Assessing sounder performance: a guide to gathering objective and meaningful performance data

Transcription

1 Assessing sounder performance: a guide to gathering objective and meaningful performance data Introduction Although most Raymarine sounder owners and users prefer fully-automatic operation, and this is one of the Raymarine sounders great strengths, this mode is not suitable for comparing performance in different conditions or analysing performance-related problems. The procedure below allows the user to gather data that will allow Raymarine-trained Service Dealers and Raymarine technical support to assess system Noise levels (which severely impact performance) and relative signal strengths. Preparation 1. Insert a blank Compact Flash (CF) or MicroSD (μsd) card, as appropriate for your MFD model, into the MFD chart slot. 2. Using your MFD s sounder setup, set the following options: Control name Manual or Auto Setting for CP450C Chirp sounders Settings for all other Raymarine digital sounders Power Manual Gain Manual Colour Gain Manual 2-8: choose a Colour Gain level to 10 present a spread of colours as in Fig.2 and tell us what CG level was used when you send in the images TVG Manual Colour Threshold Go to Menu > Fishfinder Setup > Configure Preset Frequencies (G-series, Classic and Widescreen MFD ranges) or Menu > Frequency Settings (3 rd -generation a-series, c- Series and e-series MFDs) and configure dual-frequency display (e.g. 50 & 200kHz for DSMs or Low Chirp & High Chirp for CP450C systems) 4. Exit the menu and press the relevant softkey to go to P1 Single configured above (G-series, Classic and Widescreen MFD ranges) 5. Press the softkey Adjust P1 Single > Select View > A-scope > A-scope Mode = 2 (Gseries, Classic and Widescreen MFD ranges) or Menu > Display Mode > A-scope > Mode 2 (3 rd -generation a-series, c-series and e-series MFDs) 6. Go to Menu > Databar Setup > Configure > Add Data (G-series, Classic and Widescreen MFD ranges) or Menu > Presentation > Data Overlay Setup (3 rd -generation a-series, c-series and e-series MFDs) and make sure the following items are visible: - Vessel position - SOG (Speed over Ground)

2 Section 1: Assessing the boat s sounder noise level 1. Motor out of the marina into clear water well away from any other boat and either motor at idle or put the engines into Neutral. 2. Range the sounder display out to the maximum depth (1000m or deeper) 3. Concentrate on the A-scope view on the right of either of the two displayed frequencies. Adjust the Colour Gain control until the signal level at the bottom of the A-scope view just touches the left hand side of the A-scope area (coloured deep red if you re using one of the Classic palettes.) This is the noise level coming into the system, and we look at the very bottom of the A-scope on a long range to make sure that all of our own transmitted sound energy has dispersed and is not being measured, that we re only measuring background noise. Figure 1 shows what the A-scope should look like. 4. With the Colour Gain level visible, press and hold the DATA key for 10s, until the MFD beeps twice with about a 2s gap between (G-series, Classic and Widescreen MFD ranges) or press Power > Camera icon (3 rd -generation a-series, c-series and e-series MFDs) This will save a screenshot onto the inserted memory card. It is the level of the Colour Gain control under these conditions that provides the signal level measurement to us. A high Colour Gain level means a low-noise (good) system, a low Colour Gain level means a high level of noise. 5. Repeat with the second frequency Figure 1: correct Colour Gain level to measure background noise coming into the sounder. Note that the highest signal peaks (red) are just touching the left hand side of the A-scope column.

3 Section 2: Assessing the strength of signal returns (bottom) 1. Motor out into the depth of water at which you have been having problems. It s ok to switch back to Auto settings to do this, as long as you go back to the above Manual settings before continuing. 2. Range the sounder so that the seabed is shown about two-thirds of the way down the sounder screen. Leave on Manual Range. 3. Adjust the Colour Gain control until the bottom return signal is just touching the LHS of the A-scope, as above. 4. Stop the boat. Put the engines into Neutral 5. Press and hold DATA (G-series, Classic and Widescreen MFD ranges) or Power > Camera icon (3 rd -generation a-series, c-series and e-series MFDs) to save a screenshot to the memory card as above. 6. Put the engines into gear and re-do Step 5 at idle speed (dead slow). 7. Accelerate and redo Step 5 at 5 knot intervals until you reach the vessel s maximum speed. 8. the screenshots to aus.support@raymarine.com with the following information: - A description of what you see as the problem with the images in question - Noise level measurements (Colour Gain levels) for each frequency tested - Sounder model (DSM30, DSM300, DSM400, CP450C etc.) - Transducer model (e.g. B744V, R299, B265LM) - Transducer installation location (e.g. inboard of port engine, transom stbd side) - Boat make and model - Testing location (e.g. 20nm of ESE Port Stephens) - Your name and contact details

4 Examples Figure 2: A DSM300 sounder system configured correctly to show useful sounder performance diagnostics. In this case we have a strong bottom return and low background noise level leading to very good contrast between the bottom return and the noise. Figure 3:An example of a sounder image which is NOT useful for diagnostics. Running the sounder in Auto Gain means that we cannot tell for sure whether the loss of bottom return was due to a high noise level or low signal level

5 Figure 4: Although the user is running in the wrong Colour Gain level, this screenshot is useful for diagnostics and clearly shows a low Noise level (pale blue-green background) but very broken and intermittent bottom return. This is a classic symptom of aeration under the transducer and usually means that the transducer needs to be moved to a better spot. This is not a sounder fault. Figure 5: Classic symptoms of noise from machinery or electronics on your own vessel. The herringbone pattern in the 38kHz sounder image and regular, repeating pattern in the A-scope view are very characteristic of an unwanted cyclical signal which is interfering with your sounder. This is not a sounder fault.

6 Figure 6: This screenshot is a good example of a boat-speed related Noise signal. You can see that the bottom return remains clear and continuous with no gaps (no air under the transducer) but you can see that in the section of the sounder image above the Range Shift softkey the background noise level (just above the bottom return) is far lower than in the rest of the sounder return. The boat was running at around 23 knots but for a short period slowed to idle, and this drop in speed was accompanied by a significant drop in background Noise level. The strong, continuous red band across the top of the sounder image is clutter from plankton, not part of the noise signal.

7 Other measurements You can use similar processes to measure the signal levels of other signals, for example: - Thermoclines, haloclines and other sound-reflecting zones in the water column (e.g. dense zooplankton blooms etc..) Adjust the Colour Gain level until the signal you want to measure touches the LHS of the A-scope and take a screenshot by holding DATA. Figure 2 shows an example of sound reflecting from a very dense swarm of zooplankton in the upper water layers, caused when warm but nutrient-poor current water is mixing with cold, nutrient-rich water moving offshore. Figure 7: a strong return in the upper water layers from a dense zooplankton bloom where offshore current eddies mix with coastal water. Below is a large bait school being attacked by pelagic predators.