.

• Sound Speed, m/s - Speed of sound in water.

• Output Mode - Select ‘Hydrolite DFX’ for HydroLite-Plus Dual Frequency (DFX).

MORE INFORMATION

For additional information or assistance, contact 1800 800 874 or email support@upgsolutions.com